Battery energy storage inverter, power control method and battery energy storage inverter system

Abstract

The application discloses a battery energy storage inverter, a power control method and a battery energy storage inverter system. The battery energy storage inverter comprises a direct-current side full-bridge circuit, three groups of alternating-current side half-bridge circuits, a multi-winding high-frequency transformer, a power transmission inductor and an alternating-current side filter inductor. The direct-current side full-bridge circuit and the three groups of alternating-current side half-bridge circuits are connected through the multi-winding high-frequency transformer and the power transmission inductor to complete bidirectional energy transmission between the direct-current side and the alternating-current side. The single-stage structure can realize electrical isolation and direct-current alternating-current conversion functions, without an intermediate direct-current bus, so that the power density and service life of the inverter are effectively improved. The number of alternating-current side power devices is small and bidirectional switches are not needed, so that the cost is reduced. When a fault occurs, all switches can be directly locked, and modulation is simple.

Description

Technical Field

[0001] This application relates to the field of inverter topology technology, and in particular to a battery energy storage inverter, a power control method, and a battery energy storage inverter system. Background Technology

[0002] The power interface between DC power units and the AC grid plays a crucial role in telecommunications power supplies, new energy power generation, and energy storage systems. These converters not only need to meet grid connection requirements such as power factor regulation, input current harmonic suppression, and electrical isolation, but also need to consider engineering parameters such as efficiency, size, and cost. In existing technologies, relatively mature solutions typically employ a two-stage power conversion architecture. This involves a front-end single-phase or three-phase boost converter to regulate the DC-side voltage, followed by a rear-end isolated or non-isolated converter to achieve energy isolation and AC-DC conversion control. However, the energy in a two-stage structure undergoes multiple conversions, and its overall efficiency is significantly affected by cascading losses. Furthermore, the intermediate DC side usually relies on large-capacity energy storage capacitors to maintain power balance, limiting the system's power density and affecting its lifespan.

[0003] To reduce the number of conversion stages, matrix converters have attracted attention due to their single-stage AC / DC conversion capability. Specifically, one aspect discloses a three-phase matrix single-stage isolated bidirectional AC-DC converter. This type of topology offers advantages such as controllable input power factor, low current harmonic content, and bidirectional power flow. However, existing solutions generally rely on a large number of four-quadrant switching devices, which have high voltage ratings and are numerous, leading to cost constraints. Another aspect discloses an improved topology based on the resonant principle, which can achieve soft-switching operation, but suffers from problems such as a large number of devices, unidirectional power, limited gain range, and insufficient control freedom, making it difficult to meet the comprehensive requirements of high efficiency, high power density, and reliable operation for next-generation energy storage and grid-connected applications.

[0004] Therefore, a novel inverter topology and its control method are needed that can simultaneously achieve high-frequency electrical isolation and three-phase AC / DC energy conversion in a single-stage structure, thereby reducing intermediate energy storage links and the number of power conversion stages, and lowering the number of power devices and system costs. Summary of the Invention

[0005] This application provides a battery energy storage inverter, a power control method, and a battery energy storage inverter system. It can achieve electrical isolation and DC-AC conversion functions with a single-stage structure, without an intermediate DC bus, which effectively improves the power density and service life of the inverter. The number of AC power devices is small and there is no need to use bidirectional switches, which reduces costs. In case of a fault, all switches can be directly locked out, and the modulation is simple.

[0006] The embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, embodiments of this application provide a battery energy storage inverter, including a DC-side full-bridge circuit, three AC-side half-bridge circuits, a multi-winding high-frequency transformer, a power transmission inductor, and an AC-side filter inductor.

[0008] The DC-side full-bridge circuit includes fully controlled switching transistors Q1 to Q4, and DC-side filter capacitors are connected in parallel across the two ends of the two bridge arms of the DC-side full-bridge circuit. The DC-side full-bridge circuit is connected to a DC power supply or a DC load.

[0009] The three sets of half-bridge circuits on the AC side include three sets of half-bridge circuits with the same structure and symmetrical parameters. The positive bus of each set of the half-bridge circuits is connected to the three-phase output terminal of the AC power supply through the corresponding AC side filter inductor. The three sets of half-bridge circuits on the AC side include fully controlled switching transistors S1~S6 and capacitors C1~C6.

[0010] The DC-side full-bridge circuit and the three AC-side half-bridge circuits are connected through the multi-winding high-frequency transformer and the power transmission inductor to complete bidirectional energy transmission between the DC and AC sides.

[0011] In some embodiments, the multi-winding high-frequency transformer includes one primary winding and three secondary windings, wherein the primary winding is connected to the midpoint of the two arms of the DC-side full-bridge circuit.

[0012] The secondary winding A of the multi-winding high-frequency transformer is connected to the power transfer inductor L. ka The switch arm of the half-bridge circuit A is connected to the midpoint, and the opposite-named terminal of the secondary winding A is connected to the midpoint of capacitors C1 and C2.

[0013] The secondary winding B of the multi-winding high-frequency transformer is connected to the power transfer inductor L via the same-name terminal. kb The switch arm of the half-bridge circuit B is connected to the midpoint, and the opposite-name terminal of the secondary winding B is connected to the midpoint of capacitors C3 and C4.

[0014] The secondary winding C of the multi-winding high-frequency transformer is connected to the power transfer inductor L via the same-name terminal. kc The switch arm of the half-bridge circuit C is connected to the midpoint, and the opposite-named terminal of the secondary winding C is connected to the midpoint of capacitors C5 and C6.

[0015] In some embodiments, the fully controlled switching transistors S1 to S6 and capacitors C1 to C6 form three half-bridge circuits with identical structures and symmetrical parameters. Specifically, the fully controlled switching transistors S1 and S2 and capacitors C1 and C2 form half-bridge circuit A, the fully controlled switching transistors S3 and S4 and capacitors C3 and C4 form half-bridge circuit B, and the fully controlled switching transistors S5 and S6 and capacitors C5 and C6 form half-bridge circuit C.

[0016] In some embodiments, the positive bus of half-bridge circuit A is connected to the va terminal of the AC power supply through the AC-side filter inductor La; the positive bus of half-bridge circuit B is connected to the vb terminal of the AC power supply through the AC-side filter inductor Lb; the positive bus of half-bridge circuit C is connected to the vc terminal of the AC power supply through the AC-side filter inductor Lc; the neutral lines of AC power supplies va, vb, and vc are connected at point N; and the negative buses of half-bridge circuit A, half-bridge circuit B, and half-bridge circuit C are connected at point O.

[0017] In some embodiments, the power transmission inductor adopts a discrete inductor structure, or is equivalent to the leakage inductance of the multi-winding high-frequency transformer.

[0018] In some embodiments, capacitors C1 to C6 are used to stabilize the midpoint voltage of the corresponding half-bridge circuit and to buffer the transient energy of the system.

[0019] In some embodiments, the AC-side filter inductor is an independent inductor structure or an LCL-type filter structure.

[0020] In some embodiments, the inverter topology enables bidirectional energy transfer between the DC side and the three-phase AC side, and has high-frequency electrical isolation function.

[0021] Secondly, embodiments of this application also provide a power control method based on the battery energy storage inverter described in the first aspect above, comprising the following steps:

[0022] A drive signal is applied to the DC-side full-bridge circuit composed of fully controlled switching transistors Q1 to Q4. The drive signals of the two switching transistors in each arm of the DC-side full-bridge circuit are complementary and have a duty cycle of 0.5. An inner phase shift angle is set between the drive signals of the switching transistors arranged diagonally in the DC-side full-bridge circuit to optimize the system return current power.

[0023] Drive signals are applied to the three half-bridge circuits composed of fully controlled switching transistors S1 to S6 respectively. The drive signals of the two switching transistors in each half-bridge circuit are complementary and the duty cycle is 0.5.

[0024] Three distinct outward phase shift angles are introduced between the drive signals of the three half-bridge circuits and the drive signal of the DC-side full-bridge circuit. By adjusting the magnitude of each outward phase shift angle, the power transmission magnitude and direction of the corresponding half-bridge circuit are controlled respectively.

[0025] Thirdly, embodiments of this application also provide a battery energy storage inverter system, including the battery energy storage inverter described in the first aspect, and a control unit;

[0026] The control unit is electrically connected to the battery energy storage inverter and is used to collect the DC side voltage, AC side three-phase voltage and AC side three-phase current signals of the battery energy storage inverter, and execute the power control method described in the second aspect based on the collected signals to generate a power drive for the battery energy storage inverter.

[0027] The at least one technical solution adopted in this application embodiment can achieve the following beneficial effects: a battery energy storage inverter, including a DC-side full-bridge circuit, three AC-side half-bridge circuits, a multi-winding high-frequency transformer, a power transmission inductor, and an AC-side filter inductor. The DC-side full-bridge circuit includes fully controlled switching transistors Q1~Q4, and a DC-side filter capacitor is connected in parallel to the two ends of the two bridge arms of the DC-side full-bridge circuit, and the DC-side full-bridge circuit is connected to a DC power supply or a DC load; the three AC-side half-bridge circuits include three sets of half-bridge circuits with identical structures and symmetrical parameters, and the positive bus of each set of half-bridge circuits is connected to the three-phase output terminals of the AC power supply through the corresponding AC-side filter inductor; the three AC-side half-bridge circuits include fully controlled switching transistors S1~S6 and capacitors C1~C6; the DC-side full-bridge circuit and the three AC-side half-bridge circuits are connected through the multi-winding high-frequency transformer and the power transmission inductor to complete bidirectional energy transmission between the DC and AC sides. The inverter's DC side consists of a full-bridge circuit composed of fully controlled switches Q1-Q4, while the AC side consists of three symmetrical half-bridges composed of fully controlled switches S1-S6 and capacitors C1-C6. The DC and AC sides are connected by a four-winding transformer, with the primary winding connected to the DC full-bridge and the three secondary windings connected to the three symmetrical half-bridges on the AC side. The positive buses of the three symmetrical half-bridges on the AC side are connected to phases A, B, and C via inductors, while the negative buses are connected together. This single-stage structure achieves electrical isolation and DC-AC conversion without an intermediate DC bus, effectively improving the inverter's power density and lifespan. The AC side has fewer power devices and eliminates the need for bidirectional switches, reducing costs. In case of a fault, all switches can be directly locked out, simplifying modulation. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is a schematic diagram of the topology of the battery energy storage inverter in the embodiments of this application;

[0030] Figure 2 This is a pulse control timing diagram of half-bridge A in the battery energy storage inverter in one switching cycle in this application embodiment;

[0031] Figure 3This is one of the equivalent circuit diagrams of the operation of half-bridge A in a switching cycle of the battery energy storage inverter in the embodiments of this application;

[0032] Figure 4 This is the second equivalent circuit diagram of the operation of half-bridge A in the battery energy storage inverter of this application during one switching cycle;

[0033] Figure 5 This is the third equivalent circuit diagram of the operation of half-bridge A in the battery energy storage inverter during one switching cycle in the embodiments of this application;

[0034] Figure 6 This is the fourth equivalent circuit diagram of the operation of half-bridge A in the battery energy storage inverter during one switching cycle in the embodiments of this application;

[0035] Figure 7 This is the fifth equivalent circuit diagram of the operation of half-bridge A in the battery energy storage inverter during one switching cycle in the embodiments of this application;

[0036] Figure 8 This is the sixth equivalent circuit diagram of the operation of half-bridge A in the battery energy storage inverter of this application during one switching cycle;

[0037] Figure 9 This is a schematic diagram of the closed-loop control strategy in the battery energy storage inverter in the embodiments of this application;

[0038] Figure 10 This is a schematic diagram of the power control method flow of the battery energy storage inverter in the embodiments of this application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0041] This application provides a battery energy storage inverter, such as... Figure 1The diagram shows a schematic topology of a battery energy storage inverter in this embodiment, including a DC-side full-bridge circuit, three AC-side half-bridge circuits, a multi-winding high-frequency transformer, a power transfer inductor, and an AC-side filter inductor. The DC-side full-bridge circuit includes fully controlled switching transistors Q1-Q4, and a DC-side filter capacitor is connected in parallel across the two arms of the DC-side full-bridge circuit. The DC-side full-bridge circuit is connected to a DC power supply or a DC load. The three AC-side half-bridge circuits include three sets of identical and symmetrical half-bridge circuits. The positive bus of each half-bridge circuit is connected to the three-phase output of the AC power supply through the corresponding AC-side filter inductor. The three AC-side half-bridge circuits include fully controlled switching transistors S1-S6 and capacitors C1-C6. The DC-side full-bridge circuit and the three AC-side half-bridge circuits are connected through the multi-winding high-frequency transformer and the power transfer inductor to complete bidirectional energy transfer between the DC and AC sides.

[0042] Specifically, the battery energy storage inverter topology includes a DC-side full-bridge circuit, three AC-side half-bridge circuits, a multi-winding high-frequency transformer, a power transmission inductor, and an AC-side filter inductor.

[0043] The DC-side full-bridge circuit consists of fully controlled switching transistors Q1 to Q4. A DC-side filter capacitor Cdc is connected in parallel between the two arms of the full bridge and is connected to the DC power supply or DC load to stabilize the DC-side voltage and provide transient energy buffering. The midpoints of the two arms of the full bridge are connected to the primary windings of a multi-winding high-frequency transformer, thereby achieving electrical isolation and energy transfer between the DC and AC sides under high-frequency conditions.

[0044] The AC side includes three identical and symmetrical half-bridge circuits: half-bridge circuit A, half-bridge circuit B, and half-bridge circuit C. Half-bridge circuit A consists of fully controlled switches S1 and S2 and capacitors C1 and C2; half-bridge circuit B consists of fully controlled switches S3 and S4 and capacitors C3 and C4; and half-bridge circuit C consists of fully controlled switches S5 and S6 and capacitors C5 and C6. The capacitors in each half-bridge circuit are used to stabilize the midpoint voltage of the half-bridge or to buffer energy, thereby improving the stability of the system operation.

[0045] In this circuit, the positive bus of half-bridge circuit A is connected to AC power supply va through AC-side filter inductor La. Half-bridge circuits B and C are connected to AC power supplies VB and VC respectively through AC-side filter inductors Lb and Lc. The neutral lines of the three-phase AC power supplies are connected at point N. The negative buses of the three sets of half-bridge circuits converge at point O to form a common reference point. The AC-side filter inductor is used to suppress high-frequency switching harmonics and improve the grid-connected current quality; in other embodiments, the AC-side filter inductor can also adopt an LCL-type filter structure.

[0046] The multi-winding high-frequency transformer includes one primary winding and three secondary windings, each corresponding to one of the three half-bridge circuits on the AC side. The corresponding terminals of secondary winding A are connected via the power transfer inductor L. ka The switching arm of half-bridge circuit A is connected to the midpoint, and its opposite-named terminal is connected to the midpoint of capacitors C1 and C2; secondary windings B and C are connected to power transfer inductor L in the same manner. kb L kc Connected to half-bridge circuits B and C. Power transfer inductor L. ka L kb L kc The parameters of the power are the same. The power transfer inductor is used to regulate the rate of change of current during energy transfer. It can be an independently set discrete inductor or equivalently formed by the leakage inductance of a multi-winding high-frequency transformer.

[0047] In this embodiment, a power control method based on phase-shift modulation is proposed for the aforementioned battery energy storage inverter topology to achieve bidirectional energy transfer between the DC side and the three-phase AC side, while taking into account both power backflow suppression and system efficiency improvement.

[0048] First, a drive signal is applied to the full-bridge structure composed of controllable switches Q1 to Q4 in the DC-side full-bridge circuit. The two switches in each arm of the full bridge use a complementary drive method, and their duty cycles are both set to 0.5. Based on this, an inner phase shift angle is introduced between the drive signals of the diagonally positioned switches in the two arms of the full bridge. By adjusting this inner phase shift angle, the full bridge can balance power transmission requirements and return current suppression under different operating conditions.

[0049] Secondly, drive signals are applied to the three sets of half-bridge circuits on the AC side, which are composed of controllable switching transistors S1 to S6. The upper and lower switching transistors in each half-bridge circuit also adopt a complementary drive mode, and the duty cycle of each half-bridge circuit is 0.5. In this way, each half-bridge circuit generates alternating bridge arm voltages under high-frequency conditions, providing a basis for subsequent power regulation.

[0050] Furthermore, three different outward phase shift angles are introduced between the drive signals of the three sets of half-bridge circuits and the DC-side full-bridge drive signal. By adjusting each outward phase shift angle separately, independent control of the power transmission magnitude and direction of the corresponding half-bridge circuits can be achieved, thereby meeting the requirements of three-phase AC-side power decoupling regulation.

[0051] In one embodiment of this application, the multi-winding high-frequency transformer includes one primary winding and three secondary windings. The primary winding is connected to the midpoint of the two arms of the DC-side full-bridge circuit. The corresponding terminals of the secondary winding A of the multi-winding high-frequency transformer are connected through a power transfer inductor L.ka The switching arm of the half-bridge circuit A is connected to the midpoint, and the opposite-named terminal of the secondary winding A is connected to the midpoint of capacitors C1 and C2; the same-named terminal of the secondary winding B of the multi-winding high-frequency transformer is connected to the power transfer inductor L. kb The switching arm of the half-bridge circuit B is connected to the midpoint, and the opposite-named terminal of the secondary winding B is connected to the midpoint of capacitors C3 and C4; the same-named terminal of the secondary winding C of the multi-winding high-frequency transformer is connected to the power transfer inductor L. kc The switch arm of the half-bridge circuit C is connected to the midpoint, and the opposite-named terminal of the secondary winding C is connected to the midpoint of capacitors C5 and C6.

[0052] A multi-winding high-frequency transformer consists of one primary winding and three secondary windings.

[0053] The primary winding of the multi-winding high-frequency transformer is connected to the midpoint of the two arms of the DC-side full bridge.

[0054] The secondary winding A of the multi-winding high-frequency transformer is connected to the power transfer inductor L. ka The switch arm of the half-bridge circuit A is connected to the midpoint, and the opposite-named terminal of the secondary winding A is connected to the midpoint of capacitors C1 and C2.

[0055] The secondary winding B of the multi-winding high-frequency transformer is connected to the power transfer inductor L via the same-name terminal. kb The switch arm of the half-bridge circuit B is connected to the midpoint, and the opposite-name terminal of the secondary winding B is connected to the midpoint of capacitors C3 and C4.

[0056] The secondary winding C of the multi-winding high-frequency transformer is connected to the power transfer inductor L via the same-name terminal. kc The switch arm of the half-bridge circuit C is connected to the midpoint, and the opposite-named terminal of the secondary winding C is connected to the midpoint of capacitors C5 and C6.

[0057] In one embodiment of this application, the fully controlled switches S1~S6 and capacitors C1~C6 form three half-bridge circuits with identical structures and symmetrical parameters. Specifically, the fully controlled switches S1 and S2 and capacitors C1 and C2 form half-bridge circuit A, the fully controlled switches S3 and S4 and capacitors C3 and C4 form half-bridge circuit B, and the fully controlled switches S5 and S6 and capacitors C5 and C6 form half-bridge circuit C.

[0058] In one embodiment of this application, the positive bus of half-bridge circuit A is connected to the va terminal of AC power supply through AC-side filter inductor La; the positive bus of half-bridge circuit B is connected to the vb terminal of AC power supply through AC-side filter inductor Lb; the positive bus of half-bridge circuit C is connected to the vc terminal of AC power supply through AC-side filter inductor Lc; the neutral lines of AC power supply va, vb, and vc are connected at point N; and the negative buses of half-bridge circuit A, half-bridge circuit B, and half-bridge circuit C are connected at point O.

[0059] In one embodiment of this application, the power transmission inductor adopts a discrete inductor structure, or is equivalently formed by the leakage inductance of the multi-winding high-frequency transformer.

[0060] In one embodiment of this application, capacitors C1 to C6 are used to stabilize the midpoint voltage of the corresponding half-bridge circuit and to buffer the transient energy of the system.

[0061] In one embodiment of this application, the AC side filter inductor is an independent inductor structure or an LCL-type filter structure.

[0062] In one embodiment of this application, the inverter topology enables bidirectional energy transfer between the DC side and the three-phase AC side, and has high-frequency electrical isolation function.

[0063] The inner phase shift angle of the full-bridge circuit is determined based on the DC-side voltage, AC-side voltage, and system power transmission range. Through closed-loop control of the three-phase AC current, three outer phase shift angles between the half-bridge circuit and the full-bridge circuit are dynamically generated. The range of the inner phase shift angle ensures that the fully controlled switches in the full-bridge circuit operate under soft-switching conditions. The three outer phase shift angles can be adjusted independently of each other, achieving decoupled control of the three-phase AC power.

[0064] Preferably, the closed-loop control of the three-phase current on the AC side adopts any one of proportional-integral control, proportional-resonant control, or model predictive control.

[0065] Preferably, by coordinating and adjusting the values ​​of the inner phase shift angle and the outer phase shift angle, the power backflow inside the system is reduced, thereby improving the operating efficiency of the battery energy storage inverter.

[0066] Taking half-bridge circuit A as an example, the pulse control timing diagram within one switching cycle is as follows: Figure 2 As shown. The inner phase shift angle of the DC-side full-bridge is D2, and the outer phase shift angle between the DC-side full-bridge and half-bridge circuit A is D. A The switching cycle is divided into 6 stages at each switching moment, such as Figures 3-8 As shown.

[0067] During the t0~t1 stage, such as Figure 3 As shown, DC-side full-bridge switches Q1 and Q3 are turned on, AC-side half-bridge switch S2 is turned on, the primary voltage of the transformer is 0, and the secondary voltage is -0.5V. aO The voltage across the power transfer inductor is 0.5V. aO The inductor current increases.

[0068] During the t1~t2 stage, such as Figure 4As shown, DC-side full-bridge switches Q1 and Q4 are conducting, AC-side half-bridge switch S2 is conducting, and the transformer primary voltage is v. dc The secondary voltage is -0.5V. aO The voltage across the power transfer inductor is nV. dc +0.5V aO The inductor current increases.

[0069] During the t2~t3 phase, such as Figure 5 As shown, DC-side full-bridge switches Q1 and Q4 are conducting, AC-side half-bridge switch S1 is conducting, and the transformer primary voltage is v. dc The secondary voltage is 0.5V. aO The voltage across the power transfer inductor is nV. dc -0.5v aO The direction of change of the inductor current is related to the instantaneous value of the AC side current.

[0070] During the t3~t4 stage, such as Figure 6 As shown, DC-side full-bridge switches Q2 and Q4 are turned on, AC-side half-bridge switch S1 is turned on, the transformer primary voltage is 0, and the secondary voltage is 0.5V. aO The voltage across the power transfer inductor is -0.5V. aO The inductor current decreases.

[0071] In the t4~t5 stage, such as Figure 7 As shown, DC-side full-bridge switches Q2 and Q3 are conducting, AC-side half-bridge switch S1 is conducting, and the transformer primary voltage is -V. dc The secondary voltage is 0.5V. aO The voltage across the power transfer inductor is -nV. dc -0.5v aO The inductor current decreases.

[0072] In the t5~t6 stage, such as Figure 8 As shown, DC-side full-bridge switches Q2 and Q3 are conducting, AC-side half-bridge switch S2 is conducting, and the transformer primary voltage is -V. dc The secondary voltage is -0.5V. aO The voltage across the power transfer inductor is -nV. dc +0.5V aO The direction of change of the inductor current is related to the instantaneous value of the AC side current.

[0073] Based on the inductor voltage expressions for the above six stages, the inductor current expressions for each moment can be obtained. Integrating the voltage and current over one switching cycle yields the expression for the transmitted power:

[0074] Where fs is the switching frequency.

[0075] Based on the DC-side voltage, AC-side voltage, and the system's allowable power transmission range, the inner phase shift angle range of the DC-side full-bridge is predetermined to ensure the full-bridge maintains soft-switching operation within this range. The AC-side three-phase current is regulated via closed-loop control, dynamically calculating the outer phase shift angle between each half-bridge and the DC-side full-bridge based on the current deviation. The closed-loop control of the AC-side three-phase current can employ any of the following: proportional-integral (PI) control, proportional-resonant (PI) control, or model predictive control; the specific control method can be selected based on system performance requirements. For example, the closed-loop control block diagram for PI control is shown below. Figure 9 As shown.

[0076] like Figure 10 As shown in the embodiments of this application, a power control method based on the battery energy storage inverter is also provided, including the following steps:

[0077] Step S1010: Apply a drive signal to the DC-side full-bridge circuit composed of fully controlled switching transistors Q1~Q4. The drive signals of the two switching transistors in each arm of the DC-side full-bridge circuit are complementary and have a duty cycle of 0.5. Set an inner phase shift angle between the drive signals of the switching transistors diagonally arranged in the DC-side full-bridge circuit to optimize the system return current power.

[0078] Step S1020: Apply drive signals to the three half-bridge circuits composed of fully controlled switching transistors S1 to S6 respectively. The drive signals of the two switching transistors in each half-bridge circuit are complementary and the duty cycle is 0.5.

[0079] Step S1030: Three different outward phase shift angles are introduced between the drive signals of the three half-bridge circuits and the drive signal of the DC-side full-bridge circuit. By adjusting the size of each outward phase shift angle, the power transmission magnitude and direction of the corresponding half-bridge circuit are controlled respectively.

[0080] A full-bridge structure composed of controllable switching transistors Q1 to Q4, wherein the driving signals of the switching transistors in each bridge arm are complementary and the duty cycle of each is 0.5; in the two bridge arms of the full bridge, the driving signals of the diagonally arranged switching transistors are provided with an inner phase shift angle to optimize the return current power.

[0081] Drive signals are applied to the three sets of half-bridges composed of controllable switching transistors S1 to S6, so that the drive signals of the switching transistors in each half-bridge are complementary to each other, and the duty cycle of each half-bridge is 0.5.

[0082] Three different outward phase shift angles are introduced between the drive signals of the three sets of half-bridges and the drive signals of the DC-side full-bridge, respectively, to adjust the power transmission of the corresponding half-bridges.

[0083] Optionally, the inner phase shift angle of the DC-side full bridge is determined based on the DC-side voltage, AC-side voltage, and power transmission range, and the outer phase shift angle between each half bridge and the DC-side full bridge is obtained through closed-loop control of the AC-side three-phase current.

[0084] Optionally, the range of values ​​for the inner phase shift angle is used to ensure that the DC-side full bridge operates under soft-switching conditions.

[0085] Optionally, the three outward phase angles can be adjusted independently of each other.

[0086] Optionally, the closed-loop control of the three-phase current on the AC side adopts any one of proportional-integral control, proportional-resonant control, or model predictive control.

[0087] Optionally, the power return current can be reduced and the system operating efficiency improved by coordinating the inner and outer phase shift angles.

[0088] This application embodiment also provides a battery energy storage inverter system, including the aforementioned battery energy storage inverter and a control unit;

[0089] The control unit is electrically connected to the battery energy storage inverter and is used to collect the DC side voltage, AC side three-phase voltage and AC side three-phase current signals of the battery energy storage inverter, and to generate a power control method based on the collected signals to drive the battery energy storage inverter.

[0090] The power control method achieves power transmission by controlling the inner phase shift angle of the DC-side full bridge and the outer phase shift angle between the DC-side full bridge and the AC-side half bridge.

[0091] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A battery energy storage inverter, characterized in that, It includes a DC-side full-bridge circuit, three AC-side half-bridge circuits, a multi-winding high-frequency transformer, a power transfer inductor, and an AC-side filter inductor. The DC-side full-bridge circuit includes fully controlled switching transistors Q1 to Q4, and DC-side filter capacitors are connected in parallel across the two ends of the two bridge arms of the DC-side full-bridge circuit. The DC-side full-bridge circuit is connected to a DC power supply or a DC load. The three sets of half-bridge circuits on the AC side include three sets of half-bridge circuits with the same structure and symmetrical parameters. The positive bus of each set of the half-bridge circuits is connected to the three-phase output terminal of the AC power supply through the corresponding AC side filter inductor. The three sets of half-bridge circuits on the AC side include fully controlled switching transistors S1~S6 and capacitors C1~C6. The DC-side full-bridge circuit and the three AC-side half-bridge circuits are connected through the multi-winding high-frequency transformer and the power transmission inductor to complete bidirectional energy transmission between the DC and AC sides. The multi-winding high-frequency transformer includes one primary winding and three secondary windings. The primary winding is connected to the midpoint of the two arms of the DC-side full-bridge circuit. The same-name terminal of the secondary winding A of the multi-winding high-frequency transformer is connected to the midpoint of the switching arm of the half-bridge circuit A through the power transmission inductor Lka, and the opposite-name terminal of the secondary winding A is connected to the midpoint of capacitors C1 and C2. The same-name terminal of the secondary winding B of the multi-winding high-frequency transformer is connected to the midpoint of the switching arm of the half-bridge circuit B through the power transmission inductor Lkb, and the opposite-name terminal of the secondary winding B is connected to the midpoint of capacitors C3 and C4. The same-name terminal of the secondary winding C of the multi-winding high-frequency transformer is connected to the midpoint of the switching arm of the half-bridge circuit C through the power transmission inductor Lkc, and the opposite-name terminal of the secondary winding C is connected to the midpoint of capacitors C5 and C6. The fully controlled switches S1-S6 and capacitors C1-C6 form three identical and symmetrical half-bridge circuits. S1 and S2, along with capacitors C1 and C2, form half-bridge circuit A; S3 and S4, along with capacitors C3 and C4, form half-bridge circuit B; and S5 and S6, along with capacitors C5 and C6, form half-bridge circuit C. The positive bus of half-bridge circuit A is connected to the va terminal of the AC power supply via the AC-side filter inductor La. The positive bus of half-bridge circuit B is connected to the vb terminal of the AC power supply via the AC-side filter inductor Lb. The positive bus of half-bridge circuit C is connected to the vc terminal of the AC power supply via the AC-side filter inductor Lc. The neutral lines of the AC power supplies va, vb, and vc converge at point N. The negative buses of half-bridge circuits A, B, and C converge at point O.

2. The battery energy storage inverter according to claim 1, characterized in that, The power transmission inductor adopts a discrete inductor structure, or is equivalent to the leakage inductance of the multi-winding high-frequency transformer.

3. The battery energy storage inverter according to claim 1, characterized in that, The capacitors C1 to C6 are used to stabilize the midpoint voltage of the corresponding half-bridge circuit and to buffer the transient energy of the system.

4. The battery energy storage inverter according to claim 1, characterized in that, The AC side filter inductor is an independent inductor structure or adopts an LCL type filter structure.

5. The battery energy storage inverter according to claim 1, characterized in that, The inverter's topology enables bidirectional energy transfer between the DC side and the three-phase AC side, and also features high-frequency electrical isolation.

6. A power control method based on the battery energy storage inverter according to any one of claims 1 to 5, characterized in that, Includes the following steps: A drive signal is applied to the DC-side full-bridge circuit composed of fully controlled switching transistors Q1 to Q4. The drive signals of the two switching transistors in each arm of the DC-side full-bridge circuit are complementary and have a duty cycle of 0.

5. An inner phase shift angle is set between the drive signals of the switching transistors arranged diagonally in the DC-side full-bridge circuit to optimize the system return current power. Drive signals are applied to the three half-bridge circuits composed of fully controlled switching transistors S1 to S6 respectively. The drive signals of the two switching transistors in each half-bridge circuit are complementary and the duty cycle is 0.

5. Three distinct outward phase shift angles are introduced between the drive signals of the three half-bridge circuits and the drive signal of the DC-side full-bridge circuit. By adjusting the magnitude of each outward phase shift angle, the power transmission magnitude and direction of the corresponding half-bridge circuit are controlled respectively.

7. A battery energy storage inverter system, characterized in that, This includes a battery energy storage inverter and a control unit; The control unit is electrically connected to the battery energy storage inverter and is used to collect the DC side voltage, AC side three-phase voltage and AC side three-phase current signals of the battery energy storage inverter, and execute the power control method of claim 6 based on the collected signals to generate a power drive for the battery energy storage inverter.

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