A converter active voltage support control method, device, equipment and medium

Abstract

The application discloses a converter active voltage support control method and device, equipment and medium, and relates to the field of converter voltage control. The method comprises the following steps: calculating a short-circuit ratio based on a grid-connected point voltage and a grid-connected equivalent impedance, dynamically calculating upper and lower limit coefficients of a voltage band gap based on the short-circuit ratio; determining a voltage interval and performing voltage band gap determination based on the upper and lower limit coefficients of the voltage band gap and a set voltage component value, and determining upper and lower limit exceeding characteristic quantities; when the voltage interval is exceeded, generating a reactive power compensation amount based on the upper and lower limit exceeding characteristic quantities and a voltage deviation, thereby calculating a reactive power reference value; limiting the reactive power reference value by using a converter apparent capacity constraint; and obtaining a reactive power reference output value according to the limited reactive power reference value, the calculated reactive power and a direct current side voltage, so as to drive the converter to input a reactive current to the grid-connected point to realize voltage support. The application can improve the stability and operation reliability of system voltage.

Description

Technical Field

[0001] This application relates to the field of converter voltage control, and in particular to a converter active voltage support control method, device, equipment and medium. Background Technology

[0002] With the increasing proportion of new energy sources and power electronic equipment connected to the grid, the point of common coupling (PCC) voltage is more susceptible to fluctuations, rises, or drops due to changes in short-circuit capacity, line impedance, and operating conditions. Related technologies often employ an inner current loop combined with an outer AC voltage loop, reactive power droop, or STATCOM-type reactive current injection to achieve voltage regulation.

[0003] The aforementioned solutions can play a certain role when the grid strength is relatively stable. However, in scenarios with weak grids or increased equivalent impedance, the PCC voltage becomes significantly more sensitive to reactive power injection. It becomes difficult to balance rapid support and stability margin in terms of voltage outer-loop gain and threshold parameters: excessively large parameters can easily lead to reactive power command overshoot, secondary oscillations, PLL synchronization disturbance amplification, and current limiting coupling; excessively small parameters result in delayed intervention and prolonged voltage recovery time, failing to meet the requirements of grid connection regulations for dynamic reactive power support. Furthermore, while some solutions introduce voltage dead zones / bandgap to reduce steady-state reactive power oscillations, their upper and lower bandgap limits are usually fixed and fail to adaptively adjust with changes in the short-circuit ratio or fluctuations in the grid equivalent impedance, leading to inconsistent performance across operating conditions and even repeated adjustments and voltage swirl during the recovery phase after fault clearance. Simultaneously, converters (such as inverters) are constrained by rated apparent power, limiting their available reactive power capacity at high active power output. If reactive power reference generation lacks a constraint mechanism coordinated with the P / Q capacity boundaries, problems such as command unreachability, sudden limiting changes, and outer-loop saturation can easily occur.

[0004] Therefore, improving the stability of system voltage and operational reliability has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a converter active voltage support control method, device, equipment and medium, which can improve the stability of system voltage and operational reliability.

[0006] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a converter active voltage support control method, including: Obtain the grid connection point voltage and grid connection point current; Based on the phase-locked loop, the voltage and current at the grid connection point are transformed by dq coordinates to obtain voltage and current components, and reactive power is calculated based on the voltage and current components. A DC voltage control loop is used to generate an active current command based on the DC bus voltage deviation, and the DC side voltage is determined based on the active current command. The short-circuit ratio is calculated based on the grid connection point voltage and the grid equivalent impedance, and the upper limit coefficient and lower limit coefficient of the voltage bandgap are dynamically calculated based on the short-circuit ratio. The voltage range is determined based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and the set voltage component value. The voltage bandgap is then determined based on the voltage range to identify the upper limit exceedance value and the lower limit exceedance value. When the voltage component exceeds the voltage range, a reactive power compensation amount is generated based on the upper limit exceedance indicator, the lower limit exceedance indicator, and the voltage deviation. A reactive power reference value is calculated based on the reactive power compensation amount and the preset reactive power. The reactive power reference value is limited by the apparent capacity constraint of the converter to obtain the limited reactive power reference value. The reactive power reference output value is obtained based on the limited reactive power reference value, the reactive power, and the DC side voltage; the reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

[0007] In one embodiment, the formula for calculating the short-circuit ratio is: ; in, This represents the short-circuit ratio at time t; This represents the grid connection point voltage at time t; It represents the grid-connected equivalent impedance.

[0008] In one embodiment, dynamically calculating the upper and lower voltage bandgap coefficients based on the short-circuit ratio specifically includes: Determine whether to widen the bandwidth based on the short-circuit ratio; If so, the voltage amplitude coefficient correction value is calculated based on the adaptive adjustment step size and the grid strength weighting coefficient. Based on the voltage amplitude coefficient correction value, the initial upper limit coefficient of the AC phase voltage amplitude, and the initial lower limit coefficient of the AC phase voltage amplitude, the voltage bandgap upper limit coefficient and the voltage bandgap lower limit coefficient are calculated. If not, then the voltage amplitude coefficient correction value is set to 0, the initial upper limit coefficient of the AC phase voltage amplitude is set as the upper limit coefficient of the voltage bandgap, and the initial lower limit coefficient of the AC phase voltage amplitude is set as the lower limit coefficient of the voltage bandgap.

[0009] In one embodiment, the voltage range is expressed as: ; in, The upper limit coefficient of the voltage bandgap at time t; The lower limit coefficient of the voltage bandgap at time t; The set d-axis voltage component value; The expression for the upper limit exceeding the representation quantity is: ; The expression for the lower limit transcendence characteristic is: ; in, The upper limit exceeds the representation quantity; This is the lower limit of the transcendental quantity; This is the upper limit coefficient of the voltage bandgap; This is the lower limit coefficient of the voltage bandgap; This represents the d-axis voltage component value of the voltage component obtained after performing a dq coordinate transformation on the grid connection point voltage.

[0010] In one embodiment, the formula for calculating the reactive power compensation is: ; in, This refers to reactive power compensation. The upper limit exceeds the representation quantity; The gain when the AC phase voltage amplitude exceeds the upper limit; This is the upper limit coefficient of the voltage bandgap; The set d-axis voltage component value; This refers to the d-axis voltage component value in the voltage components obtained after performing a dq coordinate transformation on the grid connection point voltage; This is the lower limit of the transcendental quantity; The gain when the AC phase voltage amplitude exceeds the lower limit; This is the lower limit coefficient of the voltage bandgap.

[0011] In one embodiment, the reactive power reference value is limited using the apparent capacity constraint of the converter to obtain a limited reactive power reference value, specifically including: The limiting value is calculated based on the rated apparent power and the real-time active power of the converter; The apparent capacity constraint of the converter is determined based on the limiting value, so that the reactive power reference value is within the apparent capacity constraint of the converter, and the limiting reactive power reference value is obtained.

[0012] In one embodiment, determining whether to widen the bandwidth based on the short-circuit ratio specifically includes: When the short-circuit ratio is less than the set grid strength threshold, it is determined that the bandwidth needs to be widened; when the short-circuit ratio is greater than or equal to the set grid strength threshold, it is determined that the bandwidth does not need to be widened.

[0013] Secondly, this application provides a converter active voltage support control device, comprising: The grid connection parameter acquisition module is used to acquire the grid connection point voltage and grid connection point current. The reactive power calculation module is used to perform dq coordinate transformation on the grid connection point voltage and the grid connection point current based on the phase-locked loop to obtain voltage components and current components, and to calculate reactive power based on the voltage components and the current components. A DC voltage control module is used to generate an active current command based on the DC bus voltage deviation using a DC voltage control loop, and to determine the DC side voltage based on the active current command. The bandgap upper and lower limit coefficient calculation module is used to calculate the short-circuit ratio based on the grid connection point voltage and the grid equivalent impedance, and to dynamically calculate the voltage bandgap upper limit coefficient and voltage bandgap lower limit coefficient based on the short-circuit ratio. The exceedance characterization module is used to determine a voltage range based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and a set voltage component value, and to determine the voltage bandgap of the voltage component based on the voltage range, thereby determining the upper limit exceedance characterization and the lower limit exceedance characterization. The reactive power reference value calculation module is used to generate a reactive power compensation amount based on the upper limit exceedance indicator, the lower limit exceedance indicator and the voltage deviation when the voltage component exceeds the voltage range, and to calculate the reactive power reference value according to the reactive power compensation amount and the preset reactive power. The limiting module is used to limit the reactive power reference value using the apparent capacity constraint of the converter, so as to obtain the limited reactive power reference value. The voltage support control module is used to obtain a reactive power reference output value based on the limited reactive power reference value, the reactive power, and the DC side voltage; the reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

[0014] Thirdly, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the computer program to implement the converter active voltage support control method described in any one of the above.

[0015] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the converter active voltage support control method described above.

[0016] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a converter active voltage support control method, device, equipment, and medium. Based on the short-circuit ratio, it dynamically calculates the upper and lower limits of the voltage bandgap to determine the voltage range. This allows the control threshold to adaptively adjust with changes in system operating conditions such as the short-circuit ratio and grid equivalent impedance. Under strong grid conditions, it can intervene in voltage support more quickly; under weak grid conditions or with increased impedance, it can appropriately widen the bandgap and reduce the tendency for excessive reactive power action, thereby improving system stability margin and voltage recovery speed. In the reactive power reference value generation process, a "limit-triggered" reactive power compensation mechanism is adopted. Reactive power compensation is generated only when the voltage exceeds the voltage range, and this compensation is superimposed with a preset reactive power value to obtain the reactive power reference value. This avoids continuous reactive power fluctuations in the normal voltage range, reduces unnecessary reactive power regulation and losses, and improves voltage quality under steady-state operation. The apparent capacity constraint of the converter is used to limit the reactive power reference value, ensuring that reactive power commands are continuously available within the rated capacity and current capability range. This reduces the risk of control performance degradation due to sudden limit changes and improves feasibility and operational safety in engineering applications. It is evident that this application improves the system voltage recovery speed, stability, and operational reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating an active voltage support control method for a converter provided in an embodiment of this application; Figure 2 This is a block diagram of a converter control system provided in an embodiment of this application; Figure 3 This is a block diagram of active voltage-supported reactive power control provided in an embodiment of this application; Figure 4 This is a system topology diagram provided for testing and verification on PSCAD in an embodiment of this application; Figure 5 This is a control system structure diagram provided in the embodiments of this application for testing and verification on PSCAD; Figure 6 This is a diagram of the grid voltage waveform when a three-phase short-circuit grounding occurs without the use of an active voltage support strategy, as provided in an embodiment of this application. Figure 7 The grid voltage waveform diagram provided in this application embodiment shows the grid voltage waveform when a three-phase short circuit to ground occurs using an active voltage support strategy; Figure 8This is a voltage waveform diagram of a single-phase short-circuit ground fault grid without the active voltage support strategy provided in the embodiments of this application; Figure 9 The voltage waveform diagram of a single-phase short-circuit ground fault grid using an active voltage support strategy is provided in the embodiments of this application. Figure 10 The voltage waveform diagram provided in this application embodiment shows a slight voltage fluctuation. Figure 11 A result diagram of the strong system reactive power reference value provided in the embodiments of this application; Figure 12 A result diagram of the reactive power reference values ​​for a weak system provided in the embodiments of this application; Figure 13 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Based on the problems existing in related technologies, there is an urgent need for an active voltage support control scheme that can adaptively adjust the support threshold and support strength by combining the grid strength index and the change of grid-connected equivalent impedance, and coordinate with capacity constraints, so as to improve the voltage recovery speed and stability under different grid conditions.

[0022] With the rapid growth of power sources such as photovoltaics, wind power, and energy storage, as well as various flexible loads, the power grid exhibits characteristics such as decreased short-circuit capacity, increased equivalent impedance, and weakened inertia and damping. The voltage stability margin in localized areas tends to decrease, and the propagation and superposition effects of voltage disturbances become more pronounced. Under system-level events such as fault occurrence and clearance, line switching, and load fluctuations, the voltage at the grid connection point of the weakly supported receiving-end grid is prone to persistent deviations or repeated fluctuations during the recovery process. This can lead to a chain reaction of problems such as renewable energy curtailment, frequent protection actions, and reactive power resource crowding, affecting power supply reliability and system safety boundaries.

[0023] The relevant voltage support mainly relies on the voltage regulation capabilities of traditional synchronous power sources and the configuration of centralized reactive power compensation facilities. However, in scenarios with a high proportion of renewable energy, reactive power support is gradually shifting to the distributed grid-connected converter side, and the control strategy is changing from centralized voltage regulation to multi-point collaborative support. However, related technologies mostly achieve reactive power regulation through device-level voltage outer loops or fixed Q-V droop, often assuming that the grid strength and equivalent impedance are relatively constant. They lack the ability to adapt to system-level factors such as changes in short-circuit ratio, grid reconfiguration, and fluctuations in grid connection impedance. This leads to mismatches in support strength of the same strategy in different regions and operating modes: in strong grids, it may be insufficient, affecting the voltage recovery speed; in weak grids, it may be over-supported, inducing voltage swirl and oscillation, and even interacting with multiple devices to form a risk of collective oscillation. At the same time, there are also problems of limited and uneven distribution of reactive power resources at the system level. The device is constrained by apparent power and current capacity. When the active power output is high, the reactive power margin decreases. If there is no support allocation mechanism that is coordinated with the capacity boundary, it is easy to "not be able to support when it should" or "sudden change in support after limiting", which will cause uncertainty in voltage recovery and amplify the vulnerability of the system.

[0024] Therefore, this application provides an active voltage support scheme that is oriented towards changes in system operation mode, can dynamically adjust the support threshold and support strength according to the grid strength and grid-connected equivalent impedance, and takes into account device capacity constraints, so as to improve the voltage recovery speed and stability during fault clearing and disturbance recovery stages.

[0025] The active voltage support control scheme for grid-connected converters provided in this application first collects the grid connection point voltage and grid connection current, and obtains the synchronization phase angle through a phase-locked loop, completing coordinate transformation to obtain the dq components of voltage and current. Second, a DC voltage control loop generates active current commands based on the DC bus voltage deviation. Then, based on online estimation results of grid operating characteristics, the upper and lower limit coefficients of the voltage bandgap are dynamically calculated, and voltage range determination is performed. Next, when the voltage exceeds the upper limit or falls below the lower limit, a reactive power compensation amount is generated based on the voltage deviation and superimposed with a preset reactive power value to obtain a reactive power reference. Simultaneously, the reactive power reference is limited by the apparent capacity constraint of the device. Finally, the limited reactive power reference is input into the reactive power outer loop and the current inner loop to drive the converter to inject reactive current into the grid connection point to achieve voltage support. This scheme was verified under fault and recovery conditions in a typical grid-connected system built on PSCAD. The results show that it can improve the voltage recovery speed and stability during fault clearing and disturbance recovery phases.

[0026] In one exemplary embodiment, such as Figure 1 As shown, a converter active voltage support control method is provided, including: Step 101: Obtain the grid connection point voltage and grid connection point current.

[0027] Step 102: Based on the phase-locked loop, perform dq coordinate transformation on the grid connection point voltage and the grid connection point current to obtain voltage components and current components, and calculate reactive power based on the voltage components and the current components.

[0028] Step 103: A DC voltage control loop is used to generate an active current command based on the DC bus voltage deviation, and the DC side voltage is determined based on the active current command.

[0029] Step 104: Calculate the short-circuit ratio based on the grid connection point voltage and the grid equivalent impedance, and dynamically calculate the upper limit coefficient and lower limit coefficient of the voltage bandgap based on the short-circuit ratio.

[0030] Step 105: Determine the voltage range based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and the set voltage component value, and determine the voltage bandgap of the voltage component based on the voltage range to determine the upper limit exceedance value and the lower limit exceedance value.

[0031] Step 106: When the voltage component exceeds the voltage range, a reactive power compensation amount is generated based on the upper limit exceedance indicator, the lower limit exceedance indicator, and the voltage deviation. A reactive power reference value is calculated based on the reactive power compensation amount and the preset reactive power.

[0032] Step 107: The reactive power reference value is limited by the apparent capacity constraint of the converter to obtain the limited reactive power reference value.

[0033] Step 108: Obtain a reactive power reference output value based on the limited reactive power reference value, the reactive power, and the DC side voltage; the reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

[0034] In another exemplary embodiment of this application, step 102 specifically includes: performing a dq coordinate transformation to obtain the voltage component based on the grid connection point voltage and grid connection current. u gd , u gq ) and current component ( i gd , i gq And according to the formula Calculate reactive power , u gd Represents the d-axis voltage component value. u gq This represents the q-axis voltage component value. i gd This represents the d-axis current component value. i gqThis represents the q-axis current component value.

[0035] Calculated Compared with the subsequently obtained reference value of reactive power after limiting The comparison is performed, and a q-axis current reference value I is generated through a PI circuit. oqref .

[0036] In step 103, a DC voltage control loop is used to directly generate active current commands based on the DC bus voltage deviation to maintain DC side voltage stability. The DC voltage control adopts a traditional control method, which is carried out simultaneously with reactive power control.

[0037] In another exemplary embodiment of this application, in step 104, the formula for calculating the short-circuit ratio is as follows.

[0038] .

[0039] in, This represents the short-circuit ratio at time t; This represents the grid connection point voltage at time t; Indicates the grid-connected equivalent impedance; This indicates the equivalent short-circuit capacity of the AC system at the grid connection point; It represents the equivalent active power of new energy sources at the grid connection point.

[0040] In another exemplary embodiment of this application, step 104, which dynamically calculates the upper limit coefficient and lower limit coefficient of the voltage bandgap based on the short-circuit ratio, specifically includes the following steps.

[0041] (1) Determine whether it is necessary to widen the bandwidth based on the short-circuit ratio.

[0042] Specifically, when the short-circuit ratio is less than a set grid strength threshold, it is determined that the bandwidth needs to be widened; when the short-circuit ratio is greater than or equal to the set grid strength threshold, it is determined that the bandwidth does not need to be widened.

[0043] (2) If yes, then calculate the voltage amplitude coefficient correction value based on the adaptive adjustment step size and the grid strength weighting coefficient. Based on the voltage amplitude coefficient correction value, the initial upper limit coefficient of the set AC phase voltage amplitude, and the initial lower limit coefficient of the set AC phase voltage amplitude, calculate the voltage bandgap upper limit coefficient and the voltage bandgap lower limit coefficient. If no, then determine the voltage amplitude coefficient correction value to be 0, determine the initial upper limit coefficient of the set AC phase voltage amplitude as the voltage bandgap upper limit coefficient, and determine the initial lower limit coefficient of the set AC phase voltage amplitude as the voltage bandgap lower limit coefficient.

[0044] Specifically, the upper limit coefficient of the voltage bandgap at time t. and the lower limit coefficient of the voltage bandgap at time t Adaptive adjustment is achieved using the following formula.

[0045] .

[0046] .

[0047] .

[0048] in, To set the initial upper limit coefficient for the AC phase voltage amplitude; To set the initial lower limit coefficient for the AC phase voltage amplitude; This is the correction value for the voltage amplitude coefficient at time t; To adaptively adjust the step size; Let be the power grid intensity weighting coefficient at time t.

[0049] when (Strong network) time, , At this point, the band gap is not widened further; when (Weak network) , At this point, the band gap widens. This is the power grid strength threshold, typically set to 3.

[0050] In another exemplary embodiment of this application, the expression for the voltage range is: ;in, The upper limit coefficient of the voltage bandgap at time t; The lower limit coefficient of the voltage bandgap at time t; The set d-axis voltage component value.

[0051] Voltage bandgap determination includes: exceeding the upper limit characteristic quantity With lower limit transcendence characterization The determination. Specifically, when the voltage amplitude is higher than... Time setting It also introduces upper limit deviation compensation when the voltage amplitude is lower than the limit. Time setting It also introduces a lower limit deviation compensation, and when the voltage amplitude is within Interval time , And make reactive power compensation amount .

[0052] The expressions for the upper limit transcendental quantity and the lower limit transcendental quantity are as follows.

[0053] .

[0054] .

[0055] in, The upper limit exceeds the representation quantity; This is the lower limit of the transcendental quantity; This is the upper limit coefficient of the voltage bandgap; This is the lower limit coefficient of the voltage bandgap; This represents the d-axis voltage component value of the voltage component obtained after performing a dq coordinate transformation on the grid connection point voltage.

[0056] In another exemplary embodiment of this application, the formula for calculating the reactive power compensation amount is as follows.

[0057] .

[0058] .

[0059] in, This refers to reactive power compensation. The upper limit exceeds the representation quantity; The gain when the AC phase voltage amplitude exceeds the upper limit; This is the upper limit coefficient of the voltage bandgap; The set d-axis voltage component value; This refers to the d-axis voltage component value in the voltage components obtained after performing a dq coordinate transformation on the grid connection point voltage; This is the lower limit of the transcendental quantity; The gain when the AC phase voltage amplitude exceeds the lower limit; This is the lower limit coefficient of the voltage bandgap. The fundamental angular frequency of the power grid; This is the grid-connected inductance between the converter and the power grid; This is the equivalent resistance on the grid-connected side.

[0060] In another exemplary embodiment of this application, step 106, calculating a reactive power reference value based on the reactive power compensation amount and the preset reactive power, specifically includes: reactive power reference value. Based on preset reactive power And is the reactive power compensation amount Superimposed generation, satisfying ,and It is zero when the voltage is within the bandgap range, and increases as the voltage deviation increases when the voltage exceeds the limit.

[0061] In another exemplary embodiment of this application, step 107 specifically includes: calculating a limiting value based on the rated apparent power and the real-time active power of the converter; determining the apparent capacity constraint of the converter based on the limiting value, so that the reactive power reference value is within the apparent capacity constraint of the converter, and obtaining the limited reactive power reference value.

[0062] Specifically, to meet the converter capacity constraint, a PQ limit is introduced for the reactive power reference value, and the limit value meets the following requirements. , Let P(t) be the rated apparent power, and P(t) be the real-time active power of the converter. Saturation constraint is applied to obtain the final ,make .

[0063] The overall process of the converter control system is as follows: Figure 2 As shown, the active voltage-supported reactive power control process is as follows: Figure 3 As shown. Figure 2 Middle,U dcref U is the reference value for the DC bus voltage. dc This is the DC bus voltage feedback value; I od This represents the actual value of the d-axis current; I oqref I is the reference value for the q-axis current. oq θ is the actual value of the q-axis current. pll For the phase-locked loop angle, U oref This is the reactive power reference output value. Figure 3 LPF is a low-pass filter.

[0064] The following is a calculation example demonstrating the testing and verification of the converter active voltage support control method described in the above embodiment on PSCAD. The system topology is as follows: Figure 4 As shown, Figure 4 A three-terminal flexible direct current transmission (VSC-MTDC) model is shown, which employs a typical decoupled dq control strategy; the control system structure is as follows. Figure 5 As shown, Figure 4 This demonstrates the adaptive generation of reactive power command value Q using an active voltage support strategy. ref The system's power reference value is 100 MVA.

[0065] The example used is a three-terminal voltage source converter multi-terminal DC (VSC-MTDC) system, which consists of three converter stations (VSC1-VSC3) and achieves flexible interconnection between AC sub-networks with rated frequencies of 60Hz and 50Hz through a DC bus.

[0066] (1) The system is set to experience a three-phase short-circuit ground fault at 0.7s and clear the fault at 0.85s. Actual results show that when active voltage support control is used, after the fault is cleared, the converter quickly adjusts its reactive power to provide voltage support, resulting in a smoother and faster PCC voltage recovery process. The grid voltage waveform when a three-phase short-circuit ground fault occurs without active voltage support is as follows: Figure 6 As shown, the grid voltage waveform when a three-phase short-circuit ground fault occurs using the active voltage support strategy is as follows: Figure 7 As shown.

[0067] (2) The system is set to experience a single-phase short-circuit ground fault at 0.7s and clear the fault at 0.85s. Simulation results show that when active voltage support control is used, after the fault is cleared, the converter quickly adjusts its reactive power to support the voltage, the PCC voltage does not fluctuate drastically, quickly returns to stability, and the voltage drop is smaller. The grid voltage waveform for a single-phase short-circuit ground fault without active voltage support strategy is as follows: Figure 8 As shown, the voltage waveform of the power grid under a single-phase short-circuit ground fault using the active voltage support strategy is as follows: Figure 9 As shown.

[0068] (3) Set the system load to surge at 1 second. Simulation results show that, with different band gaps, the reactive power reference value of the strong system remains unchanged, and the active voltage support is ineffective; however, the reactive power reference value of the weak system changes, and the active voltage support becomes effective. The voltage waveform when there is a slight voltage fluctuation is as follows: Figure 10 As shown, the results of the reactive power reference value for the strong system are as follows: Figure 11 As shown, the results of the reactive power reference value for the weak system are as follows: Figure 12 As shown.

[0069] This application presents an active voltage support control method for grid-connected converters, which has the following advantages.

[0070] (1) This application addresses the issue of inconsistent support effects of traditional fixed threshold voltage support strategies under different grid strengths. By introducing online estimation results of grid operating characteristics, the upper and lower limit coefficients of the voltage bandgap are dynamically calculated and the voltage range is determined, enabling the control threshold to adaptively adjust with changes in system operating conditions such as short-circuit ratio and equivalent impedance. This design allows the device to intervene in voltage support more quickly under strong grid conditions, and to appropriately widen the bandgap and reduce the tendency for excessive reactive power operation when the grid is weak or the impedance increases, thereby improving the system stability margin.

[0071] (2) This application employs a "limit-triggered" reactive power compensation mechanism during the reactive power reference generation process. Reactive power compensation is only generated based on the voltage deviation when the voltage exceeds the upper limit or falls below the lower limit, and this is superimposed with the preset reactive power to obtain the reactive power reference. This avoids continuously introducing reactive power fluctuations within the normal voltage range, reduces unnecessary reactive power regulation and losses, and improves voltage quality under steady-state operation. Furthermore, by combining the apparent capacity constraint of the device with the reactive power reference, it is ensured that the reactive power command is continuously available within the rated capacity and current capability range, reducing the risk of control performance degradation due to sudden limit changes and improving feasibility and operational safety in engineering applications.

[0072] Based on the same inventive concept, this application also provides a converter active voltage support control device for implementing the converter active voltage support control method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations of one or more embodiments of the converter active voltage support control device provided below can be found in the limitations of the converter active voltage support control method described above, and will not be repeated here.

[0073] In one exemplary embodiment, a converter active voltage support control device is provided, comprising: a grid connection parameter acquisition module for acquiring grid connection point voltage and grid connection point current.

[0074] The reactive power calculation module is used to perform dq coordinate transformation on the grid connection point voltage and the grid connection point current based on the phase-locked loop to obtain voltage components and current components, and to calculate reactive power based on the voltage components and the current components.

[0075] A DC voltage control module is used to generate an active current command based on the DC bus voltage deviation using a DC voltage control loop, and to determine the DC side voltage based on the active current command.

[0076] The bandgap upper and lower limit coefficient calculation module is used to calculate the short-circuit ratio based on the grid connection point voltage and the grid equivalent impedance, and to dynamically calculate the upper limit coefficient and lower limit coefficient of the voltage bandgap based on the short-circuit ratio.

[0077] The exceedance characterization module is used to determine a voltage range based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and a set voltage component value, and to determine the voltage bandgap of the voltage component based on the voltage range, thereby determining the upper limit exceedance characterization and the lower limit exceedance characterization.

[0078] The reactive power reference value calculation module is used to generate a reactive power compensation amount based on the upper limit exceedance indicator, the lower limit exceedance indicator, and the voltage deviation when the voltage component exceeds the voltage range, and to calculate a reactive power reference value based on the reactive power compensation amount and the preset reactive power.

[0079] The limiting module is used to limit the reactive power reference value using the apparent capacity constraint of the converter, so as to obtain the limited reactive power reference value.

[0080] The voltage support control module is used to obtain a reactive power reference output value based on the limited reactive power reference value, the reactive power, and the DC side voltage; the reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

[0081] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 13 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores reactive power reference output values. The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a converter active voltage support control method.

[0082] Those skilled in the art will understand that Figure 13 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer equipment to which the present application is applied. Specific computer equipment may include, for example, [the following is a list of possible additional structures]. Figure 13 The embodiments show more or fewer components, combinations of certain components, or different component arrangements. In one exemplary embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program, which the processor executes to implement the steps in the above-described method embodiments.

[0083] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0084] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0085] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0086] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0087] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, etc., and are not limited to these.

[0088] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A converter active voltage support control method, characterized in that, include: Obtain the grid connection point voltage and grid connection point current; Based on the phase-locked loop, the voltage and current at the grid connection point are transformed by dq coordinates to obtain voltage and current components, and reactive power is calculated based on the voltage and current components. A DC voltage control loop is used to generate an active current command based on the DC bus voltage deviation, and the DC side voltage is determined based on the active current command. The short-circuit ratio is calculated based on the grid connection point voltage and the grid equivalent impedance, and the upper limit coefficient and lower limit coefficient of the voltage bandgap are dynamically calculated based on the short-circuit ratio. The voltage range is determined based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and the set voltage component value. The voltage bandgap is then determined based on the voltage range to identify the upper limit exceedance value and the lower limit exceedance value. When the voltage component exceeds the voltage range, a reactive power compensation amount is generated based on the upper limit exceedance indicator, the lower limit exceedance indicator, and the voltage deviation. A reactive power reference value is calculated based on the reactive power compensation amount and the preset reactive power. The reactive power reference value is limited by the apparent capacity constraint of the converter to obtain the limited reactive power reference value. The reactive power reference output value is obtained based on the limited reactive power reference value, the reactive power, and the DC side voltage; The reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

2. The converter active voltage support control method according to claim 1, characterized in that, The formula for calculating the short-circuit ratio is: ； in, This represents the short-circuit ratio at time t; This represents the grid connection point voltage at time t; It represents the grid-connected equivalent impedance.

3. The converter active voltage support control method according to claim 1, characterized in that, The voltage bandgap upper limit coefficient and voltage bandgap lower limit coefficient are dynamically calculated based on the short-circuit ratio, specifically including: Determine whether to widen the bandwidth based on the short-circuit ratio; If so, the voltage amplitude coefficient correction value is calculated based on the adaptive adjustment step size and the grid strength weighting coefficient. Based on the voltage amplitude coefficient correction value, the initial upper limit coefficient of the AC phase voltage amplitude, and the initial lower limit coefficient of the AC phase voltage amplitude, the voltage bandgap upper limit coefficient and the voltage bandgap lower limit coefficient are calculated. If not, then the voltage amplitude coefficient correction value is set to 0, the initial upper limit coefficient of the AC phase voltage amplitude is set as the upper limit coefficient of the voltage bandgap, and the initial lower limit coefficient of the AC phase voltage amplitude is set as the lower limit coefficient of the voltage bandgap.

4. The converter active voltage support control method according to claim 1, characterized in that, The expression for the voltage range is: ； in, The upper limit coefficient of the voltage bandgap at time t; Let be the lower limit coefficient of the voltage bandgap at time t; The set d-axis voltage component value; The expression for the upper limit transcendental characteristic is: ； The expression for the lower limit transcendence characteristic is: ； in, The upper limit exceeds the representation quantity; This is the lower limit of the transcendental quantity; This is the upper limit coefficient of the voltage bandgap; This is the lower limit coefficient of the voltage bandgap; This represents the d-axis voltage component value of the voltage component obtained after performing a dq coordinate transformation on the grid connection point voltage.

5. The converter active voltage support control method according to claim 1, characterized in that, The formula for calculating the reactive power compensation is: ； in, This is the amount of reactive power compensation; The upper limit exceeds the representation quantity; The gain when the AC phase voltage amplitude exceeds the upper limit; This is the upper limit coefficient of the voltage bandgap; The set d-axis voltage component value; This refers to the d-axis voltage component value in the voltage components obtained after performing a dq coordinate transformation on the grid connection point voltage; This is the lower limit of the transcendental quantity; The gain when the AC phase voltage amplitude exceeds the lower limit; This is the lower limit coefficient of the voltage bandgap.

6. The converter active voltage support control method according to claim 1, characterized in that, The reactive power reference value is limited by the apparent capacity constraint of the converter to obtain the limited reactive power reference value, specifically including: The limiting value is calculated based on the rated apparent power and the real-time active power of the converter; The apparent capacity constraint of the converter is determined based on the limiting value, so that the reactive power reference value is within the apparent capacity constraint of the converter, and the limiting reactive power reference value is obtained.

7. The converter active voltage support control method according to claim 3, characterized in that, Determining whether to widen the bandwidth based on the short-circuit ratio specifically includes: When the short-circuit ratio is less than the set grid strength threshold, it is determined that the bandwidth needs to be widened; when the short-circuit ratio is greater than or equal to the set grid strength threshold, it is determined that the bandwidth does not need to be widened.

8. A converter active voltage support control device, characterized in that, include: The grid connection parameter acquisition module is used to acquire the grid connection point voltage and grid connection point current. The reactive power calculation module is used to perform dq coordinate transformation on the grid connection point voltage and the grid connection point current based on the phase-locked loop to obtain voltage components and current components, and to calculate reactive power based on the voltage components and the current components. A DC voltage control module is used to generate an active current command based on the DC bus voltage deviation using a DC voltage control loop, and to determine the DC side voltage based on the active current command. The bandgap upper and lower limit coefficient calculation module is used to calculate the short-circuit ratio based on the grid connection point voltage and the grid equivalent impedance, and to dynamically calculate the voltage bandgap upper limit coefficient and voltage bandgap lower limit coefficient based on the short-circuit ratio. The exceedance characterization module is used to determine a voltage range based on the upper limit coefficient of the voltage bandgap, the lower limit coefficient of the voltage bandgap, and a set voltage component value, and to determine the voltage bandgap of the voltage component based on the voltage range, thereby determining the upper limit exceedance characterization and the lower limit exceedance characterization. The reactive power reference value calculation module is used to generate a reactive power compensation amount based on the upper limit exceedance indicator, the lower limit exceedance indicator and the voltage deviation when the voltage component exceeds the voltage range, and to calculate the reactive power reference value according to the reactive power compensation amount and the preset reactive power. The limiting module is used to limit the reactive power reference value using the apparent capacity constraint of the converter, so as to obtain the limited reactive power reference value. The voltage support control module is used to obtain a reactive power reference output value based on the limited reactive power reference value, the reactive power and the DC side voltage. The reactive power reference output value is used to drive the converter to input reactive current to the grid connection point to achieve voltage support.

9. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that the processor executes the computer program to implement the converter active voltage support control method according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the converter active voltage support control method according to any one of claims 1-7.

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