Inverter common-mode voltage injection control method and apparatus

Abstract

The application discloses an inverter common-mode voltage injection control method and device. The method and device calculate the common-mode voltage of a DPWM mode according to a three-phase port voltage and an output power instruction (S202), calculate the common-mode voltage of an MPC modulation mode according to a DC bus voltage, the three-phase port voltage and the output power instruction (S204), determine a modulation ratio according to a phase voltage peak maximum of the three-phase port voltage, the DC bus voltage and a power factor of the output power instruction (S206), and generate a common-mode injection voltage according to the common-mode voltage of the DPWM mode, the modulation ratio and the common-mode voltage of the MPC modulation mode (S208), so that the common-mode voltage of various modulation modes used for generating the common-mode injection voltage is adjusted according to the real-time state of the inverter, the flexibility of the inverter under different operation conditions is facilitated, and the requirements of a smaller DC bus capacitor ripple current and a smaller switching loss are simultaneously considered.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a method and apparatus for controlling common-mode voltage injection in inverters. Background Technology

[0002] Photovoltaic inverters, wind power converters, frequency converters, and new energy vehicles all require DC-to-AC converters, also known as inverters. With the development of power electronics technology, inverters with semiconductor switching devices, such as three-phase inverters, especially three-phase multi-level inverters (with more than two output levels), have been widely used. Compared to two-level inverters, three-level inverters have advantages such as more output levels, lower voltage stress, lower ripple current, and better harmonic characteristics, thus finding widespread application in the power electronics field, especially in frequency converters and photovoltaic inverters. Three-phase three-level inverters typically use semiconductor switching devices to achieve DC-to-AC conversion. Taking a typical three-phase bridge inverter circuit structure as an example, the semiconductor switch of each bridge arm is turned on for half a cycle in a sinusoidal period. The three bridge arms conduct alternately with a 120-degree conduction angle difference, resulting in an output voltage waveform that approximates a sine wave. Recently, Model Predictive Control (MPC) has been applied to control power converters. MPC (Multi-Phase Control) offers advantages such as discreteness and fast dynamic response. Combined with rapidly developing digital signal processing technology, it is used to control three-phase inverters. The basic concept of MPC is to use a model of a system to predict the future behavior of the controlled variable in the prediction space, for example, by optimizing a user-defined cost function to provide a sequence of control actions.

[0003] Currently, three-phase three-level inverters face the problem of large ripple current in the DC bus capacitors. Specifically, the DC bus of a three-phase three-level inverter refers to the positive and negative terminals connected on the DC side of the inverter; the DC bus capacitor refers to the capacitor located between the DC buses of the inverter; to output a zero-level signal, a neutral line is drawn between the positive and negative bus capacitors; during the switching process of power electronic switching devices, ripple current flows from the neutral line into the positive and negative bus capacitors; the DC bus capacitor ripple current refers to the ripple current flowing through the DC bus capacitor (i.e., the current with the frequency components remaining after removing the DC component). For the DC bus capacitor, if the ripple current flowing through it is too large, it will lead to capacitor losses and increased temperature, thus seriously affecting the capacitor's lifespan. Therefore, to avoid excessive ripple current flowing through a single bus capacitor, the common practice is to increase the number of bus capacitors, thereby reducing the ripple current flowing through each bus capacitor, but this significantly increases costs. In addition, high-order harmonic components in ripple current or voltage can cause changes in current or voltage amplitude, which may lead to breakdown. Furthermore, since they are AC components, they will dissipate in the capacitor. If the ripple component of the current is too large, exceeding the capacitor's maximum allowable ripple current, it can even cause the capacitor to burn out.

[0004] In existing technologies, common-mode voltage injection control methods are commonly used to control the magnitude and high-order harmonic components of the DC bus capacitor ripple current, thereby helping to reduce the number of bus capacitors and lower costs. Existing common-mode voltage injection control methods are divided into continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM). CPWM can be further divided into non-common-mode voltage injection, triangular wave common-mode voltage injection, and third harmonic common-mode voltage injection. However, with CPWM, the ripple current flowing through the bus capacitor is relatively small, but because the three phases of the inverter circuit have switching devices operating in each control cycle, the switching losses of the power electronic switching devices increase, thus affecting efficiency. With DPWM, because only two phases of the three phases have switching devices operating in each control cycle, the switching losses of the power electronic switching devices are smaller, but the ripple current flowing through the bus capacitor is relatively large, requiring more bus capacitors and increasing costs. Therefore, existing common-mode voltage injection control methods cannot simultaneously meet the requirements of low DC bus capacitor ripple current and low switching losses. Summary of the Invention

[0005] The purpose of this application is to provide a common-mode voltage injection control method and apparatus for an inverter. This method and apparatus calculates the common-mode voltage using discontinuous pulse width modulation (DPWM) based on the three-phase port voltage and the output power command; predicts and controls the common-mode voltage using MPC modulation based on the DC bus voltage, the three-phase port voltage, and the output power command; determines the modulation ratio based on the maximum peak value of the phase voltages of the three-phase port voltages, the DC bus voltage, and the power factor of the output power command; and generates a common-mode injection voltage based on the common-mode voltage of the DPWM modulation, the modulation ratio, and the common-mode voltage of the MPC modulation. This allows for adjustment of the common-mode voltage and modulation ratio of various modulation methods used to generate the common-mode injection voltage according to the real-time state of the inverter. This improves flexibility under different operating conditions of the inverter, reduces the number of bus capacitors and lowers inverter costs, and also reduces switching losses of the inverter's switching devices. Furthermore, it helps to simultaneously meet the requirements of low DC bus capacitor ripple current and low switching losses.

[0006] In a first aspect, embodiments of this application provide a common-mode voltage injection control method applied to a three-phase three-level inverter. The common-mode voltage injection control method includes: obtaining the DC bus voltage and three-phase port voltages of the three-phase three-level inverter; calculating the common-mode voltage of discontinuous pulse width modulation (DPWM) based on the three-phase port voltages and the output power command; calculating the common-mode voltage of model predictive control (MPC) modulation based on the DC bus voltage, the three-phase port voltages, and the output power command; and determining the modulation based on the maximum value of the phase voltage peak of the three-phase port voltages, the DC bus voltage, and the power factor of the output power command. The common-mode injection voltage is generated based on the common-mode voltage of the DPWM modulation method, the modulation ratio, and the common-mode voltage of the MPC modulation method. The common-mode injection voltage is used to generate the output voltage modulation wave of the three-phase three-level inverter. The common-mode injection voltage includes a first part and a second part. The first part of the common-mode injection voltage uses the common-mode voltage of the DPWM method, and the second part of the common-mode injection voltage uses the common-mode voltage of the MPC modulation method. The ratio of the first part of the common-mode injection voltage to the second part of the common-mode injection voltage is determined according to the modulation ratio.

[0007] The technical solution described in the first aspect calculates the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltage and the output power command; calculates the common-mode voltage of the MPC modulation mode based on the DC bus voltage, the three-phase port voltage, and the output power command; determines the modulation ratio based on the maximum value of the phase voltage peak of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command; and generates a common-mode injection voltage based on the common-mode voltage of the DPWM mode, the modulation ratio, and the common-mode voltage of the MPC modulation mode. This achieves the adjustment of the common-mode voltage and modulation ratio of various modulation modes used to generate the common-mode injection voltage according to the real-time state of the inverter. This facilitates flexibility under different operating conditions of the inverter, reduces the number of bus capacitors and lowers the cost of the inverter, and also reduces the switching losses of the inverter's switching devices. Furthermore, it helps to simultaneously meet the requirements of lower DC bus capacitor ripple current and lower switching losses.

[0008] According to the first aspect, in one possible implementation, the common-mode voltage injection control method further includes: calculating a common-mode voltage of a continuous pulse width modulation (CPWM) mode based on the common-mode voltage of the DPWM mode and the common-mode voltage of the MPC modulation mode, wherein the common-mode voltage of the CPWM mode is between the common-mode voltage of the DPWM mode and the common-mode voltage of the MPC modulation mode; and calculating the common-mode injection voltage based on the common-mode voltage of the DPWM mode, the modulation ratio, the common-mode voltage of the MPC modulation mode, and the common-mode voltage of the CPWM mode, wherein the common-mode injection voltage further includes a third part, the third part of the common-mode injection voltage adopts the common-mode voltage of the CPWM mode, and the ratio of the third part of the common-mode injection voltage relative to the first part and the second part of the common-mode injection voltage is determined according to the modulation ratio.

[0009] Thus, by employing DPWM, MPC, and CPWM modulation methods, and adjusting the modulation ratio and common-mode injection voltage based on real-time data acquisition, the requirement of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses can be achieved.

[0010] According to the first aspect, in one possible implementation, the common-mode voltage injection control method further includes: dividing a single-cycle time period of the three-phase port voltage into a first part, a second part, and a third part, wherein the proportions of the first part, the second part, and the third part of the single-cycle time period relative to the single-cycle time period are respectively determined according to the modulation ratio; and injecting the first part of the common-mode injection voltage into the first part, the second part, and the third part of the single-cycle time period, respectively, the second part and the third part of the common-mode injection voltage to generate a single cycle of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the single cycle of the output voltage modulation wave.

[0011] Thus, by dividing a single cycle time period and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously employ DPWM, MPC, and CPWM modes within a single cycle time period, and generate a single cycle of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by cycling through the single cycle, achieving the desired control effect. This fulfills the requirement of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses.

[0012] According to the first aspect, in one possible implementation, dividing the single-cycle time period of the three-phase port voltage into the first part, the second part, and the third part includes: sequentially dividing the single-cycle time period of the three-phase port voltage into six consecutive and non-overlapping sectors, wherein each of the six sectors is sequentially divided into four consecutive and non-overlapping sub-sectors; relative to the four sub-sectors of each of the six sectors, the common-mode voltage injection control method further includes: sequentially labeling the four sub-sectors as a first sub-sector, a second sub-sector, a third sub-sector, and a fourth sub-sector; and determining the proportions of the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector relative to the single-cycle time period according to the modulation ratio, wherein the first sub-sector corresponds to the first part of the single-cycle time period, the third sub-sector corresponds to the second part of the single-cycle time period, and the second and fourth sub-sectors correspond to the third part of the single-cycle time period.

[0013] Thus, by dividing a single cycle time period into six sectors, each sector into four sub-sectors, and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously employ DPWM, MPC, and CPWM modes within a single cycle time period, and generate a single cycle of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by the cycle of the single cycle, achieving the desired control effect. This achieves the requirement of simultaneously considering a small DC bus capacitor ripple current and a small switching loss.

[0014] According to the first aspect, in one possible implementation, the duration of the second sub-sector is the same as the duration of the fourth sub-sector, and the common-mode voltage injection control method further includes: calculating the real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time based on the common-mode voltage of the DPWM mode, the common-mode voltage of the MPC modulation mode, the duration of the second sub-sector, and the real-time time.

[0015] Thus, by dividing a single period into six sectors, each sector into four sub-sectors, and configuring the various parts of the common-mode injection voltage accordingly, and calculating the real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time, the current status of the DC input terminal and the three-phase AC port is collected and fed back in real time. Based on the feedback, the common-mode voltage of the corresponding modulation mode is set, thereby achieving the requirement of simultaneously taking into account the small DC bus capacitor ripple current and the small switching loss.

[0016] According to the first aspect, in one possible implementation, the common-mode voltage injection control method further includes: dividing a plurality of continuous periodic time segments of the three-phase port voltage into a first segment and a second segment, wherein the first segment and the second segment of the plurality of continuous periodic time segments are each composed of one or more continuous periods of the plurality of continuous periodic time segments, and the proportions of the first segment and the second segment of the plurality of continuous periodic time segments relative to the plurality of continuous periodic time segments are determined according to the modulation ratio; and injecting the first portion and the second portion of the common-mode injection voltage into the first segment and the second segment of the plurality of continuous periodic time segments respectively to generate a plurality of continuous periods of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the cyclic generation of the plurality of continuous periods of the output voltage modulation wave.

[0017] Thus, by dividing multiple consecutive periodic time periods and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously use DPWM and MPC modulation methods in multiple consecutive periodic time periods T, and generate multiple consecutive periods of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by the multiple consecutive periods, achieving the desired control effect. This achieves the requirement of simultaneously taking into account a small DC bus capacitor ripple current and a small switching loss.

[0018] According to the first aspect, in one possible implementation, the output power command includes an active power command, characterized in that the calculation of the common-mode voltage of the MPC modulation method based on the DC bus voltage, the three-phase port voltage, and the output power command includes: determining the minimum value of the three-phase port voltage and a first phase voltage corresponding to the minimum value, the maximum value of the three-phase port voltage and a second phase voltage corresponding to the maximum value, a first phase current in phase with the first phase voltage, and a second phase current in phase with the second phase voltage in the three-phase port current of the three-phase three-level inverter; calculating a first feasible value of the common-mode voltage based on the active power command, the DC bus voltage, the first phase voltage corresponding to the minimum value, and the first phase current; and calculating a first feasible value of the common-mode voltage based on the active power command, the DC bus voltage, the second phase voltage corresponding to the maximum value, and the first phase voltage corresponding to the first phase voltage. The second phase current is used to calculate a second feasible value for the common-mode voltage; the first feasible value and the second feasible value of the common-mode voltage are subjected to amplitude limiting processing to obtain an upper limit value and a lower limit value for the common-mode injection voltage, respectively; based on the upper limit value of the common-mode injection voltage, the three-phase port voltage and the three-phase port current are used to calculate a first real-time value of the DC bus capacitor ripple current; based on the lower limit value of the common-mode injection voltage, the three-phase port voltage and the three-phase port current are used to calculate a second real-time value of the DC bus capacitor ripple current; one of the upper limit value and the lower limit value of the common-mode injection voltage corresponding to the smaller of the absolute values ​​of the first and second real-time values ​​of the DC bus capacitor ripple current is selected as the optimal common-mode voltage; and the common-mode voltage of the MPC modulation method is calculated based on the optimal common-mode voltage and a preset scaling factor.

[0019] Thus, by calculating the common-mode voltage of the MPC modulation mode based on the DC bus voltage, the three-phase port voltage, and the output power command, the current status of the DC input terminal and the three-phase port on the AC side is collected and fed back in real time. Based on the feedback, the common-mode voltage of the corresponding modulation mode is set, thereby achieving the requirement of simultaneously taking into account the small DC bus capacitor ripple current and the small switching loss.

[0020] According to the first aspect, in one possible implementation, the output power command includes an active power command and a reactive power command, and determining the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command includes: calculating the power factor of the output power command based on the active power command and the reactive power command; and determining the modulation ratio based on the ratio of the maximum peak value of the phase voltage of the three-phase port voltage to the DC bus voltage and the power factor.

[0021] Thus, by determining the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command, the modulation ratio can be adjusted according to the real-time acquired data. Furthermore, the output power command and the corresponding common-mode voltage and modulation ratio of the modulation mode are taken into account, thereby achieving the goal of simultaneously meeting the requirements of small DC bus capacitor ripple current and small switching losses.

[0022] Secondly, embodiments of this application provide a common-mode voltage injection control device applied to a three-phase three-level inverter. The common-mode voltage injection control device includes a memory and a processor. The memory stores a computer program, and the processor performs the following operations according to the computer program: obtaining the DC bus voltage and three-phase port voltages of the three-phase three-level inverter; calculating the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltages and the output power command; calculating the model prediction control of the common-mode voltage of the MPC modulation mode based on the DC bus voltage, the three-phase port voltages, and the output power command; and calculating the DC bus voltage based on the maximum value of the phase voltage peak of the three-phase port voltages. The modulation ratio is determined by the line voltage and the power factor of the output power command; and a common-mode injection voltage is generated based on the common-mode voltage of the DPWM mode, the modulation ratio, and the common-mode voltage of the MPC modulation mode, wherein the common-mode injection voltage is used to generate the output voltage modulation wave of the three-phase three-level inverter, the common-mode injection voltage includes a first part and a second part, the first part of the common-mode injection voltage adopts the common-mode voltage of the DPWM mode, the second part of the common-mode injection voltage adopts the common-mode voltage of the MPC modulation mode, and the ratio of the first part of the common-mode injection voltage to the second part of the common-mode injection voltage is determined according to the modulation ratio.

[0023] The technical solution described in the second aspect calculates the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltage and the output power command; calculates the common-mode voltage of the MPC modulation mode based on the DC bus voltage, the three-phase port voltage, and the output power command; determines the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command; and generates a common-mode injection voltage based on the common-mode voltage of the DPWM mode, the modulation ratio, and the common-mode voltage of the MPC modulation mode. This enables the adjustment of the common-mode voltage and modulation ratio of various modulation modes used to generate the common-mode injection voltage according to the real-time state of the inverter. This facilitates flexibility under different operating conditions of the inverter, reduces the number of bus capacitors and lowers inverter costs, and also reduces the switching losses of the inverter's switching devices. Furthermore, it helps to simultaneously meet the requirements of lower DC bus capacitor ripple current and lower switching losses.

[0024] According to the second aspect, in one possible implementation, the processor further performs: calculating a common-mode voltage of a continuous pulse width modulation (CPWM) mode based on the common-mode voltage of the DPWM mode and the common-mode voltage of the MPC modulation mode, wherein the common-mode voltage of the CPWM mode is between the common-mode voltage of the DPWM mode and the common-mode voltage of the MPC modulation mode; and calculating a common-mode injection voltage based on the common-mode voltage of the DPWM mode, the modulation ratio, the common-mode voltage of the MPC modulation mode, and the common-mode voltage of the CPWM mode, wherein the common-mode injection voltage further includes a third portion, the third portion of the common-mode injection voltage adopting the common-mode voltage of the CPWM mode, and the ratios of the third portion of the common-mode injection voltage relative to the first portion and the second portion of the common-mode injection voltage are determined according to the modulation ratio.

[0025] Thus, by employing DPWM, MPC, and CPWM modulation methods, and adjusting the modulation ratio and common-mode injection voltage based on real-time data acquisition, the requirement of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses can be achieved.

[0026] According to the second aspect, in one possible implementation, the processor further performs: dividing a single-cycle time period of the three-phase port voltage into a first part, a second part, and a third part, wherein the proportions of the first part, the second part, and the third part of the single-cycle time period relative to the single-cycle time period are respectively determined according to the modulation ratio; and injecting the first part of the common-mode injection voltage into the first part, the second part, and the third part of the single-cycle time period, respectively, to generate a single cycle of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the single cycle of the output voltage modulation wave.

[0027] Thus, by dividing a single cycle time period and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously employ DPWM, MPC, and CPWM modes within a single cycle time period, and generate a single cycle of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by cycling through the single cycle, achieving the desired control effect. This fulfills the requirement of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses.

[0028] According to the second aspect, in one possible implementation, dividing the single-cycle time period of the three-phase port voltage into the first part, the second part, and the third part includes: sequentially dividing the single-cycle time period of the three-phase port voltage into six consecutive and non-overlapping sectors, wherein each of the six sectors is sequentially divided into four consecutive and non-overlapping sub-sectors; relative to the four sub-sectors of each of the six sectors, the common-mode voltage injection control method further includes: sequentially labeling the four sub-sectors as a first sub-sector, a second sub-sector, a third sub-sector, and a fourth sub-sector; and determining the proportions of the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector relative to the single-cycle time period according to the modulation ratio, wherein the first sub-sector corresponds to the first part of the single-cycle time period, the third sub-sector corresponds to the second part of the single-cycle time period, and the second and fourth sub-sectors correspond to the third part of the single-cycle time period.

[0029] Thus, by dividing a single cycle time period into six sectors, each sector into four sub-sectors, and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously employ DPWM, MPC, and CPWM modes within a single cycle time period, and generate a single cycle of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by the cycle of the single cycle, achieving the desired control effect. This achieves the requirement of simultaneously considering a small DC bus capacitor ripple current and a small switching loss.

[0030] According to the second aspect, in one possible implementation, the duration of the second sub-sector is the same as the duration of the fourth sub-sector, and the processor further performs the following: calculating a real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time based on the common-mode voltage of the DPWM mode, the common-mode voltage of the MPC modulation mode, the duration of the second sub-sector, and the real-time time.

[0031] Thus, by dividing a single period into six sectors, each sector into four sub-sectors, and configuring the various parts of the common-mode injection voltage accordingly, and calculating the real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time, the current status of the DC input terminal and the three-phase AC port is collected and fed back in real time. Based on the feedback, the common-mode voltage of the corresponding modulation mode is set, thereby achieving the requirement of simultaneously taking into account the small DC bus capacitor ripple current and the small switching loss.

[0032] According to the second aspect, in one possible implementation, the processor further performs: dividing a plurality of consecutive periodic time segments of the three-phase port voltage into a first segment and a second segment, wherein the first segment and the second segment of the plurality of consecutive periodic time segments are each composed of one or more consecutive periods of the plurality of consecutive periodic time segments, and the proportions of the first segment and the second segment of the plurality of consecutive periodic time segments relative to the plurality of consecutive periodic time segments are determined according to the modulation ratio; and injecting the first portion and the second portion of the common-mode injection voltage into the first segment and the second segment of the plurality of consecutive periodic time segments respectively to generate a plurality of consecutive periods of the output voltage modulation wave, wherein the output voltage modulation wave is formed by cyclically generating the plurality of consecutive periods of the output voltage modulation wave.

[0033] Thus, by dividing multiple consecutive periodic time periods and configuring the various parts of the common-mode injection voltage accordingly, it is possible to simultaneously use DPWM and MPC modulation methods in multiple consecutive periodic time periods T, and generate multiple consecutive periods of the corresponding output voltage modulation wave. The waveform of the corresponding output voltage modulation wave is then formed by the multiple consecutive periods, achieving the desired control effect. This achieves the requirement of simultaneously taking into account a small DC bus capacitor ripple current and a small switching loss.

[0034] According to the second aspect, in one possible implementation, the output power command includes an active power command, and the calculation of the common-mode voltage of the MPC modulation method based on the DC bus voltage, the three-phase port voltage, and the output power command includes: determining the minimum value of the three-phase port voltage and the first phase voltage corresponding to the minimum value, the maximum value of the three-phase port voltage and the second phase voltage corresponding to the maximum value, the first phase current in phase with the first phase voltage, and the second phase current in phase with the second phase voltage in the three-phase port current of the three-phase three-level inverter; calculating a first feasible value of the common-mode voltage based on the active power command, the DC bus voltage, the first phase voltage corresponding to the minimum value, and the first phase current; and calculating a first feasible value of the common-mode voltage based on the active power command, the DC bus voltage, the second phase voltage corresponding to the maximum value, and the second phase current. The phase current is used to calculate a second feasible value for the common-mode voltage; the first feasible value and the second feasible value of the common-mode voltage are subjected to amplitude limiting processing to obtain an upper limit value and a lower limit value for the common-mode injection voltage, respectively; based on the upper limit value of the common-mode injection voltage, the three-phase port voltage and the three-phase port current are used to calculate a first real-time value of the DC bus capacitor ripple current; based on the lower limit value of the common-mode injection voltage, the three-phase port voltage and the three-phase port current are used to calculate a second real-time value of the DC bus capacitor ripple current; one of the upper limit value and the lower limit value of the common-mode injection voltage corresponding to the smaller of the absolute values ​​of the first and second real-time values ​​of the DC bus capacitor ripple current is selected as the optimal common-mode voltage; and the common-mode voltage of the MPC modulation method is calculated based on the optimal common-mode voltage and a preset scaling factor.

[0035] Thus, by calculating the common-mode voltage of the MPC modulation mode based on the DC bus voltage, the three-phase port voltage, and the output power command, the current status of the DC input terminal and the three-phase port on the AC side is collected and fed back in real time. Based on the feedback, the common-mode voltage of the corresponding modulation mode is set, thereby achieving the requirement of simultaneously taking into account the small DC bus capacitor ripple current and the small switching loss.

[0036] According to the second aspect, in one possible implementation, the output power command includes an active power command and a reactive power command, characterized in that determining the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command includes: calculating the power factor of the output power command based on the active power command and the reactive power command; and determining the modulation ratio based on the ratio of the maximum peak value of the phase voltage of the three-phase port voltage to the DC bus voltage and the power factor.

[0037] Thus, by determining the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command, the modulation ratio can be adjusted according to the real-time acquired data. Furthermore, the output power command and the corresponding common-mode voltage and modulation ratio of the modulation mode are taken into account, thereby achieving the goal of simultaneously meeting the requirements of small DC bus capacitor ripple current and small switching losses. Attached Figure Description

[0038] To illustrate the technical solutions in the embodiments or background art of this application, the accompanying drawings used in the embodiments or background art of this application will be described below.

[0039] Figure 1 A schematic diagram of a photovoltaic power generation system including an inverter common-mode voltage injection control device is provided for an embodiment of this application.

[0040] Figure 2 This is a flowchart illustrating one implementation of an inverter common-mode voltage injection control method provided in an embodiment of this application.

[0041] Figure 3 This is a flowchart illustrating another implementation of the inverter common-mode voltage injection control method provided in this application embodiment.

[0042] Figure 4 This is a flowchart illustrating another implementation of the inverter common-mode voltage injection control method provided in this application embodiment. Detailed Implementation

[0043] This application provides a common-mode voltage injection control method and apparatus for inverters. Specific application scenarios for this method and apparatus include, but are not limited to, applications requiring control of the DC bus capacitor ripple current and suppression of its high-order harmonic components, such as photovoltaic inverters, wind power converters, and frequency converters. This common-mode voltage injection control method and apparatus uses a three-phase three-level inverter as an example, but it may also be applicable to other types of inverters. This inverter common-mode voltage injection control method and apparatus calculates the common-mode voltage of discontinuous pulse width modulation (DPWM) based on the three-phase port voltage and output power command; predicts and controls the common-mode voltage of MPC modulation based on the DC bus voltage, the three-phase port voltage, and the output power command; determines the modulation ratio based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command; and generates the common-mode injection voltage based on the common-mode voltage of the DPWM modulation, the modulation ratio, and the common-mode voltage of the MPC modulation. This allows for adjustment of the common-mode voltage and modulation ratio of various modulation methods used to generate the common-mode injection voltage according to the real-time state of the inverter. This improves flexibility under different operating conditions of the inverter, reduces the number of bus capacitors and lowers inverter costs, and reduces switching losses of the inverter's switching devices. Furthermore, it helps to simultaneously meet the requirements of low DC bus capacitor ripple current and low switching losses.

[0044] The embodiments of this application can be adjusted and improved according to specific application environments, and no specific limitations are made here.

[0045] To enable those skilled in the art to better understand the present application, the embodiments of the present application will be described below with reference to the accompanying drawings.

[0046] Please see Figure 1 , Figure 1 This is a schematic diagram of a photovoltaic power generation system including an inverter common-mode voltage injection control device, provided as an embodiment of this application. Figure 1As shown, the photovoltaic power generation system 100 includes a DC-side unit 102, a DC-to-AC converter 104, an AC-side unit 106, a data acquisition unit 108, a common-mode voltage injection control device 110, and a drive signal generator 112. One end of the DC-to-AC converter 104 is electrically connected to the DC-side unit 102 as a DC input terminal, and the other end is electrically connected to the AC-side unit 104 as an AC output terminal. The DC-to-AC converter 104 operably transfers energy from the DC-side unit 102 to the AC-side unit 106, realizing the conversion from DC to AC. In this embodiment, the DC-to-AC converter 104 is a three-phase three-level inverter. The data acquisition unit 108 operably acquires data in real time from the DC input terminal and the AC output terminal of the converter 104 and sends the acquired data to the common-mode voltage injection control device 110. The common-mode voltage injection control device 110 calculates the common-mode injection voltage based on the received data. The drive signal generator 112 injects the common-mode injection voltage into the three-phase three-level inverter to generate the output voltage modulation wave of the three-phase three-level inverter. The drive signal generator 112 is configured to generate corresponding drive signals or control signals based on the common-mode injection voltage to control the AC output of the three-phase three-level inverter.

[0047] It is understood that the structures illustrated in the embodiments of this application do not constitute a specific limitation on the photovoltaic power generation system 100. In other embodiments of this application, the photovoltaic power generation system 100 may include more or fewer components than illustrated, or combine some components, or split some components, or have different component arrangements. For example, the DC-to-AC converter 104 described above may be a separately configured inverter, while the data acquisition unit 108, the common-mode voltage injection control device 110, and the drive signal generator 112 are all independent devices; the DC-to-AC converter 104 may also integrate the data acquisition unit 108 and the drive signal generator 112, that is, the common-mode voltage injection control device 110 receives the acquired data from the converter 104 and then calculates the common-mode injection voltage, and the converter 104 generates the output voltage modulation wave accordingly.

[0048] The output voltage of a photovoltaic power generation system 100 can be controlled using Pulse Wide Modulation (PWM). The PWM method is described in detail below. According to sampling control theory, narrow pulses with equal impulse but different shapes have an equivalent effect on the output response waveform. Therefore, a series of narrow pulses of equal width but unequal amplitude can be used to approximate a sinusoidal waveform. For example, a sine wave half-wave can be divided into equal parts and sampled to obtain a waveform composed of multiple interconnected pulses. These pulses have equal widths but unequal amplitudes and change according to a sinusoidal law. Then, the same number of rectangular waves of equal amplitude but unequal width are used to replace these pulses to achieve the equivalent effect. The PWM method refers to a control method that obtains an equivalent output containing the desired waveform by modulating the width (duty cycle) of these rectangular waves according to certain rules. In inverter circuits with semiconductor switching devices, a corresponding drive signal can be generated based on a specific modulation signal to control the switching action and on / off state of the semiconductor switching devices, thereby ensuring that the equivalent output contains the desired waveform and achieving the desired control effect.

[0049] PWM (Pulse Width Modulation) is divided into CPWM (Continuous Voltage Pulse) and DPWM (Discontinuous Voltage Pulse) modes. CPWM refers to a pulse level switch within each pulse cycle, meaning the pulses are continuous. The corresponding switching device control method for CPWM performs a switching action within each switching cycle. DPWM refers to multiple consecutive pulse cycles without a level switch, meaning the pulses are discontinuous. The corresponding switching device control method for DPWM maintains a constant on or off state for a certain switching period or multiple switching cycles, without any switching action. CPWM can be further divided into Sinusoidal Pulse Width Modulation (SPWM), Space Vector Pulse Width Modulation (SVPWM), and Third Harmonic Pulse Width Modulation (THIPWM). SPWM uses a series of rectangular pulse waves of equal amplitude but unequal width, equivalent to a sine wave, and compares a reference analog signal with a high-frequency carrier waveform to achieve an equivalent sine wave output waveform. THIPWM refers to superimposing a common-mode third harmonic signal onto the reference waveform of each phase, making the phase voltage modulation signal a saddle-shaped wave. When synthesizing the line voltage, the third harmonics between the phase lines cancel each other out, thus achieving better DC voltage utilization. SVPWM is based on the eight possible switching state combinations of the three switching devices in a three-phase inverter. Two of these states correspond to all three switches being either open or all three being closed, which is a short-circuit state from the output side and can be considered as zero vectors. The remaining six states can be considered as dividing the dq space into six equal spatial vectors, each spatial vector corresponding to a specific angular position. Any voltage vector can be equivalently represented by two of these six spatial vectors, thus SVPWM can obtain a more ideal third harmonic signal. DPWM waveforms are generally sinusoidal. It typically achieves this by simultaneously using two zero vectors and other non-zero vectors to ensure that there is a 60-degree interval at the peak of each of the positive and negative half-cycles of the output voltage without switching action, which is one-third of the duty cycle. Based on the space vector allocation strategy and the arrangement of intervals without switching operations, DPWM can be further divided into DPWMMIN, DPWMM0, DPWMM1, DPWMM2, DPWMM3, DPWMMAX, and GDPWM. MPC modulation refers to predicting the output voltage using the MPC method and controlling it through a specific modulation method, such as Model Predictive Control Pulse Wide Modulation (MPC-PWM).

[0050] Please continue reading. Figure 1The photovoltaic power generation system 100 can employ CPWM, DPWM, or MPC modulation, or any possible combination thereof. For example, the photovoltaic power generation system 100 can use a combination of DPWM and MPC modulation, or a combination of CPWM, DPWM, and MPC modulation. The DPWM modulation method used by the photovoltaic power generation system 100 can include DPWMMIN, DPWMM0, DPWMM1, DPWMM2, DPWMM3, DPWMMAX, and GDPWM, or any possible combination thereof. The CPWM modulation method used by the photovoltaic power generation system 100 can include SPWM, SVPWM, THIPWM, or any possible combination thereof. These can be determined based on the specific application environment and are not specifically limited here.

[0051] The DC-side unit 102 of the photovoltaic power generation system 100 is connected to a photovoltaic power generation module (not shown) and receives DC power generated by the photovoltaic power generation module. A photovoltaic power generation module refers to a device that converts solar radiation energy into DC power energy based on the solar photovoltaic effect, such as a solar panel. In some exemplary embodiments, the DC input terminal 104 may also be connected to an energy storage element such as a battery, fuel cell, or solar cell. The source providing the DC input may also include other accessories to provide more functionality, such as a programmable DC power supply and a regenerative DC electronic load. In one possible implementation, the source of the DC input is other types of new energy power generation systems, such as a DC voltage source generated by a wind turbine or hydroelectric generator. These can be adjusted and improved according to the specific application environment, and are not specifically limited here.

[0052] In this embodiment, the DC-to-AC converter 104 is a three-phase three-level inverter, including a DC bus capacitor composed of positive and negative bus capacitors, and has a voltage-type inverter circuit and receives DC input from a corresponding DC voltage source. Figure 1 As shown, the DC bus voltage U between the positive and negative terminals of the DC input terminal can be collected at the DC input terminal of the DC-to-AC converter 104. bus At the AC output terminal, three line voltages and three phase voltages U can be collected. a U b , and U c(That is, the three-phase port voltage) and the corresponding three-phase port current. The DC-to-AC converter 104 can be an inverter circuit with semiconductor switching devices and a bridge arm structure. Each bridge arm has a corresponding semiconductor switching device, and the output AC power can be affected by controlling the switching action and on / off state of each semiconductor switching device. Among them, the semiconductor switching devices can be giant transistors (GTRs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), or other suitable devices. The specific topology of the inverter circuit, such as the setting of semiconductor switching transistors and bridge arms, can refer to common NPC and T types, as long as it can meet the control requirements. That is, the photovoltaic power generation system 100 can calculate the common mode injection voltage based on the collected data and then generate the corresponding drive signal to control the switching action and on / off of each semiconductor switching device of the converter 104, so that the equivalent output of the converter 104 contains the required waveform. These can be determined according to the specific application environment, and no specific limitation is made here.

[0053] The DC-to-AC converter 104 outputs AC power to the AC-side unit 106. The AC-side unit 106 can directly output power to a load or return power to the grid; that is, the photovoltaic power generation system 100 can be used with either a passive or active inverter circuit. The AC-side unit 106 may also include a filter to suppress high-frequency harmonics generated by PWM modulation. The filter can be L-type, LC-type, or LCL-type, or it can be an adjustable filter with adjustable parameters to cope with varying output frequency and equivalent impedance. This filter can be integrated into the DC-to-AC converter 104 or separately located in the AC-side unit 106. These options depend on the specific application environment and are not specifically limited here.

[0054] The data acquisition unit 108 can realize real-time detection and acquisition of voltage phase and frequency at the AC output terminal through phase-locked loop technology, such as a three-phase software phase-locked loop; the data acquisition unit 108 can also realize tracking of a given signal through dq coordinate transformation technology, such as converting three-phase AC power into two-phase DC power through three-phase dq control; the data acquisition module 108 can also use other suitable technologies to realize real-time data acquisition; these can be determined according to the specific application environment, and no specific limitation is made here.

[0055] The drive signal generator 112 generates corresponding drive or control signals based on the calculated common-mode injection voltage to control the output voltage of the three-phase three-level inverter. The specific method of generating the drive signal depends on the topology of the semiconductor switching devices in the inverter circuit. As long as the control requirements are met, that is, the photovoltaic power generation system 100 can generate corresponding drive signals based on the collected data to control the switching action and on / off state of each semiconductor switching device in the converter 104, so that the equivalent output of the converter 104 contains the required waveform.

[0056] Please continue reading. Figure 1 In some exemplary embodiments, the common-mode voltage injection control device 110 stores a computer program in its memory. In response to the processor executing the computer program, the processor of the common-mode voltage injection control device 110 performs the following operations: obtaining the DC bus voltage and three-phase port voltage of the three-phase three-level inverter; calculating the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltage and the output power command; calculating the common-mode voltage of the model predictive control (MPC) modulation mode based on the DC bus voltage, the three-phase port voltage, and the output power command; and calculating the common-mode voltage of the DC bus voltage and the output power command based on the maximum value of the phase voltage peak of the three-phase port voltage. The power factor of the power command determines the modulation ratio; and a common-mode injection voltage is generated based on the common-mode voltage of the DPWM mode, the modulation ratio, and the common-mode voltage of the MPC modulation mode, wherein the common-mode injection voltage is used to generate the output voltage modulation wave of the three-phase three-level inverter, the common-mode injection voltage includes a first part and a second part, the first part of the common-mode injection voltage adopts the common-mode voltage of the DPWM mode, the second part of the common-mode injection voltage adopts the common-mode voltage of the MPC modulation mode, and the ratio of the first part of the common-mode injection voltage to the second part of the common-mode injection voltage is determined according to the modulation ratio.

[0057] Thus, in some exemplary embodiments, Figure 1 The photovoltaic power generation system 100 shown realizes the adjustment of the common-mode voltage and modulation ratio of various modulation methods used to generate the common-mode injection voltage according to the real-time status of the inverter. This is beneficial for achieving flexibility under different operating conditions of the inverter, reducing the number of bus capacitors and lowering the cost of the inverter, and also reducing the switching losses of the inverter switching devices. In this way, it helps to simultaneously meet the requirements of smaller DC bus capacitor ripple current and smaller switching losses.

[0058] Please see Figure 2 , Figure 2 This is a flowchart illustrating one implementation of an inverter common-mode voltage injection control method provided in an embodiment of this application. Figure 2As shown, the common-mode voltage injection control method includes the following steps.

[0059] Step S200: Obtain the DC bus voltage U of the three-phase three-level inverter. bus and three-phase port voltage U a U b , and U c .

[0060] A three-phase three-level inverter may include a positive DC bus, a negative DC bus, a neutral line, a positive bus capacitor, and a negative bus capacitor. The positive terminal of the three-phase three-level inverter is connected to the positive terminal of the positive bus capacitor, serving as the positive DC bus; the negative terminal of the three-phase three-level inverter is connected to the negative terminal of the negative bus capacitor, serving as the negative DC bus; the neutral line of the three-phase three-level inverter is connected to the negative terminal of the positive bus capacitor and the positive terminal of the negative bus capacitor, serving as the neutral line. Thus, the DC bus voltage U can be sampled between the positive and negative terminals of the DC input of the three-phase three-level inverter. bus A three-phase three-level inverter outputs three-phase AC power from its three-phase output terminals. Therefore, three phase voltages U can be sampled at the three-phase ports on the AC side of the three-phase three-level inverter. a U b , and U c This refers to the three-phase port voltage. The three-phase voltages U a U b , and U c This refers to the voltage between each phase of the three phases at the three-phase port of the AC side and the neutral or zero line. In some exemplary embodiments, the DC-side input terminal of the three-phase three-level inverter is electrically connected to a DC voltage source and has a corresponding voltage-source inverter circuit topology.

[0061] It should be understood that obtaining the three-phase port voltage U a U b , and U c The three-phase port voltage U can be obtained through real-time detection and data acquisition techniques, such as phase-locked loop (PLL) technology, dq coordinate transformation technology, or other suitable techniques. a U b , and U c Alternatively, it can be inferred indirectly, such as by detecting other electrical signals from the inverter. Similarly, the DC bus voltage U can be obtained. bus It can be done through direct detection or indirect methods.

[0062] Step S202: Based on the three-phase port voltage U a U b , and U c And the common-mode voltage U of the DPWM mode is calculated using the output power command. cmvDPWM.

[0063] The output power command includes at least the active power command P. The active power command P refers to the power consumed by the load resistance in one cycle of the inverter circuit. In some exemplary embodiments, the DPWM method can be, for example, DPWMMIN, DPWMM0, DPWMM1, DPWMM2, DPWMM3, DPWMMAX, and GDPWM. The common-mode voltage U of the DPWM method is calculated. cmvDPWM The specific methods can be adopted using appropriate technical means from the existing technology, which will not be elaborated here.

[0064] Step S204: Based on the DC bus voltage U bus The three-phase port voltage U a U b , and U c And the output power command calculates the common-mode voltage U of the MPC modulation mode. cmvMPWM .

[0065] The common-mode voltage of the MPC modulation scheme can be calculated using suitable existing techniques, as long as the real-time acquired DC bus voltage U is used. bus and the three-phase port voltage U a U b , and U c The common-mode voltage U of the final MPC modulation scheme is used as a variable to predict and control the final result. cmvMPWM .

[0066] Step S206: Based on the three-phase port voltage U a U b , and U c The peak value of the phase voltage U acmax The DC bus voltage U bus and the power factor of the output power command Determine the modulation ratio η.

[0067] Among them, the three-phase port voltage U a U b , and U c The maximum value of the peak value U acmax It can be obtained through appropriate technical means in the existing technology, which will not be elaborated here.

[0068] Step S208: Based on the common-mode voltage U of the DPWM method cmvDPWM The modulation ratio η and the common-mode voltage U of the MPC modulation method cmvMPWM Calculate the common-mode injection voltage U cmv .

[0069] Wherein, the common-mode injection voltage U cmv The common-mode injection voltage U is used to inject into the three-phase three-level inverter to generate the output voltage modulation wave of the three-phase three-level inverter. cmv It includes a first part and a second part. The common-mode injection voltage U cmv The first part uses the common-mode voltage U of the DPWM method. cmvDPWM The common-mode injection voltage U cmv The second part uses the common-mode voltage U of the MPC modulation method. cmvMPWM And the common-mode injection voltage U cmv The first portion relative to the common-mode injection voltage U cmv The proportion of the second part is determined according to the modulation ratio η.

[0070] like Figure 2 As shown, the common-mode injection voltage U cmv This is used to control the ripple current of the DC bus capacitor via a common-mode voltage injection control method, that is, by injecting a common-mode voltage U. cmv The corresponding output voltage modulation wave is generated to control the switching action and on / off state of each semiconductor switching device in the three-phase three-level inverter, thereby reducing the bus capacitor ripple current while taking into account the losses of the three-phase three-level inverter. Furthermore, because the common-mode injection voltage U... cmv Based on real-time data collected from the three-phase three-level inverter, this system achieves flexibility to adapt to different operating conditions of the three-phase three-level inverter. In some exemplary embodiments, the generated output voltage modulation wave generates drive or control signals through a controller, microprocessor, or drive module, thereby controlling the switching action and on / off state of each semiconductor switching device in the three-phase three-level inverter.

[0071] exist Figure 2 In the method shown, the DC bus voltage U at the DC input terminal of the three-phase three-level inverter is collected. bus and the three-phase port voltage U on the AC side a U b , and U c And according to the three-phase port voltage U a U b , and U c Calculate the common-mode voltage U in DPWM mode using the output power command. cmvDPWM And according to the DC bus voltage U bus The three-phase port voltage U a U b , and U c And the output power command calculates the common-mode voltage U of the MPC modulation method. cmvMPWMThis enables real-time acquisition and feedback of the current status of the DC input terminal and the three-phase AC port, and allows setting of the common-mode voltage of the corresponding modulation mode based on the feedback. Figure 2 The method shown also utilizes the three-phase port voltage U a U b , and U c The peak value of the phase voltage, the DC bus voltage U bus and the power factor of the output power command The modulation ratio η is determined, thereby enabling the adjustment of the modulation ratio based on real-time acquired data. Figure 2 The method shown also takes into account the output power command and sets the common-mode voltage and modulation ratio for the corresponding modulation scheme accordingly. Figure 2 The method shown also includes the common-mode injection voltage U cmv The first part uses the common-mode voltage U of the DPWM method. cmvDPWM The common-mode injection voltage U cmv The second part uses the common-mode voltage U of the MPC modulation method. cmvMPWM And determine the common-mode injection voltage U according to the modulation ratio η. cmv The first portion relative to the common-mode injection voltage U cmv The proportion of the second part.

[0072] Thus, in Figure 2 The method shown employs DPWM and MPC modulation, and adjusts the modulation ratio η and common-mode injection voltage U based on real-time acquired data. cmv This achieves the goal of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses. In other words, it reduces the number of bus capacitors and inverter costs while also lowering the switching losses of the inverter's switching devices. Furthermore, because the common-mode injection voltage U... cmv It achieves flexibility to adapt to different operating conditions of the three-phase three-level inverter by collecting data from the three-phase three-level inverter in real time.

[0073] Please see Figure 3 , Figure 3 This is a flowchart illustrating another implementation of the inverter common-mode voltage injection control method provided in this application embodiment. Figure 3 As shown, the common-mode voltage injection control method includes the following steps.

[0074] Step S300: Real-time acquisition of the DC bus voltage U of the three-phase three-level inverter bus Three-phase port voltage U a U b , and U cand the three-phase port current I a I b , and I c .

[0075] The three-phase three-level inverter includes a positive DC bus, a negative DC bus, a neutral line, a positive bus capacitor, and a negative bus capacitor. The positive terminal of the three-phase three-level inverter is connected to the positive terminal of the positive bus capacitor, serving as the positive DC bus; the negative terminal of the three-phase three-level inverter is connected to the negative terminal of the negative bus capacitor, serving as the negative DC bus; the neutral line of the three-phase three-level inverter is connected to the negative terminal of the positive bus capacitor and the positive terminal of the negative bus capacitor, serving as the neutral line. Thus, the DC bus voltage U can be sampled between the positive and negative terminals of the DC input of the three-phase three-level inverter. bus A three-phase three-level inverter outputs three-phase AC power from its three-phase output terminals. Therefore, three phase voltages U can be sampled at the three-phase ports on the AC side of the three-phase three-level inverter. a U b , and U c This refers to the three-phase port voltage. The three-phase voltages U a U b , and U c This refers to the voltage between each phase of the three-phase terminal on the AC side and the neutral or neutral line. The three-phase terminal current I... a I b , and I c This refers to the three phases of the AC side three-phase port connected to the three phase voltages U respectively. a U b , and U c Currents in phase.

[0076] In some exemplary embodiments, the DC-side input terminal of the three-phase three-level inverter is electrically connected to a DC voltage source and has a corresponding voltage-source inverter circuit topology; for the three-phase port voltage U a U b , and U c and the three-phase port current I a I b , and I c Data acquisition can be achieved in real time through phase-locked loop technology, dq coordinate transformation technology, or other suitable technical means.

[0077] Step S302: Based on the three-phase port voltage U a U b , and U c And the common-mode voltage U of the DPWM mode is calculated using the output power command. cmvDPWM .

[0078] The output power command includes an active power command P and a reactive power command Q. In some exemplary embodiments, the DPWM mode can be, for example, DPWMMIN, DPWMM0, DPWMM1, DPWMM2, DPWMM3, DPWMMAX, and GDPWM. The common-mode voltage U of the DPWM mode is calculated. cmvDPWM The specific methods can be adopted using appropriate technical means from the existing technology, which will not be elaborated here.

[0079] Step S304: Based on the DC bus voltage U bus The three-phase port voltage U a U b , and U c The three-phase port current I a I b , and I c And the output power command calculates the common-mode voltage U of the MPC modulation mode. cmvMPWM .

[0080] Specifically, step S304 includes the following details:

[0081] First, calculate the DC current I according to the following formula (1). dc :

[0082]

[0083] Where P is the active power command of the output power command, and U bus This is the DC bus voltage.

[0084] Then, determine the three-phase port voltage U. a U b , and U c The minimum value and the first phase voltage u corresponding to the minimum value min The three-phase port voltage U a U b , and U c The maximum value and the second phase voltage u corresponding to the maximum value max The three-phase port current I of the three-phase three-level inverter a I b , and I c The voltage u of the first phase min The first phase current i in phase min and the second phase voltage u max The second phase current i in phase max .

[0085] Then, according to the following formula (2), based on the active power command P, the DC bus voltage Ubus The first phase voltage u corresponding to the minimum value min and the first phase current i min Calculate the first feasible value u of the common-mode voltage. cmv1 According to the following formula (3), based on the active power command P, the DC bus voltage U bus The second phase voltage u corresponding to the maximum value max and the second phase current i max Calculate the second feasible value u of the common-mode voltage. cmv2 .

[0086]

[0087]

[0088] The DC current I can be obtained according to formula (1). dc ;u cmv1 The first feasible value for common-mode voltage, u cmv2 This is the second feasible value for the common-mode voltage.

[0089] Then, for the first feasible value u of the common-mode voltage cmv1 and the second feasible value u of the common-mode voltage cmv2 Limiting is performed to obtain the upper limit value of the common-mode injection voltage u. cmv1lmt and common-mode injection voltage lower limit u cmv2lmt .

[0090] Then, according to formula (4), based on the upper limit value of the common-mode injection voltage u cmv1lmt The three-phase port voltage U a U b , and U c and the three-phase port current I a I b , and I c Calculate the first real-time value i of the DC bus capacitor ripple current. cap1 According to formula (5), based on the lower limit value of the common-mode injection voltage u cmv2lmt The three-phase port voltage U a U b , and U c and the three-phase port current I a I b , and I c Calculate the second real-time value i of the DC bus capacitor ripple current. cap2 .

[0091]

[0092]

[0093] Among them, i cap1 i is the first real-time value of the DC bus capacitor ripple current. cap2 This is the second real-time value of the DC bus capacitor ripple current.

[0094] Then, select the first real-time value i of the DC bus capacitor ripple current. cap1 absolute value i cap1abs and the second real-time value i of the DC bus capacitor ripple current cap2 absolute value i cap2abs The smaller of the corresponding upper limit of the common-mode injection voltage u cmv1lmt and the lower limit of the common-mode injection voltage u cmv2lmt One of them is the optimal common-mode voltage u cmvopt Specifically, this can be achieved by comparing the first real-time value i of the DC bus capacitor ripple current. cap1 absolute value i cap1abs and the second real-time value i of the DC bus capacitor ripple current cap2 absolute value i cap2abs If i cap1abs Less than i cap2abs Then select the upper limit value of the common-mode injection voltage u. cmv1lmt As the optimal common-mode voltage u cmvopt If i cap1abs Greater than i cap2abs Then select the lower limit value of the common-mode injection voltage u. cmv2lmt As the optimal common-mode voltage u cmvopt .

[0095] Finally, based on the optimal common-mode voltage u cmvopt The common-mode voltage u of the MPC modulation method is calculated using a preset scaling factor α. cmvMPWM Specifically, when the optimal common-mode voltage u cmvopt When the value is greater than 0, the common-mode voltage u of the MPC modulation method cmvMPWM The following formula (6) is satisfied; when the optimal common-mode voltage u cmvopt When it is less than 0, the common-mode voltage u of the MPC modulation method cmvMPWM It satisfies the following formula (7).

[0096] (1-α)u cmvopt ≤u cmvMpwm ≤(1+α)u cmvopt (6)

[0097] (1+α)u cmvopt ≤u cmvMpwm ≤(1-α)u cmvopt (7)

[0098] The preset scaling factor α satisfies 0 ≤ α ≤ 0.5. In some exemplary embodiments, the preset scaling factor α can be set to 0.

[0099] Step S306: Based on the three-phase port voltage U a U b , and U c The peak value of the phase voltage U acmax The DC bus voltage U bus and the power factor of the output power command Determine the modulation ratio η.

[0100] Among them, the three-phase port voltage U a U b , and U c The maximum value of the peak value U acmax It can be obtained through appropriate technical means in the existing technology, which will not be elaborated here. The modulation ratio m is calculated according to the following formula (8); the power factor is calculated according to the following formula (9).

[0101] m = U acmax / U bus (8)

[0102]

[0103] In formula (8), based on the three-phase port voltage U a U b , and U c The maximum value of the phase voltage U acmax and the DC bus voltage U bus Calculate the modulation ratio m; in formula (9), calculate the power factor of the output power command based on the active power command P and the reactive power command Q. It should be understood that power factor It refers to the ratio of active power P to apparent power in an AC circuit, and also represents the cosine of the phase difference between voltage and current in an AC circuit; apparent power is a quantity that represents the capacity of AC electrical equipment, and it is equal to the product of the effective value of voltage and the effective value of current.

[0104] Modulation ratio m, power factor The modulation ratio η and the modulation ratio η are related as follows: the modulation ratio η represents the proportion of the DPWM mode's effective time to the total time and satisfies 0 ≤ η ≤ 1; a preset modulation ratio threshold m0 is configured, satisfying 0 ≤ m0 ≤ 1.15; a preset power factor threshold is configured. satisfy The modulation ratio η varies with the modulation ratio m and the power factor. The variation relationship is as follows: when the modulation ratio m is greater than the preset modulation ratio threshold m0, the modulation ratio η increases non-strictly monotonically with the decrease of the power factor ; when m is less than the preset modulation ratio threshold m0, the modulation ratio η decreases non-strictly monotonically with the decrease of the power factor ; when the power factor is greater than the preset power factor threshold , the modulation ratio η increases non-strictly monotonically with the decrease of the modulation ratio m. When the power factor is less than the preset power factor threshold , the modulation ratio η decreases non-strictly monotonically with the decrease of the modulation ratio m. Thus, the modulation ratio η can be obtained according to the calculated modulation ratio m and power factor as well as the preset modulation ratio threshold m0 and preset power factor threshold .

[0105] According to step S306, in some exemplary embodiments, the preset modulation ratio threshold m0 = 0.9 is configured, and the preset power factor threshold is configured. Then the variation relationship of the modulation ratio η with the modulation ratio m and power factor is as follows: when 1.1 ≤ m ≤ 1.15 and , η = 1; when m0 ≤ m < 1.1, η increases non-strictly monotonically with the decrease of ; when 0.7 ≤ m < m0, η decreases non-strictly monotonically with the decrease of ; when , η increases non-strictly monotonically with the decrease of m; when , η decreases non-strictly monotonically with the decrease of m; when m < 0.7 or , η = 0.

[0106] Step S308: Calculate the common-mode voltage U cmvDPWM of the CPWM method according to the common-mode voltage U cmvMPWM of the DPWM method and the common-mode voltage U cmvCPWM of the MPC modulation method.

[0107] Among them, the common-mode voltage U cmvCPWM of the CPWM method is between the common-mode voltage U cmvDPWM of the DPWM method and the common-mode voltage U cmvMPWM of the MPC modulation method.

[0108] Step S310: Calculate the common-mode injection voltage U according to the common-mode voltage U cmvDPWM of the DPWM method, the common-mode voltage U cmvMPWM of the MPC modulation method, the common-mode voltage U cmvCPWM of the CPWM method and the modulation ratio ηcmv .

[0109] Wherein, the common-mode injection voltage U cmv It includes a first part, a second part, and a third part; the common-mode injection voltage U cmv The first part uses the common-mode voltage U of the DPWM method. cmvDPWM The common-mode injection voltage U cmv The second part uses the common-mode voltage U of the MPC modulation method. cmvMPWM The third part of the common-mode injection voltage adopts the common-mode voltage U in CPWM mode. cmvCPWM The common-mode injection voltage U is determined based on the modulation ratio η. cmv The first portion relative to the common-mode injection voltage U cmv The proportion of the second part; the common-mode injection voltage U is determined according to the modulation ratio η. cmv The third part is respectively relative to the common-mode injection voltage U cmv The first part and the common-mode injection voltage U cmv The proportion of the second part.

[0110] Step S312: Convert the three-phase port voltage U a U b , and U c Single periodic time T ac The system is divided into three parts: a first part, a second part, and a third part; wherein, the individual periodic time T is determined according to the modulation ratio η. ac The first part, the single periodic time T ac The second part and the single periodic time T ac The third part of each is relative to the single periodic time T. ac The proportion; in the single periodic time T ac The first part, the single periodic time T ac The second part and the single periodic time T ac The third part is respectively injected with the common-mode injection voltage U cmv The first part, the common-mode injection voltage U cmv The second part and the common-mode injection voltage U cmv The third part is used to generate a single cycle of the output voltage modulation wave; the output voltage modulation wave is formed by repeating the single cycle of the output voltage modulation wave.

[0111] According to step S312, in some exemplary embodiments, the three-phase port voltage U can be... a Ub , and U c Single periodic time T ac The system is divided into six consecutive and non-overlapping sectors: sector I, sector II, sector III, sector IV, sector V, and sector VI. Each of these six sectors is further divided into four consecutive and non-overlapping sub-sectors: sub-sector 1, sub-sector 2, sub-sector 3, and sub-sector 4. Relative to each of the four sub-sectors corresponding to the six sectors, sub-sector 1, sub-sector 2, sub-sector 3, and sub-sector 4 are respectively determined relative to the single periodic time T according to the modulation ratio η. ac The proportions; and sub-sector 1 corresponds to the first part of the single periodic time period; sub-sector 3 corresponds to the second part of the single periodic time period; and sub-sectors 2 and 4 correspond to the third part of the single periodic time period. Specifically, the durations T1, T2, T3, and T4 of sub-sectors 1, 2, 3, and 4 are respectively:

[0112]

[0113] Where Δt1 and Δt2 satisfy:

[0114]

[0115] Combining steps S310 and S312, in some exemplary embodiments, the common-mode injection voltage U of each of the six sectors, namely sector I, sector II, sector III, sector IV, sector V, and sector VI, can be determined. cmv :

[0116]

[0117] According to step S312, in some exemplary embodiments, it is assumed that in the current cycle, the phase angle θ of the grid voltage is 0≤θ≤360°; the sector number k can be calculated according to the following formula (12):

[0118] k = round(θ / 60) (13)

[0119] Where `round` represents the floor function, and `k` takes values ​​from 1 to 6, corresponding to the six sectors: sector I, sector II, sector III, sector IV, sector V, and sector VI. The durations T1, T2, T3, and T4 of sub-sectors 1, 2, 3, and 4 are respectively:

[0120]

[0121] T4 is set to be the same as T2, meaning that the duration of the second sub-sector is the same as the duration of the fourth sub-sector.

[0122] In conjunction with steps S308, S310, and S312, in some exemplary embodiments, the common-mode voltage U of the DPWM mode can be determined according to the following formula (15). cmvDPWM and the common-mode voltage U of the MPC modulation method cmvMPWM Calculate the common-mode voltage U of the CPWM method. cmvCPWM :

[0123] u cmvCpwm (t)=l(t)u cmvDpwm (t)+[1-l(t)]u cmvMpwm (t)(15)

[0124] Where l(t) satisfies:

[0125]

[0126] Where t represents the current time or real-time, and is within the duration [0, T2] of sub-sectors 2 and 4. Thus, it should be understood that, combining steps S308, S310, and S312, the common-mode voltage U of the DPWM method can be used as a reference. cmvDPWM The common-mode voltage U of the MPC modulation method cmvMPWM The duration T2 and real-time time t of the second sub-sector are used to calculate the real-time value U of the common-mode voltage of the CPWM mode corresponding to the real-time time t. cmvCPWM (t).

[0127] exist Figure 3 In the method shown, the DC bus voltage U of the three-phase three-level inverter is collected. bus and three-phase port voltage U a U b , and U c and the three-phase port current I a I b , and I c And according to the three-phase port voltage U a U b , and U c Calculate the common-mode voltage U in DPWM mode using the output power command. cmvDPWM And according to the DC bus voltage U bus The three-phase port voltage U a U b , and U c And the output power command calculates the common-mode voltage U of the MPC modulation method. cmvMPWMThis enables real-time acquisition and feedback of the current status of the DC input terminal and the three-phase AC port, and allows setting of the common-mode voltage of the corresponding modulation mode based on the feedback. Figure 3 The method shown also utilizes the three-phase port voltage U a U b , and U c The peak value of the phase voltage U acmax The DC bus voltage U bus and the power factor of the output power command The modulation ratio η is determined, thereby enabling the adjustment of the modulation ratio based on real-time acquired data. Figure 3 The method shown also takes into account the output power command and sets the common-mode voltage and modulation ratio for the corresponding modulation scheme accordingly. Figure 3 The method shown also includes the common-mode injection voltage U cmv The first part uses the common-mode voltage U of the DPWM method. cmvDPWM The common-mode injection voltage U cmv The second part uses the common-mode voltage U of the MPC modulation method. cmvMPWM The common-mode injection voltage U cmv The third part uses the common-mode voltage U in CPWM mode. cmvCPWM The common-mode injection voltage U is determined based on the modulation ratio η. cmv The first portion relative to the common-mode injection voltage U cmv The proportion of the second part; the common-mode injection voltage U is determined according to the modulation ratio η. cmv The third part is respectively relative to the common-mode injection voltage U cmv The first part and the common-mode injection voltage U cmv The proportion of the second part.

[0128] Thus, in Figure 3 The method shown employs DPWM, MPC modulation, and CPWM, and adjusts the modulation ratio η and common-mode injection voltage U based on real-time acquired data. cmv This achieves the goal of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses. In other words, it reduces the number of bus capacitors and inverter costs while also lowering the switching losses of the inverter's switching devices. Furthermore, because the common-mode injection voltage U... cmv It achieves flexibility to adapt to different operating conditions of the three-phase three-level inverter by collecting data from the three-phase three-level inverter in real time.

[0129] exist Figure 3 The method shown also includes converting the three-phase port voltage Ua U b , and U c Single periodic time T ac The system is divided into three parts: a first part, a second part, and a third part; wherein, the individual periodic time T is determined according to the modulation ratio η. ac The first part, the single periodic time T ac The second part and the single periodic time T ac The third part of each is relative to the single periodic time T. ac The proportion; in the single periodic time T ac The first part, the single periodic time T ac The second part and the single periodic time T ac The third part is respectively injected with the common-mode injection voltage U cmv The first part, the common-mode injection voltage U cmv The second part and the common-mode injection voltage U cmv The third part is used to generate a single cycle of the output voltage modulation wave; the output voltage modulation wave is formed by repeating the single cycle of the output voltage modulation wave.

[0130] Thus, in Figure 3 In the method shown, by analyzing a single periodic time T ac The common-mode injection voltage U is divided and configured accordingly. cmv The various parts, thus achieving the goal of processing within a single periodic time T. ac Simultaneously employing DPWM, MPC modulation, and CPWM methods, and generating a single cycle of the corresponding output voltage modulation wave, the waveform of the corresponding output voltage modulation wave is formed by cycling through the single cycle, thus achieving the desired control effect.

[0131] Please see Figure 4 , Figure 4 This is a flowchart illustrating another implementation of the inverter common-mode voltage injection control method provided in this application embodiment. Figure 4 As shown, the common-mode voltage injection control method includes the following steps.

[0132] Steps S400, S402, S404 and S406 are the same as steps S300, S302, S304 and S306, respectively, and will not be described again here.

[0133] Step S408: Based on the common-mode voltage U of the DPWM method cmvDPWM The common-mode voltage U of the MPC modulation method cmvMPWMAnd the common-mode injection voltage U is calculated using the modulation ratio η. cmv .

[0134] Wherein, the common-mode injection voltage U cmv It includes a first part and a second part; the common-mode injection voltage U cmv The first part uses the common-mode voltage U of the DPWM method. cmvDPWM The common-mode injection voltage U cmv The second part uses the common-mode voltage U of the MPC modulation method. cmvMPWM The ratio of the first portion of the common-mode injection voltage to the second portion of the common-mode injection voltage is determined according to the modulation ratio η.

[0135] Step S410: Convert the three-phase port voltage U a U b , and U c Multiple consecutive periodic time periods T are divided into a first segment and a second segment; wherein, the first segment and the second segment of the multiple consecutive periodic time periods T are each composed of one or more consecutive periods in the multiple consecutive periodic time periods T; the proportions of the first segment and the second segment of the multiple consecutive periodic time periods T relative to the multiple consecutive periodic time periods T are determined according to the modulation ratio η; the first portion of the common-mode injection voltage is injected into the first segment of the multiple consecutive periodic time periods T, and the second portion of the common-mode injection voltage is injected into the second segment of the multiple consecutive periodic time periods T to generate multiple consecutive periods of the output voltage modulation wave; the output voltage modulation wave is formed by the multiple consecutive periods of the output voltage modulation wave.

[0136] In this case, assume that N consecutive periodic time intervals T are divided into a first segment and a second segment, where the first segment consists of M consecutive periods and the second segment consists of the remaining NM consecutive periods; then, in the M consecutive periods of the first segment, u cmv =u cmvDpwm In the second segment, over NM consecutive periods, u satisfies cmv =u cmvMpwm Furthermore, M and N satisfy:

[0137] M = round(N·η) (17)

[0138] Here, round represents the rounding function.

[0139] According to step S410, in some exemplary embodiments, N can be set to 10, that is, in a time period of 10 consecutive cycles, u satisfies cmv =ucmvDpwm And in a continuous time period of 10-M consecutive cycles, the condition u is satisfied. cmv =u cmvMpwm .

[0140] Thus, in Figure 4 The method shown employs DPWM and MPC modulation, and adjusts the modulation ratio η and common-mode injection voltage U based on real-time acquired data. cmv This achieves the goal of simultaneously minimizing DC bus capacitor ripple current and reducing switching losses. In other words, it reduces the number of bus capacitors and inverter costs while also lowering the switching losses of the inverter's switching devices. Furthermore, because the common-mode injection voltage U... cmv It achieves flexibility to adapt to different operating conditions of the three-phase three-level inverter by collecting data from the three-phase three-level inverter in real time.

[0141] Furthermore, in Figure 4 In the method shown, the common-mode injection voltage U is configured by dividing multiple consecutive periodic time periods T and configuring the common-mode injection voltage U accordingly. cmv The various parts of the system enable the simultaneous use of DPWM and MPC modulation methods in multiple consecutive periodic time periods T, generating multiple consecutive periods of the corresponding output voltage modulation wave, which in turn cycle through these multiple consecutive periods to form the waveform of the corresponding output voltage modulation wave, thus achieving the desired control effect.

[0142] The specific embodiments provided in this application can be implemented using any one or a combination of hardware, software, firmware, or solid-state logic circuits, and can be combined with signal processing, control, and / or dedicated circuitry. The devices or apparatuses provided in the specific embodiments of this application may include one or more processors (e.g., microprocessors, controllers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), etc.) that process various computer-executable instructions to control the operation of the devices or apparatuses. The devices or apparatuses provided in the specific embodiments of this application may include a system bus or data transmission system that couples various components together. The system bus may include any one or a combination of different bus architectures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and / or a processor or local bus utilizing any of a variety of bus architectures. The devices or apparatuses provided in the specific embodiments of this application may be provided separately, as part of a system, or as part of other devices or apparatuses.

[0143] The specific embodiments provided in this application may include computer-readable storage media or combinations thereof, such as one or more storage devices capable of providing non-transitory data storage. The computer-readable storage medium / storage device may be configured to store data, program modules, and / or instructions that, when executed by a processor of the device or apparatus provided in the specific embodiments of this application, cause the device or apparatus to perform relevant operations. The computer-readable storage medium / storage device may include one or more of the following features: volatile, non-volatile, dynamic, static, readable / writable, read-only, random access, sequential access, location addressable, file addressable, and content addressable. In one or more exemplary embodiments, the computer-readable storage medium / storage device may be integrated into the device or apparatus provided in the specific embodiments of this application or belong to a common system. Computer-readable storage media / storage devices may include optical storage devices, semiconductor storage devices and / or magnetic storage devices, etc., and may also include random access memory (RAM), flash memory, read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, removable disks, recordable and / or rewritable optical discs (CD), digital versatile optical discs (DVD), mass storage media devices or any other suitable form of storage media.

[0144] The above are implementation methods of the embodiments of this application. It should be noted that the steps in the methods described in the specific embodiments of this application can be adjusted, merged, and deleted according to actual needs. In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. It is understood that the structures shown in the embodiments of this application and the accompanying drawings do not constitute a specific limitation on the relevant device or system. In other embodiments of this application, the relevant device or system may include more or fewer components than in the specific embodiments and accompanying drawings, or combine some components, or split some components, or have different component arrangements. Those skilled in the art will understand that various modifications or changes can be made to the arrangement, operation, and details of the methods and devices described in the specific embodiments without departing from the spirit and scope of the specific embodiments of this application; several improvements and refinements can also be made without departing from the principle of the embodiments of this application, and these improvements and refinements are also considered to be within the protection scope of this application.

Claims

1. A common-mode voltage injection control method, applied to a three-phase three-level inverter, characterized in that, The common-mode voltage injection control method includes: Obtain the DC bus voltage and three-phase port voltage of the three-phase three-level inverter; Calculate the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltage and output power command; Based on the DC bus voltage, the three-phase port voltage, and the output power command calculation model, the common-mode voltage of the MPC modulation mode is predicted and controlled. The modulation ratio is determined based on the maximum peak value of the phase voltages at the three-phase ports, the DC bus voltage, and the power factor of the output power command; and Based on the common-mode voltage of the DPWM modulation method, the modulation ratio, and the common-mode voltage of the MPC modulation method, a common-mode injection voltage is generated. The common-mode injection voltage is used to generate the output voltage modulation wave of the three-phase three-level inverter. The common-mode injection voltage includes a first part and a second part. The first part of the common-mode injection voltage adopts the common-mode voltage of the DPWM method, and the second part of the common-mode injection voltage adopts the common-mode voltage of the MPC modulation method. The ratio of the first part of the common-mode injection voltage to the second part of the common-mode injection voltage is determined according to the modulation ratio.

2. The common-mode voltage injection control method according to claim 1, characterized in that, The common-mode voltage injection control method further includes: Based on the common-mode voltage of the DPWM modulation method and the common-mode voltage of the MPC modulation method, the common-mode voltage of the Continuous Pulse Width Modulation (CPWM) method is calculated, wherein the common-mode voltage of the CPWM method is between the common-mode voltage of the DPWM method and the common-mode voltage of the MPC modulation method; and Calculate the common-mode injection voltage based on the common-mode voltage of the DPWM method, the modulation ratio, the common-mode voltage of the MPC modulation method, and the common-mode voltage of the CPWM method. The common-mode injection voltage further includes a third part, which adopts the common-mode voltage of the CPWM method. The ratio of the third part of the common-mode injection voltage to the first part and the second part of the common-mode injection voltage is determined according to the modulation ratio.

3. The common-mode voltage injection control method according to claim 2, characterized in that, The common-mode voltage injection control method further includes: The single-cycle time period of the three-phase port voltage is divided into a first part, a second part, and a third part, wherein the proportions of the first part, the second part, and the third part of the single-cycle time period relative to the single-cycle time period are determined according to the modulation ratio; and In the first portion of the single cycle time period, the second portion of the single cycle time period and the third portion of the single cycle time period are respectively injected into the first portion of the common-mode injection voltage, the second portion of the common-mode injection voltage and the third portion of the common-mode injection voltage to generate a single cycle of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the single cycle of the output voltage modulation wave.

4. The common-mode voltage injection control method according to claim 3, characterized in that, The division of the single-cycle time period of the three-phase port voltage into the first part, the second part, and the third part includes: The single period of the three-phase port voltage is divided into six consecutive and non-overlapping sectors, wherein each of the six sectors is divided into four consecutive and non-overlapping sub-sectors. The common-mode voltage injection control method further includes, relative to the four sub-sectors of each of the six sectors: The four sub-sectors are labeled sequentially as the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector; and The proportions of the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector relative to the single period time are determined according to the modulation ratio. Wherein, the first sub-sector corresponds to the first part of the single periodic time period, the third sub-sector corresponds to the second part of the single periodic time period, and the second sub-sector and the fourth sub-sector correspond to the third part of the single periodic time period.

5. The common-mode voltage injection control method according to claim 4, wherein the duration of the second sub-sector is the same as the duration of the fourth sub-sector, characterized in that, The common-mode voltage injection control method further includes: Based on the common-mode voltage of the DPWM mode, the common-mode voltage of the MPC modulation mode, the duration of the second sub-sector, and the real-time time, calculate the real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time.

6. The common-mode voltage injection control method according to claim 1, characterized in that, The common-mode voltage injection control method further includes: The three-phase port voltage is divided into a first segment and a second segment, wherein the first segment and the second segment are each composed of one or more consecutive cycles from the multiple consecutive periodic time segments, and the proportions of the first segment and the second segment relative to the multiple consecutive periodic time segments are determined according to the modulation ratio; and The first portion of the common-mode injection voltage and the second portion of the common-mode injection voltage are injected into the first segment and the second segment of the plurality of consecutive periodic time periods, respectively, to generate a plurality of consecutive periods of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the plurality of consecutive periods of the output voltage modulation wave.

7. The common-mode voltage injection control method according to claim 1, wherein the output power command includes an active power command, characterized in that, The calculation of the common-mode voltage of the MPC modulation method based on the DC bus voltage, the three-phase port voltage, and the output power command includes: Determine the minimum value of the three-phase port voltage and the first phase voltage corresponding to the minimum value, the maximum value of the three-phase port voltage and the second phase voltage corresponding to the maximum value, the first phase current in phase with the first phase voltage and the second phase current in phase with the second phase voltage in the three-phase port current of the three-phase three-level inverter; Based on the active power command, the DC bus voltage, the first phase voltage and the first phase current corresponding to the minimum value, calculate the first feasible value of the common mode voltage; Based on the active power command, the DC bus voltage, and the second phase voltage and second phase current corresponding to the maximum value, calculate the second feasible value of the common-mode voltage; Limiting the first feasible value of the common-mode voltage and the second feasible value of the common-mode voltage respectively yields the upper limit value of the common-mode injection voltage and the lower limit value of the common-mode injection voltage; Based on the upper limit of the common-mode injection voltage, the three-phase port voltage, and the three-phase port current, calculate the first real-time value of the DC bus capacitor ripple current. The second real-time value of the DC bus capacitor ripple current is calculated based on the lower limit of the common-mode injection voltage, the three-phase port voltage, and the three-phase port current. The optimal common-mode voltage is selected from the upper and lower limits of the common-mode injection voltage, corresponding to the smaller of the absolute values ​​of the first and second real-time values ​​of the DC bus capacitor ripple current; and The common-mode voltage of the MPC modulation method is calculated based on the optimal common-mode voltage and the preset scaling factor.

8. The common-mode voltage injection control method according to claim 1, wherein the output power command includes an active power command and a reactive power command, characterized in that, The step of determining the modulation ratio based on the peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command includes: The power factor of the output power command is calculated based on the active power command and the reactive power command; and The modulation ratio is determined based on the ratio of the peak value of the phase voltage of the three-phase port voltage to the DC bus voltage and the power factor.

9. A common-mode voltage injection control device, applied to a three-phase three-level inverter, the common-mode voltage injection control device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor performs the following operations according to the computer program: Obtain the DC bus voltage and three-phase port voltage of the three-phase three-level inverter; Calculate the common-mode voltage of the discontinuous pulse width modulation (DPWM) mode based on the three-phase port voltage and output power command; Based on the DC bus voltage, the three-phase port voltage, and the output power command calculation model, the common-mode voltage of the MPC modulation mode is predicted and controlled. The modulation ratio is determined based on the maximum peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command. as well as Based on the common-mode voltage of the DPWM modulation method, the modulation ratio, and the common-mode voltage of the MPC modulation method, a common-mode injection voltage is generated. The common-mode injection voltage is used to generate the output voltage modulation wave of the three-phase three-level inverter. The common-mode injection voltage includes a first part and a second part. The first part of the common-mode injection voltage adopts the common-mode voltage of the DPWM method, and the second part of the common-mode injection voltage adopts the common-mode voltage of the MPC modulation method. The ratio of the first part of the common-mode injection voltage to the second part of the common-mode injection voltage is determined according to the modulation ratio.

10. The common-mode voltage injection control device according to claim 9, characterized in that, The processor also performs: Based on the common-mode voltage of the DPWM modulation method and the common-mode voltage of the MPC modulation method, the common-mode voltage of the Continuous Pulse Width Modulation (CPWM) method is calculated, wherein the common-mode voltage of the CPWM method is between the common-mode voltage of the DPWM method and the common-mode voltage of the MPC modulation method; and Calculate the common-mode injection voltage based on the common-mode voltage of the DPWM method, the modulation ratio, the common-mode voltage of the MPC modulation method, and the common-mode voltage of the CPWM method. The common-mode injection voltage further includes a third part, which adopts the common-mode voltage of the CPWM method. The ratio of the third part of the common-mode injection voltage to the first part and the second part of the common-mode injection voltage is determined according to the modulation ratio.

11. The common-mode voltage injection control device according to claim 10, characterized in that, The processor also performs: The single-cycle time period of the three-phase port voltage is divided into a first part, a second part, and a third part, wherein the proportions of the first part, the second part, and the third part of the single-cycle time period relative to the single-cycle time period are determined according to the modulation ratio; and In the first portion of the single cycle time period, the second portion of the single cycle time period and the third portion of the single cycle time period are respectively injected into the first portion of the common-mode injection voltage, the second portion of the common-mode injection voltage and the third portion of the common-mode injection voltage to generate a single cycle of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the single cycle of the output voltage modulation wave.

12. The common-mode voltage injection control device according to claim 11, characterized in that, The division of the single-cycle time period of the three-phase port voltage into the first part, the second part, and the third part includes: The single period of the three-phase port voltage is divided into six consecutive and non-overlapping sectors, wherein each of the six sectors is divided into four consecutive and non-overlapping sub-sectors. The common-mode voltage injection control method further includes, relative to the four sub-sectors of each of the six sectors: The four sub-sectors are labeled sequentially as the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector; and The proportions of the first sub-sector, the second sub-sector, the third sub-sector, and the fourth sub-sector relative to the single period time are determined according to the modulation ratio. Wherein, the first sub-sector corresponds to the first part of the single periodic time period, the third sub-sector corresponds to the second part of the single periodic time period, and the second sub-sector and the fourth sub-sector correspond to the third part of the single periodic time period.

13. The common-mode voltage injection control device according to claim 12, wherein the duration of the second sub-sector is the same as the duration of the fourth sub-sector, characterized in that, The processor also performs: Based on the common-mode voltage of the DPWM mode, the common-mode voltage of the MPC modulation mode, the duration of the second sub-sector, and the real-time time, calculate the real-time value of the common-mode voltage of the CPWM mode corresponding to the real-time time.

14. The common-mode voltage injection control device according to claim 9, characterized in that, The processor also performs: The three-phase port voltage is divided into a first segment and a second segment, wherein the first segment and the second segment are each composed of one or more consecutive cycles from the multiple consecutive periodic time segments, and the proportions of the first segment and the second segment relative to the multiple consecutive periodic time segments are determined according to the modulation ratio; and The first portion of the common-mode injection voltage and the second portion of the common-mode injection voltage are injected into the first segment and the second segment of the plurality of consecutive periodic time periods, respectively, to generate a plurality of consecutive periods of the output voltage modulation wave, wherein the output voltage modulation wave is formed by the plurality of consecutive periods of the output voltage modulation wave.

15. The common-mode voltage injection control device according to claim 9, wherein the output power command includes an active power command, characterized in that, The calculation of the common-mode voltage of the MPC modulation method based on the DC bus voltage, the three-phase port voltage, and the output power command includes: Determine the minimum value of the three-phase port voltage and the first phase voltage corresponding to the minimum value, the maximum value of the three-phase port voltage and the second phase voltage corresponding to the maximum value, the first phase current in phase with the first phase voltage and the second phase current in phase with the second phase voltage in the three-phase port current of the three-phase three-level inverter; Based on the active power command, the DC bus voltage, the first phase voltage and the first phase current corresponding to the minimum value, calculate the first feasible value of the common mode voltage; Based on the active power command, the DC bus voltage, and the second phase voltage and second phase current corresponding to the maximum value, calculate the second feasible value of the common-mode voltage; Limiting the first feasible value of the common-mode voltage and the second feasible value of the common-mode voltage respectively yields the upper limit value of the common-mode injection voltage and the lower limit value of the common-mode injection voltage; Based on the upper limit of the common-mode injection voltage, the three-phase port voltage, and the three-phase port current, calculate the first real-time value of the DC bus capacitor ripple current. The second real-time value of the DC bus capacitor ripple current is calculated based on the lower limit of the common-mode injection voltage, the three-phase port voltage, and the three-phase port current. The optimal common-mode voltage is selected from the upper and lower limits of the common-mode injection voltage, corresponding to the smaller of the absolute values ​​of the first and second real-time values ​​of the DC bus capacitor ripple current; and The common-mode voltage of the MPC modulation method is calculated based on the optimal common-mode voltage and the preset scaling factor.

16. The common-mode voltage injection control device according to claim 9, wherein the output power command includes an active power command and a reactive power command, characterized in that, The step of determining the modulation ratio based on the peak value of the phase voltage of the three-phase port voltage, the DC bus voltage, and the power factor of the output power command includes: The power factor of the output power command is calculated based on the active power command and the reactive power command; and The modulation ratio is determined based on the ratio of the peak value of the phase voltage of the three-phase port voltage to the DC bus voltage and the power factor.

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