CN116317818B

CN116317818B - A high-voltage circuit system and its control method

Info

Publication number: CN116317818B
Application number: CN202310126139.XA
Authority: CN
Inventors: 周双雷; 杨凡; 周祥柱; 李晨; 杜壮
Original assignee: CRRC Qingdao Sifang Rolling Stock Research Institute Co Ltd
Current assignee: CRRC Qingdao Sifang Rolling Stock Research Institute Co Ltd
Priority date: 2023-02-16
Filing date: 2023-02-16
Publication date: 2025-11-25
Anticipated expiration: 2043-02-16
Also published as: CN116317818A

Abstract

This application discloses a high-voltage circuit system and its control method. The high-voltage circuit system includes: a main isolation contactor KM1; a low-pass filter unit, including a filter support capacitor FC and a filter reactor FL, one end of the filter capacitor FC being connected to the filter reactor FL; and an IGBT electronic switch KMQ, one end of the IGBT electronic switch KMQ being connected to the filter reactor FL, and the other end being connected to the main isolation contactor KM1. When a high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ and the main isolation contactor KM1 are closed, and the filter support capacitor FC begins to charge, causing the voltage of the filter support capacitor FC to rise. When the voltage difference between the voltage of the filter support capacitor FC and the battery voltage reaches a preset voltage difference, it is determined that the filter support capacitor FC has completed pre-charging, and the IGBT electronic switch KMQ is opened, causing the filter support capacitor FC to stop charging.

Description

High-voltage circuit system and control method thereof

Technical Field

The application relates to the field of urban rail vehicle high-voltage circuits, in particular to a high-voltage circuit system and a control method thereof.

Background

The rail transit high-voltage electric system generally comprises a high-voltage input stage and a variable-current load stage, wherein the variable current is generally a three-phase inverter, a DC/DC converter, a rectifier and the like which are formed by power electronic devices such as IGBT (insulated gate bipolar transistor), diode, MOSFET (metal oxide semiconductor field effect transistor) and the like, and the high-voltage electric system is sensitive to voltage and current impact input from the high-voltage stage and easy to damage. Correspondingly, the high-voltage stage mainly comprises high-voltage protection devices, and can play roles in buffering, isolating and protecting intermediate impact energy of a power supply grid and a rear-stage current transformation system, precharging a supporting capacitor, converting a power supply mode and the like.

As shown in fig. 1, the high-voltage topology of the rail transit vehicle generally includes a grid voltage sensor TV0, a grid current sensor TA1, a main isolation contactor KM1, a precharge contactor KM2, a precharge resistor R1, a filter reactor FL, a filter support capacitor FC, an FC capacitor voltage sensor TV1, and the like. FL and FC form a low-pass filter unit, FC is generally 4mF, FL is generally 4mH, KM1, KM2 and R1 form a high-voltage isolating switch and function of pre-charging FC capacitor, and R1 is generally 150 ohms. The existing topology has the following disadvantages:

1. The number of high-voltage input stage devices is large, the structure is complex, the cost is high, the precharge time is too long, and the precharge time is generally more than 2s;

2. the coordination relation among KM1, KM2 and R1 is complex, multiple mechanical actions are required to be executed, the service life of the contactor is greatly influenced, the failure rate of the precharging problem is obviously higher than that of other components, and vehicles cannot be started normally even trains get off the line when clear;

3. during the precharge period, the resistor R1 bears heat of up to 5kJ or more in 0.1s, the short-time overload requirement on the resistor is very high, the calculation and control of the accumulated energy of the resistor are unsuitable, the resistor is often blown or short-circuited, and serious operation faults are caused;

4. KM1 is used as an electrical isolation switch of a high-voltage system, when the system fails, a power grid high voltage and an inverter are disconnected, the slow isolation protection function is achieved, KM2 and R1 are only used as current limiting pre-charging of an FC capacitor, the power grid is prevented from directly charging the capacitor through an FL reactor, the pre-charging process is abnormal due to faults of a TV0 sensor, a TV1 sensor and an R1 pre-charging resistor, the capacitor damage is caused by uncontrollable overcharge, the KM1 main contactor is damaged, and the formed oscillating voltage can damage a relatively fragile three-phase inverter. Meanwhile, the action relation of KM1 and KM2 is controlled by the difference value of the FC voltage and the power grid voltage, KM1 cannot be closed when the difference value is too large, a precharge fault can be reported when the difference value is too large for more than 2s, the system is locked, and the system is locked due to fluctuation of the power grid voltage and zero drift of a sensor;

5. KM1 is a mechanical action switch, the action response is as long as 100ms, the time for isolating the back side inverter system is long, the device can be used as faults such as IGBT overtemperature and the like with low protection time, and the risk of the back side system being affected is high.

Therefore, the traditional high-voltage input structure is mature, but the defects of high cost and high failure rate exist at the same time, and the rapid protection cannot be provided for the later-stage system. Therefore, a new high-voltage topology and a control method thereof are needed, which can realize the pre-charging of the system without time limitation and times, have higher reliability, and can provide rapid power grid cut-off action for the power electronic system with weak later stage.

Disclosure of Invention

The embodiment of the application provides a high-voltage circuit system and a control method thereof, which at least solve the problems of high number of high-voltage input stage devices, complex structure, higher cost, overlong precharge time, high risk of system oscillation, short service life, high failure rate and low protection circuit efficiency of a mechanical switch.

The invention provides a high-voltage circuit system and a control method thereof, wherein the high-voltage circuit system comprises:

a main isolation contactor KM1;

the low-pass filtering unit comprises a filtering supporting capacitor FC and a filtering reactor FL, and one end of the filtering capacitor FC is connected with the filtering reactor FL;

an IGBT electronic switch KMQ, one end of which is connected with the filter reactor FL and the other end of which is connected with the main isolation contactor KM 1;

When a high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ and the main isolation contactor KM1 are closed, the filter supporting capacitor FC starts to charge, so that the voltage of the filter supporting capacitor FC rises, when the voltage difference between the voltage of the filter supporting capacitor FC and the voltage of a battery reaches a preset voltage difference, the filter supporting capacitor FC is judged to finish precharge, and the IGBT electronic switch KMQ is disconnected, so that the filter supporting capacitor FC stops charging.

The high-voltage circuit system further includes:

grid voltage sensor TV0;

The network current sensor TA1 is connected with one end of the power grid voltage sensor TV0, and the other end of the network current sensor TA1 is connected with the main isolation contactor KM 1;

One end of the FC capacitor voltage sensor is connected with the filter reactor FL;

the three-phase inverter is connected with the filter supporting capacitor FC;

When high voltage is applied to the high-voltage circuit system, the main isolation contactor KM1 and the IGBT electronic switch KMQ are closed, current flows through the net flow sensor TA1, the main isolation contactor KM1, the IGBT electronic switch KMQ, the filter reactor FL and the filter supporting capacitor FC from a voltage source DC in sequence, and the current flows into a high-voltage circuit branch after flowing through the positive pole of the filter supporting capacitor FC in a shunting way.

In the high-voltage circuit system, the high-voltage circuit branch comprises a first high-voltage circuit branch and a second high-voltage circuit branch;

after flowing into the first high-voltage circuit branch, the current flows to the three-phase inverter, and flows out from the negative electrode of the inverter to return to GND;

After the current flows into the second high-voltage circuit branch, the current flows into the filter support capacitor FC, so that the filter support capacitor FC is charged, and flows out from the negative electrode of the filter support capacitor FC to return to the GND.

The invention also provides a control method of the high-voltage circuit system, which is characterized by comprising a direct charging precharge control method, a modulation-free precharge control method based on an LC model, a precharge control method based on an exponential function and a power grid overvoltage cutoff protection control method.

In the above-mentioned control method of the high-voltage circuit system, the direct-charging precharge control method includes:

when a high voltage is applied to the high-voltage circuit system, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, the current flows into the second branch, and the filter supporting capacitor FC starts to charge.

In the above-mentioned control method of high-voltage circuit system, the modulation-free precharge control method based on LC model includes:

and establishing a first high-voltage circuit system simulation model based on the LC model through a simulation tool, and presetting the optimal switching width and frequency.

In the above control method for a high-voltage circuit system, the modulation-free precharge control method based on the LC model further includes:

when high voltage is applied to the high-voltage circuit system, the first high-voltage circuit system simulation model is adopted to conduct the IGBT electronic switch KMQ in a staggered mode according to the preset optimal switch width and the preset frequency, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, the current flows into the second branch, and the filter supporting capacitor FC starts to charge;

and judging whether the precharge of the filter support capacitor FC is finished or not, and when the judgment result is that the precharge of the filter support capacitor FC is finished, switching the state of the IGBT electronic switch KMQ from staggered conduction to normal conduction.

In the above control method of a high-voltage circuit system, the precharge control method based on an exponential function includes:

and establishing a second high-voltage circuit system simulation model based on an exponential function through the simulation tool, and selecting a first nonlinear exponential coefficient and a second nonlinear exponential coefficient through the simulation tool according to an impact minimum principle.

when the high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ is conducted in a nonlinear staggered mode by adopting the second high-voltage circuit system simulation model according to the first nonlinear index coefficient and the second nonlinear index coefficient, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, the current flows into the second branch, and the filter supporting capacitor FC starts to charge;

And judging whether the precharge of the filter support capacitor FC is finished or not, and when the judgment result is that the precharge of the filter support capacitor FC is finished, switching the state of the IGBT electronic switch KMQ from nonlinear staggered conduction to normal conduction.

In the above control method for a high-voltage circuit system, the control method for overvoltage shutdown protection of a power grid includes:

When the voltage difference of the high-voltage circuit system detected by the power grid voltage sensor exceeds a standard voltage difference, the voltage difference of the high-voltage circuit system is detected again after the IGBT electronic switch KMQ is closed, and when the voltage difference is reduced to the standard voltage difference, the IGBT electronic switch KMQ is opened to realize overvoltage cut-off protection of the high-voltage circuit system.

Compared with the prior art, the high-voltage circuit system and the control method thereof provide a train traction high-voltage system electrical topology of a high-voltage loop series power electronic switch, fewer devices, lower cost, higher pre-charge efficiency and lower fault rate, the pre-charge control strategy is determined through a numerical calculation or model simulation method, a direct charge or multi-pulse control strategy based on an LC model is formulated according to data, the design method of the multi-pulse pre-charge control strategy is provided, an executable simulation model, a pulse sequence and a control beat are provided, a fixed pulse width multi-pulse sequence method with simple control is provided, the multi-pulse pre-charge control strategy based on an exponential function is provided, a specific formula of a nonlinear exponential function is provided, the exponential function control parameter is optimized through a more visual simulation model, the non-advanced multi-pulse sequence and a new circuit structure have a better matching relation, the pre-charge process can be completed uniformly and rapidly, a single-pulse pre-throw power grid overvoltage cut-off protection strategy is provided, a cut-off strategy is determined between KMCEs when the overvoltage is identified, the differential pressure exceeds a threshold value, the KMQ single-pulse pre-throw cut-off power grid differential pressure is provided, and then the rapid protection of the power grid is realized.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:

FIG. 1 is a prior art high voltage circuit topology according to an embodiment of the present application;

FIG. 2 is a high voltage circuit topology according to an embodiment of the present application;

FIG. 3 is a high voltage loop equivalent second order circuit according to an embodiment of the present application;

FIG. 4 is a matlab simulation model of an RLC series equivalent second order circuit according to an embodiment of the present application;

FIG. 5 is a matlab simulation waveform under severe operating conditions in accordance with an embodiment of the present application;

FIG. 6 is a matlab simulation waveform under suitable operating conditions in accordance with an embodiment of the present application;

FIG. 7 is a matlab simulation waveform with a pulse width greater than one-quarter cycle in accordance with an embodiment of the present application;

FIG. 8 is a matlab simulation waveform with pulse widths less than and near one-quarter cycle in accordance with an embodiment of the present application;

FIG. 9 is a matlab simulation waveform with pulse widths less than and far from a quarter cycle in accordance with an embodiment of the present application;

FIG. 10 is a matlab simulation waveform for a fixed narrow pulse width multi-period in accordance with an embodiment of the present application;

FIG. 11 is an exponential function based precharge control matlab simulation model according to an embodiment of the present application;

FIG. 12 is an exponential function based precharge control matlab simulation waveform according to an embodiment of the present application;

Fig. 13 is a single pulse pre-cast grid overvoltage shutdown protection according to an embodiment of the application.

Wherein, the reference numerals are as follows:

TV0, a grid voltage sensor;

TA1, a network flow sensor;

KM1, a main isolation contactor;

KMQ, IGBT electronic switch;

FL is a filter reactor;

FC is a filter support capacitor;

TV1, FC capacitor voltage sensor;

CTU is a U-phase current sensor;

CTW is a W-phase current sensor;

and M is a traction motor.

Detailed Description

The present application will be described and illustrated with reference to the accompanying drawings and examples in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application. All other embodiments, which can be made by a person of ordinary skill in the art based on the embodiments provided by the present application without making any inventive effort, are intended to fall within the scope of the present application.

It is apparent that the drawings in the following description are only some examples or embodiments of the present application, and it is possible for those of ordinary skill in the art to apply the present application to other similar situations according to these drawings without inventive effort. Moreover, it should be appreciated that while such a development effort might be complex and lengthy, it would nevertheless be a routine undertaking of design, fabrication, or manufacture for those of ordinary skill having the benefit of this disclosure, and thus should not be construed as having the benefit of this disclosure.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is to be expressly and implicitly understood by those of ordinary skill in the art that the described embodiments of the application can be combined with other embodiments without conflict.

Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. The terms "a," "an," "the," and similar referents in the context of the application are not to be construed as limiting the quantity, but rather as singular or plural. The terms "comprises," "comprising," "includes," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or modules (elements) is not limited to only those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. The terms "connected," "coupled," and the like in connection with the present application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "plurality" as used herein means two or more. "and/or" describes the association relationship of the association object, and indicates that three relationships may exist, for example, "a and/or B" may indicate that a exists alone, a and B exist simultaneously, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship. The terms "first," "second," "third," and the like, as used herein, are merely distinguishing between similar objects and not representing a particular ordering of objects.

The invention provides a high-voltage circuit system and a control method thereof, which realize the precharge of the system without time and times, have higher reliability and provide quick power grid cutting-off action for a power electronic system with weak later stage.

The following will describe embodiments of the present application by taking a high-voltage circuit system and a control method thereof as examples.

Example 1

The embodiment provides a high-voltage circuit system and a control method thereof. Referring to fig. 2, fig. 2 is a high-voltage circuit topology according to an embodiment of the present application, and as shown in fig. 2, the high-voltage circuit system includes:

a main isolation contactor KM1;

One end of the IGBT electronic switch KMQ is connected with the filter reactor FL, and the other end of the IGBT electronic switch KMQ is connected with the main isolation contactor KM 1;

When high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ and the main isolation contactor KM1 are closed, the filter supporting capacitor FC starts to charge, the voltage of the filter supporting capacitor FC rises, when the voltage difference between the voltage of the filter supporting capacitor FC and the voltage of a battery reaches a preset voltage difference, the filter supporting capacitor FC is judged to complete precharge, the IGBT electronic switch KMQ is disconnected, and the filter supporting capacitor FC stops charging.

In an embodiment, the high voltage circuit system further comprises:

grid voltage sensor TV0;

the three-phase inverter is connected with the filter supporting capacitor FC;

When high voltage is applied to the high-voltage circuit system, the main isolation contactor KM1 and the IGBT electronic switch KMQ are closed, current flows through the net flow sensor TA1, the main isolation contactor KM1, the IGBT electronic switch KMQ, the filter reactor FL and the filter supporting capacitor FC from a voltage source DC in sequence, and the current flows into a high-voltage circuit branch after flowing through the positive pole of the filter supporting capacitor FC in a shunting way;

The high-voltage circuit branch circuit comprises a first high-voltage circuit branch circuit and a second high-voltage circuit branch circuit;

In a specific embodiment, the new high-voltage circuit consists of a TV0, a TA1, a KM1, KMQ, FL, TV1, an FC, a three-phase inverter, CTU, CTW, M and the like, wherein the TV0, the TA1, the KM1, the KMQ, FL, TV1 and the FC jointly form a high-voltage input stage circuit, the high-voltage measurement of the TV0 is being connected to DC+ of a high-voltage input power supply, the high-voltage measurement of the TV0 is being connected to GND of the high-voltage input power supply, the connection point "+" of the KM1 is connected to DC+ of the high-voltage input power supply, the connection point "-" of the KM1 is sequentially connected to the C pole of the IGBT KMQ, the C pole of the IGBT KMQ is connected to the connection point "+" of the FL, the connection point "-" of the FL is sequentially connected to the connection point "+" of the FC, the connection point "-" of the FC is connected to GND of the high-voltage input power supply, the high-voltage measurement of the TV1 is being connected to the connection point "-" of the FC or the GND of the high-voltage input power supply, and the measurement hole of the TA1 is threaded through a wire between the connection point "+" of the FC of the high-voltage power supply and the power supply. The connection point "+" of the FC is connected to the high-voltage input end "+" of the three-phase inverter through the low-sense busbar, and the connection point "-" of the FC is connected to the high-voltage input end "-" of the three-phase inverter through the low-sense busbar. The three-phase output of the three-phase inverter is connected to the three-phase input end of the M, and measuring holes of the CTU and the CTW respectively penetrate through U-phase and W-phase leads between the three-phase inverter and the M;

the intelligent power grid comprises a TV0, a power grid voltage sensor, a TA1, a grid current sensor, a KM1, a main isolation contactor, a KMQ, an IGBT electronic switch, a FL, a filter reactor, an FC, a filter support capacitor, a TV1, an FC capacitor voltage sensor, a CTU, a U-phase current sensor, a CTW, a W-phase current sensor and a traction motor.

The working principle of the high-voltage circuit is that when KM1 and KMQ are closed and conducted, the high-voltage input stage circuit is in a positive and reverse complete conduction state, when energy flows in the positive direction, current flows from DC+ to TA1, KM1 and KMQ, FL, FC of the main circuit in sequence, the current flowing through "+" of FC is split into two branches, the first branch flows to the three-phase inverter and flows back to GND from the negative pole of the inverter, the second branch flows back to GND from "-" of FC through the capacitor FC, capacitor charging capacitor voltage TV1 is lifted, if the inverter stops working, the first branch stops working and does not have current, if the amplitude and phase of network voltage TV0 and FC voltage TV2 are identical, the second branch stops working and does not have current, a complete backflow loop is formed, when energy flows in the reverse direction, the current flows in the reverse direction, the first branch and the second branch are combined to DC+, the capacitor FC discharges capacitor voltage TV1 drops, and the directions of the FC and the three-phase inverter have positive or negative circulation currents according to the working states.

When KM1 is on and KMQ is off, the circuit is partially off, and only energy flows reversely, such as negative half wave when oscillation occurs.

When KM1 is closed and KMQ is conducted, the circuit is completely closed, and no current flows and energy exchange are caused.

Example two

Referring to fig. 3 to 13, fig. 3 is a high voltage loop equivalent second order circuit according to an embodiment of the present application, fig. 4 is an RLC series equivalent second order circuit matlab simulation model according to an embodiment of the present application, fig. 5 is a matlab simulation waveform under severe conditions according to an embodiment of the present application, fig. 6 is a matlab simulation waveform under suitable conditions according to an embodiment of the present application, fig. 7 is a matlab simulation waveform under pulse width greater than a quarter period according to an embodiment of the present application, fig. 8 is a matlab simulation waveform under pulse width less than and close to a quarter period according to an embodiment of the present application, fig. 9 is a matlab simulation waveform under pulse width less than and far from a quarter period according to an embodiment of the present application, fig. 10 is a fixed narrow pulse width multi-period matlab simulation waveform according to an embodiment of the present application, fig. 11 is a pre-charge control matlab simulation model based on an exponential function according to an embodiment of the present application, fig. 12 is a pre-charge control matlab simulation waveform based on an exponential function according to an embodiment of the present application, and fig. 13 is a single cut-off pre-pulse protection grid according to an embodiment of the present application. As shown in fig. 3 to 13, the control method of the high-voltage circuit system of the present application is applicable to the above-mentioned high-voltage circuit system, and the control method of the high-voltage circuit system includes:

The method comprises a direct charging precharge control method, a modulation-free precharge control method based on an LC model, a precharge control method based on an exponential function and a power grid overvoltage cutoff protection control method.

In an embodiment, a direct charge precharge control method includes:

When high voltage is applied to the high-voltage circuit system, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, current flows into the second branch, and the filter supporting capacitor FC starts to charge.

In specific implementation, there are two KMQ control strategies, one is uncontrolled, the FC capacitor is directly flushed by the reactor, the other is controlled, the control strategy is not applied, so that the IGBT KMQ is always turned on, the high-voltage circuit is equivalent to the RLC second-order series circuit, as shown in fig. 3, wherein RFL is the equivalent resistance of the reactor FL and the circuit, the traction system is generally smaller, about 100-200 milliohms, DC is a standard voltage source, the voltage source of the urban rail generally adopts two systems, the DC750V power supply system and the DC1500V power supply system, when KM1 is closed, the system corresponds to the step response of the RLC second-order series circuit, and the traction system is designed and selected by LCSo for an underdamped system, the response of the current and FC voltage of the series system is:

Wherein, the

Resonant angular frequencyL is inductance value (H), C is capacitance value (F);

Attenuation factor R is the equivalent resistance (omega) of the circuit, namely the internal resistance of the reactor and the circuit resistance;

the intrinsic oscillation period T=2pi/omega ₀ of the system;

A is the power supply amplitude, ω is the power supply frequency, the fundamental wave occupies the main component for the present system, and other frequencies are not considered, so ω=ω ₀. As can be seen by calculation, the peak value of the line current i and the peak value of the capacitance voltage u _c are high, taking c=4000 uF of FC, l=4mh of FL, r=100mΩ of R _FL, and DC power supply a=1500v as examples, at the first 1/4 cycle of the fundamental wave:

i_max=1387.6A;

u_max=2895V;

It can be seen that the peak current and peak voltage are very high, well beyond the bearable range of the system devices.

The numerical calculation through the formula is not visual enough, the invention recommends a method of simulating by using simulation software such as MATLAB and the like to make a more visual time sequence diagram, and an RLC series equivalent second-order circuit MATLAB simulation model is shown in figure 4;

under certain suitable working conditions, a direct charging simple control strategy can be adopted, and the direct charging system is multipurpose in a system with low working voltage, small LC filtering, low output power and high switching frequency. Taking c=400 uF of FC, l=3mh of FL, r=200mΩ of R _FL, and a=750v of DC power supply as an example, matlab simulation waveforms under suitable conditions are shown in fig. 6, and it can be seen from the waveforms that under suitable conditions, the peak values of the first voltage and the first current in the step response are not very high, and the common device can bear in a short time, so that the control strategy of direct charging is suitable for use.

Therefore, in the process of designing a program, the control strategy of the KMQ needs to be determined by a numerical calculation or model simulation method, and a simple direct charging strategy which can be adopted properly is obtained, and a multi-stage pre-charging control strategy based on an LC model is adopted when the condition is bad.

The implementation steps of the direct charging precharge control method without control are as follows:

Step 1, preparing a system;

step 2, applying high voltage to the power grid, and opening KM1 and KMQ;

step 3, KMQ is closed, and direct charging control without control is applied;

Step 4, KM1 is closed, a circuit is conducted, a second branch works, and FC is charged;

And 5, after the precharge is completed, the KM1 and KMQ states are maintained, and the system starts to formally operate.

In an embodiment, a modulation-free precharge control method based on an LC model includes:

establishing a first high-voltage circuit system simulation model based on an LC model through a simulation tool, and presetting an optimal switching width and frequency;

When high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ is conducted in a staggered mode by adopting a first high-voltage circuit system simulation model according to the preset optimal switch width and the preset frequency, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, current flows into the second branch, and the filter supporting capacitor FC starts to charge;

In a specific implementation, when the switching pulse width T _purse > T/4, the voltage and current peak value crosses the highest point of free oscillation, and as oscillation is formed, negative oscillation occurs in the reactor current, only part of energy is stored in the FC, so that the charging effect is greatly reduced, and more serious, the impact on the device is larger due to the occurrence of the peak value of free oscillation. The pulse width is not suitable for the occasions with high voltage and large FC value. Matlab simulation waveforms at pulse widths greater than one-quarter cycle as shown in fig. 7.

When the switching pulse width T _purse is smaller than T/4, the pulse width is relatively close to T/4, the voltage and current peak value does not completely cross the highest point of free oscillation, only a 1/4 oscillation waveform is formed, the current of the reactor does not oscillate negatively, the oscillation energy is stored in the FC completely, the charging effect is very good, but the impact on the device is larger due to the fact that the peak value of free oscillation appears near. The pulse width is not suitable. The matlab simulation waveform at pulse widths less than and near one-quarter cycle as shown in fig. 8.

When the switching pulse width T _purse is smaller than T/4, the pulse width is about T/12, the voltage and current peak value is far away from the highest point of free oscillation, only partial initial waveform of oscillation is formed, negative oscillation does not occur in the reactor current, oscillation energy is stored in the FC completely, the charging effect is good, and the device cannot be impacted greatly due to the fact that the peak value of free oscillation occurs far away. The pulse width is proper. The matlab simulation waveform is shown in fig. 9 with pulse widths less than and far from the quarter cycle.

From the above analysis, it is clear that when the control pulse width is less than 1/4 of the natural oscillation period, the peak charging current and peak voltage amplitude decrease with decreasing pulse width, but the charging energy of each pulse width correspondingly decreases, the number of pulses to be charged increases, and a series of pulse control strategies are required, and the switching frequency f >2*f ₀ is within the acceptable range of KMQ to avoid oscillation. The method is suitable for medium-low voltage occasions capable of bearing certain current impact, cannot apply a complex control strategy, and has better effect than a direct charging precharge strategy without applying control.

The modulation-free precharge control method based on the LC model comprises the following specific implementation steps:

Step 1, establishing a system simulation model, and determining the optimal switching width and frequency;

step 2, preparing a system, and initializing each device;

step 3, applying high voltage to the power grid, and opening KM1 and KMQ;

step 4, KM1 is closed;

step 5, KMQ is closed, a fixed pulse width modulation-free control strategy based on an LC model is implemented, a circuit is conducted in a short time, a second branch works, and FC begins to charge;

Step 6, judging whether the precharge is completed or not, if not, repeating the step 5, and if so, turning to the step 7;

Step 7, after the precharge is finished, KMQ is changed from staggered conduction to normal conduction;

and 8, after the precharge is completed, the KM1 and KMQ states are maintained, and the system starts to formally operate.

In an embodiment, an exponential function-based precharge control method includes:

Establishing a second high-voltage circuit system simulation model based on an exponential function through a simulation tool, and selecting a first nonlinear exponential coefficient and a second nonlinear exponential coefficient through the simulation tool according to an impact minimum principle;

when high voltage is applied to the high-voltage circuit system, according to the first nonlinear index coefficient and the second nonlinear index coefficient, the second high-voltage circuit system simulation model is adopted to conduct the IGBT electronic switch KMQ in a nonlinear staggered mode, the main isolation contactor KM1 and the IGBT electronic switch KMQ are both closed, current flows into the second branch, and the filter supporting capacitor FC starts to charge;

In a specific implementation, taking a switching pulse width of T _purse =t/12 and a switching frequency of f=2.5×f ₀ as an example, a voltage and current peak is far away from the highest point of free oscillation, the peak gradually decreases along with the accumulation of FC charging charges, and the time for completing precharge is only 0.2s, which is far less than the time for charging through resistance current limiting, so that great optimization is obtained. Matlab simulation waveforms at fixed narrow pulse width multi-period as shown in fig. 10.

The modulation method of the fixed pulse width is too simple, the pulse of the initial section is too high in energy and the energy of the second half section is too low, so that the pulse utilization rate of the whole time section is not high. The invention provides a modulation method based on a nonlinear exponential function, u=k2×e ^k1*x, and the method realizes the stable early-stage growth and the rapid late-stage growth of the function, so that the opening energy is uniformly distributed. An exponential function based precharge control matlab simulation model is shown in fig. 11.

The k1 and k2 parameters are carefully adjusted by using simulation tools such as matlab and the like, so that the energy distribution is as uniform as possible, the larger the k1 parameter is, the longer the precharge time is, the larger the current and voltage peak value is, the larger the k2 parameter is, the larger the peak value of the early pulse is, and the uniformity of pulse energy distribution can be adjusted by using the k 2. The exponential function based precharge control matlab simulation waveforms of the present invention are illustrated in fig. 12 with k1=5 and k2=0.5 as examples.

It can be seen that the waveform is obviously uniform and much, the current and voltage pulse is also reduced much, the precharge time is about 0.25s, and is close to the fixed pulse, which is obviously better than the traditional precharge resistor type, but effectively reduces the switching stress of each device and improves the use safety. The method is suitable for high-voltage precharge occasions, and the effect is optimal in all strategies.

The precharge control method based on the exponential function comprises the following specific implementation steps:

Step 1, establishing a system simulation model, and selecting proper nonlinear index coefficients k1 and k2 according to an impact minimum principle;

step 2, preparing a system, and initializing each device;

step 3, applying high voltage to the power grid, and opening KM1 and KMQ;

step 4, KM1 is closed;

step 5, KMQ is closed, a precharge control strategy based on an exponential function is applied, a circuit is conducted in a short time, a second branch works, and FC begins to charge;

Step 7, after the precharge is finished, KMQ is turned into normal on from nonlinear staggered conduction;

In an embodiment, the method for controlling overvoltage shutdown protection of a power grid includes:

When the voltage difference of the high-voltage circuit system detected by the power grid voltage sensor exceeds the standard voltage difference, the voltage difference of the high-voltage circuit system is detected again after the IGBT electronic switch KMQ is closed, and when the voltage difference is reduced to the standard voltage difference, the IGBT electronic switch KMQ is opened to realize overvoltage cut-off protection of the high-voltage circuit system.

In specific implementation, the traditional topology cannot be effectively cut off when the power grid voltage is quickly raised due to slow action of the contactor, and the traditional topology can only rely on power electronic equipment with weaker post-stage compression resistance to bear too high voltage stress, so that the damage to devices is easily caused. The invention uses IGBT or equivalent power electronic device KMQ as line switch, which can cut off the power network rapidly to realize the post protection.

However, KMQ is also an electronic device, if the voltage born by CE is too high during turn-off, the KMQ can not only play a role in protection, but also can be damaged, so that the rapid protection is further optimized, the invention proposes to pulse pre-throw turn-off KMQ, when the TV0 detects overvoltage, the KMQ is quickly started first, the KMQ is quickly turned off when the KMQ pressure difference is allowed, if the KMQ is in a conducting state before overvoltage, the on time is properly prolonged, and the prolonged time depends on whether the KMQ pressure difference meets the safety requirement or not. In the railway standard, the maximum power grid voltage is U _max3, for un=dc1500v, U _max3 =dc2540V, the threshold of the IGBT drive board active clamp has been exceeded, and the drive board and IGBT will be severely damaged by continuous turn-on, so the inter-KMQ CE voltage needs to be limited to around 2200V. The worst condition is that the FC voltage is 0, only one pulse can be provided, and the on time is the worst case for Umax3 and FC of 0. Single pulse pre-cast grid overvoltage shutdown protection as shown in fig. 13.

It can be seen that the voltage difference is reduced below 2200V, the post-stage equipment is protected, the KMQ peak is large, but the fault is a serious system fault, rarely occurs, and is very necessary to use occasionally in a safety area of 2 times of the IGBT current. The protection flow is as follows, the differential pressure is small and is directly cut off, and the differential pressure is large by adopting single pulse. The method is suitable for the transient cut-off and rapid protection of the high-voltage circuit faults, the protection speed is faster than that of a KM1 mechanical contactor, and the protection is safer.

The method for controlling the overvoltage cutoff and rapid protection of the single-pulse pre-cast power grid comprises the following specific implementation steps:

step 1, completing system preparation, and closing and conducting KM1 and KMQ;

step 2, the system works normally and monitors the power grid voltage TV0 in real time;

Step 3, if the TV0 is normal, the process goes to step 2, and if the TV0 detects overvoltage, the process goes to step 4;

Step 4, if the voltage difference (DeltaU=T0-T1) between two ends of the KMQ exceeds the KMQ safety bearing value, switching to 5, otherwise switching to 7;

step 5, KMQ is closed or opened in a delayed mode (depending on the previous state of KMQ), a single pulse is applied, a circuit is turned on in a short time or closed in a delayed mode, a second branch is operated or closed in a delayed mode, FC starts to charge, and the voltage difference between two ends of KMQ starts to be reduced;

Step 6, judging whether the voltage difference between two ends of the KMQ meets the safety requirement, if not, continuing to conduct after the step 5 is completed, and if so, turning to the step 7;

7, finishing the quick protection, and switching KMQ from on to off;

and 8, finishing the rapid protection, maintaining the KM1 and KMQ states, and entering a fault processing program by the system.

In summary, the characteristics of the traditional high-voltage circuit are deeply analyzed, the electric topology of the train traction high-voltage system with the high-voltage circuit connected in series with the power electronic switch is provided, the device is fewer, the structure is simpler, the cost is lower, the precharge time is shorter, the fault rate is lower, the direct charge or multi-pulse control strategy based on an LC model is formulated for the novel high-voltage circuit, no mechanical action exists, the novel high-voltage circuit is independent of a sensor, is insensitive to voltage fluctuation of a power grid, no complex logic matching relation exists, the reliability and the service life are greatly improved, the design method of the multi-pulse precharge control strategy is provided, the precharge time is greatly reduced, the risk of oscillation of the system is reduced, the multi-pulse precharge control strategy based on an exponential function is provided, the charge pulse energy is more uniform, the impact on the current and the voltage of the device is further reduced, the fault rate is reduced, the single-pulse precharge protection strategy is provided, the rapid overvoltage protection of a post-stage system is realized, and compared with the protection method of the mechanical switch, and the rapid overvoltage protection effect is also better.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. The protection scope of the patent of the application shall therefore be subject to the protection scope of the appended claims.

Claims

1. A high voltage circuit system, the high voltage circuit system comprising:

a main isolation contactor KM1;

a grid voltage sensor TV0 connected in parallel between the positive and negative poles of the high voltage circuit;

When a high voltage is applied to the high-voltage circuit system, the IGBT electronic switch KMQ and the main isolation contactor KM1 are closed, the filter supporting capacitor FC starts to charge, so that the voltage of the filter supporting capacitor FC rises, when the voltage difference between the voltage of the filter supporting capacitor FC and the voltage of a power grid reaches a preset voltage difference, the filter supporting capacitor FC is judged to finish precharge, and the IGBT electronic switch KMQ is disconnected, so that the filter supporting capacitor FC stops charging;

when the voltage sensor TV0 detects the voltage overvoltage of the high-voltage circuit system and detects that the voltage difference between two ends of the IGBT electronic switch KMQ exceeds the standard voltage difference, the IGBT electronic switch KMQ is closed, the voltage difference between two ends of the IGBT electronic switch KMQ is detected again, and when the voltage difference between two ends of the IGBT electronic switch KMQ is reduced to the standard voltage difference, the IGBT electronic switch KMQ is opened, so that the overvoltage cut-off protection of the high-voltage circuit system is realized.

2. The high voltage circuitry of claim 1, further comprising:

the three-phase inverter is connected with the filter supporting capacitor FC;

3. The high voltage circuit system of claim 2, wherein the high voltage circuit branch comprises a first high voltage circuit branch and a second high voltage circuit branch;

4. A control method of a high-voltage circuit system, which is applied to the high-voltage circuit system as claimed in any one of claims 1 to 3, and is characterized in that the control method of the high-voltage circuit system comprises a direct charging precharge control method, a modulation-free precharge control method based on an LC model, a precharge control method based on an exponential function and a power grid overvoltage cutoff protection control method;

The power grid overvoltage cutoff protection control method comprises the following steps:

5. The control method of the high-voltage circuit system according to claim 4, wherein the direct-charge precharge control method includes:

6. The control method of the high-voltage circuit system according to claim 5, wherein the modulation-free precharge control method based on the LC model comprises:

7. The control method of the high-voltage circuit system according to claim 6, wherein the modulation-free precharge control method based on the LC model further comprises:

8. The control method of the high-voltage circuit system according to claim 5, wherein the precharge control method based on an exponential function comprises:

And establishing a second high-voltage circuit system simulation model based on an exponential function through a simulation tool, and selecting a first nonlinear exponential coefficient and a second nonlinear exponential coefficient through the simulation tool according to an impact minimum principle.

9. The control method of the high-voltage circuit system according to claim 8, wherein the precharge control method based on an exponential function comprises: