Electric energy quality autonomous system and method for solving distributed photovoltaic grid connection problem

Abstract

The invention relates to the technical field of power equipment, in particular to an electric energy quality autonomous system and method for solving a distributed photovoltaic grid connection problem. A data acquisition module comprises a low-voltage electric energy meter and an intelligent switch and is used for acquiring operation data of a transformer area; the control strategy module comprises a master station of a transformer area and is used for data acquisition and algorithm control; the action adjusting module comprises a transformer area side device and a line side device, wherein the transformer area side device comprises an on-load voltage regulating transformer, an intelligent capacitor and a photovoltaic inverter; and the line side equipment comprises an active unbalance compensation device, a steady-state reactive generator and a distributed energy storage device. Through cooperative work of the data acquisition module, the control strategy module and the adjustment action module, real-time monitoring and automatic adjustment of the distributed photovoltaic grid connection problem are achieved, the electric energy quality problems of voltage out-of-limit, three-phase imbalance, reactive compensation and the like of transformer area side equipment are effectively solved, and the stability and efficiency of power grid operation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power equipment, and in particular to a power quality autonomous system and method for coping with distributed photovoltaic grid-connected problems. Background Art

[0002] When low-voltage distributed photovoltaics are connected to rural power grids, voltage often exceeds the limit. In order to ensure power generation efficiency, photovoltaic users set the inverter output voltage higher than the grid voltage, causing overvoltage at the end of the low-voltage line, and the voltage at some grid connection points even reaches 290 volts. After sunset, photovoltaic power generation decreases, user load increases, and low voltage appears at the end of the line, forming a phenomenon of voltage anomalies, which is difficult to solve with traditional methods. This not only affects the quality of electricity used by residents, but also causes the voltage qualification rate to fail to meet the standard. To solve this problem, existing technologies such as the CN110071579A patent propose a power grid security system based on the ubiquitous power Internet of Things, which is intelligently managed through data collection, analysis and decision-making control. However, the system still faces challenges: problems such as voltage exceeding the limit of equipment on the substation side, three-phase imbalance and reactive power compensation may not be solved in a timely and effective manner, resulting in a decline in the power quality of the power grid; the control strategy formulation lacks flexibility, and it is difficult to make precise adjustments based on data regional differences; the refined management and optimization means are insufficient, and the power quality autonomy effect is limited, making it difficult to meet the growth of power grid operation needs. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a power quality autonomous system and method for coping with distributed photovoltaic grid-connected problems.

[0004] The technical solution adopted by the present invention is as follows: An autonomous power quality system for dealing with distributed photovoltaic grid-connected problems, including modules: The data acquisition module includes a low-voltage energy meter and an intelligent switch, which are used to collect the operation data of the substation. The vertical data acquisition uses five levels of transformer operation data, including low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter. The horizontal data acquisition uses photovoltaic, charging piles, and energy storage devices to achieve hierarchical real-time monitoring. The collected data is transmitted to the control strategy module through the carrier communication unit. The control strategy module includes a master station in the substation area, which is used for data acquisition and algorithm control. It obtains the operating parameters in the data acquisition module through the carrier communication unit, and deploys the nine-domain adjustment algorithm to automatically analyze and decouple the voltage limit problem of the substation side equipment. When a power quality problem is detected, the control strategy module sends a signal to the adjustment action module to control the adjustment action module to make corresponding adjustments. The adjustment action module includes the equipment on the substation side and the equipment on the line side, including: The equipment on the substation side includes on-load tap-changing transformers, smart capacitors and photovoltaic inverters, including: On-load tap-changing transformer, gear adjustment is realized through RS-485 communication unit; Intelligent capacitors can be switched in groups through RS-485 communication unit; Photovoltaic inverter, which achieves flexible regulation through type I concentrator and protocol converter; Line-side equipment, including active unbalanced compensation devices, steady-state reactive power generators and distributed energy storage devices, including: Active unbalanced compensation device and steady-state reactive power generator are installed on low-voltage branch lines respectively to treat three-phase unbalanced problems and compensate reactive power; Distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

[0005] This technical solution realizes the collection and analysis of substation operation data and automatic adjustment of power quality. Specifically, the data acquisition module ensures the comprehensiveness and accuracy of the data through the collection of low-voltage energy meters and intelligent switches, as well as the operation data of multi-stage transformers. It not only covers the operation parameters of traditional power grids, but also pays special attention to the status of new energy equipment such as photovoltaics, charging piles, and energy storage devices, so as to reflect the actual operation of the power grid in real time and accurately. The control strategy module uses the nine-domain adjustment algorithm to analyze and process the collected data through the intelligent fusion terminal, and can automatically analyze and decouple the voltage limit of the equipment on the substation side, and formulate corresponding control strategies according to the nature and severity of the problem. The adjustment action module includes substation side equipment and line side equipment, and realizes precise adjustment through different communication methods, such as RS-485 communication unit, type I concentrator and protocol converter. For example, the on-load tap-changing transformer changes the voltage level by adjusting the gear, the intelligent capacitor compensates for reactive power by group switching, and the photovoltaic inverter optimizes the output of photovoltaic power generation through flexible adjustment. The whole system realizes comprehensive management of the power quality problems caused by distributed photovoltaic grid connection through the close cooperation of the three modules of data acquisition, control strategy and adjustment action.

[0006] In addition, the power quality autonomous system and method for coping with distributed photovoltaic grid-connected problems according to the present invention also have the following additional technical features: According to one embodiment of the present invention, the longitudinal data collection of the data collection module includes: The low-voltage main switch is connected to the main line of the power grid and is used to provide power to the entire substation area; Branch switches, which are separated from the low-voltage main switch, are used to control the power supply of different branches; Low-voltage distribution box, which connects power lines of different branches and is used to distribute electricity; Meter box installation, on the branch line, each meter box contains multiple household meters for measuring the user's energy consumption; Household meters are installed directly at the user end to record the user's individual energy consumption; The horizontal data collection of the data collection module includes: Photovoltaic equipment, charging piles and energy storage devices are respectively connected to the substation power grid to realize energy input, output and storage.

[0007] This technical solution ensures that the system can fully obtain the operating data of the substation power grid through the vertical and horizontal data collection methods of the data collection module.

[0008] According to one embodiment of the present invention, the low-voltage energy meter and the intelligent switch of the data acquisition module are installed at different levels of the power grid in the substation area to collect operation data; The data collected by the data acquisition module is transmitted to the control strategy module through the carrier communication unit, using the power line as the communication medium; after receiving the data, the control strategy module analyzes and processes it to formulate and optimize the power grid operation strategy.

[0009] This technical solution realizes real-time data collection and formulation and optimization of power grid operation strategies by utilizing a carrier communication unit to transmit data to a control strategy module.

[0010] According to one embodiment of the present invention, the nine-domain regulation algorithm deployed by the control strategy module constructs a coordinate curve diagram of reactive power Q and voltage U, and uses the limit values ​​of reactive power Q and voltage U to divide the entire coordinate curve diagram into nine basic areas, and further subdivide it into 17 specific areas, each area corresponding to a different control strategy.

[0011] This technical solution constructs a coordinate curve diagram and divides the regions through the nine-domain adjustment algorithm deployed by the control strategy module to formulate different control strategies.

[0012] According to an embodiment of the present invention, the nine-domain adjustment algorithm deployed by the control strategy module has control strategies for 17 specific regions as follows: Zone 1: The characteristic is that the reactive power exceeds the lower limit, and the voltage exceeds the upper limit; the control strategy is to cut off the capacitor bank and adjust the inverter; Zone 2: The characteristics are that the reactive power approaches the lower limit and the voltage exceeds the upper limit; the control strategy is to cut off the capacitor bank and adjust the inverter; Zone 3: The characteristics are that the reactive power is normal and the voltage exceeds the upper limit; the control strategy is to reduce the tap, cut the capacitor, and adjust the inverter; Zone 4, the characteristics are reactive power approaching the upper limit, and the voltage exceeds the upper limit; the control strategy is to reduce the tap; Zone 5: The characteristics are that the reactive power exceeds the upper limit, and the voltage exceeds the upper limit; the control strategy is to reduce the tap. If it is at the lowest level, the capacitor bank is forcibly cut off; Zone 6: The characteristics are that the reactive power exceeds the lower limit and the voltage approaches the upper limit; the control strategy is to cut the capacitor bank, and if the capacitor can be cut, it is maintained; Zone 7: The characteristics are that the reactive power exceeds the upper limit and the voltage approaches the upper limit; the control strategy is to first reduce the tap and then invest in the capacitor bank, otherwise maintain; Zone 8, the characteristics are reactive power exceeding the lower limit, and the voltage is normal; the control strategy is to cut off the capacitor bank and increase the tap; Zone 9: The characteristics are in compliance with the operating requirements; the control strategy is no action, maintain the current state; Zone 10, the characteristic is that the reactive power exceeds the upper limit, and the voltage is normal; the control strategy is to invest capacitors and reduce the tap: if no capacitors are invested, it is maintained; Zone 11, the characteristics are reactive power exceeding the lower limit and voltage approaching the lower limit; the control strategy is tap increase; Zone 12: The characteristics are that the reactive power exceeds the upper limit and the voltage approaches the lower limit; the control strategy is to invest in capacitors, and if there is no investment, it is maintained; Zone 13, the characteristic is that the reactive power is lower than the lower limit, the voltage is lower than the lower limit; the control strategy is the tap increase; Zone 14, the characteristics are reactive power approaching the lower limit, and the voltage exceeds the lower limit; the control strategy is to increase the tap, and if it has reached the maximum level, the capacitor is forced to be added; Zone 15, the characteristics are normal reactive power and voltage exceeding the lower limit; the control strategy is to increase the tap and invest in capacitors; Zone 16, the characteristics are that reactive power approaches the upper limit and voltage exceeds the lower limit; the control strategy is to inject capacitors; Zone 17: The characteristic is that the reactive power exceeds the upper limit, and the voltage exceeds the upper limit; the control strategy is to inject capacitors.

[0013] This technical solution provides specific operational guidance for the power quality autonomous system by listing the control strategies for 17 specific areas in detail.

[0014] According to one embodiment of the present invention, the substation side equipment of the adjustment action module is located near the distribution transformer of the power system; the on-load tap-changing transformer and the smart capacitor of the substation side equipment are connected to the distribution system through power lines; the photovoltaic inverter of the substation side equipment receives solar energy through photovoltaic panels and converts it into electrical energy, and then connects to the distribution system through power lines; The line-side equipment of the adjustment action module is distributed in the low-voltage branch lines and pre-meter branches of the power system; the active unbalance compensation device and steady-state reactive power generator of the line-side equipment are installed at different positions of the low-voltage branch lines to control three-phase imbalance problems and perform reactive power compensation; the distributed energy storage device of the line-side equipment is installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

[0015] This technical solution ensures that the system can effectively solve power quality problems by adjusting the distribution and functions of the substation-side equipment and line-side equipment of the action module.

[0016] According to one embodiment of the present invention, the on-load tap-changing transformer, smart capacitor and photovoltaic inverter of the substation side equipment together constitute an intelligent fusion terminal, wherein: The photovoltaic inverter converts the direct current generated by the distributed photovoltaic power source into alternating current and adjusts the output power according to the grid demand and photovoltaic power generation situation; the smart capacitor detects the reactive power demand in the grid in real time and automatically adjusts its group switching status to provide the necessary reactive power compensation and improve the power factor of the grid; the on-load voltage-changing transformer automatically adjusts its gear according to the changes in the grid voltage to maintain the stability of the grid voltage.

[0017] This technical solution improves the power factor and voltage stability of the power grid through the coordinated work of equipment on the substation side.

[0018] To achieve the above objectives, the present invention also provides a power quality autonomy method for dealing with distributed photovoltaic grid-connected problems.

[0019] A power quality autonomy method for dealing with distributed photovoltaic grid-connected problems includes the following steps: S1. Data acquisition and processing: The data acquisition module collects data from the low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter in the vertical direction through the low-voltage electric energy meter and intelligent switch; at the same time, it collects energy input, output, and storage data of photovoltaic equipment, charging piles, and energy storage devices in the horizontal direction; the collected data is transmitted to the control strategy module through the carrier communication unit; S2. Control strategy processing: After receiving the data, the control strategy module deploys the nine-domain regulation algorithm for analysis, constructs a coordinate curve diagram of reactive power Q and voltage U, and divides it into nine basic areas and 17 specific areas. Different control strategies are formulated according to the area where the data is located; when a power quality problem is detected, the control strategy module sends a signal to the adjustment action module; where: S21, Substation side processing: The on-load tap-changing transformer adjusts the gear through the RS-485 communication unit to keep the grid voltage stable; the smart capacitors are switched in groups through the RS-485 communication unit to provide reactive power compensation; the photovoltaic inverter achieves flexible regulation through the type I concentrator and protocol converter to adjust the output power; S22, line-side processing: Active unbalanced compensation devices and steady-state reactive power generators are installed on low-voltage branch lines to manage three-phase unbalance problems and perform reactive power compensation; distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics; S3, Feedback and optimization: After the adjustment action module executes the control strategy, the execution result is fed back to the control strategy module; the control strategy module optimizes the grid operation strategy according to the feedback result to achieve autonomy of power quality.

[0020] This technical solution realizes the whole process of data collection, control strategy processing, adjustment action execution, feedback and optimization, and ensures the autonomy of power quality. Specifically, through the data acquisition and processing module, it uses low-voltage electric energy meters and intelligent switches to vertically collect data from the low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter in the substation area, and horizontally collects energy data from photovoltaic equipment, charging piles, and energy storage devices, and transmits these data to the control strategy module through the carrier communication unit; the control strategy module receives these data, deploys the nine-domain adjustment algorithm for analysis, divides the data into different areas according to the coordinate curve diagram of reactive power Q and voltage U, and then formulates targeted control strategies. When a power quality problem is detected, the control strategy module sends a signal to the adjustment action module, and the power grid is adjusted and optimized in many aspects through the on-load tap-changing transformer, intelligent capacitor and photovoltaic inverter on the substation side, and the active unbalanced compensation device, steady-state reactive power generator and distributed energy storage device on the line side; the adjustment action module feeds back the execution results to the control strategy module, and the control strategy module optimizes the power grid operation strategy according to the feedback results, thereby realizing the autonomy of power quality.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) Through the coordinated work of the data acquisition module, the control strategy module and the adjustment action module, real-time monitoring and automatic adjustment of distributed photovoltaic grid-connected problems can be achieved, effectively solving power quality problems such as voltage over-limit, three-phase imbalance and reactive power compensation on the substation side, and improving the stability and efficiency of power grid operation.

[0022] (2) By deploying the nine-domain regulation algorithm, the coordinate curves of reactive power Q and voltage U are divided into multiple specific areas, and different control strategies are formulated according to the areas where the data is located, so as to achieve refined management and optimization of the grid operation status and improve the accuracy and effect of power quality autonomy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow diagram of the method of the present invention.

[0024] Figure 2 It is a schematic diagram of the connection structure of the system of the present invention.

[0025] Figure 3 It is the distribution map of 17 specific regions of the nine-domain adjustment algorithm.

[0026] In the figure: 1. Data acquisition module; 2. Control strategy module; 3. Adjustment action module. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1 like Figures 1 to 3 As shown, this embodiment provides a power quality autonomous system for dealing with distributed photovoltaic grid-connected problems, including modules: Data acquisition module 1, including low-voltage electric energy meter and intelligent switch, is used to collect the operation data of the substation; it adopts five levels of transformer operation data acquisition vertically, and the transformer levels include low-voltage main switch, branch switch, low-voltage tap box, meter box, and household meter; it adopts photovoltaic, charging pile, and energy storage device horizontally to realize hierarchical real-time monitoring; the collected data is transmitted to control strategy module 2 through carrier communication unit; The control strategy module 2 includes a master station in the substation area, which is used for data acquisition and algorithm control. It obtains the operating parameters in the data acquisition module 1 through the carrier communication unit, and deploys the nine-domain adjustment algorithm to automatically analyze and decouple the voltage limit problem of the substation side equipment; when a power quality problem is detected, the control strategy module 2 sends a signal to the adjustment action module 3, and controls the adjustment action module 3 to make corresponding adjustments; The adjustment action module 3 includes the equipment on the substation side and the equipment on the line side, wherein: The equipment on the substation side includes on-load tap-changing transformers, smart capacitors and photovoltaic inverters, including: On-load tap-changing transformer, gear adjustment is realized through RS-485 communication unit; Intelligent capacitors can be switched in groups through RS-485 communication unit; Photovoltaic inverter, which achieves flexible regulation through type I concentrator and protocol converter; Line-side equipment, including active unbalanced compensation devices, steady-state reactive power generators and distributed energy storage devices, including: Active unbalanced compensation device and steady-state reactive power generator are installed on low-voltage branch lines respectively to treat three-phase unbalanced problems and compensate reactive power; Distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

[0029] like Figures 1 to 3As shown, this technical solution realizes the collection and analysis of substation operation data and automatic adjustment of power quality. Specifically, the data acquisition module 1 ensures the comprehensiveness and accuracy of the data by collecting the operation data of low-voltage energy meters and intelligent switches, as well as multi-stage transformers. It not only covers the operation parameters of traditional power grids, but also pays special attention to the status of new energy equipment such as photovoltaics, charging piles, and energy storage devices, so as to reflect the actual operation of the power grid in real time and accurately. The control strategy module 2 analyzes and processes the collected data through the intelligent fusion terminal and the nine-domain adjustment algorithm, and can automatically analyze and decouple the voltage limit of the equipment on the substation side, and formulate corresponding control strategies according to the nature and severity of the problem. The adjustment action module 3 includes substation side equipment and line side equipment, and realizes precise adjustment through different communication methods, such as RS-485 communication unit, type I concentrator and protocol converter. For example, the on-load tap-changing transformer changes the voltage level by adjusting the gear, the intelligent capacitor compensates for reactive power by group switching, and the photovoltaic inverter optimizes the output of photovoltaic power generation through flexible adjustment. The whole system realizes comprehensive governance of the power quality problems caused by distributed photovoltaic grid connection through the close cooperation of the three modules of data acquisition, control strategy and adjustment action.

[0030] In addition, the power quality autonomous system and method for coping with distributed photovoltaic grid-connected problems according to the present invention also have the following additional technical features: According to one embodiment of the present invention, the longitudinal data collection of the data collection module 1 includes: The low-voltage main switch is connected to the main line of the power grid and is used to provide power to the entire substation area; Branch switches, which are separated from the low-voltage main switch, are used to control the power supply of different branches; Low-voltage distribution box, which connects power lines of different branches and is used to distribute electricity; Meter box installation, on the branch line, each meter box contains multiple household meters for measuring the user's energy consumption; Household meters are installed directly at the user end to record the user's individual energy consumption; The horizontal data collection of the data collection module 1 includes: Photovoltaic equipment, charging piles and energy storage devices are respectively connected to the substation power grid to realize energy input, output and storage.

[0031] This technical solution ensures that the system can fully acquire the operation data of the substation power grid through the longitudinal and lateral data collection methods of the data collection module 1.

[0032] According to one embodiment of the present invention, the low-voltage electric energy meter and the intelligent switch of the data acquisition module 1 are respectively installed at different levels of the power grid in the substation area to collect operation data; The data collected by the data acquisition module 1 is transmitted to the control strategy module 2 through the carrier communication unit using the power line as the communication medium; after receiving the data, the control strategy module 2 analyzes and processes it to formulate and optimize the power grid operation strategy.

[0033] This technical solution realizes real-time data collection and formulation and optimization of power grid operation strategies by utilizing the carrier communication unit to transmit data to the control strategy module 2.

[0034] According to one embodiment of the present invention, the nine-domain regulation algorithm deployed by the control strategy module 2 constructs a coordinate curve diagram of reactive power Q and voltage U, and uses the limit values ​​of reactive power Q and voltage U to divide the entire coordinate curve diagram into nine basic areas, and further subdivide it into 17 specific areas, each area corresponding to a different control strategy.

[0035] This technical solution uses the nine-domain adjustment algorithm deployed by the control strategy module 2 to construct a coordinate curve diagram and divide the regions to formulate different control strategies.

[0036] The nine-domain regulation algorithm deployed in the control strategy module 2 and the control strategies of 17 specific areas are as follows: Figure 3 shown.

[0037] illustrate: ΔUu: The maximum voltage change caused by adjusting the sub-head by one gear; ΔUq: Maximum voltage change caused by switching a group of capacitors; ΔQq: Maximum reactive power change caused by switching a group of capacitors; ΔQu: Maximum reactive power change caused by adjusting the sub-head to one level; Voltage limit: 90%U N ~107%U N ; Reactive power limit: calculated based on the current active load and a power factor of 0.9 to 0.98.

[0038] Table 1. Control strategies for 17 specific areas

[0039] This technical solution provides specific operational guidance for the power quality autonomous system by listing the control strategies for 17 specific areas in detail.

[0040] According to one embodiment of the present invention, the substation side equipment of the adjustment action module 3 is located near the distribution transformer of the power system; the on-load tap-changing transformer and the smart capacitor of the substation side equipment are connected to the distribution system through power lines; the photovoltaic inverter of the substation side equipment receives solar energy through photovoltaic panels and converts it into electrical energy, and then connects to the distribution system through power lines; The line-side equipment of the adjustment action module 3 is distributed in the low-voltage branch lines and pre-meter branches of the power system; the active unbalanced compensation device and steady-state reactive power generator of the line-side equipment are respectively installed at different positions of the low-voltage branch lines to control the three-phase imbalance problem and perform reactive power compensation; the distributed energy storage device of the line-side equipment is installed in the pre-meter branch where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

[0041] This technical solution ensures that the system can effectively solve the power quality problem by adjusting the distribution and function of the substation side equipment and line side equipment of the action module 3.

[0042] According to one embodiment of the present invention, the on-load tap-changing transformer, smart capacitor and photovoltaic inverter of the substation side equipment together constitute an intelligent fusion terminal, wherein: The photovoltaic inverter converts the direct current generated by the distributed photovoltaic power source into alternating current and adjusts the output power according to the grid demand and photovoltaic power generation situation; the smart capacitor detects the reactive power demand in the grid in real time and automatically adjusts its group switching status to provide the necessary reactive power compensation and improve the power factor of the grid; the on-load voltage-changing transformer automatically adjusts its gear according to the changes in the grid voltage to maintain the stability of the grid voltage.

[0043] Example 2 Based on Example 1, Figures 1 to 3 As shown, this embodiment provides a power quality autonomy method for dealing with distributed photovoltaic grid-connected problems, including the following steps: S1, data acquisition processing: data acquisition module 1 collects data of low-voltage main switch, branch switch, low-voltage junction box, meter box and household meter in the vertical direction through low-voltage electric energy meter and intelligent switch; at the same time, it collects energy input, output and storage data of photovoltaic equipment, charging pile and energy storage device in the horizontal direction; the collected data is transmitted to control strategy module 2 through carrier communication unit; S2, control strategy processing: After receiving the data, the control strategy module 2 deploys the nine-domain regulation algorithm for analysis, constructs a coordinate curve diagram of reactive power Q and voltage U, and divides it into nine basic areas and 17 specific areas. Different control strategies are formulated according to the area where the data is located; when a power quality problem is detected, the control strategy module 2 sends a signal to the adjustment action module 3; wherein: S21, Substation side processing: The on-load tap-changing transformer adjusts the gear through the RS-485 communication unit to keep the grid voltage stable; the smart capacitors are switched in groups through the RS-485 communication unit to provide reactive power compensation; the photovoltaic inverter achieves flexible regulation through the type I concentrator and protocol converter to adjust the output power; S22, line-side processing: Active unbalanced compensation devices and steady-state reactive power generators are installed on low-voltage branch lines to manage three-phase unbalance problems and perform reactive power compensation; distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics; S3, feedback and optimization: After the adjustment action module 3 executes the control strategy, the execution result is fed back to the control strategy module 2; the control strategy module 2 optimizes the power grid operation strategy according to the feedback result to achieve autonomy of power quality.

[0044] This technical solution realizes the whole process of data collection, control strategy processing, adjustment action execution, feedback and optimization to ensure the autonomy of power quality. Specifically, through the data collection and processing module, it uses low-voltage electric energy meters and intelligent switches to vertically collect data from the low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter in the substation area, and horizontally collects energy data from photovoltaic equipment, charging piles, and energy storage devices, and transmits these data to the control strategy module 2 through the carrier communication unit; the control strategy module 2 receives these data, deploys the nine-domain regulation algorithm for analysis, divides the data into different areas according to the coordinate curve diagram of reactive power Q and voltage U, and then formulates targeted control strategies. When a power quality problem is detected, the control strategy module 2 sends a signal to the adjustment action module 3, which adjusts and optimizes the power grid in many aspects through the on-load tap-changing transformer, smart capacitor and photovoltaic inverter on the substation side, and the active unbalance compensation device, steady-state reactive power generator and distributed energy storage device on the line side; the adjustment action module 3 feeds back the execution result to the control strategy module 2, and the control strategy module 2 optimizes the power grid operation strategy according to the feedback result, thereby realizing the autonomy of power quality.

[0045] Although the present invention is described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A power quality autonomous system for dealing with distributed photovoltaic grid-connected problems, characterized in that: Included modules: A data acquisition module (1), including a low-voltage electric energy meter and an intelligent switch, is used to collect operation data of the substation; It uses five levels of transformer operation data collection vertically, including low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter; it uses photovoltaic, charging pile, and energy storage device horizontally to achieve hierarchical real-time monitoring; the collected data is transmitted to the control strategy module (2) through the carrier communication unit; The control strategy module (2) includes a master station of the substation area, which is used for data acquisition and algorithm control. It obtains the operating parameters in the data acquisition module (1) through the carrier communication unit, and deploys the nine-domain adjustment algorithm to automatically analyze and decouple the voltage over-limit problem of the substation side equipment. When a power quality problem is detected, the control strategy module (2) sends a signal to the adjustment action module (3), and controls the adjustment action module (3) to make corresponding adjustments. The adjustment action module (3) includes equipment on the substation side and equipment on the line side, wherein: The equipment on the substation side includes on-load tap-changing transformers, smart capacitors and photovoltaic inverters, including: On-load tap-changing transformer, gear adjustment is realized through RS-485 communication unit; Intelligent capacitors can be switched in groups through RS-485 communication unit; Photovoltaic inverter, which achieves flexible regulation through type I concentrator and protocol converter; Line-side equipment, including active unbalanced compensation devices, steady-state reactive power generators and distributed energy storage devices, including: Active unbalanced compensation device and steady-state reactive power generator are installed on low-voltage branch lines respectively to treat three-phase unbalanced problems and compensate reactive power; Distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

2. The power quality autonomous system for dealing with distributed photovoltaic grid-connected problems according to claim 1, characterized in that: The longitudinal data collection of the data collection module (1) comprises: The low-voltage main switch is connected to the main line of the power grid and is used to provide power to the entire substation area; Branch switches, which are separated from the low-voltage main switch, are used to control the power supply of different branches; Low-voltage distribution box, which connects power lines of different branches and is used to distribute electricity; Meter box installation, on the branch line, each meter box contains multiple household meters for measuring the user's energy consumption; Household meters are installed directly at the user end to record the user's individual energy consumption; The horizontal data collection of the data collection module (1) includes: Photovoltaic equipment, charging piles and energy storage devices are respectively connected to the substation power grid to realize energy input, output and storage.

3. The power quality autonomous system for dealing with distributed photovoltaic grid-connected problems according to claim 1 or 2, characterized in that: The low-voltage electric energy meter and the intelligent switch of the data acquisition module (1) are respectively installed at different levels of the power grid in the substation area to collect operation data; The data collected by the data collection module (1) is transmitted to the control strategy module (2) through a carrier communication unit using power lines as a communication medium; after receiving the data, the control strategy module (2) analyzes and processes the data to formulate and optimize the power grid operation strategy.

4. The power quality autonomous system for coping with distributed photovoltaic grid connection problems according to claim 1, characterized in that: The nine-domain regulation algorithm deployed in the control strategy module (2) constructs a coordinate curve diagram of reactive power Q and voltage U, and divides the entire coordinate curve diagram into nine basic areas using the limits of reactive power Q and voltage U, and further subdivides it into 17 specific areas, each area corresponding to a different control strategy.

5. The power quality autonomous system for coping with distributed photovoltaic grid connection problems as claimed in claim 4, characterized in that: The nine-domain regulation algorithm deployed by the control strategy module (2) has 17 specific control strategies: Zone 1: The characteristic is that the reactive power exceeds the lower limit, and the voltage exceeds the upper limit; the control strategy is to cut off the capacitor bank and adjust the inverter; Zone 2: The characteristics are that the reactive power approaches the lower limit and the voltage exceeds the upper limit; the control strategy is to cut off the capacitor bank and adjust the inverter; Zone 3: The characteristics are that the reactive power is normal and the voltage exceeds the upper limit; the control strategy is to reduce the tap, cut the capacitor, and adjust the inverter; Zone 4, the characteristics are reactive power approaching the upper limit, and the voltage exceeds the upper limit; the control strategy is to reduce the tap; Zone 5: The characteristics are that the reactive power exceeds the upper limit, and the voltage exceeds the upper limit; the control strategy is to reduce the tap. If it is at the lowest level, the capacitor bank is forcibly cut off; Zone 6: The characteristics are that the reactive power exceeds the lower limit and the voltage approaches the upper limit; the control strategy is to cut the capacitor bank, and if the capacitor can be cut, it is maintained; Zone 7: The characteristics are that the reactive power exceeds the upper limit and the voltage approaches the upper limit; the control strategy is to first reduce the tap and then invest in the capacitor bank, otherwise maintain; Zone 8, the characteristics are reactive power exceeding the lower limit, and the voltage is normal; the control strategy is to cut off the capacitor bank and increase the tap; Zone 9: The characteristics are in compliance with the operating requirements; the control strategy is no action, maintain the current state; Zone 10, the characteristic is that the reactive power exceeds the upper limit, and the voltage is normal; the control strategy is to invest capacitors and reduce the tap: if no capacitors are invested, it is maintained; Zone 11, the characteristics are reactive power exceeding the lower limit and voltage approaching the lower limit; the control strategy is tap increase; Zone 12: The characteristics are that the reactive power exceeds the upper limit and the voltage approaches the lower limit; the control strategy is to invest in capacitors, and if there is no investment, it is maintained; Zone 13, the characteristic is that the reactive power is lower than the lower limit, the voltage is lower than the lower limit; the control strategy is the tap increase; Zone 14, the characteristics are reactive power approaching the lower limit, and the voltage exceeds the lower limit; the control strategy is to increase the tap, and if it has reached the maximum level, the capacitor is forced to be added; Zone 15, the characteristics are normal reactive power and voltage exceeding the lower limit; the control strategy is to increase the tap and invest in capacitors; Zone 16, the characteristics are that reactive power approaches the upper limit and voltage exceeds the lower limit; the control strategy is to inject capacitors; Zone 17: The characteristic is that the reactive power exceeds the upper limit, and the voltage exceeds the upper limit; the control strategy is to inject capacitors.

6. The power quality autonomous system for coping with distributed photovoltaic grid connection problems according to claim 1, characterized in that: The substation side equipment of the adjustment action module (3) is located near the distribution transformer of the power system; the on-load voltage-changing transformer and the smart capacitor of the substation side equipment are connected to the distribution system through power lines; the photovoltaic inverter of the substation side equipment receives solar energy through photovoltaic panels and converts it into electrical energy, and then connects to the distribution system through power lines; The line side equipment of the adjustment action module (3) is distributed in the low voltage branch line and the pre-meter branch of the power system; The active unbalanced compensation device and steady-state reactive power generator of the line-side equipment are installed at different positions of the low-voltage branch lines to control three-phase imbalance problems and perform reactive power compensation. The distributed energy storage device of the line-side equipment is installed in the pre-meter branch where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics.

7. The power quality autonomous system for coping with distributed photovoltaic grid-connected problems according to claim 1 or 6, characterized in that: The on-load voltage-changing transformer, smart capacitor and photovoltaic inverter of the equipment on the substation side together constitute an intelligent fusion terminal, wherein: The photovoltaic inverter converts the direct current generated by the distributed photovoltaic power source into alternating current and adjusts the output power according to the grid demand and photovoltaic power generation situation; the smart capacitor detects the reactive power demand in the grid in real time and automatically adjusts its group switching status to provide the necessary reactive power compensation and improve the power factor of the grid; the on-load voltage-changing transformer automatically adjusts its gear according to the changes in the grid voltage to maintain the stability of the grid voltage.

8. A power quality autonomy method for dealing with distributed photovoltaic grid-connected problems, using a power quality autonomy system for dealing with distributed photovoltaic grid-connected problems as described in any one of claims 1 to 7, characterized in that: The steps include: S1. Data collection and processing: The data collection module (1) collects data of the low-voltage main switch, branch switch, low-voltage junction box, meter box, and household meter in the vertical direction through the low-voltage electric energy meter and the intelligent switch; at the same time, it collects energy input, output, and storage data of the photovoltaic equipment, charging pile, and energy storage device in the horizontal direction; the collected data is transmitted to the control strategy module (2) through the carrier communication unit; S2. Control strategy processing: After receiving the data, the control strategy module (2) deploys a nine-domain regulation algorithm for analysis, constructs a coordinate curve diagram of reactive power Q and voltage U, and divides it into nine basic areas and 17 specific areas. Different control strategies are formulated according to the area where the data is located. When a power quality problem is detected, the control strategy module (2) sends a signal to the adjustment action module (3); wherein: S21, Substation side processing: The on-load tap-changing transformer adjusts the gear through the RS-485 communication unit to keep the grid voltage stable; the smart capacitors are switched in groups through the RS-485 communication unit to provide reactive power compensation; the photovoltaic inverter achieves flexible regulation through the type I concentrator and protocol converter to adjust the output power; S22, line-side processing: Active unbalanced compensation devices and steady-state reactive power generators are installed on low-voltage branch lines to manage three-phase unbalance problems and perform reactive power compensation; distributed energy storage devices are installed in the pre-meter branches where photovoltaic users are concentrated to solve the voltage over-limit problem caused by photovoltaics; S3, Feedback and optimization: After the adjustment action module executes the control strategy, the execution result is fed back to the control strategy module; the control strategy module optimizes the grid operation strategy according to the feedback result to achieve autonomy of power quality.

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