Method, device and system for balancing the dc bus voltage of an inverter

Abstract

This application discloses a DC bus voltage balance control method, apparatus, and system for an inverter, belonging to the field of power electronics technology. The control method includes: acquiring the difference between the positive DC bus voltage and the negative DC bus voltage; when the absolute value of the difference between the positive and negative DC bus voltages is greater than a voltage difference threshold, acquiring a common-mode voltage compensation amount based on the difference between the positive and negative DC bus voltages; and adjusting the difference between the positive and negative DC bus voltages based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive and negative DC bus voltages is less than or equal to the voltage difference threshold. The DC bus voltage balance control method, apparatus, and system for an inverter disclosed in this application, by adjusting the difference between the positive and negative DC bus voltages based on the common-mode voltage compensation amount, can more efficiently suppress the imbalance between the positive and negative DC bus voltages and can more quickly and effectively restore the balanced state of the positive and negative DC bus voltages.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a method, device and system for DC bus voltage balance control of an inverter. Background Technology

[0002] In related technologies, three-phase three-wire inverters (such as three-phase T-type three-level inverters, three-phase I-type three-level inverters, or traditional two-level inverters) are widely used in new energy power generation and uninterruptible power supply (UPS) fields. Three-phase three-wire inverters typically have two sets of positive and negative bus capacitors connected in series on the DC side. During the pre-charging phase before inverter startup, slight differences in pre-charging circuit parameters (such as resistance and / or relay contact resistance), inconsistencies in the capacitance values ​​of the positive and negative bus capacitors, and at least one of the equivalent series resistance (ESR) can lead to unequal voltages on the positive and negative bus capacitors, resulting in a DC bus voltage imbalance.

[0003] The imbalance of positive and negative DC bus voltages poses at least the following hazards: First, it threatens the safety of power devices, potentially causing at least one switching transistor to experience a voltage exceeding its rated value, leading to transistor breakdown and damage. Second, during grid connection, the imbalance of positive and negative DC bus voltages can cause common-mode current in the output, affecting grid connection quality and possibly triggering protection mechanisms. Third, it degrades control performance, affecting the symmetry of the inverter output voltage and potentially preventing the inverter system from starting normally.

[0004] Therefore, how to efficiently suppress the voltage imbalance between positive and negative DC buses has become a technical issue that urgently needs to be addressed in this field. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method, apparatus, and system for DC bus voltage balance control of an inverter, which can more efficiently suppress positive and negative DC bus voltage imbalance.

[0006] In a first aspect, this application provides a DC bus voltage balance control method for an inverter, the method comprising: Obtain the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter; When the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold, the common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage. Based on the common-mode voltage compensation amount, the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

[0007] According to the DC bus voltage balance control method of the inverter of this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, a common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, and the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This method can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0008] According to one embodiment of this application, adjusting the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount includes: Based on the common-mode voltage compensation and the three-phase modulation wave, drive signals for the switching devices in the inverter are generated; the drive signals are used to adjust the positive DC bus voltage and the negative DC bus voltage.

[0009] According to one embodiment of this application, generating drive signals for the switching devices in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave includes: Generate the initial three-phase modulated wave; The common-mode voltage compensation is injected into the initial three-phase modulation wave to generate a compensated three-phase modulation wave; Based on the compensated three-phase modulated wave, the drive signal for each of the switching devices is generated.

[0010] According to one embodiment of this application, generating the drive signal for each of the switching devices based on the compensated three-phase modulated wave includes: Based on the compensated three-phase modulated wave, a pulse width modulation signal corresponding to each of the switching devices is generated as the driving signal of the switching device.

[0011] According to one embodiment of this application, obtaining the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage includes: Based on the proportional-integral-derivative (PID) control algorithm, the common-mode voltage compensation amount is obtained according to the difference between the positive DC bus voltage and the negative DC bus voltage.

[0012] According to one embodiment of this application, after generating drive signals for each switching device in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave, the method further includes: The drive signal of each of the switching devices is input to each of the switching devices respectively.

[0013] Secondly, this application provides a DC bus voltage balance control device for an inverter, the device comprising: The differential voltage acquisition module is used to acquire the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter upon receiving a start command. The compensation amount acquisition module is used to acquire the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold. The control module is used to adjust the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

[0014] According to the DC bus voltage balance control device of the inverter of this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, the common mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, and the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted based on the common mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0015] Thirdly, this application provides an inverter system, including an inverter and a DC bus voltage balance control device for the inverter as described in the second aspect above.

[0016] According to the inverter system of this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, a common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage. Based on the common-mode voltage compensation amount, the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0017] Fourthly, this application provides an inverter, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the DC bus voltage balance control method of the inverter as described in the first aspect above.

[0018] Fifthly, this application provides a non-volatile computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the DC bus voltage balance control method for an inverter as described in the first aspect above.

[0019] In a sixth aspect, this application provides a chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being used to run programs or instructions to implement the DC bus voltage balance control method for inverters as described in the first aspect.

[0020] In a seventh aspect, this application provides a computer program product, including a computer program that, when executed by a processor, implements the DC bus voltage balance control method for an inverter as described in the first aspect above.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is one of the flowcharts illustrating the DC bus voltage balance control method for an inverter provided in this application embodiment; Figure 2 This is a second schematic flowchart of the DC bus voltage balance control method for an inverter provided in the embodiments of this application; Figure 3 This is a schematic diagram of the DC bus voltage balance control device for the inverter provided in this application embodiment; Figure 4 This is a schematic diagram of the inverter system provided in the embodiments of this application; Figure 5 This is a schematic diagram of the inverter provided in the embodiment of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0024] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] The following description, in conjunction with the accompanying drawings, details the DC bus voltage balance control method, DC bus voltage balance control device, inverter system, inverter, and readable storage medium provided in this application through specific embodiments and application scenarios.

[0026] The DC bus voltage balance control method of the inverter can be applied to the terminal, and can be executed by the hardware or software in the terminal.

[0027] The DC bus voltage balance control method for inverters provided in this application embodiment can be executed by an electronic device or a functional module or entity in an electronic device that can implement the DC bus voltage balance control method for inverters. The electronic devices mentioned in this application embodiment include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The following uses an electronic device as the execution subject to illustrate the DC bus voltage balance control method for inverters provided in this application embodiment.

[0028] like Figure 1 As shown, the DC bus voltage balance control method of the inverter includes steps 110, 120 and 130.

[0029] In actual implementation, the DC bus voltage balance control method for inverters provided in this application embodiment can be used to control the DC bus voltage of a three-phase inverter, so that the DC bus voltage of the inverter is balanced.

[0030] In some embodiments, the DC bus voltage balance control method for inverters provided in this application can be used to control the DC bus voltage of a three-phase inverter during the no-load phase before grid-connected operation or off-grid operation, so as to balance the DC bus voltage of the inverter. Alternatively, it can be used to control the DC bus voltage of a three-phase inverter during other phases, so as to balance the DC bus voltage of the inverter.

[0031] Step 110: Obtain the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0032] In actual operation, the positive DC bus voltage and negative DC bus voltage of the inverter can be sampled separately to obtain the positive DC bus voltage and negative DC bus voltage of the inverter.

[0033] In some embodiments, the positive DC bus voltage and the voltage between the positive and negative DC buses of the inverter can be sampled respectively to obtain the positive DC bus voltage and the voltage between the positive and negative DC buses of the inverter; after obtaining the positive DC bus voltage and the voltage between the positive and negative DC buses of the inverter, the difference between the voltage between the positive and negative DC buses of the inverter and the positive DC bus voltage of the inverter can be obtained as the negative DC bus voltage of the inverter.

[0034] In some embodiments, the negative DC bus voltage and the voltage between the positive and negative DC buses of the inverter can be sampled respectively to obtain the negative DC bus voltage and the voltage between the positive and negative DC buses of the inverter. After obtaining the negative DC bus voltage and the voltage between the positive and negative DC buses of the inverter, the difference between the voltage between the positive and negative DC buses of the inverter and the negative DC bus voltage of the inverter can be obtained as the positive DC bus voltage of the inverter.

[0035] In some embodiments, two DC bus capacitors can be connected in series between the positive and negative DC buses of the inverter, for example... Figure 4 C1 and C2 in the diagram. The voltage between the positive DC bus (BUS+) of the inverter and the connection point of the two DC bus capacitors mentioned above is the positive DC bus voltage, and the voltage between the connection point of the two DC bus capacitors and the negative DC bus (BUS-) of the inverter is the negative DC bus voltage. Therefore, the voltage between the positive DC bus (BUS+) of the inverter and the connection point of the two DC bus capacitors mentioned above, and the voltage between the connection point of the two DC bus capacitors and the negative DC bus (BUS-) of the inverter can be sampled to obtain the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0036] In some embodiments, the positive DC bus voltage, negative DC bus voltage, or voltage between the positive and negative DC buses of the inverter can be sampled using an analog-to-digital converter (ADC).

[0037] In some embodiments, after obtaining the positive DC bus voltage and the negative DC bus voltage of the inverter, the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter can be obtained.

[0038] It is understandable that the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter can be obtained by the following formula: ΔV = positive DC bus voltage - negative DC bus voltage.

[0039] Step 120: When the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold, obtain the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage.

[0040] In actual operation, after obtaining the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter, it can be determined whether the absolute value of the difference ΔV, |ΔV|, is greater than the voltage difference threshold Vth. The voltage difference threshold Vth is a positive value.

[0041] It should be noted that if the absolute value of the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter, |ΔV|, is greater than the voltage difference threshold Vth, it indicates that the positive DC bus voltage and the negative DC bus voltage of the inverter are significantly different, and the positive and negative DC bus voltages of the inverter are unbalanced. If the absolute value of the difference ΔV between the positive DC bus voltage and the negative DC bus voltage, |ΔV|, is less than or equal to the voltage difference, it indicates that the positive DC bus voltage and the negative DC bus voltage of the inverter are significantly different, and the positive and negative DC bus voltages of the inverter can be considered balanced.

[0042] It should be noted that the differential voltage threshold Vth can be determined based on the actual situation and operational requirements of the inverter, such as the voltage between the positive and negative DC buses. This application does not limit the specific value of the differential voltage threshold Vth.

[0043] In some embodiments, when the absolute value of the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter, |ΔV|, is greater than the voltage difference threshold Vth, the common-mode voltage compensation amount ΔVcm can be obtained based on the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0044] It should be noted that common mode voltage is the average phasor voltage that occurs between each conductor and a specified reference point (usually ground or rack).

[0045] In this embodiment, the common-mode voltage Vcm is the average voltage of the three-phase output terminals of the inverter relative to the DC side reference point, and can be calculated using the following formula: Vcm=(V AO +V BO +V CO ) / 3.

[0046] Among them, V AO V BO V CO These represent the voltages of the inverter's A-phase input terminal relative to the DC-side reference point, the B-phase input terminal relative to the DC-side reference point, and the C-phase input terminal relative to the DC-side reference point, respectively.

[0047] It should be noted that the common-mode voltage compensation amount ΔVcm is the compensation amount corresponding to the common-mode voltage Vcm.

[0048] In some embodiments, the control objective can be to reduce the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage to less than or equal to the voltage difference threshold. A target control algorithm is used to calculate and determine the common-mode voltage compensation amount ΔVcm based on the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0049] It should be noted that the specific target control algorithm used is not limited in the embodiments of this application. For example, the target control algorithm may be a proportional-integral-differential (PID) control algorithm, a fuzzy control algorithm, or an optimal control algorithm, etc.

[0050] Step 130: Based on the common-mode voltage compensation, adjust the difference between the positive DC bus voltage and the negative DC bus voltage so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

[0051] In actual implementation, the common-mode voltage compensation amount ΔVcm can be used as the basis for adjusting the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter. Based on the common-mode voltage compensation amount ΔVcm, the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter is adjusted so that the absolute value of the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter, |ΔV|, can be reduced to less than or equal to the voltage difference threshold Vth, thereby restoring the balance of the positive and negative DC bus voltages of the inverter.

[0052] It should be noted that, based on the common-mode voltage compensation amount ΔVcm, the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter is adjusted. Specifically, this can include, based on the common-mode voltage compensation amount ΔVcm, dynamically and in a closed loop, adjusting the charging and discharging current of the positive and negative DC buses of the inverter, thereby transferring the energy of the DC bus with the higher voltage to the side with the lower voltage, and ultimately achieving voltage balance between the positive and negative DC buses of the inverter.

[0053] According to the DC bus voltage balance control method for inverters provided in this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, a common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, and the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This method can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and can more quickly and effectively restore the balance of the positive and negative DC bus voltages of the inverter.

[0054] In some embodiments of this application, adjusting the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount includes: generating drive signals for the switching devices in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave; the drive signals are used to adjust the positive DC bus voltage and the negative DC bus voltage.

[0055] In actual implementation, the common-mode voltage compensation amount ΔVcm can be injected into the three-phase modulation wave. After injecting the common-mode voltage compensation amount ΔVcm into the three-phase modulation wave, the drive signals of each switching device in the inverter can be generated based on the three-phase modulation wave with the injected common-mode voltage compensation amount ΔVcm.

[0056] It should be noted that each switching device in the inverter can change its switching state under the drive of its own drive signal, thereby transferring energy from the DC bus with higher voltage to the DC bus with lower voltage, thus adjusting the difference ΔV between the positive and negative DC bus voltages of the inverter, and ultimately achieving voltage balance between the positive and negative DC buses of the inverter.

[0057] It should be noted that the three-phase modulated wave is generated based on the amplitude, frequency and phase of the grid voltage, with each of the three phases (A, B and C) corresponding to its own modulation wave.

[0058] In some embodiments, the drive signal for the switching devices in the inverter can be a pulse width modulation (PWM) signal or other forms of modulation signal.

[0059] It should be noted that when the positive DC bus voltage of the inverter is high (i.e., the positive DC bus voltage is greater than the negative DC bus voltage), the duration of the positive half-cycle of the drive signal of the switching device can be longer than the duration of the negative half-cycle, consuming more voltage from the positive DC bus. Energy is transferred from the higher voltage positive DC bus to the lower voltage negative DC bus, thus balancing the positive and negative DC bus voltages. Conversely, when the negative DC bus voltage of the inverter is high (i.e., the positive DC bus voltage is less than the negative DC bus voltage), the duration of the positive half-cycle of the drive signal of the switching device can be shorter than the duration of the negative half-cycle, consuming more voltage from the negative DC bus. Energy is transferred from the higher voltage negative DC bus to the lower voltage positive DC bus, thus balancing the positive and negative DC bus voltages.

[0060] According to the DC bus voltage balance control method for inverters provided in this application embodiment, by injecting common-mode voltage compensation into a three-phase modulation wave, and generating drive signals for the switching devices in the inverter based on this, the switching devices in the inverter can change their switching states accordingly under the drive of their own drive signals, so that energy is transferred from the DC bus with higher voltage to the DC bus with lower voltage. This adjusts the difference between the positive and negative DC bus voltages of the inverter, making the absolute value of the difference between the positive and negative DC bus voltages less than or equal to the voltage difference threshold. This can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and more quickly and effectively restore the balance of the positive and negative DC bus voltages of the inverter.

[0061] In some embodiments of this application, the drive signal for the switching devices in the inverter is generated based on the common-mode voltage compensation amount and the three-phase modulation wave, including: generating an initial three-phase modulation wave.

[0062] In actual implementation, a corresponding modulation wave can be generated based on the amplitude, frequency, and phase of the grid voltage. The aforementioned modulation wave is the initial three-phase modulation wave, which can be denoted as (Va, Vb, Vc).

[0063] It is understandable that the initial three-phase modulated wave (Va, Vb, Vc) can be a symmetrical three-phase AC signal with zero amplitude and the frequency of the power grid.

[0064] The common-mode voltage compensation is injected into the initial three-phase modulation wave to generate the compensated three-phase modulation wave.

[0065] In actual execution, after generating the initial three-phase modulation wave (Va, Vb, Vc), the common-mode voltage compensation amount ΔVcm can be injected into the initial three-phase modulation wave to generate the compensated three-phase modulation wave (Va', Vb', Vc').

[0066] Where Va'=Va+ΔVcm, Vb'=Vb+ΔVcm, Vc'=Vb+ΔVcm.

[0067] Based on the compensated three-phase modulated wave, a drive signal for each switching device is generated.

[0068] In actual execution, after generating the compensated three-phase modulated wave (Va', Vb', Vc'), it can be converted into the drive signal of each switching device in the inverter based on the modulation method adopted by the inverter.

[0069] It should be noted that the modulation method used in this inverter can be phase shift modulation, pulse width modulation, phase shift plus duty cycle modulation, or resonant modulation, etc.

[0070] In some embodiments, the switching state of each switching device in the inverter during each time period of a switching cycle can be determined based on the modulation method used in the inverter (i.e., which time periods in a switching cycle are in the on state and which time periods are in the off state; in extreme cases, it can also be kept in the on state or off state throughout a switching cycle). For each switching device in the inverter, with the goal of controlling the switching device to achieve the aforementioned determined switching state during each time period of a switching cycle, the compensated three-phase modulation wave (Va', Vb', Vc') can be converted into a drive signal for the switching device, thereby enabling the switching device to achieve the aforementioned determined switching state during each time period of a switching cycle under the drive signal of the switching device.

[0071] According to the DC bus voltage balance control method for inverters provided in this application embodiment, by injecting common-mode voltage compensation into the initial three-phase modulation wave, a compensated three-phase modulation wave is generated. Based on the compensated three-phase modulation wave, a drive signal for each switching device in the inverter is generated. This enables each switching device in the inverter to change its switching state under the drive of its own drive signal, so that energy is transferred from the DC bus with higher voltage to the DC bus with lower voltage. The difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is adjusted so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This method can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0072] In some embodiments of this application, the driving signal for each switching device is generated based on the compensated three-phase modulated wave, including: generating a pulse width modulation signal corresponding to each switching device based on the compensated three-phase modulated wave, as the driving signal for the switching device.

[0073] In actual operation, the inverter can use pulse width modulation (PWM) as the modulation method, and therefore the drive signal for the switching devices is a PWM signal.

[0074] In some embodiments, the switching state of each switching device in the inverter during each time period of a switching cycle can be determined based on a pulse width modulation method. For each switching device in the inverter, with the goal of controlling the switching device to achieve the aforementioned determined switching state during each time period of a switching cycle, the compensated three-phase modulation wave (Va', Vb', Vc') can be converted into a pulse width modulation signal corresponding to the switching device. The pulse width modulation signal is the driving signal of the switching device, thereby enabling the switching device to achieve the aforementioned determined switching state during each time period of a switching cycle under the drive of the switching device's driving signal.

[0075] In some embodiments, converting the compensated three-phase modulated wave (Va', Vb', Vc') into a pulse width modulation signal corresponding to the switching device may include determining the duty cycle and the pulse width of each time period in a switching cycle based on the switching state of the switching device in each time period of a switching cycle, thereby generating a pulse width modulation signal corresponding to the switching device based on the duty cycle and the pulse width of each time period in a switching cycle.

[0076] According to the DC bus voltage balance control method for inverters provided in this application embodiment, pulse width modulation signals corresponding to each switching device in the inverter are generated based on the compensated three-phase modulation wave, and used as driving signals for the switching devices. This allows the common-mode voltage compensation amount obtained according to actual conditions to be injected into the pulse width modulation signals corresponding to each switching device in the inverter. By controlling the duty cycle and pulse width of the pulse width modulation signals corresponding to each switching device in the inverter, each switching device in the inverter can change its switching state under the drive of its own driving signal, allowing energy to be transferred from the DC bus with higher voltage to the DC bus with lower voltage. This adjusts the difference between the positive and negative DC bus voltages of the inverter, ensuring that the absolute value of the difference is less than or equal to the voltage difference threshold. This method can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and more quickly and effectively restore the balance of the positive and negative DC bus voltages of the inverter.

[0077] In some embodiments of this application, the common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, including: obtaining the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage using a proportional-integral-derivative control algorithm.

[0078] In actual implementation, the control objective can be to reduce the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage to less than or equal to the voltage difference threshold. The proportional-integral-derivative control algorithm is used to calculate and determine the common-mode voltage compensation amount ΔVcm based on the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0079] It should be noted that the above proportional-integral-derivative (PI) control algorithm can be an algorithm that uses at least one of proportional (P) control, integral (I) control, and derivative (D) control. For example, the above PI control algorithm can be a proportional-integral (PI) control algorithm that uses proportional control and integral control, or a PI control algorithm that uses proportional control, integral control, and derivative control, etc.

[0080] In some embodiments, the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter can be passed through two PI controllers (an upper limit loop and a lower limit loop). These two PI controllers can jointly output a common-mode voltage compensation amount ΔVcm. The upper limit loop can be used to limit the difference ΔV between the positive and negative DC bus voltages of the inverter to less than or equal to +Vth, and the lower limit loop can be used to limit the difference ΔV between the positive and negative DC bus voltages of the inverter to greater than or equal to -Vth; Vth is the aforementioned voltage difference threshold.

[0081] According to the DC bus voltage balance control method for inverters provided in the embodiments of this application, the common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter by using a proportional-integral-derivative control algorithm. The algorithm is simpler and easier to implement, and can obtain a more accurate common-mode voltage compensation amount more quickly. Therefore, based on the common-mode voltage compensation amount, the imbalance between the positive and negative DC bus voltages of the inverter can be suppressed more efficiently, and the balance between the positive and negative DC bus voltages of the inverter can be restored more quickly and effectively.

[0082] In some embodiments of this application, after generating the drive signals for each switching device in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave, the method further includes: inputting the drive signal of the switching device to each switching device respectively.

[0083] In actual operation, after generating the drive signal for each switching device in the inverter, the drive signal of each switching device can be input to each switching device in the inverter. This causes each switching device to change its switching state under the drive of its own drive signal, thereby transferring energy from the DC bus with higher voltage to the DC bus with lower voltage. This adjusts the difference ΔV between the positive and negative DC bus voltages of the inverter, ultimately achieving voltage balance between the positive and negative DC buses of the inverter.

[0084] According to the DC bus voltage balance control method for inverters provided in this application embodiment, by inputting a drive signal to each switching device in the inverter, each switching device in the inverter changes its switching state under the drive of its own drive signal, so that energy is transferred from the DC bus with higher voltage to the DC bus with lower voltage. This adjusts the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This method can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and can more quickly and effectively restore the balance of the positive and negative DC bus voltages of the inverter.

[0085] To facilitate understanding of the above embodiments of this application, an implementation process of the DC bus voltage balance control method for an inverter is described below. For example... Figure 2 As shown, the implementation process of a DC bus voltage balance control method for an inverter may include the following steps.

[0086] In some embodiments, after the inverter is powered on but before the grid-connected relay is closed, the following steps can be performed to perform DC bus voltage balance control of the inverter.

[0087] Step 210: Determine whether a startup command has been received.

[0088] Determine whether a start command has been received. In some embodiments, the start command may be input by the user directly operating the input device of the electronic device that serves as the execution subject of the DC bus voltage balance control method for the inverter, or it may be input by the user through other electronic devices to the input device of the electronic device that serves as the execution subject of the DC bus voltage balance control method for the inverter.

[0089] If a startup command is received, step 220 can be executed; if no startup command is received, step 210 can be re-executed.

[0090] Step 220: Enter DC bus voltage balance control mode.

[0091] Upon receiving a start command, the inverter can be started. The inverter is in the start-up phase before grid-connected or off-grid operation. The electronic device, which is the main body for executing the DC bus voltage balance control method of the inverter, enters the DC bus voltage balance control mode to control the inverter to achieve a state of positive and negative DC bus voltage balance before grid-connected or off-grid operation.

[0092] Step 230: Read the sampled values ​​of the positive DC bus voltage and the negative DC bus voltage.

[0093] In some embodiments, the positive DC bus voltage and negative DC bus voltage of the inverter can be obtained through an analog-to-digital converter. The electronic device, which executes the DC bus voltage balance control method of the inverter, can read the sampled values ​​of the positive and negative DC bus voltages output by the analog-to-digital converter, thereby acquiring the positive and negative DC bus voltages of the inverter.

[0094] Step 240: Calculate ΔV and determine whether the absolute value of ΔV is less than the pressure difference threshold Vth.

[0095] Calculate the voltage difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter. The voltage difference ΔV is the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter, ΔV = positive DC bus voltage - negative DC bus voltage.

[0096] After obtaining the difference ΔV between the positive and negative DC bus voltages of the inverter, it can be determined whether the absolute value of the difference ΔV, |ΔV|, is greater than the voltage difference threshold Vth. If yes, step 250 can be executed; otherwise, the inverter is in a state of balanced positive and negative DC bus voltages, and the DC bus voltage balance control mode can be exited or terminated.

[0097] Step 250: Calculate the common-mode voltage compensation amount ΔVcm.

[0098] The common-mode voltage compensation ΔVcm can be calculated based on the difference ΔV between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0099] Step 260: Generate a drive signal to drive the switching device to work.

[0100] Based on the common-mode voltage compensation amount ΔVcm, a drive signal for each switching device in the inverter can be generated and input to each switching device to drive it to work, thereby reducing the absolute value |ΔV| of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0101] For example, for Figure 4The inverter shown can generate drive signals for the corresponding switching devices Q1A, Q2A, Q3A, and Q4A, Q1B, Q2B, Q3B, and Q4B for each of the three phases A, B, and C. This drives the switching devices Q1A, Q2A, Q3A, Q4A, Q1B, Q2B, Q3B, Q4B, Q1B, Q2B, Q3B, and Q4B to operate, thereby reducing the absolute value |ΔV| of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter.

[0102] The DC bus voltage balance control method for inverters provided in this application can be executed by a DC bus voltage balance control device for inverters. This application uses the example of a DC bus voltage balance control device executing the DC bus voltage balance control method for inverters to illustrate the DC bus voltage balance control device provided in this application.

[0103] This application also provides a DC bus voltage balance control device for an inverter. For example... Figure 3 As shown, the DC bus voltage balance control device of the inverter includes: a differential voltage acquisition module 310, a compensation quantity acquisition module 320, and a control module 330.

[0104] The differential voltage acquisition module 310 is used to acquire the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter when a start command is received. The compensation amount acquisition module 320 is used to acquire the common mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold. The control module 330 is used to adjust the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

[0105] According to the DC bus voltage balance control device for inverters provided in the embodiments of this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, a common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, and the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0106] In some embodiments, the control module 330 can be used to generate drive signals for the switching devices in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave; the drive signals are used to adjust the positive DC bus voltage and the negative DC bus voltage.

[0107] In some embodiments, the control module 330 may include: Modulation wave generation unit, used to generate initial three-phase modulation wave; The compensation injection unit is used to inject the common-mode voltage compensation into the initial three-phase modulation wave to generate the compensated three-phase modulation wave. The drive signal generation unit is used to generate a drive signal for each switching device based on the compensated three-phase modulated wave.

[0108] In some embodiments, the drive signal generation unit can be used to generate pulse width modulation signals corresponding to each switching device based on the compensated three-phase modulation wave, as drive signals for the switching devices.

[0109] In some embodiments, the compensation amount acquisition module 320 can be used to acquire the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage using a proportional-integral-derivative control algorithm.

[0110] In some embodiments, the control module 330 may further include: The output unit is used to input the drive signal of the switching device to each switching device respectively.

[0111] The DC bus voltage balance control device of the inverter in this application embodiment can be an electronic device or a component of an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal or other devices besides a terminal. For example, the electronic device can be a mobile phone, tablet computer, laptop computer, handheld computer, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television (TV), ATM or self-service machine, etc. The embodiments of this application do not specifically limit it.

[0112] The DC bus voltage balance control device of the inverter in this embodiment can be a device with an operating system. This operating system can be Microsoft Windows, Android, iOS, or other possible operating systems; this embodiment does not specifically limit it.

[0113] The DC bus voltage balance control device for the inverter provided in this application embodiment can achieve… Figures 1 to 2 The various processes implemented in the method implementation examples will not be described again here to avoid repetition.

[0114] This application also provides an inverter, which may include the DC bus voltage balance control device of the inverter provided in any of the above embodiments of this application.

[0115] This application also provides an inverter system. For example... Figure 4 As shown, the inverter system may include an inverter 410 and a DC bus voltage balance control device 420 for the inverter.

[0116] In actual implementation, the DC bus voltage balance control device 420 of the inverter can be any of the DC bus voltage balance control devices provided in the above embodiments of this application. The DC bus voltage balance control device 420 of the inverter can implement the various processes of the above embodiments of the DC bus voltage balance control method of the inverter and achieve the same technical effect. To avoid repetition, it will not be described again here.

[0117] In some embodiments, the inverter 410 may include a DC-AC conversion module (DC / AC module) 411 and two sets of relays (relay S1 and relay S2), etc.

[0118] In some embodiments, relay S1 may include relays S1A, S1B, and S1C corresponding to phases A, B, and C, respectively.

[0119] In some embodiments, relay S2 may include relays S2A, S2B, and S2C corresponding to phases A, B, and C, respectively.

[0120] In some embodiments, the DC-AC conversion module 411 can be a DC-AC conversion circuit. The DC-AC conversion circuit can include three corresponding DC-AC conversion branches, that is, it can include three DC-AC conversion branches. Each corresponding DC-AC conversion branch can include multiple switching devices. For example, For example, Figure 4Phases A, B, and C each correspond to a DC-AC conversion branch. Each DC-AC conversion branch includes four main switching devices, as well as anti-parallel diodes and clamping diodes, among other devices. Specifically, the DC-AC conversion branch corresponding to phase A includes four switching devices: Q1A, Q2A, Q3A, and Q4A, and their respective anti-parallel diodes, as well as two clamping diodes, D5A and D6A. The DC-AC conversion branch corresponding to phase B includes four switching devices: Q1B, Q2B, Q3B, and Q4B, and their respective anti-parallel diodes, as well as two clamping diodes, D5B and D6B. The DC-AC conversion branch corresponding to phase C includes four switching devices: Q1B, Q2B, Q3B, and Q4B, and their respective anti-parallel diodes, as well as two clamping diodes, D5C and D6C.

[0121] It should be noted that the embodiments of this application do not specifically limit the topology of the inverter 410. For example, Figure 4 The inverter 410 shown is a three-level inverter employing a diode-clamped neutral point clamp (NPC) topology. In this diode-clamped neutral point clamp topology, each main switch in each phase can specifically adopt an I-type or T-type topology, etc., and this embodiment does not specifically limit this. For example, Figure 4 This illustrates a typical topology of a conventional diode-clamped three-level inverter. Figure 4 In the inverter 410 shown, the DC-AC conversion branches corresponding to phases A, B, and C each adopt an I-type topology. Four switching devices are vertically connected in a straight line, resembling the letter "I", and are connected to the midpoint of the DC bus with two clamping diodes.

[0122] In some embodiments, each corresponding DC-AC conversion branch in the DC-AC conversion module 411 may be provided with an inverter inductor. The first end of the inverter inductor may be connected to the corresponding output terminal in the inverter 410, and the second end of the inverter inductor may be connected to the switching device in the DC-AC conversion branch.

[0123] For example, Figure 1 The inverter inductors in the corresponding DC-AC conversion branches A, B, and C are respectively inductance L. A L B and L C .

[0124] In some embodiments, each DC-AC conversion branch is connected to both the positive DC input terminal and the negative DC input terminal of the inverter 410, and the DC-AC conversion branch includes a plurality of switching devices.

[0125] In some embodiments, the positive DC input terminal and the negative DC input terminal of the inverter 410 can be connected to the output terminal of a DC power generation device. The DC power generation device may include at least one of a photovoltaic (PV) module, a DC wind power generation device, and a thermoelectric generator. The specific type of DC power generation device is not limited in the embodiments of this application.

[0126] In some embodiments, reference Figure 4 The DC power generation device can be a photovoltaic module, and the DC positive input terminal and DC negative input terminal of the inverter 410 can be connected to the positive output terminal (PV+) and negative output terminal (PV-) of the photovoltaic module, respectively.

[0127] According to the inverter system provided in the embodiments of this application, when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter is greater than the voltage difference threshold, a common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage, and the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold. This can more efficiently suppress the imbalance of the positive and negative DC bus voltages of the inverter and restore the balance of the positive and negative DC bus voltages of the inverter more quickly and effectively.

[0128] In some embodiments, such as Figure 5 As shown, this application embodiment also provides an inverter 500, including a processor 501, a memory 502, and a computer program stored in the memory 502 and executable on the processor 501. When the computer program is executed by the processor 501, it implements the various processes of the DC bus voltage balance control method embodiment of the inverter described above, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0129] It should be noted that the inverter in this application embodiment includes the mobile electronic device and non-mobile electronic device described above.

[0130] This application also provides a non-volatile computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described inverter DC bus voltage balance control method embodiment and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0131] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0132] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the DC bus voltage balance control method of the inverter described above.

[0133] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0134] This application embodiment also provides a chip, which includes a processor and a communication interface. The communication interface is coupled to the processor. The processor is used to run programs or instructions to implement the various processes of the above-described DC bus voltage balance control method embodiment for inverters, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0135] It should be understood that the chip mentioned in the embodiments of this application may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0136] It should be noted that, in this document, 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 a process, method, article, or apparatus. Without further limitations, 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. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0137] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the related technology, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0138] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0139] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0140] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for DC bus voltage balance control of an inverter, characterized in that, include: Obtain the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter; When the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold, the common-mode voltage compensation amount is obtained based on the difference between the positive DC bus voltage and the negative DC bus voltage. Based on the common-mode voltage compensation amount, the difference between the positive DC bus voltage and the negative DC bus voltage is adjusted so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

2. The DC bus voltage balance control method for an inverter according to claim 1, characterized in that, The adjustment of the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount includes: Based on the common-mode voltage compensation and the three-phase modulation wave, drive signals for the switching devices in the inverter are generated; the drive signals are used to adjust the positive DC bus voltage and the negative DC bus voltage.

3. The DC bus voltage balance control method for an inverter according to claim 2, characterized in that, The step of generating drive signals for the switching devices in the inverter based on the common-mode voltage compensation and the three-phase modulation wave includes: Generate the initial three-phase modulated wave; The common-mode voltage compensation is injected into the initial three-phase modulation wave to generate a compensated three-phase modulation wave; Based on the compensated three-phase modulated wave, the drive signal for each of the switching devices is generated.

4. The DC bus voltage balance control method for an inverter according to claim 3, characterized in that, The process of generating the drive signal for each of the switching devices based on the compensated three-phase modulated wave includes: Based on the compensated three-phase modulated wave, a pulse width modulation signal corresponding to each of the switching devices is generated as the driving signal of the switching device.

5. The DC bus voltage balance control method for an inverter according to any one of claims 1 to 4, characterized in that, The step of obtaining the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage includes: Based on the proportional-integral-derivative (PID) control algorithm, the common-mode voltage compensation amount is obtained according to the difference between the positive DC bus voltage and the negative DC bus voltage.

6. The DC bus voltage balance control method for an inverter according to claim 2, characterized in that, After generating the drive signals for each switching device in the inverter based on the common-mode voltage compensation amount and the three-phase modulation wave, the method further includes: The drive signal of each of the switching devices is input to each of the switching devices respectively.

7. A DC bus voltage balance control device for an inverter, characterized in that, The differential voltage acquisition module is used to acquire the difference between the positive DC bus voltage and the negative DC bus voltage of the inverter upon receiving a start command. The compensation amount acquisition module is used to acquire the common-mode voltage compensation amount based on the difference between the positive DC bus voltage and the negative DC bus voltage when the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is greater than the voltage difference threshold. The control module is used to adjust the difference between the positive DC bus voltage and the negative DC bus voltage based on the common-mode voltage compensation amount, so that the absolute value of the difference between the positive DC bus voltage and the negative DC bus voltage is less than or equal to the voltage difference threshold.

8. An inverter system, characterized in that, Includes an inverter and a DC bus voltage balance control device for the inverter as described in claim 7.

9. An inverter, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the DC bus voltage balance control method for the inverter as described in any one of claims 1 to 6.

10. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the DC bus voltage balance control method for the inverter as described in any one of claims 1 to 6.

11. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the DC bus voltage balance control method for the inverter as described in any one of claims 1 to 6.

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