Power electronic equipment low voltage ride through control method and system based on negative sequence current

Abstract

The invention provides a power electronic equipment low-voltage ride-through control method and system based on negative sequence current, and the method comprises the steps: carrying out the primary amplitude limiting and secondary amplitude limiting of an instruction value of positive and negative sequence current of an outer ring according to a predetermined positive and negative sequence current instruction threshold interval; according to the instruction value of the positive sequence current obtained after primary amplitude limiting, the instruction value of the negative sequence current obtained after secondary amplitude limiting and the measured values of the corresponding positive and negative sequence current, positive and negative sequence voltage reference values are obtained through a transfer function of an inner loop controller; based on the positive and negative sequence voltage reference values, adopting coordinate system conversion to generate positive and negative sequence instruction values, and controlling the power electronic equipment to complete low voltage ride through according to the positive and negative sequence instruction values; the negative-sequence current instruction protection range is reasonable limitation of the negative-sequence current instruction value in the fault period, the effect of reducing the negative-sequence component of the system is achieved, the state before the fault can be rapidly recovered, and conflict with new energy control is avoided.

Description

Technical Field

[0001] The patent application of this invention belongs to the technical field of power electronic devices, and specifically relates to a low voltage ride-through control method and system for power electronic equipment based on negative sequence current. Background Art

[0002] Power electronic fault ride-through after new energy access refers to the ability of new energy equipment (such as photovoltaic power stations and wind turbines) to ensure continuous operation without disconnection from the grid and smoothly transition to normal operation when the voltage or frequency at the grid connection point of new energy exceeds the normal operating range allowed by the standard due to power system accidents or disturbances. When the power system fails or is disturbed, the voltage or frequency at the grid connection point may change. At this time, new energy equipment needs to use certain control strategies and technical means to ensure continuous operation without disconnection from the grid. This requires the equipment to have a certain fault ride-through capability, including the ability to cope with transient processes such as overcurrent, low voltage, and overspeed. In order to achieve power electronic fault ride-through after new energy access, a series of technical measures and management measures need to be taken. For example, for photovoltaic power stations, inverter control strategies can be adopted to dynamically adjust the output voltage and current of the inverter according to the changes in grid voltage and frequency to ensure continuous operation without disconnection from the grid. For wind turbines, doubly fed induction generator control strategies can be adopted to control the voltage and current on the stator and rotor sides of the generator to ensure that the wind turbine can continue to operate in the event of a grid failure. In order to improve the fault ride-through capability of new energy equipment, it is also necessary to strengthen equipment maintenance and management. For example, regularly inspect and overhaul equipment to promptly identify and address hidden dangers and faults in the equipment to ensure the healthy operation of the equipment.

[0003] During the low voltage ride-through process performed by the existing power electronic device control strategy, it is often difficult to quickly recover to normal operating conditions. The main reason for this is that the power electronic control strategy does not reasonably limit the negative sequence current during the fault period, resulting in difficulty in recovery after the fault. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention patent application proposes a low voltage ride-through control method for power electronic equipment based on negative sequence current, comprising:

[0005] According to the predetermined positive and negative sequence current command threshold interval, the command values ​​of the positive and negative sequence currents of the outer loop are limited once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence currents and the command values ​​of the negative sequence currents;

[0006] According to the preset negative sequence current command protection range, the command value of the negative sequence current after the primary limitation is subjected to secondary limitation;

[0007] According to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, the positive and negative sequence voltage reference values ​​are obtained through the transfer function of the inner loop controller;

[0008] Based on the positive and negative sequence voltage reference values, coordinate system conversion is adopted to generate positive and negative sequence command values, and according to the positive and negative sequence command values, power electronic equipment is controlled to complete low voltage ride-through.

[0009] Preferably, the positive and negative sequence current command threshold interval includes a negative sequence current command threshold interval and a positive sequence current command threshold interval; the positive and negative sequence current command values ​​of the outer loop are limited once according to the predetermined positive and negative sequence current command threshold interval, including:

[0010] According to the command value of the negative sequence current of the outer loop, a preset negative sequence current command threshold interval is adopted to obtain the command value of the negative sequence current after primary limiting;

[0011] According to the command value of the positive sequence current of the outer loop, a pre-set positive sequence current command threshold interval is adopted to obtain the command value of the positive sequence current after primary limiting;

[0012] Among them, the command value of the positive-sequence current includes a positive-sequence d-axis current command value and a positive-sequence q-axis current command value; the command value of the negative-sequence current includes a negative-sequence d-axis current command value and a negative-sequence q-axis current command value; the command value of the positive-sequence current after the primary limitation includes: the positive-sequence d-axis current command value after the primary limitation and the positive-sequence q-axis current command value after the primary limitation; the command value of the negative-sequence current after the primary limitation includes: the negative-sequence d-axis current command value after the primary limitation and the negative-sequence q-axis current command value after the primary limitation.

[0013] Preferably, the second limiting of the command value of the negative sequence current after the primary limiting is performed according to the preset negative sequence current command protection range, comprises:

[0014] When a fault voltage drop is detected, the command value of the negative sequence current after the primary amplitude limiting is adjusted to within the negative sequence current command protection range according to a preset negative sequence current command protection range;

[0015] When the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold interval to obtain the command value of the negative sequence current after secondary limiting;

[0016] The command value of the negative-sequence current after secondary limiting includes: a negative-sequence d-axis current command value after secondary limiting and a negative-sequence q-axis current command value after secondary limiting.

[0017] Preferably, the negative sequence current command protection range is greater than 0.05pu and less than 0.5pu.

[0018] Preferably, before limiting the command value of the positive and negative sequence current of the outer loop once according to the predetermined positive and negative sequence current command threshold interval, the method further includes:

[0019] Determine whether the outer loop control exists. If so, set the outer loop control strategy to network control and set the inner loop control simultaneously.

[0020] If it does not exist, the inner loop control is set directly;

[0021] Wherein, the inner loop control includes negative sequence current control.

[0022] Preferably, the positive and negative sequence voltage reference values ​​are obtained by using the transfer function of the inner loop controller according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, including:

[0023] Calculate the difference between the negative-sequence d-axis current command value after secondary limiting and the corresponding negative-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the negative-sequence d-axis command value, and calculate the negative-sequence d-axis voltage reference value according to the negative-sequence d-axis command value and the negative-sequence d-axis voltage related parameters using the negative-sequence d-axis voltage reference value calculation formula;

[0024] Calculate the difference between the positive-sequence d-axis current command value after primary limiting and the corresponding positive-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive-sequence d-axis command value, and calculate the positive-sequence d-axis voltage reference value according to the positive-sequence d-axis command value and the positive-sequence d-axis voltage related parameters using the positive-sequence d-axis voltage reference value calculation formula;

[0025] Calculate the difference between the negative-sequence q-axis current command value after secondary limiting and the corresponding negative-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value, and calculate the negative-sequence q-axis voltage reference value according to the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters using the negative-sequence q-axis voltage reference value calculation formula;

[0026] Calculate the difference between the positive-sequence q-axis current command value after primary limiting and the corresponding positive-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value, and calculate the positive-sequence q-axis voltage reference value according to the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters using the positive-sequence q-axis voltage reference value calculation formula;

[0027] The positive-sequence q-axis voltage related parameters include one or more of the following: angular velocity, equivalent inductance and measured value of positive-sequence d-axis current.

[0028] Preferably, the expression of the transfer function is as follows:

[0029] G(S)=KP+Ki÷S

[0030] Among them, G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0031] Preferably, the positive sequence q-axis voltage reference value is calculated as follows:

[0032]

[0033] in, is the positive sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence d-axis current, is the measured value of the positive sequence q-axis current, qrr + is the positive sequence q-axis command value.

[0034] Preferably, the generating of positive and negative sequence command values ​​by using coordinate system conversion based on the positive and negative sequence voltage reference values, and controlling the power electronic equipment to complete low voltage ride through according to the positive and negative sequence command values, comprises:

[0035] Based on the positive-sequence d-axis voltage reference value and the positive-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a positive-sequence command value;

[0036] Based on the negative-sequence d-axis voltage reference value and the negative-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a negative-sequence command value;

[0037] According to the positive and negative sequence command values, the power electronic equipment is controlled to complete low voltage ride-through.

[0038] Based on the same inventive concept, the patent application of the present invention also provides a low voltage ride-through control system for power electronic equipment based on negative sequence current, including: a primary limiter module, a secondary limiter module, a positive and negative sequence voltage reference value calculation module and a low voltage ride-through module;

[0039] The primary amplitude limiting module is used to perform a primary amplitude limiting on the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold interval; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current;

[0040] The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after primary limiting according to a preset negative sequence current command protection range;

[0041] The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents;

[0042] The low voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system conversion, and control the power electronic equipment to complete low voltage ride-through according to the positive and negative sequence command values.

[0043] Preferably, the positive and negative sequence current command threshold interval includes a negative sequence current command threshold interval and a positive sequence current command threshold interval; the primary amplitude limiting module is used to:

[0044] According to the command value of the negative sequence current of the outer loop, a preset negative sequence current command threshold interval is adopted to obtain the command value of the negative sequence current after primary limiting;

[0045] According to the command value of the positive sequence current of the outer loop, a pre-set positive sequence current command threshold interval is adopted to obtain the command value of the positive sequence current after primary limiting;

[0046] Among them, the command value of the positive-sequence current includes a positive-sequence d-axis current command value and a positive-sequence q-axis current command value; the command value of the negative-sequence current includes a negative-sequence d-axis current command value and a negative-sequence q-axis current command value; the command value of the positive-sequence current after the primary limitation includes: the positive-sequence d-axis current command value after the primary limitation and the positive-sequence q-axis current command value after the primary limitation; the command value of the negative-sequence current after the primary limitation includes: the negative-sequence d-axis current command value after the primary limitation and the negative-sequence q-axis current command value after the primary limitation.

[0047] Preferably, the secondary limiting module is used for:

[0048] When a fault voltage drop is detected, the command value of the negative sequence current after the primary amplitude limiting is adjusted to within the negative sequence current command protection range according to a preset negative sequence current command protection range;

[0049] When the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold interval to obtain the command value of the negative sequence current after secondary limiting;

[0050] The command value of the negative-sequence current after secondary limiting includes: a negative-sequence d-axis current command value after secondary limiting and a negative-sequence q-axis current command value after secondary limiting.

[0051] Preferably, the negative sequence current command protection range is greater than 0.05pu and less than 0.5pu.

[0052] Preferably, the system further comprises: an inner and outer loop control module, which is used to:

[0053] Determine whether the outer loop control exists. If so, set the outer loop control strategy to network control and set the inner loop control simultaneously.

[0054] If it does not exist, the inner loop control is set directly;

[0055] Wherein, the inner loop control includes negative sequence current control.

[0056] Preferably, the positive and negative sequence voltage reference value calculation module is used to:

[0057] Calculate the difference between the negative-sequence d-axis current command value after secondary limiting and the corresponding negative-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the negative-sequence d-axis command value, and calculate the negative-sequence d-axis voltage reference value according to the negative-sequence d-axis command value and the negative-sequence d-axis voltage related parameters using the negative-sequence d-axis voltage reference value calculation formula;

[0058] Calculate the difference between the positive-sequence d-axis current command value after primary limiting and the corresponding positive-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive-sequence d-axis command value, and calculate the positive-sequence d-axis voltage reference value according to the positive-sequence d-axis command value and the positive-sequence d-axis voltage related parameters using the positive-sequence d-axis voltage reference value calculation formula;

[0059] Calculate the difference between the negative-sequence q-axis current command value after secondary limiting and the corresponding negative-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value, and calculate the negative-sequence q-axis voltage reference value according to the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters using the negative-sequence q-axis voltage reference value calculation formula;

[0060] Calculate the difference between the positive-sequence q-axis current command value after primary limiting and the corresponding positive-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value, and calculate the positive-sequence q-axis voltage reference value according to the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters using the positive-sequence q-axis voltage reference value calculation formula;

[0061] The positive-sequence q-axis voltage related parameters include one or more of the following: angular velocity, equivalent inductance and measured value of positive-sequence d-axis current.

[0062] Preferably, the expression of the transfer function is as follows:

[0063] G(S)=KP+Ki÷S

[0064] Among them, G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0065] Preferably, the positive sequence q-axis voltage reference value is calculated as follows:

[0066]

[0067] in, is the positive sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence d-axis current, is the measured value of the positive sequence q-axis current, qrr + is the positive sequence q-axis command value.

[0068] Preferably, the low voltage ride through module is used for:

[0069] Based on the positive-sequence d-axis voltage reference value and the positive-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a positive-sequence command value;

[0070] Based on the negative-sequence d-axis voltage reference value and the negative-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a negative-sequence command value;

[0071] According to the positive and negative sequence command values, the power electronic equipment is controlled to complete low voltage ride-through.

[0072] Based on the same inventive concept, the patent application of the present invention also provides an electronic device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0073] The memory is used to store one or more programs;

[0074] When the one or more programs are executed by the at least one processor, the above-mentioned low voltage ride-through control method for power electronic equipment based on negative sequence current is implemented.

[0075] Based on the same inventive concept, the patent application of the present invention also provides a readable storage medium on which an execution program is stored. When the execution program is executed, a low voltage ride-through control method for power electronic equipment based on negative sequence current as described above is implemented.

[0076] Compared with the closest prior art, the patent application of this invention has the following beneficial effects:

[0077] The patent application of the present invention provides a low voltage ride-through control method and system for power electronic equipment based on negative sequence current, including: according to a predetermined positive and negative sequence current command threshold interval, the command value of the positive and negative sequence current of the outer loop is limited once; the command value of the positive and negative sequence current includes the command value of the positive sequence current and the command value of the negative sequence current; according to a preset negative sequence current command protection range, the command value of the negative sequence current after the primary limit is limited twice; according to the command value of the positive sequence current obtained after the primary limit, the command value of the negative sequence current obtained after the secondary limit and the corresponding measured value of the positive and negative sequence current, the positive and negative sequence voltage reference value is obtained through the transfer function of the inner loop controller; based on the positive and negative sequence voltage reference value, the coordinate system conversion is adopted to generate the positive and negative sequence command value, and according to the positive and negative sequence command value, the power electronic equipment is controlled to complete the low voltage ride-through; the negative sequence current command protection range of the present invention is a reasonable limit of the negative sequence current command value during the fault period, so as to achieve the effect of reducing the negative sequence component of the system, and achieve rapid recovery to the pre-fault state without conflicting with the new energy control. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 A schematic flow chart of a low voltage ride-through control method for power electronic equipment based on negative sequence current provided for the patent application of the present invention;

[0079] Figure 2 A schematic diagram of a low voltage ride-through control system for power electronic equipment based on negative sequence current provided for the patent application of the present invention;

[0080] Figure 3 A schematic structural diagram of an electronic device provided for the patent application of the present invention. DETAILED DESCRIPTION

[0081] The specific implementation methods of the patent application of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0082] Embodiment 1:

[0083] The present invention provides a method for controlling low voltage ride-through of power electronic equipment based on negative sequence current. Figure 1 As shown, including:

[0084] Step 1: According to a predetermined positive and negative sequence current command threshold interval, the command values ​​of the positive and negative sequence currents of the outer loop are limited once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current;

[0085] Step 2: According to the preset negative sequence current command protection range, the command value of the negative sequence current after the primary limiting is subjected to secondary limiting;

[0086] Step 3: According to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, the positive and negative sequence voltage reference values ​​are obtained through the transfer function of the inner loop controller;

[0087] Step 4: Based on the positive and negative sequence voltage reference values, coordinate system conversion is used to generate positive and negative sequence command values, and according to the positive and negative sequence command values, power electronic equipment is controlled to complete low voltage ride-through.

[0088] Before step 1 above, also include:

[0089] Determine whether the outer loop control exists. If so, set the outer loop control strategy to network control and set the inner loop control simultaneously.

[0090] If it does not exist, the inner loop control is set directly;

[0091] Wherein, the inner loop control includes negative sequence current control.

[0092] For example, the relationship between the outer-loop control strategy and the negative-sequence current limiting link is set as follows: determine whether the outer-loop control exists, and if so, set the outer-loop control strategy to grid-forming control; when the outer-loop control strategy is grid-forming, the inner-loop is synchronously set to include a negative-sequence current limiting link; the present invention limits the outer loop to grid-forming control, but in order to ensure that the grid-forming control does not conflict with the grid-forming control of wind power, negative-sequence current control is set in the inner power loop.

[0093] The positive and negative sequence current command threshold intervals in step 1 include a negative sequence current command threshold interval and a positive sequence current command threshold interval; the positive and negative sequence current command values ​​of the outer loop are limited once according to the predetermined positive and negative sequence current command threshold intervals, including:

[0094] According to the command value of the negative sequence current of the outer loop, a preset negative sequence current command threshold interval is adopted to obtain the command value of the negative sequence current after primary limiting;

[0095] For example, the command value of the negative sequence current needs to be limited by a preset negative sequence current command threshold range before being used as a given value for the inner loop control;

[0096] The command value of the negative sequence current needs to meet the negative sequence current command threshold range, as follows:

[0097]

[0098]

[0099] in, is the command value of the negative sequence d-axis current, is the command value of the negative-sequence q-axis current, L3 is the upper limit value of the negative-sequence current command threshold interval, and L4 is the lower limit value of the negative-sequence current command threshold interval;

[0100] When the command value of the negative-sequence d-axis current and the command value of the negative-sequence q-axis current exceed the limit of the negative-sequence current command threshold interval, L3 or L4, the outer loop controller limits its output selection to the corresponding limit value of L3 or L4 at that time;

[0101] Before performing inner loop control, it is necessary to ensure that the command value of the negative sequence current is within the allowable range. Specifically, this range is defined by two limits: L4 (the lower limit of the negative sequence current command threshold interval) and L3 (the upper limit of the negative sequence current command threshold interval), both of which must satisfy the interval from L4 to L3. If any command value exceeds this range, the outer loop controller will limit its output and select the closest limit value (L3 or L4) as the output. The purpose of this is to protect the power system and equipment and avoid potential problems caused by negative sequence current command values ​​that exceed the range. In summary, this is a limiting process to ensure that the negative sequence current command value is within a reasonable range.

[0102] According to the command value of the positive sequence current of the outer loop, a pre-set positive sequence current command threshold interval is adopted to obtain the command value of the positive sequence current after primary limiting;

[0103] For example, the command value of the positive sequence current and the command value of the negative sequence current need to be limited before being used as the given value of the inner loop control;

[0104] The command value of the positive sequence current needs to satisfy the following formula:

[0105]

[0106]

[0107] in, is the command value of the positive sequence d-axis current, is the positive-sequence q-axis current command value, L1 is the upper limit of the positive-sequence current command threshold interval, and L2 is the lower limit of the positive-sequence current command threshold interval;

[0108] When the command value of the positive-sequence d-axis current and the command value of the positive-sequence q-axis current exceed the limit of the positive-sequence current command threshold interval, that is, L1 or L2, the outer loop controller limits its output selection to the corresponding limit value of L1 or L2 at that time;

[0109] Both the command value of the positive sequence current and the command value of the negative sequence current need to be limited before being used as a given value for the inner loop control. This is to ensure that the current command value is within a reasonable range, thereby protecting the power system and equipment. This means that the command value of the positive sequence current must be between L2 and L1. When the command value of the positive sequence current exceeds this range, that is, exceeds L1 or is lower than L2, the outer loop controller intervenes and limits its output. The outer loop controller selects the closest limit value (L1 or L2) as the output to ensure that the current command value does not exceed the set safety range. Similarly, the command value of the negative sequence current also needs to meet similar limiting conditions and is limited by the outer loop controller when it exceeds the range. In summary, the command values ​​of both the positive and negative sequence currents need to be limited to ensure that they remain within the allowable range before the inner loop control. If the command value exceeds this range, the outer loop controller will take appropriate measures to limit the output, thereby protecting the safe operation of the power system and equipment.

[0110] Among them, the command value of the positive-sequence current includes a positive-sequence d-axis current command value and a positive-sequence q-axis current command value; the command value of the negative-sequence current includes a negative-sequence d-axis current command value and a negative-sequence q-axis current command value; the command value of the positive-sequence current after the primary limiting includes: the positive-sequence d-axis current command value after the primary limiting and the positive-sequence q-axis current command value after the primary limiting; the command value of the negative-sequence current after the primary limiting includes: the negative-sequence d-axis current command value after the primary limiting and the negative-sequence q-axis current command value after the primary limiting; the present invention obtains the command values ​​of the positive and negative sequence currents after limiting by performing a primary limiting on the command values ​​of the positive and negative sequence currents of the outer ring, thereby providing data for subsequent secondary limiting.

[0111] The above step 2, according to the preset negative sequence current command protection range, performs secondary limiting on the command value of the negative sequence current after the primary limiting, including:

[0112] When a fault voltage drop is detected, the command value of the negative sequence current after the primary amplitude limiting is adjusted to within the negative sequence current command protection range according to a preset negative sequence current command protection range;

[0113] When the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold interval to obtain the command value of the negative sequence current after secondary limiting;

[0114] For example, after the fault is cleared, the limiting of the negative sequence inner loop is restored to the limiting limits L1 and L2. The reason for performing a secondary limiting on the command value of the negative sequence current after the primary limiting is that during the negative sequence current setting process, if it is set to 0, it may cause a conflict with the control strategy of the wind turbine and fail to balance the voltage. However, if the negative sequence current is lowered, it can cooperate with wind power to achieve the purpose of suppressing the negative sequence voltage. Ultimately, the negative sequence voltage will be reduced to 0. This is because, with the same control target, different controllers may not be able to truly stabilize to a unified timing.

[0115] The command value of the negative-sequence current after secondary limiting includes: a negative-sequence d-axis current command value after secondary limiting and a negative-sequence q-axis current command value after secondary limiting.

[0116] In one implementation, the negative-sequence current command protection range is greater than 0.05pu and less than 0.5pu; the specific value of the negative-sequence current command protection range of the present invention more specifically illustrates the numerical interval of the negative-sequence current command protection range; the negative-sequence current command protection range is a suppression strategy for the negative-sequence current during an additional fault period added to the inner-loop control, which is a reasonable restriction on the negative-sequence current command during a fault period and can achieve rapid fault-crossing recovery.

[0117] In the above step 3, according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, the positive and negative sequence voltage reference values ​​are obtained through the transfer function of the inner loop controller, including:

[0118] Calculate the difference between the negative-sequence d-axis current command value after secondary limiting and the corresponding negative-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the negative-sequence d-axis command value, and calculate the negative-sequence d-axis voltage reference value according to the negative-sequence d-axis command value and the negative-sequence d-axis voltage related parameters using the negative-sequence d-axis voltage reference value calculation formula;

[0119] For example, the negative sequence d-axis voltage reference value is calculated as follows:

[0120]

[0121] in, is the negative sequence d-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of negative sequence q-axis current, is the measured value of negative sequence d-axis current, drr - is the negative sequence d-axis command value;

[0122] Calculate the difference between the positive-sequence d-axis current command value after primary limiting and the corresponding positive-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive-sequence d-axis command value, and calculate the positive-sequence d-axis voltage reference value according to the positive-sequence d-axis command value and the positive-sequence d-axis voltage related parameters using the positive-sequence d-axis voltage reference value calculation formula;

[0123] For example, the positive sequence d-axis voltage reference value is calculated as follows:

[0124]

[0125] in, is the positive sequence d-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence q-axis current, is the measured value of the positive sequence d-axis current, drr + is the positive sequence d-axis command value;

[0126] Calculate the difference between the negative-sequence q-axis current command value after secondary limiting and the corresponding negative-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value, and calculate the negative-sequence q-axis voltage reference value according to the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters using the negative-sequence q-axis voltage reference value calculation formula;

[0127] For example, the negative sequence q-axis voltage reference value is calculated as follows:

[0128]

[0129] in, is the negative sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of negative sequence q-axis current, is the measured value of negative sequence q axis current, qrr - It is the negative sequence q-axis command value.

[0130] Calculate the difference between the positive-sequence q-axis current command value after primary limiting and the corresponding positive-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value, and calculate the positive-sequence q-axis voltage reference value according to the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters using the positive-sequence q-axis voltage reference value calculation formula;

[0131] The positive-sequence q-axis voltage related parameters include one or more of the following: angular velocity, equivalent inductance and measured value of positive-sequence d-axis current.

[0132] The implementation of the current inner loop control is illustrated in the following example, especially how the difference between the d-axis and q-axis current command values ​​and the actual values ​​is used to calculate the voltage reference value. These calculations are based on transfer functions and Laplace transform, as well as some basic electrical parameters of the motor. First, we calculate the difference between the d-axis and q-axis current command values ​​and the actual values. These differences are used as inputs to the d-axis and q-axis transfer functions. These transfer functions describe how the inner loop controller adjusts the voltage reference value according to the current error. In general, this process describes how to adjust the voltage reference value through the inner loop controller according to the difference between the current command value and the actual value, so as to achieve precise current control.

[0133] In one implementation, the transfer function is expressed as follows:

[0134] G(S)=KP+Ki÷S

[0135] Among them, G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0136] In one implementation, the positive sequence q-axis voltage reference value is calculated as follows:

[0137]

[0138] in, is the positive sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence d-axis current, is the measured value of the positive sequence q-axis current, qrr + is the positive-sequence q-axis command value; the present invention adjusts the positive- and negative-sequence voltage reference values ​​through an inner-loop controller according to the difference between the current command value and the measured value, thereby achieving precise current control.

[0139] The above step 4 uses coordinate system conversion based on the positive and negative sequence voltage reference values ​​to generate positive and negative sequence command values, and controls the power electronic equipment to complete low voltage ride-through according to the positive and negative sequence command values, including:

[0140] Based on the positive-sequence d-axis voltage reference value and the positive-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a positive-sequence command value;

[0141] Based on the negative-sequence d-axis voltage reference value and the negative-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a negative-sequence command value;

[0142] According to the positive and negative sequence command values, the power electronic equipment is controlled to complete low voltage ride-through.

[0143] For example, the positive sequence command value and the negative sequence command value are converted from the dq coordinate system to the abc coordinate system. The dq coordinate system is usually used to represent a rotating coordinate system, in which the d axis is aligned with the magnetic field direction and the q axis is perpendicular to the d axis. The abc coordinate system is a fixed three-phase coordinate system. After the conversion is completed, the positive sequence command value and the negative sequence command value under the abc coordinate system are obtained. These command values ​​can be directly used for the PWM control or other voltage control links of the motor; the present invention achieves the effect of reducing the negative sequence component of the system by adding an additional negative sequence current control strategy during the fault period to the negative sequence current in the inner loop control; the present invention achieves rapid recovery to the pre-fault state by adding an additional negative sequence current control strategy during the fault period to the negative sequence current in the inner loop control, and does not conflict with the new energy control; in order to achieve the situation that no oscillation occurs during the low voltage ride-through process, the present invention sets a strategy of lowering the negative sequence current command value and reducing the negative sequence current component of the system. In this way, the negative sequence current can be quickly kept within a smaller range, ensuring that it can be quickly recovered after the fault ends, and the magnitude of the fault current can be effectively suppressed.

[0144] Embodiment 2:

[0145] Based on the same inventive concept, the present invention patent application also provides a low voltage ride-through control system for power electronic equipment based on negative sequence current. Figure 2 As shown, it includes: a primary limiting module, a secondary limiting module, a positive and negative sequence voltage reference value calculation module and a low voltage ride-through module;

[0146] The primary amplitude limiting module is used to perform a primary amplitude limiting on the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold interval; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current;

[0147] The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after primary limiting according to a preset negative sequence current command protection range;

[0148] The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents;

[0149] The low voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system conversion, and control the power electronic equipment to complete low voltage ride-through according to the positive and negative sequence command values.

[0150] Preferably, the positive and negative sequence current command threshold interval includes a negative sequence current command threshold interval and a positive sequence current command threshold interval; the primary amplitude limiting module is used to:

[0151] According to the command value of the negative sequence current of the outer loop, a preset negative sequence current command threshold interval is adopted to obtain the command value of the negative sequence current after primary limiting;

[0152] According to the command value of the positive sequence current of the outer loop, a pre-set positive sequence current command threshold interval is adopted to obtain the command value of the positive sequence current after primary limiting;

[0153] Among them, the command value of the positive-sequence current includes a positive-sequence d-axis current command value and a positive-sequence q-axis current command value; the command value of the negative-sequence current includes a negative-sequence d-axis current command value and a negative-sequence q-axis current command value; the command value of the positive-sequence current after the primary limitation includes: the positive-sequence d-axis current command value after the primary limitation and the positive-sequence q-axis current command value after the primary limitation; the command value of the negative-sequence current after the primary limitation includes: the negative-sequence d-axis current command value after the primary limitation and the negative-sequence q-axis current command value after the primary limitation.

[0154] Preferably, the secondary limiting module is used for:

[0155] When a fault voltage drop is detected, the command value of the negative sequence current after the primary amplitude limiting is adjusted to within the negative sequence current command protection range according to a preset negative sequence current command protection range;

[0156] When the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold interval to obtain the command value of the negative sequence current after secondary limiting;

[0157] The command value of the negative-sequence current after secondary limiting includes: a negative-sequence d-axis current command value after secondary limiting and a negative-sequence q-axis current command value after secondary limiting.

[0158] Preferably, the negative sequence current command protection range is greater than 0.05pu and less than 0.5pu.

[0159] Preferably, the system further comprises: an inner and outer loop control module, which is used to:

[0160] Determine whether the outer loop control exists. If so, set the outer loop control strategy to network control and set the inner loop control simultaneously.

[0161] If it does not exist, the inner loop control is set directly;

[0162] Wherein, the inner loop control includes negative sequence current control.

[0163] Preferably, the positive and negative sequence voltage reference value calculation module is used to:

[0164] Calculate the difference between the negative-sequence d-axis current command value after secondary limiting and the corresponding negative-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the negative-sequence d-axis command value, and calculate the negative-sequence d-axis voltage reference value according to the negative-sequence d-axis command value and the negative-sequence d-axis voltage related parameters using the negative-sequence d-axis voltage reference value calculation formula;

[0165] Calculate the difference between the positive-sequence d-axis current command value after primary limiting and the corresponding positive-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive-sequence d-axis command value, and calculate the positive-sequence d-axis voltage reference value according to the positive-sequence d-axis command value and the positive-sequence d-axis voltage related parameters using the positive-sequence d-axis voltage reference value calculation formula;

[0166] Calculate the difference between the negative-sequence q-axis current command value after secondary limiting and the corresponding negative-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value, and calculate the negative-sequence q-axis voltage reference value according to the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters using the negative-sequence q-axis voltage reference value calculation formula;

[0167] Calculate the difference between the positive-sequence q-axis current command value after primary limiting and the corresponding positive-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value, and calculate the positive-sequence q-axis voltage reference value according to the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters using the positive-sequence q-axis voltage reference value calculation formula;

[0168] The positive-sequence q-axis voltage related parameters include one or more of the following: angular velocity, equivalent inductance and measured value of positive-sequence d-axis current.

[0169] Preferably, the expression of the transfer function is as follows:

[0170] G(S)=KP+Ki÷S

[0171] Among them, G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

[0172] Preferably, the positive sequence q-axis voltage reference value is calculated as follows:

[0173]

[0174] in, is the positive sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence d-axis current, is the measured value of the positive sequence q-axis current, qrr +is the positive sequence q-axis command value.

[0175] Preferably, the low voltage ride through module is used for:

[0176] Based on the positive-sequence d-axis voltage reference value and the positive-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a positive-sequence command value;

[0177] Based on the negative-sequence d-axis voltage reference value and the negative-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a negative-sequence command value;

[0178] According to the positive and negative sequence command values, the power electronic equipment is controlled to complete low voltage ride-through.

[0179] Example 3

[0180] like Figure 3 As shown, the present invention also provides an electronic device, which may be a computer device, a single-chip device, an intelligent mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, the processor, and the transceiver component are connected via a bus; the memory may be used to store an execution program, and an exemplary execution program may include instructions; the processor is used to execute the instructions stored in the memory. The memory may also be used to store data, which may be called and / or modified when the instructions are executed.

[0181] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a storage medium to implement a corresponding method flow or a corresponding function, so as to implement the steps of a low voltage ride-through control method for power electronic equipment based on negative sequence current in the above-mentioned embodiment.

[0182] Example 4

[0183] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in an electronic device for storing programs and data. It can be understood that the storage medium here can include both built-in storage media in electronic devices and, of course, extended storage media supported by electronic devices. The storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of a low voltage ride-through control method for power electronic equipment based on negative sequence current in the above embodiment.

[0184] It should be understood by those skilled in the art that the embodiments of the present invention patent application can be provided as methods, systems, or computer program products. Therefore, the present invention patent application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention patent application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0185] The present invention patent application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention patent application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0186] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0187] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the patent application of the present invention rather than to limit its protection scope. Although the patent application of the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the patent application of the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the protection scope of the claims to be approved.

Claims

1. A low voltage ride-through control method for power electronic equipment based on negative sequence current, characterized in that: include: According to the predetermined positive and negative sequence current command threshold interval, the command values ​​of the positive and negative sequence currents of the outer loop are limited once; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence currents and the command values ​​of the negative sequence currents; According to the preset negative sequence current command protection range, the command value of the negative sequence current after the primary limitation is subjected to secondary limitation; According to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, the positive and negative sequence voltage reference values ​​are obtained through the transfer function of the inner loop controller; Based on the positive and negative sequence voltage reference values, coordinate system conversion is adopted to generate positive and negative sequence command values, and according to the positive and negative sequence command values, power electronic equipment is controlled to complete low voltage ride-through.

2. The method according to claim 1, characterized in that The positive and negative sequence current command threshold interval includes a negative sequence current command threshold interval and a positive sequence current command threshold interval; the positive and negative sequence current command values ​​of the outer loop are limited once according to the predetermined positive and negative sequence current command threshold interval, including: According to the command value of the negative sequence current of the outer loop, a preset negative sequence current command threshold interval is adopted to obtain the command value of the negative sequence current after primary limiting; According to the command value of the positive sequence current of the outer loop, a pre-set positive sequence current command threshold interval is adopted to obtain the command value of the positive sequence current after primary limiting; Among them, the command value of the positive-sequence current includes a positive-sequence d-axis current command value and a positive-sequence q-axis current command value; the command value of the negative-sequence current includes a negative-sequence d-axis current command value and a negative-sequence q-axis current command value; the command value of the positive-sequence current after the primary limitation includes: the positive-sequence d-axis current command value after the primary limitation and the positive-sequence q-axis current command value after the primary limitation; the command value of the negative-sequence current after the primary limitation includes: the negative-sequence d-axis current command value after the primary limitation and the negative-sequence q-axis current command value after the primary limitation.

3. The method according to claim 2, characterized in that The method of performing secondary amplitude limiting on the negative sequence current command value after primary amplitude limiting according to the preset negative sequence current command protection range comprises: When a fault voltage drop is detected, the command value of the negative sequence current after the primary limiting is adjusted to within the negative sequence current command protection range according to the preset negative sequence current command protection range; When the fault voltage is cleared, the command value of the negative sequence current in the negative sequence current command range is limited by the positive sequence current command threshold interval to obtain the command value of the negative sequence current after secondary limiting; The command value of the negative-sequence current after secondary limiting includes: a negative-sequence d-axis current command value after secondary limiting and a negative-sequence q-axis current command value after secondary limiting.

4. The method according to claim 3, characterized in that The negative sequence current command protection range is greater than 0.05pu and less than 0.5pu.

5. The method according to claim 1, characterized in that Before limiting the positive and negative sequence current command values ​​of the outer loop according to the predetermined positive and negative sequence current command threshold interval, the method further includes: Determine whether the outer loop control exists. If so, set the outer loop control strategy to network control and set the inner loop control simultaneously. If it does not exist, the inner loop control is set directly; Wherein, the inner loop control includes negative sequence current control.

6. The method according to claim 3, characterized in that The positive and negative sequence voltage reference values ​​are obtained through the transfer function of the inner loop controller according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents, including: Calculate the difference between the negative-sequence d-axis current command value after secondary limiting and the corresponding negative-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the negative-sequence d-axis command value, and calculate the negative-sequence d-axis voltage reference value according to the negative-sequence d-axis command value and the negative-sequence d-axis voltage related parameters using the negative-sequence d-axis voltage reference value calculation formula; Calculate the difference between the positive-sequence d-axis current command value after primary limiting and the corresponding positive-sequence d-axis current measured value, and input the difference into the transfer function of the inner loop controller of the d-axis current to calculate the positive-sequence d-axis command value, and calculate the positive-sequence d-axis voltage reference value according to the positive-sequence d-axis command value and the positive-sequence d-axis voltage related parameters using the positive-sequence d-axis voltage reference value calculation formula; Calculate the difference between the negative-sequence q-axis current command value after secondary limiting and the corresponding negative-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the negative-sequence q-axis command value, and calculate the negative-sequence q-axis voltage reference value according to the negative-sequence q-axis command value and the negative-sequence q-axis voltage related parameters using the negative-sequence q-axis voltage reference value calculation formula; Calculate the difference between the positive-sequence q-axis current command value after primary limiting and the corresponding positive-sequence q-axis current measured value, and input the difference into the transfer function of the inner loop controller of the q-axis current to calculate the positive-sequence q-axis command value, and calculate the positive-sequence q-axis voltage reference value according to the positive-sequence q-axis command value and the positive-sequence q-axis voltage related parameters using the positive-sequence q-axis voltage reference value calculation formula; The positive-sequence q-axis voltage related parameters include one or more of the following: angular velocity, equivalent inductance and measured value of positive-sequence d-axis current.

7. The method according to claim 6, characterized in that The expression of the transfer function is as follows: G(S)=KP+Ki÷S Among them, G(S) is the transfer function, KP is the proportional coefficient, Ki is the integral coefficient, and S is the Laplace operator.

8. The method according to claim 6, characterized in that The positive sequence q-axis voltage reference value is calculated as follows: in, is the positive sequence q-axis voltage reference value, ω is the angular velocity, L is the equivalent inductance, is the measured value of the positive sequence d-axis current, is the measured value of the positive sequence q-axis current, qrr + is the positive sequence q-axis command value.

9. The method according to claim 6, characterized in that The method of generating positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system conversion, and controlling the power electronic equipment to complete low voltage ride through according to the positive and negative sequence command values, comprises: Based on the positive-sequence d-axis voltage reference value and the positive-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a positive-sequence command value; Based on the negative-sequence d-axis voltage reference value and the negative-sequence q-axis voltage reference value, coordinate transformation is performed from the dq coordinate system to the abc coordinate system to generate a negative-sequence command value; According to the positive and negative sequence command values, the power electronic equipment is controlled to complete low voltage ride-through.

10. A low voltage ride-through control system for power electronic equipment based on negative sequence current, characterized in that: include: Primary limiting module, secondary limiting module, positive and negative sequence voltage reference value calculation module and low voltage ride through module; The primary amplitude limiting module is used to perform a primary amplitude limiting on the command values ​​of the positive and negative sequence currents of the outer loop according to a predetermined positive and negative sequence current command threshold interval; the command values ​​of the positive and negative sequence currents include the command values ​​of the positive sequence current and the command values ​​of the negative sequence current; The secondary limiting module is used to perform secondary limiting on the command value of the negative sequence current after primary limiting according to a preset negative sequence current command protection range; The positive and negative sequence voltage reference value calculation module is used to obtain the positive and negative sequence voltage reference values ​​through the transfer function of the inner loop controller according to the command value of the positive sequence current obtained after the primary limiting, the command value of the negative sequence current obtained after the secondary limiting and the corresponding measured values ​​of the positive and negative sequence currents; The low voltage ride-through module is used to generate positive and negative sequence command values ​​based on the positive and negative sequence voltage reference values ​​by using coordinate system conversion, and control the power electronic equipment to complete low voltage ride-through according to the positive and negative sequence command values.

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