A double-terminal three-level energy storage converter

Abstract

The present invention relates to a double-terminal three-level energy storage converter, which belongs to the field of power electronics technology and solves the problems in the prior art that the power frequency transformer is large in size and weight, high in cost, has large electromagnetic interference and energy loss, and is not suitable for occasions with high power density requirements. The double-terminal three-level energy storage converter includes: a DC end; a dual-path full-bridge isolation circuit connected between the DC end and the T-type inverter circuit, which is used to perform pulse width modulation control based on the first drive signal output by the drive circuit to realize DCDC conversion; a T-type inverter circuit, which is used to output / input AC voltage signals, wherein the T-type inverter circuit is also used to realize the switching of three working modes of output / input AC voltage based on the second drive signal output by the drive circuit; a control circuit and a drive circuit. A light, high-efficiency, high-power-density and low-system-loss double-terminal three-level energy storage converter is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a double-terminal three-level energy storage converter. Background Art

[0002] The energy storage inverter is a bidirectional energy conversion device that connects the DC bus and the AC bus. It is an important component of the multi-energy microgrid and can be widely used in photovoltaic power generation, wind power generation, multi-energy power supply systems, microgrids and other fields.

[0003] The power supply system connects the DC bus and the AC bus through a bidirectional energy storage inverter, and networks photovoltaic power generation, wind power generation, new energy batteries with traditional power supply equipment such as the municipal power grid and diesel generator sets to achieve two-way flow of energy. It has the capabilities of free access to electricity, hot backup of multiple power supplies, automatic energy conversion and efficient regulation and scheduling. It can be applied to diversified electricity demands in different environments and under different mission conditions, and improves the reliability, stability and economy of the power supply system.

[0004] Traditional energy storage converters often use power frequency transformers for isolation and voltage boosting at the grid end. Power frequency transformers are large in size and weight, high in cost, and have large electromagnetic interference and energy losses, making them unsuitable for applications with high power density requirements. In summary, there is an urgent need for a lightweight, high-efficiency, high-power-density, and low-system-loss energy storage converter. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a double-terminal three-level energy storage converter to solve the problems of existing power frequency transformers being large in size and weight, high in cost, having large electromagnetic interference and energy loss, and being unsuitable for applications requiring high power density.

[0006] On the one hand, an embodiment of the present invention provides a double-ended three-level energy storage converter, comprising:

[0007] The DC terminal is used to input / output DC voltage, and a capacitor C1 is connected in parallel between the positive and negative terminals of the DC terminal;

[0008] A dual-path full-bridge isolation circuit is connected between the DC terminal and the T-type inverter circuit, and is used to perform pulse width modulation control based on the first drive signal output by the drive circuit to achieve DCDC conversion;

[0009] A T-type inverter circuit, used for outputting / inputting an AC voltage signal, wherein the T-type inverter circuit is also used for switching between three working modes of outputting / inputting an AC voltage based on a second driving signal output by the driving circuit;

[0010] A control circuit, used for sampling the voltage / current in the energy storage converter circuit, and obtaining a control circuit control signal based on the sampling information;

[0011] The driving circuit is used to generate the first driving signal and the second driving signal based on the control circuit control signal.

[0012] Furthermore, the sampling information includes the DC input / output DC voltage and current of the DC end, the voltage and current values ​​of the high-voltage bus and the low-voltage bus in the dual-bridge isolation circuit, and the voltage and current values ​​of the two ends of the AC end of the T-type inverter circuit; the control circuit adjusts the switching voltage U according to the sampling information G ;

[0013] The control circuit compares the switching voltage U G A control signal for the T-type inverter circuit is generated according to the voltage and current values ​​of the high-voltage bus and the low-voltage bus in the dual full-bridge isolation circuit, and the drive circuit generates the second drive signal based on the T-type inverter circuit control signal.

[0014] Furthermore, the dual-path full-bridge isolation circuit includes switch tubes S3 to S10, a high-frequency transformer T1 and capacitors C3 to C5;

[0015] The collector of the switch tube S3 and the emitter of the switch tube S4 are connected to the positive and negative ends of the DC end respectively;

[0016] The emitter of the switch tube S3 is connected to the collector of the switch tube S4, and the emitter of the switch tube S5 is connected to the collector of the switch tube S6, wherein the collector of the switch tube S4 and the collector of the switch tube S6 are respectively connected to the primary side of the high-frequency transformer T1;

[0017] The emitter of the switch tube S7 is connected to the collector of the switch tube S8, and the collector of the switch tube S8 is connected to one end of the secondary side of the high-frequency transformer T1;

[0018] The emitter of the switch tube S9 is connected to the collector of the switch tube S10, and the collector of the switch tube S10 is connected to the other end of the secondary side of the high-frequency transformer T1 through the capacitor C3;

[0019] The collector of the switch tube S7 and the emitter of the switch tube S8 are connected to the anode and cathode of the capacitor C5 respectively;

[0020] The collector of the switch tube S9 and the emitter of the switch tube S10 are connected to the anode and cathode of the capacitor C4 respectively;

[0021] The cathodes of the capacitor C4 and the capacitor C5 are connected to each other, and serve as a common negative terminal of the dual-path full-bridge isolation circuit;

[0022] The switch tubes S3 to S10 are turned on and off based on the first driving signal;

[0023] The anode of the capacitor C5 is the positive terminal of the high-voltage bus of the dual-path full-bridge isolation circuit;

[0024] The anode of the capacitor C4 is the positive terminal of the low-voltage busbar of the dual-path full-bridge isolation circuit.

[0025] Furthermore, the three working modes include a low-voltage single-ended power supply mode, a double-ended power supply mode, and a high-voltage single-ended power supply mode;

[0026] When the output / input AC voltage is lower than U L At the same time, it is lower than U G , switching to the low-voltage single-ended power supply mode;

[0027] When the output / input AC voltage is lower than U L At the same time, it is lower than U G , switching to the dual-end power supply mode;

[0028] When the output / input AC voltage is higher than U G , switching to the high-voltage single-ended power supply mode;

[0029] Among them, the U L is the positive terminal voltage of the low voltage bus, U H It is the voltage value of the positive terminal of the high voltage bus.

[0030] Furthermore, when the energy storage converter is in the inverter state, the U G The control method is as follows:

[0031]

[0032] Among them, U G is the switching voltage, U Gp is the output voltage amplitude of the AC end of the energy storage converter, U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, s is the Laplace operator;

[0033] When the energy storage converter is in the rectifying state, the U G The control method is as follows:

[0034]

[0035] Among them, U G is the switching voltage, U Gpis the input voltage amplitude of the AC end of the energy storage converter, U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, and s is the Laplace operator.

[0036] Furthermore, the T-type inverter circuit includes switch tubes S11 to S18, a capacitor C6, an inductor L2,

[0037] The emitter of the switch tube S15 is connected to the emitter of the switch tube S17 and is connected to the positive end of the low-voltage bus of the dual-path full-bridge isolation circuit;

[0038] The collector of the switch tube S15 is connected to the collector of the switch tube S16, and the collector of the switch tube S17 is connected to the collector of the switch tube S18;

[0039] The emitter of the switch tube S11 is connected to the collector of the switch tube S12, wherein the collector of the switch tube S12 is connected to the emitter of the switch tube S16 and to one end of the inductor L2;

[0040] The collector of the switch tube S11 is connected to the positive terminal of the high-voltage bus of the dual-path full-bridge isolation circuit;

[0041] The other end of the inductor L2 is connected to one end of the capacitor C6;

[0042] The emitter of the switch tube S13 is connected to the collector of the switch tube S14, wherein the collector of the switch tube S14 is connected to the emitter of the switch tube S18 and the other end of the capacitor C6;

[0043] The two ends of the capacitor C6 are the output / input AC voltage signal ends;

[0044] The switch tubes S11 - S18 are turned on and off based on the second driving signal.

[0045] Furthermore, the double-terminal three-level energy storage converter further includes a Buck-Boost circuit, the Buck-Boost circuit includes the capacitor C1, and the dual-path full-bridge isolation circuit is connected to the DC end via the Buck-Boost circuit.

[0046] Furthermore, the Buck-Boost circuit includes a capacitor C1, a capacitor C2, an inductor L1, a switch tube S1 and a switch tube S2;

[0047] The anode of the capacitor C1 is connected to the positive end of the DC terminal and one end of the inductor L1; wherein the cathode of the capacitor C1 is connected to the negative end of the DC terminal;

[0048] The emitter of the switch tube S1 is connected to the collector of the switch tube S2, and the collector of the switch tube S2 is connected to the other end of the inductor L1;

[0049] The emitter of the switch tube S2 is connected to the negative terminal of the DC terminal;

[0050] The anode and cathode of the capacitor C2 are respectively connected to the collector of the switch tube S1 and the emitter of the switch tube S2, and serve as two connection terminals with the T-type inverter circuit;

[0051] The driving circuit further generates the third driving signal based on the control circuit control signal; the third driving signal is used to control the switching on and off of the switch tube S1 and the switch tube S2.

[0052] Furthermore, a DC voltage is input at the DC end, the energy storage converter operates in an inverter state, and the T-type inverter circuit outputs an AC voltage signal; the Buck-Boost circuit operates in a Boost state, and under the drive of a cycle drive signal of the third drive signal, the switch tube S2 is first turned on, and the current flows through the capacitor C1, the inductor L1, and the switch tube S2; the switch tube S2 is then turned off, and the current flows through the capacitor C1, the inductor L1, the switch tube S1, and the capacitor C2.

[0053] Furthermore, an AC voltage signal is input into the T-type inverter circuit, the energy storage converter operates in a rectification state, and a DC voltage is output at the DC end; the Buck-Boost circuit operates in a Buck state, and under the drive of a cycle drive signal of the third drive signal, the switch tube S1 is first turned on, and the current flows through the capacitor C2, the inductor L1, and the capacitor C1; the switch tube S1 is then turned off, and the current flows through the inductor L1, the capacitor C1, and the switch tube S2.

[0054] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0055] 1. The traditional energy storage converter circuit topology has been improved. The dual-path full-bridge isolation circuit has been adjusted to a dual-port, and combined with a T-type three-level inverter circuit, the switching loss of each switch tube has been effectively reduced, the AC harmonic voltage and current have been reduced, the grid-side waveform quality has been improved, and the performance of the energy storage converter has been greatly improved.

[0056] 2. According to the output voltage, the T-type inverter circuit is divided into three working modes, namely, low-voltage single-ended power supply mode, double-ended power supply mode, and high-voltage single-ended power supply mode. H , U L, U G Different working modes are allocated according to the relationship between the capacitor and the voltage, which makes full use of the capacitor voltage, reduces switching losses, and greatly improves the working efficiency of the energy storage converter.

[0057] 3. The T-type inverter circuit uses a high-frequency transformer, which greatly reduces the volume and weight of the energy storage converter.

[0058] 4. By adjusting the switching voltage U G , for U H , U L A closed-loop control is performed so that the dual full-bridge isolation circuit can adopt a simple open-loop control to always operate at the resonant frequency point, keep the gain fixed and optimize the efficiency.

[0059] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0061] Figure 1 Schematic diagram of a double-ended three-level energy storage converter in one embodiment of the present application. DETAILED DESCRIPTION

[0062] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0063] A specific embodiment of the present invention discloses a double-terminal three-level energy storage converter, such as Figure 1As shown, a double-terminal three-level energy storage converter includes: a DC terminal, which is used to input / output a DC voltage, and a capacitor C1 is connected in parallel between the positive and negative terminals of the DC terminal; a dual-path full-bridge isolation circuit, which is connected between the DC terminal and the T-type inverter circuit, and is used to perform pulse width modulation control based on a first drive signal output by a drive circuit to achieve DCDC conversion; a T-type inverter circuit, which is used to output / input an AC voltage signal, wherein the T-type inverter circuit is also used to switch between three working modes of outputting / inputting AC voltage based on a second drive signal output by the drive circuit; a control circuit, which is used to sample the voltage / current in the energy storage converter circuit, and obtain a control circuit control signal based on the sampling information; and a drive circuit, which is used to generate a first drive signal and a second drive signal based on the control circuit control signal.

[0064] The double-terminal three-level energy storage converter provided in this embodiment improves the traditional energy storage converter circuit topology. The DC end is used to input DC voltage, and the T-type inverter circuit corresponds to outputting AC voltages in three working modes; the T-type inverter circuit corresponds to input AC voltage, and the DC end corresponds to outputting DC voltage; the dual-path full-bridge isolation circuit uses a dual-bridge circuit + high-frequency transformer mode, which reduces costs while miniaturizing, and the switching of the three working modes in the T-type inverter circuit can make full use of the capacitor voltage, reduce switching losses, and improve efficiency, and can realize bidirectional three-level energy flow between DC voltage and AC voltage.

[0065] In the following, a double-ended three-level energy storage converter is described in detail.

[0066] The capacitor C1 connected in parallel between the positive and negative ends of the DC terminal is used for voltage stabilization and filtering.

[0067] The dual-path full-bridge isolation circuit includes switch tubes S3 to S10, a high-frequency transformer T1 and capacitors C3 to C5; wherein the collector of the switch tube S3 and the emitter of the switch tube S4 are respectively connected to the positive and negative ends of the DC end; the emitter of the switch tube S3 is connected to the collector of the switch tube S4, and the emitter of the switch tube S5 is connected to the collector of the switch tube S6, wherein the collector of the switch tube S4 and the collector of the switch tube S6 are respectively connected to the primary side of the high-frequency transformer T1; the emitter of the switch tube S7 is connected to the collector of the switch tube S8, and the collector of the switch tube S8 is connected to the secondary side of the high-frequency transformer T1; the emitter of the switch tube S9 is connected to the collector of the switch tube S1 The collector of the switch tube S0 is connected, and the collector of the switch tube S10 is connected to the other end of the secondary side of the high-frequency transformer T1 through the capacitor C3; the collector of the switch tube S7 and the emitter of the switch tube S8 are respectively connected to the anode and cathode of the capacitor C5; the collector of the switch tube S9 and the emitter of the switch tube S10 are respectively connected to the anode and cathode of the capacitor C4; the cathode of the capacitor C4 and the cathode of the capacitor C5 are connected, which are the common negative terminal of the dual-path full-bridge isolation circuit; the switch tubes S3~S10 are turned on and off based on the first driving signal; the anode of the capacitor C5 is the positive terminal of the high-voltage bus of the dual-path full-bridge isolation circuit; the anode of the capacitor C4 is the positive terminal of the low-voltage bus of the dual-path full-bridge isolation circuit.

[0068] The dual-channel full-bridge isolation circuit outputs U to capacitor C5 H and capacitor C4 output U L Open-loop control is performed to ensure that it always operates at the resonant frequency point, keeping the gain fixed and the efficiency optimized. At the same time, the use of high-frequency transformer + switching circuit greatly reduces the volume and weight of the energy storage inverter.

[0069] When the DC input voltage of the energy storage converter is high and a large boost ratio is not required, the capacitor C1 is used to connect the dual-bridge isolation circuit and the T-type inverter circuit at the subsequent stage. When the DC end needs to adapt to a wider voltage range, a Buck-Boost circuit can also be included.

[0070] Specifically, the Buck-Boost circuit includes a capacitor C1, and the dual-bridge isolation circuit is connected to the DC end through the Buck-Boost circuit to broaden the DC end voltage adaptation range. Specifically, the Buck-Boost circuit may include a capacitor C1, a capacitor C2, an inductor L1, a switch tube S1 and a switch tube S2; wherein the anode of the capacitor C1 is connected to the positive end of the DC end and one end of the inductor L1; wherein the cathode of the capacitor C1 is connected to the negative end of the DC end; the emitter of the switch tube S1 is connected to the collector of the switch tube S2, and the collector of the switch tube S2 is connected to the other end of the inductor L1; the emitter of the switch tube S2 is connected to the negative end of the DC end; the anode and cathode of the capacitor C2 are respectively connected to the collector of the switch tube S1 and the emitter of the switch tube S2, and serve as two connection terminals with the T-type inverter circuit; the drive circuit also generates a third drive signal based on the control circuit control signal; the third drive signal is used to control the opening and closing of the switch tube S1 and the switch tube S2.

[0071] Specifically, the T-type inverter circuit includes switch tubes S11 to S18, a capacitor C6, and an inductor L2; wherein the emitter of the switch tube S15 is connected to the emitter of the switch tube S17 and is connected to the positive end of the low-voltage bus of the dual-path full-bridge isolation circuit; the collector of the switch tube S15 is connected to the collector of the switch tube S16, and the collector of the switch tube S17 is connected to the collector of the switch tube S18; the emitter of the switch tube S11 is connected to the collector of the switch tube S12, wherein the collector of the switch tube S12 is connected to the collector of the switch tube S16. The emitter of the switch tube S11 is connected to one end of the inductor L2; the collector of the switch tube S11 is connected to the positive end of the high-voltage busbar of the dual-path full-bridge isolation circuit; the other end of the inductor L2 is connected to one end of the capacitor C6; the emitter of the switch tube S13 is connected to the collector of the switch tube S14, wherein the collector of the switch tube S14 is connected to the emitter of the switch tube S18 and the other end of the capacitor C6; the two ends of the capacitor C6 are the output / input AC voltage signal terminals; the switch tubes S11 to S18 are turned on and off based on the second drive signal. By adjusting the switching voltage U G , for U H , UL performs closed-loop control.

[0072] The switch tubes S11, S12, S13, S14, S15, S16, S17, and S18 form a T-type three-level circuit, which effectively reduces the switching loss of each switch tube, reduces the AC harmonic voltage and current, and improves the grid-side waveform quality. The anode of capacitor C5, the anode of capacitor C4, and the cathode of C4 form a three-level circuit, which is divided into three working modes, making full use of the capacitor voltage. The midpoint voltage of the bridge arm branch can better approach the sine, which can reduce the volume and weight of inductor L2 and capacitor C6, and improve the power density of the converter.

[0073] The three working modes of the T-type inverter circuit output / input AC voltage include: when the output / input AC voltage is lower than UL When the output / input AC voltage is lower than or higher than U L At the same time, it is lower than U G When the output / input AC voltage is higher than U G At the same time, it is lower than U H When it switches to high-voltage single-ended power supply mode, U L is the voltage across capacitor C4, U H is the voltage across capacitor C5.

[0074] The control circuit sampling information includes the DC input / output DC voltage and current, the high-voltage bus and low-voltage bus voltage and current values ​​in the dual-bridge isolation circuit, and the voltage and current values ​​at both ends of the T-type inverter circuit C6; the control circuit adjusts the switching voltage U according to the sampling information G .

[0075] The control circuit compares the switching voltage U G The voltage and current values ​​of the high-voltage bus and the low-voltage bus in the dual-bridge isolation circuit are used to generate a control signal for the T-type inverter circuit, and the drive circuit generates the second drive signal based on the T-type inverter circuit control signal.

[0076] Based on the control signal of the control circuit, the drive circuit generates a first drive signal to drive the switch tube in the dual full-bridge isolation circuit to be turned on and off, generates a second drive signal to drive the switch tube in the T-type inverter circuit to be turned on and off, and generates a third drive signal to drive the switch tube in the Buck-Boost circuit to be turned on and off.

[0077] When the DC terminal inputs a DC voltage and the T-type inverter circuit outputs an AC voltage signal, the double-terminal three-level energy storage converter works in the inverter state. In the inverter state:

[0078] The Buck-Boost circuit works in the Boost state, and energy flows from the DC side to the AC side. In a control cycle, when the switch tube S2 is turned on, the current flows through the capacitor C1, the inductor L1, and the switch tube S2. The current of the inductor L1 increases and stores energy in the inductor L1. When the switch tube S2 is turned off, the current flows through the capacitor C1, the inductor L1, the switch tube S1, and the capacitor C2. The current of the inductor L1 decreases, and the energy stored in the inductor L1 is released to charge the capacitor C2. At this time, the input and output voltages of the Buck-Boost circuit contain the following relationship:

[0079] U2=U d / d (1)

[0080] Among them, U2 is the voltage across capacitor C2, U dis the voltage between the DC+ and DC- terminals of the energy storage converter, and d is the duty cycle of the pulse width modulation control. At this time, the Buck-Boost circuit inputs its voltage U d The pump is raised to U2 for use in the subsequent dual-path full-bridge isolation circuit.

[0081] The dual-channel full-bridge isolation circuit adopts open-loop control. In one control cycle, capacitor C2 charges capacitors C4 and C5, establishes a low-voltage bus voltage on capacitor C4, and establishes a high-voltage bus voltage on capacitor C5. According to the energy conservation on the transformer, there is the following relationship:

[0082]

[0083] Among them, U2 is the voltage across capacitor C2, U L is the low voltage bus voltage across capacitor C4, U H is the high voltage bus voltage across capacitor C5, N p is the number of turns of the primary side of the high-frequency transformer T1, N s is the number of turns on the secondary side of the high-frequency transformer T1.

[0084] The T-type inverter circuit adopts closed-loop control and outputs AC voltage signals to achieve three working modes:

[0085] (1) When the voltage across capacitor C6 is v G Lower than the voltage U across C4 L , and when it is lower than the switching voltage UG, the T-type inverter circuit works in a low-voltage single-ended power supply mode, and the capacitor C4 in the circuit transmits power to the AC end. G In the positive half cycle of the sine wave, the current flows through capacitor C4, switch tubes S15, S16, inductor L2, capacitor C6, switch tube S14 in turn to transmit power; or flows through inductor L2, capacitor C6, switch tube S14, switch tube S12 in turn to continue current. G In the negative half cycle of the sine wave, the current flows through capacitor C4, switch tubes S17, S18, capacitor C6, inductor L2, switch tube S12 in turn to transmit power; or flows through inductor L2, capacitor C6, switch tube S14, switch tube S12 in turn to continue current. In each control cycle, the distribution time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by the following formula:

[0086]

[0087] Among them, v G is the instantaneous value of the voltage across capacitor C6, U L is the voltage across capacitor C4.

[0088] (2) When the voltage across capacitor C6 is v G Higher than the voltage U across C4L , and at the same time lower than the switching voltage U G When the T-type inverter circuit works in the double-end power supply mode, the capacitors C4 and C5 in the circuit transmit power in turn with the AC end. In the positive half cycle of the sine wave, the current loop flows through the capacitor C5, the switch tube S11, the inductor L2, the capacitor C6, the switch tube S14 in turn to transmit power; or flows through the capacitor C4, the switch tube S15, the switch tube S16, the inductor L2, the capacitor C6, the switch tube S14 in turn to transmit power. In the negative half cycle of the sine wave, it flows through the capacitor C5, the switch tube S13, the capacitor C6, the inductor L2, the switch tube S12 in turn to transmit power; or flows through the capacitor C4, the switch tube S17, the switch tube S18, the capacitor C6, the inductor L2, the switch tube S12 in turn to transmit power. In each control cycle, the allocation time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by the following formula:

[0089]

[0090] Among them, v G is the instantaneous value of the voltage across capacitor C6, U H is the voltage across capacitor C5, U L is the voltage across capacitor C4.

[0091] (3) When the voltage across capacitor C6 is v G Higher than the switching voltage U G , the T-type inverter circuit operates in the high-voltage single-ended power supply mode, and the capacitor C5 in the circuit transmits power to the AC end. In the positive half-cycle of the sine wave, the current loop flows through the capacitor C5, the switch tube S11, the inductor L2, the capacitor C6, the switch tube S14 in sequence to transmit power; or flows through the inductor L2, the capacitor C6, the switch tube S14, and the switch tube S12 in sequence for continuous flow. In the negative half-cycle of the sine wave, it flows through the capacitor C5, the switch tube S13, the capacitor C6, the inductor L2, the switch tube S12 in sequence to transmit power; or flows through the inductor L2, the capacitor C6, the switch tube S14, and the switch tube S12 in sequence for continuous flow. In each control cycle, the allocation time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by the following formula:

[0092]

[0093] Among them, v G is the instantaneous value of the voltage across capacitor C6, U H is the voltage across capacitor C5.

[0094] By adjusting the switching voltage U in the T-type inverter circuit control algorithm G , which can realize the power distribution of the two output ports of the dual-channel full-bridge isolation circuit and stabilize the high and low bus voltages U on capacitors C5 and C4 H and UL In this way, the dual-bridge isolation circuit can maintain open-loop control, always operate at the resonant frequency point, keep the gain fixed and optimize the efficiency. Specifically, the control circuit switches the voltage U G The control formula is as follows:

[0095]

[0096] Among them, U Gp is the amplitude of the AC output voltage of the energy storage converter (i.e. the voltage across capacitor C6), U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, s is the Laplace operator. Determine the switching voltage U according to formula 4 G Then, the working modes are divided according to the above method, and in each working mode, according to the instantaneous voltage values ​​of the current capacitors C4, C5, and C6, the pulse width control duty ratio of the T-type inverter circuit is determined according to the above method to control the current loop. G Realize the voltage U across C5 H Forming a closed-loop control: When U H Higher than reference value When the switching voltage U G The time for the T-type inverter circuit to work in the high-voltage single-ended power supply mode in each power frequency cycle increases, which increases the consumption of the voltage across C5 and makes U H Reduce and return to stability; U H Below the reference value When the switching voltage U G The time for the T-type inverter circuit to work in the high-voltage single-ended power supply mode in each power frequency cycle is reduced, which reduces the consumption of the voltage across C5 and makes U H Improve and return to stability.

[0097] In inverter mode, the voltage of capacitor C2 is controlled by the Buck-Boost circuit in a closed loop. At this time, the voltage across capacitor C4 is U L According to formula (2), the two output voltages U of the dual-bridge isolation circuit are automatically determined. H and U L The AC end of the energy storage converter finally outputs a stable AC voltage.

[0098] When the T-type inverter circuit inputs an AC voltage signal and the DC terminal outputs a DC voltage, the double-terminal three-level energy storage converter works in the rectification state. In the rectification state:

[0099] The T-type inverter circuit adopts closed-loop control to input AC voltage signals and realize three working modes:

[0100] (1) When the voltage across capacitor C6 is v G Lower than the voltage U across C4 L , and at the same time lower than the switching voltage U G When the T-type inverter circuit works in the low-voltage single-ended power supply mode, the AC end of the circuit transmits power to the capacitor C4. G In the positive half cycle of the sine wave, the current flows through capacitor C6, inductor L2, switch tube S16, switch tube S15, capacitor C4, switch tube S14 in sequence to transmit power; or flows through inductor L2, switch tube S12, switch tube S14, capacitor C6 in sequence to store energy. G In the negative half cycle of the sine wave, the current flows through capacitor C6, S18, switch S17, capacitor C4, switch S12, and inductor L2 in sequence to transmit power; or flows through capacitor C6, switch S14, switch S12, and inductor L2 in sequence to store energy. In each control cycle, the distribution time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by formula (3).

[0101] (2) When the voltage across capacitor C6 is v G Higher than the voltage U across C4 L , and at the same time lower than the switching voltage U G When , the T-type inverter circuit works in the double-end power supply mode, and the AC end of the circuit transfers power to capacitors C4 and C5 in turn. In the positive half cycle of the sine wave, the current loop flows through capacitor C6, inductor L2, switch tube S11, capacitor C5, switch tube S14 in turn to transfer power; or flows through capacitor C6, inductor L2, switch tube S16, switch tube S15, capacitor C4, switch tube S14 in turn to transfer power. In the negative half cycle of the sine wave, it flows through capacitor C6, switch tube S13, capacitor C5, switch tube S12, inductor L2 in turn to transfer power; or flows through capacitor C6, switch tube S18, switch tube S17, capacitor C4, switch tube S12, inductor L2 in turn to transfer power. In each control cycle, the distribution time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by formula (4).

[0102] (3) When the voltage across capacitor C6 is v G Higher than the switching voltage U GWhen , the T-type inverter circuit works in the high-voltage single-ended power supply mode, and the AC end of the circuit transmits power to the capacitor C5. In the positive half cycle of the sine wave, the current loop flows through the capacitor C6, the inductor L2, the switch tube S11, the capacitor C5, the switch tube S14 in turn to transmit power; or flows through the capacitor C6, the inductor L2, the switch tube S12, and the switch tube S14 to store energy. In the negative half cycle of the sine wave, it flows through the capacitor C6, the switch tube S13, the capacitor C5, the switch tube S12, and the inductor L2 in turn to transmit power; or flows through the capacitor C6, the switch tube S14, the switch tube S12, and the inductor L2 to store energy. In each control cycle, the distribution time of the two current loops depends on the pulse width modulation control duty cycle d of the T-type inverter circuit, which is calculated by formula (5).

[0103] The control circuit switches the voltage U of the T-type inverter circuit. G The control formula is as follows:

[0104]

[0105] Among them, U Gp is the amplitude of the AC input voltage of the energy storage converter (i.e. the voltage across capacitor C6), U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, s is the Laplace operator. According to formula (7), the switching voltage U is determined G Then, the working modes are divided according to the above method, and in each working mode, according to the instantaneous value of the current AC input voltage of the energy storage converter, the pulse width control duty ratio of the T-type inverter circuit is determined according to the above method to control the current loop. G Realize the voltage U across C5 H Forming a closed-loop control: When U H Higher than reference value When the switching voltage U G The time for the T-type inverter circuit to work in the high-voltage single-ended power supply mode in each power frequency cycle is reduced, which reduces the accumulation of voltage across C5 and makes U H Reduce and return to stability; U H Below the reference value Switching voltage U G The time for the T-type inverter circuit to work in the high-voltage single-ended power supply mode in each power frequency cycle increases, which increases the accumulation of voltage across C5 and makes U H Improve and return to stability.

[0106] The dual-channel full-bridge isolation circuit outputs to the DC end through capacitors C4 and C5 or charges capacitor C2 in the Buck-Boost circuit, and establishes a DC bus voltage on capacitor C2. According to the energy conservation on the transformer, the corresponding relationship is the same as formula (2).

[0107] The energy of the Buck-Boost circuit flows from the AC side to the DC side, and the Buck-Boost circuit works in the Buck state. In a control cycle, when the switch tube S1 is turned on, the current flows through the capacitor C2, the inductor L1, and the capacitor C1, and the current of the inductor L1 increases, storing energy in the inductor; when the switch tube S1 is turned off, the current flows through the inductor L1, the capacitor C1, and the switch tube S2, and the current of the inductor L1 decreases, releasing the energy stored in the inductor L1 and charging the capacitor C1. At this time, the input and output voltages of the Buck-Boost circuit contain the following relationship:

[0108] U d =U2*d (8)

[0109] Among them, U2 is the voltage across capacitor C2, U d is the voltage between the DC+ and DC- terminals of the energy storage converter, and d is the duty cycle of the pulse width modulation control. At this time, the Buck-Boost circuit reduces the voltage U2 across C2 to U d , output by the DC end of the energy storage converter.

[0110] In the rectification mode, the amplitude of the AC voltage will affect the voltage U across capacitor C4. L The voltage across capacitor C2 is then determined according to formula (8). At this time, the energy storage converter controls the voltage across capacitor C1 through a closed-loop Buck-Boost circuit, and outputs a stable DC voltage at the DC end.

[0111] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0112] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A double-ended three-level energy storage converter, characterized in that: include: The DC terminal is used to input / output DC voltage, and a capacitor C1 is connected in parallel between the positive and negative terminals of the DC terminal; A dual-path full-bridge isolation circuit is connected between the DC terminal and the T-type inverter circuit, and is used to perform pulse width modulation control based on the first drive signal output by the drive circuit to achieve DCDC conversion; A T-type inverter circuit is used for outputting / inputting an AC voltage signal, wherein the T-type inverter circuit is also used to switch between three working modes of outputting / inputting AC voltage based on a second driving signal output by a driving circuit; wherein the three working modes include a low-voltage single-ended power supply mode, a double-ended power supply mode, and a high-voltage single-ended power supply mode; when the output / input AC voltage is lower than U L At the same time, it is lower than U G When the output / input AC voltage is higher than U L At the same time, it is lower than U G When the output / input AC voltage is higher than U G At the same time, it is lower than U G , switching to the high voltage single-ended power supply mode; wherein the U L is the positive terminal voltage of the low voltage bus, U H is the positive terminal voltage of the high voltage bus, U G is the switching voltage; A control circuit is used to sample the voltage / current in the energy storage converter circuit and obtain a control circuit control signal based on the sampled information; The driving circuit is used to generate the first driving signal and the second driving signal based on the control circuit control signal.

2. The double-ended three-level energy storage converter according to claim 1, characterized in that: The sampling information includes the DC input / output DC voltage and current of the DC end, the voltage and current values ​​of the high-voltage bus and the low-voltage bus in the dual-bridge isolation circuit, and the voltage and current values ​​of the two ends of the AC end of the T-type inverter circuit; the control circuit adjusts the switching voltage U according to the sampling information G ; The control circuit compares the switching voltage U G A control signal for the T-type inverter circuit is generated according to the voltage and current values ​​of the high-voltage bus and the low-voltage bus in the dual full-bridge isolation circuit, and the drive circuit generates the second drive signal based on the T-type inverter circuit control signal.

3. The double-ended three-level energy storage converter according to claim 1, characterized in that: The dual-path full-bridge isolation circuit includes switch tubes S3-S10, a high-frequency transformer T1 and capacitors C3-C5; The collector of the switch tube S3 and the emitter of the switch tube S4 are connected to the positive and negative ends of the DC end respectively; The emitter of the switch tube S3 is connected to the collector of the switch tube S4, and the emitter of the switch tube S5 is connected to the collector of the switch tube S6, wherein the collector of the switch tube S4 and the collector of the switch tube S6 are respectively connected to the primary side of the high-frequency transformer T1; The emitter of the switch tube S7 is connected to the collector of the switch tube S8, and the collector of the switch tube S8 is connected to one end of the secondary side of the high-frequency transformer T1; The emitter of the switch tube S9 is connected to the collector of the switch tube S10, and the collector of the switch tube S10 is connected to the other end of the secondary side of the high-frequency transformer T1 through the capacitor C3; The collector of the switch tube S7 and the emitter of the switch tube S8 are connected to the anode and cathode of the capacitor C5 respectively; The collector of the switch tube S9 and the emitter of the switch tube S10 are connected to the anode and cathode of the capacitor C4 respectively; The cathodes of the capacitor C4 and the capacitor C5 are connected to each other, and serve as a common negative terminal of the dual-path full-bridge isolation circuit; The switch tubes S3 to S10 are turned on and off based on the first driving signal; The anode of the capacitor C5 is the positive terminal of the high-voltage bus of the dual-path full-bridge isolation circuit; The anode of the capacitor C4 is the positive terminal of the low-voltage busbar of the dual-path full-bridge isolation circuit.

4. The double-ended three-level energy storage converter according to claim 1 or 2, characterized in that: When the energy storage converter is in the inverter state, the U G The control method is as follows: Among them, U G is the switching voltage, U Gp is the output voltage amplitude of the AC end of the energy storage converter, U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, s is the Laplace operator; When the energy storage converter is in the rectifying state, the U G The control method is as follows: Among them, U G is the switching voltage, U Gp is the input voltage amplitude of the AC end of the energy storage converter, U H is the voltage across capacitor C5, is the reference value of the bus voltage across capacitor C5, k p is the proportional control parameter, k i is the integral control parameter, and s is the Laplace operator.

5. The double-ended three-level energy storage converter according to claim 1, characterized in that: The T-type inverter circuit includes switch tubes S11 to S18, capacitor C6, inductor L2, The emitter of the switch tube S15 is connected to the emitter of the switch tube S17 and is connected to the positive end of the low-voltage bus of the dual-path full-bridge isolation circuit; The collector of the switch tube S15 is connected to the collector of the switch tube S16, and the collector of the switch tube S17 is connected to the collector of the switch tube S18; The emitter of the switch tube S11 is connected to the collector of the switch tube S12, wherein the collector of the switch tube S12 is connected to the emitter of the switch tube S16 and to one end of the inductor L2; The collector of the switch tube S11 is connected to the positive terminal of the high-voltage bus of the dual-path full-bridge isolation circuit; The other end of the inductor L2 is connected to one end of the capacitor C6; The emitter of the switch tube S13 is connected to the collector of the switch tube S14, wherein the collector of the switch tube S14 is connected to the emitter of the switch tube S18 and the other end of the capacitor C6; The two ends of the capacitor C6 are the output / input AC voltage signal ends; The switch tubes S11 - S18 are turned on and off based on the second driving signal.

6. The double-ended three-level energy storage converter according to claim 1, characterized in that: The double-terminal three-level energy storage converter further includes a Buck-Boost circuit, the Buck-Boost circuit includes the capacitor C1, and the dual-path full-bridge isolation circuit is connected to the DC end via the Buck-Boost circuit.

7. The double-ended three-level energy storage converter according to claim 6, characterized in that: The Buck-Boost circuit includes a capacitor C1, a capacitor C2, an inductor L1, a switch tube S1 and a switch tube S2; The anode of the capacitor C1 is connected to the positive end of the DC terminal and one end of the inductor L1; wherein the cathode of the capacitor C1 is connected to the negative end of the DC terminal; The emitter of the switch tube S1 is connected to the collector of the switch tube S2, and the collector of the switch tube S2 is connected to the other end of the inductor L1; The emitter of the switch tube S2 is connected to the negative terminal of the DC terminal; The anode and cathode of the capacitor C2 are respectively connected to the collector of the switch tube S1 and the emitter of the switch tube S2, and serve as two connection terminals with the T-type inverter circuit; The driving circuit further generates a third driving signal based on the control circuit control signal; the third driving signal is used to control the switching on and off of the switch tube S1 and the switch tube S2.

8. The double-ended three-level energy storage converter according to claim 7, characterized in that: A DC voltage is input at the DC end, the energy storage converter works in the inverter state, and the T-type inverter circuit outputs an AC voltage signal; the Buck-Boost circuit works in the Boost state, and under the drive of a cycle drive signal of the third drive signal, the switch tube S2 is turned on first, and the current flows through the capacitor C1, the inductor L1, and the switch tube S2; the switch tube S2 is then turned off, and the current flows through the capacitor C1, the inductor L1, the switch tube S1, and the capacitor C2.

9. The double-ended three-level energy storage converter according to claim 7, characterized in that: An AC voltage signal is input to the T-type inverter circuit, the energy storage converter works in a rectification state, and a DC voltage is output at the DC end; the Buck-Boost circuit works in a Buck state, and under the drive of a cycle drive signal of the third drive signal, the switch tube S1 is turned on first, and the current flows through the capacitor C2, the inductor L1, and the capacitor C1; the switch tube S1 is then turned off, and the current flows through the inductor L1, the capacitor C1, and the switch tube S2.

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