A Low-Voltage Reactive Power Compensation Network and Control Method

Abstract

This invention relates to a low-voltage reactive power compensation networking and control method. The networking scheme adopts a master-slave configuration, with two types of networking: re-networking and subsequent addition of networks. The master unit collects data through polling commands. In terms of control, it includes three aspects: data analysis, compensation control, and cyclic switching. Through in-depth analysis of the collected data, the basic parameters and historical usage of the slave units are comprehensively considered to accurately calculate the optimal compensation scheme. In addition, a cyclic working mode is designed to allow the slave units to operate in turn, maintaining balanced use and extending service life.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation technology, and in particular to a low-voltage reactive power compensation network and control method. Background Technology

[0002] Traditional reactive power compensation systems use contactors as switches to switch capacitors, employing a three-phase simultaneous compensation method, which has many drawbacks. The workflow of a low-voltage reactive power compensation controller mainly focuses on networking and compensation control.

[0003] Currently available controllers and networking solutions have numerous problems, such as excessively long networking times, untimely slave device responses, frequent disconnections, and data corruption after slave device replacement. Compensation control schemes have even more drawbacks. First, due to the series reactance of capacitors and their attenuation during use, theoretical calculations deviate from actual values, leading to either excessive or insufficient compensation. This results in more frequent compensation actions, impacting the lifespan of the capacitors and the overall circuitry. Second, improper compensation prioritization can cause imbalances in the operating time of capacitors from the same batch, leading to increasingly greater differences in attenuation over time. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a low-voltage reactive power compensation networking and control method. In terms of networking, a master-slave configuration is adopted, with the master collecting data through polling commands. In terms of control, the collected data is analyzed in depth, and the basic parameters and historical usage of the slaves are comprehensively considered to accurately calculate the optimal compensation scheme. In addition, a cyclic working mode is designed to allow the slaves to operate in turn, maintain balanced use, and extend service life.

[0005] The objective of this invention is achieved as follows: A low-voltage reactive power compensation networking and control method is disclosed. The networking method is as follows: Networking begins with the host sending a broadcast networking command and waiting for responses from the slave devices. The host waits for a certain period, during which all responding slave devices are recorded. If the timeout period expires, it is assumed that no more slave devices are responding. The host then begins assigning addresses to these slave devices sequentially according to the order of their responses. Once all slave devices have established addresses, the networking process is complete. After networking is complete, the host sends polling commands to the slave devices to read data. The control method comprises three parts: data analysis, compensation control, and cyclic switching. Data Analysis Section: After the network is set up, the host will record the basic parameter information of the slave capacitors, and calculate the actual capacity of each capacitor based on the parameter information. Then, according to the user-defined rules, all capacitors are classified and sorted to build a capacitor pool. After the capacitor pool is initially built, all capacitors are set to an idle state by default. After the master starts polling, it updates the status of the capacitors in the capacitor pool periodically based on the data replied by each slave. During polling, if a slave fails to respond three times in a row, the master marks it as disconnected and returns it to normal status after it responds. Slave capacitors with abnormal status will not become candidate capacitors for compensation control. Compensation and control section: In the entire compensation control process, fault detection has the highest priority. Once a circuit fault is detected, the host will immediately execute the cut-off command. According to the user-defined logic, the individual compensation capacitors are cut off first, followed by the common compensation capacitors; the smaller capacity capacitors are cut off first, followed by the larger capacity capacitors; the capacitors that were put into operation first are cut off first, followed by the capacitors that were put into operation last. If the fault is detected to have been recovered during the cut-off process, the cut-off command is stopped, and the compensation detection process begins.

[0006] During compensation testing, the system first checks for insufficient compensation and then checks for overcompensation. After calculating the capacity for insufficient or overcompensated compensation, it starts searching the capacitor pool to find the capacitor with the most suitable capacity. Once found, the system does not execute the test immediately but continues to search the capacitor pool to determine if there are any capacitors with the same capacity. If so, it compares their usage time to find the most suitable one. Cyclic switching section: During normal operation, the system performs a cyclic switching function. When it detects that the activation time of a certain capacitor has reached the set cycle value, it will search the capacitor pool to determine if there are any capacitors of equal capacity that have not been activated. After finding one, it will not execute the switch immediately, but will continue to search the capacitor pool to determine if there are any capacitors of equal capacity. If so, it will compare their usage time to find the most suitable one. Finally, it will execute the cyclic switching action, first disconnecting and then activating the capacitor.

[0007] A low-voltage reactive power compensation networking and control method, the process steps of which are as follows: Start setting up the network; The host sends a broadcast network formation command; if the network formation times out, the process ends. If only the network formation timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network formation is obtained → the slave address is established → the slave index is set to 0 → the process ends. If only the network formation timeout occurs and no response is received, the process ends directly. If the network formation timeout has not occurred, then re-form the network → clear the network information → automatically form the network → reset the slave count to zero → broadcast the network formation command → automatic network formation timeout → end; If the re-networking timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network is obtained → the slave address is established → the slave index is set to 0 → the process ends. If no response is received, the process ends directly. If the re-networking does not time out, then add a new network → clear network information → obtain the number of slave devices in the last network → broadcast the command to add a new network → add a new network timeout → end; If the subsequent network formation times out, if a response is received, the receive timeout flag is set to 0 → obtain the number of networked slave devices → establish slave device address → set slave device index to 0 → end; if no response is received, the process ends directly. If the subsequent network addition does not time out, then the process is as follows: establish slave address → assign address to master → slave address establishment timeout → end; If the slave address establishment times out, and a response is received, the receive timeout flag is set to 0 → the slave index is incremented → if the slave index is greater than the total number of slaves → if the reset flag is 1 → broadcast cut-off → the slave index is set to 0 → end. If the reset flag is not 1 → poll → the slave index is set to 0 → end. If the slave index is not greater than the total number of slaves → establish a slave address → end. If no response is received, the process ends directly. Finish.

[0008] A low-voltage reactive power compensation network and control method, wherein the process steps of the compensation control section are as follows: If the controller has an overvoltage or undervoltage fault → disconnect all capacitors → disconnect one capacitor, and put the disconnected capacitors into a discharge state → check if the fault persists → if the fault is recovered, stop disconnecting → end. If the controller does not have overvoltage or undervoltage faults, check the power factor PFA, PFB, and PFC. Then determine whether all three phases meet the requirements (less than the target value or greater than 1) → If none of them meet the requirements, calculate the required capacitors to be added / removed → Find the most suitable common compensation capacitor in the capacitor pool → If a suitable common compensation capacitor is found → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End; If no suitable common compensation capacitor is found → Find the most suitable individual compensation capacitor in the capacitor pool → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End. If one or two phases do not meet the requirements → calculate the required capacitors to be added / removed → find the most suitable supplementary capacitor in the corresponding capacitor pool → add / remove → set the added capacitor to the working state and add it to the working capacitor pool, set the removed capacitor to the discharging state → end. If all requirements are met, the process ends directly.

[0009] A low-voltage reactive power compensation network and control method, wherein the process steps of the cyclic switching section are as follows: Query the working capacitor pool → If the working capacitor's cycle switching time has not expired, end the process; if the working capacitor's cycle switching time has expired, find the capacitor with the longest working time in this process. If no replacement was found in the previous step, skip this capacitor and return to the previous step to find the capacitor with the longest working time in this process. If a replacement was found last time, the query can add it to the capacitor pool; Determine if there are capacitors with equal capacity. If there are capacitors with equal capacity, find the one with the longest idle time. Switching will start soon. Turn off compensation detection. Disconnect the capacitor and set its status to discharge. Connect the capacitor and set its status to working. Add it to the working capacitor pool. Switching cycle is complete. Start compensation detection. End. If there is no equal capacity, the process ends directly.

[0010] Compared with the prior art, the beneficial effects of the present invention are: (1) The networking method of the present invention greatly improves the success rate and efficiency of networking, and also handles the added slave devices very well. There is corresponding feedback for all networking situations, which improves the user experience overall.

[0011] (2) In the compensation calculation of the present invention, not only the inherent capacitance of the capacitor is referenced, but also the series reactance rate and attenuation degree are combined to calculate the closest value, thus ensuring the accuracy of each compensation, greatly reducing invalid compensation and erroneous compensation, extending the service life of the capacitor, and ensuring the stability of the circuit.

[0012] (3) The compensation control of this invention has a slave cyclic operation mechanism that replaces the slave capacitors on time to ensure that all capacitors work in a balanced manner, thus guaranteeing overall stability and longevity.

[0013] (4) In the event of a sudden failure, the present invention has a set of slave device disconnection sequence logic to ensure both circuit safety and capacitor safety. Attached Figure Description

[0014] Figure 1 This is a flowchart of the networking method of the present invention.

[0015] Figure 2 This is a flowchart of the compensation control method of the present invention.

[0016] Figure 3 This is a flowchart of the cyclic switching method of the present invention. Implementation

[0017] To better understand the technical solution of the present invention, a detailed description will be provided below in conjunction with relevant illustrations. It should be understood that the specific embodiments described below are not intended to limit the specific implementation of the technical solution of the present invention, but are merely possible implementations of the technical solution of the present invention. It should be noted that the descriptions of the positional relationships of the components herein, such as component A being located above component B, are based on the relative positions of the components in the illustrations and are not intended to limit the actual positional relationships of the components. Example 1

[0018] See Figure 1-3 , Figure 1A flowchart of a low-voltage reactive power compensation network method is presented. As shown in the figure, the low-voltage reactive power compensation network and control method of this invention includes a low-voltage reactive power compensation network method and a control method. The networking method is as follows: To begin networking, the host sends a broadcast networking command and waits for responses from the slave devices. The host waits for a certain period, during which all responding slave devices are recorded; if the timeout period expires, it is assumed that no more slave devices are responding. Then, the host begins assigning addresses to these slave devices, assigning them sequentially according to the order of response. Once all slave devices have established addresses, the networking process is complete. After networking is complete, the host sends polling commands to the slave devices to read data. This includes the following specific steps: Start setting up the network; The host sends a broadcast network formation command; if the network formation times out, the process ends. If only the network formation timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network formation is obtained → the slave address is established → the slave index is set to 0 → the process ends. If only the network formation timeout occurs and no response is received, the process ends directly. If the network formation timeout has not occurred, then re-form the network → clear the network information → automatically form the network → reset the slave count to zero → broadcast the network formation command → automatic network formation timeout → end; If the re-networking timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network is obtained → the slave address is established → the slave index is set to 0 → the process ends. If no response is received, the process ends directly. If the re-networking does not time out, then add a new network → clear network information → obtain the number of slave devices in the last network → broadcast the command to add a new network → add a new network timeout → end; If the subsequent network formation times out, if a response is received, the receive timeout flag is set to 0 → obtain the number of networked slave devices → establish slave device address → set slave device index to 0 → end; if no response is received, the process ends directly. If the subsequent network addition does not time out, then the process is as follows: establish slave address → assign address to master → slave address establishment timeout → end; If the slave address establishment times out, and a response is received, the receive timeout flag is set to 0 → the slave index is incremented → if the slave index is greater than the total number of slaves → if the reset flag is 1 → broadcast cut-off → the slave index is set to 0 → end. If the reset flag is not 1 → poll → the slave index is set to 0 → end. If the slave index is not greater than the total number of slaves → establish a slave address → end. If no response is received, the process ends directly. Finish.

[0019] The overall networking scheme is a master-slave mode, and the networking is divided into two types: re-networking and subsequent addition networking. Re-networking means clearing the existing networking information and starting the networking process for all slaves. Subsequent addition networking means adding new slaves based on the existing networking information.

[0020] See Figure 2-3 Its control method includes three parts: data analysis, compensation control, and cyclic switching. Data Analysis Section: After the network is set up, the host records the basic parameter information of the slave capacitors, including capacitor type, rated capacity, series reactance rate, and cumulative operating time. Based on these parameters, the actual capacity of each capacitor is calculated. Then, according to user-defined rules, all capacitors are classified and sorted to create a capacitor pool. After the initial construction of the capacitor pool, all capacitors are set to an idle state by default. After the master unit initiates polling, it periodically updates the capacitor status in the capacitor pool based on the data returned by each slave unit. During polling, if a slave unit fails to respond three times consecutively, the master unit marks it as disconnected and returns it to normal status once it responds. Slave capacitors with abnormal status will not become candidate capacitors during compensation control, thus ensuring that every switching command is meaningful and greatly reducing unnecessary waiting time.

[0021] Compensation and control section: The compensation process involves real-time monitoring of reactive power in the power grid. If the reactive power is below the target value, compensation is initiated; if it is above the limit value, over-compensation is cut off. Priority processing and compensation logic are implemented throughout the entire operation process. In the entire compensation control process, fault detection has the highest priority. Once a circuit fault is detected, the host will immediately execute a disconnection command. According to the predefined logic, the individual compensation capacitors are disconnected first, followed by the common compensation capacitors; smaller capacity capacitors are disconnected first, followed by larger capacity capacitors; and those connected earlier are disconnected first, followed by those connected later. If the fault is detected to have been recovered during the disconnection process, the disconnection command is stopped, and the compensation detection process begins.

[0022] During compensation testing, the system first checks for insufficient compensation and then for overcompensation. After calculating the capacitance for insufficient or overcompensated capacitors, it begins searching the capacitor pool to find the capacitor with the most suitable capacitance. Once found, the system does not execute the test immediately but continues searching the capacitor pool to see if there are any capacitors with the same capacitance. If so, the system compares their usage time to find the most suitable one.

[0023] See Figure 2 The specific steps of the compensation process are as follows: If the controller has an overvoltage or undervoltage fault → disconnect all capacitors → disconnect one capacitor, and put the disconnected capacitors into a discharge state → check if the fault persists → if the fault is recovered, stop disconnecting → end. If the controller does not have overvoltage or undervoltage faults, check the power factor PFA, PFB, and PFC. Then determine whether all three phases meet the requirements (less than the target value or greater than 1) → If none of them meet the requirements, calculate the required capacitors to be added / removed → Find the most suitable common compensation capacitor in the capacitor pool → If a suitable common compensation capacitor is found → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End; If no suitable common compensation capacitor is found → Find the most suitable individual compensation capacitor in the capacitor pool → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End. If one or two phases do not meet the requirements → calculate the required capacitors to be added / removed → find the most suitable supplementary capacitor in the corresponding capacitor pool → add / remove → set the added capacitor to the working state and add it to the working capacitor pool, set the removed capacitor to the discharging state → end. If all requirements are met, the process ends directly.

[0024] Cyclic switching section: During normal operation, the system performs a cyclic switching function. When it detects that the activation time of a certain capacitor has reached the set cycle value, it will search the capacitor pool to see if there are any capacitors of equal capacity that have not been activated. After finding one, it will not execute the switch immediately, but will continue to search the capacitor pool to see if there are any capacitors of equal capacity. If so, it will compare their usage time to find the most suitable one. Finally, it will execute the cyclic switching action, first disconnecting and then activating the capacitor.

[0025] See Figure 3 The specific steps for cyclic switching are as follows: Query the working capacitor pool → If the working capacitor's cycle switching time has not expired, end the process; if the working capacitor's cycle switching time has expired, find the capacitor with the longest working time in this process. If no replacement was found in the previous step, skip this capacitor and return to the previous step to find the capacitor with the longest working time in this process. If a replacement was found last time, the query can add it to the capacitor pool; Determine if there are capacitors with equal capacity. If there are capacitors with equal capacity, find the one with the longest idle time. Switching will start soon. Turn off compensation detection. Disconnect the capacitor and set its status to discharge. Connect the capacitor and set its status to working. Add it to the working capacitor pool. Switching cycle is complete. Start compensation detection. End. If there is no equal capacity, the process ends directly.

[0026] The above are merely specific application examples of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent transformations or substitutions fall within the scope of protection of the present invention.

Claims

1. A low-voltage reactive power compensation network and control method, characterized in that: The networking method is as follows: To start networking, the host sends a broadcast networking command and waits for responses from the slave devices; the host will wait for a certain period of time, during which all responding slave devices will be recorded, and if the timeout occurs, it is assumed that no slave devices will respond; then the host begins to assign addresses to these slave devices, assigning them sequentially according to the order of response; after all slave devices have established addresses, the networking process is complete; after networking is completed, the host sends polling commands to the slave devices to read data; The control method comprises three parts: data analysis, compensation control, and cyclic switching. Data Analysis Section: After the network is set up, the host will record the basic parameter information of the slave capacitors, and calculate the actual capacity of each capacitor based on the parameter information. Then, according to the user-defined rules, all capacitors are classified and sorted to build a capacitor pool. After the capacitor pool is initially built, all capacitors are set to an idle state by default. After the host starts polling, it updates the status of the capacitors in the capacitor pool periodically based on the data replied by each slave. During the polling process, if a slave device fails to respond three times in a row, the master device marks it as disconnected and returns it to normal status once it responds. Slave capacitors that are in an abnormal state will not be considered as candidate capacitors for compensation control. Compensation and control section: In the entire compensation control process, fault detection has the highest priority. Once a circuit fault is detected, the host will immediately execute a disconnection command. According to the user-defined logic, the individual compensation capacitors are disconnected first, followed by the common compensation capacitors; smaller capacity capacitors are disconnected first, followed by larger capacity capacitors; and those connected earlier are disconnected first, followed by those connected later. If the fault is detected to have been recovered during the disconnection process, the disconnection command is stopped, and the compensation detection process begins. During compensation testing, first test for missing fillers, then test for overfillers; After calculating the missing or over-compensated capacity, the capacitor pool is searched to find the capacitor with the most suitable capacity. After finding it, the process is not executed immediately, but the search continues to check if there is a capacitor with the same capacity. If so, their usage time is compared to find the most suitable one. Cyclic switching section: During normal operation, the system performs a cyclic switching function. When it detects that the activation time of a certain capacitor has reached the set cycle value, it will search the capacitor pool to determine if there are any capacitors of equal capacity that have not been activated. After finding one, it will not execute the switch immediately, but will continue to search the capacitor pool to determine if there are any capacitors of equal capacity. If so, it will compare their usage time to find the most suitable one. Finally, it will execute the cyclic switching action, first disconnecting and then activating the capacitor.

2. The low-voltage reactive power compensation networking and control method according to claim 1, characterized in that, The networking method has the following steps: Start setting up the network; The host sends a broadcast network formation command; if the network formation times out, the process ends. If only the network formation timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network formation is obtained → the slave address is established → the slave index is set to 0 → the process ends. If only the network formation timeout occurs and no response is received, the process ends directly. If the network formation timeout has not occurred, then re-form the network → clear the network information → automatically form the network → reset the slave count to zero → broadcast the network formation command → automatic network formation timeout → end; If the re-networking timeout occurs, and a response is received, the reset flag is set to 1 → the receive timeout flag is set to 0 → the number of slave devices in the last network is obtained → the slave address is established → the slave index is set to 0 → the process ends. If no response is received, the process ends directly. If the re-networking does not time out, then add a new network → clear network information → obtain the number of slave devices in the last network → broadcast the command to add a new network → add a new network timeout → end; If the subsequent network formation times out, if a response is received, the receive timeout flag is set to 0 → obtain the number of networked slave devices → establish slave device address → set slave device index to 0 → end; if no response is received, the process ends directly. If the subsequent network addition does not time out, then the process is as follows: establish slave address → assign address to master → slave address establishment timeout → end; If the slave address establishment times out, and a response is received, the receive timeout flag is set to 0 → the slave index is incremented → if the slave index is greater than the total number of slaves → if the reset flag is 1 → broadcast cut-off → the slave index is set to 0 → end. If the reset flag is not 1 → poll → the slave index is set to 0 → end. If the slave index is not greater than the total number of slaves → establish a slave address → end. If no response is received, the process ends directly. Finish.

3. The low-voltage reactive power compensation networking and control method according to claim 1, characterized in that: The process steps of the compensation control section are as follows: If the controller has an overvoltage or undervoltage fault → disconnect all capacitors → disconnect one capacitor, and put the disconnected capacitors into a discharge state → check if the fault persists → if the fault is recovered, stop disconnecting → end. If the controller does not have overvoltage or undervoltage faults, check the power factor PFA, PFB, and PFC. Then determine whether all three phases meet the requirements (less than the target value or greater than 1) → If none of them meet the requirements, calculate the required capacitors to be added / removed → Find the most suitable common compensation capacitor in the capacitor pool → If a suitable common compensation capacitor is found → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End; If no suitable common compensation capacitor is found → Find the most suitable individual compensation capacitor in the capacitor pool → Add / remove → Set the added capacitor to the working state and add it to the working capacitor pool, and set the removed capacitor to the discharging state → End. If one or two phases do not meet the requirements → calculate the required capacitors to be added / removed → find the most suitable supplementary capacitor in the corresponding capacitor pool → add / remove → set the added capacitor to the working state and add it to the working capacitor pool, set the removed capacitor to the discharging state → end. If all requirements are met, the process ends directly.

4. The low-voltage reactive power compensation networking and control method according to claim 1, characterized in that: The process steps of the cyclic switching section are as follows: Query the working capacitor pool → If the working capacitor's cycle switching time has not expired, end the process; if the working capacitor's cycle switching time has expired, find the capacitor with the longest working time in this process. If no replacement was found in the previous step, skip this capacitor and return to the previous step to find the capacitor with the longest working time in this process. If a replacement was found last time, the query can add it to the capacitor pool; Determine if there are capacitors with equal capacity. If there are capacitors with equal capacity, find the one with the longest idle time. Switching will start soon. Turn off compensation detection. Disconnect the capacitor and set its status to discharge. Connect the capacitor and set its status to working. Add it to the working capacitor pool. Switching cycle is complete. Start compensation detection. End. If there is no equal capacity, the process ends directly.

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