Off-grid inverter voltage-sharing current-limiting control method and system under unbalanced load

Abstract

The invention provides an off-grid inverter voltage-sharing current-limiting control method and system under unbalanced load. The method comprises the following steps: determining a negative sequence q-axis initial given value, a negative sequence d-axis initial given value and the like of a three-phase three-wire system off-grid inverter; when the alternating current side load unbalance degree is larger than or equal to the first threshold value and smaller than or equal to the second threshold value, the positive sequence d-axis real given value of the current loop is determined according to the comparison result of the positive sequence d-axis initial given value and the positive sequence voltage d-axis amplitude limiting value; determining a positive sequence q-axis real given value of the current loop by using a comparison result of the positive sequence q-axis initial given value and the positive sequence voltage q-axis amplitude limiting value; determining a negative sequence d-axis real given value of the current loop according to a comparison result of the negative sequence d-axis initial given value and the negative sequence voltage d-axis amplitude limiting value; and determining a negative sequence q-axis real given value by using a comparison result of the negative sequence q-axis initial given value and the negative sequence voltage q-axis amplitude limiting value, thereby realizing current-limiting and voltage-limiting control of the three-phase three-wire system off-grid inverter.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy power generation, and specifically, to a method and system for voltage equalization and current limiting control of an off-grid inverter under unbalanced loads. Background Art

[0002] In recent years, renewable energy power generation has become an important technical route for China's energy transformation. As a hub between the renewable energy side and the grid side or load side, the inverter shoulders the important responsibilities of power quality and system safe operation. Therefore, the inverter has always been a research hotspot. As an important device for new energy power generation, when operating in the off-grid mode, a three-phase three-wire inverter is generally connected to the load through a power frequency transformer. In the off-grid mode, the phenomena of unbalanced three-phase loads and even single-phase load overload are extremely common.

[0003] When unbalanced three-phase loads or single-phase overload occur, it will cause asymmetric magnetic fluxes in the transformer; and the asymmetric magnetic fluxes will introduce asymmetric three-phase reflected voltages on the primary side of the transformer, resulting in voltage imbalance on the primary side voltage of the transformer, and further causing the inverter to protect and shut down or even equipment damage.

[0004] Currently, most manufacturers of three-phase three-wire off-grid inverters often adopt the method of only controlling the positive sequence for unbalanced three-phase loads in the off-grid mode, resulting in serious unevenness of the line voltage or phase voltage on the AC side of the inverter, reducing the off-grid power supply quality. Especially when a single-phase load overload condition occurs, it is extremely easy to cause the inverter to protect and shut down or even damage.

[0005] In order to solve the above existing problems, people have been seeking an ideal technical solution. Summary of the Invention

[0006] Based on this, in view of the above technical problems, it is necessary to provide a method and system for voltage equalization and current limiting control of an off-grid inverter under unbalanced loads, so that the difference in the three-phase voltages output on the AC side of a three-phase three-wire off-grid inverter can maintain a small range of fluctuations in the off-grid mode and under unbalanced three-phase load conditions, thereby achieving precise control of voltage equalization;

[0007] By calculating the peak value of the single-phase load voltage, precise control of current limiting output under the single-phase load overload condition can also be achieved, so that the three-phase three-wire off-grid inverter can greatly reduce the voltage imbalance degree of the output voltage on the AC side under unbalanced load conditions and ensure the safe operation of the inverter.

[0008] To achieve the above object, the first aspect of the present invention provides a method for voltage equalization and current limiting control of an off-grid inverter under unbalanced loads, the method comprising:

[0009] Determine the AC-side load unbalance degree e of the three-phase three-wire off-grid inverter; according to the AC-side load unbalance degree e, set two thresholds, namely the first threshold e 1 = 2% and the second threshold e 2 = 100%; the calculation formula for the unbalance degree e is:

[0010]

[0011] where, I max is the maximum value of the AC-side load current, and I min is the minimum value of the AC-side load current;

[0012] Generate the initial negative-sequence q-axis given value of the current loop based on the true value of the negative-sequence voltage q-axis sampling Generate the initial negative-sequence d-axis given value of the current loop based on the true value of the negative-sequence voltage d-axis sampling

[0013] Generate the initial positive-sequence q-axis given value of the current loop based on the true value of the positive-sequence voltage q-axis sampling Generate the initial positive-sequence d-axis given value of the current loop based on the true value of the positive-sequence voltage d-axis sampling

[0014] Determine the limit value of the negative-sequence voltage q-axis and the limit value of the negative-sequence voltage d-axis Determine the limit value of the positive-sequence voltage q-axis and the limit value of the positive-sequence voltage d-axis

[0015] When the first threshold ≤ the AC-side load unbalance degree e ≤ the second threshold, the three-phase three-wire off-grid inverter executes the current-limiting and voltage-limiting control strategy:

[0016] ① Judge whether the initial positive-sequence d-axis given value is greater than or equal to the limit value of the positive-sequence voltage d-axis If so, determine the true positive-sequence d-axis given value of the current loop based on the limit value of the positive-sequence voltage d-axis If not, determine the true positive-sequence d-axis given value of the current loop based on the initial positive-sequence d-axis given value

[0017] ② Judge whether the initial positive-sequence q-axis given value is greater than or equal to the limit value of the positive-sequence voltage q-axis If so, determine the true positive-sequence q-axis given value of the current loop based on the limit value of the positive-sequence voltage q-axis ​​​​​​Determine the true positive-sequence q-axis given value of the current loop If not, then based on the positive-sequence q-axis initial given value Determine the true positive-sequence q-axis given value of the current loop

[0018] ③ Judge the negative-sequence d-axis initial given value Whether it is greater than or equal to the negative-sequence voltage d-axis limit value If so, then based on the negative-sequence voltage d-axis limit value Determine the true negative-sequence d-axis given value of the current loop If not, then based on the negative-sequence d-axis initial given value Determine the true negative-sequence d-axis given value of the current loop

[0019] ④ Judge the negative-sequence q-axis initial given value Whether it is greater than or equal to the negative-sequence voltage q-axis limit value If so, then based on the negative-sequence voltage q-axis limit value Determine the true negative-sequence q-axis given value of the current loop If not, then based on the positive-sequence q-axis initial given value Determine the true negative-sequence q-axis given value of the current loop

[0020] The three-phase three-wire off-grid inverter is based on the true positive-sequence d-axis given value of the current loop The true negative-sequence d-axis given value The true positive-sequence q-axis given value And the true negative-sequence q-axis given value Carry out voltage equalization and current limiting control.

[0021] Based on the above, set the third threshold e 3 = 30%;

[0022] When the third threshold ≤ the AC side load unbalance degree e ≤ the second threshold, the double closed-loop control loop of the three-phase three-wire off-grid inverter performs voltage limiting and equalization output according to the following formula:

[0023]

[0024] Among them, α P Represents the peak value of the output voltage of the voltage limiting and equalization of the three-phase three-wire off-grid inverter, Represents the peak value of the rated AC side output phase voltage effective value of the three-phase three-wire off-grid inverter, and Δv represents the voltage drop on the internal inductor line of the three-phase three-wire off-grid inverter.

[0025] Based on the above, the generated negative-sequence q-axis initial given value of the current loop Initial negative sequence d-axis given value Initial positive sequence q-axis given value and initial positive sequence d-axis given value Determine the true positive and negative sequence dq-axis given values of the current loop in the way of eliminating negative sequence, limiting positive sequence, protecting reactive power and limiting active power:

[0026] (1) First calculate the negative sequence dq-axis limit values, and then calculate the positive sequence dq-axis limit values; when calculating the positive sequence dq-axis limit values, use the positive sequence reactive power limit to the maximum value to calculate the upper and lower limits of the positive sequence d-axis and q-axis;

[0027] (2) Then perform the following logical judgment:

[0028] Determine the true positive sequence dq-axis given value of the current loop through the comparison result between the initial positive sequence dq-axis given value and the positive sequence voltage dq-axis limit value: if the initial positive sequence dq-axis given value ≥ the positive sequence voltage dq-axis limit value, then the true positive sequence dq-axis given value of the current loop = the positive sequence voltage dq-axis limit value; if the initial positive sequence dq-axis given value < the positive sequence voltage dq-axis limit value, then the true positive sequence dq-axis given value of the current loop = the initial positive sequence dq-axis given value;

[0029] Determine the true negative sequence dq-axis given value of the current loop through the comparison result between the initial negative sequence dq-axis given value and the negative sequence voltage dq-axis limit value: if the initial negative sequence dq-axis given value ≥ the negative sequence voltage dq-axis limit value, then the true negative sequence dq-axis given value of the current loop = the negative sequence voltage dq-axis limit value; if the initial negative sequence dq-axis given value < the negative sequence voltage dq-axis limit value, then the true negative sequence dq-axis given value of the current loop = the initial negative sequence dq-axis given value.

[0030] Based on the above, when calculating the negative sequence dq-axis limit value, first calculate the negative sequence voltage q-axis limit value

[0031] Based on the above, determine the negative sequence voltage q-axis limit value and negative sequence voltage d-axis limit value When performing:

[0032] Use the following formula to generate the negative sequence voltage q-axis limit value

[0033]

[0034] Use the following formula to generate the negative sequence voltage d-axis limit value

[0035]

[0036] Among them, represents the peak value of the effective value of the AC-side output phase current of the three-phase three-wire off-grid inverter, represents the true value of the q-axis sampling of the negative-sequence current of the three-phase three-wire off-grid inverter, and abs represents the absolute value calculation.

[0037] Based on the above, determine the q-axis limit amplitude of the positive-sequence voltage and the d-axis limit amplitude of the positive-sequence voltage When performing:

[0038] Generate the q-axis limit amplitude of the positive-sequence voltage using the following formula

[0039]

[0040] Generate the d-axis limit amplitude of the positive-sequence voltage using the following formula

[0041]

[0042] Among them, represents the total amplitude limit value of the positive sequence, represents the peak value of the effective value of the AC-side output phase current of the three-phase three-wire off-grid inverter, represents the true value of the d-axis sampling of the negative-sequence current of the three-phase three-wire off-grid inverter, represents the true value of the q-axis sampling of the negative-sequence current of the three-phase three-wire off-grid inverter, and abs represents the absolute value calculation.

[0043] To achieve the above object, the second aspect of the present invention provides a voltage equalization and current limiting control system for an off-grid inverter under unbalanced loads, which includes an abc-αβ0 coordinate system transformation module, a positive and negative sequence separation transformation module, an αβ-dq coordinate system transformation module, an unbalanced load voltage equalization and current limiting control module, a current loop control module, a dq-αβ coordinate system transformation module under positive and negative sequences, and an SVPWM drive calculation module; among them,

[0044] The abc-αβ0 coordinate system transformation module is used to perform Clark transformation on the AC-side output voltage signal and the load current signal of the three-phase three-wire off-grid inverter by using a pre-configured abc-αβ0 coordinate system transformation matrix;

[0045] The positive and negative sequence separation transformation module is used to perform positive and negative sequence separation on the AC-side output voltage signal and the load current signal after Clark transformation;

[0046] The αβ-dq coordinate system transformation module is used to perform Park transformation on the AC-side output voltage signal and the load current signal after positive and negative sequence separation by using the pre-configured αβ-dq transformation matrix in the positive and negative sequence coordinate systems, so as to obtain the variables in the positive and negative sequence dq axes; wherein, the variables in the positive and negative sequence dq axes include the true sampling value of the negative sequence voltage on the q axis The true sampling value of the negative sequence voltage on the d axis The true sampling value of the negative sequence current on the q axis The true sampling value of the negative sequence current on the d axis The true sampling value of the positive sequence voltage on the q axis And the true sampling value of the positive sequence voltage on the d axis

[0047] The unbalanced load voltage equalization and current limiting control module is used to execute the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load according to any one of claims 1 to 4;

[0048] The current loop control module is used to generate the true positive sequence d-axis given value The true negative sequence d-axis given value The true positive sequence q-axis given value And the true negative sequence q-axis given value to generate voltage modulation signals in the positive and negative sequence dq coordinate systems, and use the voltage modulation signals as the current loop output modulation signals;

[0049] The dq-αβ coordinate system transformation module under positive and negative sequences is used to perform inverse Park transformation on the current loop output modulation signals under positive and negative sequences;

[0050] The SVPWM drive calculation module is used to generate corresponding PWM drive signals based on the current loop output modulation signals after inverse Park transformation.

[0051] To achieve the above object, the third aspect of the present invention provides a voltage equalization and current limiting control device for an off-grid inverter under unbalanced load, which includes a processor, a communication interface, a memory, and a communication bus. Among them, the processor, the communication interface, and the memory complete mutual communication through the communication bus;

[0052] The memory is used to store computer programs;

[0053] The processor is used to implement the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load as described above when executing the program stored on the memory.

[0054] To achieve the above object, a fourth aspect of the present invention provides a readable storage medium, on which instructions are stored, and when executed by one or more processors, cause the processors to execute the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load as described above.

[0055] To achieve the above object, a fifth aspect of the present invention provides a computer program product, including a computer program / instructions, characterized in that when the computer program / instructions are executed by a processor, the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load as described is implemented.

[0056] The beneficial effects of the present invention are as follows:

[0057] Based on the true values of the positive and negative sequence voltage dq-axis sampling, the initial given values of the positive and negative sequence voltage dq-axis are determined. The timing of the voltage equalization and current limiting control is judged through the unbalance degree of the AC side load. The true given value of the positive sequence d-axis of the current loop is determined through the comparison result between the initial given value of the positive sequence d-axis and the limit value of the positive sequence voltage d-axis; the true given value of the positive sequence q-axis of the current loop is determined by using the comparison result between the initial given value of the positive sequence q-axis and the limit value of the positive sequence voltage q-axis; the true given value of the negative sequence d-axis of the current loop is determined through the comparison result between the initial given value of the negative sequence d-axis and the limit value of the negative sequence voltage d-axis; the true given value of the negative sequence q-axis is determined by using the comparison result between the initial given value of the negative sequence q-axis and the limit value of the negative sequence voltage q-axis, so as to quickly and accurately realize the current limiting and voltage limiting control of the three-phase three-wire off-grid inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a schematic flow chart of the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load of the present invention.

[0059] Figure 2 is a schematic diagram of the current limiting and voltage limiting control strategy of the present invention.

[0060] Figure 3 is a control block diagram of the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load of the present invention.

[0061] Figure 4 is a Bode diagram of the transfer function of the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load of the present invention.

[0062] Figure 5 is a schematic diagram of the positive and negative sequence rotating coordinate systems of the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load of the present invention.

[0063] Figure 6 is a schematic diagram of the simulation uvw three-phase AC voltage waveform of the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load of the present invention Figure 1(Under the conditions of an inverter with a rated power of 50 kW, 10 kW on phase A, 10 kW on phase B, and 13 kW on phase C).

[0064] Figure 7 It is a schematic diagram of the uvw three-phase AC voltage waveform of the simulation of the equal voltage and current limiting control method of the off-grid inverter of the present invention under unbalanced loads. Figure 2 (Under the conditions of an inverter with a rated power of 50 kW, 0 kW on phase A, 0 kW on phase B, 20 kW on phase C, and single-phase overload conditions). Specific embodiments

[0065] The technical solutions of the present invention will be further described in detail through specific embodiments below.

[0066] For easy understanding, first, the interaction parties and / or terms and / or custom words involved in the present invention will be described in combination with the technical solutions of the present invention:

[0067] Current Loop: The main purpose of the current loop is to precisely control the output current of the device to achieve fast and precise regulation of the load current; the current loop is usually the inner loop, with a fast response speed and can quickly respond to load changes; the positive and negative sequence coordinate system current loop control module proposed in the present invention obtains the true positive sequence d-axis given value after equal voltage and current limiting control of unbalanced loads True positive sequence d-axis given value True positive sequence q-axis given value And the true positive sequence q-axis given value And the AC side voltage after positive and negative sequence separation is subjected to PI control (proportional-integral control) to generate voltage modulation signals in the positive and negative sequence dq coordinate systems.

[0068] Voltage Loop: The voltage loop is usually the outer loop of the current loop, used to control the output voltage to ensure the stability and accuracy of the output voltage; the voltage loop has a slower response speed and is mainly used to adjust and stabilize the long-term voltage level; the positive and negative sequence coordinate system voltage loop control module proposed in the present invention outputs the initial positive sequence d-axis given value through PI control (proportional-integral control) of the AC side voltage and load current after positive and negative sequence separation Initial positive sequence q-axis given value Initial negative sequence d-axis given value And the initial negative sequence q-axis given value

[0069] The double closed-loop control of the inverter is a power conversion technology that jointly ensures the power quality of the inverter output through two control loops - the current inner loop and the voltage outer loop. This double closed-loop design not only improves the stability of the inverter but also effectively copes with external interferences such as grid fluctuations.

[0070] The load unbalance degree of the AC side of a three - phase three - wire off - grid inverter: The ratio of the difference between the maximum and minimum values of the three - phase current values on the AC side to the maximum value.

[0071] The first, second, and third thresholds: The pre - set unbalance degree thresholds, where the first, second, and third thresholds are e 1 = 2%, e 2 = 100%, and e 3 = 30%;

[0072] It should be noted that the voltage equalization and current limiting method proposed in the present invention mainly aims at the control strategy when the unbalance degree of the inverter AC side is relatively large (i.e., unbalance degree value > 2%).

[0073] It should be noted that if the load unbalance degree of the AC side of a three - phase three - wire inverter is relatively high (i.e., 2% ≤ unbalance degree value ≤ 100%), the negative - sequence content is relatively high at this stage. And in this stage, the inverter voltage control loop will enter the unbalanced load voltage equalization and current limiting control module, and the unbalanced load voltage equalization and current limiting control module will control the output of the inverter voltage loop in the way of eliminating negative - sequence, limiting positive - sequence, maintaining reactive power, and limiting active power to ensure the voltage balance degree of the inverter AC side;

[0074] If the load unbalance degree of the AC side of a three - phase three - wire inverter is very high (i.e., 30% ≤ unbalance degree value ≤ 100%), resulting in a single - phase overload situation, on the basis of controlling the output of the inverter voltage loop in the way of eliminating negative - sequence, limiting positive - sequence, maintaining reactive power, and limiting active power, the current - voltage double - closed - loop circuit also performs output voltage peak limiting to ensure the voltage balance degree of the inverter AC side.

[0075] Eliminating negative - sequence: Refers to eliminating the negative - sequence voltage or current components in the system.

[0076] Limiting positive - sequence: Refers to limiting the amplitude of the positive - sequence voltage or current in the system.

[0077] Maintaining reactive power: Refers to maintaining the stability of the reactive power in the system.

[0078] Limiting active power: Refers to limiting the output of the active power in the system to ensure that the system does not operate over - load.

[0079] Embodiment 1

[0080] This embodiment gives a specific implementation manner of the voltage equalization and current limiting control method of an off - grid inverter under unbalanced load, as Figure 1 shown, the voltage equalization and current limiting control method of the off - grid inverter under unbalanced load includes:

[0081] Determine the load unbalance degree e of the AC side of the three - phase three - wire off - grid inverter; According to the load unbalance degree e of the AC side, set two thresholds, namely the first threshold e1 = 2% and the second threshold e 2 = 100%; The calculation formula for the unbalance degree e is:

[0082]

[0083] where, I max is the maximum value of the AC - side load current, I min is the minimum value of the AC - side load current;

[0084] Generate the initial negative - sequence q - axis given value of the current loop based on the true value of the negative - sequence voltage q - axis sampling Generate the initial negative - sequence d - axis given value of the current loop based on the true value of the negative - sequence voltage d - axis sampling Generate the initial positive - sequence q - axis given value of the current loop based on the true value of the positive - sequence voltage q - axis sampling Generate the initial positive - sequence d - axis given value of the current loop based on the true value of the positive - sequence voltage d - axis sampling

[0085] Determine the limit value of the negative - sequence voltage q - axis and the limit value of the negative - sequence voltage d - axis

[0086] Generate the initial positive - sequence q - axis given value of the current loop based on the true value of the positive - sequence voltage q - axis sampling Generate the initial positive - sequence d - axis given value of the current loop based on the true value of the positive - sequence voltage d - axis sampling Generate the initial positive - sequence q - axis given value of the current loop based on the true value of the positive - sequence voltage q - axis sampling Generate the initial positive - sequence d - axis given value of the current loop based on the true value of the positive - sequence voltage d - axis sampling

[0087] Determine the limit value of the positive - sequence voltage q - axis and the limit value of the positive - sequence voltage d - axis

[0088] When the first threshold ≤ the AC - side load unbalance degree ≤ the second threshold, that is, e 1 ≤ e ≤ e 2 the three - phase three - wire off - grid inverter executes the current - limiting and voltage - limiting control strategy:

[0089] Judge whether the initial positive - sequence d - axis given value is greater than or equal to the limit value of the positive - sequence voltage d - axis If so, determine the true positive - sequence d - axis given value of the current loop based on the limit value of the positive - sequence voltage d - axis If not, determine the true positive - sequence d - axis given value of the current loop based on the initial positive - sequence d - axis given value If not, determine the true positive - sequence d - axis given value of the current loop based on the initial positive - sequence d - axis given value Determine the true positive - sequence d - axis given value of the current loop based on the initial positive - sequence d - axis given value

[0090] Judge whether the initial positive - sequence q - axis given value is greater than or equal to the limit value of the positive - sequence voltage q - axis If so, determine the true positive - sequence q - axis given value of the current loop based on the limit value of the positive - sequence voltage q - axis Determine the true positive-sequence q-axis given value of the current loop If not, then based on the positive-sequence q-axis initial given value Determine the true positive-sequence q-axis given value of the current loop ;

[0091] Judge whether the negative-sequence d-axis initial given value is greater than or equal to the negative-sequence voltage d-axis limit value If so, then based on the negative-sequence voltage d-axis limit value Determine the true negative-sequence d-axis given value of the current loop If not, then based on the negative-sequence d-axis initial given value Determine the true negative-sequence d-axis given value of the current loop

[0092] Judge whether the negative-sequence q-axis initial given value is greater than or equal to the negative-sequence voltage q-axis limit value If so, then based on the negative-sequence voltage q-axis limit value Determine the true negative-sequence q-axis given value of the current loop If not, then based on the positive-sequence q-axis initial given value Determine the true negative-sequence q-axis given value of the current loop

[0093] The three-phase three-wire off-grid inverter is based on the true positive-sequence d-axis given value of the current loop True positive-sequence d-axis given value True positive-sequence q-axis given value And the true positive-sequence q-axis given value Carry out equal-voltage and current-limiting control

[0094] The core of the current-limiting and voltage-limiting control strategy in this embodiment is to set upper and lower limit values for the given value of the current loop, and instead of using the current inner-loop value calculated by the voltage loop, use the limit value to generate a new current inner-loop given value; when the inverter works in a normal state (three-phase balanced and overload-free condition), the current inner-loop reference value generated by the voltage loop will not trigger the execution of the current-limiting and voltage-limiting control strategy, and when the inverter is three-phase unbalanced or three-phase unbalanced and overloaded, the current-limiting and voltage-limiting control strategy will be triggered to execute

[0095] The method in this embodiment has a small amount of calculation, and the system can quickly realize carrying balanced loads and unbalanced loads. The simulation effect when the unbalance degree of the load on the AC side of the three-phase three-wire inverter is relatively high (i.e., 2% ≤ e ≤ 100%) is as Figure 6 shown

[0096] Embodiment 2

[0097] The difference between this embodiment and Embodiment 1 is that:

[0098] When the first threshold ≤ the unbalance degree of the AC side load ≤ the second threshold, the initial given value of the negative sequence q-axis of the generated current loop Initial given value of the negative sequence d-axis Initial given value of the positive sequence q-axis and the initial given value of the positive sequence d-axis Cannot be directly given to the current loop. The true given values of the positive and negative sequence dq-axes of the current loop should be determined in the way of eliminating negative sequence, limiting positive sequence, protecting reactive power and limiting active power.

[0099] Preferably, set upper and lower limits for the true given values of the current loop in the order of eliminating negative sequence, limiting positive sequence, protecting reactive power and limiting active power, which not only ensures the specification of positive and negative sequence components and the stable output power of the system, but also reduces the system burden.

[0100] The specific determination process of the true given values of the positive and negative sequence dq-axes of the current loop is as follows:

[0101] (1) To meet the principle of eliminating negative sequence, first calculate the limit values of the negative sequence dq-axes (limit value of the negative sequence voltage q-axis Limit value of the negative sequence voltage d-axis ) to meet the negative sequence requirements, and then calculate the limit values of the positive sequence dq-axes (limit value of the positive sequence voltage q-axis Limit value of the positive sequence voltage d-axis ). To protect reactive power, when calculating the limit values of the negative sequence dq-axes, first calculate the limit value of the negative sequence voltage q-axis

[0102] When calculating the limit values of the positive sequence dq-axes, according to the principles of protecting reactive power and limiting active power, use the positive sequence reactive power limit to give the maximum value to calculate the upper and lower limits of the positive sequence d-axis and q-axis.

[0103] In this way, four limit values are constructed, which are respectively:

[0104] Limit value of the negative sequence voltage q-axis Limit value of the negative sequence voltage d-axis Limit value of the positive sequence voltage q-axis Limit value of the positive sequence voltage d-axis

[0105] (2) Then perform the following logical judgment:

[0106] Determine the true given value of the positive sequence d-axis of the current loop through the comparison result between the initial given value of the positive sequence d-axis and the limit value of the positive sequence voltage d-axis: If the initial given value of the positive sequence d-axis ≥ the limit value of the positive sequence voltage d-axis Then the true given value of the positive sequence d-axis of the current loop If the initial given value of the positive sequence d-axis < the limit value of the positive sequence voltage d-axis Then the true positive-sequence d-axis given value of the current loop

[0107] Using the comparison result between the initial positive-sequence q-axis given value and the positive-sequence voltage q-axis limit value, determine the true positive-sequence q-axis given value of the current loop: If the initial positive-sequence q-axis given value ≥ the positive-sequence voltage q-axis limit value Then the true positive-sequence q-axis given value of the current loop If the initial positive-sequence q-axis given value < the positive-sequence voltage q-axis limit value Then the true positive-sequence q-axis given value of the current loop

[0108] Through the comparison result between the initial negative-sequence d-axis given value and the negative-sequence voltage d-axis limit value, determine the true negative-sequence d-axis given value of the current loop: If the initial negative-sequence d-axis given value ≥ the negative-sequence voltage d-axis limit value Then the true negative-sequence d-axis given value of the current loop If the initial negative-sequence d-axis given value < the negative-sequence voltage d-axis limit value Then the true negative-sequence d-axis given value of the current loop

[0109] Using the comparison result between the initial negative-sequence q-axis given value and the negative-sequence voltage q-axis limit value, determine the true negative-sequence q-axis given value: The initial negative-sequence q-axis given value ≥ the negative-sequence voltage q-axis limit value Then the true negative-sequence q-axis given value of the current loop The initial negative-sequence q-axis given value < the negative-sequence voltage q-axis limit value Then the true negative-sequence q-axis given value of the current loop

[0110] Embodiment 3

[0111] Based on the above embodiments, this embodiment provides a specific implementation manner of another voltage equalization and current limiting control method for an off-grid inverter under unbalanced loads;

[0112] Determine the negative-sequence voltage q-axis limit value and the negative-sequence voltage d-axis limit value When performing:

[0113] Use the following formula to generate the negative-sequence voltage q-axis limit value

[0114]

[0115] The negative - sequence voltage d - axis limit amplitude is generated using the following formula

[0116]

[0117] where represents the peak value of the effective value of the AC - side output phase current of the three - phase three - wire off - grid inverter, represents the true sampled value of the q - axis of the negative - sequence current of the three - phase three - wire off - grid inverter, and abs represents the absolute - value calculation.

[0118] Determine the positive - sequence voltage q - axis limit amplitude and the positive - sequence voltage d - axis limit amplitude When doing so, execute:

[0119] The positive - sequence voltage q - axis limit amplitude is generated using the following formula

[0120]

[0121] The positive - sequence voltage d - axis limit amplitude is generated using the following formula

[0122]

[0123] where represents the total positive - sequence amplitude limit value, represents the peak value of the effective value of the AC - side output phase current of the three - phase three - wire off - grid inverter, represents the true sampled value of the d - axis of the negative - sequence current of the three - phase three - wire off - grid inverter, represents the true sampled value of the q - axis of the negative - sequence current of the three - phase three - wire off - grid inverter, and abs represents the absolute - value calculation.

[0124] Embodiment 4

[0125] Based on the above - mentioned embodiment, when the load unbalance degree on the AC side of the three - phase three - wire inverter is very high (i.e., 30% ≤ unbalance degree value ≤ 100%) and a single - phase overload occurs, this embodiment gives a further solution to the voltage - equalizing and current - limiting control method of the off - grid inverter under unbalanced loads.

[0126] When the third threshold ≤ the AC - side load unbalance degree ≤ the second threshold, 30% ≤ e ≤ 100%, the double - closed - loop control loop of the three - phase three - wire off - grid inverter performs voltage - limiting and equalizing output according to the following formula

[0127]

[0128] where α Prepresents the peak value of the effective value of the output voltage of the three-phase three-wire off-grid inverter for voltage limiting and balancing, represents the peak value of the effective value of the rated AC-side output phase voltage of the three-phase three-wire off-grid inverter, and Δv represents the voltage drop on the inductor line inside the three-phase three-wire off-grid inverter.

[0129] Under the condition of single-phase overload, the simulation effect is as Figure 7 shown, still ensuring the balance of the AC-side voltage, greatly broadening the adaptability of the off-grid inverter to the load and the off-grid application scenarios.

[0130] Embodiment 5

[0131] Based on the above embodiments, this embodiment gives a specific implementation manner of the voltage equalization and current limiting control system of an off-grid inverter under unbalanced loads, as shown in the attached Figure 2 and 3 shown;

[0132] In some embodiments, the voltage equalization and current limiting control system of the off-grid inverter under unbalanced loads includes an abc-αβ0 coordinate system transformation module, a positive and negative sequence separation transformation module, an αβ-dq coordinate system transformation module, an unbalanced load voltage equalization and current limiting control module, a current loop control module, a dq-αβ coordinate system transformation module under positive and negative sequences, and an SVPWM drive calculation module; among them,

[0133] The abc-αβ0 coordinate system transformation module is used to perform Clark transformation on the AC-side output voltage signal and the load current signal of the three-phase three-wire off-grid inverter by using a pre-configured abc-αβ0 coordinate system transformation matrix;

[0134] The positive and negative sequence separation transformation module is used to perform positive and negative sequence separation on the AC-side output voltage signal and the load current signal after Clark transformation;

[0135] The αβ-dq coordinate system transformation module is used to perform Park transformation on the AC-side output voltage signal and the load current signal after positive and negative sequence separation by using a pre-configured αβ-dq transformation matrix under positive and negative sequence coordinate systems to obtain variables under positive and negative sequence dq axes; among them, the variables under positive and negative sequence dq axes include the true sampled value of the negative sequence voltage q-axis the true sampled value of the negative sequence voltage d-axis the true sampled value of the negative sequence current q-axis the true sampled value of the negative sequence current d-axis the true sampled value of the positive sequence voltage q-axis and the true sampled value of the positive sequence voltage d-axis

[0136] The unbalanced load voltage equalization and current limiting control module is used to execute the voltage equalization and current limiting control method of the off-grid inverter under unbalanced load according to any one of Embodiments 1-3;

[0137] The current loop control module is used to generate a positive-sequence d-axis true given value based on the unbalanced load voltage equalization and current limiting control module Positive-sequence d-axis true given value Positive-sequence q-axis true given value And the positive-sequence q-axis true given value Generate voltage modulation signals in the positive and negative sequence dq coordinate systems, and use the voltage modulation signals as the current loop output modulation signals;

[0138] The positive and negative sequence dq-αβ coordinate system transformation module is used to perform an inverse Park transformation on the current loop output modulation signals in the positive and negative sequences;

[0139] The SVPWM drive calculation module is used to generate corresponding PWM drive signals based on the current loop output modulation signals after the inverse Park transformation.

[0140] In some embodiments, the voltage equalization and current limiting control system of the off-grid inverter under unbalanced load further includes an αβ integration module in the positive and negative sequence coordinate systems, which is used to integrate and limit the positive and negative sequence αβ integrated modulation signals output by the current loop after the inverse Park transformation.

[0141] It should be noted that the control object of the voltage equalization and current limiting control system of the off-grid inverter under unbalanced load is the inverter, and the input signals include the three-phase voltage output on the AC side, the three-phase inductor current, and the three-phase load current.

[0142] It can be understood that performing a Clark transformation on the AC side output voltage signal and the load current signal of a three-phase three-wire off-grid inverter is to transform the three-phase three-wire voltage, inductor current, and load current from the abc coordinate system to the αβ coordinate system. The specific steps are prior art and will not be elaborated here;

[0143] In some embodiments, the pre-configured abc-αβ0 coordinate system transformation matrix is:

[0144]

[0145] Where, T abc-αβ0 Represents the abc-αβ0 coordinate system transformation matrix.

[0146] It can be understood that the specific steps for separating the positive and negative sequences of the AC side output voltage signal and the load current signal after the Clark transformation are prior art and will not be elaborated here;

[0147] In some embodiments, when the positive and negative sequence separation transformation module performs positive and negative sequence separation, the transfer function of the orthogonal lag variable is used; among them, the α lagging by 90° q The transfer function from α to α is:

[0148]

[0149] Among them, α q represents the lagging component of the α component after Clark transformation, and α represents the α component after Clark transformation; the amplitude-frequency characteristic curve of this transfer function is as Figure 4 shown.

[0150] Similarly, the transfer function from β lagging by 90° q to β is:

[0151]

[0152] Among them, β q represents the lagging component of the β component after Clark transformation, and β represents the β component after Clark transformation.

[0153] In some embodiments, the positive and negative sequence separation transformation module performs positive and negative sequence separation on the AC side output voltage signal and the load current signal after Clark transformation, and respectively obtains the positive sequence α component α P and the positive sequence β component β P , the negative sequence α component α N and the negative sequence β component β N ;

[0154] The expression of the positive sequence α P is:

[0155]

[0156] The expression of the positive sequence β P is:

[0157]

[0158] The expression of the negative sequence α N is:

[0159]

[0160] The expression of the negative sequence β N is:

[0161]

[0162] It can be understood that the specific steps of performing Park transformation on the AC-side output voltage signal and the load current signal after positive and negative sequence separation to obtain the variables under the positive and negative sequence dq axes are prior art and will not be elaborated here;

[0163] It can be understood that the specific steps of performing inverse Park transformation on the current-loop output modulation signals under positive and negative sequences are prior art and will not be elaborated here;

[0164] In some embodiments, the αβ-dq transformation matrix in the pre-configured positive and negative sequence coordinate systems is:

[0165]

[0166] Among them, represents the αβ-dq transformation matrix in the positive sequence coordinate system, represents the αβ-dq transformation matrix in the negative sequence coordinate system, and θ represents the rotation angle from the α-β coordinate system to the d-q rotating coordinate system.

[0167] It should be noted that after inverse Park transformation, α P , β P , α N , β N are added and limited;

[0168] α = α P + α N

[0169] β = β P + β N

[0170] Limiting requirements:

[0171]

[0172] It should also be noted that the unbalanced load voltage equalization and current limiting control module performs inverter voltage loop control on the dq axes in the positive and negative sequence coordinate systems. In the voltage loop control, with the goal of controlling the balance of the AC-side output voltage, the given values of the negative-sequence AC d, q and are set to 0.

[0173] As shown in the appendix Figure 5 , abc is the three-phase coordinate system, αβ is the two-phase coordinate system, d P and q P are respectively the positive-sequence rotating coordinate systems, d N and q N are respectively the negative-sequence rotating coordinate systems; i P represents the positive-sequence component, i N represents the negative-sequence component, d’ and q’ are the virtual reference coordinate systems; the d’ axis and iN In the same direction, due to the positive sequence coordinate system d P and q P rotating counterclockwise at an angular velocity ω, the negative sequence coordinate system d N and q N rotate clockwise at an angular velocity -ω. Then, relative to the d' and q' virtual reference coordinate systems, i P rotates counterclockwise at an angular velocity of 2ω, and when i P and i N coincide, the given value of the off-grid inverter current loop is the largest. Therefore, it is necessary to satisfy:

[0174]

[0175] wherein, represents the peak value of the effective value of the current limiting value.

[0176] It can be understood that the SVPWM drive calculation module sends the αβ values obtained after the inverse Park transformation to the SVPWM function to generate the required PWM drive signal. The specific steps are prior art and will not be elaborated here.

[0177] It should be understood that although the steps in the flowcharts involved in the above embodiments are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0178] Embodiment 6

[0179] Based on the same inventive concept, the embodiment of the present application also provides a voltage equalization and current limiting control device for an off-grid inverter under unbalanced loads, which includes a processor, a communication interface, a memory, and a communication bus. Among them, the processor, the communication interface, and the memory complete mutual communication through the communication bus; the memory is used to store computer programs; when the processor executes the programs stored on the memory, it realizes the voltage equalization and current limiting control method of the off-grid inverter under unbalanced loads as in Embodiment 1, 2, or 3.

[0180] The solution provided by this device for problem-solving is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the voltage equalization and current limiting control device for off-grid inverters under unbalanced loads provided below can refer to the limitations on the voltage equalization and current limiting control method for off-grid inverters under unbalanced loads in the foregoing text, and will not be elaborated here.

[0181] This embodiment also provides a specific implementation of a readable storage medium, on which instructions are stored. When executed by one or more processors, the instructions cause the processors to execute the voltage equalization and current limiting control method for off-grid inverters under unbalanced loads as described in Embodiments 1, 2, 3, or 4.

[0182] This embodiment also provides a computer program product, including a computer program / instructions, characterized in that when the computer program / instructions are executed by a processor, the voltage equalization and current limiting control method for off-grid inverters under unbalanced loads as described in Embodiments 1, 2, 3, or 4 is implemented.

[0183] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memories can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memories can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., without limitation.

[0184] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0185] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A voltage-sharing and current-limiting control method for an off-grid inverter under unbalanced load, characterized in that: include: Determine the AC side load imbalance e of the three-phase three-wire off-grid inverter; according to the AC side load imbalance e, set two thresholds, namely, the first threshold e1=2% and the second threshold e2=100%; the calculation formula of the imbalance e is: Among them, I max is the maximum value of the AC side load current, I min is the minimum value of the AC side load current; Based on the negative sequence voltage q-axis sampling real value Generate the initial set value of the negative sequence q axis of the current loop Based on the negative sequence voltage d-axis sampling real value Generate the negative sequence d-axis initial reference value of the current loop Based on the real value of the positive sequence voltage q-axis sampling Generate the initial set value of the positive sequence q axis of the current loop Based on the real value of positive sequence voltage d-axis sampling Generate the initial set value of the positive sequence d axis of the current loop Determine the negative sequence voltage q-axis limit value and negative sequence voltage d-axis limit value Determine the positive sequence voltage q-axis limit value and positive sequence voltage d-axis limit value When the first threshold value ≤ the AC side load imbalance degree e ≤ the second threshold value, the three-phase three-wire off-grid inverter implements the current and voltage limiting control strategy: ① Determine the initial given value of the positive sequence d axis Is it greater than or equal to the positive sequence voltage d-axis limit value? If so, based on the positive sequence voltage d-axis limit value Determine the actual set value of the positive sequence d-axis of the current loop If not, then based on the positive sequence d axis initial given value Determine the actual set value of the positive sequence d-axis of the current loop ② Determine the initial given value of the positive sequence q axis Is it greater than or equal to the positive sequence voltage q-axis limit value? If so, based on the positive sequence voltage q-axis limit value Determine the actual set value of the positive sequence q axis of the current loop If not, then based on the positive sequence q axis initial given value Determine the actual set value of the positive sequence q axis of the current loop ③ Determine the initial given value of the negative sequence d axis Is it greater than or equal to the negative sequence voltage d-axis limit value? If so, based on the negative sequence voltage d-axis limit value Determine the negative sequence d-axis true set value of the current loop If not, then based on the negative sequence d axis initial given value Determine the negative sequence d-axis true set value of the current loop ④ Determine the initial given value of the negative sequence q axis Is it greater than or equal to the negative sequence voltage q axis limit value? If so, based on the negative sequence voltage q-axis limit value Determine the negative sequence q axis real set value of the current loop If not, then based on the positive sequence q axis initial given value Determine the negative sequence q axis real set value of the current loop The three-phase three-wire off-grid inverter is based on the positive sequence d-axis real given value of the current loop Negative sequence d-axis actual reference value Positive sequence q axis real set value And the negative sequence q axis real set value Perform voltage-sharing and current-limiting control.

2. The voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load according to claim 1, characterized in that: Set the third threshold value e3 = 30%; When the third threshold value ≤ the AC side load imbalance degree e ≤ the second threshold value, the dual closed-loop control loop of the three-phase three-wire off-grid inverter performs voltage limiting and balanced output according to the following formula: Among them, α P It indicates the output voltage peak value of the three-phase three-wire off-grid inverter with voltage limiting and equalization. It represents the peak value of the effective value of the rated AC side output phase voltage of the three-phase three-wire off-grid inverter, and Δv represents the voltage drop on the internal inductance line of the three-phase three-wire off-grid inverter.

3. The voltage-sharing and current-limiting control method for an off-grid inverter under unbalanced load according to claim 1 or 2, characterized in that: The initial given value of the negative sequence q axis of the generated current loop Negative sequence d axis initial given value Positive sequence q axis initial given value and the initial given value of the positive sequence d axis Determine the actual given value of the positive and negative sequence dq axis of the current loop by eliminating the negative sequence, limiting the positive sequence, protecting the reactive power and limiting the active power: (1) Calculate the negative sequence dq axis limit value first, and then calculate the positive sequence dq axis limit value; when calculating the positive sequence dq axis limit value, use the positive sequence reactive power limit to give the maximum value to calculate the upper and lower limits of the positive sequence d axis and q axis; (2) Then make the following logical judgment: The positive-sequence dq axis real given value of the current loop is determined by comparing the positive-sequence dq axis initial given value and the positive-sequence voltage dq axis limit value: if the positive-sequence dq axis initial given value ≥ the positive-sequence voltage dq axis limit value, then the positive-sequence dq axis real given value of the current loop = the positive-sequence voltage dq axis limit value; if the positive-sequence dq axis initial given value < the positive-sequence voltage dq axis limit value, then the positive-sequence dq axis real given value of the current loop = the positive-sequence dq axis initial given value; The negative-sequence dq axis real given value of the current loop is determined by comparing the negative-sequence dq axis initial given value and the negative-sequence voltage dq axis limit value: if the negative-sequence dq axis initial given value ≥ the negative-sequence voltage dq axis limit value, then the negative-sequence dq axis real given value of the current loop = the negative-sequence voltage dq axis limit value; if the negative-sequence dq axis initial given value < the negative-sequence voltage dq axis limit value, then the negative-sequence dq axis real given value of the current loop = the negative-sequence dq axis initial given value.

4. The voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load according to claim 3, characterized in that: When calculating the negative sequence dq axis limit value, first calculate the negative sequence voltage q axis limit value 5. The voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load according to claim 4, characterized in that: Determine the negative sequence voltage q-axis limit value and negative sequence voltage d-axis limit value When executing: The negative sequence voltage q-axis limit value is generated using the following formula: The negative sequence voltage d-axis limit value is generated using the following formula: in, represents the peak value of the effective value of the output phase current on the AC side of the three-phase three-wire off-grid inverter, It represents the real value of the negative-sequence current q-axis sampling of the three-phase three-wire off-grid inverter, and abs represents the absolute value calculation.

6. The voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load according to claim 4, characterized in that: Determine the positive sequence voltage q-axis limit value and positive sequence voltage d-axis limit value When executing: The positive sequence voltage q-axis limit value is generated by the following formula: The positive sequence voltage d-axis limit value is generated by the following formula: in, Represents the total amplitude limit value of the positive sequence, represents the peak value of the effective value of the output phase current on the AC side of the three-phase three-wire off-grid inverter, It represents the real value of the negative sequence current d-axis sampling of the three-phase three-wire off-grid inverter. It represents the real value of the negative-sequence current q-axis sampling of the three-phase three-wire off-grid inverter, and abs represents the absolute value calculation.

7. A voltage-sharing and current-limiting control system for an off-grid inverter under unbalanced load, characterized in that: It includes abc-αβ0 coordinate system transformation module, positive and negative sequence separation transformation module, αβ-dq coordinate system transformation module, unbalanced load voltage-sharing and current-limiting control module, current loop control module, positive and negative sequence dq-αβ coordinate system transformation module and SVPWM drive calculation module; among which, The abc-αβ0 coordinate system transformation module is used to perform Clark transformation on the AC side output voltage signal and load current signal of the three-phase three-wire off-grid inverter using a pre-configured abc-αβ0 coordinate system transformation matrix; The positive-negative sequence separation and transformation module is used to perform positive-negative sequence separation on the AC side output voltage signal and the load current signal after Clark transformation; The αβ-dq coordinate system transformation module is used to use the pre-configured αβ-dq transformation matrix in the positive and negative sequence coordinate system to perform Park transformation on the AC side output voltage signal and load current signal after positive and negative sequence separation to obtain variables under the positive and negative sequence dq axis; wherein the variables under the positive and negative sequence dq axis include the real value of the negative sequence voltage q axis sampling Negative sequence voltage d-axis sampling true value Negative sequence current q-axis sampling real value Negative sequence current d-axis sampling true value Positive sequence voltage q-axis sampling real value And the actual value of the positive sequence voltage d-axis sampling The unbalanced load voltage-sharing and current-limiting control module is used to execute the voltage-sharing and current-limiting control method of the off-grid inverter under unbalanced load according to any one of claims 1 to 6; The current loop control module is used to generate a positive-sequence d-axis real given value based on the unbalanced load voltage-sharing and current-limiting control module. Negative sequence d-axis actual reference value Positive sequence q axis real set value And the negative sequence q axis real set value Generate a voltage modulation signal in a positive and negative sequence dq coordinate system, and use the voltage modulation signal as a current loop output modulation signal; The positive and negative sequence dq-αβ coordinate system transformation module is used to perform an inverse Park transformation on the current loop output modulation signal under the positive and negative sequence; The SVPWM drive calculation module is used to generate a corresponding PWM drive signal based on the current loop output modulation signal after inverse Park transformation.

8. A voltage-sharing and current-limiting control device for an off-grid inverter under unbalanced load, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus; Memory, used to store computer programs; The processor is used to implement the voltage-sharing and current-limiting control method of the off-grid inverter under unbalanced load as described in any one of claims 1 to 6 when executing the program stored in the memory.

9. A readable storage medium, characterized in that: Instructions are stored thereon, and when executed by one or more processors, the processors are enabled to execute the voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load as described in any one of claims 1 to 6.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the voltage-sharing and current-limiting control method for an off-grid inverter under an unbalanced load is implemented as described in any one of claims 1 to 6.

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