Method and apparatus for balancing midpoint potential to suppress common-mode voltage influence, and electronic device

Abstract

This application provides a method, apparatus, and electronic device for suppressing the influence of common-mode voltage and achieving midpoint potential balance. The method includes: acquiring the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, and the direct-axis voltage component and the quadrature-axis voltage component; modulating the direct-axis voltage component and the quadrature-axis voltage component based on the direct-axis inductor current and the quadrature-axis inductor current to obtain a three-phase initial modulation reference voltage; performing compensation analysis on the voltage difference between the positive and negative bus to obtain a target compensation signal; compensating the three-phase initial modulation reference voltage using the target compensation signal to obtain a three-phase target modulation reference voltage; and determining a three-phase switch drive signal based on the three-phase target modulation reference voltage, wherein the three-phase switch drive signal is used to control the midpoint potential. This method aims to improve the reliability of midpoint potential suppression.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a method, apparatus and electronic device for suppressing the influence of common-mode voltage in midpoint potential balancing. Background Technology

[0002] Multilevel converters are the core topology of high-voltage, high-power energy storage systems and grid-connected inverters. The DC bus midpoint potential of multilevel topologies is susceptible to the effects of switching state transitions and load fluctuations. The zero-sequence component (common-mode voltage) will return to the DC bus through a filter, exacerbating the fluctuations in the midpoint potential.

[0003] In existing technologies, when a three-phase three-wire system is used, and the grid-side LC or LCL filter (with the capacitor connected in a star configuration) is connected to the midpoint of the DC bus support capacitor, the zero-sequence component (common-mode voltage) will return to the midpoint of the DC bus support capacitor, causing a huge fluctuation in the midpoint potential and resulting in low reliability of midpoint potential suppression. Summary of the Invention

[0004] This application provides a method, apparatus, and electronic device for balancing midpoint potential to suppress the influence of common-mode voltage, thereby improving the reliability of midpoint potential suppression.

[0005] In a first aspect, embodiments of this application provide a method for balancing the midpoint potential to suppress the influence of common-mode voltage, comprising:

[0006] Obtain the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component;

[0007] Based on the direct-axis inductor current and the quadrature-axis inductor current, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage;

[0008] The voltage difference between the positive and negative busbars is analyzed and processed to obtain the target compensation signal;

[0009] The three-phase initial modulation reference voltage is compensated using the target compensation signal to obtain the three-phase target modulation reference voltage.

[0010] Based on the three-phase target modulation reference voltage, a three-phase switch drive signal is determined, which is used to control the midpoint potential.

[0011] In one possible implementation, the direct-axis voltage component and the quadrature-axis voltage component are modulated based on the direct-axis inductor current and the quadrature-axis inductor current to obtain a three-phase initial modulation reference voltage, including:

[0012] The direct-axis error signal is determined based on the direct-axis inductor current and the direct-axis reference current, and the direct-axis error signal is subjected to proportional-integral adjustment processing to obtain the direct-axis adjustment signal.

[0013] The quadrature axis error signal is determined based on the quadrature axis inductor current and the quadrature axis reference current, and the quadrature axis error signal is subjected to proportional-integral adjustment processing to obtain the quadrature axis adjustment signal;

[0014] Based on the direct-axis inductor current and the quadrature-axis inductor current, determine the cross-coupling compensation term;

[0015] The three-phase initial modulation reference voltage is determined based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term.

[0016] In one possible implementation, the cross-coupling compensation term includes a direct-axis cross-coupling compensation term and a quadrature-axis cross-coupling compensation term; determining the three-phase initial modulation reference voltage based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term includes:

[0017] The direct-axis modulation voltage reference is obtained by performing feedforward compensation processing on the direct-axis adjustment signal through the direct-axis cross compensation term.

[0018] The quadrature axis cross-compensation term is used to perform feedforward compensation processing on the quadrature axis adjustment signal to obtain the quadrature axis modulation voltage reference;

[0019] Based on the grid phase and coordinate inverse transformation, the three-phase adjustment voltages corresponding to the direct-axis modulation voltage reference and the quadrature-axis modulation voltage reference are determined, and the three-phase adjustment voltages are pre-processed to obtain the three-phase initial modulation reference voltages.

[0020] In one possible implementation, the voltage difference between the positive and negative busbars is subjected to compensation analysis to obtain a target compensation signal, including:

[0021] The controller performs a first adjustment process on the voltage difference between the positive and negative busbars to obtain a first compensation signal.

[0022] Based on the filter, the voltage difference between the positive and negative busbars is subjected to a second adjustment process to obtain a second compensation signal;

[0023] The first compensation signal and the second compensation signal are superimposed to obtain the target compensation signal.

[0024] In one possible implementation, based on a filter, a second adjustment process is performed on the positive and negative bus voltage difference to obtain a second compensation signal, including:

[0025] Based on the filter, the voltage difference between the positive and negative busbars is filtered to obtain a specific frequency component of the midpoint potential fluctuation.

[0026] The specific frequency component is determined as the second compensation signal.

[0027] In one possible implementation, determining the three-phase switch drive signal based on the three-phase target modulation reference voltage includes:

[0028] Based on the three-phase target modulation reference voltage, determine the initial equivalent duration of capacitor charging for the inverter.

[0029] Based on the midpoint potential state of the inverter, the initial equivalent duration is adjusted to obtain the redundant vector duration of the capacitor charging corresponding to the inverter.

[0030] Based on the duration of the redundancy vector and the topology of the inverter, the switching timing of the three-phase bridge arm is generated;

[0031] Generate the three-phase switch drive signals corresponding to the turn-on timing of the switching transistors of the three-phase bridge arm.

[0032] In one possible implementation, acquiring the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component, includes:

[0033] Obtain the voltage difference between the positive and negative DC bus, the three-phase voltage of the power grid, and the three-phase inductor current of the inverter;

[0034] The phase of the power grid is obtained through a phase-locked loop;

[0035] The direct-axis inductor current and the quadrature-axis inductor current are determined based on the grid phase and the three-phase inductor current of the inverter.

[0036] The direct-axis voltage component and the quadrature-axis voltage component are determined based on the grid phase and the three-phase grid voltage.

[0037] Secondly, embodiments of this application provide a midpoint potential balancing device for suppressing the influence of common-mode voltage, comprising an acquisition module, a modulation processing module, a first compensation processing module, a second compensation processing module, and a determination module:

[0038] The acquisition module is used to acquire the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component;

[0039] The modulation processing module is used to modulate the direct-axis voltage component and the quadrature-axis voltage component according to the direct-axis inductor current and the quadrature-axis inductor current to obtain the three-phase initial modulation reference voltage.

[0040] The first compensation processing module is used to perform compensation analysis processing on the voltage difference between the positive and negative busbars to obtain the target compensation signal;

[0041] The second compensation processing module is used to perform compensation processing on the three-phase initial modulation reference voltage through the target compensation signal to obtain the three-phase target modulation reference voltage;

[0042] The determining module is used to determine the three-phase switch drive signal based on the three-phase target modulation reference voltage, and the three-phase switch drive signal is used to control the midpoint potential.

[0043] In one possible implementation, the modulation processing module is specifically used to modulate the direct-axis voltage component and the quadrature-axis voltage component according to the direct-axis inductor current and the quadrature-axis inductor current to obtain a three-phase initial modulation reference voltage, including:

[0044] The direct-axis error signal is determined based on the direct-axis inductor current and the direct-axis reference current, and the direct-axis error signal is subjected to proportional-integral adjustment processing to obtain the direct-axis adjustment signal.

[0045] The quadrature axis error signal is determined based on the quadrature axis inductor current and the quadrature axis reference current, and the quadrature axis error signal is subjected to proportional-integral adjustment processing to obtain the quadrature axis adjustment signal;

[0046] Based on the direct-axis inductor current and the quadrature-axis inductor current, determine the cross-coupling compensation term;

[0047] The three-phase initial modulation reference voltage is determined based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term.

[0048] In one possible implementation, the cross-coupling compensation term includes a direct-axis cross-coupling compensation term and a quadrature-axis cross-coupling compensation term; the modulation processing module is specifically used to determine the three-phase initial modulation reference voltage based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term, including:

[0049] The direct-axis modulation voltage reference is obtained by performing feedforward compensation processing on the direct-axis adjustment signal through the direct-axis cross compensation term.

[0050] The quadrature axis cross-compensation term is used to perform feedforward compensation processing on the quadrature axis adjustment signal to obtain the quadrature axis modulation voltage reference;

[0051] Based on the grid phase and coordinate inverse transformation, the three-phase adjustment voltages corresponding to the direct-axis modulation voltage reference and the quadrature-axis modulation voltage reference are determined, and the three-phase adjustment voltages are pre-processed to obtain the three-phase initial modulation reference voltages.

[0052] In one possible implementation, the first compensation analysis process is performed on the positive and negative bus voltage difference to obtain the target compensation signal, including a module specifically used for:

[0053] The controller performs a first adjustment process on the voltage difference between the positive and negative busbars to obtain a first compensation signal.

[0054] Based on the filter, the voltage difference between the positive and negative busbars is subjected to a second adjustment process to obtain a second compensation signal;

[0055] The first compensation signal and the second compensation signal are superimposed to obtain the target compensation signal.

[0056] In one possible implementation, the first compensation processing module is specifically used to perform a second adjustment process on the positive and negative bus voltage difference based on the filter to obtain a second compensation signal, including:

[0057] Based on the filter, the voltage difference between the positive and negative busbars is filtered to obtain a specific frequency component of the midpoint potential fluctuation.

[0058] The specific frequency component is determined as the second compensation signal.

[0059] In one possible implementation, the three-phase switch drive signal is determined based on the three-phase target modulation reference voltage, including a module specifically used for:

[0060] Based on the three-phase target modulation reference voltage, determine the initial equivalent duration of capacitor charging for the inverter.

[0061] Based on the midpoint potential state of the inverter, the initial equivalent duration is adjusted to obtain the redundant vector duration of the capacitor charging corresponding to the inverter.

[0062] Based on the duration of the redundancy vector and the topology of the inverter, the switching timing of the three-phase bridge arm is generated;

[0063] Generate the three-phase switch drive signals corresponding to the turn-on timing of the switching transistors of the three-phase bridge arm.

[0064] In one possible implementation, the module for acquiring the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component, is specifically used for:

[0065] Obtain the voltage difference between the positive and negative DC bus, the three-phase voltage of the power grid, and the three-phase inductor current of the inverter;

[0066] The phase of the power grid is obtained through a phase-locked loop;

[0067] The direct-axis inductor current and the quadrature-axis inductor current are determined based on the grid phase and the three-phase inductor current of the inverter.

[0068] The direct-axis voltage component and the quadrature-axis voltage component are determined based on the grid phase and the three-phase grid voltage.

[0069] Thirdly, embodiments of this application provide an electronic device, including: a memory and a processor;

[0070] The memory stores computer-executed instructions;

[0071] The processor executes computer execution instructions stored in the memory, causing the processor to perform the first aspect and / or various possible implementations of the first aspect as described above.

[0072] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the first aspect and / or various possible implementations of the first aspect.

[0073] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.

[0074] The midpoint potential balancing method, apparatus, and electronic equipment for suppressing the influence of common-mode voltage provided in this application can perform compensation analysis on the voltage difference between positive and negative buses to obtain a target compensation signal. This ensures that the target compensation signal accurately matches the midpoint potential fluctuation. Then, the target compensation signal is used to compensate the three-phase initial modulation reference voltage after modulation processing to obtain the three-phase target modulation reference voltage. This generates a switch drive signal, which can drive the inverter switching transistors to dynamically adjust their switching states, thereby suppressing midpoint potential fluctuations and improving the reliability of midpoint potential suppression. Attached Figure Description

[0075] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0076] Figure 1 A schematic diagram illustrating an application scenario provided by this application;

[0077] Figure 2 A flowchart illustrating a midpoint potential balancing method for suppressing the influence of common-mode voltage provided in this application;

[0078] Figure 3 A system control block diagram for a midpoint potential balance method to suppress the influence of common-mode voltage provided in this application;

[0079] Figure 4 A flowchart illustrating another method for suppressing the influence of common-mode voltage provided in this application for midpoint potential balancing;

[0080] Figure 5 This application provides a schematic diagram of a current loop PI regulation and feedforward decoupling control.

[0081] Figure 6 A schematic diagram of a midpoint potential balancing device for suppressing the influence of common-mode voltage provided in this application;

[0082] Figure 7 This is a schematic diagram of the structure of an electronic device provided in this application.

[0083] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0084] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0085] Figure 1 This diagram illustrates an application scenario provided by this application. Please refer to [link / reference]. Figure 1As shown, this application can be applied to high-voltage, high-power energy storage systems and three-level active neutral point clamped (ANPC) converters. This application scenario can include a three-level inverter 101, a three-level rectifier 102, an LC / LCL filter 103, and a processing device 104. The DC side consists of a DC bus composed of series capacitors, which can receive DC power rectified from the grid side by the three-level rectifier 102 and input DC current to the three-level inverter 101. The LC / LCL filter 103 can filter the three-phase bridge arm current output by the three-level inverter 101 to obtain the three-phase current from the grid side. The processing device 104 can control and process the operating states of the three-level inverter 101, the three-level rectifier 102, and the LC / LCL filter 103.

[0086] The processing device 104 can acquire the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component; based on the direct-axis inductor current and the quadrature-axis inductor current, it modulates the direct-axis voltage component and the quadrature-axis voltage component to obtain the three-phase initial modulation reference voltage; it performs compensation analysis on the voltage difference between the positive and negative bus to obtain the target compensation signal; it performs compensation processing on the three-phase initial modulation reference voltage using the target compensation signal to obtain the three-phase target modulation reference voltage; and it determines the three-phase switch drive signal based on the three-phase target modulation reference voltage, which is used to control the neutral point potential.

[0087] In the prior art, when a three-phase three-wire system is used, and the grid-side LC or LCL filter (with the capacitor connected in a star configuration) is connected to the midpoint of the DC bus support capacitor, the zero-sequence component (common-mode voltage) will return to the midpoint of the DC bus support capacitor, causing huge fluctuations in the midpoint potential and resulting in low reliability of midpoint potential suppression.

[0088] The midpoint potential balancing method for suppressing the influence of common-mode voltage provided in this application can perform compensation analysis on the voltage difference between the positive and negative buses to obtain a target compensation signal. This ensures that the target compensation signal accurately matches the midpoint potential fluctuation. Then, the target compensation signal is used to compensate the three-phase initial modulation reference voltage after modulation processing to obtain the three-phase target modulation reference voltage. This generates a switching drive signal, which can drive the inverter switching transistors to dynamically adjust the switching state, thereby suppressing the midpoint potential fluctuation and improving the reliability of midpoint potential suppression.

[0089] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0090] Figure 2 This is a flowchart illustrating a midpoint potential balancing method for suppressing the influence of common-mode voltage, as provided in this application. Please refer to... Figure 2 The method may include:

[0091] S201. Obtain the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component.

[0092] The execution subject of this application embodiment can be a processing device, or it can be a midpoint potential balancing device for suppressing the influence of common-mode voltage installed in the processing device. The midpoint potential balancing device for suppressing the influence of common-mode voltage can be implemented by software or by a combination of software and hardware.

[0093] In some embodiments, the voltage difference between the positive and negative DC bus, the three-phase grid voltage, and the three-phase inductor current of the inverter can be obtained; the grid phase can be obtained through a phase-locked loop; based on the grid phase, the direct-axis inductor current and quadrature-axis inductor current corresponding to the three-phase inductor current of the inverter can be determined; based on the grid phase, the direct-axis voltage component and quadrature-axis voltage component corresponding to the three-phase grid voltage can be determined.

[0094] To facilitate understanding, the following will be combined with... Figure 3 The parameters obtained in this application are explained. Figure 3 The system control block diagram for a midpoint potential balance method for suppressing the influence of common-mode voltage provided in this application is shown.

[0095] The voltage difference between the positive and negative buses is the series capacitor of the upper bridge arm of the DC bus. Series capacitor with lower bridge arm The difference between the positive and negative bus voltages can directly reflect the fluctuation state of the DC side midpoint potential.

[0096] The three-phase voltage of the power grid can be passed through , , The instruction is to lock the three-phase voltage of the power grid into phase angles, and then use the phase angles and the three-phase voltages or currents to perform coordinate transformations to obtain the corresponding D-axis and Q-axis components.

[0097] Please see Figure 3 The three-phase voltage of the power grid can be controlled through a phase-locked loop. , , Phase-locked loop (PLL) is performed to obtain the grid phase. The grid phase is used to indicate the rotation angle of the grid voltage vector. It is a key synchronization basis for the transformation between the abc coordinate system and the dq rotating coordinate system, ensuring the accuracy of the coordinate transformation.

[0098] It can be done , , This represents the three-phase inductor current (i.e., the bridge arm current) of the converter (i.e., the current including the inverter and rectifier). After being filtered by an LC filter, the grid-connected three-phase current is obtained. , , After filtering, the current is closer to a sine wave, and the three-phase current on the grid-connected side can be used for subsequent power control.

[0099] Can be based on grid phase By transforming the coordinates from abc to dq0, the three-phase inductor current on the bridge arm side is... , , ( Figure 3 Zhongyou (Indication), converted to direct-axis inductor current. and quadrature axis inductor current (The image is by) instruct).

[0100] Similarly, based on the grid phase, the three-phase voltage of the grid can be transformed from coordinates abc to dq0 to represent the grid phase. , , Converted to direct-axis voltage components and cross-axis voltage components .

[0101] Please see Figure 3 , , , These are the voltages of the filter capacitors in phases a, b, and c, respectively. , , Transform the coordinates from abc to dq0 to convert it into a direct-axis capacitor voltage. and cross-axis capacitor voltage .

[0102] In this application, raw electrical parameters (e.g., voltage sensor data) can be collected. , Wait, current sensor collects data. , (etc.), combining phase-locked loop synchronization technology with coordinate transformation algorithms.

[0103] S202. Based on the direct-axis inductor current and the quadrature-axis inductor current, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage.

[0104] In some embodiments, the direct-axis error signal can be determined based on the direct-axis inductor current and the direct-axis reference current, and proportional-integral (PI) adjustment processing can be performed on the direct-axis error signal to obtain the direct-axis adjustment signal; the quadrature-axis error signal can be determined based on the quadrature-axis inductor current and the quadrature-axis reference current, and PPI adjustment processing can be performed on the quadrature-axis error signal to obtain the quadrature-axis adjustment signal; based on the direct-axis inductor current... quadrature axis inductor current Based on the inductance parameter L, determine the cross-coupling compensation term; based on the direct-axis adjustment signal, quadrature-axis adjustment signal, and cross-coupling compensation term, determine the three-phase initial modulation reference voltage.

[0105] Please see Figure 3 It can be done Indicates direct-axis reference current, through The quadrature axis reference current is indicated. The direct axis reference current and quadrature axis reference current can be obtained according to the system control objectives, such as being calculated from the DC bus voltage outer loop, power command, or energy storage system charging and discharging command during grid-connected operation, and are used to achieve decoupled control of active and reactive power.

[0106] In this application, a PI controller can be used to achieve closed-loop current regulation without steady-state error, and dq-axis cross-coupling feedforward compensation can be introduced to achieve fast tracking of inverter output current and decoupling control of dq-axis components, thereby improving the dynamic response speed and steady-state accuracy of current control.

[0107] S203. Perform compensation analysis on the voltage difference between the positive and negative busbars to obtain the target compensation signal.

[0108] In some embodiments, the voltage difference between the positive and negative buses can be first adjusted by a controller to obtain a first compensation signal; the voltage difference between the positive and negative buses can be second adjusted based on a filter to obtain a second compensation signal; and the first compensation signal and the second compensation signal can be superimposed to obtain a target compensation signal.

[0109] Please see Figure 3 The controller can be a quasi-proportional resonant controller (QPR). A QPR controller is a controller that can track and control a specific frequency component without steady-state error. Its transfer function includes a proportional element, an integral element, and a resonant gain element. The resonant point is designed for the characteristic frequency of the midpoint potential fluctuation (such as twice the fundamental frequency of the power grid) to achieve precise suppression of the fluctuation component of that frequency.

[0110] Please see Figure 3 The filter can be a bandpass filter (Butterworth type), which is a filter that allows signals in a specific frequency range to pass through. It is used to extract characteristic frequency components in the midpoint potential fluctuation that are strongly correlated with the modulation condition and system operation, and to filter out DC bias and high-frequency noise interference.

[0111] The first compensation signal is a dynamic signal generated based on the controller output, used for closed-loop zero steady-state error adjustment of the characteristic frequency fluctuation component of the midpoint potential; the second compensation signal is a dynamic signal generated based on the fluctuation component after filter processing, used to provide the controller with a clean characteristic frequency feedback input, improving the targeting of the adjustment.

[0112] The target compensation signal refers to the dynamic signal obtained by the coordinated output of the controller and filter and after amplitude limiting. It is used to superimpose on the three-phase initial modulation reference voltage, correct the modulation command to balance the charging and discharging current of the DC side capacitor, and realize the midpoint potential regulation.

[0113] In this application, the characteristic fluctuation component of the midpoint potential can be extracted by a filter, and then combined with the controller's zero steady-state error adjustment capability for the characteristic frequency component, the extraction and dynamic compensation of the midpoint potential fluctuation can be realized, thereby improving the response speed and steady-state accuracy of the midpoint potential balance control, while enhancing the reliability of the control under low power factor and high modulation conditions.

[0114] S204. The three-phase initial modulation reference voltage is compensated by the target compensation signal to obtain the three-phase target modulation reference voltage.

[0115] Please see Figure 3 The three-phase target modulation reference voltage is , , ( Figure 3 Zhongyou (Indicator), corresponding to the final modulation voltage reference of the three-phase bridge arms A, B, and C of the inverter, used to generate subsequent switching drive signals.

[0116] Three-phase target modulation reference voltage , , The three phases are superimposed on the corresponding three-phase target compensation signals to obtain the three-phase target modulation reference voltage.

[0117] In some embodiments, the target compensation signal can be converted into a zero-sequence compensation voltage in a three-phase stationary coordinate system. Then, by superimposing zero-sequence compensation onto the three-phase modulation voltages, the initial modulation reference voltage of each phase is compensated. The zero-sequence compensation voltage is superimposed onto the initial modulation reference voltages of the three phases, and the mathematical expression is:

[0118]

[0119] in, , , This is the initial modulation reference voltage for the three phases. For compensation coefficient, The value range is 0~1, and it is calibrated according to the DC bus voltage level and the withstand voltage characteristics of the switching transistor. It is used to limit the compensation intensity and avoid over-modulation caused by the modulation voltage exceeding the DC bus voltage range.

[0120] Zero-sequence compensation voltage The polarity is dynamically determined by the target compensation signal. When the voltage difference between the positive and negative buses is greater than zero, The output is a negative zero-sequence voltage. By reducing the potential of the three-phase phase voltage relative to the midpoint, the discharge current of the upper capacitor Udc1 is reduced, and the charging current of the lower capacitor Udc2 is increased, thereby lowering the midpoint potential. When the voltage difference between the positive and negative buses is less than zero... It outputs a positive zero-sequence voltage, and conversely, it balances the voltage difference of the capacitor.

[0121] For example, assume the three-phase initial modulation reference voltage is , , , The total DC bus voltage; the target compensation signal obtained through QPR and bandpass filtering is converted into zero-sequence compensation voltage. (Corresponding to an upward bias in the midpoint potential, negative compensation is required); Compensation coefficient The three-phase target compensation signal is: , , After compensation, the overall phase voltage of the three phases shifts, without changing the line voltage. By adjusting the relative potential of the phase voltage and the midpoint, the charging and discharging current of the upper and lower capacitors is rebalanced, thus suppressing the fluctuation of the midpoint potential.

[0122] In this application, the initial modulation reference voltage of the three phases is compensated by zero-sequence compensation superposition, thereby decoupling the midpoint potential balance control and grid-connected current control. This ensures that the target compensation signal regulates the midpoint potential while avoiding interference of the compensation process on the three-phase line voltage and grid-connected current, thus improving the reliability of the midpoint potential balance and the grid-connected power quality of the system under low power factor and high modulation conditions.

[0123] S205. Determine the three-phase switch drive signal based on the three-phase target modulation reference voltage.

[0124] Please see Figure 3 Three-phase switch drive signals can be used , , The instruction corresponds to the switching transistor drive command (high level to turn on, low level to turn off) of the ANPC inverter's three-phase bridge arms A, B, and C.

[0125] The three-phase switch drive signal is used to control the neutral point potential. By controlling the on and off times of the switching transistors and the logic combination, the inverter output can be made to match the three-phase target modulation reference voltage, dynamically balancing the charging and discharging currents of the upper and lower capacitors on the DC side, and thus achieving neutral point potential stability.

[0126] In some embodiments, the initial equivalent duration of capacitor charging for the inverter can be determined based on the three-phase target modulation reference voltage; the initial equivalent duration is adjusted based on the midpoint potential state of the inverter to obtain the redundant vector duration of capacitor charging for the inverter; the switching timing sequence of the three-phase bridge arm is generated based on the redundant vector duration and the inverter topology; and the three-phase switch drive signals corresponding to the switching timing sequence of the three-phase bridge arm are generated.

[0127] The three-phase target modulation reference voltage can be determined as the space voltage vector. Based on the amplitude and angle of the space voltage vector in the stationary coordinate system, the corresponding sector position can be determined. Based on the volt-second balance, the initial equivalent action time of two adjacent basic vectors and a zero vector (or redundant small vector) in the sector position can be determined to ensure that the synthesized space voltage vector is close.

[0128] The neutral point potential state can be determined based on the voltage difference between the positive and negative busbars. Then, by combining the neutral point potential state, the proportion of the duration of the redundant small vector can be dynamically adjusted to determine the duration of the redundant vector.

[0129] For example, when the voltage difference between the positive and negative busbars is greater than 0 (i.e., the midpoint is biased upward), the duration of the redundant vector action that charges the lower capacitor is increased, and the duration of the redundant vector action that discharges the upper capacitor is reduced, thereby further enhancing the midpoint potential balance effect.

[0130] Based on the redundancy vector duration and the inverter topology's switching transistor configuration (4 transistors per phase, such as T1-T4), the switching transistor turn-on timing for each phase arm is generated. This turn-on timing is then converted into corresponding discrete switching drive signals (which can be PWM drive signals). Minimum on-time limits (to prevent damage from hard switching of the transistors) and over-modulation protection are applied to the switching drive signals to ensure their reliability.

[0131] The topology can be a three-level ANPC topology, or it can be replaced with any other three-level topology with a midpoint potential and the midpoint of the filter capacitor connected to the midpoint of the DC bus.

[0132] For example, assume the three-phase target compensation signal is , , The spatial vector is located in the second sector, and the duration of the fundamental vector's action is determined to be... , ( (Switching cycle), duration of redundant small vector action The voltage difference between the positive and negative busbars is greater than 0, indicating a slight upward bias. Therefore, the proportion of the lower capacitor charging component in the redundant small vector is adjusted from 50% to 60%, while the proportion of the upper capacitor discharging component is reduced to 40%. This ultimately generates... (High-level conduction duration 0.4) ), (High-level conduction duration 0.1) ), (High-level conduction duration 0.1) ), drive the inverter to output a matched three-level voltage.

[0133] In this application, the decoupling of midpoint potential balance control and grid voltage / current control is achieved through three-phase target modulation reference voltage, three-level SVPWM modulation and redundancy vector optimization. This ensures grid power quality (no line voltage distortion) and suppresses midpoint potential fluctuations through dynamic adjustment of the switching drive signal, thereby improving the reliability of midpoint potential balance and long-term operational stability of the system under low power factor and high modulation conditions.

[0134] The midpoint potential balancing method for suppressing the influence of common-mode voltage provided in this application acquires the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component. Based on the direct-axis and quadrature-axis inductor currents, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage. The voltage difference between the positive and negative bus is compensated to obtain the target compensation signal. The three-phase initial modulation reference voltage is then compensated using the target compensation signal to obtain the three-phase target modulation reference voltage. The three-phase switch drive signal is determined based on the three-phase target modulation reference voltage. Compensating the voltage difference between the positive and negative bus to obtain the target compensation signal ensures that the target compensation signal accurately matches the midpoint potential fluctuation. Then, the modulated three-phase initial modulation reference voltage is compensated using the target compensation signal to obtain the three-phase target modulation reference voltage, which in turn generates the switch drive signal. This signal can drive the inverter switching transistors to dynamically adjust their switching states, thereby suppressing midpoint potential fluctuations and improving the reliability of midpoint potential suppression.

[0135] Figure 4 A flowchart illustrating another method for suppressing the influence of common-mode voltage in this application, based on the present application, is shown below. Figure 4 In this embodiment Figure 2Based on the embodiments, a method for midpoint potential balancing to suppress the influence of common-mode voltage is described in detail. This method may include:

[0136] S401: Obtain the voltage difference between the positive and negative DC bus, the three-phase grid voltage, and the three-phase inductor current of the inverter.

[0137] It can collect three-phase current on the grid-connected side. , , Based on Kirchhoff's current law for LC filter circuits, the three-phase inductor current of the inverter is calculated using the following formula. , , ,

[0138]

[0139] Where C is the filter capacitor. , , These are the filter capacitor voltages for phases a, b, and c, respectively. Where phase a, ... Phase C and phase C are the three-phase output phases of the ANPC three-level inverter.

[0140] S402. Obtain the grid phase through a phase-locked loop.

[0141] The three-phase voltage of the power grid can be controlled through a phase-locked loop. , , Synchronous demodulation is performed to obtain the grid phase. .

[0142] in, , , The grid-side phase voltage, where N is the neutral point of the system or the midpoint of the DC bus, is the input signal for phase tracking by the phase-locked loop.

[0143] For example, the phase-locked loop can be a synchronous rotating coordinate system phase-locked loop (SRF-PLL).

[0144] S403. Determine the direct-axis inductor current and quadrature-axis inductor current based on the grid phase and the three-phase inductor current of the inverter.

[0145] Can be based on grid phase By transforming the abc / dq0 coordinates, the three-phase inductor current on the inverter side is... , , Converted to direct-axis inductor current in a synchronous rotating coordinate system and quadrature axis inductor current .

[0146] Specifically, based on grid phase As a synchronization reference, the inductor current in the three-phase stationary coordinate system is transformed and mapped to the dq coordinate system that rotates synchronously with the grid voltage vector, thereby realizing the DC quantization of AC quantities and facilitating subsequent closed-loop regulation.

[0147] Among them, the direct-axis inductor current Used to characterize the active power component of a system, quadrature-axis inductor current. Used to characterize the reactive power component of the system, providing a DC control target for subsequent current loop PI regulation and cross-decoupling control.

[0148] S404. Determine the direct-axis voltage component and quadrature-axis voltage component based on the grid phase and the three-phase voltage of the grid.

[0149] Based on the grid phase, the three-phase voltage of the grid can be transformed using the abc / dq0 coordinate system. , , Converted into direct-axis voltage components in a synchronous rotating coordinate system and cross-axis voltage components This provides the dq-axis reference signal for subsequent voltage modulation and current closed-loop control.

[0150] S405. Determine the direct-axis error signal based on the direct-axis inductor current and the direct-axis reference current, and perform proportional-integral adjustment processing on the direct-axis error signal to obtain the direct-axis adjustment signal.

[0151] Direct-axis reference current can be used Direct-axis inductor current The difference is determined as the direct axis error signal. .

[0152] The direct axis error signal can be controlled using a PI controller. Proportional-integral adjustment is performed to obtain the direct-axis adjustment signal. The transfer function of the PI controller can be found in the following formula:

[0153]

[0154] in, This is the complex frequency domain transfer function of the PI controller, indicating the dynamic mapping relationship between the controller output and the input error signal; It is a proportional coefficient used to improve the response speed of the current closed loop and quickly reduce current error; The integral coefficient is used to eliminate steady-state error and achieve zero steady-state error tracking of the direct-axis current; These are Laplace complex frequency domain variables used to describe the dynamic characteristics of the control system.

[0155] S406. Determine the quadrature axis error signal based on the quadrature axis inductor current and the quadrature axis reference current, and perform proportional-integral adjustment processing on the quadrature axis error signal to obtain the quadrature axis adjustment signal.

[0156] The quadrature axis reference current can be used quadrature axis inductor current The difference is determined as the cross-axis error signal. .

[0157] The quadrature axis error signal can be controlled by a PI controller. Proportional-integral adjustment is performed to obtain the quadrature-axis adjustment signal. For the transfer function of the PI controller, please refer to S405, which will not be repeated here.

[0158] S407. Determine the cross-coupling compensation term based on the direct-axis inductor current and the quadrature-axis inductor current.

[0159] Cross-coupling compensation terms can include direct-axis cross-coupling compensation terms and quadrature-axis cross-coupling compensation terms, which are used to counteract electromagnetic coupling interference between the d / q axes in a synchronous rotating coordinate system, realize decoupling control of the d / q axis currents, and avoid the influence of changes in the current of one axis on the current of the other axis.

[0160] The electromagnetic coupling characteristics of the output-side filter inductor of the ANPC inverter generate a coupling voltage term in a synchronous rotating coordinate system. This coupling term is related to the inductor parameter L and the grid angular frequency. The current is proportional to the current on the other axis and is a key disturbance affecting the accuracy of the current loop control.

[0161] Direct axis cross compensation term Used to cancel the coupling interference of quadrature axis current to direct axis voltage, based on the quadrature axis inductor current. Filter inductance L and mains angular frequency The calculation yields the following expression:

[0162]

[0163] Cross-axis compensation term Used to cancel the coupling interference of direct-axis current to quadrature-axis voltage, based on the direct-axis inductor current. Filter inductance L and mains angular frequency The calculation yields the following expression:

[0164]

[0165] in, L is the grid angular frequency (obtained by differentiating the grid phase θ output by the S402 phase-locked loop, or directly taking the grid rated angular frequency), and L is the inductance value of the inverter output-side filter inductor (consistent with the inductance parameters of the LC filter in S401).

[0166] In this application, the electromagnetic coupling interference of the d / q axis is accurately canceled by calculating the coupling term based on the inductor current and the grid parameters, thereby improving the decoupling control effect and steady-state control accuracy of the current loop.

[0167] S408. Determine the three-phase initial modulation reference voltage based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term.

[0168] Specifically, through the direct axis cross compensation term Adjustment signal for the direct axis Feedforward compensation is performed to obtain the direct-axis modulated voltage reference. ; through axis intersection compensation terms Adjustment signal for cross-axis Compensation processing is performed to obtain the quadrature-axis modulated voltage reference. Based on the grid phase θ and inverse coordinate transformation, the direct-axis modulated voltage reference is determined. and cross-axis modulated voltage reference The corresponding three-phase adjustment voltage is obtained, and the three-phase adjustment voltage is pre-modulated to obtain the initial three-phase modulation reference voltage. , , .

[0169] Considering electromagnetic coupling interference and grid voltage feedforward in a synchronous rotating coordinate system, the synthesis expression for the direct-axis and quadrature-axis modulated voltage references is as follows:

[0170]

[0171] in, The cross-compensation term is superimposed in reverse on the direct axis to cancel the coupling interference of the quadrature axis current on the direct axis; The positive superposition of cross compensation terms on the quadrature axis cancels out the coupling interference of the direct axis current on the quadrature axis; and To superimpose the grid voltage dq component and achieve grid back EMF feedforward compensation.

[0172] SVPWM preprocessing can be used to perform amplitude clamping on the three-phase regulating voltage to obtain the initial three-phase modulation reference voltage. , , .

[0173] In this application, by superimposing compensation terms and feeding forward from the power grid, the synthesis of dq-axis modulation voltage and the standardized conversion of three-phase voltage reference are realized. This not only ensures the accuracy of current decoupling control, but also reserves a superposition interface for midpoint potential balance compensation, thereby improving the compatibility and control effect of the entire control scheme.

[0174] To facilitate understanding, the following will be combined with... Figure 5 The embodiments of this application provide S405-S408, which, through a PI controller and a feedforward decoupling circuit, control the direct-axis inductor current. and quadrature axis inductor current After processing, a direct-axis modulated voltage reference is obtained. and cross-axis modulated voltage reference The execution process will be further explained.

[0175] Figure 5 This is a schematic diagram of a current loop PI regulation and feedforward decoupling control provided in this application. Please refer to... Figure 5 , direct axis reference current With direct-axis inductor current The difference is calculated to obtain the direct-axis current error signal. The error signal The input transfer function is The PI controller outputs a direct-axis adjustment signal. The quadrature-axis reference current quadrature axis inductor current The difference is determined as the cross-axis error signal. The error signal The input transfer function is The PI controller outputs a quadrature axis adjustment signal. Based on the filter inductance L and the grid angular frequency ω, the cross-coupling compensation term is calculated as a direct-axis cross-coupling compensation term. and cross-axis compensation term Finally, the direct-axis capacitor voltage dq component is converted into the capacitor voltage. Cross-axis capacitor voltage These signals are superimposed onto the decoupled adjustment signals of the direct axis and quadrature axis, respectively, to obtain the final direct-axis modulated voltage reference. and cross-axis modulated voltage reference .

[0176] S409. The voltage difference between the positive and negative busbars is adjusted by the controller to obtain the first compensation signal.

[0177] The controller can be a QPR controller, and the QPR controller transfer function is:

[0178]

[0179] in, The complex frequency domain transfer function of the QPR controller characterizes the dynamic mapping relationship between the controller output and the input voltage difference. The proportional coefficient is used to improve the compensation response speed and quickly suppress dynamic fluctuations in the midpoint potential. This is the resonant gain coefficient, used to enhance the ability to adjust characteristic frequency components and achieve zero steady-state error tracking; The resonant angular frequency is typically set to twice the fundamental frequency of the power grid (e.g., (corresponding to a 50Hz power grid), precisely matching the second harmonic fluctuation characteristics of the midpoint potential; These are Laplace complex frequency domain variables used to describe the dynamic characteristics of the control system.

[0180] The voltage difference between the positive and negative bus can be used as the input of the QPR controller, and the first compensation signal can be used as the output of the QPR controller. The dynamic compensation amount of the first compensation signal, which is in sync with the midpoint potential fluctuation, is used to be superimposed on the three-phase modulation reference voltage to correct the switch drive signal and balance the charging and discharging current of the DC side capacitor.

[0181] S410. Based on the filter, the voltage difference between the positive and negative busbars is subjected to a second adjustment process to obtain a second compensation signal.

[0182] The filter can be a Butterworth bandpass filter, whose complex frequency domain transfer function is:

[0183]

[0184] in, The complex frequency domain transfer function of the bandpass filter characterizes the frequency response relationship between the filtered output signal and the input voltage difference. This is the passband gain of the filter (usually set to 1 to ensure that the signal amplitude within the passband is not attenuated). The center angular frequency of the filter is kept consistent with the resonant angular frequency of the QPR controller and is set to twice the fundamental frequency of the power grid to accurately match the second harmonic fluctuation characteristics of the midpoint potential. For Laplace complex frequency domain variables; The Q value is the filter quality factor, which determines the passband bandwidth (the larger the Q value, the narrower the passband and the sharper the frequency selection characteristics; it is usually set to 1 to 5 to balance frequency selection accuracy and dynamic response speed).

[0185] Specifically, based on the filter, the voltage difference between the positive and negative bus is filtered to obtain a specific frequency component of the midpoint potential fluctuation; the specific frequency component is then determined as the second compensation signal.

[0186] Among them, a specific frequency component can be a second harmonic specific frequency component.

[0187] The voltage difference between the positive and negative busbars is input into a bandpass filter, which only allows the center frequency to be input. The nearby second harmonic fluctuation component passes through, while suppressing DC bias and high-frequency noise interference, outputting a pure second harmonic fluctuation component, which is the second compensation signal.

[0188] In this application, a bandpass filter is used to accurately select the frequency and suppress noise of the second harmonic fluctuation of the midpoint potential, thereby achieving pure extraction and preprocessing of the compensation signal, improving the targeting and steady-state accuracy of the subsequent QPR controller adjustment, and enhancing the system's ability to balance the midpoint potential under complex operating conditions such as low power factor and high modulation.

[0189] S411. The first compensation signal and the second compensation signal are superimposed to obtain the target compensation signal.

[0190] The first compensation signal (dynamically adjusted second harmonic compensation amount) from the QPR controller and the second compensation signal (preprocessed pure second harmonic fluctuation component) from the bandpass filter are linearly superimposed, and then the output amplitude is constrained by the limiting stage to finally obtain the target compensation signal.

[0191] Target compensation signal The synthesis formula is:

[0192]

[0193] in, As the first compensation signal, This is the second compensation signal. To compensate for the weighting coefficient (with a value ranging from 0 to 1, used to balance the contribution of dynamic adjustment and fluctuation components, and can be adaptively adjusted according to system operating conditions).

[0194] The superimposed signal needs to pass through a limiting circuit to limit the output amplitude to a certain value. Within the range ( (This refers to the total voltage of the DC bus) to avoid excessive compensation, which could cause the modulation voltage to exceed the safe range and lead to over-modulation or overvoltage of the switching transistor.

[0195] The target compensation signal is the zero-sequence compensation voltage, which will be superimposed on the three-phase initial modulation reference voltage. The switching timing is dynamically adjusted by modifying the SVPWM modulation command to balance the charging and discharging current of the upper and lower capacitors on the DC side, and finally suppress the midpoint potential fluctuation.

[0196] S412. The three-phase initial modulation reference voltage is compensated by the target compensation signal to obtain the three-phase target modulation reference voltage.

[0197] S413. Determine the three-phase switch drive signal based on the three-phase target modulation reference voltage.

[0198] The execution process of S412 and S413 can be found in the execution process of S204 and S205, and will not be repeated here.

[0199] The midpoint potential balancing method for suppressing the influence of common-mode voltage provided in this application acquires the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component. Based on the direct-axis and quadrature-axis inductor currents, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage. The voltage difference between the positive and negative bus is compensated to obtain the target compensation signal. The three-phase initial modulation reference voltage is then compensated using the target compensation signal to obtain the three-phase target modulation reference voltage. The three-phase switch drive signal is determined based on the three-phase target modulation reference voltage. Compensating the voltage difference between the positive and negative bus to obtain the target compensation signal ensures that the target compensation signal accurately matches the midpoint potential fluctuation. Then, the modulated three-phase initial modulation reference voltage is compensated using the target compensation signal to obtain the three-phase target modulation reference voltage, which in turn generates the switch drive signal. This signal can drive the inverter switching transistors to dynamically adjust their switching states, thereby suppressing midpoint potential fluctuations and improving the reliability of midpoint potential suppression.

[0200] Figure 6 A schematic diagram of a midpoint potential balancing device for suppressing the influence of common-mode voltage provided in this application. Please refer to... Figure 6 The midpoint potential balancing device 600 for suppressing the influence of common-mode voltage includes an acquisition module 601, a modulation processing module 602, a first compensation processing module 603, a second compensation processing module 604, and a determination module 605.

[0201] The acquisition module 601 is used to acquire the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component;

[0202] The modulation processing module 602 is used to modulate the direct-axis voltage component and the quadrature-axis voltage component according to the direct-axis inductor current and the quadrature-axis inductor current to obtain the three-phase initial modulation reference voltage.

[0203] The first compensation processing module 603 is used to perform compensation analysis and processing on the voltage difference between the positive and negative busbars to obtain the target compensation signal.

[0204] The second compensation processing module 604 is used to perform compensation processing on the three-phase initial modulation reference voltage through the target compensation signal to obtain the three-phase target modulation reference voltage.

[0205] The determination module 605 is used to determine the three-phase switch drive signal based on the three-phase target modulation reference voltage. The three-phase switch drive signal is used to control the neutral point potential.

[0206] In one possible implementation, the modulation processing module 602 is specifically used to modulate the direct-axis voltage component and the quadrature-axis voltage component according to the direct-axis inductor current and the quadrature-axis inductor current to obtain a three-phase initial modulation reference voltage, including:

[0207] The direct-axis error signal is determined based on the direct-axis inductor current and the direct-axis reference current, and the direct-axis error signal is processed by proportional-integral adjustment to obtain the direct-axis adjustment signal.

[0208] The quadrature axis error signal is determined based on the quadrature axis inductor current and the quadrature axis reference current, and the quadrature axis error signal is processed by proportional-integral adjustment to obtain the quadrature axis adjustment signal;

[0209] Determine the cross-coupling compensation term based on the direct-axis inductor current and the quadrature-axis inductor current;

[0210] The three-phase initial modulation reference voltage is determined based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term.

[0211] In one possible implementation, the cross-coupling compensation term includes a direct-axis cross-coupling compensation term and a quadrature-axis cross-coupling compensation term; the modulation processing module 602 is specifically used to determine the three-phase initial modulation reference voltage based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term, including:

[0212] By using the direct-axis cross compensation term, the direct-axis adjustment signal is fed forward to obtain the direct-axis modulation voltage reference.

[0213] By using the cross-axis cross compensation term, the cross-axis adjustment signal is fed forward to obtain the cross-axis modulation voltage reference;

[0214] Based on the grid phase and coordinate inverse transformation, the three-phase adjustment voltages corresponding to the direct-axis modulation voltage reference and the quadrature-axis modulation voltage reference are determined, and the three-phase adjustment voltages are pre-processed to obtain the initial three-phase modulation reference voltages.

[0215] In one possible implementation, a first compensation analysis process is performed on the voltage difference between the positive and negative busbars to obtain a target compensation signal, including a module specifically used for:

[0216] The controller performs a first adjustment process on the voltage difference between the positive and negative busbars to obtain a first compensation signal.

[0217] Based on the filter, the voltage difference between the positive and negative busbars is subjected to a second adjustment process to obtain a second compensation signal;

[0218] The first compensation signal and the second compensation signal are superimposed to obtain the target compensation signal.

[0219] In one possible implementation, the first compensation processing module 603 is specifically used to perform a second adjustment process on the positive and negative bus voltage difference based on the filter to obtain a second compensation signal, including:

[0220] Based on the filter, the voltage difference between the positive and negative busbars is filtered to obtain the specific frequency component of the midpoint potential fluctuation.

[0221] A specific frequency component is determined as the second compensation signal.

[0222] In one possible implementation, the three-phase switch drive signal is determined based on the three-phase modulation reference voltage, including a module specifically used for:

[0223] Based on the three-phase target modulation reference voltage, determine the initial equivalent duration of capacitor charging for the inverter.

[0224] Based on the midpoint potential state of the inverter, the initial equivalent duration is adjusted to obtain the redundant vector duration of the capacitor charging corresponding to the inverter.

[0225] Based on the duration of the redundancy vector and the inverter topology, the switching timing of the three-phase bridge arm is generated.

[0226] Generate the three-phase switch drive signals corresponding to the turn-on timing of the switching transistors in the three-phase bridge arm.

[0227] In one possible implementation, the module for acquiring the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component, includes a module specifically used for:

[0228] Obtain the voltage difference between the positive and negative DC bus, the three-phase grid voltage, and the three-phase inductor current of the inverter;

[0229] The phase of the power grid is obtained through a phase-locked loop;

[0230] Determine the direct-axis inductor current and quadrature-axis inductor current based on the grid phase and the three-phase inductor current of the inverter;

[0231] Based on the grid phase and the three-phase grid voltage, determine the direct-axis voltage component and the quadrature-axis voltage component.

[0232] The midpoint potential balancing device for suppressing the influence of common-mode voltage provided in this embodiment can perform the method provided in the above-described method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0233] Figure 7A schematic diagram of the structure of an electronic device provided in this application. Please refer to [link / reference]. Figure 7 The electronic device 700 may include a processor 701 and a memory 702. Exemplarily, the processor 701 and the memory 702 are interconnected via a bus 703.

[0234] Memory 702 stores instructions executed by the computer;

[0235] The processor 701 executes computer execution instructions stored in the memory 702, causing the processor 701 to perform a midpoint potential balancing method for suppressing the influence of common-mode voltage as described in the above method embodiment.

[0236] Accordingly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the midpoint potential balancing method for suppressing the influence of common-mode voltage as described in the above-described method embodiments.

[0237] Accordingly, embodiments of this application may also provide a computer program product, including a computer program, which, when executed by a processor, can implement the midpoint potential balancing method for suppressing the influence of common-mode voltage as shown in the above method embodiments.

[0238] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0239] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0240] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0241] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0242] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0243] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0244] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0245] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0246] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for balancing the midpoint potential to suppress the influence of common-mode voltage, characterized in that, include: Obtain the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component; Based on the direct-axis inductor current and the quadrature-axis inductor current, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage; The voltage difference between the positive and negative busbars is analyzed and processed to obtain the target compensation signal; The three-phase initial modulation reference voltage is compensated using the target compensation signal to obtain the three-phase target modulation reference voltage. Based on the three-phase target modulation reference voltage, a three-phase switch drive signal is determined, which is used to control the midpoint potential.

2. The method according to claim 1, characterized in that, Based on the direct-axis inductor current and the quadrature-axis inductor current, the direct-axis voltage component and the quadrature-axis voltage component are modulated to obtain the three-phase initial modulation reference voltage, including: The direct-axis error signal is determined based on the direct-axis inductor current and the direct-axis reference current, and the direct-axis error signal is subjected to proportional-integral adjustment processing to obtain the direct-axis adjustment signal. The quadrature axis error signal is determined based on the quadrature axis inductor current and the quadrature axis reference current, and the quadrature axis error signal is subjected to proportional-integral adjustment processing to obtain the quadrature axis adjustment signal; Based on the direct-axis inductor current, quadrature-axis inductor current, and inductance parameters, determine the cross-coupling compensation term; The three-phase initial modulation reference voltage is determined based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term.

3. The method according to claim 2, characterized in that, The cross-coupling compensation term includes a direct-axis cross-coupling compensation term and a quadrature-axis cross-coupling compensation term; the three-phase initial modulation reference voltage is determined based on the direct-axis adjustment signal, the quadrature-axis adjustment signal, and the cross-coupling compensation term, including: The direct-axis modulation voltage reference is obtained by performing feedforward compensation processing on the direct-axis adjustment signal through the direct-axis cross compensation term. The quadrature axis cross-compensation term is used to perform feedforward compensation processing on the quadrature axis adjustment signal to obtain the quadrature axis modulation voltage reference; Based on the grid phase and coordinate inverse transformation, the three-phase adjustment voltages corresponding to the direct-axis modulation voltage reference and the quadrature-axis modulation voltage reference are determined, and the three-phase adjustment voltages are pre-modulated to obtain the three-phase initial modulation reference voltages.

4. The method according to claim 1, characterized in that, The voltage difference between the positive and negative busbars is analyzed and processed to obtain the target compensation signal, including: The controller performs a first adjustment process on the voltage difference between the positive and negative busbars to obtain a first compensation signal. Based on the filter, the voltage difference between the positive and negative busbars is subjected to a second adjustment process to obtain a second compensation signal; The first compensation signal and the second compensation signal are superimposed to obtain the target compensation signal.

5. The method according to claim 4, characterized in that, Based on the filter, a second adjustment process is performed on the voltage difference between the positive and negative buses to obtain a second compensation signal, including: Based on the filter, the voltage difference between the positive and negative busbars is filtered to obtain a specific frequency component of the midpoint potential fluctuation. The specific frequency component is determined as the second compensation signal.

6. The method according to claim 1, characterized in that, The three-phase switch drive signal is determined based on the three-phase target modulation reference voltage. include: Based on the three-phase target modulation reference voltage, determine the initial equivalent duration of capacitor charging for the inverter. Based on the midpoint potential state of the inverter, the initial equivalent duration is adjusted to obtain the redundant vector duration of the capacitor charging corresponding to the inverter. Based on the duration of the redundancy vector and the topology of the inverter, the switching timing of the three-phase bridge arm is generated; Generate the three-phase switch drive signals corresponding to the turn-on timing of the switching transistors of the three-phase bridge arm.

7. The method according to claim 1, characterized in that, Obtain the voltage difference between the positive and negative DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage components and the quadrature-axis voltage components, including: Obtain the positive and negative bus voltage difference of the DC bus, the three-phase voltage of the power grid, and the three-phase inductor current of the inverter; The phase of the power grid is obtained through a phase-locked loop; The direct-axis inductor current and the quadrature-axis inductor current are determined based on the grid phase and the three-phase inductor current of the inverter. The direct-axis voltage component and the quadrature-axis voltage component are determined based on the grid phase and the three-phase voltage of the grid.

8. A midpoint potential balancing device for suppressing the influence of common-mode voltage, characterized in that, It includes an acquisition module, a modulation processing module, a first compensation processing module, a second compensation processing module, and a determination module: The acquisition module is used to acquire the positive and negative bus voltage difference of the DC bus, the grid phase, the direct-axis inductor current and the quadrature-axis inductor current, as well as the direct-axis voltage component and the quadrature-axis voltage component; The modulation processing module is used to modulate the direct-axis voltage component and the quadrature-axis voltage component according to the direct-axis inductor current and the quadrature-axis inductor current to obtain the three-phase initial modulation reference voltage. The first compensation processing module is used to perform compensation analysis processing on the voltage difference between the positive and negative busbars to obtain the target compensation signal; The second compensation processing module is used to perform compensation processing on the three-phase initial modulation reference voltage through the target compensation signal to obtain the three-phase target modulation reference voltage; The determining module is used to determine the three-phase switch drive signal based on the three-phase target modulation reference voltage, and the three-phase switch drive signal is used to control the midpoint potential.

9. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory to implement the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1 to 7.

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