CN116566232A - A level conversion circuit, inverter and energy storage system thereof - Google Patents

Abstract

The embodiment of the invention discloses a level conversion circuit, an inverter and an energy storage system thereof. The level conversion circuit includes: the N direct current sides are connected with the controlled driving units of the direct current side voltage sources, and the controlled driving units are configured to respond to the direct current side voltage and correspondingly output first voltage, second voltage or third voltage under the control of the control unit; the N voltage ratios are in equal proportion increasing trend; the alternating current side of the controlled driving unit is connected with the primary side of the corresponding transformer, the secondary sides of the N transformers are connected in series and then output a modulating voltage with 3Nn levels, and the modulating voltage is equivalent to the alternating current voltage under the control of the control unit; the ratio of the voltages of the N transformers is equal to N. By combining the control unit and the mixed cascade modulation, the embodiment of the invention can reduce the temperature rise of the switching tubes under the condition of the same number of switching tubes and avoid the reliability problem caused by the parallel connection of the switching tubes.

Description

A level conversion circuit, inverter and energy storage system thereof

technical field

The embodiments of the present invention relate to the field of inverters, and in particular to a level conversion circuit, an inverter and an energy storage system thereof.

Background technique

Generally, traditional high-voltage grid-connected inverters use full-bridge or half-bridge inverters for charging and discharging. When the power is too high, considering the problems caused by traditional IGBT technology and temperature rise, it is necessary to use multiple tubes in parallel or use IGBTs in combination. The power expansion of the module structure brings many challenges to the actual LAYOUT layout and software control.

The invention provides the possibility of stable and reliable development of renewable energy power generation in the large power range by combining the hybrid cascaded inverter mode and CPLD control; the hybrid cascaded level modulation technology is used to realize the grid-connected converter's high voltage and large The pursuit of power, high power quality, and low cost.

Contents of the invention

In order to solve the above technical problems, a technical solution adopted by the embodiment of the present invention is to provide a level conversion circuit, including: N controlled drive units connected to the DC side and the DC side voltage source, and the controlled drive units are configured in In response to the DC side voltage, the first voltage, the second voltage or the third voltage is correspondingly output under the control of the control unit; N transformers and the control unit, the voltage ratio of the N transformers is proportionally increasing; controlled drive The AC side of the unit is connected to the primary side of the corresponding transformer, and the secondary sides of the N transformers are connected in series to output a modulation voltage with 3Nn levels. Under the control of the control unit, the modulation voltage is equivalent to an AC voltage; N transformers The proportional ratio between the voltage ratios is n, the first voltage is the inverse value of the third voltage, and the second voltage is 0.

In some embodiments, the controlled drive unit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube, wherein the controlled end of the first switch tube and the controlled end of the second switch tube , the controlled terminal of the third switching tube and the controlled terminal of the fourth switching tube are connected to the control unit; the first terminal of the first switching tube is connected to the positive pole of the DC side voltage source, and the second terminal of the first switching tube is connected to the second terminal of the first switching tube. The first end of the second switch tube and the first end of the primary side of the corresponding transformer, the second end of the second switch tube is connected to the negative pole of the DC side voltage source; the first end of the third switch tube is connected to the first end of the first switch tube terminal, the second terminal of the third switching tube is connected to the first terminal of the fourth switching tube and the second terminal of the primary side of the corresponding transformer, and the second terminal of the fourth switching tube is connected to the negative pole of the DC side voltage source.

In some embodiments, types of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube include IGBT tubes, MOS tubes and triodes.

In some embodiments, the control unit is a complex programmable logic device.

In some embodiments, the geometric ratio is 3.

In order to solve the above-mentioned technical problems, another technical solution adopted by the embodiments of the present invention is to provide an inverter, including the above-mentioned level conversion circuit.

In order to solve the above technical problems, another technical solution adopted by the embodiment of the present invention is to provide an energy storage system, including: a photovoltaic module power generation module, a battery module energy storage module, a bus capacitor module and the above inverter, wherein, The battery component energy storage module is used to store electric energy and provide DC side voltage to the bus capacitor module; the photovoltaic module power generation module is used to convert solar energy into electrical energy and provide DC side voltage to the bus capacitor module; the bus capacitor module is used to filter the DC side voltage and output to the inverter; the inverter responds to the DC side voltage and outputs the modulated voltage to the power grid and the load.

In some embodiments, the battery assembly energy storage module includes N energy storage batteries and N bidirectional DC/DC conversion devices, wherein one side of the N bidirectional DC/DC conversion devices is connected to both ends of the bus capacitor module, The other sides of the N bidirectional DC/DC conversion devices are connected to corresponding energy storage batteries.

In some embodiments, the photovoltaic component power generation module includes N photovoltaic power generation components and N DC/DC conversion devices, wherein the output sides of the N DC/DC conversion devices are connected to both ends of the bus capacitor module, and the N DC The input side of the /DC converting device is connected to corresponding photovoltaic power generation components.

In some embodiments, the bus capacitor module includes several electrolytic capacitors connected in series and parallel, and film capacitors connected in parallel with the several electrolytic capacitors connected in series and parallel.

The beneficial effect of the embodiment of the present invention is: different from the situation of the prior art, the embodiment of the present invention combines the control unit and the level conversion circuit that modulates the AC voltage in hybrid cascade, and can under the condition of the same number of switching tubes, Reduce the temperature rise of the switch tube, avoid the reliability problems caused by the parallel connection of the switch tube, realize the pursuit of high voltage, high power, high power quality, and low cost of the grid-connected converter, and can also adapt to the needs of different power segments; in addition , in the case of high-power applications, it can reduce the amount of software calculation and LAYOUT layout workload.

Description of drawings

FIG. 1 is a schematic structural diagram of a level conversion circuit provided in an embodiment of the present invention;

Fig. 2 is a circuit structure diagram of a controlled driving unit provided in an embodiment of the present invention;

Fig. 3 is a circuit structure diagram of a level conversion circuit provided by an embodiment of the present invention;

Fig. 4 is a schematic structural diagram of an energy storage system provided by an embodiment of the present invention;

Fig. 5 is a schematic structural view of a battery pack energy storage module provided by an embodiment of the present invention;

Fig. 6 is a schematic structural diagram of a photovoltaic module power generation module provided by an embodiment of the present invention;

Fig. 7 is a circuit structure diagram of an energy storage system provided in an embodiment of the present invention.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is said to be "fixed" to another element, it may be directly on the other element, or there may be one or more intervening elements therebetween. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", and "bottom" used in this specification is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the The application and simplified description do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as limiting the application. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the technical field of this application. The terms used in the description of the present application are only for the purpose of describing specific embodiments, and are not used to limit the present application. The term "and/or" used in this specification includes any and all combinations of one or more of the associated listed items.

In addition, the technical features involved in different embodiments of the present application described below may be combined with each other as long as they do not constitute a conflict with each other.

In some embodiments of the present application, a level conversion circuit is provided, the structural diagram of which is shown in FIG. 1 , the level conversion circuit includes N controlled driving units 200 , N transformers and a control unit 100 .

Wherein, the signal output terminals of the control unit 100 are respectively connected to the controlled terminals of the N controlled driving units 200, and the N controlled driving units 200 are all connected to the DC side voltage source, and the controlled driving unit 200 is powered by the DC voltage source The controlled driving unit 200 is configured to output the first voltage, the second voltage or the third voltage under the control of the control unit 100 in response to the DC side voltage. That is, under the supply of the DC side voltage, in response to different control signals output by the control unit 100 , the first voltage, the second voltage or the third voltage is correspondingly output.

The N transformers include transformer T1 , transformer T2 , . In this embodiment, the proportional ratio between the voltage ratios of the transformers is set to be n.

The voltage ratio is the turns ratio of the transformer, that is, the turns ratio of the primary coil and the secondary coil, and is generally called the transformation ratio of the transformer. It reflects the ratio of the effective value of the primary and secondary coil voltages of the transformer. When the no-load current can be ignored, the effective value of the primary and secondary coil currents is inversely proportional to the number of turns. The transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. Its main components are primary coil, secondary coil and iron core.

For example, the voltage ratio of transformer T1 is 1:M, then the voltage ratio of transformer T2 is 1:nM, the voltage ratio of transformer T3 is 1:n ² M,..., the voltage ratio of transformer TN is 1:n ^N-1 M .

The AC side of the controlled drive unit is connected to the primary side of the corresponding transformer, and the secondary sides of the N transformers are connected in series to output a modulation voltage with 3Nn levels. Since the output levels of the transformers include the first voltage, the second voltage and the third voltage, the number of levels of the modulation voltage is equal to 3*the number of transformers N*the proportional ratio n.

In this embodiment, the first voltage is an inverse value of the third voltage, and the second voltage is zero.

Since the secondary sides of the transformers are connected in series, the modulation voltage is the sum of the output voltages of each transformer. Under the control of the control unit 100, the modulation voltage is equivalent to an AC voltage. For example, the control unit 100 controls each controlled driving unit 200 according to time sequence, assuming that the first voltage V1 is positive and the third voltage V3 is negative, so that each controlled driving unit 200 outputs the first voltage V1 at the first moment, and at the Under the action of the corresponding transformer of the controlled driving unit 200, for example, the output voltage of the transformer T1 is V1*M, the output voltage of the transformer T2 is V1*3*M, and the output voltage of the transformer T2 is V1*3 ² *M ,..., the voltage output by the transformer TN is V1*3 ^N-1 *M, so the total output voltage at the first moment, that is, the modulation voltage VT1 at the first moment is V1*(1+3+3 ² +… ...+3 ^N-1 )*M.

At the second moment, the control unit 100 controls the controlled driving unit 200 connected to the transformer T1 to output the second voltage, and the remaining controlled driving units 200 still output the first voltage V1. Since the second voltage is 0, the second The modulation voltage VT2 at the moment is V1*(3+3 ² +...+3 ^N-1 )*M, which is one V1 lower than the modulation voltage VT1 at the first moment.

At the third moment, the control unit 100 controls the controlled driving unit 200 connected to the transformer T1 to output the third voltage V3, and the remaining controlled driving units 200 still output the first voltage V1, because the third voltage V3 is the first voltage The opposite number of V1, so the modulation voltage VT3 at the third moment is V1*(3+3 ² +...+3 ^N-1 -1)*M, which is one V1 lower than the modulation voltage VT2 at the second moment . It is not difficult to see that, under the timing control of the control unit 100, the level conversion circuit can make the waveform of the output modulation voltage a sine wave, that is, make the modulation signal equivalent to an AC signal.

In some embodiments of the present application, a controlled drive unit 200 is provided, the controlled drive unit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, wherein the first switch The controlled end of the transistor, the controlled end of the second switching transistor, the controlled end of the third switching transistor and the controlled end of the fourth switching transistor are all connected to the control unit 100 .

The first end of the first switch tube is connected to the positive pole of the DC side voltage source, the second end of the first switch tube is connected to the first end of the second switch tube and the first end of the primary side of the corresponding transformer, and the second end of the second switch tube is connected to the first end of the primary side of the corresponding transformer. The two terminals are connected to the negative pole of the DC side voltage source.

The first end of the third switching tube is connected to the first end of the first switching tube, the second end of the third switching tube is connected to the first end of the fourth switching tube and the second end of the corresponding primary side of the transformer, and the fourth switching tube The second terminal is connected to the negative pole of the DC side voltage source.

The first switch tube, the second switch tube, the third switch tube and the fourth switch tube form an H-bridge circuit. The H-bridge is an electronic circuit that can reverse the voltage/current of the connected load or the output terminal. Towards. The H-bridge is a typical DC motor control circuit, which can be built in the form of discrete components or integrated into an integrated circuit. The name "H bridge" originates from its circuit, two parallel branches and a load access/circuit output branch, which seem to form a circuit structure shaped like the letter "H".

It should be noted that types of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube include IGBT tubes, MOS tubes and triodes.

In some embodiments of the present application, a controlled drive unit 200 constructed with IGBT tubes is provided, the circuit structure diagram of which is shown in FIG. 2 , the controlled drive unit 200 includes a first IGBT tube Q1, a second IGBT tube Tube Q2, third IGBT tube Q3 and fourth IGBT tube Q4, wherein the base of the first IGBT tube Q1, the base of the second IGBT tube Q2, the base of the third IGBT tube Q3 and the base of the fourth IGBT tube Q4 Both bases are connected to the control unit 100 .

The collector of the first IGBT tube Q1 is connected to the positive pole of the DC side voltage source, the emitter of the first IGBT tube Q1 is connected to the collector of the second IGBT tube Q2 and the first end of the primary side of the corresponding transformer, and the second IGBT tube Q2 The emitter is connected to the negative pole of the DC side voltage source.

The collector of the third IGBT tube Q3 is connected to the collector of the first IGBT tube Q1, the emitter of the third IGBT tube Q3 is connected to the collector of the fourth IGBT tube Q4 and the second end of the primary side of the corresponding transformer, and the fourth IGBT tube The emitter of Q4 is connected to the negative pole of the DC side voltage source.

Based on the above-mentioned controlled driving unit 200 , an embodiment of the present invention provides a level conversion circuit, the circuit structure diagram of which is shown in FIG. 3 . The level conversion circuit includes a control unit 100 , a transformer T1 , a transformer T2 , a transformer T3 and a corresponding controlled driving unit 200 . The circuit structure of the controlled driving unit 200 has been described in the above embodiments and will not be repeated here.

The collectors of the first IGBT transistor Q1 of each controlled driving unit 200 are connected to the positive pole of the DC voltage source, and the emitters of the second IGBT transistor Q2 are connected to the negative pole of the DC voltage source to introduce the DC voltage Udc. The first terminal of the secondary side of the transformer T1 is used as the output terminal of the modulation voltage Vout, the second terminal of the secondary side of the transformer T1 is connected to the first terminal of the secondary side of the transformer T2, and the second terminal of the secondary side of the transformer T2 is connected to the terminal of the transformer T3 The first terminal of the secondary side, the second terminal of the secondary side of the transformer T3 is grounded.

In the embodiment of the present invention, the proportional ratio between the voltage ratios of the transformers is 3, that is, if the voltage ratio of the transformer T1 is 1:M, the voltage ratio of the transformer T2 is 1:3M, and the voltage ratio of the transformer T3 is 1 : 9M.

The signal output terminals of the control unit 100 are respectively connected to the base of the first IGBT transistor Q1, the base of the second IGBT transistor Q2, the base of the third IGBT transistor Q3 and the base of the fourth IGBT transistor Q4 of each controlled driving unit 200. base.

In the embodiment of the present invention, the control unit 100 is a complex programmable logic device (Complex ProgrammableLogic Device, CPLD). CPLD is a device developed from PAL and GAL devices. It is relatively large in scale and complex in structure, and belongs to large-scale range of integrated circuits. It is suitable for control-intensive digital digital system design, and its delay control is convenient. It is one of the fastest-growing devices in integrated circuits. It adopts CMOS EPROM, EEPROM, flash memory and SRAM and other programming technologies to form a high-density, high-speed and low-power programmable logic device, mainly composed of logic array blocks, macro cells, extended product items, programmable connection The line array and the I/O control block consist of five parts.

It should be noted that this embodiment uses three transformers and corresponding controlled driving units as examples for illustration, but in practical applications, transformers and corresponding controlled driving units can be increased or decreased according to requirements. It should be emphasized that the minimum number of transformers and corresponding controlled drive units is two.

The beneficial effect of the embodiment of the present invention is: different from the situation of the prior art, the embodiment of the present invention combines the control unit and the level conversion circuit that modulates the AC voltage in hybrid cascade, and can under the condition of the same number of switching tubes, Reduce the temperature rise of the switching tubes and avoid the reliability problems caused by the parallel connection of the switching tubes.

Based on the above-mentioned level conversion circuit, an embodiment of the present invention provides an inverter, and the inverter includes the level conversion circuit as described in the above-mentioned embodiments.

Based on the above-mentioned inverter, an embodiment of the present invention provides an energy storage system, the structural diagram of which is shown in FIG. And the inverter 10 as above.

Among them, the battery component energy storage module 40 is connected to the bus capacitor module 20, the battery component energy storage module 40 is used to store electric energy and provide the DC side voltage to the bus capacitor module 20, the battery component energy storage module 40 realizes energy peak shaving and valley filling (Peak Cut). Peak shaving and valley filling is a measure to adjust electricity load. Arrange and organize the power consumption time of various users in a reasonable and planned manner according to the power consumption rules of different users. To reduce load peaks and fill load troughs. Reduce the peak-to-valley load difference of the power grid, so that the power generation and power consumption tend to be balanced.

The photovoltaic module power generation module 30 is connected to the bus capacitor module 20, and the photovoltaic module power generation module 30 is used to convert solar energy into electric energy and provide a DC side voltage to the bus capacitor module 20; the photovoltaic module power generation module 30 includes multiple MPPT output DC/DC The conversion device realizes the maximum power point tracking of photovoltaic power generation components and the energy supply of the system.

Maximum Power Point Tracking (MPPT for short) is a core technology in the photovoltaic power generation system. Output maximum power.

The bus capacitor module 20 is connected to the inverter 10, and the bus capacitor module 20 is used to filter the DC side voltage and output it to the inverter; the bus capacitor module 20 includes several electrolytic capacitors connected in series and parallel, and several electrolytic capacitors connected in series and parallel A film capacitor connected in parallel with an electrolytic capacitor. The bus capacitor module 20 is used to realize bus voltage support and power decoupling of AC voltage and DC voltage.

The inverter 10 is connected to the grid 60 and the load 70 , and the inverter 10 outputs a modulated voltage to the grid 60 and the load 70 in response to the DC side voltage.

In some embodiments of the present invention, a battery assembly energy storage module 40 is provided, the structural diagram of which is shown in FIG. 5 , the battery assembly energy storage module 40 includes N energy storage batteries 410 and N bidirectional DC/DC Transformation means 420 .

Wherein, one side of the N bidirectional DC/DC conversion devices 420 is connected to both ends of the bus capacitor module 20, and the positive port of one side of the bidirectional DC/DC conversion device 420 is connected to the positive pole of the bus capacitor module 20, and the bidirectional DC/DC The negative terminal on one side of the DC conversion device 420 is connected to the negative pole of the bus capacitor module 20; the other side of the N bidirectional DC/DC conversion devices 420 is connected to the corresponding energy storage battery 410, and the other side of the bidirectional DC/DC conversion device 420 The positive terminal on one side is connected to the positive terminal of the corresponding energy storage battery 410 , and the negative terminal on the other side of the bidirectional DC/DC conversion device 420 is connected to the negative terminal of the corresponding energy storage battery 410 .

In some embodiments of the present invention, a photovoltaic module power generation module 30 is provided, the structural diagram of which is shown in FIG. 6 , the photovoltaic module power generation module 30 includes N photovoltaic power generation modules 310 and N DC/DC conversion devices 320 .

Wherein, the output sides of the N DC/DC conversion devices 320 are all connected to both ends of the bus capacitor module 20, and the positive port of one side of the DC/DC conversion device 320 is connected to the positive pole of the bus capacitor module 20, and the DC/DC conversion device The negative terminal on one side of 320 is connected to the negative terminal of the bus capacitor module 20; the input side of the N DC/DC conversion devices 320 is connected to the corresponding photovoltaic power generation module 310, and the positive terminal on the other side of the DC/DC conversion device 320 is connected to To the positive pole of the corresponding photovoltaic power generation component 310 , the negative terminal on the other side of the DC/DC conversion device 320 is connected to the negative pole of the corresponding photovoltaic power generation component 310 .

The DC/DC conversion device 320 in this embodiment is a DC/DC conversion device that includes an MPPT device. The MPPT device continuously detects the current and voltage changes of the photovoltaic power generation module 310, and according to the change, the PWM drive signal of the DC/DC converter The duty cycle is adjusted.

Based on the above-mentioned photovoltaic module power generation module 30 and battery module energy storage module 40, the embodiment of the present invention provides an energy storage system, its circuit structure diagram is shown in Figure 7, in this embodiment, the bus capacitor module 20 includes Several electrolytic capacitors connected in series and parallel, and film capacitors connected in parallel with several electrolytic capacitors connected in series and parallel are equivalent to capacitor C1. The energy storage system includes a control unit 100, a transformer T1, a transformer T2, a transformer T3, and three receiving Control drive unit 200, capacitor C1, 3 photovoltaic power generation modules 310, 3 DC/DC conversion devices 320, 3 energy storage batteries 410 and 3 bidirectional DC/DC conversion devices 420.

In this embodiment, the transformer T1, the transformer T2 and the transformer T3 are all low-voltage transformers.

Among them, the positive ports on one side of the three bidirectional DC/DC converting devices 420 are all connected to the positive pole of the capacitor C1, and the negative ports on one side of the three bidirectional DC/DC converting devices 420 are all connected to the negative pole of the capacitor C1; The positive terminal on the other side of the bidirectional DC/DC conversion device 420 is connected to the positive terminal of the corresponding energy storage battery 410, and the negative terminals on the other side of the three bidirectional DC/DC conversion devices 420 are connected to the corresponding positive terminal of the energy storage battery 410. negative electrode.

The positive terminals on one side of the three DC/DC conversion devices 320 are all connected to the positive terminal of the capacitor C1, and the negative terminals on one side of the three DC/DC conversion devices 320 are all connected to the negative terminal of the capacitor C1; the three DC/DC conversion The positive terminal on the other side of the device 320 is connected to the positive terminal of the corresponding photovoltaic power generation module 310 , and the negative terminals on the other side of the three DC/DC conversion devices 320 are connected to the negative terminal of the corresponding photovoltaic power generation module 310 .

The signal output terminals of the control unit 100 are respectively connected to the base of the first IGBT transistor Q1, the base of the second IGBT transistor Q2, the base of the third IGBT transistor Q3 and the base of the fourth IGBT transistor Q4 of each controlled driving unit 200. base.

The collectors of the first IGBT transistor Q1 of each controlled driving unit 200 are connected to the positive pole of the capacitor C1, and the emitters of the second IGBT transistor Q2 are connected to the negative pole of the capacitor C1 to introduce the DC side voltage Udc.

The primary side of the transformer T1, the primary side of the transformer T2 and the primary side of the transformer T3 are connected to the corresponding controlled driving unit 200, and the first terminal of the secondary side of the transformer T1 is connected to the grid 60 and the load 70 as the output terminal of the modulation voltage Vout , the second end of the secondary side of the transformer T1 is connected to the first end of the secondary side of the transformer T2, the second end of the secondary side of the transformer T2 is connected to the first end of the secondary side of the transformer T3, and the second end of the secondary side of the transformer T3 grounded.

In this example, in the implementation of the present invention, the proportional ratio between the voltage ratios of the transformers is 3, that is, if the voltage ratio of the transformer T1 is 1:2, then the voltage ratio of the transformer T2 is 1:3*2 , the voltage ratio of transformer T3 is 1:9*2.

In the above-mentioned embodiment, it can be seen that the level conversion circuit composed of the control unit 100, the transformer T1, the transformer T2, the transformer T3, and the three controlled driving units 200 can output 3Nn kinds of levels, that is, 3*3*3, 27 kinds level. Assuming that the voltage of the actual power grid 60 is 800V, the secondary side of the transformer T1 can correspondingly generate three levels of 84V, 0, and -84V, and the first voltage output by the controlled driving unit 200 is 42V, the second voltage is 0, and the third voltage is 0. The voltage is -42V. Therefore, the secondary side of the transformer T2 can generate three levels of 252V, 0, and -252V, and the secondary side of the transformer T3 can generate three levels of 756V, 0, and -756V. Therefore, the peak-to-peak value of the modulation voltage is 1092V, so that the modulation voltage The waveform is close to the sine wave with an effective voltage value of 800V, so as to obtain the output voltage waveform of the corresponding controlled drive unit 200, and further deduce the switching sequence of the four IGBT tubes in each controlled drive unit 200, so as to achieve the control effect.

It should be noted that the number of energy storage batteries, DC/DC conversion devices, photovoltaic power generation components, bidirectional DC/DC conversion devices, transformers and corresponding controlled drive units can be increased or decreased according to actual applications, and this embodiment is only an example. , the number of energy storage batteries, DC/DC conversion devices, photovoltaic power generation components, bidirectional DC/DC conversion devices, transformers and corresponding controlled drive units is not limited.

Different from the prior art, the embodiment of the present invention can reduce the temperature rise of the switching tubes under the condition of the same number of switching tubes by combining the control unit and the level conversion circuit that modulates the AC voltage in hybrid cascade, and avoids the switching tubes from being damaged due to The reliability problem brought by parallel connection realizes the pursuit of high voltage, high power, high power quality, and low cost of grid-connected converters, and can also adapt to the needs of different power segments; in addition, in high-power applications, it can reduce software The amount of calculation and the workload of LAYOUT layout.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; under the thinking of the present application, the above embodiments or technical features in different embodiments can also be combined, The steps can be performed in any order, and there are many other variations of the different aspects of the application as above, which are not presented in detail for the sake of brevity; although the application has been described in detail with reference to the preceding examples, those of ordinary skill in the art It should be understood that it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technology of each embodiment of the application. scope of the program.

Claims (10)

1. A level conversion circuit, characterized in that, comprising: N controlled drive units connected to the DC side voltage source, the controlled drive units are configured to output the first voltage, the second voltage or the third voltage under the control of the control unit in response to the DC side voltage ; N transformers and a control unit, the voltage ratios of the N transformers are in an increasing trend proportionally; The AC side of the controlled drive unit is connected to the primary side of the corresponding transformer, and the secondary sides of the N transformers are connected in series to output a modulation voltage with 3Nn levels. Under the control of the control unit, the Modulation voltage is equivalent to AC voltage; The proportional ratio among the voltage ratios of the N transformers is n, the first voltage is an inverse value of the third voltage, and the second voltage is 0. 2. The circuit according to claim 1, wherein the controlled driving unit comprises a first switching tube, a second switching tube, a third switching tube and a fourth switching tube, wherein, The controlled terminal of the first switch tube, the controlled terminal of the second switch tube, the controlled terminal of the third switch tube and the controlled terminal of the fourth switch tube are all connected to the control unit ; The first terminal of the first switching tube is connected to the positive pole of the DC side voltage source, and the second terminal of the first switching tube is connected to the first terminal of the second switching tube and the first terminal of the primary side of the corresponding transformer. end, the second end of the second switching tube is connected to the negative pole of the DC side voltage source; The first end of the third switching tube is connected to the first end of the first switching tube, and the second end of the third switching tube is connected to the first end of the fourth switching tube and the primary side of the corresponding transformer. The second end, the second end of the fourth switch tube is connected to the negative pole of the DC side voltage source. 3. The circuit according to claim 2, wherein the types of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube include IGBT tube, MOS tube and triode. 4. The circuit according to claim 1, wherein the control unit is a complex programmable logic device. 5. The circuit according to any one of claims 1-4, wherein the geometrical ratio is 3. 6. An inverter, characterized in that, comprising: The level conversion circuit according to any one of claims 1-5. 7. An energy storage system, characterized in that it comprises: a photovoltaic module power generation module, a battery module energy storage module, a bus capacitor module and the inverter as claimed in claim 6, wherein, The battery pack energy storage module is used to store electric energy and provide DC side voltage to the bus capacitor module; The photovoltaic module power generation module is used to convert solar energy into electrical energy and provide DC side voltage to the bus capacitor module; The bus capacitor is used to filter the DC side voltage and output it to the inverter; The inverter outputs a modulated voltage to the grid and the load in response to the DC side voltage. 8. The energy storage system according to claim 7, wherein the battery assembly energy storage module includes N energy storage batteries and N bidirectional DC/DC conversion devices, wherein, One side of the N bidirectional DC/DC conversion devices is connected to both ends of the bus capacitor module, and the other side of the N bidirectional DC/DC conversion devices is connected to a corresponding energy storage battery. 9. The energy storage system according to claim 7, wherein the photovoltaic module power generation module includes N photovoltaic power generation modules and N DC/DC conversion devices, wherein, The output sides of the N DC/DC conversion devices are all connected to both ends of the bus capacitor module, and the input sides of the N DC/DC conversion devices are connected to corresponding photovoltaic power generation components. 10. The energy storage system according to any one of claims 7-9, characterized in that the bus capacitor module includes several electrolytic capacitors connected in series and parallel, and film capacitors connected in parallel with the several electrolytic capacitors connected in series and parallel .