Photovoltaic grid-connected power factor treatment and voltage treatment device and method
By using photovoltaic grid-connected power factor and voltage management devices, and by utilizing the KZ-1 controller and the transformer integrated automatic device, reactive power compensation and transformer turns ratio are dynamically adjusted, the problems of substandard power factor and excessive voltage caused by distributed photovoltaic power generation systems are solved, thereby improving power quality and reducing electricity costs.
Patent Information
- Application Number
- CN202511056292.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-11-14
AI Technical Summary
After the distributed photovoltaic power generation system is connected to the factory's power distribution network, problems such as substandard power factor and excessive terminal voltage occur. Existing reactive power compensation devices cannot effectively regulate these issues, increasing grid regulation costs and electricity expenses.
Photovoltaic grid-connected power factor and voltage management devices are adopted. The controller KZ-1 collects voltage, current, active power and reactive power data. Combined with the transformer integrated automatic device and reactive power compensation cabinet, the power status quadrant is divided, and reactive power compensation and transformer ratio are adjusted to achieve dynamic regulation of power factor and voltage.
It effectively improved the power quality of the factory, solved the problems of low power factor and excessive voltage rise of low-voltage bus, and reduced the grid regulation cost and electricity bill burden.
Smart Images
Figure CN120955680A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solar photovoltaic power generation technology, and in particular to an apparatus and method for reactive power management and voltage management of distributed photovoltaic grid-connected systems. Background Technology
[0002] In recent years, distributed photovoltaic (PV) power generation systems have been widely used in factories. PV power stations are connected to the factory's power grid nearby, providing green electricity, reducing carbon dioxide emissions, and saving on electricity costs. However, with the increasing proportion of PV installations, some factories have experienced substandard power factors, leading to power regulation fees imposed by the grid. Some factories have also experienced alarms indicating excessive voltage rise at the terminal.
[0003] Reactive power does not consume electrical energy, but it forms energy exchange in the power grid, occupies the power grid's energy bandwidth, reduces the power grid's ability to transmit active energy, and increases the cost of the power grid regulating the power factor. Therefore, the power grid will charge power regulation fees to users whose power factor does not meet the standards.
[0004] The power grid assesses the power factor of enterprise users by using the cosine calculation of the monthly cumulative downlink active energy and the monthly cumulative back-transmission and downlink reactive energy, as shown in Formula 1-8.
[0005] Formula 1 Monthly cumulative power factor at the metering port;
[0006] Formula 2 Monthly cumulative downlink active power at the metering port;
[0007] Formula 3 ; Downlink active power at the metering port;
[0008] Formula 4 Monthly cumulative reactive power at the metering port;
[0009] Formula 5 , Downlink inductive reactive power at the metering port;
[0010] Formula 6 , Downlink capacitive reactive power at the metering port;
[0011] Formula 7 , The metering port returns capacitive reactive power.
[0012] Formula 8 , The metering port returns inductive reactive power.
[0013] Among them, in the formula : Monthly cumulative downlink active power at the metering port; Downlink active power at the metering port; Active power of the load; Photovoltaic power generation active power; : Monthly cumulative reactive power at the metering port; Downlink inductive reactive power at the metering port; Downlink capacitive reactive power at the metering port; The metering port returns inductive reactive power. The metering port returns capacitive reactive power. Inductive reactive load power; The capacitive reactive load power has been compensated.
[0014] The factory's main production load is electric motors, which are inductive loads. During operation, they generate inductive reactive power, causing the current phase to lag behind the voltage. Capacitive reactive current leads the voltage. Compensating for capacitive reactive power on the load side can bring the current back into near-phase with the voltage. Locally compensating reactive loads at the grid's end can reduce the amount of inductive reactive power transmitted to the grid, increasing the grid's active power transmission capacity.
[0015] Photovoltaic (PV) power is connected to the factory's power distribution network, providing active power to offset some of the active power flowing down from the grid. However, the reactive power flowing down from the grid does not decrease accordingly, leading to a decrease in the ratio of active to reactive power at the factory's electricity metering port. According to formula 1-8, this results in a lower power factor. However, when the PV power generation exceeds the factory's load, it feeds back power to the grid. The factory's existing reactive power compensation control device cannot recognize this back-feeding active power, causing the already activated reactive load to be cut off, exacerbating the power factor deterioration. Simultaneously, because the PV inputs active power to the grid, the downstream active power decreases, leading to a reduction in line voltage drop and further increasing the voltage at the grid's endpoints.
[0016] Faced with a decrease in the ratio of active to reactive power at the factory's electricity metering port, some factories' existing reactive power compensation devices have limited capacity and cannot effectively adjust the factory's power factor. Furthermore, when reverse power flow occurs at the factory's electricity metering port, causing the reactive power compensation device to be disconnected, the control systems of some factories' existing reactive power compensation devices are unable to adapt to reactive power compensation operations under reverse power flow conditions, thus failing to effectively adjust the factory's power factor. Some factories have installed four-quadrant reactive power compensation controllers, which, although compensating for the power factor, reduce line voltage drop due to reactive power compensation, exacerbating the problem of excessive voltage rise at the grid's end. Summary of the Invention
[0017] This invention addresses the problems existing in the prior art by providing a device and method for photovoltaic grid-connected power factor control and voltage control. This device can, based on the active and reactive power input of the power grid of a factory connected to photovoltaic power, address the issues of low power factor and excessive low-voltage bus voltage rise in the factory, thereby improving the factory's power quality.
[0018] To achieve the above-mentioned technical objectives, this invention provides a photovoltaic grid-connected power factor correction and voltage correction device, installed in a factory power distribution network system. The factory power distribution network system includes an on-load tap-changing transformer, a transformer integrated automatic device BT-1, a photovoltaic incoming line cabinet, a reactive power compensation cabinet SVC, a voltage transformer cabinet PT, and a load outgoing line cabinet. The photovoltaic grid-connected power factor correction and voltage correction device includes a controller KZ-1, a bidirectional meter AT-1, a first unidirectional meter AT-2, a second unidirectional meter AT-3, and a third unidirectional meter AT-4. The controller KZ-1 is connected to the bidirectional meter AT-1, the first unidirectional meter AT-2, the second unidirectional meter AT-3, the third unidirectional meter AT-4, the transformer integrated automatic device BT-1, and the voltage transformer cabinet PT via RS485 control wires.
[0019] The bidirectional meter AT-1 is located on the low-voltage outgoing side of the transformer and is used to measure the downstream active power, downstream reactive power, returned active power, returned reactive power, cumulative downstream active energy, cumulative downstream reactive energy, cumulative returned active energy, and cumulative returned reactive energy at the low-voltage outgoing line of the transformer.
[0020] The first one-way meter AT-2 is located in the photovoltaic incoming line cabinet and is used to measure the active power and reactive power of photovoltaic power generation; the third one-way meter AT-4 is located in the load outgoing line cabinet and is used to measure the active power and reactive power of the load; the second one-way meter AT-3 and the controller KZ-1 are located in the reactive power compensation cabinet SVC, and the second one-way meter AT-3 is used to measure the reactive power compensation.
[0021] The controller KZ-1 collects voltage, current, active power, and reactive power data from each meter, as well as bus voltage data from the voltage transformer. It also sends capacitor activation and deactivation commands to the reactive power compensation cabinet SVC and commands to adjust the transformer ratio to the transformer integrated automatic device BT-1.
[0022] A further technical solution of the present invention: The controller KZ-1 has a built-in control strategy program. The control strategy program divides the power state of the transformer's low-voltage outgoing node into the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant according to the direction of active power and the phase of voltage and current. Based on the quadrant in which the node is located, the program controls the reactive power compensation cabinet to put on and cut off capacitors, adjusts the power factor, calculates the voltage drop and voltage rise of the incoming circuit based on the current active and reactive power of the node, controls the on-load transformer to adjust the high-voltage side tap position, adjusts the transformer ratio, and thus adjusts the low-voltage bus voltage.
[0023] The preferred technical solution of the present invention is as follows: The factory power distribution network system includes one on-load tap-changing transformer, one overhead incoming line connected to the high-voltage side of the transformer, one 0.4kV busbar connected to the low-voltage side of the transformer, one photovoltaic incoming line cabinet connected to the 0.4kV busbar, one reactive power compensation cabinet SVC connected to the 0.4kV busbar, one voltage transformer cabinet PT connected to the 0.4kV busbar, and one load outgoing line cabinet connected to the 0.4kV busbar. A transformer low-voltage outgoing line cabinet is provided on the low-voltage side of the transformer. The transformer integrated automatic device BT-1 is installed in the transformer control cabinet. A current transformer CT-1 is installed in the transformer low-voltage outgoing line cabinet, a current transformer CT-2 is installed in the photovoltaic incoming line cabinet, a current transformer CT-3 is installed in the reactive power compensation cabinet SVC, and a current transformer CT-4 is installed in the load outgoing line cabinet.
[0024] The preferred technical solution of the present invention is that the bidirectional metering meter AT-1 is installed in the low-voltage outgoing cabinet of the transformer.
[0025] To achieve the above objectives, the present invention also provides a method for photovoltaic grid-connected power factor control and voltage control, used for photovoltaic grid-connected power factor control and voltage control in factory distribution network systems. The method utilizes the aforementioned photovoltaic grid-connected power factor control and voltage control device, and its specific steps are as follows:
[0026] S1. Initial Data Acquisition: The low-voltage bus voltage is measured using voltage transformers (PT), the low-voltage outgoing current of the transformer is measured using current transformer (CT-1), the photovoltaic incoming current is measured using current transformer (CT-2), the reactive power compensation device incoming current is measured using current transformer (CT-3), and the load outgoing current is measured using current transformer (CT-4). The active and reactive power at the low-voltage outgoing nodes of the transformer are measured using meter AT-1, meter AT-2, meter AT-3, and meter AT-4. After initial data acquisition, proceed to step S2.
[0027] S2. The controller KZ-1 determines the direction of active power at the low-voltage outgoing node of the transformer based on the measurement of the meter AT-1.
[0028] If there is active power downstream, the controller KZ-1 makes a determination based on the phase of the voltage and current at the low-voltage outgoing node measured by the meter AT-1; if the voltage leads the current, proceed to step S3; if the voltage lags the current, proceed to step S6.
[0029] If active power is returned, the controller KZ-1 makes a determination based on the phase of the voltage and current at the low-voltage outgoing node measured by the meter AT-1; if the voltage leads the current, proceed to step S5; if the voltage lags the current, proceed to step S4.
[0030] S3. Controller KZ-1 defines the transformer low-voltage outgoing line node as operating in the first quadrant, with downstream active power and downstream inductive reactive power; proceed to step S301.
[0031] S301. Controller KZ-1 calculates the power factor of the transformer low-voltage outgoing node according to the following formula ①: ①, In the above formula, Instantaneous power factor in the first quadrant at meter AT-1; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1;
[0032] The power factor is determined based on the value. If the power factor is higher than 0.92, proceed to step S303; if the power factor is lower than 0.92, proceed to step S302.
[0033] S302. Controller KZ-1 calculates the power of the capacitive reactive load in the first quadrant according to the following formula ②. Based on the calculated value, the SVC is controlled to compensate for capacitive reactive load, and the process returns to step S301; Formula ② is as follows: ②, In the above formula, First quadrant: Compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated. : Downward active power at meter AT-1;
[0034] S303. Controller KZ-1 determines the low-voltage bus voltage according to the following formula ③; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise is greater than 5% or the voltage drop is greater than 5%, proceed to step S304; formula ③ is as follows: ③, In the above formula, : Rated voltage on the low-voltage side of the transformer; Low-voltage bus voltage in the first quadrant;
[0035] S304. If the voltage rise exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ④, ⑤, and ⑥, then returns to step S303; the specific formulas are as follows: ④, ⑤, ⑥, In the above formula, The absolute value of the voltage drop in the high-voltage circuit in the first quadrant; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of a high-voltage line; : High-voltage side voltage of the transformer; Low-voltage bus voltage in the first quadrant; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio;
[0036] S4. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the second quadrant, returning active power and capacitive reactive power, and enters step S401.
[0037] S401. Calculate the power of the compensated capacitive reactive load in the second quadrant according to the following formula ⑦. Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S402; Formula ⑦ is as follows: ⑦, In the above formula, Second quadrant compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0038] S402. Determine the bus voltage according to formula ⑧; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S403; formula ⑧ is as follows: ⑧, In the above formula, : Rated voltage on the low-voltage side of the transformer; Second quadrant low-voltage bus voltage;
[0039] S403. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑨, ⑩, ⑪; return to step S402; ⑨, ⑩, ⑪, In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the second quadrant; : Upstream active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Second quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio;
[0040] S5. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the third quadrant, returning active power and inductive reactive power, and enters step S501.
[0041] S501. Calculate the power of the capacitive reactive load in the third quadrant according to the following formula (12). Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S502; formula ⑫ is as follows: ⑫, In the above formula, The third quadrant reduces capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0042] S502. Determine the bus voltage according to the following formula ⑬; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S503, formula ⑬ as follows: ⑬, In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage;
[0043] S503. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑭, ⑮, ⑯; return to step S502; ⑭, ⑮, 16, In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the third quadrant; : Upstream active power at meter AT-1; : Upward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Third quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio.
[0044] S6. Controller KZ-1 defines the transformer low-voltage outgoing node as operating in the fourth quadrant, with downstream active power and downstream capacitive reactive power; proceed to step S601.
[0045] S601. Calculate the reduced capacitive reactive power in the fourth quadrant according to the following formula (17). And reduce the capacitive reactive load according to the calculated value, and proceed to step S602; ⑰, In the above formula, The fourth quadrant reduces capacitive reactive load power. Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0046] S602. Determine the bus voltage according to the following formula (18); if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S603; formula (18) is as follows: 18, In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage;
[0047] S603. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑲, ⑳, and ㉑; return to step S602; 19, ⑳, ㉑, In the above formula, The absolute value of voltage drop in the high-voltage circuit of the fourth quadrant; : Downward active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Fourth quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio.
[0048] The controller KZ-1 of this invention can collect voltage, current, active power, and reactive power data from meters AT-1, AT-2, AT-3, and AT-4, as well as voltage data from the voltage transformer PT bus. It can also send commands to the reactive power compensation device SVC to connect and disconnect capacitors, and commands to the transformer integrated automatic device BT-1 to adjust the transformer ratio. The controller KZ-1 has a built-in control strategy program that can divide the power state of the low-voltage outgoing node of the transformer into the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant according to the direction of active power and the phase of voltage and current. The control strategy program can control the reactive power compensation cabinet to connect and disconnect capacitors according to the quadrant in which the node is located, adjust the power factor, and calculate the voltage drop and voltage rise of the incoming circuit based on the current active and reactive power of the node. It can also control the on-load transformer to adjust the high-voltage side tap position, adjust the transformer ratio, and thus adjust the low-voltage bus voltage.
[0049] This invention is installed in the factory power distribution network system and can address the problems of low power factor and excessive low-voltage bus voltage rise in the factory based on the active and reactive power input of the photovoltaic-connected factory power grid, thereby improving the factory's power quality. Attached Figure Description
[0050] Figure 1 This is a schematic diagram of the electrical wiring of the device in this invention;
[0051] Figure 2 This is a schematic diagram of the electrical wiring of the factory power distribution network connected to photovoltaics in this invention;
[0052] Figure 3 Electrical wiring diagram for installing the device of this invention in a factory power distribution network connected to photovoltaics;
[0053] Figure 4 This is a schematic diagram of the four-quadrant working range of the low-voltage outgoing node of the transformer in this invention;
[0054] Figure 5 The flowchart of the method control strategy in this invention. Detailed Implementation
[0055] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figures 1 to 5 All accompanying drawings are simplified versions of embodiments and are intended only to clearly and concisely illustrate the embodiments of the present invention. The technical solutions shown in the drawings below are specific solutions of embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0056] An embodiment provides a photovoltaic grid-connected power factor correction and voltage correction device, such as Figure 1 As shown, it includes one controller KZ-1, one bidirectional meter AT-1, three unidirectional meters (the first unidirectional meter AT-2, the second unidirectional meter AT-3, and the third unidirectional meter AT-4, respectively), and several RS485 control wires; the photovoltaic grid-connected power factor correction and voltage correction device is installed in the factory's power distribution network system, such as... Figure 2 The factory power distribution network system includes one on-load tap-changing transformer, one overhead incoming line connected to the high-voltage side of the transformer, one 0.4kV busbar connected to the low-voltage side of the transformer, one photovoltaic incoming line cabinet connected to the 0.4kV busbar, one reactive power compensation cabinet (SVC) connected to the 0.4kV busbar, one voltage transformer cabinet (PT) connected to the 0.4kV busbar, and one load outgoing line cabinet connected to the 0.4kV busbar. A low-voltage outgoing line cabinet is also provided on the low-voltage side of the transformer. The transformer integrated automatic device BT-1 is installed inside the transformer control cabinet. Current transformer CT-1 is installed in the low-voltage outgoing line cabinet, current transformer CT-2 is installed in the photovoltaic incoming line cabinet, current transformer CT-3 is installed in the reactive power compensation cabinet (SVC), and current transformer CT-4 is installed in the load outgoing line cabinet. Figure 1 As shown, the controller KZ-1 is connected to the bidirectional metering meter AT-1, the first unidirectional metering meter AT-2, the second unidirectional metering meter AT-3, the third unidirectional metering meter AT-4, the transformer integrated automatic device BT-1, and the voltage transformer cabinet PT signal via RS485 control wires.
[0057] In the embodiments, such as Figure 3As shown, the bidirectional meter AT-1 is located on the low-voltage outgoing side of the transformer and is used to measure the downstream active power, downstream reactive power, returned active power, returned reactive power, cumulative downstream active energy, cumulative downstream reactive energy, cumulative returned active energy, and cumulative returned reactive energy at the low-voltage outgoing line of the transformer. The first unidirectional meter AT-2 is located in the photovoltaic incoming line cabinet and is used to measure the active and reactive power of photovoltaic power generation. The third unidirectional meter AT-4 is located in the load outgoing line cabinet and is used to measure the active and reactive power of the load. The second unidirectional meter AT-3 and the controller KZ-1 are located in the reactive power compensation cabinet SVC. The second unidirectional meter AT-3 is used to measure the reactive power compensation. The controller KZ-1 collects the voltage, current, active power, and reactive power data of each meter and the voltage transformer bus voltage data, and sends capacitor connection and disconnection commands to the reactive power compensation cabinet SVC, and sends transformer ratio adjustment commands to the transformer integrated automatic device BT-1. The bidirectional meter AT-1 is installed inside the low-voltage outgoing cabinet of the transformer.
[0058] In the embodiments, such as Figure 4 As shown, the controller KZ-1 has a built-in control strategy program. The control strategy program divides the power state of the transformer's low-voltage outgoing node into the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant according to the direction of active power and the phase of voltage and current. Based on the quadrant in which the node is located, the program controls the reactive power compensation cabinet to put on and cut off capacitors, adjusts the power factor, calculates the voltage drop and voltage rise of the incoming circuit based on the current active and reactive power of the node, controls the on-load transformer to adjust the high-voltage side tap position, adjusts the transformer ratio, and thus adjusts the low-voltage bus voltage.
[0059] The embodiment provides a photovoltaic grid-connected power factor and voltage control method for controlling the photovoltaic grid-connected power factor and voltage in a factory distribution network system. The method uses the aforementioned photovoltaic grid-connected power factor and voltage control device, and its specific steps are as follows:
[0060] S1. Initial Data Acquisition: The low-voltage bus voltage is measured using voltage transformers (PT), the low-voltage outgoing current of the transformer is measured using current transformer (CT-1), the photovoltaic incoming current is measured using current transformer (CT-2), the reactive power compensation device incoming current is measured using current transformer (CT-3), and the load outgoing current is measured using current transformer (CT-4). The active and reactive power at the low-voltage outgoing nodes of the transformer are measured using meter AT-1, meter AT-2, meter AT-3, and meter AT-4. After initial data acquisition, proceed to step S2.
[0061] S2. The controller KZ-1 determines the direction of active power at the low-voltage outgoing node of the transformer based on the measurement of the meter AT-1.
[0062] If there is active power downstream, the controller KZ-1 makes a determination based on the phase of the voltage and current at the low-voltage outgoing node measured by the meter AT-1; if the voltage leads the current, proceed to step S3; if the voltage lags the current, proceed to step S6.
[0063] If active power is returned, the controller KZ-1 makes a determination based on the phase of the voltage and current at the low-voltage outgoing node measured by the meter AT-1; if the voltage leads the current, proceed to step S5; if the voltage lags the current, proceed to step S4.
[0064] S3. Controller KZ-1 defines the transformer low-voltage outgoing line node as operating in the first quadrant, with downstream active power and downstream inductive reactive power; proceed to step S301.
[0065] S301. Controller KZ-1 calculates the power factor of the transformer low-voltage outgoing node according to the following formula ①: ①, In the above formula, Instantaneous power factor in the first quadrant at meter AT-1; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1;
[0066] The power factor is determined based on the value. If the power factor is higher than 0.92, proceed to step S303; if the power factor is lower than 0.92, proceed to step S302.
[0067] S302. Controller KZ-1 calculates the power of the capacitive reactive load in the first quadrant according to the following formula ②. Based on the calculated value, the SVC is controlled to compensate for capacitive reactive load, and the process returns to step S301; Formula ② is as follows: ②, In the above formula, First quadrant: Compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated. : Downward active power at meter AT-1;
[0068] S303. Controller KZ-1 determines the low-voltage bus voltage according to the following formula ③; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise is greater than 5% or the voltage drop is greater than 5%, proceed to step S304; formula ③ is as follows: ③, In the above formula, : Rated voltage on the low-voltage side of the transformer; Low-voltage bus voltage in the first quadrant;
[0069] S304. If the voltage rise exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ④, ⑤, and ⑥, then returns to step S303; the specific formulas are as follows: ④, ⑤, ⑥, In the above formula, The absolute value of the voltage drop in the high-voltage circuit in the first quadrant; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of a high-voltage line; : High-voltage side voltage of the transformer; Low-voltage bus voltage in the first quadrant; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio;
[0070] S4. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the second quadrant, returning active power and capacitive reactive power, and enters step S401.
[0071] S401. Calculate the power of the compensated capacitive reactive load in the second quadrant according to the following formula ⑦. Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S402; Formula ⑦ is as follows: ⑦, In the above formula, Second quadrant compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0072] S402. Determine the bus voltage according to formula ⑧; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S403; formula ⑧ is as follows: ⑧, In the above formula, : Rated voltage on the low-voltage side of the transformer; Second quadrant low-voltage bus voltage;
[0073] S403. If the voltage rise exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the transformer high-voltage side tap position one step lower; if the voltage drop exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the transformer high-voltage side tap position one step higher; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑨, ⑩, and ⑪; then returns to step S402; the formulas are as follows: ⑨, ⑩, ⑪, In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the second quadrant; : Upstream active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Second quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio;
[0074] S5. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the third quadrant, returning active power and inductive reactive power, and enters step S501.
[0075] S501. Calculate the power of the capacitive reactive load in the third quadrant according to the following formula (12). Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S502; formula ⑫ is as follows: ⑫, In the above formula, The third quadrant reduces capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0076] S502. Determine the bus voltage according to the following formula ⑬; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S503, formula ⑬ as follows:
[0077] ⑬,
[0078] In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage;
[0079] S503. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑭, ⑮, ⑯; return to step S502; ⑭, ⑮, 16, In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the third quadrant; : Upstream active power at meter AT-1; : Upward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Third quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio.
[0080] S6. Controller KZ-1 defines the transformer low-voltage outgoing node as operating in the fourth quadrant, with downstream active power and downstream capacitive reactive power; proceed to step S601.
[0081] S601. Calculate the reduced capacitive reactive power in the fourth quadrant according to the following formula (17). And reduce the capacitive reactive load according to the calculated value, and proceed to step S602; ⑰, In the above formula, The fourth quadrant reduces capacitive reactive load power. Inductive reactive load power; The capacitive reactive load power has already been compensated.
[0082] S602. Determine the bus voltage according to the following formula (18); if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S603; formula (18) is as follows: 18, In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage;
[0083] S603. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑲, ⑳, and ㉑; return to step S602; 19, ⑳, ㉑, In the above formula, The absolute value of voltage drop in the high-voltage circuit of the fourth quadrant; : Downward active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Fourth quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio.
[0084] The invention will be further illustrated below with specific application examples. One example is a factory, equipped with a 1000kVA-10 / 0.4kV transformer connected to a 10kV overhead conductor. The overhead conductor is LGJ-150 / 50, 10km long, with a line resistance of 3Ω, reactance of 5Ω, and susceptance of 23Ω. The transformer has a resistance of 0.6Ω and a reactance of 6Ω. The factory's rated active power load is 800kW, rated reactive power load is 600kvar, and the factory's reactive power compensation device has a rated capacity of 500kvar. The factory is connected to a photovoltaic power station with a grid-connected capacity of 800kW. The photovoltaic power generation mode is "self-consumption with surplus power fed into the grid." The transformer supports on-load tap changing with a tap change step of 2.5%. The tap positions corresponding to the high-voltage side voltages are shown in Table 1.
[0085] Based on six operating conditions, a comparative analysis was conducted on the changes in system power factor after reactive power compensation using the photovoltaic grid-connected power factor control and voltage control devices and methods in the embodiments of the present invention; a comparative analysis was also conducted on the changes in system low-voltage bus voltage before and after transformer ratio adjustment using the devices and methods of the present invention, as shown in Table 1.
[0086] Table 1. Comparison and analysis of transformer turns ratio adjustment before and after using the present invention under different operating conditions.
[0087]
[0088] The above comparative analysis shows that before using the device and method of this invention for reactive power compensation, the monthly cumulative power factor at the metering port was 0.759, which did not meet the standard. After using the device and method of this invention for reactive power compensation, the monthly cumulative power factor at the metering port was 0.956, which met the standard.
[0089] Before using the device and method of the present invention for reactive power compensation, the instantaneous power factor of the metering port corresponding to operating condition 3 is 0.707, and the instantaneous power factor of the metering port corresponding to operating condition 4 is 0.003, which does not meet the standard.
[0090] After reactive power compensation using the device and method of this invention, the instantaneous power factor of the metering port corresponding to operating condition 3 is 0.92, and the instantaneous power factor of the metering port corresponding to operating condition 4 is 0.92, both meeting the standard.
[0091] Before using the device and method of this invention for power factor compensation and transformer turns ratio adjustment, the low-voltage bus voltage corresponding to operating condition 1 is 0.396kV, which is too low; the low-voltage bus voltage corresponding to operating condition 4 is 0.420kV; the low-voltage bus voltage corresponding to operating condition 6 is 0.427kV; the low-voltage bus voltage corresponding to operating condition 5 is 0.426kV; and the low-voltage bus voltage corresponding to operating condition 6 is 0.427kV, which exceeds the standard.
[0092] After power factor compensation and transformer turns ratio adjustment using the device and method of this invention, the low-voltage bus voltage corresponding to operating condition 1 is 0.406kV, operating condition 4 is 0.410kV, operating condition 5 is 0.411kV, and operating condition 6 is 0.412kV, all of which are normal. See Table 1.
[0093] Analysis results show that after using the device and method of this invention for reactive power compensation and transformer ratio linkage adjustment in the photovoltaic-connected factory power distribution network system, the system power factor is significantly improved, the low-voltage bus voltage stability is enhanced, the fluctuation range is reduced, and the factory power supply quality is significantly improved.
[0094] The above description is merely one embodiment of the present invention, and while it is detailed and specific, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.
Claims
1. A photovoltaic grid-connected power factor correction and voltage correction device, installed in a factory power distribution network system, the factory power distribution network system comprising an on-load tap-changing transformer, a transformer integrated automatic device BT-1, a photovoltaic incoming line cabinet, a reactive power compensation cabinet SVC, a voltage transformer cabinet PT, and a load outgoing line cabinet, characterized in that: The photovoltaic grid-connected power factor correction and voltage correction device includes a controller KZ-1, a bidirectional meter AT-1, a first unidirectional meter AT-2, a second unidirectional meter AT-3, and a third unidirectional meter AT-4. The controller KZ-1 is connected to the bidirectional meter AT-1, the first unidirectional meter AT-2, the second unidirectional meter AT-3, the third unidirectional meter AT-4, the transformer integrated automatic device BT-1, and the voltage transformer cabinet PT via RS485 control wires. The bidirectional meter AT-1 is located on the low-voltage outgoing side of the transformer and is used to measure the downstream active power, downstream reactive power, returned active power, returned reactive power, cumulative downstream active energy, cumulative downstream reactive energy, cumulative returned active energy, and cumulative returned reactive energy at the low-voltage outgoing line of the transformer. The first one-way meter AT-2 is located in the photovoltaic incoming line cabinet and is used to measure the active power and reactive power of photovoltaic power generation; the third one-way meter AT-4 is located in the load outgoing line cabinet and is used to measure the active power and reactive power of the load; the second one-way meter AT-3 and the controller KZ-1 are located in the reactive power compensation cabinet SVC, and the second one-way meter AT-3 is used to measure the reactive power compensation. The controller KZ-1 collects voltage, current, active power, and reactive power data from each meter, as well as bus voltage data from the voltage transformer. It also sends capacitor activation and deactivation commands to the reactive power compensation cabinet SVC and commands to adjust the transformer ratio to the transformer integrated automatic device BT-1.
2. The photovoltaic grid-connected power factor correction and voltage correction device according to claim 1, characterized in that: The controller KZ-1 has a built-in control strategy program. The control strategy program divides the power state of the transformer's low-voltage outgoing nodes into the first quadrant, second quadrant, third quadrant, and fourth quadrant according to the direction of active power and the phase of voltage and current. Based on the quadrant in which the node is located, the program controls the reactive power compensation cabinet to put on and cut off capacitors, adjusts the power factor, calculates the voltage drop and voltage rise of the incoming circuit based on the current active and reactive power of the node, controls the on-load transformer to adjust the high-voltage side tap position, adjusts the transformer ratio, and thus adjusts the low-voltage bus voltage.
3. A photovoltaic grid-connected power factor correction and voltage correction device according to claim 1 or 2, characterized in that: The factory power distribution network system includes one on-load tap-changing transformer, one overhead incoming line connected to the high-voltage side of the transformer, one 0.4kV busbar connected to the low-voltage side of the transformer, one photovoltaic incoming line cabinet connected to the 0.4kV busbar, one reactive power compensation cabinet SVC connected to the 0.4kV busbar, one voltage transformer cabinet PT connected to the 0.4kV busbar, and one load outgoing line cabinet connected to the 0.4kV busbar. A low-voltage outgoing line cabinet is provided on the low-voltage side of the transformer. The transformer integrated automatic device BT-1 is installed in the transformer control cabinet. A current transformer CT-1 is installed in the low-voltage outgoing line cabinet, a current transformer CT-2 is installed in the photovoltaic incoming line cabinet, a current transformer CT-3 is installed in the reactive power compensation cabinet SVC, and a current transformer CT-4 is installed in the load outgoing line cabinet.
4. The photovoltaic grid-connected power factor correction and voltage correction device according to claim 3, characterized in that: The bidirectional meter AT-1 is installed inside the low-voltage outgoing cabinet of the transformer.
5. A method for photovoltaic grid-connected power factor control and voltage control, used for photovoltaic grid-connected power factor control and voltage control in factory distribution network systems, characterized in that, The method uses the photovoltaic grid-connected power factor correction and voltage correction device described in claim 3, and its specific steps are as follows: S1. Initial Data Acquisition: The low-voltage bus voltage is measured using voltage transformers (PT), the low-voltage outgoing current of the transformer is measured using current transformer (CT-1), the photovoltaic incoming current is measured using current transformer (CT-2), the reactive power compensation device incoming current is measured using current transformer (CT-3), and the load outgoing current is measured using current transformer (CT-4). The active and reactive power at the low-voltage outgoing nodes of the transformer are measured using meter AT-1, meter AT-2, meter AT-3, and meter AT-4. After initial data acquisition, proceed to step S2. S2. The controller KZ-1 determines the direction of active power at the low-voltage outgoing node of the transformer based on the measurement of the meter AT-1. If there is active power downstream, the controller KZ-1 determines the phase of the voltage and current at the low-voltage outgoing node based on the meter AT-1. If the voltage leads the current, proceed to step S3; if the voltage lags the current, proceed to step S6. If active power is returned, the controller KZ-1 makes a determination based on the phase of the voltage and current at the low-voltage outgoing node measured by the meter AT-1. If the voltage leads the current, proceed to step S5; if the voltage lags the current, proceed to step S4. S3. Controller KZ-1 defines the transformer low-voltage outgoing line node as operating in the first quadrant, with downstream active power and downstream inductive reactive power; proceed to step S301. S301. Controller KZ-1 calculates the power factor of the transformer low-voltage outgoing node according to the following formula ①: ①， In the above formula, Instantaneous power factor in the first quadrant at meter AT-1; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1; The power factor is determined based on the value. If the power factor is higher than 0.92, proceed to step S303; if the power factor is lower than 0.92, proceed to step S302. S302. Controller KZ-1 calculates the power of the capacitive reactive load in the first quadrant according to the following formula ②. Based on the calculated value, the SVC is controlled to compensate for capacitive reactive load, and the process returns to step S301; Formula ② is as follows: ②， In the above formula, First quadrant: Compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated. : Downward active power at meter AT-1; S303. Controller KZ-1 determines the low-voltage bus voltage according to the following formula ③; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise is greater than 5% or the voltage drop is greater than 5%, proceed to step S304; formula ③ is as follows: ③， In the above formula, : Rated voltage on the low-voltage side of the transformer; First quadrant low-voltage bus voltage; S304. If the voltage rise exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to the transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by one step; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ④, ⑤, and ⑥, then returns to step S303; the specific formulas are as follows: ④， ⑤， ⑥， In the above formula, The absolute value of the voltage drop in the high-voltage circuit in the first quadrant; : Downward active power at meter AT-1; : Downward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of a high-voltage line; : High-voltage side voltage of the transformer; First quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio; S4. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the second quadrant, returning active power and capacitive reactive power, and enters step S401. S401. Calculate the power of the second quadrant compensating capacitive reactive load according to the following formula ⑦. Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S402; Formula ⑦ is as follows: ⑦， In the above formula, Second quadrant compensation for capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated. S402. Determine the bus voltage according to formula ⑧; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S403; formula ⑧ is as follows: ⑧， In the above formula, : Rated voltage on the low-voltage side of the transformer; Second quadrant low-voltage bus voltage; S403. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; and calculates the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑨, ⑩, and ⑪. Return to step S402; ⑨， ⑩， ⑪， In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the second quadrant; : Upstream active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Second quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio; S5. Controller KZ-1 defines the transformer low-voltage outgoing node to operate in the third quadrant, returning active power and inductive reactive power, and enters step S501. S501. Calculate the power of the capacitive reactive load in the third quadrant according to the following formula (12). Then, based on the calculated values, compensate for the capacitive reactive load and proceed to step S502; formula ⑫ is as follows: ⑫， In the above formula, The third quadrant reduces capacitive reactive load power; Inductive reactive load power; The capacitive reactive load power has already been compensated. S502. Determine the bus voltage according to the following formula ⑬; if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S503, formula ⑬ as follows: ⑬， In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage; S503. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑭, ⑮, and ⑯. Return to step S502; ⑭， ⑮， ⑯， In the above formula, The absolute value of the voltage rise in the high-voltage circuit of the third quadrant; : Upstream active power at meter AT-1; : Upward inductive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Third quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio; S6. Controller KZ-1 defines the transformer low-voltage outgoing node as operating in the fourth quadrant, with downstream active power and downstream capacitive reactive power; proceed to step S601. S601. Calculate the reduced capacitive reactive power in the fourth quadrant according to the following formula (17). And reduce the capacitive reactive load according to the calculated value, and proceed to step S602; ⑰， In the above formula, The fourth quadrant reduces capacitive reactive load power. Inductive reactive load power; The capacitive reactive load power has already been compensated. S602. Determine the bus voltage according to the following formula (18); if the voltage rise is less than 5% or the voltage drop is less than 5%, the process ends; if the voltage rise exceeds 5% or the voltage drop exceeds 5%, proceed to step S603; formula (18) is as follows: ⑱， In the above formula, : Rated voltage on the low-voltage side of the transformer; Third quadrant low-voltage bus voltage; S603. If the voltage rise exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; if the voltage drop exceeds 5%, controller ZK-1 sends a command to transformer integrated automatic device BT-1 to adjust the high-voltage side tap position of the transformer by 1 step; calculate the low-voltage bus voltage after adjusting the transformer ratio according to the following formulas ⑲, ⑳, and ㉑. Return to step S602; ⑲， ⑳， ㉑， In the above formula, The absolute value of voltage drop in the high-voltage circuit of the fourth quadrant; : Downward active power at meter AT-1; : Downward capacitive reactive power at meter AT-1; : Rated voltage on the high-voltage side of the transformer; : Voltage at the beginning of the line; : High-voltage side voltage of the transformer; Fourth quadrant low-voltage bus voltage; Total resistance of the high-voltage circuit; Total reactance of the high-voltage circuit; Line resistance; Line reactance; Transformer resistance; Transformer reactance; : Rated power of the transformer; Transformer load factor; Transformer turns ratio.