Direct power control method and system for high voltage direct mounted energy storage power unit to tow platform

Abstract

The application provides a power direct control method and system of a high-voltage direct-hanging energy storage power unit to a towing platform, wherein an output end H-bridge power unit module and an input end H-bridge power unit module are connected back to back through a connecting inductor; the direct current side of the output end H-bridge power unit module and the input end H-bridge power unit module each comprises a direct current side battery, a direct current side filtering inductor, a direct current side capacitor and an H-bridge power unit, the positive pole of the direct current side battery is connected in series with the direct current side filtering inductor, and then connected in parallel with the direct current side capacitor, and the two ends after the parallel connection are respectively used as the direct current side positive pole end and the negative pole end of the H-bridge power unit; a PCS unit sub-controller is connected with the output end H-bridge power unit module and the input end H-bridge power unit module, the modulation ratio and the phase of the input end H-bridge power unit module are reversely solved according to the given active power and the reactive power, the corresponding modulation waveform is generated, and the direct control of the transmission power between the two H-bridge power unit modules is realized.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a method and system for direct power control of a tugboat platform by a high-voltage direct-connected energy storage power unit. More specifically, it relates to a method and system for direct power control of a tugboat platform by a high-voltage direct-connected energy storage power unit based on power given and inversely solving control parameters. Background Technology

[0002] High-voltage direct-connect energy storage systems utilize a high-voltage direct-connect power conversion system (PCS) to divide the massive number of battery cells required by the system into numerous battery clusters and distribute them to the DC side of the power module. The AC side of these clusters is then cascaded to increase the output voltage and individual unit capacity of the PCS, allowing for transformerless direct connection to the high-voltage grid. The H-bridge power module, as the basic power unit in a high-voltage direct-connect energy storage system, directly impacts the efficiency and stability of the entire system through its performance and control methods.

[0003] In a high-voltage direct-connected energy storage power unit parallel platform, two H-bridge power unit modules are connected back-to-back via connecting inductors for simulating power transmission and system testing. Traditional parallel control methods typically require simultaneous adjustment of the modulation ratio and phase difference of the two H-bridge power unit modules to achieve power control. Specifically, the traditional method involves setting the phase difference... The active power P and reactive power Q transmitted are indirectly controlled by the modulation ratio M, and its power transmission characteristics are described by the following equation:

[0004] in, and These are the effective values ​​of the AC side voltages of the two H-bridge power unit modules, respectively. To connect the inductive reactance of the inductor, This represents the phase difference between the two H-bridge power unit modules.

[0005] However, traditional towing control methods have the following technical problems: First, the relationship between control parameters and power targets is indirect. In traditional methods, users need to first specify the modulation ratio and phase difference, and then calculate the actual transmitted power through the power transmission equation. It is not possible to directly set control parameters based on the desired power value, making the control process cumbersome and unintuitive.

[0006] Secondly, power point tracking accuracy is affected by DC-side voltage fluctuations. In actual systems, the DC-side battery has internal resistance, which causes a voltage shift during power transmission. Traditional feedforward calculation methods still rely on ideal DC voltage values ​​and do not consider the voltage shift caused by battery internal resistance, resulting in a discrepancy between the actual output power and the given power.

[0007] Third, it lacks a compensation mechanism for non-ideal factors in the system. Traditional open-loop control methods rely entirely on feedforward calculations and do not depend on feedback adjustment. When system parameters deviate, they cannot be automatically corrected, resulting in poor control robustness.

[0008] Therefore, there is an urgent need for an H-bridge towing platform control method that can automatically calculate the control parameters of the H-bridge power unit module based on the given active and reactive power requirements, and can compensate for the effects of non-ideal factors such as DC side voltage deviation.

[0009] Patent application CN114884078A discloses a high-voltage direct-connected system integrating reactive power compensation and energy storage. It includes calculating the amplitude and relative phase of the zero-sequence voltage based on parameter information of a cascaded H-bridge converter and grid-side current; calculating the setpoint value of the output voltage of each phase of the cascaded H-bridge converter based on the reactive power setpoint of the high-voltage direct-connected energy storage system; calculating the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter based on the battery state of charge, the amplitude and relative phase of the zero-sequence voltage of each phase; calculating the number of sub-modules required for the nearest-level modulation based on the battery state of charge and capacitor voltage of each power module in each phase, and the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter; sorting the battery state of charge of each power module; and determining the drive signal of each power module based on the current direction of each phase and the number of power modules required for the nearest-level modulation. However, this patent cannot completely solve the existing technical problems and cannot meet the needs of this invention. Summary of the Invention

[0010] In view of the deficiencies in the prior art, the purpose of this invention is to provide a method and system for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit.

[0011] According to the present invention, the high-voltage direct-connected energy storage power unit for direct power control of a towing platform includes an output H-bridge power unit module, an input H-bridge power unit module, a connecting inductor, and a PCS unit sub-controller. The output H-bridge power unit module and the input H-bridge power unit module are connected back-to-back via the connecting inductor; the PCS unit sub-controller is connected to both the output H-bridge power unit module and the input H-bridge power unit module. Both the output H-bridge power unit module and the input H-bridge power unit module include a DC-side battery, a DC-side filter inductor, a DC-side capacitor, and an H-bridge power unit on their DC sides. The positive terminal of the DC-side battery is connected in series with the DC-side filter inductor to form a series branch. This series branch is connected in parallel with the DC-side capacitor, and the two ends of the parallel connection serve as the positive and negative terminals of the DC side of the H-bridge power unit, respectively. The direct power control method includes the following steps: Step S1: Obtain the given active power reference value and reactive power reference value, the DC side voltage of the output H-bridge power unit module and the input H-bridge power unit module, as well as the fixed modulation ratio, system frequency, phase angle and inductance value of the connected inductor of the output H-bridge power unit module; Step S2: Calculate the effective value of the AC side voltage of the output H-bridge power unit module based on the DC side voltage and fixed modulation ratio of the output H-bridge power unit module; Step S3: Calculate the inductive reactance based on the system frequency and the inductance value of the connecting inductor, and calculate the constant based on the effective value of the AC side voltage of the output H-bridge power unit module and the inductive reactance; Step S4: Based on the given active power reference value, reactive power reference value, constant, and effective value of AC side voltage of the output H-bridge power unit module, establish the power transfer equation and solve in reverse the effective value and phase of AC side voltage of the input H-bridge power unit module. Step S5: Calculate the modulation ratio of the input H-bridge power unit module based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module; Step S6: Based on the phase angle of the output H-bridge power unit module and the phase of the input H-bridge power unit module, generate modulation waveforms for the output H-bridge power unit module and the input H-bridge power unit module to control the active and reactive power transmitted between the two H-bridge power unit modules.

[0012] Preferably, the DC-side voltages of the output H-bridge power unit module and the input H-bridge power unit module are real-time measured values.

[0013] Preferably, the effective value of the AC side voltage of the output H-bridge power unit module is calculated based on the DC side voltage of the output H-bridge power unit module and the fixed modulation ratio of the output H-bridge power unit module. The calculation formula is:

[0014] in, The fixed modulation ratio of the output H-bridge power unit module, This refers to the DC-side voltage of the output H-bridge power unit module.

[0015] Preferably, the inductive reactance is calculated based on the system frequency and the inductance value of the connecting inductor. The calculation formula is:

[0016] Based on the effective value of the AC side voltage and the calculated inductive reactance constant of the output H-bridge power unit module. The calculation formula is:

[0017] in, It is pi. For system frequency, This is the inductance value of the connected inductor.

[0018] Preferably, the power transfer equation is:

[0019] Where P represents active power and Q represents reactive power. This represents the effective value of the AC side voltage of the input H-bridge power unit module. This represents the phase difference between the output H-bridge power unit module and the input H-bridge power unit module.

[0020] Preferably, the method for reversely solving the effective value and phase of the AC side voltage of the input H-bridge power unit module is as follows: taking the given active power reference value and reactive power reference value as known quantities, substituting them into the power transfer equation, and solving simultaneously to obtain the effective value and phase of the AC side voltage of the input H-bridge power unit module.

[0021] Preferably, the modulation ratio of the input H-bridge power unit module is calculated based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module. The calculation formula is:

[0022] in, This refers to the DC-side voltage of the input H-bridge power unit module.

[0023] Preferably, the modulation ratio of the input H-bridge power unit module is limited to the range of [0, 1]; the phase of the input H-bridge power unit module is limited to the range of [-π / 2, π / 2].

[0024] Preferably, the fixed modulation ratio of the output H-bridge power unit module is in the range of 0.7 to 0.9.

[0025] The power direct control system for the high-voltage direct-connected energy storage power unit to the towing platform provided by the present invention includes an output H-bridge power unit module, an input H-bridge power unit module, a connecting inductor, and a PCS unit sub-controller. The output H-bridge power unit module and the input H-bridge power unit module are connected back-to-back via the connecting inductor; the PCS unit sub-controller is connected to both the output H-bridge power unit module and the input H-bridge power unit module. Both the output H-bridge power unit module and the input H-bridge power unit module include a DC-side battery, a DC-side filter inductor, a DC-side capacitor, and an H-bridge power unit on their DC sides. The positive terminal of the DC-side battery is connected in series with the DC-side filter inductor to form a series branch. This series branch is connected in parallel with the DC-side capacitor, and the two ends of the parallel connection serve as the positive and negative terminals of the DC side of the H-bridge power unit, respectively. The direct power control system includes the following modules: Module M1: Obtains the given active power reference value and reactive power reference value, the DC side voltage of the output H-bridge power unit module and the input H-bridge power unit module, as well as the fixed modulation ratio, system frequency, phase angle and inductance value of the connected inductor of the output H-bridge power unit module; Module M2: Calculate the effective value of the AC side voltage of the output H-bridge power unit module based on the DC side voltage and fixed modulation ratio of the output H-bridge power unit module; Module M3: Calculates the inductive reactance based on the system frequency and the inductance value of the connecting inductor, and calculates the constant based on the effective value of the AC side voltage of the output H-bridge power unit module and the inductive reactance; Module M4: Based on the given active power reference value, reactive power reference value, constant, and the effective value of the AC side voltage of the output H-bridge power unit module, establish the power transfer equation and solve in reverse the effective value and phase of the AC side voltage of the input H-bridge power unit module; Module M5: Calculates the modulation ratio of the input H-bridge power unit module based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module; Module M6: Based on the phase angle of the output H-bridge power unit module and the phase of the input H-bridge power unit module, it generates modulation waveforms for the output H-bridge power unit module and the input H-bridge power unit module to control the active and reactive power transmitted between the two H-bridge power unit modules.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention proposes a direct power control method for a towing platform based on power given and reverse solution of control parameters. By fixing the modulation ratio and phase of the output H-bridge power unit module, the modulation ratio and phase of the input H-bridge power unit module are directly solved in reverse according to the given active power and reactive power, realizing the direct solution from power target to control parameters. The control process is intuitive and simple. (2) The present invention introduces a real-time feedback compensation mechanism for DC side voltage. By measuring the actual DC bus voltage of the two H-bridge power unit modules, it effectively compensates for the influence of DC voltage deviation caused by battery internal resistance on power transmission and improves power tracking accuracy. (3) The present invention provides dual limiting protection of modulation ratio and phase. It limits the modulation ratio of the input H-bridge power unit module to [0,1] to ensure operation in the linear modulation region, and limits the phase of the input H-bridge power unit module to [-π / 2, π / 2] to avoid excessive phase difference leading to current distortion, thus ensuring the safe and stable operation of the system. Attached Figure Description

[0027] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A schematic diagram of the main circuit topology of the power unit to drag platform provided by the present invention; Figure 2 A flowchart of the power unit's direct power control method for the towing platform provided by the present invention; Figure 3 Simulation results of the power unit's direct power control method for the towing platform provided by this invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] Example This invention provides a method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit, which utilizes the power unit to control the towing platform. The high-voltage direct-connected energy storage power unit towing platform includes: an output H-bridge power unit module, an input H-bridge power unit module, a connecting inductor, and a PCS unit sub-controller. The output H-bridge power unit module and the input H-bridge power unit module are connected back-to-back via connecting inductors. The PCS unit sub-controller is connected to the output H-bridge power unit module and the input H-bridge power unit module, respectively. Both the output H-bridge power unit module and the input H-bridge power unit module include a DC-side battery, a DC-side filter inductor, a DC-side capacitor, and an H-bridge power unit on their DC sides. The positive terminal of the DC-side battery is connected in series with the DC-side filter inductor to form a series branch. This series branch is connected in parallel with the DC-side capacitor, and the two ends of the parallel connection serve as the positive and negative terminals of the DC side of the H-bridge power unit, respectively.

[0030] like Figure 2 The direct power control method includes: Step S1: Obtain the given active power reference value and reactive power reference value And the DC-side voltage of the output H-bridge power unit module. DC side voltage of the input H-bridge power unit module Fixed modulation ratio of the output H-bridge power unit module System frequency f, connecting inductor L, phase angle of the output H-bridge power unit module ; Step S2: Based on the DC side voltage of the output H-bridge power unit module and fixed modulation ratio Calculate the effective value of the AC side voltage of the output H-bridge power unit module. ; Step S3: Calculate the inductive reactance based on the system frequency f and the connecting inductance L. Then calculate the constant. ; Step S4: Based on the given active power and reactive power And the constant k and the effective value of the AC side voltage of the output H-bridge power unit module. Establish the power transfer equation and solve in reverse for the effective value of the AC side voltage of the input H-bridge power unit module. and phase ; Step S5: Based on the effective value of the AC side voltage of the input H-bridge power unit module. and the DC side voltage of the input H-bridge power unit module Calculate the modulation ratio of the input H-bridge power unit module. ; Step S6: Based on the phase angle of the output H-bridge power unit module Phase angle with the input H-bridge power unit module It generates modulation waveforms for the output H-bridge power unit module and the input H-bridge power unit module, and controls the active power and reactive power transmitted between the two H-bridge power unit modules. The effective value of the AC side voltage of the output H-bridge power unit module in step S2 The calculation formula is:

[0031] in, The fixed modulation ratio of the output H-bridge power unit module, This refers to the DC-side voltage of the output H-bridge power unit module.

[0032] In step S3, the inductive The formula for calculating the constant k is:

[0033] in, π is the mathematical constant pi, f is the system frequency, and L is the connecting inductance.

[0034] The power transfer equation in step S4 is:

[0035] Where P represents active power and Q represents reactive power. This represents the effective value of the AC side voltage of the output H-bridge power unit module. The effective value of the AC side voltage of the input H-bridge power unit module. For resistance, This represents the phase difference between the two H-bridge power unit modules.

[0036] In step S4, the effective value of the AC side voltage of the input H-bridge power unit module is calculated in reverse. and phase The method is as follows: make ; but ; Where A and B are process parameters, Given a reference value for active power, Given a reactive power reference value, .

[0037] The modulation ratio of the input H-bridge power unit module in step S5 The calculation formula is:

[0038] in, The DC-side voltage of the input H-bridge power unit module; for Amplitude limiting is applied, restricting the amplitude to the range [0, 1].

[0039] Step S6 also includes phasing the input H-bridge power unit module. Amplitude limiting is applied to the range of [-π / 2, π / 2] to avoid excessive phase difference causing current distortion.

[0040] The DC side voltage of the output H-bridge power unit module in step S1 and the DC side voltage of the input H-bridge power unit module These are real-time measurements used to compensate for voltage deviations caused by the internal resistance of the DC-side battery.

[0041] The fixed modulation ratio of the output H-bridge power unit module The value range is 0.7 to 0.9 to ensure the linear modulation region and leave a voltage margin.

[0042] like Figure 1 As shown, the H-bridge power supply platform includes an output H-bridge power unit module and an input H-bridge power unit module, which are connected back-to-back via a connecting inductor L. The DC-side parameters of the two H-bridge modules are identical, and the specific parameter settings are as follows: The H-bridge towing platform is configured with a rated active power of 160kW, a DC-side battery rated voltage of 998.4V, a battery capacity of 314Ah, a battery internal resistance of 0.065Ω, a DC-side filter inductance of 0.0016H, a DC-side filter capacitor of 0.01215F, a system frequency of f=50Hz, a power device switching frequency of 1000Hz, and a sinusoidal SPWM pulse width modulation method.

[0043] To ensure the H-bridge module operates in the linear modulation region and allows for sufficient dynamic adjustment margin, the fixed modulation ratio of the output H-bridge power unit module is set to... =0.85, the phase difference under rated operating conditions is selected. =10°, connected inductor L=1.24mH.

[0044] The simulation time is set to 6 seconds. The simulation process is shown in the table below:

[0045] Simulated waveforms such as Figure 3 As shown, during the 0~0.5s positive full-load phase, the actual active power is precisely stable at 160kW, and the reactive power is close to 0. During the 0.5~1s switching of operating conditions, the power direction reverses rapidly, and the actual active power smoothly transitions to -160kW, with rapid dynamic response and no overshoot oscillation. At the same time, it can be seen that during the entire simulation process, the output voltage waveform of the H-bridge power unit exhibits a sinusoidal SPWM pulse width modulation waveform, and the output current has good sinusoidal characteristics. During the switching of operating conditions, the load current waveform synchronously undergoes phase switching, with rapid dynamic response and no current oscillation.

[0046] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0047] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit, characterized in that, The high-voltage direct-connected energy storage power unit towing platform includes an output H-bridge power unit module, an input H-bridge power unit module, a connecting inductor, and a PCS unit sub-controller. The output H-bridge power unit module and the input H-bridge power unit module are connected back-to-back via the connecting inductor; the PCS unit sub-controller is connected to both the output H-bridge power unit module and the input H-bridge power unit module. Both the output H-bridge power unit module and the input H-bridge power unit module include a DC-side battery, a DC-side filter inductor, a DC-side capacitor, and an H-bridge power unit on their DC sides. The positive terminal of the DC-side battery is connected in series with the DC-side filter inductor to form a series branch. This series branch is connected in parallel with the DC-side capacitor, and the two ends of the parallel connection serve as the positive and negative terminals of the DC side of the H-bridge power unit, respectively. The direct power control method includes the following steps: Step S1: Obtain the given active power reference value and reactive power reference value, the DC side voltage of the output H-bridge power unit module and the input H-bridge power unit module, as well as the fixed modulation ratio, system frequency, phase angle and inductance value of the connected inductor of the output H-bridge power unit module; Step S2: Calculate the effective value of the AC side voltage of the output H-bridge power unit module based on the DC side voltage and fixed modulation ratio of the output H-bridge power unit module; Step S3: Calculate the inductive reactance based on the system frequency and the inductance value of the connecting inductor, and calculate the constant based on the effective value of the AC side voltage of the output H-bridge power unit module and the inductive reactance; Step S4: Based on the given active power reference value, reactive power reference value, constant, and effective value of AC side voltage of the output H-bridge power unit module, establish the power transfer equation and solve in reverse the effective value and phase of AC side voltage of the input H-bridge power unit module. Step S5: Calculate the modulation ratio of the input H-bridge power unit module based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module; Step S6: Based on the phase angle of the output H-bridge power unit module and the phase of the input H-bridge power unit module, generate modulation waveforms for the output H-bridge power unit module and the input H-bridge power unit module to control the active and reactive power transmitted between the two H-bridge power unit modules.

2. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 1, characterized in that, The DC-side voltages of the output H-bridge power unit module and the input H-bridge power unit module are measured in real time.

3. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 1, characterized in that, Calculate the effective value of the AC side voltage of the output H-bridge power unit module based on the DC side voltage of the output H-bridge power unit module and the fixed modulation ratio of the output H-bridge power unit module. The calculation formula is: in, The fixed modulation ratio of the output H-bridge power unit module, This refers to the DC-side voltage of the output H-bridge power unit module.

4. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 3, characterized in that, Calculate the inductive reactance based on the system frequency and the inductance value of the connected inductor. The calculation formula is: Based on the effective value of the AC side voltage and the calculated inductive reactance constant of the output H-bridge power unit module. The calculation formula is: in, It is pi. For system frequency, This is the inductance value of the connected inductor.

5. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 4, characterized in that, The power transfer equation is: Where P represents active power and Q represents reactive power. This represents the effective value of the AC side voltage of the input H-bridge power unit module. This represents the phase difference between the output H-bridge power unit module and the input H-bridge power unit module.

6. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 5, characterized in that, The method for reversely solving the effective value and phase of the AC side voltage of the input H-bridge power unit module is as follows: taking the given active power reference value and reactive power reference value as known quantities, substituting them into the power transfer equation, and solving simultaneously to obtain the effective value and phase of the AC side voltage of the input H-bridge power unit module.

7. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 6, characterized in that, The modulation ratio of the input H-bridge power unit module is calculated based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module. The calculation formula is: in, This refers to the DC-side voltage of the input H-bridge power unit module.

8. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 7, characterized in that, The modulation ratio of the input H-bridge power unit module is limited to the range of [0, 1]; the phase of the input H-bridge power unit module is limited to the range of [-π / 2, π / 2].

9. The method for direct power control of a towing platform by a high-voltage direct-connected energy storage power unit according to claim 1, characterized in that, The fixed modulation ratio of the output H-bridge power unit module ranges from 0.7 to 0.

9.

10. A direct power control system for a high-voltage direct-connected energy storage power unit to a towing platform, characterized in that, The method for direct power control of a towing platform using a high-voltage direct-connected energy storage power unit according to any one of claims 1 to 9, wherein the high-voltage direct-connected energy storage power unit for the towing platform includes an output H-bridge power unit module, an input H-bridge power unit module, a connecting inductor, and a PCS unit sub-controller; The output H-bridge power unit module and the input H-bridge power unit module are connected back-to-back via the connecting inductor; the PCS unit sub-controller is connected to both the output H-bridge power unit module and the input H-bridge power unit module. Both the output H-bridge power unit module and the input H-bridge power unit module include a DC-side battery, a DC-side filter inductor, a DC-side capacitor, and an H-bridge power unit on their DC sides. The positive terminal of the DC-side battery is connected in series with the DC-side filter inductor to form a series branch. This series branch is connected in parallel with the DC-side capacitor, and the two ends of the parallel connection serve as the positive and negative terminals of the DC side of the H-bridge power unit, respectively. The direct power control system includes the following modules: Module M1: Obtains the given active power reference value and reactive power reference value, the DC side voltage of the output H-bridge power unit module and the input H-bridge power unit module, as well as the fixed modulation ratio, system frequency, phase angle and inductance value of the connected inductor of the output H-bridge power unit module; Module M2: Calculate the effective value of the AC side voltage of the output H-bridge power unit module based on the DC side voltage and fixed modulation ratio of the output H-bridge power unit module; Module M3: Calculates the inductive reactance based on the system frequency and the inductance value of the connecting inductor, and calculates the constant based on the effective value of the AC side voltage of the output H-bridge power unit module and the inductive reactance; Module M4: Based on the given active power reference value, reactive power reference value, constant, and the effective value of the AC side voltage of the output H-bridge power unit module, establish the power transfer equation and solve in reverse the effective value and phase of the AC side voltage of the input H-bridge power unit module; Module M5: Calculates the modulation ratio of the input H-bridge power unit module based on the effective value of the AC side voltage and the DC side voltage of the input H-bridge power unit module; Module M6: Based on the phase angle of the output H-bridge power unit module and the phase of the input H-bridge power unit module, it generates modulation waveforms for the output H-bridge power unit module and the input H-bridge power unit module to control the active and reactive power transmitted between the two H-bridge power unit modules.

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