Converter reactive power allocation method and device, electronic equipment and converter system

Abstract

The application discloses a converter reactive power distribution method and device, electronic equipment and a converter system, and relates to the field of smart grids. The fault type of a fault causing bus voltage drop is determined according to the voltage variation of a point of common coupling, the effective value of a grid voltage and the variation of load reactive power. According to a reactive power compensation strategy corresponding to the fault type, a reactive power compensation value is determined. According to the reactive power compensation value and the maximum reactive capacity that a support valve can provide, the reactive power that the support valve and a main valve need to provide is determined. When voltage drop occurs at the point of common coupling, the cause of the drop can be quickly determined, and the reactive power provided by the support valve and the main valve is distributed according to the size of the required reactive compensation, so that the reactive demand of the grid is maximally met, the stability of the grid voltage is improved, and the limit support for the alternating current system is realized on the premise of guaranteeing the upper limit of the device capacity.

Description

Technical Field

[0001] This application relates to the field of smart grid technology, and in particular to a method, apparatus, electronic device and converter system for reactive power distribution in a converter. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) converters, as core equipment in UHVDC projects, determine power transmission efficiency and reliability. With the significant increase in the penetration rate of new energy sources and the widespread application of power electronic equipment, new power systems exhibit characteristics of high proportions of new energy and power electronics. In traditional power systems, synchronous generators can provide sufficient inertia and damping to maintain stable and reliable operation. However, in power systems with these dual high characteristics, the proportion of synchronous generators is relatively low, leading to low inertia and underdamping problems, and increasingly prominent issues related to voltage and frequency stability. Therefore, how to control the reactive power of the converter to improve its stability has become an urgent problem to be solved. Summary of the Invention

[0003] In view of the above problems, this application provides a method, apparatus, electronic equipment, and converter system for reactive power distribution in a converter, in order to improve grid stability. The specific solution is as follows:

[0004] The first aspect of this application provides a reactive power distribution method for a converter, applied to a converter including a main valve and a support valve. The main valve is composed of multiple bridge arms, each of which is composed of at least one IGCT device connected in series. The support valve is composed of multiple full-bridge sub-modules, each of which is a full-bridge circuit composed of IGCT devices. The method includes:

[0005] In the event of a bus voltage drop, the fault type causing the bus voltage drop is determined based on the voltage change at the point of common coupling, the effective value of the grid voltage, and the change in the reactive power of the load.

[0006] The reactive power compensation value is determined based on the reactive power compensation strategy corresponding to the fault type.

[0007] Based on the reactive power compensation value and the target reactive power capacity, the reactive power required to be provided by the support valve and the main valve is determined, where the target reactive power capacity is the maximum reactive power capacity provided by the support valve.

[0008] In one possible implementation, if the bus voltage does not drop, it further includes:

[0009] If no grid-side scheduling instruction is received, the support valve is controlled to maintain unity power factor operation;

[0010] Upon receiving the network-side scheduling instruction, the power reference values ​​of the support valve and the main valve are set to the corresponding scheduling setpoints.

[0011] In one possible implementation, determining the fault type causing the bus voltage drop based on the voltage variation at the common coupling point, the effective value of the grid voltage, and the variation of the load reactive power includes:

[0012] If the voltage drop rate at the common coupling point is not less than the rate threshold and the effective value of the grid voltage is lower than the voltage limit, then the fault type is determined to be a three-phase symmetrical voltage drop fault.

[0013] If the voltage drop rate at the common coupling point is not less than the rate threshold, the effective value of the grid voltage is not lower than the voltage limit, and the rate of change of the reactive power of the load is not less than the change threshold, then the fault type of the fault is determined to be an inductive load connection fault.

[0014] In one possible implementation, in the event of the bus voltage drop, the following is also included:

[0015] If the voltage sag rate at the common coupling point is less than the rate threshold, and the effective value of the grid voltage is not lower than the voltage limit; or,

[0016] If the voltage drop rate at the common coupling point is less than the rate threshold and the reactive power change of the load is 0, then the support valve is controlled to maintain unity power factor operation.

[0017] In one possible implementation, when the fault type is a three-phase symmetrical drop fault, determining the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes:

[0018] The reactive power compensation value is determined based on the grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the grid impedance, and the grid inductive reactance.

[0019] In one possible implementation, when the fault type is an inductive load connection fault, determining the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes:

[0020] Based on the power conservation relationship at the time of the inductive load connection fault and the actual value of reactive power injected into the grid at the time of the fault, the change value of reactive power after the load connection is determined.

[0021] The reactive power compensation value is determined based on the reactive power change value and the total reactive power compensation value of the power grid. The total reactive power compensation value of the power grid is determined based on the power grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the power grid impedance, and the power grid inductive reactance.

[0022] In one possible implementation, determining the reactive power required to be provided by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity includes:

[0023] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve has not reached the maximum apparent power, determine the first reactive power required by the main valve in the negative firing angle mode, and the second reactive power required by the support valve. The second reactive power is the difference between the reactive power compensation value and the first reactive power.

[0024] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve reaches the maximum apparent power, the support valve provides the target reactive power capacity, and the third reactive power required by the main valve is determined based on the difference between the reactive power compensation value and the target reactive power capacity.

[0025] In one possible implementation, determining the reactive power required to be provided by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity further includes:

[0026] In the case where the fault type is a three-phase symmetrical drop fault, if the reactive power compensation value is less than the target reactive power capacity, the reactive power required by the support valve is determined based on the reactive power compensation value and the reactive power required by the main valve.

[0027] If the fault type is an inductive load connection fault, and the reactive power compensation value is less than the target reactive power capacity, then the reactive power compensation value is determined as the reactive power required to be provided by the support valve.

[0028] A second aspect of this application provides a converter reactive power distribution device, comprising:

[0029] The fault type determination module is used to determine the fault type that caused the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in the reactive power of the load.

[0030] The compensation value determination module is used to determine the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type; and,

[0031] The compensation value allocation module is used to determine the reactive power required to be provided by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity, wherein the target reactive power capacity is the maximum reactive power capacity provided by the support valve.

[0032] A third aspect of this application provides a computer program product including computer-readable instructions that, when executed on an electronic device, cause the electronic device to implement the converter reactive power distribution method described in the first aspect or any implementation thereof.

[0033] A fourth aspect of this application provides an electronic device, including at least one processor and a memory connected to the processor, wherein:

[0034] The memory is used to store computer programs;

[0035] The processor is used to execute the computer program so that the electronic device can implement the converter reactive power distribution method of the first aspect or any implementation thereof.

[0036] The fifth aspect of this application provides a computer storage medium carrying one or more computer programs, which, when executed by an electronic device, enable the electronic device to implement the converter reactive power distribution method described in the first aspect or any implementation thereof.

[0037] The sixth aspect of this application provides a converter system, including: a converter and a power distribution device;

[0038] The power distribution device is connected to the main valve and the support valve of the converter respectively, and the power distribution device is used to perform the various steps of the converter reactive power distribution method as in the first aspect or any implementation thereof.

[0039] By employing the above technical solution, the converter reactive power allocation method provided in this application determines the fault type causing the bus voltage drop by considering the voltage change at the common coupling point, the effective value of the grid voltage, and the change in load reactive power. Based on the reactive power compensation strategy corresponding to this fault type, a reactive power compensation value is determined. Based on this reactive power compensation value and the maximum reactive power capacity that the support valve can provide, the required reactive power to be provided by the support valve and the main valve is determined. This enables rapid identification of the cause of a voltage drop at the common coupling point and allocation of the reactive power provided by the support valve and the main valve according to the required reactive power compensation, thereby maximizing the satisfaction of the grid's reactive power demand, improving grid voltage stability, and achieving maximum support for the AC system while ensuring the upper limit of the device capacity. Attached Figure Description

[0040] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0041] Figure 1 A flowchart of a converter reactive power distribution method provided in this application;

[0042] Figure 2 An architecture diagram of a converter is provided in this application;

[0043] Figure 3 A flowchart illustrating the specific application of a converter reactive power allocation method provided in this application;

[0044] Figure 4 A structural diagram of a converter reactive power distribution device provided in this application;

[0045] Figure 5 This is a structural diagram of an electronic device provided in this application. Detailed Implementation

[0046] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0047] The embodiments of this application will now be described with reference to the accompanying drawings. Those skilled in the art will recognize that, with technological advancements and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are equally applicable to similar technical problems.

[0048] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0049] Current hybrid converters already possess grid-connecting capabilities, simulating synchronous generators to provide inertia and damping for the power system. This allows them to participate in grid voltage and frequency regulation, enabling widespread application in future power systems. However, the current reactive power control strategy for this type of converter is relatively simple, aiming to maintain unit power operation under all operating conditions. This control method can easily lead to excessive reactive current output from the support valve under certain harsh conditions, even resulting in overload.

[0050] To address the aforementioned problems, this application provides a reactive power allocation method for a converter. The reactive power allocation method for a converter according to this application will be described in detail below with reference to the accompanying drawings.

[0051] Reference Figure 1 , Figure 1 A flowchart illustrating a converter reactive power distribution method provided in this application embodiment is shown below. Figure 1 As shown in the embodiment of this application, a converter reactive power distribution method may include steps 101 to 103, which are described in detail below.

[0052] This converter reactive power distribution method can be applied to converters that include a main valve and a support valve. The main valve consists of multiple bridge arms, each of which is composed of at least one IGCT device connected in series. The support valve consists of multiple full-bridge sub-modules, each of which is a full-bridge circuit composed of IGCT devices.

[0053] Specifically, refer to Figure 2 The diagram shows the structure of a converter, where the support valve and the main valve constitute a composite converter with both voltage and current source characteristics. (Refer to...) Figure 2 As shown on the left, the main valve is an RB-IGCT (reverse-resistance IGCT) board composed of a three-phase, six-bridge-arm IGCT (Integrated Gate-Commutated Thyristor) direct-flow valve. (Refer to...) Figure 2 The structure of the support valve shown on the lower right side is composed of a three-phase full-bridge sub-module, where each full-bridge sub-module (i.e., SM) consists of a capacitor, an IGBT (Insulated Gate Bipolar Transistor), and a diode.

[0054] It is understood that those skilled in the art can make corresponding adjustments to the structure of the main valve and support valve in the above-mentioned converter as needed, and no restrictions are imposed here.

[0055] The reactive power allocation method for this converter may include the following processes:

[0056] 101. In the event of a bus voltage drop, determine the fault type causing the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in the reactive power of the load.

[0057] Specifically, there are various reasons for bus voltage dips, such as AC faults and load changes. These situations necessitate the converter to provide reactive power support to the grid. The voltage dip at the point of common coupling (PCC) can be identified by first monitoring the rate of voltage change at PCC. Further analysis of the cause is then required. By detecting the effective value of the grid voltage, it can be determined that the PCC voltage dip is caused by a three-phase symmetrical voltage drop. Then, by assessing sudden changes in the grid load reactive power, it can be determined whether an inductive reactive load has been connected, thus determining whether the voltage dip is caused by an inductive load connection fault or by grid voltage fluctuations.

[0058] The voltage changes at the common coupling point can be instantaneously acquired using a voltage transformer, with a sampling frequency typically between 10kHz and 20kHz (i.e., 200 to 400 sampling points per cycle). Then, a coordinate transformation (e.g., Clark transform + Park transform) is used to convert the voltage in the three-phase stationary coordinate system into components in a two-phase rotating coordinate system (dq axis), and the d-axis voltage component is extracted as a representation of the voltage amplitude. The voltage changes are then calculated based on the sampling interval. To improve anti-interference capability, a moving average filtering method can be used to calculate the rate of change of the voltage value, avoiding misjudgments caused by noise.

[0059] Similarly, the effective value of the grid voltage can be determined by calculating the root mean square value over one power frequency cycle from the sampled instantaneous voltage value, and then calculating the mean value in a sliding window.

[0060] The reactive power of the load can be determined based on the power conservation relationship of the circuit at the point of common coupling. Specifically, the reactive power injected into the point of common coupling by the support valve is added to the reactive power absorbed by the main valve to obtain a sum. Then, the actual reactive power injected into the grid at the point of common coupling is subtracted from the sum to obtain the reactive power of the load. Based on this, the rate of change and other variations over time are determined.

[0061] 102. Determine the reactive power compensation value based on the reactive power compensation strategy corresponding to the fault type.

[0062] Specifically, based on the identified fault types causing voltage drops at the point of common coupling (PCC), the required reactive power injection into the grid is determined according to the corresponding reactive power compensation strategy. Timely injection of reactive power into the grid raises the PCC voltage, preventing further voltage drops and improving grid stability.

[0063] 103. Based on the reactive power compensation value and the target reactive power capacity, determine the reactive power required to be provided by the support valve and the main valve. The target reactive power capacity is the maximum reactive power capacity provided by the support valve.

[0064] Specifically, in the process of injecting reactive power into the grid through the common coupling point, considering the capacity constraints of reactive power of the main valve and the support valve, the reactive power can be provided by the support valve first. When the capacity of the support valve reaches the upper limit, the reactive power is switched to the main valve. When the main valve reaches the maximum apparent power and still cannot meet the reactive power demand of the grid side, the reactive power support demand is further met by reducing the active power of the converter.

[0065] According to the definition of apparent power: Apparent power squared = Active power squared + Reactive power squared. Since the main valve is a three-phase, six-arm IGCT direct-flow valve, the maximum apparent power of the main valve is usually determined based on the relevant design parameters during the converter design process.

[0066] The rated apparent power S can be determined based on the rated active power P of the main valve (which can be designed according to the converter capacity, such as 50MW) and the rated power factor φ of the main valve (generally taken as 0.9-1.0, absorbing reactive power during rectification operation). The result is: S≈P / φ. In practical applications, the rated apparent power needs to be appropriately amplified to obtain the maximum apparent power, for example, by amplifying it by 1.2-1.5 times. Those skilled in the art can adjust this as needed, and it will not be elaborated further here.

[0067] It is understood that those skilled in the art may use other allocation methods to allocate reactive power, and no restrictions are imposed here.

[0068] This converter reactive power allocation method quickly analyzes the cause of voltage drops at the common coupling point. Based on this analysis, it determines the reactive power compensation value required to compensate the grid. Then, it compares the required reactive power compensation value with the maximum reactive power capacity of the support valve to allocate reactive power. This achieves maximum support for the AC system while ensuring the upper limit of capacity, thereby significantly improving the voltage stability of the AC system.

[0069] To further improve this technical solution and enhance the adaptability of power grid stability regulation, in another embodiment, when the bus voltage does not drop, the following processing steps may also be included:

[0070] If no grid-side dispatch instruction is received, the control support valve will maintain unity power factor operation.

[0071] If a grid-side dispatch instruction is received, the power reference values ​​of the support valve and the main valve are set to the corresponding dispatch given values.

[0072] Specifically, the converter initially operates in unity power factor mode, with the main valve delivering rated active power. At this time, the support valve does not participate in active power exchange. The support valve will balance the reactive load of the main valve and the reactive power demand of the power grid to maintain unity power factor operation.

[0073] When the grid-side dispatch command is issued, the converter will switch to dispatch mode. The power reference values ​​of the main valve and the support valve are controlled by the dispatch command. The corresponding power is set according to the dispatch command, for example, as shown in formula (1):

[0074] (1);

[0075] Among them, Q svg_ref P is the power reference value for supporting the valve. csc_ref Q is the power reference value for the main valve. svg_set P is the power dispatch setpoint for supporting the valve. csc_set This is the power dispatch setpoint for the main valve. Both the power reference value and the power dispatch setpoint here include reactive power and active power; that is, the reactive power and active power of both the support valve and the main valve are set accordingly based on the dispatch instructions.

[0076] In another embodiment, to improve the accuracy of fault type determination, step 101 above determines the fault type causing the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in load reactive power. This may specifically include:

[0077] If the voltage drop rate at the common coupling point is not less than the rate threshold and the effective value of the grid voltage is lower than the voltage limit, then the fault type is determined to be a three-phase symmetrical drop fault.

[0078] If the voltage drop rate at the common coupling point is not less than the rate threshold, the effective value of the grid voltage is not lower than the voltage limit, and the rate of change of the reactive power of the load is not less than the change threshold, then the fault type is determined to be an inductive load connection fault.

[0079] Specifically, considering that the rate of voltage change is generally negative in the event of a voltage drop, a rate threshold of -v can be defined. pcc When the rate of change of voltage is less than -V pcc This indicates a voltage drop at the point of common coupling, requiring further investigation to determine the cause. If the effective value of the grid voltage is detected to be less than the minimum voltage limit U... gmin It can be determined that the voltage drop at the point of common coupling is caused by a three-phase symmetrical voltage drop in the grid; if the effective value of the grid voltage is greater than the minimum limit U... gmin This indicates that the voltage drop at the point of common coupling (PCC) is caused by a sudden change in load or fluctuations in grid voltage. It is necessary to check whether the load reactive power changes abruptly. If the load reactive power changes abruptly, it indicates that an inductive reactive load is connected; otherwise, it can be determined that the PCC voltage drop is caused by grid voltage fluctuations.

[0080] Among them, the rate threshold serves as a criterion for judging the difference between normal voltage fluctuations and voltage drops requiring the activation of reactive power support. Its value in converter scenarios is generally 0.5-0.8% / s, and the voltage limit is usually not less than 90% of the grid's effective value. Those skilled in the art can select and adjust it according to different application scenarios, which will not be elaborated here.

[0081] Furthermore, based on the above embodiments, after the power grid is compensated for reactive power through the support valve and the main valve, the voltage at the common coupling point tends to stabilize. At this time, if the voltage drop rate at the common coupling point is less than the rate threshold, and the effective value of the grid voltage is not lower than the voltage limit; or,

[0082] If the voltage drop rate at the common coupling point is less than the rate threshold and the load reactive power change is 0, then the control support valve will maintain unity power factor operation.

[0083] Specifically, if the rate of change of the voltage at the common coupling point is detected to be greater than the threshold v pcc At the same time, when the grid voltage is greater than the minimum limit, it is judged that the grid voltage has recovered, and the converter switches to unity power factor mode.

[0084] If the rate of change of voltage at the common coupling point is detected to be greater than the threshold v pcc If the reactive power of the load becomes 0, it is determined that the load is completely disconnected and the parallel system switches to unity power factor mode.

[0085] As a specific implementation method for the above-mentioned reactive power compensation value, when the fault type is a three-phase symmetrical drop fault, the reactive power compensation value is determined according to the reactive power compensation strategy corresponding to the fault type, which may specifically include:

[0086] The reactive power compensation value is determined based on the grid voltage, power angle, voltage recovery value at the common coupling point, grid impedance, and grid reactance after the voltage drop.

[0087] The voltage recovery values ​​of the grid voltage after the drop and the voltage at the common coupling point can be obtained by converting the high voltage of the bus or the common coupling point into a standard low voltage signal through a voltage transformer, and then the signal is processed by analog-to-digital conversion to obtain the accurate grid voltage.

[0088] The power angle can be obtained by subtracting the phase of the internal potential of the power generation equipment from the phase of the grid bus voltage. The phase of the internal potential of the power generation equipment can be obtained by measuring the rotor angle through a position sensor installed on the power generation equipment.

[0089] The grid impedance can be obtained using online impedance estimation methods. This involves injecting a non-characteristic subharmonic disturbance of a specific frequency into the grid and measuring the response voltage and current at the point of common coupling to calculate the impedance. Similarly, the grid inductive reactance can be obtained by injecting a specific disturbance signal (such as a sinusoidal current signal) into the grid, detecting the system response (voltage and current at a specific frequency) at the point of common coupling, and then solving the problem using methods such as Fast Fourier Transform.

[0090] It is understood that those skilled in the art can also use other technical means to obtain the above-mentioned grid voltage, power angle, voltage recovery value of common coupling point, grid impedance and grid inductive reactance, and no restrictions are imposed here.

[0091] Specifically, let the grid voltage after the drop be U. gF The work angle is δ F After a voltage drop in the mains grid, the goal is to restore the voltage at the point of common coupling to a set value (i.e., the voltage recovery value) U. pcc_ref Then, a total reactive power compensation amount Q needs to be injected into the power grid through the common coupling point. total As shown in the following formula:

[0092] (2);

[0093] in, Indicates the impedance in the power grid. This represents the inductive reactance in the power grid.

[0094] The corresponding reactive power distribution of the support valve and the main valve can specifically include:

[0095] If the reactive power compensation value is less than the target reactive power capacity, the control support valve provides the reactive power compensation value and the reactive power required by the main valve.

[0096] Specifically, the key to coordinated reactive power control between the main valve and the supporting valve lies in allocating their respective reactive power command values. Therefore, as long as the reactive load Q of the main valve is clearly defined...csc Then, the reactive power command value Q of the supporting valve can be calculated by equation (3). svg_ref :

[0097] (3);

[0098] When the fault is minor, the capacity of the support valve alone is sufficient to meet the reactive power demand of the grid side. In this case, the power distribution expression between the main valve and the support valve is as follows:

[0099] (4);

[0100] in, This indicates that the main valve absorbs reactive power in the positive firing angle operation mode. Under this condition, in addition to providing reactive power to the grid side, the support valve also needs to compensate for the reactive load of the main valve.

[0101] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve has not reached the maximum apparent power, the main valve is controlled to operate in negative trigger angle mode to provide the first reactive power, and the support valve is controlled to provide the second reactive power. The second reactive power is the difference between the reactive power compensation value and the first reactive power.

[0102] Specifically, in cases of severe faults, the capacity of the support valve alone is insufficient to meet the reactive power demand of the grid side, requiring the main valve to provide some reactive power. The power distribution expression between the main valve and the support valve in this situation is as follows:

[0103] (5);

[0104] in, This indicates that the IGCT active shut-off characteristic is used to enable the main valve to operate in negative firing angle mode, thereby providing reactive power.

[0105] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve reaches the maximum apparent power, the support valve provides the target reactive power capacity, and the main valve is controlled to reduce the active power to provide the third reactive power. The third reactive power is the difference between the reactive power compensation value and the target reactive power capacity.

[0106] Specifically, in cases of severe faulting, the capacity of the supporting valve alone is insufficient to meet the reactive power demand of the grid side, while the main valve, having reached its maximum apparent power, still cannot meet the grid side's reactive power demand. In this situation, the power distribution expression between the main valve and the supporting valve is as follows:

[0107] (6);

[0108] Among them, S csc_max The apparent power of the main valve, Q maxThis indicates the maximum reactive power capacity of the supporting valve. Under this operating condition, the converter will be unable to inject rated active power into the grid. At this time, the main valve reduces the reactive power load of the main valve by reducing active power transmission, thereby achieving maximum support for the reactive power on the grid side.

[0109] In some embodiments, when the fault type is an inductive load connection fault, the reactive power compensation value is determined according to the reactive power compensation strategy corresponding to the fault type, which may specifically include:

[0110] Based on the power conservation relationship at the moment of the inductive load connection fault and the actual value of reactive power injected into the grid at the moment of the fault, the change value of reactive power after the load connection is determined.

[0111] The reactive power compensation value is determined based on the reactive power change value and the total reactive power compensation value of the power grid. The total reactive power compensation value of the power grid is determined based on the grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the grid impedance, and the grid inductive reactance.

[0112] Specifically, when the reactive load connected to the point of common coupling changes, the converter power reference value needs to be calculated and determined based on the actual situation. As the reactive load connected to the point of common coupling increases, the voltage at the bus of the point of common coupling will drop, and the depth of the drop increases with the increase in inductive load. To prevent the risk of system instability caused by large-amplitude connections, the converter needs to inject reactive power into the point of common coupling in a timely manner to raise the voltage at the point of common coupling, thereby improving the stability of the parallel system.

[0113] Let the power angle after the load change be δ load To support the PCC point voltage to the set value U pcc_ref Then, the PCC point needs to inject a total reactive power compensation amount Q into the power grid. total As shown in the following formula, where U gN This is the effective value of the rated voltage of the power grid.

[0114] (7);

[0115] To determine the reactive power Q of the load load The power distribution between the main valve and the support valve can be achieved based on the measurement and calculation of instantaneous values.

[0116] When a sudden load change occurs in the system, recorded as time k, the following equation can be obtained from the power conservation relationship:

[0117] (8);

[0118] in, Let k be the reactive power supporting the valve. Let Q be the reactive power of the main valve at time k. load Q represents the change in reactive power when a load is connected. g_k The actual reactive power injected into the power grid at the common coupling point at time k is calculated as follows:

[0119] (9);

[0120] Where, δ k Let U be the angle of attack at time k. gk Let be the bus voltage at time k. This is the voltage recovery value at the corresponding common coupling point.

[0121] From equations (9) and (8) above, the reactive power change value Q under the connected load condition can be obtained. load Combined with the reactive power compensation Q that needs to be injected into the grid after load changes total The total reactive power compensation value Q* to be allocated can be expressed as follows:

[0122] (10);

[0123] After determining the reactive power compensation value Q* required by the power grid to be allocated, the reactive power can be allocated according to the following process:

[0124] If the reactive power compensation value is less than the target reactive power capacity, then only the support valve is controlled to provide the reactive power compensation value.

[0125] Specifically, the capacity of the support valve alone is sufficient to meet the reactive power demand caused by changes in grid-side load. In this case, the support valve undertakes the reactive power compensation task, and the power distribution between the main valve and the support valve is shown in the following formula:

[0126] (11);

[0127] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve has not reached the maximum apparent power, the main valve is controlled to operate in negative trigger angle mode to provide the first reactive power, and the support valve is controlled to provide the second reactive power. The second reactive power is the difference between the reactive power compensation value and the first reactive power.

[0128] Specifically, the capacity of the support valve alone is insufficient to meet the reactive power demand generated by changes in grid-side load; therefore, the main valve needs to provide partial reactive power support. In this case, the power distribution between the main valve and the support valve is as follows:

[0129] (12);

[0130] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve reaches the maximum apparent power, the support valve provides the target reactive power capacity, and the main valve is controlled to reduce the active power to provide a third reactive power, which is the difference between the reactive power compensation value and the target reactive power capacity.

[0131] Specifically, if the capacity of the support valve alone is insufficient to meet the reactive power demand generated by changes in grid-side load, the main valve needs to reduce its active power to achieve maximum reactive power support. In this case, the power distribution between the main valve and the support valve is as follows:

[0132] (13);

[0133] As a specific application of the above-mentioned converter reactive power distribution method, refer to Figure 3 As shown, the following processing procedures may be included:

[0134] After startup, the converter initially operates in unity power factor mode. The main valve outputs rated active power, and the support valve does not participate in active power exchange. The support valve will balance the reactive load of the main valve and the reactive power demand of the grid to maintain unity power factor operation (i.e., the converter operates in unity power factor mode).

[0135] When the grid-side dispatch command is issued, the converter will switch to dispatch mode. The power reference values ​​of the main valve and the support valve are controlled by the dispatch command, and the corresponding power is issued according to the dispatch command value.

[0136] If the effective value of the mains voltage is detected to be less than the minimum limit U gmin It can be determined that the voltage drop at the point of common coupling is caused by a three-phase symmetrical voltage drop in the grid; if the effective value of the grid voltage is greater than the minimum limit U... gmin This indicates that the voltage drop at the point of common coupling (PCC) is caused by a sudden change in load or fluctuations in grid voltage. It is necessary to check whether the load reactive power changes abruptly. If the load reactive power changes abruptly, it indicates that an inductive reactive load is connected; otherwise, it can be determined that the PCC voltage drop is caused by grid voltage fluctuations.

[0137] When it is identified that the voltage drop at the point of common coupling (PCC) is caused by a three-phase symmetrical voltage drop in the grid, the converter's reactive power distribution method is as follows: First, calculate the total reactive power compensation Q that needs to be injected into the grid at the PCC. total Secondly, according to Q total With Q max Based on the magnitude relationship and whether the output of the main valve reaches the maximum apparent power, reactive power allocation is performed according to the reactive power allocation method expressed by equation (4), (5), or (6). If the rate of change of the common coupling point voltage is detected to be greater than the threshold v pccSimultaneously, when the grid voltage is greater than the minimum limit, it is determined that the grid voltage has recovered, and the converter switches to unity power factor mode.

[0138] When the load reactive power Q total When a sudden change occurs, it can be determined that the voltage drop at the point of common coupling is caused by the connection of an inductive reactive load. The total reactive power value Q of the added load is then calculated. load Calculate the total reactive power compensation value Q* to be allocated; then, based on Q* and Q... max Based on the magnitude relationship and whether the output of the main valve reaches the maximum apparent power, the reactive power distribution is performed according to the reactive power distribution method expressed by equation (11), (12), or (13), with the support valve and the main valve providing reactive power support. If the voltage change rate at the PCC point is detected to be greater than the threshold v, pcc At the same time Q load If the value is 0, it indicates that the load has been completely disconnected, and the parallel system switches to unity power factor mode.

[0139] If it is determined that the voltage drop at the point of common coupling is caused by grid voltage fluctuations, reactive power can still be adjusted according to the unity power factor mode.

[0140] The above describes a converter reactive power allocation method provided by the embodiments of this application. The following will describe the apparatus for performing the above converter reactive power allocation method.

[0141] Please see Figure 4 , Figure 4 This is a schematic diagram of a converter reactive power distribution device provided in an embodiment of this application. Figure 4 As shown, the reactive power distribution device of the converter includes:

[0142] The fault type determination module 401 is used to determine the fault type that causes the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in the reactive power of the load when the bus voltage drops.

[0143] The compensation value determination module 402 is used to determine the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type; and,

[0144] The compensation value allocation module 403 is used to determine the reactive power required by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity. The target reactive power capacity is the maximum reactive power capacity provided by the support valve.

[0145] In one possible implementation, it also includes: a power control module for use when the bus voltage does not drop:

[0146] If no grid-side dispatching command is received, the control support valve will maintain unity power factor operation;

[0147] Upon receiving a grid-side dispatch instruction, the power reference values ​​for the support valve and the main valve are set to the corresponding dispatch given values.

[0148] In one possible implementation, the fault type determination module 401 determines the fault type causing the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in load reactive power. This process includes:

[0149] If the voltage drop rate at the common coupling point is not less than the rate threshold and the effective value of the grid voltage is lower than the voltage limit, then the fault type is determined to be a three-phase symmetrical drop fault.

[0150] If the voltage drop rate at the common coupling point is not less than the rate threshold, the effective value of the grid voltage is not lower than the voltage limit, and the rate of change of the reactive power of the load is not less than the change threshold, then the fault type is determined to be an inductive load connection fault.

[0151] In one possible implementation, the power control module is also used for:

[0152] If the voltage sag rate at the point of common coupling is less than the rate threshold, and the effective value of the grid voltage is not lower than the voltage limit; or,

[0153] If the voltage drop rate at the common coupling point is less than the rate threshold and the load reactive power change is 0, then the control support valve will maintain unity power factor operation.

[0154] In one possible implementation, when the fault type is a three-phase symmetrical drop fault, the process by which the compensation value determination module 402 determines the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes:

[0155] The reactive power compensation value is determined based on the grid voltage, power angle, voltage recovery value at the common coupling point, grid impedance, and grid reactance after the voltage drop.

[0156] In one possible implementation, when the fault type is an inductive load connection fault, the process by which the compensation value determination module 402 determines the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes:

[0157] Based on the power conservation relationship at the moment of the inductive load connection fault and the actual value of reactive power injected into the grid at the moment of the fault, the change value of reactive power after the load connection is determined.

[0158] The reactive power compensation value is determined based on the reactive power change value and the total reactive power compensation value of the power grid. The total reactive power compensation value of the power grid is determined based on the grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the grid impedance, and the grid inductive reactance.

[0159] In one possible implementation, the compensation value allocation module 403 determines the reactive power required by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity, including:

[0160] If the reactive power compensation value is greater than the target reactive power capacity and the main valve has not reached the maximum apparent power, determine the first reactive power required by the main valve in the negative firing angle mode and the second reactive power required by the support valve. The second reactive power is the difference between the reactive power compensation value and the first reactive power.

[0161] If the reactive power compensation value is greater than the target reactive power capacity, and the main valve reaches the maximum apparent power, the support valve provides the target reactive power capacity, and the third reactive power required by the main valve is determined based on the difference between the reactive power compensation value and the target reactive power capacity.

[0162] In one possible implementation, the compensation value allocation module 403 is also used to determine the reactive power required by the support valve based on the reactive power compensation value and the reactive power required by the main valve when the fault type is a three-phase symmetrical drop fault.

[0163] If the fault type is an inductive load connection fault, and the reactive power compensation value is less than the target reactive power capacity, then the reactive power compensation value is determined as the reactive power required to be provided by the support valve.

[0164] This application also provides an electronic device in its embodiments. (See reference...) Figure 5 The diagram illustrates a structural schematic suitable for implementing the electronic device in the embodiments of this application. The electronic device in the embodiments of this application may include, but is not limited to, fixed terminals such as laptops, desktop computers, etc. Figure 5 The electronic device shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0165] like Figure 5As shown, the electronic device may include a processing unit (e.g., a central processing unit, a graphics processing unit, etc.) 501, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 502 or a program loaded from a storage device 508 into a random access memory (RAM) 503. When the electronic device is powered on, the RAM 503 also stores various programs and data required for the operation of the electronic device. The processing unit 501, ROM 502, and RAM 503 are interconnected via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0166] Typically, the following devices can be connected to I / O interface 505: input devices 506 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 507 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 508 including, for example, memory cards, hard drives, etc.; and communication devices 509. Communication device 509 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 5 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown. More or fewer devices may be implemented or have alternatively.

[0167] This application also provides a computer program product including computer-readable instructions, which, when executed on an electronic device, cause the electronic device to implement any of the converter reactive power distribution methods provided in this application.

[0168] This application also provides a computer-readable storage medium carrying one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement any of the converter reactive power distribution methods provided in this application.

[0169] This application also provides a converter system, including: a converter and a power distribution device as described in the above embodiments;

[0170] The power distribution device is connected to the main valve and the support valve of the converter respectively. The power distribution device is used to perform each step of the converter reactive power distribution method in the above embodiment.

[0171] The power distribution device may include the aforementioned electronic devices and other control devices, which are not limited herein.

[0172] It should also be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. In addition, in the device embodiment drawings provided in this application, the connection relationship between modules indicates that they have a communication connection, which can be implemented as one or more communication buses or signal lines.

[0173] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware, or it can be implemented by special-purpose hardware including application-specific integrated circuits, special-purpose CPUs, special-purpose memory, special-purpose components, etc. Generally, any function performed by a computer program can be easily implemented by corresponding hardware, and the specific hardware structure used to implement the same function can also be diverse, such as analog circuits, digital circuits, or special-purpose circuits. However, for this application, software program implementation is more often the preferred implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a readable storage medium, such as a computer floppy disk, USB flash drive, mobile hard disk, ROM, RAM, magnetic disk, or optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, training equipment, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0174] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product.

[0175] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, training device, or data center to another website, computer, training device, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a training device or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives (SSDs)).

Claims

1. A reactive power distribution method for a converter, applied to a converter including a main valve and a support valve, wherein the main valve is composed of multiple bridge arms, each bridge arm being composed of at least one IGCT device connected in series; the support valve is composed of multiple full-bridge sub-modules, each full-bridge sub-module being a full-bridge structure circuit composed of IGCT devices; characterized in that, include: In the event of a bus voltage drop, the fault type causing the bus voltage drop is determined based on the voltage change at the point of common coupling, the effective value of the grid voltage, and the change in the reactive power of the load. The reactive power compensation value is determined based on the reactive power compensation strategy corresponding to the fault type. Based on the reactive power compensation value and the target reactive power capacity, the reactive power required to be provided by the support valve and the main valve is determined, where the target reactive power capacity is the maximum reactive power capacity provided by the support valve.

2. The converter reactive power distribution method according to claim 1, characterized in that, If the bus voltage does not drop, the following is also included: If no grid-side scheduling instruction is received, the support valve is controlled to maintain unity power factor operation; Upon receiving the network-side scheduling instruction, the power reference values ​​of the support valve and the main valve are set to the corresponding scheduling setpoints.

3. The converter reactive power distribution method according to claim 1, characterized in that, The fault type causing the bus voltage drop is determined based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in load reactive power, including: If the voltage drop rate at the common coupling point is not less than the rate threshold and the effective value of the grid voltage is lower than the voltage limit, then the fault type is determined to be a three-phase symmetrical voltage drop fault. If the voltage drop rate at the common coupling point is not less than the rate threshold, the effective value of the grid voltage is not lower than the voltage limit, and the rate of change of the reactive power of the load is not less than the change threshold, then the fault type of the fault is determined to be an inductive load connection fault.

4. The converter reactive power distribution method according to claim 3, characterized in that, In the event of a bus voltage drop, the method further includes: If the voltage sag rate at the common coupling point is less than the rate threshold, and the effective value of the grid voltage is not lower than the voltage limit; or, If the voltage drop rate at the common coupling point is less than the rate threshold and the reactive power change of the load is 0, then the support valve is controlled to maintain unity power factor operation.

5. The converter reactive power distribution method according to claim 3, characterized in that, When the fault type is a three-phase symmetrical drop fault, determining the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes: The reactive power compensation value is determined based on the grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the grid impedance, and the grid inductive reactance.

6. The converter reactive power distribution method according to claim 3, characterized in that, When the fault type is an inductive load connection fault, determining the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type includes: Based on the power conservation relationship at the time of the inductive load connection fault and the actual value of reactive power injected into the grid at the time of the fault, the change value of reactive power after the load connection is determined. The reactive power compensation value is determined based on the reactive power change value and the total reactive power compensation value of the power grid. The total reactive power compensation value of the power grid is determined based on the power grid voltage after the voltage drop, the power angle, the voltage recovery value of the common coupling point, the power grid impedance, and the power grid inductive reactance.

7. The converter reactive power distribution method according to any one of claims 3 to 6, characterized in that, The step of determining the reactive power required by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity includes: If the reactive power compensation value is greater than the target reactive power capacity, and the main valve has not reached the maximum apparent power, determine the first reactive power required by the main valve in the negative firing angle mode, and the second reactive power required by the support valve. The second reactive power is the difference between the reactive power compensation value and the first reactive power. If the reactive power compensation value is greater than the target reactive power capacity, and the main valve reaches the maximum apparent power, the support valve provides the target reactive power capacity, and the third reactive power required by the main valve is determined based on the difference between the reactive power compensation value and the target reactive power capacity.

8. The converter reactive power distribution method according to claim 7, characterized in that, The step of determining the reactive power required by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity further includes: In the case where the fault type is a three-phase symmetrical drop fault, if the reactive power compensation value is less than the target reactive power capacity, the reactive power required by the support valve is determined based on the reactive power compensation value and the reactive power required by the main valve. If the fault type is an inductive load connection fault, and the reactive power compensation value is less than the target reactive power capacity, then the reactive power compensation value is determined as the reactive power required to be provided by the support valve.

9. A reactive power distribution device for a converter, characterized in that, include: The fault type determination module is used to determine the fault type that caused the bus voltage drop based on the voltage change at the common coupling point, the effective value of the grid voltage, and the change in the reactive power of the load. The compensation value determination module is used to determine the reactive power compensation value according to the reactive power compensation strategy corresponding to the fault type; and, The compensation value allocation module is used to determine the reactive power required to be provided by the support valve and the main valve based on the reactive power compensation value and the target reactive power capacity, wherein the target reactive power capacity is the maximum reactive power capacity provided by the support valve.

10. An electronic device, characterized in that, It includes at least one processor and a memory connected to the processor, wherein: The memory is used to store computer programs; The processor is used to execute the computer program to enable the electronic device to implement the converter reactive power distribution method as described in any one of claims 1 to 8.

11. A converter system, characterized in that, include: Converters and power distribution devices; The power distribution device is connected to the main valve and the support valve of the converter respectively, and the power distribution device is used to perform each step of the converter reactive power distribution method as described in any one of claims 1 to 8.

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