Method and system for equalizing over-capacity multi-branch of grid-connected magnetic valve type static synchronous compensator

Abstract

This invention provides a method and system for equalizing multiple branches of a grid-type magnetic valve-type static synchronous condenser with overcapacity, relating to the field of reactive power compensation technology in power systems. The invention first defines adjacent branches of each branch of the synchronous condenser according to their electrical cascading sequence, and reads reference signals within the current rolling window. For each branch, the adjustment deviation between that branch and its adjacent branches is calculated at each sampling point, and cumulative deviation verification and marking of branches to be adjusted are completed within the current rolling window. At the start of the next monitoring cycle, the branch to be adjusted performs virtual impedance step adjustment at a fixed ratio until the current deviation meets the requirements. It then determines whether the number of times the reference data for this adjustment has been repeated in previous adjustment cycles exceeds the sample size trigger threshold. If it does, the fixed ratio is optimized and replaced. This method, with its decentralized architecture, offers higher reliability and allows for the development of fixed ratio optimization measures during continuous operation, improving convergence and iteration speed.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation technology in power systems, specifically to a method and system for balancing multiple branches of a grid-type magnetic valve-type static synchronous condenser with overcapacity. Background Technology

[0002] To further improve the capacity level, operational redundancy and fault tolerance of a single device, grid-type solenoid valve static synchronous condensers generally adopt an overcapacity multi-branch structure. However, the output current imbalance between parallel branches is very likely to occur, which in turn generates branch circulating current. To address the need for current sharing and equalization control across multiple branches, existing technologies generally employ a centralized control architecture. Its core logic involves using a central controller to collect high-frequency data on the output current and operating status of all branches in the entire system. The average output current of all branches in the system is used as the current sharing control benchmark. For the deviation between the current of each branch and the benchmark value, a centralized PID controller calculates the virtual impedance correction or output voltage reference correction for each branch. Then, the control commands are uniformly sent to each branch via a global communication link for execution and adjustment, ultimately achieving current sharing among branches. Then, in the case of overcapacity multi-branch scenarios, there are many branches, and the central controller needs to establish a high-frequency global communication link with all branches. The communication bandwidth requirement is high and the transmission delay is large, which makes it easy for data synchronization deviation to occur, leading to inaccurate regulation and increased circulating current in branches. In addition, the PID parameters are difficult to tune. When the power grid operating conditions fluctuate or the solenoid valve saturation changes, regulation overshoot and system oscillation are likely to occur. The convergence iteration speed is slow and cannot meet the rapid response requirements of network-type equipment.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a supercapacitive multi-branch equalization method and system for a grid-type magnetic valve-type static synchronous condenser, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The overcapacitance multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser includes the following steps: Based on the electrical cascading sequence of each branch of the synchronous condenser, the adjacent branches of each branch are defined, and the reference signals of each branch of the synchronous condenser under the current rolling window are obtained. For any branch, read its output current and virtual impedance operating values ​​at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branch as the adjustment value, calculate the difference between its output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to get the cumulative deviation of the branch. If the cumulative deviation of a branch is greater than the event trigger current threshold, determine whether the absolute difference between its output current and that of each adjacent branch meets the adjustment conditions. If it does, define the branch as the branch to be adjusted, and simultaneously extract the current equivalent solenoid saturation and reference signal range of the branch as reference data for this round of adjustment, and use the average output current of its adjacent branches at the same sampling point as its adjustment value. For any branch defined as to be adjusted, its virtual impedance operating value is adjusted in a step-by-step manner at a fixed ratio in each subsequent monitoring cycle until the adjustment termination condition is met. It is then determined whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, the fixed ratio is optimized based on the virtual impedance operating value at the end of this round of adjustment.

[0006] Furthermore, the method for defining adjacent branches of each branch based on the electrical cascading sequence of each branch of the synchronous condenser is as follows: In the synchronous condenser, each branch is sequentially numbered with consecutive natural numbers along the linear extension direction of the busbar. For any branch, the two branches immediately before and after its number are defined as its adjacent branches. Specifically, for the first branch, its immediately following branch and the last branch are defined as its adjacent branches; for the last branch, its immediately preceding branch and the first branch are defined as its adjacent branches.

[0007] Furthermore, the scrolling window is a 20ms time interval, and one scrolling window contains 20 sampling points, with a time interval of 1ms for each sampling point.

[0008] Furthermore, the method for calculating the adjustment deviation is as follows: For any branch, calculate the average output current of the branch and its adjacent branches at the same sampling point, and use it as the adjustment value of the branch at this sampling point. Calculate the difference between the output current of the branch at the same sampling point and the adjustment value, and use it as the adjustment deviation of the branch at this sampling point.

[0009] Furthermore, the method for setting the event trigger current threshold is as follows: For any branch, 2% of the rated output current effective value of the branch is taken as its deviation threshold, and 2 / 3 is taken as the single-step pre-trigger deviation ratio. The deviation threshold of the branch, the number of sampling points in the current scrolling window and the single-step pre-trigger deviation ratio are multiplied in sequence to obtain the event trigger current threshold of the branch.

[0010] Furthermore, the method for determining whether the absolute difference between the output current of any branch and its adjacent branches meets the adjustment conditions is as follows: If the cumulative deviation of a branch exceeds the event trigger current threshold, the last sampling point in the current scrolling window is taken as the target sampling point. The absolute difference of the output current between the branch and each adjacent branch at the target sampling point is calculated. When the absolute difference of the output current between the branch and each adjacent branch at the target sampling point is greater than the deviation threshold, the branch is judged to meet the adjustment conditions.

[0011] Furthermore, the method for simultaneously extracting the current equivalent solenoid saturation and reference signal range of this branch is as follows: Extract the instantaneous sampling data of the DC current of the excitation winding of the solenoid body within the current scrolling window, and obtain its fundamental component RMS value and the RMS values ​​of the 3rd, 5th and 7th odd harmonic components through fast Fourier transform decomposition. Calculate the sum of squares of the RMS values ​​of each odd harmonic and take the arithmetic square root to obtain the total RMS value of the harmonics. The ratio of the total RMS value of the harmonics to the fundamental RMS value is used as the equivalent solenoid saturation. The reference signals include voltage and angular frequency reference signals. Only the voltage reference signal range is defined for matching to synchronize the rated phase voltage of the phase-shifting camera. Based on this, multiple consecutive voltage ranges are pre-defined: , , , , or ; Obtain the voltage reference signal of the synchronous modulator within the current scrolling window, and determine the voltage range into which the voltage reference signal falls as the matching reference signal range.

[0012] Furthermore, the method for performing a step adjustment on its virtual impedance operating value at a fixed ratio in each subsequent monitoring cycle until the adjustment termination condition is met is as follows: The monitoring period is set to 100ms, and one monitoring period contains 5 rolling windows. For branches that are determined to be adjusted in the current rolling window, no virtual impedance adjustment is performed within the monitoring period to which the current rolling window belongs. Only at the beginning of the next monitoring period, the virtual impedance running value is adjusted in steps according to a fixed ratio. At any moment when step adjustment is performed, if the output current of the branch to be adjusted is greater than the adjustment value, the difference between 1 and a fixed ratio is multiplied by the virtual impedance operating value of the previous monitoring cycle to obtain a new virtual impedance operating value, thereby reducing the virtual impedance operating value. If the output current of the branch to be adjusted is not greater than the adjustment value, the sum of 1 and a fixed ratio is multiplied by the virtual impedance operating value of the previous monitoring cycle to obtain a new virtual impedance operating value, thereby increasing the virtual impedance operating value. The virtual resistance and virtual inductance are adjusted synchronously in the same proportion until the adjustment termination condition is met. The adjustment termination condition is that the absolute difference between the output current of the branch and each adjacent branch at the moment of step adjustment is not greater than the deviation threshold.

[0013] Furthermore, the method for optimizing a fixed ratio is as follows: The sample size trigger threshold is set to be no less than 10. For any historical adjustment round, the equivalent solenoid saturation and reference signal interval in its reference data are extracted and used as the first reference quantity and the second reference quantity, respectively. If the equivalent solenoid saturation in the first reference quantity and the reference data of this round of adjustment fall into the same preset interval, and the reference signal interval in the second reference quantity and the reference data of this round of adjustment are consistent, then it is determined that the reference data of this round of adjustment has appeared repeatedly in the historical adjustment round, and this historical adjustment round is used as the reference adjustment round. Each historical adjustment round is traversed to determine the number of times the reference data of this round of adjustment has appeared repeatedly in previous adjustment rounds. When the number of times the reference data for this round of adjustment has been repeated in previous adjustment rounds exceeds the sample size trigger threshold, the virtual resistance and virtual inductance in the virtual impedance running values ​​recorded in each reference adjustment round are extracted, and the arithmetic mean of all virtual resistances and the arithmetic mean of virtual inductances are calculated respectively, which are used as the target virtual impedance running value for this round of adjustment. The expected convergence step number is preset, and the value of the expected convergence step number is between 1 and 5. First, the current virtual impedance running value of the branch is read, and the total relative change rate of virtual resistance and the total relative change rate of virtual inductance between the current virtual resistance and the target virtual impedance running value are calculated. Then, the total relative change rate is divided equally according to the preset expected convergence step number to obtain the optimized fixed ratio for the next round of adjustment.

[0014] Additionally, a supercapacity multi-branch equalization system for a grid-type magnetic valve-type static synchronous condenser is provided, characterized in that: the system is used to execute the above-mentioned supercapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser, including: The reference signal reading module is used to define the adjacent branches of each branch based on the electrical cascading order of each branch of the synchronous condenser, and to obtain the reference signal of each branch of the synchronous condenser in the current scrolling window. The cumulative deviation calculation module is used to read the output current and virtual impedance operating values ​​of any branch at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branches as the adjustment value, calculate the difference between the output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to obtain the cumulative deviation of the branch. The branch determination module is used to determine whether the absolute difference between the output current of a branch and its adjacent branches meets the adjustment conditions if the cumulative deviation of a branch is greater than the event trigger current threshold. If it does, the branch is defined as the branch to be adjusted. The current equivalent solenoid saturation and reference signal range of the branch are extracted simultaneously as reference data for this round of adjustment, and the average output current of its adjacent branches at the same sampling point is used as its adjustment value. The virtual impedance optimization module is used to perform a step adjustment on the virtual impedance operating value of any branch defined as to be adjusted in each subsequent monitoring cycle by a fixed proportion until the adjustment termination condition is met. It determines whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, it optimizes the fixed proportion based on the virtual impedance operating value when the current round of adjustment is completed.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention defines the adjacent branches of each branch by the electrical cascading sequence of each branch, calculates the cumulative deviation by using the average output current of the current branch and the adjacent branches as the adjustment value, and constructs the adjustment condition for whether the virtual impedance needs to be adjusted by comparing the result with the event trigger current threshold, without the need to establish a global high-frequency communication link. This invention also improves the convergence iteration speed by analyzing the virtual impedance operating values ​​under previous adjustment rounds when the number of times the reference data of the current adjustment appears in previous adjustment rounds exceeds the sample size trigger threshold, and optimizing the fixed ratio based on the virtual impedance operating values ​​when the current adjustment is completed. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 This is a schematic diagram of the overall system structure of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example: Please see Figure 1 The present invention provides a technical solution: The overcapacitance multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser includes the following steps: S1: Define the adjacent branches of each branch based on the electrical cascading sequence of each branch of the synchronous condenser, and obtain the reference signal of each branch of the synchronous condenser under the current rolling window; Each branch of a synchronous condenser is an independent modular power unit consisting of an independent solenoid reactor, a supercapacitor bank, a fully controlled converter bridge arm, and a branch controller. All power units are installed sequentially and tightly side-by-side in the same equipment room or cabinet, forming a linear and continuous physical installation sequence. The AC and DC sides of all power units are connected in parallel to a common AC bus and a DC supercapacitor bus, respectively, forming a multi-branch parallel loop. Traditional fully connected communication links collect the output current and operating status data of each branch individually, requiring significant communication bandwidth. Therefore, along the linear extension direction of the busbar, i.e., the physical installation sequence, each branch is sequentially numbered with consecutive natural numbers to construct a closed-loop topology, connecting all synchronous condensers. Each branch is numbered consecutively with natural numbers 1, 2, 3, ..., N, where N is the total number of branches. For a given branch, the two branches immediately preceding and following its number are defined as its adjacent branches. Specifically, for the first branch numbered 1, the last branch numbered N and its immediately following branch numbered 2 are defined as its adjacent branches. For the last branch numbered N, the first branch numbered 1 and its immediately preceding branch numbered N-1 are defined as its adjacent branches. This constructs a distributed, decentralized control architecture. Subsequently, only the output current data of adjacent branches needs to be obtained, and adjustment conditions need to be set to adjust the virtual impedance to adjust the output current of its own branch. This avoids the problem of simultaneous adjustment of all branches and the spread of deviations throughout the system, thereby ensuring that the average output current of each branch is the same. For acquiring the reference signals of each branch of the synchronous condenser within the current rolling window, virtual synchronous generator technology is often used. The core of this technology is to simulate the rotational inertia of a synchronous generator, providing inertia and damping support to the power grid. Its response speed cannot be too fast, otherwise it may cause system oscillations; if it is too slow, it cannot track grid fluctuations. Based on engineering experience, a monitoring period of 100ms is set, allowing the reference signals output by each branch of the synchronous condenser to be updated every 100ms using virtual synchronous generator technology. A rolling window with a time interval of 20ms is set, and the reference signals are read once per rolling window. The reference signals output by each branch of the pacing camera are used to obtain the reference signals of each branch of the synchronous pacing camera under the current rolling window. The reference signals include voltage and angular frequency reference signals. This virtual synchronous generator technology simulates the inertia-damping element of the synchronous generator rotor motion equation and the voltage amplitude control element of the excitation regulation. Then, by inputting the real-time sampled value of the grid voltage at the grid connection point and the total reactive / active power command value of the system, a unified reference signal for each branch can be obtained in each monitoring cycle, namely the angular frequency and voltage reference signals. Moreover, the angular frequency and voltage reference signals will remain unchanged within a detection cycle. The virtual impedance consists of virtual inductance and virtual resistance. During system cold starts, restarts, and resets, an initial virtual impedance is set as the operating value. This means a unified, fixed initial virtual impedance is set for all branches. During system (synchronous condenser) cold starts, restarts, and resets, this initial virtual impedance is directly assigned to the currently latched operating value and is not replaced by subsequent optimizations of the operating value. Afterward, the system calculates the voltage execution value and drives the converter to correct the output current. This converter correction process is performed every 50μs. Simultaneously, the initial virtual impedance also serves as a fixed reference anchor value, facilitating subsequent optimization and adjustment. The initial virtual impedance is set as follows: For the virtual inductance, take 1.2 times the total equivalent reactance of each branch under rated voltage conditions, including the winding inherent reactance, the solenoid valve rated excitation reactance, and the branch output line reactance. This is then converted to a virtual inductance value using the inductive reactance formula. In the formula, Indicates the total equivalent reactance. This indicates the rated frequency of the power grid, with a value of 50Hz. Indicates virtual inductance; For virtual resistance, take 1.0 times the average of the total equivalent resistance of the inherent resistance of the windings of each branch and the output line resistance of each branch under rated voltage conditions.

[0020] S2: For any branch, read its output current and virtual impedance operating values ​​at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branch as the adjustment value, calculate the difference between its output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to serve as the cumulative deviation of the branch. Set up a scrolling window containing 20 sampling points, with a time interval of 1ms between each sampling point. At each sampling point within the current scrolling window, the output current is read: within the first 1ms of each sampling point, the instantaneous values ​​of the three-phase output current are continuously read, the sum of the squares of the three-phase output current is calculated, the arithmetic mean is taken, and the square root is taken as the effective value of each group of output currents. At each sampling point, the average of the effective values ​​of the output current of this branch and the adjacent branches is taken as the adjustment value at this sampling point. The difference between the output current and the adjustment value at the same sampling point is calculated as the adjustment deviation of this branch at this sampling point. Thus, the adjustment deviation of this branch at each sampling point within the current scrolling window is obtained. It is not necessary to upload the current data of the entire branch to a unified controller. Only the current data of the adjacent branches need to be exchanged between neighbors. This branch can calculate the adjustment value autonomously, which also avoids the deviation of the average value of the entire system caused by the abnormality of individual branches. Then, the absolute values ​​of all adjustment deviations under the current rolling window are summed to obtain the cumulative deviation of the branch. This is because, in actual operation, the sign of the adjustment deviation may change slightly within a short time of 1ms due to the influence of power grid harmonics and small load fluctuations. Therefore, within a single rolling window, the absolute values ​​of the 20 adjustment deviations calculated at 1ms intervals are taken separately and then summed to avoid the situation where the cumulative deviation is close to 0 when there is continuous uneven current.

[0021] S3: If the cumulative deviation of a branch is greater than the event trigger current threshold, determine whether the absolute difference between its output current and that of each adjacent branch meets the adjustment conditions. If it does, define the branch as the branch to be adjusted, and simultaneously extract the current equivalent solenoid saturation and reference signal range of the branch as reference data for this round of adjustment, and use the average output current of its adjacent branches at the same sampling point as its adjustment value. For any branch, 2% of the rated output current RMS value of that branch is used as its deviation threshold, and 2 / 3 is used as the single-step pre-trigger deviation ratio. The event trigger current threshold of that branch is obtained by multiplying the branch's deviation threshold, the number of sampling points in the current rolling window, and the single-step pre-trigger deviation ratio sequentially. Using 2% of the rated output current RMS value of that branch as its deviation threshold can meet the grid's requirements for grid connection point voltage stability and branch circulating current suppression. The adjustment deviation calculated at 1ms intervals is the instantaneous value of a single sampling point, which is susceptible to current sampling noise, electromagnetic interference from switching actions, and instantaneous grid voltage fluctuations. To mitigate the impact of peak flow, 2 / 3 is taken as the single-step pre-trigger deviation ratio, that is, 2 / 3 of the deviation threshold is taken as the single-step pre-trigger upper limit, limiting the upper limit of deviation every 1ms. Finally, the product of the two is multiplied by the number of sampling points in the current rolling window. Essentially, this is to design the maximum allowable value of the cumulative sum of the absolute values ​​of continuous deviations over 20ms. When the adjustment deviation of multiple consecutive sampling points is continuously greater than the single-step pre-trigger upper limit and the cumulative sum reaches the threshold, the mark of the branch to be adjusted will be triggered. This avoids 1ms-level instantaneous deviations caused by sampling noise and also ensures a rapid response to continuous uneven flow conditions. If the cumulative deviation of a branch exceeds the event-triggered current threshold, the last sampling point in the current rolling window is taken as the target sampling point. The absolute difference of the output current between this branch and each adjacent branch at the target sampling point is calculated. If the absolute difference of the output current between this branch and each adjacent branch at the target sampling point is greater than the deviation threshold, the branch is judged to meet the adjustment condition; otherwise, the branch is judged not to meet the adjustment condition. This is because the essence of the cumulative deviation is the sum of the absolute values ​​of the adjustment deviations of 20 1ms sampling points within the rolling window, quickly capturing the continuous deviation trend. When the adjustment deviation calculated at a few sampling points is large, it may cause the cumulative value to exceed the event-triggered threshold. It may have already decayed and returned to steady state before the end of the rolling window, without the need for manual intervention. Therefore, the last sampling point in the current rolling window is taken as the target sampling point. The last sampling point is taken as the target sampling point. The absolute difference of the output current between this branch and each adjacent branch at the target sampling point is calculated to complete the secondary verification. If the absolute difference of the current with the adjacent branch is less than the deviation threshold, it means that the deviation has disappeared and no adjustment is needed. Otherwise, the branch to be adjusted needs to be adjusted. At the same time, the reason for setting this adjustment condition is that the probability of the current branch and a single adjacent branch having abnormal same-direction deviation at the same time is itself at a low level. Based on this, if the absolute difference of the current of only a single adjacent branch is not less than the deviation threshold, it is likely caused by the instantaneous fluctuation of the adjacent branch itself, rather than the problem of this branch. Only when the absolute difference of the current of this branch and the two adjacent branches before and after it is greater than the deviation threshold is it defined as the branch to be adjusted and the adjustment is triggered to effectively reduce the false judgment rate. Synchronously extract the instantaneous sampling data of the DC current of the excitation winding of the solenoid body within the current scrolling window, and obtain its fundamental component RMS value and the RMS values ​​of the 3rd, 5th and 7th odd harmonic components through fast Fourier transform decomposition. Calculate the sum of squares of the RMS values ​​of each odd harmonic and take the arithmetic square root to obtain the total RMS value of the harmonics. The ratio of the total RMS value of the harmonics to the fundamental RMS value is used as the equivalent solenoid saturation. When the power grid is operating normally, the angular frequency fluctuation is extremely small. Therefore, the reference signal range is only taken from the voltage reference signal range for matching, to synchronize the rated phase voltage of the synchronous condenser. Based on this, multiple consecutive voltage ranges are pre-defined: , , , , or This involves using ±5% of the rated phase voltage as a base interval, acquiring the voltage reference signal of the synchronous condenser within the current rolling window, and determining the voltage interval into which the voltage reference signal falls as the matching reference signal interval.

[0022] When a branch is defined as a branch to be adjusted, the equivalent solenoid saturation and reference signal range of the current rolling window of the branch are recorded. The adjustment value update operation is performed synchronously. Within the current rolling window, the effective value of the output current of the two adjacent branches calculated every 1ms is obtained. The arithmetic mean of the effective values ​​of all output currents is taken as the new adjustment value of the branch, replacing the original adjustment value, which is used for subsequent 1ms adjustment deviation calculation. The original adjustment value is the one calculated before. After the uneven current operation of the current rolling window, the output current of the adjacent branches may have changed. Updating the adjustment value can ensure the accuracy of subsequent control.

[0023] S4: For any branch defined as to be adjusted, perform a step adjustment on its virtual impedance operating value at a fixed ratio in each subsequent monitoring cycle until the adjustment termination condition is met. Determine whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, optimize the fixed ratio based on the virtual impedance operating value when this round of adjustment is completed. If a branch is identified as needing adjustment within the current rolling window, no virtual impedance adjustment is performed within its monitoring cycle. This is the control architecture of the slow loop for outer-loop virtual impedance adjustment. Otherwise, if the virtual impedance is modified immediately after any rolling window completes the adjustment determination, the slow loop parameters will randomly change during the operation of the fast loop built into the synchronous condenser, causing a step impact on the branch output current and triggering circulating current oscillations between branches. Only at the beginning of the next monitoring cycle is the virtual impedance operating value adjusted in steps according to a fixed ratio. At any given moment when performing a step adjustment, first determine the direction of the step adjustment. If the output current of this branch is greater than the adjustment value, it indicates that the output of this branch is too large, and the virtual impedance operating value needs to be reduced; conversely, it indicates that the output of this branch is too small, and the virtual impedance operating value needs to be increased. Then, perform a step adjustment on the virtual impedance operating value of the previous monitoring cycle. The virtual resistance and virtual inductance are adjusted synchronously according to the same ratio. If the output of this branch is too large, multiply the difference between 1 and the fixed ratio by the virtual impedance operating value of the previous monitoring cycle to obtain the new virtual impedance operating value; if the output of this branch is too small, multiply the sum of 1 and the fixed ratio by the virtual impedance operating value of the previous monitoring cycle to obtain the new virtual impedance operating value. The new virtual impedance operating value is: In the formula, The virtual resistance value represents the new virtual impedance operating value. This represents the virtual resistance value, which indicates the virtual impedance operating value of the previous monitoring cycle. The virtual inductance value represents the new virtual impedance operating value. The virtual inductance value represents the virtual impedance operating value of the previous monitoring cycle. This indicates a fixed ratio. After adjustment, the new virtual impedance operating value is updated and replaced until the adjustment termination condition is met. The adjustment termination condition is: the absolute difference between the output current of this branch and each adjacent branch at the moment of step adjustment is not greater than the deviation threshold.

[0024] The sample size trigger threshold is set to be no less than 10 to ensure that the statistical results have basic representativeness. For any historical adjustment round, the equivalent solenoid saturation and reference signal interval in its reference data are extracted and used as the first reference quantity and the second reference quantity, respectively. If the equivalent solenoid saturation in the first reference quantity and the reference data of the current adjustment round fall into the same preset interval, and the reference signal interval in the second reference quantity and the reference data of the current adjustment round are consistent, then it is determined that the reference data of the current adjustment round has appeared repeatedly in the historical adjustment round, and the historical adjustment round is used as the reference adjustment round. Each historical adjustment round is traversed to determine the number of times the reference data of the current adjustment round has appeared repeatedly in previous adjustment rounds. When the equivalent solenoid valve saturation falls within the same preset range and the reference signal range is completely consistent, it is considered that the excitation characteristics of the solenoid valve reactor, the grid operating benchmark, and the branch current sharing control target are unified. When the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds exceeds the sample size trigger threshold, the arithmetic mean of all virtual resistance components and the arithmetic mean of virtual inductive reactance are calculated respectively, which are used as the target virtual impedance operating value of this round of adjustment. The expected convergence step number is preset, and the value of the expected convergence step number is between 1 and 5, in order to control the duration of current sharing adjustment and solve the contradiction of easy oscillation when the step size is large and slow convergence when the step size is small, which is caused by traditional fixed ratio adjustment. At this time, the virtual impedance operating value of the branch is read under this round of adjustment, and the total relative change rate of virtual resistance and the total relative change rate of virtual inductive reactance between the current virtual resistance and the target virtual impedance operating value are calculated. Then, the total relative change rate is divided equally according to the preset expected convergence step number to obtain the value of the next round of adjustment. The optimized fixed ratio is used to ensure that the virtual impedance converges smoothly, accurately, and at a preset pace to the target value from the current value, guaranteeing that there is no overshoot risk in each adjustment step. This allows the virtual impedance and virtual reactance to converge synchronously to their respective optimal target values ​​within the same expected number of steps, without interference from current surges affecting the stable operation of the fast loop. Independent calculation of the total relative change rate of virtual resistance and virtual reactance is performed. The virtual resistance and virtual impedance read in this round of adjustment are adjusted separately. Specifically, based on the determined direction of the step adjustment, the virtual resistance read in this round of adjustment is multiplied by 1 and summed with the optimized fixed ratio to obtain the adjusted virtual impedance; or the difference between the virtual resistance read in this round of adjustment and the optimized fixed ratio is used. Similarly, the virtual reactance read in this round of adjustment is multiplied by 1 and summed with the optimized fixed ratio to obtain the adjusted virtual reactance; or the difference between the virtual reactance read in this round of adjustment and the optimized fixed ratio is used.

[0025] Please see Figure 2 The present invention further provides an overcapacity multi-branch equalization system for a grid-type magnetic valve-type static synchronous condenser, used to perform the above-described overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser, comprising: The reference signal reading module is used to construct the synchronous condenser branches into a ring-adjacent topology and obtain the reference signal of each synchronous condenser branch under the current scrolling window. The cumulative deviation calculation module is used to read the output current and virtual impedance operating values ​​of any branch at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branches as the adjustment value, calculate the difference between the output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to obtain the cumulative deviation of the branch. The branch determination module is used to determine whether the absolute difference between the output current of a branch and its adjacent branches meets the adjustment conditions if the cumulative deviation of a branch is greater than the event trigger current threshold. If it does, the branch is defined as the branch to be adjusted. The current equivalent solenoid saturation and reference signal range of the branch are extracted simultaneously as reference data for this round of adjustment, and the average output current of its adjacent branches at the same sampling point is used as its adjustment value. The virtual impedance optimization module is used to perform a step adjustment on the virtual impedance operating value of any branch defined as to be adjusted in each subsequent monitoring cycle at a fixed ratio until the adjustment termination condition is no longer met. It determines whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, it optimizes the fixed ratio based on the virtual impedance operating value when the current round of adjustment is completed.

[0026] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0027] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0028] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0029] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for overcapacity multi-branch equalization of a grid-type magnetic valve-type static synchronous condenser, characterized in that, The specific steps include: Based on the electrical cascading sequence of each branch of the synchronous condenser, the adjacent branches of each branch are defined, and the reference signals of each branch of the synchronous condenser under the current rolling window are obtained. For any branch, read its output current and virtual impedance operating values ​​at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branch as the adjustment value, calculate the difference between its output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to get the cumulative deviation of the branch. If the cumulative deviation of a branch is greater than the event trigger current threshold, determine whether the absolute difference between its output current and that of each adjacent branch meets the adjustment conditions. If it does, define the branch as the branch to be adjusted, and simultaneously extract the current equivalent solenoid saturation and reference signal range of the branch as reference data for this round of adjustment, and use the average output current of its adjacent branches at the same sampling point as its adjustment value. For any branch defined as to be adjusted, its virtual impedance operating value is adjusted in a step-by-step manner at a fixed ratio in each subsequent monitoring cycle until the adjustment termination condition is met. It is then determined whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, the fixed ratio is optimized based on the virtual impedance operating value at the end of this round of adjustment.

2. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 1, characterized in that: The method for defining adjacent branches based on the electrical cascading sequence of each branch of a synchronous condenser is as follows: In the synchronous condenser, each branch is sequentially numbered with consecutive natural numbers along the linear extension direction of the busbar. For any branch, the two branches immediately before and after its number are defined as its adjacent branches. Specifically, for the first branch, its immediately following branch and the last branch are defined as its adjacent branches; for the last branch, its immediately preceding branch and the first branch are defined as its adjacent branches.

3. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 1, characterized in that: The scrolling window is a 20ms time interval, and one scrolling window contains 20 sampling points, with a time interval of 1ms for each sampling point.

4. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 3, characterized in that: The method for calculating the adjustment deviation is as follows: For any branch, calculate the average output current of the branch and its adjacent branches at the same sampling point, and use it as the adjustment value of the branch at this sampling point. Calculate the difference between the output current of the branch at the same sampling point and the adjustment value, and use it as the adjustment deviation of the branch at this sampling point.

5. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 3, characterized in that: The method for setting the event trigger current threshold is as follows: For any branch, 2% of the rated output current effective value of the branch is taken as its deviation threshold, and 2 / 3 is taken as the single-step pre-trigger deviation ratio. The deviation threshold of the branch, the number of sampling points in the current scrolling window and the single-step pre-trigger deviation ratio are multiplied in sequence to obtain the event trigger current threshold of the branch.

6. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 5, characterized in that: The method for determining whether the absolute difference between the output current of any branch and its adjacent branches meets the adjustment conditions is as follows: If the cumulative deviation of a branch exceeds the event trigger current threshold, the last sampling point in the current scrolling window is taken as the target sampling point. The absolute difference of the output current between the branch and each adjacent branch at the target sampling point is calculated. When the absolute difference of the output current between the branch and each adjacent branch at the target sampling point is greater than the deviation threshold, the branch is judged to meet the adjustment conditions.

7. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 1, characterized in that: The method for synchronously extracting the current equivalent solenoid saturation and reference signal range of this branch is as follows: Extract the instantaneous sampling data of the DC current of the excitation winding of the solenoid body within the current scrolling window, and obtain its fundamental component RMS value and the RMS values ​​of the 3rd, 5th and 7th odd harmonic components through fast Fourier transform decomposition. Calculate the sum of squares of the RMS values ​​of each odd harmonic and take the arithmetic square root to obtain the total RMS value of the harmonics. The ratio of the total RMS value of the harmonics to the fundamental RMS value is used as the equivalent solenoid saturation. The reference signals include voltage and angular frequency reference signals. Only the voltage reference signal range is defined for matching to synchronize the rated phase voltage of the phase-shifting camera. Based on this, multiple consecutive voltage ranges are pre-defined: , , , , or ; Obtain the voltage reference signal of the synchronous modulator within the current scrolling window, and determine the voltage range into which the voltage reference signal falls as the matching reference signal range.

8. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 7, characterized in that: The method for performing a step adjustment on the virtual impedance operating value at a fixed ratio in each subsequent monitoring cycle until the adjustment termination condition is met is as follows: The monitoring period is set to 100ms, and one monitoring period contains 5 rolling windows. For branches that are determined to be adjusted in the current rolling window, no virtual impedance adjustment is performed within the monitoring period to which the current rolling window belongs. Only at the beginning of the next monitoring period, the virtual impedance running value is adjusted in steps according to a fixed ratio. At any moment when step adjustment is performed, if the output current of the branch to be adjusted is greater than the adjustment value, the difference between 1 and a fixed ratio is multiplied by the virtual impedance operating value of the previous monitoring cycle to obtain a new virtual impedance operating value, thereby reducing the virtual impedance operating value. If the output current of the branch to be adjusted is not greater than the adjustment value, the sum of 1 and a fixed ratio is multiplied by the virtual impedance operating value of the previous monitoring cycle to obtain a new virtual impedance operating value, thereby increasing the virtual impedance operating value. The virtual resistance and virtual inductance are adjusted synchronously in the same proportion until the adjustment termination condition is met. The adjustment termination condition is that the absolute difference between the output current of the branch and each adjacent branch at the moment of step adjustment is not greater than the deviation threshold.

9. The overcapacity multi-branch equalization method for a grid-type magnetic valve-type static synchronous condenser according to claim 6, characterized in that: The method for optimizing a fixed ratio is as follows: The sample size trigger threshold is set to be no less than 10. For any historical adjustment round, the equivalent solenoid saturation and reference signal interval in its reference data are extracted and used as the first reference quantity and the second reference quantity, respectively. If the equivalent solenoid saturation in the first reference quantity and the reference data of this round of adjustment fall into the same preset interval, and the reference signal interval in the second reference quantity and the reference data of this round of adjustment are consistent, then it is determined that the reference data of this round of adjustment has appeared repeatedly in the historical adjustment round, and this historical adjustment round is used as the reference adjustment round. Each historical adjustment round is traversed to determine the number of times the reference data of this round of adjustment has appeared repeatedly in previous adjustment rounds. When the number of times the reference data for this round of adjustment has been repeated in previous adjustment rounds exceeds the sample size trigger threshold, the virtual resistance and virtual inductance in the virtual impedance running values ​​recorded in each reference adjustment round are extracted, and the arithmetic mean of all virtual resistances and the arithmetic mean of virtual inductances are calculated respectively, which are used as the target virtual impedance running value for this round of adjustment. The expected convergence step number is preset, and the value of the expected convergence step number is between 1 and 5. First, the current virtual impedance running value of the branch is read, and the total relative change rate of virtual resistance and the total relative change rate of virtual inductance between the current virtual resistance and the target virtual impedance running value are calculated. Then, the total relative change rate is divided equally according to the preset expected convergence step number to obtain the optimized fixed ratio for the next round of adjustment.

10. An overcapacity multi-branch equalization system for a grid-type magnetic valve-type static synchronous condenser, characterized in that: The system is used to perform the overcapacity multi-branch equalization method of the grid-type magnetic valve static synchronous condenser as described in any one of claims 1-9: The reference signal reading module is used to define the adjacent branches of each branch based on the electrical cascading order of each branch of the synchronous condenser, and to obtain the reference signal of each branch of the synchronous condenser in the current scrolling window. The cumulative deviation calculation module is used to read the output current and virtual impedance operating values ​​of any branch at each sampling point in the current rolling window, take the average output current of the branch and the adjacent branches as the adjustment value, calculate the difference between the output current and the adjustment value to determine the adjustment deviation of the branch at each sampling point in the current rolling window, and accumulate the absolute values ​​to obtain the cumulative deviation of the branch. The branch determination module is used to determine whether the absolute difference between the output current of a branch and its adjacent branches meets the adjustment conditions if the cumulative deviation of a branch is greater than the event trigger current threshold. If it does, the branch is defined as the branch to be adjusted. The current equivalent solenoid saturation and reference signal range of the branch are extracted simultaneously as reference data for this round of adjustment, and the average output current of its adjacent branches at the same sampling point is used as its adjustment value. The virtual impedance optimization module is used to perform a step adjustment on the virtual impedance operating value of any branch defined as to be adjusted in each subsequent monitoring cycle by a fixed proportion until the adjustment termination condition is met. It determines whether the number of times the reference data of this round of adjustment has been repeated in previous adjustment rounds is greater than the sample size trigger threshold. If it is greater, it optimizes the fixed proportion based on the virtual impedance operating value when the current round of adjustment is completed.

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