CN115764880A - Converters, power systems and resonance detection methods - Google Patents

Abstract

The application provides a converter, a power system and a resonance detection method. The converter includes a control module, an inverter module, a filter inductor and a filter capacitor. The input end of the inverter module is used to connect to a DC power supply, the output end of the inverter module is connected to one end of the filter inductor, and the other end of the filter inductor is connected to the filter capacitor. One end of the converter is connected and the connection point is used as the output terminal of the converter to connect to the AC grid; the control module is used to obtain the effective value of the output current of the converter based on the multiple output current sampling values of the converter in one power frequency cycle, and convert The multiple output current sampling values of the converter are obtained based on the multiple sampling values of the inductor current of the filter inductor and the multiple sampling values of the capacitor current of the filter capacitor in the power frequency period; the control module is also used for output current of the converter When the effective value is greater than the resonance threshold, the inverter module is controlled to suppress resonance. By implementing the application, the resonance can be detected quickly and timely, and the safety and stability of the system can be improved.

Description

Converters, power systems and resonance detection methods

technical field

The present application relates to the technical field of power electronics, in particular to a converter, a power system and a resonance detection method.

Background technique

With the continuous development of energy demand and power electronics technology, the grid-connected capacity of photovoltaic/energy storage power stations continues to increase, and it is becoming more and more common for multiple converters in the power system to be connected in parallel to the public grid. In the power system, the DC power generated by the energy storage battery or the photovoltaic power generation unit can be converted by the DC converter and then output to the converter. , for public grid use. The power system includes one or more grid-connected converters. Due to the interaction coupling phenomenon between the converter and the grid, and between multiple grid-connected converters, the input port of the converter and the converter Positions such as grid-connected ports are likely to cause resonance.

When resonance occurs in the power system, it will lead to the collapse of the power system and affect the safe and stable operation of the power system. Therefore, how to detect the resonance in the power system quickly and in real time and take measures to suppress the resonance has become an urgent technical problem to be solved.

Contents of the invention

The application provides a converter, a power system and a resonance detection method, which can detect resonance quickly and in time, and improve system safety and stability.

In the first aspect, the present application provides a converter, the converter includes: a control module, an inverter module, a filter inductor and a filter capacitor, the input terminal of the inverter module is used to connect to a DC power supply, and the output One end of the filter inductor is connected to one end of the filter inductor, and the other end of the filter inductor is connected to one end of the filter capacitor, and the connection point is used as the output end of the converter to connect to the AC grid; the control module is used for multiple outputs of the converter based on a power frequency cycle The current sampling value is used to obtain the effective value of the output current of the converter, and the multiple output current sampling values of the converter are obtained based on multiple sampling values of the inductor current of the filter inductor and multiple sampling values of the capacitor current of the filter capacitor in the power frequency cycle ; The control module is also used to control the inverter module to suppress the resonance when the effective value of the output current of the converter is greater than the resonance threshold. Wherein, the effective value of the output current of the converter can be used to represent the magnitude of the output current of the converter, which is beneficial to reflect the resonance condition in the system where the converter is located. The above-mentioned resonance threshold can be specifically set based on the type of power grid, equipment requirements, etc., and is not limited here.

In this application, the control module in the converter obtains the effective value of the output current of the converter by obtaining a plurality of sampling values of the output current of the converter within one power frequency cycle. Wherein, the sampling value of the output current of the converter can be obtained based on the sampling information of the existing filter inductor and filter capacitor, and the process of calculating the effective value of the output current of the converter is simple and efficient, without adding additional detection lines and calculations. After obtaining the effective value of the output current, determine whether resonance occurs based on the relationship between the effective value of the output current and the resonance threshold. Since the effective value of the output current can reflect the amplitude of each harmonic in the output current of the converter, it can be It can intuitively reflect whether resonance exists, so adopting this method is conducive to quickly identifying resonance and improving system safety and reliability.

In a feasible implementation manner, one of the multiple output current sampling values of the converter is obtained based on a difference between one inductor current sampling value and one capacitor current sampling value. In this application, the sampling information of the existing filter inductor and filter capacitor is directly used to obtain the sampled value of the output current of the converter, and then the effective value of the output current is obtained, which is simple and efficient, can improve the speed of resonance detection, and save circuit costs.

In a feasible implementation manner, the above-mentioned converter further includes a DC capacitor module, and the input terminal of the inverter module is connected to the DC power supply through the DC capacitor module; multiple sampled values within the converter to obtain the effective value of the input voltage of the converter; the control module is also used to control the inverter module to suppress resonance when the effective value of the input voltage of the converter is greater than the resonance threshold. It can be understood that the sampled value of the input voltage of the DC capacitor module is equal to the sampled value of the input voltage of the converter. In this application, the input voltage sampling value of the converter can be directly obtained by using the voltage sampling information of the existing DC capacitor module, and then the effective value of the input voltage of the converter can be obtained to detect resonance. This method is simple and efficient, and is conducive to improving Resonance detection speed.

In a feasible implementation manner, the above DC capacitor module includes a first capacitor and a second capacitor connected in series, and the first capacitor and the second capacitor connected in series are connected in parallel with the input terminal of the inverter module, and the first capacitor and the second capacitor The series connection point serves as the midpoint of the capacitor and is connected to the other end of the filter capacitor; the control module is also used to obtain the input voltage of the DC capacitor module based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor. Wherein, the first capacitor and the second capacitor are supporting capacitors, and the circuit topology of the inverter module in the converter can be a multi-level topology, for example, it can be a two-level topology, a midpoint clamped three-level topology, The flying capacitor type three-level topology and the like are not limited in this application. In this application, the input voltage sampling information of the existing first capacitor and the second capacitor is directly used to obtain the effective value of the input voltage of the converter to detect resonance. This method is simple and efficient, and is conducive to improving the resonance detection speed.

In a feasible implementation manner, the above-mentioned DC capacitor module includes a third capacitor connected in parallel with the input terminal of the inverter module; the control module is also used to obtain the input voltage of the third capacitor as the input voltage of the DC capacitor module. Wherein, the third capacitor is a supporting capacitor, and the circuit topology of the inverter module in the converter may be a two-level topology. In this application, the resonance is detected by directly using the input voltage sampling information of the existing third capacitor to obtain the effective value of the input voltage of the converter. This method is simple and efficient, and is conducive to improving the resonance detection speed.

In a feasible implementation manner, the plurality of sampled values of output current include N sampled values of output current, and the control module is configured to use the average value of the N sampled values of output current and the average value of the N sampled values of output current root mean square to obtain the effective value of the above output current, and the above N is greater than or equal to twice the switching frequency of the above inverter module. Wherein, one output current sampling value represents one output current sampling value. In this application, the output current effective value obtained based on the N output current sampling values can reflect the amplitude of each harmonic included in the output current of the converter, and the output current effective value is obtained based on these output current sampling values. It is beneficial to improve the effect and accuracy of resonance detection.

In a feasible implementation manner, the control module is further configured to control the inverter module to stop when the effective value of the output current or the effective value of the input voltage of the above-mentioned converter is greater than the resonance threshold and the duration is greater than or equal to the reference time length. Work. The above reference time length is equal to the resonance protection setting time of the converter, which can be set according to actual application scenarios. In this application, when the above-mentioned effective value is continuously greater than the above-mentioned resonance threshold and the duration exceeds the above-mentioned reference time, the control module directly controls the inverter module in the converter to stop working, which can prevent the negative impact of resonance on the power system is too big.

In the second aspect, the present application provides a converter, the converter includes: a control module, an inverter module and a DC capacitor module, the input end of the inverter module is connected to a DC power supply through the DC capacitor module, and the output of the inverter module The terminal is used to connect to the AC power grid; the control module is used to obtain the effective value of the input voltage of the converter based on the multiple input voltage sampling values of the converter in one power frequency cycle, and the multiple input voltage sampling values of the converter are based on Multiple capacitor current sampling values of the DC capacitor module in the power frequency period are obtained; the control module is also used to control the inverter module to suppress resonance when the effective value of the input voltage of the converter is greater than the resonance threshold. Wherein, the effective value of the input voltage of the converter can be used to represent the magnitude of the input voltage of the converter, which is beneficial to reflect the resonance condition in the system where the converter is located. The above-mentioned resonance threshold can be specifically set based on the type of power grid, equipment requirements, etc., and is not limited here.

In a feasible implementation manner, the above-mentioned DC capacitor module includes a first capacitor and a second capacitor connected in series, and the above-mentioned first capacitor and second capacitor connected in series are connected in parallel with the input terminal of the above-mentioned inverter module; the above-mentioned control module is also used for Based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor, the input voltage of the DC capacitor module is obtained.

In a feasible implementation manner, the above-mentioned DC capacitor module includes a third capacitor, and the above-mentioned third capacitor is connected in parallel with the input terminal of the above-mentioned inverter module; the above-mentioned control module is also used to obtain the input voltage of the above-mentioned third capacitor as the above-mentioned DC capacitor The input voltage of the module.

In this application, the control module in the converter obtains the effective value of the input voltage of the converter by obtaining a plurality of sampling values of the input voltage of the converter within one power frequency cycle. Among them, the sampling value of the input voltage of the converter can be obtained based on the sampling information of the existing DC capacitor module, and the process of calculating the effective value of the input voltage of the converter is simple and efficient, without adding additional detection lines and calculations. After obtaining the effective value of the input voltage, determine whether resonance occurs based on the relationship between the effective value of the input voltage and the resonance threshold. Since the effective value of the input voltage can reflect the amplitude of each harmonic in the input voltage of the converter, it can be It can intuitively reflect whether resonance exists, so adopting this method is conducive to quickly identifying resonance and improving system safety and reliability.

In a third aspect, the present application provides a power system, the power system includes at least two converters as described in any one of the first aspect and the first aspect, the output ends of the at least two converters After parallel connection, connect the above-mentioned AC grid through the above-mentioned transformer; the control module in any one of the above-mentioned at least two converters is used to obtain the effective value of the output current of the above-mentioned converter, and when the above-mentioned effective value of the output current is greater than the above-mentioned When the resonance threshold is reached, the inverter module in the above-mentioned converter is controlled to suppress resonance, and the transformer is used to step-up transform the output voltage of any one of the above-mentioned at least two converters and output it to the above-mentioned AC power grid. Wherein, the output terminals of at least two converters in the power system are connected in parallel to the same transformer, which also corresponds to the AC side paralleling scenario of multiple converters. In this application, in the scenario where multiple converters are paralleled on the AC side, since AC side resonance is likely to occur, the control module in each converter can detect whether the resonance exists based on the effective value of the output current of the inverter , and take steps to suppress the resonance when it is detected. In this way, the resonance occurring on the AC port side of the converter can be detected quickly and in real time, the speed and effect of resonance detection can be improved, and it is beneficial to eliminate the resonance in time when the resonance occurs, thereby improving the stability and reliability of the power system.

In a fourth aspect, the present application provides a power system, the power system includes at least two converters, a DC bus, and one or more DC converters as described in any one of the first aspect and any one of the implementation manners of the first aspect, The input ends of each DC converter are connected to the above-mentioned DC power supply, the output ends of each DC converter are connected in parallel to the above-mentioned DC bus, and the input ends of at least two of the above-mentioned converters are connected in parallel to the above-mentioned DC bus; in the above-mentioned at least two converters The control module in any one of the converters is used to obtain the effective value of the input voltage of the inverter module in the above-mentioned converter, and when the above-mentioned effective value of the input voltage is greater than the above-mentioned resonance threshold, control the inverter in the above-mentioned converter The module suppresses resonance; the above-mentioned DC converter is used for performing DC conversion on the DC power provided by the above-mentioned DC power supply and then outputting it to the above-mentioned DC bus. Wherein, the input ends of at least two converters in the power system are connected in parallel to the DC bus, which also corresponds to the DC side paralleling scenario of multiple converters. In this application, in the scenario where multiple converters are paralleled on the DC side, since DC side resonance is prone to occur, the control module in each converter can detect whether the resonance exists based on the effective value of the input voltage of the inverter , and take steps to suppress the resonance when it is detected. In this way, the resonance occurring on the DC port side of the converter can be detected quickly and in real time, the speed and effect of resonance detection can be improved, and it is beneficial to eliminate the resonance in time when the resonance occurs, thereby improving the stability and reliability of the power system.

In the fifth aspect, the present application provides a resonance detection method, which is applied to the control module in the converter. The converter also includes an inverter module, a filter inductor and a filter capacitor. The input terminal of the above inverter module is used for When connecting a DC power supply, the output end of the inverter module is connected to one end of the filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor, and the connection point is used as the output end of the converter to connect to the AC grid; the method includes : Obtain the effective value of the output current of the above-mentioned converter based on a plurality of output current sampling values of the above-mentioned converter in one power frequency period, and the multiple output current sampling values of the above-mentioned converter are based on the above-mentioned A plurality of sampled values of the inductor current of the filter inductor and a plurality of sampled values of the capacitor current of the filter capacitor are obtained; when the effective value of the output current of the above-mentioned converter is greater than the resonance threshold, the above-mentioned inverter module is controlled to suppress resonance.

In a feasible implementation manner, one output current sample value among the multiple output current sample values of the converter is obtained based on a difference between one inductor current sample value and one capacitor current sample value.

In a feasible implementation manner, the above-mentioned converter further includes a DC capacitor module, the input terminal of the above-mentioned inverter module is connected to the above-mentioned DC power supply through the above-mentioned DC capacitor module; the above-mentioned method also includes: based on the input voltage of the above-mentioned DC capacitor module at A plurality of sampling values in one power frequency cycle is used to obtain an effective value of the input voltage of the converter; when the effective value of the input voltage of the converter is greater than the resonance threshold, the inverter module is controlled to suppress resonance.

In a feasible implementation manner, the above-mentioned DC capacitor module includes a first capacitor and a second capacitor connected in series, and the first capacitor and the second capacitor connected in series are connected in parallel with the input terminal of the inverter module, and the first capacitor and the above-mentioned The series connection point of the second capacitor is connected to the other end of the filter capacitor as the capacitor midpoint; the method further includes: based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor, the DC capacitor module is obtained. Input voltage.

In a feasible implementation manner, the above-mentioned DC capacitor module includes a third capacitor, and the above-mentioned third capacitor is connected in parallel with the input terminal of the above-mentioned inverter module; the above method also includes: obtaining the input voltage of the above-mentioned third capacitor as the voltage of the above-mentioned DC capacitor module. the input voltage.

In a feasible implementation manner, the above-mentioned multiple output current sampling values include N output current sampling values, and the above-mentioned multiple output current sampling values of the above-mentioned converter in one power frequency cycle are used to obtain the The effective value of the output current includes: obtaining the effective value of the output current based on the average value of the above-mentioned N output current sampling values and the root mean square of the above-mentioned N output current sampling values, and the above-mentioned N is greater than or equal to the switch of the above-mentioned inverter module twice the frequency.

In a feasible implementation manner, the method further includes: controlling the inverter module to stop working when the duration of the effective value of the output current or the effective value of the input current is greater than the resonance threshold is greater than or equal to a reference duration.

In this application, the control module in the converter can obtain multiple sampled values of the output current of the converter in one power frequency cycle based on the sampling information of the filter inductor and filter capacitor, and obtain the effective value of the output current of the converter . The control module can also obtain a plurality of sampled values of the input voltage of the converter based on the sampling information of the DC capacitor module, and obtain an effective value of the input voltage of the converter. Among them, the effective value of the output current and the effective value of the input voltage of the converter can be obtained based on the existing sampling information, and the process of calculating the effective value is simple and efficient, without adding additional detection lines and calculations. After obtaining the above effective value, determine whether resonance occurs based on the relationship between the effective value and the resonance threshold, because the effective value of the output current and the effective value of the input voltage can visually reflect whether there are Resonance, so using this method is conducive to quickly identifying resonance and improving system safety and reliability.

Description of drawings

FIG. 1 is a schematic diagram of an application scenario of a converter provided by the present application;

Fig. 2 is a schematic structural diagram of a converter provided by the present application;

Fig. 3 is another structural schematic diagram of the converter provided by the present application;

Fig. 4 is another structural schematic diagram of the converter provided by the present application;

Fig. 5 is another structural schematic diagram of the converter provided by the present application;

Fig. 6 is another structural schematic diagram of the converter provided by the present application;

Fig. 7 is a schematic structural diagram of the power system provided by the present application;

Fig. 8 is another structural schematic diagram of the power system provided by the present application;

Fig. 9 is another structural schematic diagram of the power system provided by the present application;

FIG. 10 is a schematic flowchart of a resonance detection method provided in the present application.

Detailed ways

A converter is a commonly used energy conversion unit in the field of power electronics, which can be used to change the voltage, frequency, phase number and other power or characteristics of the power supply. In new energy power generation systems, the DC power provided by power sources such as energy storage systems or photovoltaic power generation devices can be converted into AC power by converters and then output to the grid or supply power to loads. That is to say, the converter mentioned in this application has the function of converting direct current into alternating current. This converter can refer to an inverter that can convert DC power to AC power, or can refer to a power storage converter (Power Conversion System, PCS) that can convert DC power to AC power and convert AC power to DC power. Applications are not restricted. Please refer to FIG. 1 . FIG. 1 is a schematic diagram of an application scenario of the converter provided in this application. The converter can be applied in a power generation system (also called a power system). The input end of the converter is connected to the output end of the DC power supply, and the output end of the converter can be connected through a transformer (not shown in Figure 1). AC power grid, the converter can convert the DC power input by the DC power supply into AC power and send it to the AC power grid. In addition, the input end of the converter can also be connected to the output end of the DC power supply (not shown in FIG. 1 ) through a DC converter, and the DC converter is used for performing DC conversion on the DC power provided by the DC power supply and outputting it to the converter. In the application scenario shown in FIG. 1 , the DC power supply may include an energy storage system and/or a photovoltaic power generation device. In FIG. 1 , the DC power supply includes an energy storage system as an example. This application scenario may also include a DC converter (not shown in Figure 1), the input end of the DC converter is connected to the output end of the DC power supply, the output end of the DC converter is connected to the input end of the converter, and the DC The converter can be used to convert the DC power provided by the energy storage system and/or photovoltaic power generation device into DC power and output it to the converter. The converter is used to convert the DC power provided by the DC power supply into AC power, which can be supplied to the AC power grid to supply power for loads such as communication base stations or household equipment. It is understandable that when the DC power supply includes an energy storage system, the converter can be an energy storage converter to realize bidirectional conversion of electric energy, that is, the DC power provided by the energy storage system can be converted into AC power and sent to the AC power grid Or use it for loads; it can also rectify the alternating current of the grid into direct current to charge the energy storage system. The application scenario shown in FIG. 1 is a grid-connected scenario of a single converter. In other application scenarios, the power system may include multiple grid-connected converters. Multiple converters connected in parallel to the grid can increase the grid-connected capacity of new energy power generation systems such as photovoltaic/energy storage power stations to meet the increasing energy demand. In a power system composed of one converter or multiple converters connected to the grid, due to the interactive coupling phenomenon between the converter and the grid or between multiple grid-connected converters, the input port of the converter And the grid-connected output port is very easy to cause resonance. The existence of resonance can easily lead to system collapse and affect the safe and stable operation of the power system.

The control module in the converter provided by this application obtains multiple output current samples of the converter based on multiple sampled values of the inductor current of the filter inductor and multiple sampled values of the capacitor current of the filter capacitor within a power frequency cycle value, and based on the plurality of output current sampling values to obtain the effective value of the output current of the converter, based on the relationship between the effective value of the output current and the resonance threshold to determine whether resonance occurs in the power system where the converter is located. Since the sampling information of the filter inductor and filter capacitor is the existing sampling information, the effective value of the output current can directly reflect the resonance situation in the system, and the acquisition method of the effective value of the output current is simple and efficient, so it can be detected quickly and timely Resonance, improve system reliability and safety.

Referring to FIG. 2 , FIG. 2 is a schematic structural diagram of a converter provided in the present application. As shown in FIG. 2 , the converter may include a control module, an inverter module, a filter inductor (ie, inductor L ₁ in FIG. 2 ) and a filter capacitor (ie, capacitor C _f in FIG. 2 ). Wherein, the input end of the inverter module can be used as the input end of the converter to connect with the DC power supply, the output end of the inverter module is connected to one end of the filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor and the connection point As the output of the converter, it is connected to the AC grid. In this application, the inverter module in the converter can be used to invert the DC power provided by the DC power supply into AC power, and the AC power can be output to the AC power grid after being filtered by a filter capacitor and a filter inductor. Here, the converter may be an energy storage converter or an inverter, which may be specifically determined according to an actual application scenario. Optionally, in the converter shown in Figure 2, the end of the filter inductor connected to the filter capacitor can also be connected to another inductor (not shown in Figure 2) to improve the stability of the output current of the inverter module sex. The converter shown in Figure 2 can be a three-phase converter, which can include a three-phase filter circuit composed of three filter inductors and three filter capacitors, and the two ends of each filter inductor are respectively connected to the inverter One end of the module and a filter capacitor, the connection point of the filter inductor and the filter capacitor are used as the output end of the converter, and the other ends of the three filter capacitors are connected in parallel. Optionally, the converter provided in this application can also be a single-phase converter, which includes a filter circuit composed of a filter inductor and a filter capacitor. At this time, the inverter module in the converter can It includes two bridge arms, one end of the filter inductor and one end of the filter capacitor are respectively connected to the midpoint of the two bridge arms, the other end of the filter inductor is connected to the other end of the filter capacitor and the connection point is used as the output end of the converter. The topology of the inverter module in the above-mentioned converter may be a multi-level topology, which may be specifically set according to actual application scenarios, which is not limited in this application.

In some feasible implementation manners, the control module in the above-mentioned converter can obtain the effective value of the output current of the converter based on a plurality of sampled values of the output current of the converter within one power frequency cycle. In this application, the effective value of the output current of the converter is an effective value of alternating current, and the meaning of the effective value of alternating current or alternating voltage is: the magnitude of the work done by the alternating current/ac voltage in one cycle is equal to the specific direct current / DC voltage (equal to the effective value of the AC current) to do work. That is to say, from the effect of alternating current or alternating voltage, the "effective value" can be used to represent the magnitude of the alternating current. In this application, the effective value of the output current of the converter can be used to represent the magnitude of the output current. Understandably, when there is resonance in the power system where the converter is located, the resonance may occur at the output port side of the converter. Therefore, the control module in the converter can determine the magnitude of the output current by detecting the effective value of the output current of the converter, so as to determine whether resonance occurs. Further, after the control module in the converter obtains the effective value of the output current of the converter, when the effective value of the output current is greater than the resonance threshold, it is determined that resonance exists in the power system. The resonance threshold can be specifically set based on the grid type, device type, etc., and no limitation is set here. Among them, the above-mentioned multiple output current sampling values of the converter in one power frequency cycle can be based on the multiple inductor current sampling values of the filter inductor in the converter in the power frequency cycle and the filter capacitance in the power frequency cycle Multiple capacitor current sampling values are obtained. Specifically, one output current sample value among the plurality of output current sample values is obtained based on the difference between one inductor current sample value and one capacitor current sample value. That is to say, in a power frequency cycle, at each sampling moment, a sampled value i1 of the inductor current of the filter inductor and a sampled value i2 of the capacitive current of the filter capacitor are obtained, and based on the difference between i1 and i2 obtained at this moment, the variable An output current sampling value of the converter at this moment. In this way, multiple sampling values of the output current of the converter can be obtained based on multiple samplings of the filter inductor and the filter capacitor. Afterwards, based on a plurality of sampled values of the output current of the converter, an effective value of the output current of the converter can be obtained. Understandably, the sampled value of the inductor current of the filter inductor and the sampled value of the capacitive current of the filter capacitor belong to the sampled information that needs to be obtained when the converter works normally, that is, the sampled information is the existing sampled information. Therefore, this In the embodiment of the application, there is no need to add an additional output current sampling line, and the effective value of the output current of the converter can be obtained directly by using the sampling information of the existing filter inductor and filter capacitor to detect resonance. This method is simple and efficient, and can improve resonance detection. speed and save circuit cost.

In some feasible implementation manners, the plurality of output current sampling values of the above-mentioned converter may include N output current sampling values, wherein N may take a value greater than or equal to twice the switching frequency of the inverter module. Understandably, since the N sampled values of the output current are obtained based on multiple sampled values of the inductor current and multiple sampled values of the capacitor current within one power frequency cycle, the N sampled values of the output current can be used to restore the variable The signal waveform of the output current of the converter. Since the effective value of the output current obtained based on the N output current sampling values can reflect the amplitude of each harmonic included in the output current of the converter, the output current of the converter is obtained based on these output current sampling values The effective value is used to detect resonance, which is beneficial to improve the resonance detection effect and accuracy of the converter. Specifically, the control module in the above converter can obtain the average value and the root mean square of the N output current sample values based on the above N output current sample values. Then, based on the average value and the root mean square of the N output current sampling values, the effective value of the output current of the converter is obtained. In the following formula (1), the output current of the converter is i, and the control module can obtain the output current of the converter based on the N output current sampling values i ₁ , ..., i _N of the converter and formula (1) Valid values for i _rms . Understandably, when it is necessary to calculate the effective value of other electrical parameters of the converter (such as the effective value of the output voltage, the effective value of the input current or the effective value of the input voltage, etc.), the output current i in the formula (1) can be replaced by the corresponding other electrical parameters.

Understandably, in the above formula (1), the root mean square of the N output current sampling values can represent the total effective value of the AC component and the DC component included in the output current, and the average value of the N output current sampling values can represent The DC component of the output current, and the difference between the two can represent the effective value of the AC component of the output current, that is, the effective value of the output current. It can be understood that the effective value of the output current can reflect the magnitude of each harmonic included in the AC component of the output current, so whether resonance occurs can be detected by comparing the effective value of the output current with the resonance threshold.

In some feasible implementation manners, the control module in the above-mentioned converter may also obtain the effective value of the output voltage of the converter based on a plurality of sampled values of the output voltage of the converter within one power frequency cycle. When the effective value of the output voltage is greater than the resonance threshold, it is determined that resonance occurs, and the inverter module is controlled to suppress the resonance. Wherein, the sampling value of the output voltage of the converter can be directly sampled. Using multiple sampled values of the output voltage of the converter and the above formula (1), the effective value of the output voltage of the converter can be obtained. In this way, the calculation method of the effective value of the output voltage is simple and efficient, without adding additional calculation amount, which is conducive to improving the resonance detection speed and improving the safety and stability of the system.

In some feasible implementation manners, as shown in FIG. 3 , the above-mentioned converter may further include a DC capacitor module. The inverter module in the converter can be connected to the DC power supply through the DC capacitor module. The DC power supply is actually connected to the converter through the DC bus, and the DC bus is inductive. The DC capacitor module includes capacitors, so resonance may occur on the DC input side of the converter. Here, the control module in the converter can determine whether resonance occurs at the DC input side of the converter by detecting the effective value of the input voltage of the converter. Specifically, the control module can obtain the effective value of the input voltage of the converter based on a plurality of sampling values of the input voltage of the DC capacitor module within one power frequency cycle. For example, when the _N input voltage sampling values u ₁ , . When the effective value of the input voltage is greater than the resonance threshold, it is determined that resonance exists on the DC input side of the converter, and the control module of the converter can control the inverter module to suppress the resonance. Generally speaking, the input voltage sampling information of the DC capacitor module is also the control information that needs to be obtained when the converter works normally. Therefore, in the embodiment of the present application, the input voltage sampling information of the existing DC capacitor module can be directly used to obtain the current conversion information. The effective value of the input voltage of the device is used to detect resonance. This method is simple and efficient, and it is beneficial to improve the speed of resonance detection.

In some feasible implementation manners, the converter may include a control module, an inverter module and a DC capacitor module, the input terminal of the inverter module is connected to the DC power supply through the DC capacitor module, and the output terminal of the inverter module is used to connect to the AC power grid . The control module can be used to obtain the effective value of the input voltage of the converter based on multiple sampled values of the input voltage of the converter in a power frequency cycle, and the multiple sampled values of the input voltage of the converter are based on the DC current in the power frequency cycle Multiple capacitor current sampling values of the capacitor module are obtained. The control module can also be used to control the inverter module to suppress resonance when the effective value of the input voltage of the converter is greater than the resonance threshold. Wherein, the effective value of the input voltage can be obtained based on a plurality of sampled values of the input voltage and the above formula (1). The specific structure of the DC capacitor module will be introduced below.

It is understandable that resonance may occur at either the AC side port or the DC side port of the above-mentioned converter, so the control module in the converter can be obtained based on the current sampling information of the filter inductor and filter capacitor connected to the output terminal of the inverter module The effective value of the output current is used to detect whether resonance occurs at the AC side port of the converter based on the magnitude of the effective value of the output current. On the other hand, the controller in the converter can also obtain the effective value of the input voltage based on the voltage sampling information of the DC capacitor module connected to the input terminal of the inverter module, and calculate the output voltage of the converter based on the effective value of the input voltage. Check whether resonance occurs at the DC side port. Optionally, the controller in the converter can obtain the effective value of the output current and the effective value of the input voltage of the converter, and simultaneously detect the AC side port and the DC side port of the converter based on the relationship between the two and the resonance threshold Whether resonance occurs.

In some feasible implementation manners, as shown in FIG. 4 , the above-mentioned DC capacitor module may include a first capacitor (like capacitor C ₁ in FIG. 4 ) and a second capacitor (like capacitor C ₂ in FIG. 4 ) connected in series, The first capacitor and the second capacitor connected in series are connected in parallel with the input end of the inverter module, and the series connection point of the first capacitor and the second capacitor is connected to the other end of the filter capacitor in the converter as a midpoint of the capacitor. Specifically, when the converter is a three-phase converter, the midpoint of the capacitor is connected to the parallel connection point of the three filter capacitors. Wherein, the first capacitor and the second capacitor are supporting capacitors, and the circuit topology of the inverter module in the converter can be a multi-level topology, for example, it can be a two-level topology, a midpoint clamped three-level topology, The flying capacitor type three-level topology and the like are not limited in this application. In the converter shown in FIG. 4 , the control module can obtain the input voltage of the DC capacitor module based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor. It can be understood that the input voltage sampling information of the first capacitor and the second capacitor can also be the control information that needs to be obtained when the converter works normally. Therefore, in the embodiment of the present application, the existing first capacitor and The input voltage sampling information of the second capacitor is used to obtain the effective value of the input voltage of the converter to detect resonance. This method is simple and efficient, and is conducive to improving the resonance detection speed.

In some feasible implementation manners, as shown in FIG. 5 , the above-mentioned DC capacitor module may include a third capacitor (capacitor C ₃ in FIG. 5 ), and the third capacitor is connected in parallel with the input terminal of the inverter module. Here, the third capacitor is a supporting capacitor, and the circuit topology of the inverter module in the converter may be a two-level topology. In the converter shown in FIG. 4 , the control module can obtain the input voltage of the third capacitor as the input voltage of the DC capacitor module. It can be understood that the input voltage sampling information of the third capacitor can also be the control information that needs to be obtained when the converter works normally. Therefore, in the embodiment of the present application, the existing input voltage sampling information of the third capacitor can be directly used Obtaining the effective value of the input voltage of the converter to detect the resonance is simple and efficient, and it is beneficial to improve the speed of resonance detection.

In some feasible implementation manners, as shown in FIG. 6 , the above-mentioned DC capacitor module may include a first capacitor (like capacitor C ₁ in FIG. 6 ) and a second capacitor (like capacitor C ₂ in FIG. 6 ) connected in series, A third capacitor (such as capacitor C ₃ in FIG. 6 ) may also be included. Wherein, the first capacitor and the second capacitor connected in series are connected in parallel with the input end of the inverter module, and the third capacitor is also connected in parallel with the input end of the inverter module. The series connection point of the first capacitor and the second capacitor is connected to the other end of the filter capacitor in the converter as the midpoint of the capacitor. Specifically, when the converter is a three-phase converter, the midpoint of the capacitor is connected to the parallel connection point of the three filter capacitors. Wherein, the first capacitor and the second capacitor are supporting capacitors, and the circuit topology of the inverter module in the converter can be a multi-level topology, for example, it can be a two-level topology, a midpoint clamped three-level topology, The flying capacitor type three-level topology and the like are not limited in this application. The third capacitor can function as voltage regulator and filter. In the converter shown in FIG. 6 , the control module can obtain the input voltage of the DC capacitor module based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor. Alternatively, the control module may obtain the input voltage of the third capacitor as the input voltage of the DC capacitor module. It can be understood that the input voltage sampling information of the first capacitor and the second capacitor and the input voltage sampling information of the third capacitor can also be the control information that needs to be obtained when the converter works normally. Therefore, in the embodiment of the present application, the Directly use the existing input voltage sampling information of the first capacitor and the second capacitor or the input voltage sampling information of the third capacitor to obtain the effective value of the input voltage of the converter to detect resonance. This method is simple and efficient, and is conducive to improving resonance detection. speed.

In some feasible implementation manners, the control module in the above-mentioned converter can obtain the effective value of the input current of the converter by obtaining a plurality of sampling values of the input current of the converter within one power frequency cycle. Since the input current of the converter can also be used as a commonly used control parameter, that is, the sampling value of the input current is also the sampling information required in the power system, so the process is simple and efficient without adding additional calculations, which is conducive to improving resonance Detection speed, improve system security and stability.

In some feasible implementations, when there is resonance in the power system and the resonance occurs on the input side or output side of the above-mentioned converter, the control module in the converter can suppress the resonance by implementing a control strategy, such as controlling the The inverter module in the converter reduces the output power (which may be called derating) or adjusts the switching frequency, etc. Wherein, adjusting the switching frequency may include increasing the PWM control frequency and decreasing the PWM control frequency, which is not limited here. Understandably, by derating or adjusting the switching frequency, the operating point of the power system can be shifted so that the system avoids the resonance frequency point, thereby suppressing resonance. Using this method to suppress resonance can improve system safety and stability. In addition, since the resonance suppression method is a software control method, the resonance suppression can be realized through the software control method, and no additional inductance can be added to reduce the resonance frequency, so that the volume and weight of the equipment can be reduced, which is beneficial to save costs.

In some feasible implementation manners, the control module in the above-mentioned converter is also used to control the current converter when the duration of the effective value of the output current or the effective value of the input voltage of the converter is greater than the resonance threshold is greater than or equal to the reference time length. The inverter module in the converter stops working. The above reference time length is equal to the resonance protection setting time of the converter, which can be set according to actual application scenarios, and is not limited in this application. It can be understood that when the effective value of the output current or the effective value of the input voltage of the above-mentioned converter is continuously greater than the above-mentioned resonance threshold, and the duration exceeds the above-mentioned reference time, it means that there is resonance in the power system and the resonance cannot be effectively suppressed. At this time, The control module can directly control the inverter module in the converter to stop working, that is, control the converter to shut down, so as to prevent the negative impact of resonance on the power system from being too large.

The process of detecting resonance and suppressing resonance of the converters has been introduced in detail above. The following describes how each converter detects resonance and suppresses resonance in the actual application scenario where multiple converters are connected in parallel and connected to the grid.

In some feasible implementation modes, please refer to Fig. 7, as shown in Fig. 7, the present application also provides a power system, which includes at least two converters (converter 1, ... in Fig. 7 ..., converter n, n is greater than or equal to 2), each converter can be any converter as shown in Figure 2-Figure 6 . The output terminals of the at least two converters are connected in parallel to the AC grid through the same transformer; that is, the output terminals of the at least two converters are connected in parallel to the same transformer, and the converters are applied to the power system, It can also be said that the converter is applied to the AC side paralleling scenario. Then, due to the interactive coupling between these converters and between the converters and the grid, resonance is likely to occur at the output port side of the at least two converters. In this scenario, the control module in any one of the at least two converters can obtain the effective value of the output current or the effective value of the output voltage of the converter, and the effective value of the output current or the effective value of the output voltage When the effective value of the output voltage is greater than the resonance threshold, the inverter module in the converter is controlled to suppress the resonance by reducing the output power or adjusting the switching frequency. Wherein, the process for the control module in each converter to obtain the effective value of the output current or the effective value of the output voltage of the converter can refer to the relevant description above, and will not be repeated here. The transformer in the power system can be used to boost the output voltage of any converter. When the converter is an energy storage converter, the transformer can also be used to convert the AC power provided by the AC grid and provide it to the energy storage converter. In the embodiment of the present application, in the scenario where multiple converters are paralleled on the AC side, since AC side resonance is likely to occur, the control module in each converter can detect whether the resonance is based on the effective value of the output current of the inverter. exist, and take steps to suppress the resonance when it is detected. In this way, the resonance occurring on the AC port side of the converter can be detected quickly and in real time, the speed and effect of resonance detection can be improved, and it is beneficial to eliminate the resonance in time when the resonance occurs, thereby improving the stability and reliability of the power system.

In some feasible implementation manners, please refer to FIG. 8 . As shown in FIG. 8 , the present application also provides a power system, which includes at least two converters (converter 1, ... in FIG. 8 ..., converter n, n is greater than or equal to 2), each converter can be any one of the converters shown in Figure 3-Figure 6 . The power system may also include a DC bus and one or more DC converters (such as DC converter 1, . . . , DC converter m in FIG. 8 , where m is greater than or equal to 1). Wherein, the input end of each DC converter is connected to a DC power supply. As shown in FIG. 8 , one DC converter can be connected to one DC power source, and the present application does not limit the number of DC power sources included in the power system. The output terminals of each DC converter are connected in parallel to the DC bus, and the input terminals of the above-mentioned at least two converters are connected in parallel to the same DC bus (the DC bus shown in FIG. 8 ). Wherein, the DC converter in the power system can be used to perform DC conversion on the DC power provided by the DC power supply, and output it to the DC bus. A DC bus can be used to provide DC voltage to the converter. In this embodiment, the input ends of at least two converters included in the power system are connected in parallel to the same DC bus, and the converters are applied to the power system, which can also be called the DC side paralleling scenario. Then, due to the interactive coupling between these converters and between the converters, the DC converter and the DC power supply, resonance is likely to occur at the input port side of the at least two converters. In this scenario, the control module in any one of the above-mentioned at least two converters can be used to obtain the effective value of the input current or the effective value of the input voltage of the converter, and the effective value of the input current Or when the effective value of the input voltage is greater than the resonance threshold, control the inverter module in the converter to reduce the output power or adjust the switching frequency to suppress the resonance. Wherein, the process for the control module in each converter to obtain the effective value of the input current or the effective value of the input voltage of the converter can refer to the relevant description above, and will not be repeated here. That is to say, in the scenario where multiple converters are paralleled on the DC side, since DC side resonance is likely to occur, the control modules in each converter can be based on the effective value of the input current or the input voltage of the inverter. Detects the presence of resonance and takes steps to suppress it when it is detected. In this way, the resonance occurring on the DC port side of the converter can be detected quickly and in real time, the speed and effect of resonance detection can be improved, and it is beneficial to eliminate the resonance in time when the resonance occurs, thereby improving the stability and reliability of the power system.

In some feasible implementation modes, please refer to Fig. 9, as shown in Fig. 9, the present application also provides a power system, which includes at least two converters (converter 1, ... in Fig. 9 ..., converter n, n is greater than or equal to 2), and also includes a DC bus and one or more DC converters (such as DC converter 1 in Figure 9, ..., DC converter m, m is greater than or equal to 1 ), the structure of each converter can be shown in Figure 2 or Figure 3. The input ends of each DC converter are connected to a DC power supply. As shown in FIG. 9 , one DC converter can be connected to one DC power supply. This application does not limit the number of DC power supplies included in the power system. The output terminals of each DC converter are connected in parallel to the above-mentioned DC bus, the input terminals of the above-mentioned at least two converters are connected in parallel to the same DC bus (the DC bus shown in Figure 9), and the output terminals of the above-mentioned at least two converters After parallel connection, they are connected to the AC grid through the same transformer. That is to say, the input ends of at least two converters in the power system are connected in parallel to the same DC bus, and the output ends are connected in parallel to the same transformer. AC and DC side paralleling scenarios. In this scenario, due to the interactive coupling between the converters and between the converters and the grid, the converters and the DC converter and the DC power supply, it is possible to occur on the AC port side of the at least two converters Resonance may also occur on the DC port side of the at least two converters. In the AC/DC parallel scenario, the control module in any one of the at least two converters can be used to obtain the input current effective value, input voltage effective value, and output current effective value of the converter. value or the effective value of the output voltage, and when the corresponding effective value is greater than the above-mentioned resonance threshold, control the inverter module in the converter to reduce the output power or adjust the switching frequency to suppress the resonance. That is to say, in the scenario where multiple converters are paralleled on the AC and DC sides, since DC side resonance and AC side resonance are prone to occur, the control modules in each converter can be based on the effective value of the input current of the inverter, Input voltage RMS, output current RMS or output voltage RMS to detect the existence of resonance, and take measures to suppress resonance when resonance is detected. Wherein, the control module in each converter obtains the effective value of the input current, the effective value of the input voltage, the effective value of the output current or the effective value of the output voltage of the inverter module in the converter. description and will not be repeated here. In this way, in the scenario where multiple converters are paralleled on the AC and DC sides, regardless of whether resonance occurs on the DC side port or the AC side port of the converter in the power system, the resonance can be detected quickly and in real time, and the resonance detection speed is improved. Suppressing resonance in time is conducive to improving the stability and reliability of the power system.

In some feasible implementation manners, the control module in each converter of the above at least two converters may be independent, that is, one converter includes one control module. Optionally, two or more control modules included in two or more converters among the above-mentioned at least two converters may also be integrated, that is, two or more converters correspond to a control module. The control module may be a control device independent of the converter. Specifically, it may be determined according to an actual application scenario, which is not limited in the present application.

In this application, the control module in the converter obtains the effective value of the output current of the converter by obtaining a plurality of sampling values of the output current of the converter within one power frequency cycle. Wherein, the sampling value of the output current of the converter can be obtained based on the sampling information of the existing filter inductor and filter capacitor, and the process of calculating the effective value of the output current of the converter is simple and efficient, without adding additional detection lines and calculations. After obtaining the effective value of the output current, determine whether resonance occurs based on the relationship between the effective value of the output current and the resonance threshold. Since the effective value of the output current can reflect the amplitude of each harmonic in the output current of the converter, it can be It can intuitively reflect whether resonance exists, so adopting this method is conducive to quickly identifying resonance and improving system safety and reliability.

Please refer to FIG. 10 , which is a schematic flowchart of a resonance detection method provided in the present application. The method can be applied to the control module in the converter. The converter also includes an inverter module, a filter inductor, a filter capacitor and a DC capacitor unit. The input end of the inverter module is connected to a DC power supply, and the output of the inverter module is The terminal is connected to the AC power grid; the structure of the converter can be shown in any one of Figures 3-6, and the converter can be applied to the application scenarios shown in Figure 1, Figure 7, Figure 8, or Figure 9 .

As shown in Figure 10, the method may include but not limited to the following steps:

In step S1001, the control module in the converter obtains multiple sampled values of the output current of the converter or multiple sampled values of the input voltage of the converter within one power frequency cycle.

Specifically, when the converter is connected to the grid with multiple machines and the AC side is paralleled, the control module can obtain multiple sampled values of the output current of the converter within one power frequency cycle. When the converter is connected to the grid and the DC side is paralleled, the control module can obtain multiple sampled values of the input voltage of the converter within one power frequency cycle. When the converter is connected to the grid and the AC and DC sides are paralleled, the control module can obtain multiple output current sampling values of the converter or multiple input voltages of the converter within one power frequency cycle The sampled values can also obtain multiple sampled values of the output current of the converter and multiple sampled values of the input voltage of the converter within one power frequency cycle.

In some feasible implementation manners, as shown in FIG. 3 , the converter may include an inverter module, a filter capacitor and a filter inductor, wherein the input end of the inverter module is used to connect to a DC power supply, and the inverter module The output end is connected to one end of the filter inductance, the other end of the filter inductance is connected to one end of the filter capacitor, and the connection point is used as the output end of the converter to connect to the AC grid. Here, the circuit topology of the inverter module may be a multi-level topology. The control module in the converter can obtain multiple sampled values of the output current of the converter based on the multiple sampled values of the inductor current of the filter inductor and the multiple sampled values of the capacitive current of the filter capacitor within the power frequency cycle. Specifically, each sampled value of the output current is obtained based on a difference between a sampled value of the inductor current and a sampled value of the capacitor current. It can be understood that the sampled value of the output current of the filter inductor and the sampled value of the filter capacitor belong to the sampling information that the converter needs to obtain. Therefore, the control module in the converter can be directly based on the output current of the filter inductor. The sampled value and the sampled value of the output current of the filter capacitor are used to obtain the sampled value of the output current of the converter, thus saving circuit cost and being simple and efficient.

In some feasible implementation manners, as shown in FIG. 3 , the input terminal of the inverter module is connected to the DC power supply through the DC capacitor module, where the input voltage of the DC capacitor module is equal to the input voltage of the converter. Therefore, the control module in the converter can obtain multiple sampled values of the input voltage of the DC capacitor module in one power frequency cycle as the multiple sampled values of the input voltage of the converter in the power frequency cycle. Optionally, when the DC capacitor module includes a first capacitor and a second capacitor as shown in FIG. 4 , the control module can obtain the input voltage of the DC capacitor module based on the sum of the input voltages of the first capacitor and the second capacitor. Optionally, when the DC capacitor module includes a third capacitor as shown in FIG. 5 , the control module may obtain the input voltage of the third capacitor as the input voltage of the DC capacitor module. Optionally, when the DC capacitor module includes the first capacitor, the second capacitor and the third capacitor as shown in Figure 6, the control module can obtain the DC capacitor module based on the sum of the input voltages of the first capacitor and the second capacitor Input voltage. The control module can also obtain the input voltage of the third capacitor as the input voltage of the DC capacitor module. Since the voltage sampling information of the first capacitor, the second capacitor or the voltage sampling information of the third capacitor is the existing sampling information, the sampling information of the existing DC filter capacitor is directly used to obtain the input voltage sampling value of the converter, and then The effective value of the input voltage of the inverter module is obtained, the method is simple and efficient, can improve the speed of resonance detection, and save circuit cost.

Step S1002, obtaining an effective value of the output current of the converter based on a plurality of sampling values of the output current or obtaining an effective value of the input voltage of the converter based on a plurality of sampling values of the input voltage.

For the convenience of description, the process of obtaining the effective value of the output current of the converter is taken as an example for introduction. Assuming that the above-mentioned multiple output current sample values include N output current sample values, then the control module can obtain the above-mentioned output current based on the average value of the N output current sample values and the root mean square of the N output current sample values valid value. Wherein, the value of N is greater than or equal to twice the switching frequency of the inverter module. Specifically, the effective value of the output current can be obtained based on the above formula (1) and N sampled values of the output current. The effective value of the input voltage of the converter is obtained based on a plurality of input voltage sampling values. When , the output current i in formula (1) can be replaced by the corresponding input voltage u of the converter.

Step S1003, judging whether the effective value of the output current or the effective value of the input voltage is greater than the resonance threshold, if yes, execute step S1004, if not, return to step S1001.

Wherein, the resonance threshold can be specifically set based on the grid type, equipment requirements, etc., and no limitation is set here.

Step S1004, controlling the inverter module to reduce the output power or adjust the switching frequency to suppress the resonance.

Wherein, adjusting the switching frequency may include increasing the PWM control frequency and decreasing the PWM control frequency, which is not limited here. Understandably, by derating or adjusting the switching frequency, the operating point of the power system can be shifted so that the system avoids the resonance frequency point, thereby suppressing resonance. By suppressing the resonance through this method, the safety and stability of the system can be improved. In addition, since this method is a software control method, the resonance suppression can be realized through the software control method, and no additional inductance can be added to reduce the resonance frequency, so that the volume and weight of the equipment can be reduced, which is beneficial to save costs.

Step S1005, judging whether the duration of the effective value of the output current or the effective value of the input voltage is greater than the resonance threshold is greater than the reference duration, if yes, execute step S1006, if not, return to step S1001.

Wherein, the reference time length is equal to the resonance protection setting time of the converter, which can be set according to actual application scenarios, and is not limited in this application.

Step S1006, controlling the inverter module to stop working.

Specifically, a resonance alarm may be performed first, and then the inverter module is controlled to stop working, that is, the converter is controlled to be shut down. In this way, when the resonance cannot be suppressed in time, the machine can be shut down directly to avoid a greater negative impact on the power system.

In this application, the control module in the converter can obtain multiple sampled values of the output current of the converter in one power frequency cycle based on the sampling information of the filter inductor and filter capacitor, and obtain the effective value of the output current of the converter . The control module can also obtain a plurality of sampled values of the input voltage of the converter based on the sampling information of the DC capacitor module, and obtain an effective value of the input voltage of the converter. Among them, the effective value of the output current and the effective value of the input voltage of the converter can be obtained based on the existing sampling information, and the process of calculating the effective value is simple and efficient, without adding additional detection lines and calculations. After obtaining the above effective value, determine whether resonance occurs based on the relationship between the effective value and the resonance threshold, because the effective value of the output current and the effective value of the input voltage can visually reflect whether there are Resonance, so using this method is conducive to quickly identifying resonance and improving system safety and reliability.

The above is only a specific implementation of the application, but the scope of protection of the application is not limited thereto. Anyone familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the application. Should be covered within the protection scope of this application. Therefore, the protection scope of the present application should be determined by the protection scope of the claims.

Claims (14)

1. A converter, characterized in that it comprises: a control module, an inverter module, a filter inductor and a filter capacitor, the input end of the inverter module is used to connect to a DC power supply, and the output end of the inverter module is connected to One end of the filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor and the connection point is used as the output end of the converter to connect to the AC grid; The control module is used to obtain the effective value of the output current of the converter based on the multiple sampled values of the output current of the converter within one power frequency cycle, and the multiple sampled values of the output current of the converter Obtained based on multiple sampled values of the inductor current of the filter inductor and multiple sampled values of the capacitor current of the filter capacitor within the power frequency period; The control module is also used to control the inverter module to suppress resonance when the effective value of the output current of the converter is greater than the resonance threshold. 2. The converter according to claim 1, characterized in that one of the multiple output current sampling values of the converter is based on the difference between an inductor current sampling value and a capacitor current sampling value get. 3. The converter according to claim 2, wherein the converter further comprises a DC capacitor module, and the input end of the inverter module is connected to the DC power supply through the DC capacitor module; The control module is further configured to obtain an effective value of the input voltage of the converter based on a plurality of sampling values of the input voltage of the DC capacitor module within one power frequency cycle; The control module is further configured to control the inverter module to suppress resonance when the effective value of the input voltage of the converter is greater than the resonance threshold. 4. The converter according to claim 3, wherein the DC capacitor module includes a first capacitor and a second capacitor connected in series, and the first capacitor and the second capacitor connected in series are connected with the inverter module The input ends of the capacitors are connected in parallel, and the series connection point of the first capacitor and the second capacitor is connected to the other end of the filter capacitor as the capacitor midpoint; The control module is further configured to obtain the input voltage of the DC capacitor module based on the sum of the input voltage of the first capacitor and the input voltage of the second capacitor. 5. The converter according to claim 3, wherein the DC capacitor module includes a third capacitor, and the third capacitor is connected in parallel with the input terminal of the inverter module; the control module is also used for The input voltage of the third capacitor is obtained as the input voltage of the DC capacitor module. 6. The converter according to any one of claims 1-5, characterized in that, the control module is also used for when the effective value of the output current or the effective value of the input voltage of the converter is greater than the resonance threshold When the duration is greater than or equal to the reference duration, the inverter module is controlled to stop working. 7. An electric power system, characterized in that the electric power system comprises at least two converters according to any one of claims 1-6, and the output terminals of the at least two converters are connected in parallel connecting the AC grid through a transformer; The control module in any one of the at least two converters is used to obtain the effective value of the output current of the converter, and when the effective value of the output current is greater than the resonance threshold, control the The inverter module in the above-mentioned converter suppresses the resonance. 8. A power system, characterized in that the power system comprises at least two converters as claimed in any one of claims 3-6, a DC bus and one or more DC converters, each DC converter The input end of the DC power supply is connected to the DC power supply, the output ends of each DC converter are connected in parallel to the DC bus, and the input ends of the at least two converters are connected in parallel to the DC bus; The control module in any one of the at least two converters is used to obtain the effective value of the input voltage of the inverter module in the converter, and when the effective value of the input voltage is greater than the resonance threshold, controlling the inverter module in the converter to suppress resonance; The DC converter is used for performing DC conversion on the DC power provided by the DC power supply and outputting it to the DC bus. 9. A resonance detection method, characterized in that it is applied to a control module in a converter, the converter also includes an inverter module, a filter inductor and a filter capacitor, and the input terminal of the inverter module is used to connect DC power supply, the output end of the inverter module is connected to one end of the filter inductor, the other end of the filter inductor is connected to one end of the filter capacitor and the connection point is used as the output end of the converter to connect to the AC grid; The methods include: Obtain an effective value of the output current of the converter based on a plurality of sampled values of the output current of the converter within a power frequency cycle, where the multiple sampled values of the output current of the converter are based on the power frequency cycle A plurality of sampled values of the inductor current of the filter inductor and a plurality of sampled values of the capacitor current of the filter capacitor are obtained; When the effective value of the output current of the converter is greater than a resonance threshold, the inverter module is controlled to suppress resonance. 10 . The method according to claim 9 , wherein one output current sampling value among the plurality of output current sampling values of the converter is obtained based on a difference between an inductor current sampling value and a capacitor current sampling value. 11 . 11. The method according to claim 10, wherein the converter further comprises a DC capacitor module, and the input terminal of the inverter module is connected to the DC power supply through the DC capacitor module; the method further comprises include: Obtaining an effective value of the input voltage of the converter based on a plurality of sampling values of the input voltage of the DC capacitor module within one power frequency cycle; When the effective value of the input voltage of the converter is greater than the resonance threshold, the inverter module is controlled to suppress resonance. 12. The method according to claim 11, wherein the DC capacitor module includes a first capacitor and a second capacitor connected in series, and the first capacitor connected in series and the second capacitor are connected to the input of the inverter module terminals in parallel, and the series connection point of the first capacitor and the second capacitor is connected to the other end of the filter capacitor as the capacitor midpoint; the method further includes: based on the input voltage of the first capacitor and the The sum of the input voltages of the second capacitors is used to obtain the input voltage of the DC capacitor module. 13. The method according to claim 11, wherein the DC capacitor module includes a third capacitor, and the third capacitor is connected in parallel with the input terminal of the inverter module; the method further includes: The input voltage of the third capacitor is obtained as the input voltage of the DC capacitor module. 14. The method according to any one of claims 9-13, wherein the method further comprises: When the effective value of the output current or the effective value of the input voltage of the converter is greater than the resonance threshold for a duration greater than or equal to a reference duration, the inverter module is controlled to stop working.

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