A grid-connected overvoltage control system

Abstract

The present application discloses a grid-connected overvoltage control system, which includes a voltage regulating converter, an overvoltage suppressor, and a power energy storage device. Among them, the voltage regulating converter obtains the real-time load current signal of grid connection, the voltage value of the DC current transmitted to the power energy storage device, and the charge and discharge power parameters of the power energy storage device. The overvoltage suppressor obtains the real-time voltage signal of grid connection, the charge and discharge power parameters of the power energy storage device, and the state of charge parameter, predicts the load power of grid connection in the future period based on the load power of grid connection in the current period, and through the combined processing of the voltage regulating converter and the overvoltage suppressor, obtains the grid-connected overvoltage regulation amount for controlling the grid-connected voltage. It can be seen that the present application obtains the electrical energy parameters of grid connection in real time, performs real-time overvoltage control by combining the voltage regulating converter and the overvoltage suppressor, effectively controls the abnormal voltage fluctuations of grid connection in a timely manner, avoids the increase of voltage fluctuations, improves the qualification rate of grid-connected voltage, and improves the power quality of grid connection.

Description

Technical Field

[0001] This application relates to the technical field of voltage control, and more specifically, to a grid-connected overvoltage control system. Background Art

[0002] With the improvement of people's living quality, the power consumption has increased rapidly. To meet people's demand for electricity, photovoltaic power generation with a large power generation capacity is adopted for power generation. Currently, in a distributed photovoltaic power generation system, there are multiple distributed photovoltaic grid connection points. Due to the large photovoltaic power generation capacity, there are sometimes situations where power is fed back to the superior power grid, and the voltages of some grid connection points and common connection points are raised to exceed the rated limit. In view of this situation, the grid-connected inverters in the current distributed photovoltaic power generation system adopt the maximum power point tracking method for grid-connected power generation. The maximum power point tracking controller can detect the power generation voltage of the solar panel in real time, track the highest voltage and current values, and enable the system to output the maximum power to charge the battery.

[0003] However, the voltage control method of using the maximum power point tracking controller for grid-connected power generation results in large fluctuations in the grid-connected voltage of the photovoltaic system, a decrease in the qualification rate of the grid-connected voltage, and poor power quality. If the distribution voltage is too high, the equipment is prone to damage when working at a high voltage for a long time. Summary of the Invention

[0004] In view of the above problems, this application is proposed to provide a grid-connected overvoltage control system to achieve control of the grid-connected voltage fluctuations.

[0005] To achieve the above objective, the following specific solutions are proposed:

[0006] A grid-connected overvoltage control system includes: a voltage regulating converter, an overvoltage suppressor, and a power energy storage device. The voltage regulating converter converts the grid-connected alternating current into direct current and transmits it to the power energy storage device for charging and discharging. The overvoltage suppressor is communicatively connected to the voltage regulating converter and the power energy storage device, wherein:

[0007] The voltage regulating converter is configured to obtain the real-time load current signal of the grid connection, the voltage value of the direct current transmitted to the power energy storage device, and the highest allowable voltage value of the direct current, send the real-time load current signal to the overvoltage suppressor, obtain the rated charge and discharge power of the power energy storage device, and after receiving the grid-connected voltage margin and the predicted power value sequence sent by the overvoltage suppressor, determine the power adjustment value according to the grid-connected voltage margin, the predicted power value sequence, the voltage value of the direct current, the highest allowable voltage value of the direct current, and the rated charge and discharge power, and send the power adjustment value and the voltage value of the direct current to the overvoltage suppressor;

[0008] The power energy storage device is used to detect the charging and discharging power and the state of charge in the current state, obtain the real-time charging and discharging power and the real-time state of charge, and send the real-time charging and discharging power and the real-time state of charge to the overvoltage suppressor;

[0009] The overvoltage suppressor is used to obtain the real-time voltage signal of grid connection, obtain the charge capacity of the power energy storage device, after receiving the real-time load current signal sent by the voltage regulating converter, determine the real-time load power value with the real-time load current signal and the real-time voltage signal, obtain the predicted power value sequence of the next time period according to each real-time load power value in the current time period, obtain the grid connection voltage margin according to the preset grid connection voltage limit value and the real-time voltage signal, send the grid connection voltage margin and the predicted power value sequence to the voltage regulating converter, and after receiving the power regulation value, the voltage value of the DC current, and the real-time charging and discharging power and the real-time state of charge sent by the power energy storage device, determine the grid connection overvoltage regulation amount according to the power regulation value, the grid connection voltage margin, the real-time charging and discharging power, the real-time state of charge, and the charge capacity, and the grid connection overvoltage regulation amount is used to regulate the voltage of the grid connection.

[0010] Optionally, the process of the voltage regulating converter determining the power regulation value according to the grid connection voltage margin, the predicted power value sequence, the voltage value of the DC current, the highest allowable voltage value of the DC current, and the rated charging and discharging power includes:

[0011] When the grid connection voltage margin is not greater than zero and the load power values in the predicted power value sequence are not all greater than zero or all less than zero, in the order of the predicted power value sequence, the load power values less than zero in the predicted power value sequence are formed into a negative predicted power value sequence;

[0012] In the order of the predicted power value sequence, the load power values not less than zero in the predicted power value sequence are formed into a non-negative predicted power value sequence;

[0013] Subtract the minimum load power value in the negative predicted power value sequence from the maximum load power value in the negative predicted power value sequence to obtain the subtracted negative predicted power amplitude difference;

[0014] Subtract the minimum load power value in the non-negative predicted power value sequence from the maximum load power value in the non-negative predicted power value sequence to obtain the subtracted non-negative predicted power amplitude difference;

[0015] Take the average value of the negative predicted power amplitude difference and the non-negative predicted power amplitude difference as the load average fluctuation amount;

[0016] Subtract the first load power value in the predicted power value sequence from the maximum load power value in the predicted power value sequence to obtain a first value to be adjusted;

[0017] Subtract the minimum load power value in the predicted power value sequence from the first load power value in the predicted power value sequence to obtain a second value to be adjusted;

[0018] Multiply the load average fluctuation amount, the difference between the maximum and minimum values of the first value to be adjusted and the second value to be adjusted, and the reciprocal of the maximum value of the first value to be adjusted and the second value to be adjusted, and use the multiplication result as the power adjustment value.

[0019] Optionally, the voltage regulating converter is further configured to:

[0020] When the grid connection voltage margin is greater than zero, and the load power values greater than zero in the predicted power value sequence are not less than the positive power adjustment start value, and the absolute value of the load power values less than zero in the predicted power value sequence is not less than the negative power adjustment start value, multiply the reciprocal of the highest allowable voltage value of the DC current, the voltage value of the DC current, and the rated charge and discharge power to obtain the power adjustment value.

[0021] Optionally, the voltage regulating converter is further configured to:

[0022] When the grid connection voltage margin is not greater than zero, and the load power values in the predicted power value sequence are all greater than zero or all less than zero, use the average value of the maximum load power value and the minimum load power value in the predicted power value sequence as the load average fluctuation amount;

[0023] Subtract the first load power value in the predicted power value sequence from the maximum load power value in the predicted power value sequence to obtain a first value to be adjusted;

[0024] Subtract the minimum load power value in the predicted power value sequence from the first load power value in the predicted power value sequence to obtain a second value to be adjusted;

[0025] Multiply the load average fluctuation amount, the difference between the maximum and minimum values of the first value to be adjusted and the second value to be adjusted, and the reciprocal of the maximum value of the first value to be adjusted and the second value to be adjusted, and use the multiplication result as the power adjustment value.

[0026] Optionally, the voltage regulating converter includes a circuit breaker, and the circuit breaker controls the connection and disconnection of the voltage regulating converter to the grid connection;

[0027] Before determining the power adjustment value according to the grid-connected voltage margin, the predicted power value sequence, the voltage value of the DC current, the maximum allowable voltage value of the DC current, and the rated charge and discharge power, the voltage regulator converter further includes:

[0028] Judge whether the following conditions are all satisfied: the grid-connected voltage margin is greater than zero, the positive load power values greater than zero in the predicted power value sequence are less than a preset positive power adjustment start value, and the absolute value of the negative load power values less than zero in the predicted power value sequence is less than a preset negative power adjustment start value;

[0029] If so, the circuit breaker disconnects the connection between the voltage regulator converter and the grid.

[0030] Optionally, the process of the overvoltage suppressor determining the grid-connected overvoltage adjustment amount according to the power adjustment value, the grid-connected voltage margin, the real-time charge and discharge power, the real-time state of charge, and the state of charge capacity includes:

[0031] If the power adjustment value is greater than zero, multiply the grid-connected voltage margin, the reciprocal of the preset grid-connected voltage standard value, a preset first coefficient, and the power adjustment value, and use the multiplication result as the overvoltage power, where the grid-connected voltage standard value is less than the grid-connected voltage limit value;

[0032] Multiply a preset first state-of-charge coefficient by the state of charge capacity, and use the multiplication result as the reference state of charge;

[0033] Judge whether the following conditions are all satisfied: the real-time charge and discharge power is greater than the overvoltage power, and the real-time state of charge is less than the reference state of charge;

[0034] If not, subtract the real-time charge and discharge power from the overvoltage power, and use the subtraction result as the grid-connected overvoltage adjustment amount.

[0035] Optionally, the overvoltage suppressor is further configured to:

[0036] If the power adjustment value is not greater than zero, determine that the grid-connected overvoltage adjustment amount is zero;

[0037] Optionally, the overvoltage suppressor is further configured to:

[0038] If the real-time charge and discharge power is greater than the overvoltage power and the real-time state of charge is less than the reference state of charge, determine that the grid-connected overvoltage adjustment amount is zero.

[0039] Optionally, the process of the overvoltage suppressor obtaining the predicted power value sequence according to each real-time load power value in the current time period includes:

[0040] According to the time sequence corresponding to each real-time load power value in the current period, each real-time load power value in the current period is formed into a current power value sequence;

[0041] Through the current power value sequence, each load power value in the next period is predicted, and the duration of the next period is equal to that of the current period;

[0042] Each load power value in the predicted next period is formed into a predicted power value sequence.

[0043] Optionally, the overvoltage suppressor is communicatively connected to the photovoltaic power generation system, and the photovoltaic power generation system is connected to the grid through the transformer, and the transformer is used to control the voltage of the grid connection;

[0044] After determining the grid connection overvoltage regulation amount, it further includes:

[0045] The overvoltage suppressor sends the grid connection overvoltage regulation amount to the photovoltaic power generation system, so that the photovoltaic power generation system converts the grid connection overvoltage regulation amount into a current amplitude and phase, and the transformer adjusts the voltage of the grid connection according to the current amplitude and phase.

[0046] With the above technical solution, the present application obtains the real-time load current signal of the grid connection through a voltage regulating converter, as well as the voltage value of the DC current transmitted to the power energy storage device, and the maximum allowable voltage value of the DC current, and sends the real-time load current signal to the overvoltage suppressor, obtains the rated charge and discharge power of the power energy storage device, and after receiving the grid connection voltage margin and the predicted power value sequence sent by the overvoltage suppressor, determines a power adjustment value according to the grid connection voltage margin, the predicted power value sequence, the voltage value of the DC current, the maximum allowable voltage value of the DC current, and the rated charge and discharge power, and sends the power adjustment value and the voltage value of the DC current to the overvoltage suppressor; the power energy storage device detects the charge and discharge power and the state of charge in the current state to obtain the real-time charge and discharge power and the real-time state of charge, and sends the real-time charge and discharge power and the real-time state of charge to the overvoltage suppressor; the overvoltage suppressor obtains the real-time voltage signal of the grid connection, obtains the charge capacity of the power energy storage device, and after receiving the real-time load current signal sent by the voltage regulating converter, determines the real-time load power value with the real-time load current signal and the real-time voltage signal, obtains the predicted power value sequence for the next time period according to each real-time load power value in the current time period, obtains the grid connection voltage margin according to the preset grid connection voltage limit value and the real-time voltage signal, and sends the grid connection voltage margin and the predicted power value sequence to the voltage regulating converter, and after receiving the power adjustment value, the voltage value of the DC current sent by the voltage regulating converter, and the real-time charge and discharge power and the real-time state of charge sent by the power energy storage device, determines the grid connection overvoltage adjustment amount according to the power adjustment value, the grid connection voltage margin, the real-time charge and discharge power, the real-time state of charge, and the charge capacity, and the grid connection overvoltage adjustment amount is used to adjust the voltage of the grid connection. Thus, compared with the traditional maximum power point tracking method, this solution effectively controls the abnormal voltage fluctuations of the grid connection in real time by jointly using the voltage regulating converter and the overvoltage suppressor to obtain the electrical energy parameters of the grid connection in real time, avoiding the increase of voltage fluctuations, effectively improving the qualified rate of the grid connection voltage, and thus improving the electrical energy quality of the grid connection. Description of the Drawings

[0047] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0048] Figure 1 It is a system architecture diagram for implementing grid connection overvoltage control provided by an embodiment of the present application;

[0049] Figure 2 It is an internal component architecture diagram of a system for implementing grid connection overvoltage control provided by an embodiment of the present application;

[0050] Figure 3 It is a schematic flowchart of a process for determining a power adjustment value provided by an embodiment of the present application;

[0051] Figure 4 It is a schematic flowchart of a process for determining a grid-connected overvoltage adjustment amount provided by an embodiment of the present application. Detailed implementation manners

[0052] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0053] Figure 1 It is an optional system architecture for grid-connected overvoltage control provided by an embodiment of the present application. As Figure 1 shown, the system architecture may include a voltage regulating converter 10, an overvoltage suppressor 20, and a power energy storage device 30.

[0054] Among them, the voltage regulating converter 10, the overvoltage suppressor 20, and the power energy storage device 30 all support the functions of sending and receiving information, and can display each result in the processing process in real time. The voltage regulating converter 10 converts the grid-connected alternating current into direct current and transmits it to the power energy storage device 30 for charging and discharging, and the overvoltage suppressor 20 is connected to the voltage regulating converter 10 and the power energy storage device 30.

[0055] The specific operation process of this system may include:

[0056] The voltage regulating converter 10 is used to obtain the real-time load current signal of the grid-connected bus, the voltage value of the direct current transmitted to the power energy storage device 30, and the highest allowable voltage value of the direct current, send the real-time load current signal to the overvoltage suppressor 20, obtain the rated charge and discharge power of the power energy storage device 30, determine the power adjustment value after receiving the grid-connected voltage margin and the predicted power value sequence sent by the overvoltage suppressor 20, and send the power adjustment value and the voltage value of the direct current to the overvoltage suppressor 20.

[0057] The overvoltage suppressor 20 is used to obtain the real-time grid-connected voltage signal and the state of charge of the power energy storage device 30. After receiving the real-time load current signal, it determines the real-time load power value based on the real-time load current signal and the real-time voltage signal. According to the real-time load power values in the current period, it obtains the predicted power value sequence for the next period. According to the preset grid-connected voltage limit and the real-time voltage signal, it obtains the grid-connected voltage margin, and sends the grid-connected voltage margin and the predicted power value sequence to the voltage regulating converter 10. After receiving the power adjustment value, the voltage value of the direct current, and the real-time charge-discharge power and the real-time state of charge sent by the power energy storage device 30, it determines the grid-connected overvoltage adjustment amount, and the grid-connected overvoltage adjustment amount is used to adjust the grid-connected voltage.

[0058] Specifically, the process by which the overvoltage suppressor 20 determines the real-time load power value based on the real-time load current signal and the real-time voltage signal can be to multiply the real-time load current signal, the real-time voltage signal, and the cosine value of the vector angle between the load current signal and the real-time voltage signal to obtain the load power value. The process by which the overvoltage suppressor 20 obtains the grid-connected voltage margin according to the preset grid-connected voltage limit and the real-time voltage signal can be to multiply the grid-connected voltage limit by the preset voltage safety value to obtain the grid-connected voltage safety limit, then subtract the voltage value of the real-time voltage signal from the grid-connected voltage safety limit to obtain the grid-connected safety overvoltage value, and finally divide the grid-connected safety overvoltage value by the preset voltage standard value to obtain the grid-connected voltage margin.

[0059] The power energy storage device 30 is used to detect the charge-discharge power and the state of charge in the current state, obtain the real-time charge-discharge power and the real-time state of charge, and send the real-time charge-discharge power and the real-time state of charge to the overvoltage suppressor 20.

[0060] What can be achieved in this application is that the voltage regulating converter 10 obtains the real-time load current signal of grid connection, as well as the voltage value of the DC current transmitted to the power energy storage device 30, and the maximum allowable voltage value of the DC current, sends the real-time load current signal to the overvoltage suppressor 20, obtains the rated charge-discharge power of the power energy storage device 30, and after receiving the grid connection voltage margin and the predicted power value sequence sent by the overvoltage suppressor 20, determines a power regulation value according to the grid connection voltage margin, the predicted power value sequence, the voltage value of the DC current, the maximum allowable voltage value of the DC current, and the rated charge-discharge power, and sends the power regulation value and the voltage value of the DC current to the overvoltage suppressor 20; the power energy storage device 30 detects the charge-discharge power and the state of charge in the current state, obtains the real-time charge-discharge power and the real-time state of charge, and sends the real-time charge-discharge power and the real-time state of charge to the overvoltage suppressor 20; the overvoltage suppressor 20 obtains the real-time voltage signal of grid connection, obtains the charge capacity of the power energy storage device 30, and after receiving the real-time load current signal sent by the voltage regulating converter 10, determines the real-time load power value with the real-time load current signal and the real-time voltage signal, obtains the predicted power value sequence of the next time period according to each real-time load power value in the current time period, obtains the grid connection voltage margin according to the preset grid connection voltage limit value and the real-time voltage signal, sends the grid connection voltage margin and the predicted power value sequence to the voltage regulating converter 10, and after receiving the power regulation value sent by the voltage regulating converter 10, the voltage value of the DC current, and the real-time charge-discharge power and the real-time state of charge sent by the power energy storage device 30, determines the grid connection overvoltage regulation amount according to the power regulation value, the grid connection voltage margin, the real-time charge-discharge power, the real-time state of charge, and the charge capacity, and the grid connection overvoltage regulation amount is used to regulate the voltage of the grid connection. Thus, compared with the traditional maximum power point tracking method, this solution effectively controls the abnormal voltage fluctuations of the grid connection in real time by jointly using the voltage regulating converter 10 and the overvoltage suppressor 20 to obtain the electrical energy parameters of the grid connection in real time, avoids the increase of voltage fluctuations, effectively improves the qualification rate of the grid connection voltage, and thus improves the electrical energy quality of the grid connection.

[0061] Based on Figure 1 the system architecture shown, Figure 2 FIG. shows an internal component architecture of a grid connection overvoltage control provided by an embodiment of the present application. Referring to Figure 2 , the internal component architecture of this system may include:

[0062] The voltage regulating converter 10 may include a circuit breaker 101, a power regulator 102, and an AC-DC inverter 103.

[0063] Among them, one end of the circuit breaker 101 can obtain grid-connected alternating current from the grid-connected bus through an external circuit, and the other end is connected to the AC-DC inverter 103 to transmit the grid-connected alternating current to the AC-DC inverter 103. The circuit breaker 101 is communicatively connected to the power regulator 102. The AC-DC inverter 103 is used to convert the alternating current into direct current and output it. The AC-DC inverter 103 is communicatively connected to the power regulator 102. The power regulator 102 can obtain the real-time load current signal of the grid connection through an external current transformer and can obtain the voltage value of the direct current output by the AC-DC inverter 103.

[0064] The overvoltage suppressor 20 may include a power controller 201, a voltage monitoring unit 202, and a communication interface module 203.

[0065] Among them, the power controller 201 is connected to the voltage monitoring unit 202 and the communication interface module 203. The voltage monitoring unit 202 can obtain the real-time voltage signal from the grid-connected bus through an external voltage terminal. The voltage monitoring unit 202 is connected to the communication interface module 203.

[0066] In addition, the communication interface module 203 is communicatively connected to the photovoltaic grid-connected power generation system and is used to transmit the grid-connected overvoltage regulation amount to the photovoltaic grid-connected power generation system.

[0067] The power energy storage device 30 may include a DC energy storage module 301, a power detector 302, and a state-of-charge detector 303.

[0068] Among them, the DC energy storage module 301 is communicatively connected to the power detector 302 and the state-of-charge detector 303 respectively. The power detector 302 can detect the charge and discharge power in the current state from the DC energy storage module 301, and the state-of-charge detector 303 can detect the state of charge in the current state from the DC energy storage module 301.

[0069] The specific operation process of the system may include:

[0070] Specifically, the process of the voltage regulating converter 10 obtaining the real-time load current signal of the grid-connected bus, transmitting the voltage value of the direct current to the power energy storage device 30, and the highest allowable voltage value of the direct current, sending the real-time load current signal to the overvoltage suppressor 20, obtaining the rated charge and discharge power of the power energy storage device 30, receiving the grid-connected voltage margin and the predicted power value sequence, determining the power regulation value, and sending the power regulation value and the voltage value of the direct current to the overvoltage suppressor 20 can be executed by the power regulator 102.

[0071] Specifically, the process of the overvoltage suppressor 20 obtaining the real-time grid-connected voltage signal can be executed by the voltage monitoring unit 202, and the voltage monitoring unit 202 can transmit the real-time voltage signal to the power controller 201. The overvoltage suppressor 20 obtains the charge capacity of the power energy storage device 30, receives the real-time load current signal, determines the real-time load power value based on the real-time load current signal and the real-time voltage signal, obtains a predicted power value sequence for the next time period according to each real-time load power value in the current time period, obtains the grid-connected voltage margin based on the preset grid-connected voltage limit value and the real-time voltage signal, and sends the grid-connected voltage margin and the predicted power value sequence to the voltage regulating converter 10. The process of receiving the power regulation value, the voltage value of the direct current, and the real-time charge and discharge power and the real-time charge amount sent by the power energy storage device 30 sent by the voltage regulating converter 10 and determining the grid-connected overvoltage regulation amount can be executed by the power controller 201.

[0072] Specifically, the process of the power energy storage device 30 detecting the charge and discharge power in the current state to obtain the real-time charge and discharge power and sending the real-time charge and discharge power to the overvoltage suppressor 20 can be executed by the power detector 302. The process of the power energy storage device 30 detecting the charge amount in the current state to obtain the real-time charge amount and sending the real-time charge amount to the overvoltage suppressor 20 can be executed by the charge amount detector 303.

[0073] In some embodiments of the present application, the process of the overvoltage suppressor 20 obtaining a predicted power value sequence for the next time period according to each real-time load power value in the current time period is introduced, and this process may include:

[0074] S1. According to the time sequence corresponding to each real-time load power value in the current time period, form the real-time load power values in the current time period into a current power value sequence.

[0075] It can be understood that the overvoltage suppressor 20 can store the obtained real-time load power value each time and the time information corresponding to the real-time load power value, obtain the real-time load power value every preset fixed time, and since the current time period is greater than the preset fixed time, there are multiple real-time load power values in the current time period.

[0076] For example, it can be set to obtain the real-time load power value every 5 minutes. The real-time load power value obtained at 9:00 can be 1000W, the real-time load power value obtained at 9:05 can be 2000W, the real-time load power value obtained at 9:10 can be 3000W, and the real-time load power value obtained at 9:15 can be 4000W. Then the current power value sequence is [1000W, 2000W, 3000W, 4000W].

[0077] S2. Predict the load power values for the next time period based on the current power value sequence.

[0078] Specifically, the prediction method can adopt the linear regression prediction method. The duration of the next time period is equal to that of the current time period. For example, if the current time period is from 9:00 to 9:15, then the next time period can be from 9:20 to 9:35. Therefore, the number of load power values in the next time period is equal to that in the current time period.

[0079] For example, if the current power value sequence is [1000W, 2000W, 3000W, 4000W], then the first power value in the predicted next time period is 5000W, the second power value in the next time period is 6000W, the third power value in the next time period is 7000W, and the fourth power value in the next time period is 8000W.

[0080] S3. Combine the predicted load power values for the next time period into a predicted power value sequence.

[0081] Specifically, the overvoltage suppressor 20 can store the time corresponding to each predicted load power value, and each predicted load power value can be combined into a predicted power value sequence in chronological order.

[0082] For example, if the predicted real-time load power value obtained at 9:20 can be 5000W, the predicted real-time load power value obtained at 9:25 can be 6000W, the predicted real-time load power value obtained at 9:30 can be 7000W, and the predicted real-time load power value obtained at 9:35 can be 8000W, then the predicted power value sequence is [5000W, 6000W, 7000W, 8000W].

[0083] The grid-connected overvoltage control method provided in this embodiment can scientifically analyze the future trend of the grid-connected voltage by predicting the load power values for the next time period based on the load power values in the current time period, so as to provide a reasonable reference quantity for subsequent calculation of the power adjustment value.

[0084] In some embodiments of the present application, the process of determining the power adjustment value for the above voltage regulating converter 10 is introduced, and this process can be referred to Figure 3 as shown.

[0085] Specifically, the voltage regulating converter 10 can determine the power adjustment value according to the grid-connected voltage margin, the predicted power value sequence, the voltage value of the DC current, the maximum allowable voltage value of the DC current, and the rated charge and discharge power.

[0086] This process can include:

[0087] Step S401: Determine whether the grid-connected voltage margin is greater than 0. If so, execute Step S402; if not, execute Step S406.

[0088] Specifically, the grid-connected voltage margin can represent the reasonable fluctuation range of the grid-connected voltage, and the grid-connected voltage margin can be used as one of the reference quantities for the amplitude of the grid-connected voltage adjustment.

[0089] Step S402: Determine whether the load power values greater than zero in the predicted power value sequence are less than a preset positive power adjustment start value. If so, execute Step S403; if not, execute Step S405.

[0090] Step S403: Determine whether the load power values less than zero in the predicted power value sequence are less than a preset negative power adjustment start value. If so, execute Step S404; if not, execute Step S405.

[0091] Step S404: The circuit breaker 101 disconnects the connection between the voltage regulating converter 10 and the grid.

[0092] It can be understood that when the grid-connected voltage margin is greater than zero, and the load power values greater than zero in the predicted power value sequence are less than the preset positive power adjustment start value, and the absolute value of the load power values less than zero in the predicted power value sequence is less than the preset negative power adjustment start value, it can indicate that the predicted voltages in the next time period are all within the reasonable fluctuation range and no voltage adjustment is required. Therefore, the circuit breaker 101 disconnects the connection between the voltage regulating converter 10 and the grid to reduce the energy loss generated by the inverter during the no-load standby period. Among them, the no-load standby period can be the period from 6 pm to 6 am the next day.

[0093] Step S405: Multiply the reciprocal of the maximum allowable voltage value of the DC current, the voltage value of the DC current, and the rated charge and discharge power to obtain a power adjustment value.

[0094] For example, the maximum allowable voltage value of the DC current can be 400V, the voltage value of the DC voltage can be 320V, and the rated charge and discharge power can be 10000W. Then the obtained power adjustment value is 8000W.

[0095] Step S406: Determine whether all the load power values in the predicted power value sequence are greater than 0 or all less than 0. If so, execute Step S407; if not, execute Step S408.

[0096] Step S407: Take the average value of the maximum load power value and the minimum load power value in the predicted power value sequence as the load average fluctuation amount.

[0097] Specifically, the load average fluctuation amount can represent the fluctuation amplitude of the power corresponding to the grid-connected voltage in the predicted next time period.

[0098] For example, the predicted power value sequence can be [1000W, 2000W, 3000W, 4000W]. Since the load power values in this predicted power value sequence are all greater than 0, the average load fluctuation amount is 2500W.

[0099] Another example, the predicted power value sequence can be [-1000W, -2000W, -3000W, -4000W]. Since the load power values in this predicted power value sequence are all less than 0, the average load fluctuation amount is -2500W.

[0100] Step S408: According to the order of the predicted power value sequence, form a negative predicted power value sequence with the load power values less than zero in the predicted power value sequence.

[0101] For example, the predicted power value sequence can be [1000W, -2000W, 3000W, -4000W]. Then the load power values less than zero in the predicted power value sequence are -2000W and -4000W. Therefore, the negative predicted power value sequence is [-2000W, -4000W].

[0102] Step S409: Subtract the minimum load power value from the maximum load power value in the negative predicted power value sequence to obtain the subtracted negative predicted power amplitude difference.

[0103] Specifically, the negative predicted power amplitude difference can represent the fluctuation amplitude of the power corresponding to the negative voltage of the grid-connected voltage in the next time period.

[0104] For example, the negative predicted power value sequence can be [-2000W, -4000W]. The maximum load power value is -2000W and the minimum load power value is -4000W. Then the negative predicted power amplitude difference is 2000W.

[0105] Step S410: According to the order of the predicted power value sequence, form a non-negative predicted power value sequence with the load power values not less than zero in the predicted power value sequence.

[0106] For example, the predicted power value sequence can be [1000W, -2000W, 3000W, -4000W]. Then the load power values greater than zero in the predicted power value sequence are 1000W and 3000W. Therefore, the negative predicted power value sequence is [1000W, 3000W].

[0107] Step S411: Subtract the minimum load power value from the maximum load power value in the non-negative predicted power value sequence to obtain the subtracted non-negative predicted power amplitude difference.

[0108] Specifically, the non-negative predicted power amplitude difference may represent the power fluctuation amplitude corresponding to the positive voltage of the grid-connected voltage predicted in the next time period.

[0109] For example, the non-negative predicted power value sequence may be [1000W, 3000W], where the maximum load power value is 3000W and the minimum load power value is 1000W, and the non-negative predicted power amplitude difference is 2000W.

[0110] It can be understood that this step and step S410 are the processing processes of non-negative predicted power value sequences, and have no influence on the processing processes of negative predicted power value sequences of steps S408 and S409. Based on this, the execution order of the step combination of step S408 and step S409 and the step combination of step S410 and step S411 can be in no particular order.

[0111] Step S412: taking the average value of the negative predicted power amplitude difference and the non-negative predicted power amplitude difference as the average load fluctuation.

[0112] For example, the negative predicted power amplitude difference may be 2000W, and the non-negative predicted power amplitude difference may be 2000W, then the average load fluctuation is 2000W.

[0113] Step S413: subtract the first load power value in the predicted power value sequence from the maximum load power value in the predicted power value sequence to obtain a first value to be adjusted.

[0114] For example, the predicted power value sequence may be [1000W, 2000W, 3000W, 4000W], then the maximum load power value is 4000W, the first load power value is 1000W, and the first value to be adjusted is 3000W.

[0115] Step S414: subtract the minimum load power value in the predicted power value sequence from the first load power value in the predicted power value sequence to obtain a second value to be adjusted.

[0116] For example, the predicted power value sequence may be [1000W, 2000W, 3000W, 4000W], then the minimum load power value is 1000W, the first load power value is 1000W, then the first value to be adjusted is 0.

[0117] Step S415: multiply the average load fluctuation, the difference between the maximum and minimum values of the first value to be adjusted and the second value to be adjusted, and the reciprocal of the maximum value of the first value to be adjusted and the second value to be adjusted to obtain a power adjustment value.

[0118] For example, the average load fluctuation amount can be 2500 W, the first value to be adjusted can be 3000 W, and the second value to be adjusted can be 0. Then, the obtained power adjustment value is 2500 W.

[0119] The grid-connected overvoltage control method provided in this embodiment can calculate the power adjustment value according to different situations by judging whether the grid-connected voltage margin is greater than 0, judging whether the load power values greater than zero in the predicted power value sequence are less than the preset positive power adjustment start value, judging whether the load power values less than zero in the predicted power value sequence are less than the preset negative power adjustment start value, and judging whether the load power values in the predicted power value sequence are all greater than 0 or all less than 0, so as to effectively control the fluctuation of the grid-connected voltage.

[0120] In some embodiments of the present application, the process of determining the grid-connected overvoltage adjustment amount by the above overvoltage suppressor 20 is introduced, and this process can be referred to Figure 4 as shown.

[0121] Specifically, the grid-connected overvoltage adjustment amount can be used to adjust the voltage of the grid connection. The overvoltage suppressor 20 can determine the grid-connected overvoltage adjustment amount according to the power adjustment value, the grid-connected voltage margin, the real-time charge and discharge power, the real-time state of charge, and the charge capacity.

[0122] This process may include:

[0123] Step S501: Judge whether the power adjustment value is greater than 0. If so, execute step S502; if not, execute step S505.

[0124] Step S502: Multiply the grid-connected voltage margin, the reciprocal of the preset grid-connected voltage standard value, the preset first coefficient, and the power adjustment value to obtain the overvoltage power.

[0125] For example, the grid-connected voltage margin can be 0.02, the preset grid-connected voltage standard value can be 400 V, the preset first coefficient can be 10, and the power adjustment value can be 2500 W. Then, the overvoltage power is 1.25 W.

[0126] Step S503: Multiply the preset first state-of-charge coefficient by the charge capacity, and use the multiplication result as the reference state of charge.

[0127] For example, the preset first state-of-charge coefficient can be 0.95, and the charge capacity can be 2 C. Then, the reference state of charge is 1.9 C.

[0128] Step S504: Judge whether the following adjustments are all established: the real-time charge and discharge power is greater than the overvoltage power, and the real-time state of charge is less than the reference state of charge. If so, execute step S505; if not, execute step S506.

[0129] Step S505: Determine that the grid-connected overvoltage regulation amount is 0.

[0130] Specifically, when the overvoltage power does not reach the real-time charge-discharge power and the state of charge still does not reach the reference state of charge, it indicates that the grid-connected voltage still does not reach the voltage standard value and overvoltage control is not required. Therefore, the grid-connected overvoltage regulation amount is determined to be 0.

[0131] Step S506: Subtract the real-time charge-discharge power from the overvoltage power, and use the result after subtraction as the grid-connected overvoltage regulation amount.

[0132] Specifically, when the real-time charge-discharge power is not greater than the overvoltage power, or the real-time state of charge is not less than the reference state of charge, it indicates that the grid-connected voltage has exceeded the voltage standard value, and overvoltage control is required at this time. For example, the overvoltage power can be 40W and the real-time charge-discharge power can be 20W, then the obtained grid-connected overvoltage regulation amount is 20W.

[0133] In the grid-connected overvoltage control method provided in this embodiment, the overvoltage suppressor 20 can calculate the grid-connected overvoltage regulation amount according to different situations by judging whether the power regulation value is greater than 0, whether the real-time charge-discharge power is greater than the overvoltage power, and whether the real-time state of charge is less than the reference state of charge. The grid-connected overvoltage regulation amount is adjusted by the power regulation value of the voltage regulating converter 10, so as to realize the real-time overvoltage control calculation by combining the voltage regulating converter 10 and the overvoltage suppressor 20, so as to effectively control the fluctuation of the grid-connected voltage.

[0134] As Figure 1 shown, the overvoltage suppressor 20 is communicatively connected to the photovoltaic power generation system. The photovoltaic power generation system is connected to the transformer through grid connection, and the transformer is used to control the voltage of the grid connection. Based on this, in some embodiments of the present application, the process of the overvoltage suppressor 20 adjusting the grid-connected voltage according to the grid-connected overvoltage regulation amount after determining the grid-connected overvoltage regulation amount is introduced. This process may include:

[0135] The overvoltage suppressor 20 sends the grid-connected overvoltage regulation amount to the photovoltaic power generation system.

[0136] Specifically, the overvoltage suppressor 20 sends the grid-connected overvoltage regulation amount to the photovoltaic power generation system. The photovoltaic power generation system may include a photovoltaic inverter, and the photovoltaic inverter may convert the grid-connected overvoltage regulation amount into current amplitude and phase. The transformer may adjust the real-time active and reactive power of the transformer according to the current amplitude and phase, so as to adjust the low-voltage side voltage of the transformer and act on the grid connection.

[0137] In the grid-connected overvoltage control method provided in this embodiment, the grid-connected overvoltage regulation amount is transmitted to the photovoltaic power generation system through the overvoltage suppressor 20, and the transformer is controlled by the photovoltaic power generation system, achieving the effect of controlling the grid-connected voltage.

[0138] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0139] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0140] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A grid-connected overvoltage control system, characterized in that, Including: A voltage regulating inverter, an overvoltage suppressor, and a power energy storage device. The voltage regulating inverter converts the grid-connected alternating current into direct current and transmits it to the power energy storage device for charging and discharging. The overvoltage suppressor is communicatively connected to the voltage regulating inverter and the power energy storage device, where: The voltage regulating inverter is configured to obtain the real-time load current signal of the grid connection, the voltage value of the direct current transmitted to the power energy storage device, and the maximum allowable voltage value of the direct current, send the real-time load current signal to the overvoltage suppressor, obtain the rated charge and discharge power of the power energy storage device, and after receiving the grid connection voltage margin and the predicted power value sequence sent by the overvoltage suppressor, determine a power regulation value according to the grid connection voltage margin, the predicted power value sequence, the voltage value of the direct current, the maximum allowable voltage value of the direct current, and the rated charge and discharge power, and send the power regulation value and the voltage value of the direct current to the overvoltage suppressor; The power energy storage device is configured to detect the charge and discharge power and the state of charge in the current state, obtain the real-time charge and discharge power and the real-time state of charge, and send the real-time charge and discharge power and the real-time state of charge to the overvoltage suppressor; The overvoltage suppressor is configured to obtain the real-time voltage signal of the grid connection, obtain the charge capacity of the power energy storage device, determine the real-time load power value based on the real-time load current signal and the real-time voltage signal after receiving the real-time load current signal sent by the voltage regulating inverter, obtain the predicted power value sequence for the next time period according to the real-time load power values in the current time period, obtain the grid connection voltage margin according to the preset grid connection voltage limit and the real-time voltage signal, send the grid connection voltage margin and the predicted power value sequence to the voltage regulating inverter, and after receiving the power regulation value, the voltage value of the direct current sent by the voltage regulating inverter, and the real-time charge and discharge power and the real-time state of charge sent by the power energy storage device, determine the grid connection overvoltage regulation amount according to the power regulation value, the grid connection voltage margin, the real-time charge and discharge power, the real-time state of charge, and the charge capacity, and the grid connection overvoltage regulation amount is used to regulate the voltage of the grid connection.

2. The system according to claim 1, wherein The process by which the voltage regulating inverter determines the power regulation value according to the grid connection voltage margin, the predicted power value sequence, the voltage value of the direct current, the maximum allowable voltage value of the direct current, and the rated charge and discharge power includes: When the grid connection voltage margin is not greater than zero and the load power values in the predicted power value sequence are not all greater than zero or all less than zero, in the order of the predicted power value sequence, form a negative predicted power value sequence from the load power values less than zero in the predicted power value sequence; In the order of the predicted power value sequence, form a non-negative predicted power value sequence from the load power values not less than zero in the predicted power value sequence; Subtract the minimum load power value in the negative predicted power value sequence from the maximum load power value in the negative predicted power value sequence to obtain the subtracted negative predicted power amplitude difference; Subtract the minimum load power value in the non - negative predicted power value sequence from the maximum load power value in the non - negative predicted power value sequence to obtain the non - negative predicted power amplitude difference after subtraction; Take the average value of the negative predicted power amplitude difference and the non - negative predicted power amplitude difference as the load average fluctuation amount; Subtract the first load power value in the predicted power value sequence from the maximum load power value in the predicted power value sequence to obtain the first value to be adjusted; Subtract the minimum load power value in the predicted power value sequence from the first load power value in the predicted power value sequence to obtain the second value to be adjusted; Multiply the load average fluctuation amount, the difference between the maximum and minimum values of the first value to be adjusted and the second value to be adjusted, and the reciprocal of the maximum value of the first value to be adjusted and the second value to be adjusted, and use the result of the multiplication as the power adjustment value.

3. The system according to claim 2, wherein The voltage regulating converter is further configured to: When the grid - connected voltage margin is greater than zero, and the load power values greater than zero in the predicted power value sequence are not less than a preset positive power adjustment start value, and the absolute value of the load power values less than zero in the predicted power value sequence is not less than a preset negative power adjustment start value, multiply the reciprocal of the highest allowable voltage value of the DC current, the voltage value of the DC current, and the rated charge - discharge power to obtain the power adjustment value.

4. The system according to claim 2, wherein The voltage regulating converter is further configured to: When the grid - connected voltage margin is not greater than zero, and the load power values in the predicted power value sequence are all greater than zero or all less than zero, take the average value of the maximum load power value and the minimum load power value in the predicted power value sequence as the load average fluctuation amount; Subtract the first load power value in the predicted power value sequence from the maximum load power value in the predicted power value sequence to obtain the first value to be adjusted; Subtract the minimum load power value in the predicted power value sequence from the first load power value in the predicted power value sequence to obtain the second value to be adjusted; Multiply the load average fluctuation amount, the difference between the maximum and minimum values of the first value to be adjusted and the second value to be adjusted, and the reciprocal of the maximum value of the first value to be adjusted and the second value to be adjusted, and use the result of the multiplication as the power adjustment value.

5. The system according to claim 1, wherein, The voltage regulating converter includes a circuit breaker, and the circuit breaker controls the connection and disconnection of the voltage regulating converter and the grid connection; Before the voltage regulating converter determines the power adjustment value according to the grid - connected voltage margin, the predicted power value sequence, the voltage value of the DC current, the highest allowable voltage value of the DC current, and the rated charge - discharge power, it further includes: Judge whether the following conditions are all satisfied: the grid - connected voltage margin is greater than zero, the load power values greater than zero in the predicted power value sequence are less than a preset positive power adjustment start value, and the absolute value of the load power values less than zero in the predicted power value sequence is less than a preset negative power adjustment start value; If so, the circuit breaker disconnects the connection between the voltage regulating converter and the grid.

6. The system according to claim 1, wherein The process by which the overvoltage suppressor determines the grid-connected overvoltage adjustment amount based on the power adjustment value, the grid-connected voltage margin, the real-time charge-discharge power, the real-time state of charge, and the charge capacity includes: If the power adjustment value is greater than zero, multiply the grid-connected voltage margin, the reciprocal of a preset grid-connected voltage standard value, a preset first coefficient, and the power adjustment value, and use the multiplication result as the overvoltage power, where the grid-connected voltage standard value is less than the grid-connected voltage limit value; Multiply a preset first state-of-charge coefficient by the charge capacity, and use the multiplication result as the reference state of charge; Judge whether the following conditions are all satisfied: the real-time charge-discharge power is greater than the overvoltage power, and the real-time state of charge is less than the reference state of charge; If not, subtract the real-time charge-discharge power from the overvoltage power, and use the result of the subtraction as the grid-connected overvoltage adjustment amount.

7. The system according to claim 6, wherein The overvoltage suppressor is further configured to: If the power adjustment value is not greater than zero, determine that the grid-connected overvoltage adjustment amount is zero.

8. The system according to claim 6, wherein The overvoltage suppressor is further configured to: If the real-time charge-discharge power is greater than the overvoltage power and the real-time state of charge is less than the reference state of charge, determine that the grid-connected overvoltage adjustment amount is zero.

9. The system according to claim 1, wherein The process by which the overvoltage suppressor obtains a predicted power value sequence based on the real-time load power values in the current time period includes: According to the time sequence corresponding to the real-time load power values in the current time period, form the real-time load power values in the current time period into a current power value sequence; Predict the load power values in the next time period through the current power value sequence, where the duration of the next time period is equal to that of the current time period; Form the predicted load power values in the next time period into a predicted power value sequence.

10. The system according to claim 1, characterized in that, The overvoltage suppressor is communicatively connected to the photovoltaic power generation system, and the photovoltaic power generation system is connected to the grid through the transformer, and the transformer is used to control the voltage of the grid connection, After determining the grid-connected overvoltage adjustment amount, it further includes: The overvoltage suppressor sends the grid-connected overvoltage adjustment amount to the photovoltaic power generation system, so that the photovoltaic power generation system converts the grid-connected overvoltage adjustment amount into a current amplitude and phase, and the transformer adjusts the voltage of the grid connection according to the current amplitude and phase.

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