A distributed energy storage device with series compensation function

Abstract

The application provides a distributed energy storage device with series compensation function, comprising a power main circuit, a control unit and an isolation circuit; the power main circuit is electrically connected with the control unit and the isolation circuit; the power main circuit comprises high-voltage components, low-voltage components and a three-phase bus; the control unit comprises a sampling conditioning circuit, a digital control circuit and an isolation driving circuit; the sampling conditioning circuit samples input voltage or current of the power main circuit and DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak electric signal and inputs the weak electric signal into a sampling port of the digital control circuit; the digital control circuit outputs a control signal to the driving isolation circuit, and the driving isolation circuit converts the control signal into pulse electric quantity of power devices in the power main circuit; the number of the isolation circuits is at least three groups, which are connected with a distributed photovoltaic grid-connected system, an AC side of the internal high-voltage components and an AC side of the low-voltage components respectively.

Description

Technical Field

[0001] The present invention relates to the field of substation technology, and in particular to a distributed energy storage device with series compensation function. Background Technology

[0002] With the rapid development of new energy power generation, mainly photovoltaic and wind power, a large number of distributed photovoltaic systems have been connected to medium and low voltage distribution networks. Due to the influence of variable weather factors such as sunlight, cloud cover and wind speed, photovoltaic power generation naturally has intermittent and fluctuating characteristics, which determines that its grid-connected power quality is not high, seriously affecting the power supply quality and reliability of medium and low voltage distribution networks.

[0003] Currently, medium- and low-voltage distribution networks contain a large number of distributed photovoltaic (PV) systems. If these systems are transformed into grid-friendly devices through simple modifications, the overall cost of improving the distribution network system will be reduced, system complexity will be lowered, and the overall efficiency of the distribution network system will be improved. Existing patents have proposed the structure and control strategy of a unified power quality regulator with PV grid-connected power generation capabilities. This system can simultaneously achieve comprehensive power quality management, PV grid-connected power generation, and power compensation. However, the structure of this device is relatively complex, the topology is typically a two-stage back-to-back configuration, the device capacity must be greater than or equal to twice the interconnection power, the cost is relatively high, and the device size is large. Therefore, this invention proposes a technical solution with smaller device capacity and lower cost to address these shortcomings. Summary of the Invention

[0004] To address the shortcomings of previous inventions, this invention proposes a distributed energy storage device with series compensation function. By reducing the local power capacity of the device, it achieves precise control of the voltage of the series-connected link, thereby achieving the goal of precise power control in multi-line interconnection. At the same time, it addresses the voltage and power problems caused by reverse overload of the power grid in the distribution network. Furthermore, this device does not affect the operation of distributed photovoltaic devices in the original line, nor does it have adverse effects on other system parts.

[0005] To achieve the above objectives, embodiments of the present invention provide a distributed energy storage device with series compensation function, comprising: The system includes a main power circuit, a control unit, and an isolation circuit; wherein the main power circuit is electrically connected to both the control unit and the isolation circuit. The main power circuit includes a high-voltage component, a low-voltage component, and a three-phase busbar. The three-phase busbars are phase A, phase B, and phase C, and each phase busbar is connected to the common potential point of the high-voltage component and the low-voltage component, as well as the AC side of the external converter. The control unit includes a sampling conditioning circuit, a digital control circuit, and an isolation drive circuit. The sampling conditioning circuit samples the input voltage or current of the power main circuit and the DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak electrical signal before inputting it to the sampling port of the digital control circuit. The digital control circuit outputs a control signal to the drive isolation circuit, and the drive isolation circuit converts the control signal into a pulse electrical quantity of the power device in the power main circuit. The isolation circuits are at least three sets, which are respectively connected to the distributed photovoltaic grid-connected system, the AC side of the internal high-voltage component, and the AC side of the low-voltage component.

[0006] The distributed energy storage device with series compensation function provided in this embodiment of the invention includes: a power main circuit, a control unit, and an isolation circuit; wherein, the power main circuit is electrically connected to the control unit and the isolation circuit respectively; the power main circuit includes a high-voltage component, a low-voltage component, and a three-phase bus, wherein the three-phase bus is A phase, B phase, and C phase, and each phase bus is connected to the common potential point of the high-voltage component and the low-voltage component, and the AC side of the external converter respectively; the control unit includes a sampling conditioning circuit, a digital control circuit, and an isolation drive circuit; the sampling conditioning circuit samples the input voltage or current of the power main circuit and the DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak electrical signal before inputting it to the sampling port of the digital control circuit; the digital control circuit outputs a control signal to the drive isolation circuit, and the drive isolation circuit converts the control signal into pulse electrical quantities of the power devices in the power main circuit; the number of isolation circuits is at least 3 sets, which are respectively connected to the distributed photovoltaic grid-connected system, the AC side of the internal high-voltage component, and the AC side of the low-voltage component. By reducing the local power capacity of the equipment, precise control of the voltage of the series-connected link can be achieved, thereby achieving the goal of precise control of the interconnected power in multiple lines. At the same time, it can address the voltage and power problems caused by reverse overload of the power grid in the distribution network. Furthermore, this device affects the operation of distributed photovoltaic devices in the original line and has adverse effects on other system parts. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the structure of a distributed energy storage device with series compensation function in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a power main circuit in an embodiment of the present invention; Figure 3 This is an example diagram of a high-voltage component control strategy in an embodiment of the present invention; Figure 4 This is an example diagram of a low-voltage component control strategy in an embodiment of the present invention; Figure 5This is a schematic diagram of the structure of an intermediate isolation converter according to an embodiment of the present invention; Figure 6 This is a schematic diagram of an intermediate isolation converter control strategy in an embodiment of the present invention; Figure 7 This is a schematic diagram of an external converter control strategy in one embodiment. Detailed Implementation

[0008] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0009] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0010] It is understood that before using the technical solutions disclosed in the various embodiments of this disclosure, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in this disclosure in an appropriate manner in accordance with relevant laws and regulations, and user authorization should be obtained.

[0011] Figure 1 This is a schematic diagram of a distributed energy storage device with series compensation function provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the device includes a power main circuit, a control unit, and an isolation circuit; wherein the power main circuit is electrically connected to the control unit and the isolation circuit respectively.

[0012] Figure 2 This is a schematic diagram of the structure of a power main circuit in an embodiment of the present invention, such as... Figure 2As shown, the main power circuit includes a high-voltage component, a low-voltage component, and a three-phase busbar. The three-phase busbars are phase A, phase B, and phase C, and each phase busbar is connected to the common potential point of the high-voltage component and the low-voltage component, as well as the AC side of the external converter.

[0013] The control unit includes a sampling conditioning circuit, a digital control circuit, and an isolated drive circuit. The sampling conditioning circuit samples the input voltage or current of the power main circuit and the DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak electrical signal (usually 0-3.3V) before inputting it to the sampling port of the digital control circuit. The digital control circuit outputs a control signal to the drive isolation circuit, and the drive isolation circuit converts the control signal into a pulse electrical quantity of the power device in the power main circuit.

[0014] The isolation circuit includes a disconnect switch and an EMC circuit. There are at least three isolation circuits, respectively connected to the distributed photovoltaic grid-connected system, the AC side of the internal high-voltage component, and the AC side of the low-voltage component. Optionally, the number of isolation circuits can be expanded according to system requirements.

[0015] Specifically, such as Figure 2 As shown, the high-voltage component includes multiple converter units connected in series. Each converter unit consists of a front-end submodule and an intermediate isolation converter cascaded together. The DC output sides of the multiple intermediate isolation converters are connected in parallel and connected to the input port of the low-voltage component.

[0016] Among them, the front-end sub-module of the high-voltage component is a half-bridge sub-module, a full-bridge sub-module, or a combination of a half-bridge module and a full-bridge module.

[0017] Among them, the intermediate isolation converter is a dual active full-bridge structure, a back-to-back isolated DC-AC-DC converter, a bidirectional forward circuit, a bidirectional flyback circuit, or a combination of a bidirectional forward circuit and a bidirectional flyback circuit.

[0018] The low-voltage components include a front-end submodule, which can be a half-bridge submodule, a full-bridge submodule, or a combination of a half-bridge submodule and a full-bridge submodule.

[0019] The energy storage element in the front-end submodule can be any one of a capacitor, a supercapacitor, or an electrochemical cell.

[0020] In this embodiment, the main power circuit is electrically connected to an external converter; the external converter is usually an existing photovoltaic grid-connected device, which includes photovoltaic cells and connected inverter circuits. The inverter circuit is composed of power devices, including but not limited to power diodes, insulated gate bipolar transistors (IGBTs), power MOSFETs, power BJTs, and integrated gate commutated thyristors (IGCTs).

[0021] In this embodiment, the distributed energy storage device with series compensation function can control the high-voltage components, the low-voltage components, and the external converter.

[0022] The photovoltaic grid-connected device, consisting of the high-voltage component, the low-voltage component, and the external converter, all employs dual closed-loop control.

[0023] Optionally, the outer loop of the high-voltage component is controlled by a constant DC voltage, and the inner loop is controlled by a constant DC current. The high-voltage component is controlled using the algorithm corresponding to the following formula: ； in, L n The inductance value at the input terminal of line n. i ndq The input current of line n ω For the grid-connected power grid angular frequency, u gndq Line-side voltage, u dndq To output local voltage for high-voltage components, u d0dq This refers to the output voltage of the existing grid-connected converter equipment. in, ; in, For the input current of line 1, This is the output current of the existing grid-connected device. Let n be the input current of line n.

[0024] For example, for line n=1, the formula can be expressed as: .

[0025] For example, Figure 3 This is an example diagram of a high-voltage component control strategy in an embodiment of the present invention, such as... Figure 3 As shown, the high-voltage components are controlled by cascaded PI control of the DC-side voltage outer loop and the dq-axis current inner loop. Specifically, as shown... Figure 3 As shown, for the DC voltage outer loop, the input signal is the DC reference voltage. u dc_ref With actual voltage u dc The deviation is used to generate the d-axis current reference value after PI adjustment. i d1_ref For the d-axis current inner loop, the input signal is the current reference value. i d1_refWith d-axis actual current i d1 The deviation, after PI regulation, is fed forward with the grid voltage. U grid1_d Coupling terms ωLi q1 The values ​​are superimposed to output the d-axis control quantity. For the q-axis current inner loop, the input signal is the q-axis current reference value. i q1_ref With q-axis actual current i q1 The deviation, after PI regulation, is fed forward with the grid voltage. U grid1_q Coupling terms ωLi d1 The control signals are superimposed to output the q-axis control quantity. Finally, the d-axis and q-axis control quantities undergo a dq-abc transformation to generate a three-phase modulated signal. The dq-abc transformation can be understood as converting the dq-axis control quantities into a modulated signal in a three-phase abc coordinate system. ωLi q1 , ωLi d1 It is the cross-coupling term of the grid inductance L in the dq coordinate system. The coupling interference is eliminated by feedforward compensation to ensure independent control of the dq axis current. U grid1_d , U grid1_q It involves grid-side voltage feedforward to improve the system's dynamic response speed and reduce the impact of grid voltage fluctuations on current control. The PI control can be proportional-integral control, hysteresis control, or nonlinear control.

[0026] Optionally, the outer loop control of the low-voltage components adopts a P / Q outer loop, and the inner loop adopts a current dual inner loop control.

[0027] For example, Figure 4 This is an example diagram of the low-voltage component control strategy in an embodiment of the present invention, such as... Figure 4 As shown, the control of low-voltage components is achieved through cascaded PI control of the DC-side power outer loop and the dq-axis current inner loop. Specifically, as shown... Figure 4 As shown, for the DC power outer loop, the input signal is the power reference value. p n_ref With actual power p n The deviation is used to generate the d-axis current reference value after PI adjustment. i dn_ref For the d-axis current inner loop, the input signal is the current reference value. i dn_ref With d-axis actual current i dn The deviation, after PI regulation, is fed forward with the grid voltage.U gridn_d Coupling terms ωLi qn The values ​​are superimposed to output the d-axis control quantity. For the q-axis current inner loop, the input signal is the q-axis current reference value. i qn_ref With q-axis actual current i qn The deviation, after PI regulation, is fed forward with the grid voltage. U gridn_q Coupling terms ωLi dn The control signals are superimposed to output the q-axis control quantity. Finally, the d-axis and q-axis control quantities undergo a dq-abc transformation to generate a three-phase modulated signal. The dq-abc transformation can be understood as converting the dq-axis control quantities into a modulated signal in a three-phase abc coordinate system. ωLi qn , ωLi dn It is the cross-coupling term of the grid inductance L in the dq coordinate system. The coupling interference is eliminated by feedforward compensation to ensure independent control of the dq axis current. U gridn_d , U gridn_q It involves grid-side voltage feedforward to improve the system's dynamic response speed and reduce the impact of grid voltage fluctuations on current control. The PI control can be proportional-integral control, hysteresis control, or nonlinear control.

[0028] For example, Figure 5 This is a schematic diagram of the structure of an intermediate isolation converter according to an embodiment of the present invention, as shown below. Figure 5 As shown, the intermediate isolation converter in the high-voltage component adopts a dual active full-bridge structure. The left half is an H-bridge circuit, and the AC output of the H-bridge is connected to the left half port of the intermediate isolation converter. The right half port of the intermediate isolation converter is connected to the right H-bridge circuit. Figure 6 This is a schematic diagram of the intermediate isolation converter control strategy in an embodiment of the present invention, as shown below. Figure 6 As shown, control of the intermediate isolation converter is achieved through cascaded PI control of the voltage outer loop, current inner loop, and frequency adjustment loop. For the voltage outer loop: the input signal is the DC reference voltage. V dcref With actual DC voltage V dc The deviation is then adjusted by a PI controller to output a reference current value. For the inner current loop: the input signal is the current reference value. With actual input current i in The deviation, after being adjusted by a PI controller, is the output frequency deviation Δf. For the frequency adjustment loop: the rabbit signal serves as the frequency reference value.f ∗ Deviation from frequency deviation Δf f s ,deviation f s After adjustment by the PWM module, two complementary drive pulses are generated, namely, the full-bridge switch drive signals T1, T4 and T2, T3. Among them, the PI control is proportional-integral control, hysteresis control or nonlinear control.

[0029] Optionally, the external converter can be controlled using the algorithm corresponding to the following formula; ; Where L0 is the input-side inductance value of the original equipment. ω is the input current of the existing grid-connected device, and ω is the angular frequency of the grid. The input voltage of the original device, u ddq C is the inverter-side voltage at the equipment output. 11 This represents the capacitance value of the busbar on the straight side.

[0030] Optional, Figure 7 This is a schematic diagram of the external converter control strategy in an embodiment of the present invention, as shown below. Figure 7 As shown, the external converter is controlled by cascaded PI control of the DC-side voltage outer loop and the dq-axis current inner loop. Specifically, as shown... Figure 7 As shown, for the DC voltage outer loop, the input signal is the DC side reference voltage. u dc_ref With actual voltage u dc The deviation is used to generate the d-axis current reference value after PI adjustment. i d0_ref For the d-axis current inner loop, the input signal is the current reference value. i d0_ref With d-axis actual current i d0 The deviation, after PI regulation, is fed forward with the load voltage. U 0_d Coupling terms ωLi q0 The values ​​are superimposed to output the d-axis control quantity. For the q-axis current inner loop, the input signal is the q-axis current reference value. i q0_ref With q-axis actual current i q0 The deviation, after PI regulation, is fed forward with the load voltage. U 0_q Coupling terms ωLi d0The control signals are superimposed to output the q-axis control signal. Finally, the d-axis and q-axis control signals undergo dq-abc transformation to generate a three-phase modulated signal. The synchronization angle for coordinate transformation is generated by a phase-locked loop (PLL) or an internal oscillator. The dq-abc transformation can be understood as converting the dq axis control quantity into a modulation signal in a three-phase abc coordinate system. ωLi q0 , ωLi d0 It is the cross-coupling term of the grid inductance L in the dq coordinate system. The coupling interference is eliminated by feedforward compensation to ensure independent control of the dq axis current. U 0_d , U 0_q It uses load voltage feedforward to improve the system's dynamic response speed and reduce the impact of grid voltage fluctuations on current control. PI control can be proportional-integral control, hysteresis control, or nonlinear control.

[0031] The distributed energy storage device with series compensation function provided in this embodiment includes: a power main circuit, a control unit, and an isolation circuit; wherein, the power main circuit is electrically connected to the control unit and the isolation circuit respectively; the power main circuit includes a high-voltage component, a low-voltage component, and three-phase buses of phase A, phase B, and phase C, each phase bus being connected to the common potential point of the high-voltage component and the low-voltage component, and the AC side of the external converter respectively; the control unit includes a sampling conditioning circuit, a digital control circuit, and an isolation drive circuit; the sampling conditioning circuit samples the input voltage or current of the power main circuit and the DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak electrical signal before inputting it to the sampling port of the digital control circuit; the digital control circuit outputs a control signal to the drive isolation circuit, and the drive isolation circuit converts the control signal into pulse electrical quantities of the power devices in the power main circuit; the number of isolation circuits is at least 3 sets, which are respectively connected to the distributed photovoltaic grid-connected system, the AC side of the internal high-voltage component, and the AC side of the low-voltage component. By reducing the local power capacity of the equipment, precise control of the voltage of the series-connected link can be achieved, thereby achieving the goal of precise control of the interconnected power in multiple lines. At the same time, it can address the voltage and power problems caused by reverse overload of the power grid in the distribution network. Furthermore, this device affects the operation of distributed photovoltaic devices in the original line and has adverse effects on other system parts.

[0032] Compared with the prior art, the present invention has the following characteristics: The patent provides a new topology, including a series structure and a parallel structure, wherein the high-voltage series component and the low-voltage series component have internal topologies, are interconnected, and are connected to the original converter.

[0033] This invention proposes a control method for the corresponding equipment, enabling flexible grid connection of multiple grid ports and existing grid-connected equipment. This method can achieve interconnection power control of different ports and series voltage compensation, while not affecting the active power control function of the original equipment.

[0034] As can be seen from the above technical solutions, compared with the parallel access structure adopted in existing distributed energy storage technologies, the converter of this invention only controls the voltage part, and the ratio of the maximum power to the controlled power of the device is the ratio of the series voltage to the rated voltage. At the same time, this device can connect to AC voltages of different amplitudes, and the voltage transformation ratio is much higher than the voltage ratio between traditional interconnected devices. This invention has good application and promotion effects.

Claims

1. A distributed energy storage device with series compensation function, characterized in that, include: The system includes a main power circuit, a control unit, and an isolation circuit; wherein the main power circuit is electrically connected to both the control unit and the isolation circuit. The main power circuit includes a high-voltage component, a low-voltage component, and a three-phase busbar. The three-phase busbars are phase A, phase B, and phase C, and each phase busbar is connected to the common potential point of the high-voltage component and the low-voltage component, as well as the AC side of the external converter. The control unit includes a sampling conditioning circuit, a digital control circuit, and an isolation drive circuit; the sampling conditioning circuit samples the input voltage or current of the power main circuit and the DC capacitor voltage inside the power main circuit, and converts the sampled voltage signal into a weak signal before inputting it to the sampling port of the digital control circuit. The digital control circuit outputs a control signal to the drive isolation circuit, and the drive isolation circuit converts the control signal into pulse electrical quantities of the power devices in the power main circuit. The isolation circuits are at least three sets, which are respectively connected to the distributed photovoltaic grid-connected system, the AC side of the internal high-voltage component, and the AC side of the low-voltage component.

2. The distributed energy storage device with series compensation function according to claim 1, characterized in that, The high-voltage component includes multiple converter units connected in series. Each converter unit is composed of a front-end submodule and an intermediate isolation converter cascaded together. The DC output sides of the multiple intermediate isolation converters are connected in parallel and connected to the input port of the low-voltage component.

3. The distributed energy storage device with series compensation function according to claim 2, characterized in that, The front-end submodule of the high-voltage component is a half-bridge submodule, a full-bridge submodule, or a combination of a half-bridge submodule and a full-bridge submodule.

4. The distributed energy storage device with series compensation function according to claim 2, characterized in that, The intermediate isolation converter is a dual active full-bridge structure, a back-to-back isolated DC-AC-DC converter, a bidirectional forward circuit, a bidirectional flyback circuit, or a combination of a bidirectional forward circuit and a bidirectional flyback circuit.

5. The distributed energy storage device with series compensation function according to claim 1, characterized in that, The low-voltage component includes a front-end submodule, which is a half-bridge submodule, a full-bridge submodule, or a combination of a half-bridge submodule and a full-bridge submodule.

6. The distributed energy storage device with series compensation function according to claim 3 or 5, characterized in that, The energy storage element in the front-end submodule is any one of a capacitor, a supercapacitor, or an electrochemical cell.

7. The distributed energy storage device with series compensation function according to claim 1, characterized in that, The photovoltaic grid-connected device, consisting of the high-voltage component, the low-voltage component, and the external converter, all employs dual closed-loop control.

8. The distributed energy storage device with series compensation function according to claim 7, characterized in that, The outer ring of the high-voltage component is controlled by DC voltage, and the inner ring is controlled by dq-axis current. For the DC voltage outer loop, the DC reference voltage u dc_ref With actual voltage u dc The deviation is determined as the input signal, and the input signal is adjusted by a PI controller to generate a d-axis current reference value. i d1_ref ; For the inner loop of the d-axis current, the d-axis current reference value i d1_ref With d-axis actual current i d1 The deviation is determined as the input signal, which is then PI-regulated and fed forward with the grid voltage. U grid1_d Coupling terms ωLi q1 Superimpose the values ​​and output the d-axis control quantity; For the inner loop of the q-axis current, the q-axis current reference value will be... i q1_ref With q-axis actual current i q1 The deviation is determined as the input signal, which is then PI-regulated and fed forward with the grid voltage. U grid1_q Coupling terms ωLi d1 The values ​​are superimposed to output the q-axis control quantity. The d-axis control quantity and the q-axis control quantity are subjected to dq-abc transformation to generate a three-phase modulation signal.

9. The distributed energy storage device with series compensation function according to claim 7, characterized in that, The outer ring of the low-voltage component and the high-voltage component are controlled by DC power, and the inner ring is controlled by dq-axis current. For the DC power outer loop, the power reference value p n_ref With actual power p n The deviation is determined as the input signal, and the input signal is adjusted by a PI controller to generate a d-axis current reference value. i dn_ref ; For the inner loop of the d-axis current, the d-axis current reference value i dn_ref With d-axis actual current i dn The deviation is determined as the input signal, and the input signal is PI-regulated and then fed forward with the grid voltage. U gridn_d Coupling terms ωLi qn Superimpose the values ​​and output the d-axis control quantity; For the inner loop of the q-axis current, the q-axis current reference value will be... i qn_ref With q-axis actual current i qn The deviation is determined as the input signal, which is then PI-regulated and fed forward with the grid voltage. U gridn_q Coupling terms ωLi dn The values ​​are superimposed to output the q-axis control quantity. The d-axis control quantity and the q-axis control quantity are subjected to dq-abc transformation to generate a three-phase modulation signal.

10. The distributed energy storage device with series compensation function according to claim 7, characterized in that, The outer loop of the external converter is controlled by DC voltage, and the inner loop is controlled by dq-axis current. For the DC voltage outer loop, the DC reference voltage u dc_ref With actual voltage u dc The deviation is determined as the input signal, and the input signal is adjusted by PI to generate the d-axis current reference value. i d0_ref ; For the inner loop of the d-axis current, the d-axis current reference value i d0_ref With d-axis actual current i d0 The deviation is determined as the input signal, and the input signal is PI-regulated and fed forward with the load voltage. U 0_d Coupling terms ωLi q0 Superimpose the values ​​and output the d-axis control quantity; For the inner loop of the q-axis current, the q-axis current reference value will be... i q0_ref With q-axis actual current i q0 The deviation is determined as the input signal, and the input signal is PI-regulated and fed forward with the load voltage. U 0_q Coupling terms ωLi d0 The values ​​are superimposed to output the q-axis control quantity. The d-axis control quantity and the q-axis control quantity are subjected to dq-abc transformation to generate a three-phase modulation signal.

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