Anti-countercurrent and anti-overload method, device and system for optical storage power station

Abstract

The invention relates to an anti-countercurrent and anti-overload method, device and system for an optical storage power station. The method comprises the steps of obtaining a first power generation time period, a second power generation time period and photovoltaic output power based on meteorological data, a local electricity price scheme in each time period and preset intensity; load power and energy storage allowable charging power are predicted; controlling the power grid to charge the energy storage device in the first power generation period, and controlling the photovoltaic power generation device and the power grid to charge the energy storage device in the second power generation period; comparing the anti-countercurrent power threshold with the power grid output power, and adjusting the photovoltaic output power and the energy storage output power; and setting a maximum demand limit value, a demand control margin value and a power reduction margin value, and adjusting the energy storage allowable charging power of the energy storage device. According to the invention, countercurrent prevention and overload prevention are effectively ensured under the condition that the optical storage power station fully utilizes the electric energy of the photovoltaic power generation device, the operation cost of the power station is reduced, and stable circulation of self-generation and self-use of the electric energy of the power station is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic energy storage, and particularly to a method, device and system for preventing reverse current and overload in a photovoltaic energy storage power station. Background Art

[0002] A photovoltaic energy storage power station is a facility that combines photovoltaic power generation and an energy storage system, and is widely used in factories with large electricity demands. It is for the factories to use electricity generated by themselves. The photovoltaic power generation device converts solar energy into electrical energy during the day. The electrical energy is first supplied to the factory for use, and the excess electrical energy is stored in the energy storage device. During the night or when the grid electricity price is high, the energy storage device releases electrical energy to supply the factory with electricity, effectively reducing the cost of factory electricity consumption.

[0003] During the operation of a photovoltaic energy storage power station, it is easy to have a reverse current to the grid due to excessive photovoltaic output electrical energy, and an overload phenomenon where the charging power of the energy storage system is too large, resulting in the total power of the enterprise exceeding the maximum demand. In the prior art, usually, the photovoltaic power generation power is reduced in real time according to the detected photovoltaic power generation device and grid power data to prevent reverse current, and the maximum demand control technology is used to prevent overload. However, this cannot make full use of the photovoltaic energy, causing resource waste. Moreover, the maximum demand control technology only simply compares the grid power data with the maximum demand value and reduces the charging power of the energy storage device in real time, without reserving a suitable equipment response time and tolerance, resulting in unstable demand control and easily causing the phenomenon of exceeding the maximum demand. Summary of the Invention

[0004] The present application provides a method, device and system for preventing reverse current and overload in a photovoltaic energy storage power station.

[0005] The method, device and system for preventing reverse current and overload in a photovoltaic energy storage power station provided by the present application adopt the following technical solutions:

[0006] A method for preventing reverse current and overload in a photovoltaic energy storage power station includes:

[0007] S1: Obtain meteorological data, local electricity price plans for each time period, and a preset intensity, and obtain a first power generation time period, a second power generation time period, and a photovoltaic output power according to the meteorological data and the local electricity price plans for each time period;

[0008] S2: Obtain user historical data, and predict the load power and the energy storage allowable charging power for the next 24 hours according to the user historical data;

[0009] S3: Control the grid to charge the energy storage device with the energy storage allowable charging power during the first power generation time period, and control the photovoltaic power generation device and the grid to charge the energy storage device with the sum of the photovoltaic output power and the grid output power not greater than the energy storage allowable charging power during the second power generation time period in the order of giving priority to the photovoltaic power generation device;

[0010] S4: Preset a maximum demand limit value according to the user's electricity consumption last month, set a demand control margin value and a power reduction margin value, and adjust the allowable charging power of the energy storage according to the maximum demand limit value, the demand control margin value, and the power reduction margin value;

[0011] S5: After the energy storage device is fully charged, control at least one of the photovoltaic power generation device, the energy storage device, and the power grid to output electric energy to the load, and set an anti-reverse load control mode. The anti-reverse load control mode includes setting an anti-counterflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase electricity from the power grid to carry the load, and obtain the power grid output power on the main electricity meter. Compare the power grid output power with the anti-counterflow power threshold. When the power grid output power is less than the anti-counterflow power threshold, preferentially reduce the energy storage output power, and then reduce the photovoltaic output power until the power grid output power exceeds the power increase threshold.

[0012] Preferably, the meteorological data is the light intensity data within the next 24 hours; the local electricity price plan for each period is the distribution plan of peak electricity periods and valley electricity periods within the next 24 hours; the first power generation period is the period when the light intensity is less than the preset intensity during the valley electricity period; the second power generation period is the period when the light intensity is greater than the preset intensity during the valley electricity period; the photovoltaic output power is the average power generation power of the photovoltaic power generation device per hour during the second power generation period.

[0013] Preferably, in the order of giving priority to the photovoltaic power generation device for power generation, controlling the photovoltaic power generation device and the power grid to charge the energy storage device within the second power generation period with the sum of the photovoltaic output power and the power grid output power not greater than the allowable charging power of the energy storage includes:

[0014] When the difference between the photovoltaic output power and the load power is greater than 0 kW and less than the allowable charging power of the energy storage, control the photovoltaic power generation device and the power grid to charge the energy storage device within the second power generation period with the sum of the photovoltaic output power and the power grid output power not greater than the allowable charging power of the energy storage;

[0015] When the difference between the photovoltaic output power and the load power is greater than or equal to the allowable charging power of the energy storage, control the photovoltaic power generation device to charge the energy storage device with the allowable charging power of the energy storage, and the power grid output power is 0 kW.

[0016] Preferably, S4: Preset a maximum demand limit value according to the user's electricity consumption last month, set a demand control margin value and a power reduction margin value, and adjust the allowable charging power of the energy storage according to the maximum demand limit value, the demand control margin value, and the power reduction margin value includes:

[0017] S41: Preset the initial maximum demand limit value according to the user's situation last month;

[0018] S42: When the sum of the load power and the energy storage allowable charging power is greater than the difference obtained by subtracting the demand control margin value from the maximum demand limit value, reduce the energy storage allowable charging power until the sum of the load power and the energy storage allowable charging power is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value;

[0019] S43: When the load power is greater than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value, adjust the energy storage allowable charging power to 0 kW;

[0020] S44: When the load power is less than the difference obtained by successively subtracting the demand control margin value and the power reduction margin value from the maximum demand limit value, adjust the energy storage allowable charging power so that the sum of the load power and the energy storage allowable charging power is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value.

[0021] Preferably, S5: After the energy storage device is fully charged, control at least one of the photovoltaic power generation device, the energy storage device, and the power grid to output electric energy to the load, and set an anti-reverse load-carrying control mode. The anti-reverse load-carrying control mode includes setting an anti-counterflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid to carry the load, and obtain the power grid output power on the main electric meter. Comparing the power grid output power with the anti-counterflow power threshold includes:

[0022] Obtain the output power of each phase of the three-phase power of the power grid on the main electric meter connected to the main transformer, and compare the anti-counterflow power threshold with the output power of each phase one by one. When the output power of any one phase of the three-phase power of the power grid is less than the anti-counterflow power threshold, first reduce the energy storage output power, and then reduce the photovoltaic output power until the output power of each phase of the power grid exceeds the power increase threshold.

[0023] Preferably, S5: After the energy storage device is fully charged, control at least one of the photovoltaic power generation device, the energy storage device, and the power grid to output electric energy to the load, and set an anti-reverse load-carrying control mode. The anti-reverse load-carrying control mode includes setting an anti-counterflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid to carry the load, and obtain the power grid output power on the main electric meter. Comparing the power grid output power with the anti-counterflow power threshold includes:

[0024] Obtain the total output power of the power grid on the main electric meter connected to the main transformer, and compare the anti-counterflow power threshold with the total output power of the power grid. When the total output power of the power grid is less than the anti-counterflow power threshold, first reduce the energy storage output power, and then reduce the photovoltaic output power until the total output power of the power grid exceeds the power increase threshold.

[0025] An anti-counterflow and anti-overload device for a photovoltaic and energy storage power station, which is used for any of the above anti-counterflow and anti-overload methods of a photovoltaic and energy storage power station, and includes:

[0026] A first prediction module, which is used to obtain meteorological data and local electricity price plans for each period, and obtain a first power generation period, a second power generation period, and photovoltaic output power according to the meteorological data and the local electricity price plans for each period;

[0027] A second prediction module, which is used to obtain user historical data and predict the load power and the allowable charging power of the energy storage according to the user historical data;

[0028] A central processing module, which is connected to the first prediction module and the second prediction module;

[0029] A first control module, which is connected to the central processing module, and is used to control the power grid to charge the energy storage device within the first power generation period at the allowable charging power of the energy storage, and in the order of preferentially generating power by the photovoltaic power generation device, control the photovoltaic power generation device and the power grid to charge the energy storage device within the second power generation period so that the sum of the photovoltaic output power and the power grid output power does not exceed the allowable charging power of the energy storage;

[0030] A second control module, which presets a maximum demand limit according to the user's electricity consumption situation last month, and sets a demand control margin value and a power reduction margin value, and adjusts the allowable charging power of the energy storage according to the maximum demand limit, the demand control margin value, and the power reduction margin value;

[0031] A third control module, after the energy storage device is fully charged, controls at least one of the photovoltaic power generation device, the energy storage device, and the power grid to output electric energy to the load, and sets an anti-counterflow load control mode, and the anti-counterflow load control mode includes setting an anti-counterflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid to carry the load, and obtain the power grid output power on the main electric meter, and compare the power grid output power with the anti-counterflow power threshold. When the power grid output power is less than the anti-counterflow power threshold, first reduce the energy storage output power, and then reduce the photovoltaic output power until the power grid output power exceeds the power increase threshold.

[0032] A photovoltaic energy storage power station anti-counterflow and anti-overload system includes the above-mentioned photovoltaic energy storage power station anti-counterflow and anti-overload device, and also includes a photovoltaic power generation device, a power grid, a load, an energy storage device, a busbar, a main transformer, a sub-transformer, a main electricity meter and a sub-electricity meter.

[0033] In summary, the present application includes at least one of the following beneficial technical effects:

[0034] Through prediction, the present application obtains the first power generation period, the second power generation period and the photovoltaic output power, and based on the first power generation period, the second power generation period and the photovoltaic output power, makes full use of the electric energy of the photovoltaic power generation device, charges the energy storage device while loading with a lower power purchase cost, and ensures that the energy storage device is fully charged, which is beneficial to the subsequent power generation and loading of the energy storage device. By monitoring the power output of the power grid, comparing with the anti-counterflow power threshold, and adjusting the output power of the energy storage device and the photovoltaic power generation device in real time, it is ensured that there is no counterflow to the power grid. By setting the maximum demand limit value, the demand control margin value and the power reduction margin value, the charging power of the energy storage is adjusted in real time to ensure that in the case of anti-counterflow, the photovoltaic power generation device and the power grid are not prone to overload during the process of charging the energy storage device, effectively ensuring anti-counterflow and anti-overload of the photovoltaic energy storage power station while making full use of the electric energy of the photovoltaic power generation device, reducing the operation cost of the power station, and ensuring the stable and compliant cycle of the power station's self-use of electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the photovoltaic energy storage power station anti-counterflow and anti-overload system in a preferred embodiment of the present application.

[0036] Figure 2 It is a flowchart of the photovoltaic energy storage power station anti-counterflow and anti-overload method in a preferred embodiment of the present application.

[0037] Figure 3 It is a flowchart of the specific implementation method of step S5 in a preferred embodiment of the present application.

[0038] Figure 4 It is a schematic diagram of the overall structure of the photovoltaic energy storage power station anti-counterflow and anti-overload device in a preferred embodiment of the present application.

[0039] Description of the reference numerals: 10, photovoltaic power generation device; 101, photovoltaic array; 102, photovoltaic inverter; 20, power grid; 30, load; 40, energy storage device; 50, busbar; 60, main transformer; 70, sub-transformer; 80, main electricity meter; 90, sub-electricity meter; 110, first prediction module; 120, second prediction module; 130, central processing module; 140, first control module; 150, second control module; 160, third control module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following further describes the present application in detail with reference to the accompanying drawings.

[0041] The present application provides a method, device and system for preventing reverse current and overload in a photovoltaic and energy storage power station. To facilitate the understanding of the method for preventing reverse current and overload in the photovoltaic and energy storage power station provided by the embodiments of the present invention, the photovoltaic and energy storage power station anti-reverse current and overload prevention system applied thereto will be described first.

[0042] Embodiment 1

[0043] A photovoltaic and energy storage power station anti-reverse current and overload prevention system, referring to Figure 1 , the system includes a photovoltaic power generation device 10, a power grid 20, a load 30, an energy storage device 40, a bus 50, a main transformer 60, a sub-transformer 70, a main electric meter 80, a sub-electric meter 90 and a photovoltaic and energy storage power station anti-reverse current and overload prevention device. The photovoltaic and energy storage power station anti-reverse current and overload prevention device is used to execute the method for preventing reverse current and overload in the photovoltaic and energy storage power station provided by any embodiment of the present application. The method for preventing reverse current and overload in the photovoltaic and energy storage power station will be explained in subsequent embodiments.

[0044] The power grid 20 is connected to the bus 50 through the main transformer 60. There are N sub-transformers 70. The N sub-transformers 70 are connected in parallel along the length direction of the bus 50 and are connected to the bus 50. The N sub-transformers 70 are located on the low-voltage side of the main transformer 60. The photovoltaic power generation device 10 includes a photovoltaic array 101 and a photovoltaic inverter 102. The output end of the photovoltaic inverter 102 is connected to the first sub-transformer 70. The energy storage device 40 is connected to the Nth sub-transformer 70. The number of loads 30 is the same as the number of sub-transformers 70, both being N. The N loads 30 are connected to the N sub-transformers 70 in one-to-one correspondence.

[0045] Specifically, the first sub-transformer 70 is located at the head end of the busbar 50. The first load 30 is connected to the first sub-transformer 70 and is combined with the photovoltaic inverter 102 at the first parallel connection point and then flows into the first sub-transformer 70. N sub-transformers 70 are arranged from the head end to the tail end of the busbar. The Nth sub-transformer 70 is close to the tail end of the busbar 50. The Nth load 30 is connected to the Nth sub-transformer 70 and is combined with the energy storage device 40 at the second parallel connection point and then flows into the Nth sub-transformer 70. The main electricity meter 80 is connected between the main transformer 60 and the busbar 50. The number of sub-electricity meters 90 is N + 2. Among them, the first sub-electricity meter 90 is connected between the first parallel connection point and the first sub-transformer 70. The second sub-electricity meter 90 is connected between the first sub-electricity meter 90 and the photovoltaic inverter 102. The third sub-electricity meter 90 to the Nth sub-electricity meter 90 are respectively connected to the second sub-transformer 70 to the (N - 1)th sub-transformer 70 in one-to-one correspondence. The (N + 1)th sub-electricity meter 90 is connected between the Nth sub-transformer 70 and the second parallel connection point. The (N + 2)th sub-electricity meter 90 is connected between the Nth sub-electricity meter 90 and the energy storage device 40. The first sub-electricity meter 90 is used to detect the power of the electric energy of the photovoltaic power generation device 10 flowing to the busbar 50 after outputting to the load 30 connected to the same sub-electricity meter 90. The second sub-electricity meter 90 is used to detect the photovoltaic output power of the photovoltaic power generation device 10. The third sub-electricity meter 90 to the Nth sub-electricity meter 90 are respectively used to detect the power of the corresponding load 30 when the load 30 connected to the same sub-electricity meter 90 is driven. In the case of charging the energy storage device 40, the (N + 1)th sub-electricity meter 90 is used to detect the total power flowing to the load 30 and the energy storage device 40 connected to the same sub-electricity meter 90. The (N + 2)th sub-electricity meter 90 is used to detect the energy storage charging power. In the case of discharging the energy storage device 40, if the output power of the energy storage device is sufficient to drive the load 30 connected to the same sub-electricity meter 90, the (N + 1)th sub-electricity meter 90 is used to detect the power of the electric energy of the energy storage device 40 flowing to the busbar 50 after driving the load 30 connected to the same sub-electricity meter 90. If the output power of the energy storage device is not sufficient to drive the load 30 connected to the same sub-electricity meter 90, the (N + 1)th sub-electricity meter 90 is used to detect the lacking power for driving the load 30. The (N + 2)th sub-electricity meter 90 is used to detect the output power of the energy storage device 40 in this state.

[0046] The anti-counterflow and anti-overload device of the photovoltaic and energy storage power station is connected to the photovoltaic inverter 102 and is used to control the photovoltaic output power to prevent the occurrence of counterflow. It is also connected to the energy storage device 40 and is used to control the allowable charging power of the energy storage device 40 through the EMS of the energy storage device 40 to prevent the occurrence of overload.

[0047] Embodiment 2

[0048] A method for preventing reverse power flow and overload in a photovoltaic energy storage power station. The following embodiments will specifically describe the method for preventing reverse power flow and overload performed by the device for preventing reverse power flow and overload in the photovoltaic energy storage power station.

[0049] As Figure 1 and 2 shown, the method for preventing reverse power flow and overload includes:

[0050] S1. Obtain meteorological data, local electricity price plans for each time period, and a preset intensity. According to the meteorological data and local electricity price plans for each time period, obtain the first power generation time period, the second power generation time period, and the photovoltaic output power.

[0051] Specifically, the meteorological data is the light intensity data in the direction of the photovoltaic array 101 within the next 24 hours. The local electricity price plans for each time period are the distribution plans of peak electricity time periods and valley electricity time periods within the next 24 hours. The valley electricity time period refers to the time period when the electricity price of the power grid 20 is the lowest compared to other time periods, and the peak electricity time period refers to the time period when the electricity price is higher than that of the valley electricity time period. Since the electricity price plans for each time period in each region are different, the electricity price plans for each time period mentioned in this application are the plans stipulated by the region where the application site of the method, device, and system for preventing reverse power flow and overload in a photovoltaic energy storage power station provided by this application is located.

[0052] The first power generation time period is the time period in the valley electricity time period when the light intensity is less than the preset intensity, the second power generation time period is the time period in the valley electricity time period when the light intensity is greater than the preset intensity, and the photovoltaic output power is the average power generation power of the photovoltaic power generation device 10 per hour in the second power generation time period. Specifically, the preset intensity is the preset light intensity and is greater than 0 Lux. Since the light intensity at night is not necessarily equal to 0 Lux, but is very low compared to the light intensity after sunrise and can be ignored, the preset intensity is set to indicate that the output power of the photovoltaic power generation device 10 can be ignored during the time period when the light intensity is lower than the preset intensity.

[0053] S2. Obtain user historical data, and predict the load power and the energy storage allowable charging power for the next 24 hours according to the user historical data.

[0054] Specifically, the user historical data includes the energy storage installed capacity and the historical load power data of N loads 30 within the past 24 hours. By calculating the energy storage allowable charging power required to fully charge the energy storage installed capacity during the first power generation time period and the second power generation time period, the load power for the next 24 hours refers to the load power in the past 24 hours.

[0055] S3. Control the power grid 20 to charge the energy storage device 40 with the energy storage allowable charging power during the first power generation time period, and in the order of giving priority to the power generation of the photovoltaic power generation device 10, control the photovoltaic power generation device 10 and the power grid 20 to charge the energy storage device 40 with the sum of the photovoltaic output power and the power grid output power not greater than the energy storage allowable charging power during the second power generation time period.

[0056] Specifically, during the first power generation period, the power generation power of the photovoltaic power generation device 10 is less than the preset power. Therefore, the load 30 is driven by the power grid 20. While driving the load, the power grid 20 charges the energy storage device 40 at a power equal to the allowable charging power of the energy storage. At the moment when the first power generation period ends, the power grid 20 stops charging the energy storage device 40, and the energy storage device 40 is in a standby state without charging or discharging. And in the second power generation period, the order is switched to give priority to the photovoltaic power generation device 10 for power generation. There is a period reserved between the first power generation period and the second power generation period for the energy storage device 40 to switch from the charging state to the standby state and from the standby state to the power generation state. The priority of the photovoltaic power generation device 10 for power generation means that the photovoltaic power generation device 10 is given priority to drive the load and the surplus electric energy after driving the load is transmitted to the energy storage device 40. When the photovoltaic output power of the photovoltaic power generation device 10 is not sufficient to charge the energy storage device 40 at the allowable charging power of the energy storage, that is, when the difference between the photovoltaic output power and the load power is greater than 0 kW and less than the allowable charging power of the energy storage, power is purchased from the power grid 20 to make up for the missing power. It is controlled that the sum of the photovoltaic output power and the power grid output power in the second power generation period does not exceed the allowable charging power of the energy storage to charge the energy storage device 40. When the difference between the photovoltaic output power and the load power is greater than or equal to the allowable charging power of the energy storage, it is controlled that the photovoltaic power generation device 10 charges the energy storage device 40 at the allowable charging power of the energy storage, and the power grid output power is 0 kW. In this way, the electric energy of the photovoltaic power generation device 10 can be fully utilized, and the energy storage device 40 can be fully charged at a lower power purchase cost compared with the prior art.

[0057] S4. Preset the maximum demand limit value according to the user's electricity consumption situation last month, set the demand control margin value and the power reduction margin value, and adjust the allowable charging power of the energy storage device 40 according to the maximum demand limit value, the demand control margin value and the power reduction margin value.

[0058] As Figure 3 shown, specifically, it includes:

[0059] S41. Preset the initial maximum demand limit value according to the user's situation last month.

[0060] Among them, the maximum demand limit value is the sum of the demands in the charging state of the load 30 and the energy storage device 40. Since the load 30 changes with time according to the demands of the plant area to which the method of the present application is applied, the maximum demand limit value is a dynamic value calculated by the sliding difference maximum demand calculation method, which is calculated every 15 minutes. The value calculated each time is compared with the previous value, and the larger value is taken as the maximum demand limit value.

[0061] S42. When the sum of the load power and the allowable charging power of the energy storage is greater than the difference obtained by subtracting the demand control margin value from the maximum demand limit, reduce the allowable charging power of the energy storage until the sum of the load power and the allowable charging power of the energy storage is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit.

[0062] S43. When the load power is greater than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit, adjust the allowable charging power of the energy storage to 0 kW and be in the standby state.

[0063] S44. When the load power is less than the difference obtained by successively subtracting the demand control margin value and the power reduction margin value from the maximum demand limit, adjust the allowable charging power of the energy storage so that the sum of the load power and the allowable charging power of the energy storage is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit.

[0064] In this way, set the demand control margin value to leave a margin for fluctuations in the load power and the allowable charging power of the energy storage, provide sufficient response time for demand control, and set the power reduction margin value to prevent frequent activation of demand control when the total power fluctuates around the demand control critical point.

[0065] S5. After the energy storage device is fully charged, set the anti-backflow load control mode, and control at least one of the photovoltaic power generation device 10, the energy storage device 40, and the power grid 20 to output electric energy to drive the load 30. Set the anti-backflow power threshold and the power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid to drive the load, and obtain the power grid output power on the main electricity meter 80, and compare the power grid output power with the anti-backflow power threshold. When the power grid output power is less than the anti-backflow power threshold, preferentially reduce the energy storage output power, and then reduce the photovoltaic output power until the power grid output power exceeds the power increase threshold.

[0066] Specifically, the anti-backflow power threshold is the preset grid output power, which is used to prevent the electric energy of the photovoltaic power generation device 10 and the energy storage device 40 from flowing back to the grid 20, that is, to ensure that the grid 20 always outputs a power greater than the anti-backflow power threshold. Since the photovoltaic output power, the energy storage output power, and the load power will vary, when the sum of the photovoltaic output power, the energy storage output power, and the anti-backflow power threshold is greater than or equal to the load power, the grid output power collected by the main electricity meter 80 is equal to or smaller than the anti-backflow power threshold, indicating that the output powers of the photovoltaic power generation device 10 and the energy storage device 40 are too large and are about to flow back to the grid 20. At this time, the energy storage output power is preferentially reduced, and then the photovoltaic output power is reduced. Since the energy storage device 40 needs to be charged after discharging, the energy storage output power is preferentially reduced to save the electric energy of the energy storage device 40. If the energy storage output power is 0 and the grid output power is still smaller than the anti-backflow power threshold, then the photovoltaic output power is further reduced until the grid output power exceeds the power increase threshold. The power increase threshold is a preset value, and the power increase threshold is greater than the anti-backflow power threshold. It is the power tolerance set to prevent frequent activation of the anti-backflow control when the grid output power fluctuates around the anti-backflow power threshold. For example, the anti-backflow power control threshold is set to 20 kW, and the power increase threshold is set to 25 kW. When the grid output power is less than 20 kW, the anti-backflow mechanism is triggered to reduce the photovoltaic output power and / or the energy storage output power until the grid output power is greater than 20 kW. The load power and the photovoltaic output power will fluctuate due to user usage and light intensity changes. If the load power increases by 3 kW, making the grid output power 23 kW, since the grid output power is between the anti-backflow power threshold and the power increase threshold at this time, the photovoltaic output power and the energy storage output power are not adjusted. If the load power increases to more than 5 kW, making the grid output power greater than the power increase threshold, then the photovoltaic output power and / or the energy storage output power are increased to keep the grid output power within the range greater than the anti-backflow power threshold. The setting of the power increase threshold gives a tolerance when the grid output power fluctuates around the anti-backflow power threshold. When the grid output power increases, it reduces the frequency of adjustment of the photovoltaic output power and the energy storage output power, thereby reducing the calculation energy consumption.

[0067] The reverse power flow prevention and load control mode is a single-phase power reverse power flow prevention control mode or a total power reverse power flow prevention control mode. The selection of the m mode depends on the user's needs. Among them, in the single-phase power reverse power flow prevention control mode, the grid output power refers to the output power of each phase of the three-phase power of the grid 20. In this mode, the reverse power flow prevention power threshold is compared with the output power of each phase one by one. The reverse power flow prevention power threshold is the preset minimum output power of each phase of the grid 20, and the power increase threshold is the preset output power of each phase of the grid 20. When the output power of each phase of the three-phase power of the grid 20 is less than the reverse power flow prevention power threshold, the energy storage output power is preferentially reduced, and then the photovoltaic output power is reduced until the output power of each phase of the three-phase power of the grid 20 exceeds the power increase threshold; in the total power reverse power flow prevention control mode, the grid output power refers to the total output power of the three-phase grid 20. In this mode, the reverse power flow prevention power threshold is compared with the grid output total power. The reverse power flow prevention power threshold is the minimum value of the sum of the preset output powers, and the power increase threshold is the total preset value. When the grid 20 output total power is less than the reverse power flow prevention power threshold, the energy storage output power is preferentially reduced, and then the photovoltaic output power is reduced until the grid output total power exceeds the power increase threshold.

[0068] Embodiment 3

[0069] The present application also provides a reverse power flow and overload prevention device for a photovoltaic and energy storage power station, which is used to execute the above-mentioned reverse power flow and overload prevention method for a photovoltaic and energy storage power station, and includes:

[0070] The first prediction module 110 is connected to a meteorological data platform and is connected to the central processing module 130, and is used to obtain meteorological data and local electricity price plans for each period, and obtain the first power generation period, the second power generation period and the photovoltaic output power according to the meteorological data and the local electricity price plans for each period.

[0071] The second prediction module 120 is connected to the (N + 2)th sub-meter 90 and is connected to the central processing module 130, and is used to obtain user historical data and predict the load power and the energy storage allowable charging power according to the user historical data.

[0072] The central processing module 130 is configured to receive and process data from the first prediction module 110 and the second prediction module 120, and is connected to a first control module 140, a second control module 150, and a third control module 160. The first control module 140 is connected to the power grid 20, the photovoltaic power generation device 10, and the energy storage device 40, and is configured to control the power grid 20 to charge the energy storage device 40 at the energy storage allowed charging power during the first power generation period. In the order of giving priority to the power generation of the photovoltaic power generation device 10, the first control module 140 controls the photovoltaic power generation device 10 and the power grid 20 to charge the energy storage device 40 at a sum of the photovoltaic output power and the power grid output power not greater than the energy storage allowed charging power during the second power generation period. The second control module 150 is connected to the energy storage device 40 and the main electricity meter 80, presets a maximum demand limit value according to the user's electricity consumption situation of the previous month, sets a demand control margin value and a power reduction margin value, and adjusts the energy storage allowed charging power of the energy storage device 40 according to the maximum demand limit value, the demand control margin value, and the power reduction margin value. The third control module 160 is connected to the main electricity meter 80, the power grid 20, the photovoltaic inverter 102, and the energy storage device 40, and is configured to obtain the power grid output power of the main electricity meter 80, and control at least one of the photovoltaic power generation device 10, the energy storage device 40, and the power grid 20 to output electric energy to the load 30. A reverse current prevention load-carrying control mode is set, and the reverse current prevention load-carrying control mode includes setting a reverse current prevention power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, power is purchased from the power grid 20 for load-carrying, and the power grid output power on the main electricity meter 80 is obtained. The power grid output power is compared with the reverse current prevention power threshold. When the power grid output power is less than the reverse current prevention power threshold, the energy storage output power is preferentially reduced, and then the photovoltaic output power is reduced until the power grid output power exceeds the power increase threshold.

[0073] In this application, the first power generation period, the second power generation period, and the photovoltaic output power are obtained through prediction. Based on the first power generation period, the second power generation period, and the photovoltaic output power, the electric energy of the photovoltaic power generation device 10 is fully utilized to charge the energy storage device 40 while carrying the load at a relatively low power purchase cost, and it is ensured that the energy storage device 40 is fully charged, which is beneficial for the subsequent power generation and load-carrying of the energy storage device 40. By comparing the power grid output power with the reverse current prevention power threshold, the output powers of the energy storage device 40 and the photovoltaic power generation device 10 are adjusted in real time to ensure that there is no reverse current to the power grid 20. By setting the maximum demand limit value, the demand control margin value, and the power reduction margin value, the energy storage allowed charging power is adjusted in real time to ensure that during the process of charging the energy storage device 40 by the photovoltaic power generation device 10 and the power grid 20, it is not easy to have an overload phenomenon under the condition of preventing reverse current, effectively ensuring that the photovoltaic energy storage power station prevents reverse current and overload while fully utilizing the electric energy of the photovoltaic power generation device 10, reducing the operation cost of the power station, and ensuring the stability of the power station's self-use of generated electricity.

[0074] The above are all preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.

Claims

1. A method for preventing reverse power flow and overload in a photovoltaic and energy storage power station, characterized in that, Including: S1: Obtain meteorological data, local electricity price plans for each period, and a preset intensity. Obtain a first power generation period, a second power generation period, and the photovoltaic output power according to the meteorological data and the local electricity price plans for each period; S2: Obtain user historical data, and predict the load power and the energy storage allowable charging power for the next 24 hours according to the user historical data; S3: Control the power grid (20) to charge the energy storage device (40) at the energy storage allowable charging power during the first power generation period, and in the order of giving priority to the photovoltaic power generation device (10) for power generation, control the photovoltaic power generation device (10) and the power grid (20) to charge the energy storage device (40) during the second power generation period with the sum of the photovoltaic output power and the power grid output power not exceeding the energy storage allowable charging power; S4: Preset a maximum demand limit value according to the user's electricity consumption situation last month, and set a demand control margin value and a power reduction margin value, and adjust the energy storage allowable charging power according to the maximum demand limit value, the demand control margin value, and the power reduction margin value; S5: After the energy storage device (40) is fully charged, control at least one of the photovoltaic power generation device (10), the energy storage device (40), and the power grid (20) to output electric energy to the load (30), and set an anti-reverse load control mode. The anti-reverse load control mode includes setting an anti-backflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid (20) to carry the load, and obtain the power grid output power on the main electricity meter (80). Compare the power grid output power with the anti-backflow power threshold. When the power grid output power is less than the anti-backflow power threshold, preferentially reduce the energy storage output power, and then reduce the photovoltaic output power until the power grid output power exceeds the power increase threshold.

2. A method for preventing backflow and overload in a photovoltaic and energy storage power station according to claim 1, characterized in that The meteorological data is the light intensity data within the next 24 hours; The local electricity price plans for each period are the distribution plans of peak electricity periods and valley electricity periods within the next 24 hours; The first power generation period is the period when the light intensity is less than the preset intensity during the valley electricity period; The second power generation period is the period when the light intensity is greater than the preset intensity during the valley electricity period; The photovoltaic output power is the average power generation of the photovoltaic power generation device (10) per hour during the second power generation period.

3. A method for preventing reverse power flow and overload in a photovoltaic and energy storage power station according to claim 1, characterized in that, In the order of giving priority to the photovoltaic power generation device (10) for power generation, controlling the photovoltaic power generation device (10) and the power grid (20) to charge the energy storage device (40) during the second power generation period with the sum of the photovoltaic output power and the power grid output power not exceeding the energy storage allowable charging power includes: When the difference between the photovoltaic output power and the load power is greater than 0 kW and less than the energy storage allowable charging power, control the photovoltaic power generation device (10) and the power grid (20) to charge the energy storage device (40) during the second power generation period with the sum of the photovoltaic output power and the power grid output power not exceeding the energy storage allowable charging power; When the difference between the photovoltaic output power and the load power is greater than or equal to the allowable charging power of the energy storage, control the photovoltaic power generation device (10) to charge the energy storage device (40) with the allowable charging power of the energy storage, and the grid output power is 0 kW.

4. A method for preventing reverse power flow and overload in a photovoltaic and energy storage power station according to claim 1, characterized in that, S4: Preset a maximum demand limit value according to the user's electricity consumption last month, and set a demand control margin value and a power reduction margin value. Adjusting the allowable charging power of the energy storage according to the maximum demand limit value, the demand control margin value, and the power reduction margin value includes: S41: Preset the initial maximum demand limit value according to the user's situation last month; S42: When the sum of the load power and the allowable charging power of the energy storage is greater than the difference obtained by subtracting the demand control margin value from the maximum demand limit value, reduce the allowable charging power of the energy storage until the sum of the load power and the allowable charging power of the energy storage is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value; S43: When the load power is greater than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value, adjust the allowable charging power of the energy storage to 0 kW; S44: When the load power is less than the difference obtained by successively subtracting the demand control margin value and the power reduction margin value from the maximum demand limit value, adjust the allowable charging power of the energy storage so that the sum of the load power and the allowable charging power of the energy storage is less than or equal to the difference obtained by subtracting the demand control margin value from the maximum demand limit value.

5. A method for preventing reverse current and overload in a photovoltaic and energy storage power station according to claim 1, characterized in that, S5: After the energy storage device (40) is fully charged, control at least one of the photovoltaic power generation device (10), the energy storage device (40), and the grid (20) to output electric energy to the load (30), and set an anti-reverse load-carrying control mode. The anti-reverse load-carrying control mode includes setting an anti-backflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the grid (20) to carry the load, and obtain the grid output power on the main electricity meter (80). Comparing the grid output power and the anti-backflow power threshold includes: Obtain the output power of each phase of the three-phase electricity of the grid (20) on the main electricity meter (80) connected to the main transformer (60), and compare the anti-backflow power threshold and the output power of each phase one by one. When the output power of any one phase of the three-phase electricity of the grid (20) is less than the anti-backflow power threshold, first reduce the energy storage output power, and then reduce the photovoltaic output power until the output power of each phase of the grid (20) exceeds the power increase threshold.

6. A method for preventing reverse power flow and overload in a photovoltaic and energy storage power station according to claim 1, characterized in that, S5: After the energy storage device (40) is fully charged, control at least one of the photovoltaic power generation device (10), the energy storage device (40), and the power grid (20) to output electrical energy to the load (30), and set an anti-reverse load-carrying control mode. The anti-reverse load-carrying control mode includes setting an anti-backflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, purchase power from the power grid (20) to carry the load, and obtain the power output from the power grid on the main electricity meter (80). Comparing the power output from the power grid and the anti-backflow power threshold includes: Obtain the total output power of the power grid (20) on the main electricity meter (80) connected to the main transformer (60), and compare the anti-backflow power threshold with the total output power of the power grid (20) correspondingly. When the total output power of the power grid (20) is less than the anti-backflow power threshold, first reduce the energy storage output power, and then reduce the photovoltaic output power until the total output power of the power grid (20) exceeds the power increase threshold.

7. An anti-backflow and anti-overload device for a photovoltaic energy storage power station, characterized in that, A method for preventing reverse current and overloading in a photovoltaic and energy storage power station for implementing any one of claims 1 to 6, including: A first prediction module (110) for obtaining meteorological data and local electricity price schemes for each period, and obtaining a first power generation period, a second power generation period, and the photovoltaic output power according to the meteorological data and the local electricity price schemes for each period; A second prediction module (120) for obtaining user historical data and predicting the load power and the energy storage allowable charging power according to the user historical data; A central processing module (130) connected to the first prediction module (110) and the second prediction module (120); A first control module (140) connected to the central processing module (130), for controlling the power grid (20) to charge the energy storage device (40) at the energy storage allowable charging power during the first power generation period, and in the order of giving priority to the photovoltaic power generation device (10) to generate electricity, controlling the photovoltaic power generation device (10) and the power grid (20) to charge the energy storage device (40) during the second power generation period with the sum of the photovoltaic output power and the power grid output power not greater than the energy storage allowable charging power; A second control module (150) presetting a maximum demand limit according to the user's electricity consumption situation last month, and setting a demand control margin value and a power reduction margin value, and adjusting the energy storage allowable charging power according to the maximum demand limit, the demand control margin value, and the power reduction margin value; The third control module (160) controls at least one of the photovoltaic power generation device (10), the energy storage device (40), and the power grid (20) to output electric energy to the load (30) after the energy storage device (40) is fully charged, and sets an anti-reverse load-carrying control mode. The anti-reverse load-carrying control mode includes setting an anti-backflow power threshold and a power increase threshold. When the photovoltaic output power and the energy storage output power are less than the load power, power is purchased from the power grid (20) for load-carrying, and the power grid output power on the main electricity meter (80) is obtained. The power grid output power is compared with the anti-backflow power threshold. When the power grid output power is less than the anti-backflow power threshold, the energy storage output power is preferentially reduced, and then the photovoltaic output power is reduced until the power grid output power exceeds the power increase threshold.

8. A photovoltaic and energy storage power station anti-backflow and anti-overload system, characterized in that, The anti-backflow and anti-overload device for a photovoltaic and energy storage power station according to claim 7 further includes a photovoltaic power generation device (10), a power grid (20), a load (30), an energy storage device (40), a busbar (50), a main transformer (60), a sub-transformer (70), a main electricity meter (80), and a sub-electricity meter (90).

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