A control method for energy storage peak shaving and valley filling

Abstract

The present invention relates to a control method for energy storage peak shaving and valley filling, which comprises the following steps: Step 1: determine whether the current time is within the peak time period, if so, execute Step 2, if not, execute Step 3; Step 2: determine the working state of the energy storage converter and whether the energy storage device charge and discharge constraints are met, determine whether there is reverse flow between the energy storage system and the power grid, and increase or decrease the discharge power of the energy storage inverter according to the judgment result; Step 3: determine the working state of the energy storage converter and whether the energy storage device charge and discharge constraints and the energy storage converter working constraints are met, and increase or decrease the charging power of the energy storage inverter according to the judgment result. The present invention can automatically operate and adjust the charge and discharge power of the energy storage system in real time, thereby controlling the energy storage system to achieve peak shaving and valley filling, and avoiding reverse flow and transformer overload problems.

Description

Technical Field

[0001] The present invention belongs to the technical field of microgrid control, and in particular relates to a control method suitable for realizing peak shaving and valley filling in an energy storage system connected to a power grid. Background Art

[0002] As an important support for "Internet +" smart energy and a technical means of friendly interaction with large power grids, microgrids can improve the safety and reliability of power systems, promote the access and local consumption of clean energy, improve energy utilization efficiency, play an important role in energy conservation and emission reduction, and are conducive to building a conservation-oriented society.

[0003] At present, deep-seated contradictions such as low overall efficiency of the power system, insufficient coordination between sources, networks and loads, and insufficient complementarity and mutual assistance among various power sources are becoming increasingly prominent, and they are in urgent need of overall optimization. We need to rely on new technologies such as modern information and communication technology, big data, artificial intelligence, and energy storage to fully mobilize the load-side regulation and response capabilities, study the comprehensive optimization configuration plan of sources, networks, loads, and storage, promote the integrated development with multi-energy complementary demonstration parks and smart integrated energy services, and, under economically feasible conditions, improve self-balancing capabilities and reduce the demand for peak regulation and capacity reserve on large power grids.

[0004] Peak shaving and valley filling is currently the main operating mode and profit path for energy storage devices in microgrids. Peak shaving and valley filling refers to the energy storage device charging during the low electricity consumption period (when the electricity price is low) and discharging to users during the peak electricity consumption period (when the electricity price is high). While alleviating the power supply pressure of the power grid during the peak period and improving the utilization rate of the power grid during the valley period, it also realizes the arbitrage of peak and valley electricity prices. The peak-valley price difference in the major electricity-consuming provinces in the country is distributed between 0.4 and 0.9 yuan / kWh, which provides considerable space for users to use energy storage to arbitrage the peak-valley price difference.

[0005] However, the energy storage device in the microgrid may encounter the following problems during the peak load shifting operation:

[0006] (1) When the energy storage device is shaving peak power (discharging), if the total power consumption of the user is less than the discharge power of the energy storage device, the power of the energy storage device will flow back to the upper-level power grid connected to the user, resulting in a decrease in the peak shaving income of the energy storage device;

[0007] (2) When the energy storage device is valley filling (charging), if the charging power of the energy storage device is too high, resulting in the user's total power consumption being too high, it may cause the user's transformer to overload or even trip, affecting the transformer's efficiency, life, and the user's power safety.

[0008] Therefore, during the peak-shaving and valley-filling operation of the energy storage device, the charging and discharging power of the energy storage device needs to be adjusted according to the user's power consumption to avoid the reverse grid connection (reverse flow) of the energy storage device's power or the overload operation (overload) of the user's transformer.

[0009] The mainstream energy storage devices on the market currently generally achieve peak-shaving and valley-filling operation by pre-setting the charging and discharging power of the energy storage device in each period (such as setting the energy storage device to discharge from 8:00 to 12:00 with a discharge power of 200kW, and setting the energy storage device to charge from 0:00 to 8:00 with a charging power of 100kW). The energy storage peak-shaving and valley-filling solution to prevent reverse flow and transformer overload is not designed in the microgrid. In this mode, the energy storage device will not adjust the charging and discharging power in real time according to the user's power consumption, so it is easy for the energy storage device's power to go back to the grid (reverse flow) or the user's transformer to be overloaded (overloaded). Summary of the invention

[0010] The purpose of the present invention is to provide an energy storage peak shaving and valley filling control method that can adjust the charging and discharging power of an energy storage system in real time to avoid reverse flow and transformer overload problems.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A method for controlling energy storage peak shaving and valley filling is used to control an energy storage system connected to a power grid to achieve peak shaving and valley filling. The energy storage system includes an energy storage device, and the energy storage device includes an energy storage battery and an energy storage converter connected to the energy storage battery. The method for controlling energy storage peak shaving and valley filling includes the following steps:

[0013] Step 1: Determine whether the current time is within the peak time period, if yes, go to step 2, if no, go to step 3;

[0014] Step 2: Determine the working state of the energy storage converter and whether the energy storage device charge and discharge constraint conditions are met, and determine whether there is reverse flow between the energy storage system and the power grid. If the energy storage converter is in the off state or the on state and the discharge mode, meets the energy storage device charge and discharge constraint conditions, and does not have reverse flow, then increase the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the off state and does not meet the energy storage device charge and discharge constraint conditions or reverse flow, then return to step 1. If the energy storage converter is in the on state and the discharge mode and does not meet the energy storage device charge and discharge constraint conditions or reverse flow, then reduce the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the on state and the charging mode, switch the energy storage converter to the off state and return to step 1.

[0015] Step 3: Determine the working state of the energy storage converter and whether the charge and discharge constraints of the energy storage device and the working constraints of the energy storage converter are met. If the energy storage converter is in the power-on state and charging mode or the power-off state and meets the charge and discharge constraints of the energy storage device and the working constraints of the energy storage converter, increase the charging power of the energy storage converter and return to step 1. If the energy storage converter is in the power-on state and charging mode and does not meet the charge and discharge constraints of the energy storage device or the working constraints of the energy storage converter, reduce the charging power of the energy storage converter and return to step 1. If the energy storage converter is in the power-on state and discharging mode, switch the energy storage converter to the power-off state and return to step 1.

[0016] In step 1, if the peak hour start time ≤ the current time < the peak hour end time, it is determined that the current time is within the peak hour period.

[0017] A mains power anti-backflow threshold is preset, and in step 2, the detected mains power and the mains power anti-backflow threshold are used to determine whether there is a backflow between the energy storage system and the power grid. When the detected mains power is greater than the mains power anti-backflow threshold, it is determined that there is no backflow.

[0018] The charging and discharging constraints of the energy storage device include: the state of charge of the energy storage battery > the discharge depth of the energy storage battery; the state of charge of the energy storage battery < the charging depth of the energy storage battery; the discharge power of the energy storage inverter < the maximum discharge power of the energy storage battery; the charging power of the energy storage inverter < the maximum charging power of the energy storage battery; the working constraints of the energy storage inverter are: the discharge power of the energy storage inverter < the maximum discharge power of the energy storage battery, and the charging power of the energy storage inverter < the maximum charging power of the energy storage battery.

[0019] In step 2, the method for increasing the discharge power of the energy storage converter is: switching the energy storage converter in the shutdown state to the power-on state and the discharge mode, and determining the discharge power of the energy storage converter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, or determining the discharge power increase amount based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the increased discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power increase amount;

[0020] The method for reducing the discharge power of the energy storage inverter is: determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the discharge power of the energy storage inverter after the reduction based on the current discharge power of the energy storage inverter and the discharge power reduction amount, or switching the energy storage inverter in the power-on state and discharge mode to the power-off state.

[0021] The step 2 comprises the following steps:

[0022] Step 2-1: Determine whether the energy storage converter is in a shutdown state, if yes, execute step 2-2, if no, execute step 2-5;

[0023] Step 2-2: Determine whether the state of charge of the energy storage battery > the depth of discharge of the energy storage battery is established, if so, execute step 2-3, if not, return to step 1;

[0024] Step 2-3: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 2-4. If so, return to step 1.

[0025] Step 2-4: increasing the discharge power of the energy storage converter, switching the energy storage converter from the shutdown state to the startup state and the discharge mode, and determining the discharge power of the energy storage converter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and then returning to step 1;

[0026] Step 2-5: Determine whether the energy storage converter is in the power-on state and the discharge mode, if yes, execute step 2-6, if no, execute step 2-12;

[0027] Step 2-6: Determine whether the state of charge of the energy storage battery> the depth of discharge of the energy storage battery is established, if so, execute step 2-7, if not, execute step 2-11;

[0028] Step 2-7: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 2-8. If so, execute step 2-10.

[0029] Step 2-8: Determine whether the discharge power of the energy storage converter is less than the maximum discharge power of the energy storage battery. If so, execute step 2-9; otherwise, return to step 1;

[0030] Step 2-9: increasing the discharge power of the energy storage converter, determining the discharge power increase amount based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the increased discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power increase amount, and then returning to step 1;

[0031] Step 2-10: reducing the discharge power of the energy storage converter, determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the reduced discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power reduction amount, and then returning to step 1;

[0032] Step 2-11: reducing the discharge power of the energy storage converter, switching the energy storage converter in the on state and the discharge mode to the off state, and then returning to step 1;

[0033] Step 2-12: Switch the energy storage converter to the shutdown state and then return to step 1.

[0034] The discharge power reduction amount is the product of the maximum discharge power of the energy storage battery and the battery discharge power growth coefficient, and the discharge power increase amount is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient.

[0035] In step 3, the method for increasing the charging power of the energy storage converter is as follows: determining the charging power increase amount based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the charging power of the energy storage converter after the current charging power of the energy storage converter and the charging power increase amount, or switching the energy storage converter in the shutdown state to the power-on state and the charging mode, and determining the charging power of the energy storage converter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery;

[0036] The method for reducing the charging power of the energy storage inverter is: determining the charging power reduction amount based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, and reducing the charging power of the energy storage inverter based on the current charging power of the energy storage inverter and the charging power increase, or switching the energy storage inverter in the power-on state and charging mode to the power-off state.

[0037] The step 3 comprises the following steps:

[0038] Step 3-1: Determine whether the energy storage converter is in the power-on state and the charging mode, if so, execute step 3-2, if not, execute step 3-8;

[0039] Step 3-2: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-3; otherwise, execute step 3-7;

[0040] Step 3-3: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 3-4. If so, execute step 3-6.

[0041] Step 3-4: Determine whether the charging power of the energy storage converter is less than the maximum charging power of the energy storage battery. If so, execute step 3-5; otherwise, return to step 1;

[0042] Step 3-5: increasing the charging power of the energy storage converter, determining the charging power increase amount based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the increased charging power of the energy storage converter based on the current charging power of the energy storage converter and the charging power increase amount, and then returning to step 1;

[0043] Step 3-6: reducing the charging power of the energy storage converter, determining the amount of reduction in charging power based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the reduced charging power of the energy storage converter based on the current charging power of the energy storage converter and the charging power increase, and then returning to step 1;

[0044] Step 3-7: reducing the charging power of the energy storage converter, switching the energy storage converter in the power-on state and the charging mode to the power-off state, and then returning to step 1;

[0045] Step 3-8: Determine whether the energy storage converter is in a shutdown state, if yes, execute step 3-9, if no, execute step 3-12;

[0046] Step 3-9: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-10. If not, return to step 1.

[0047] Step 3-10: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 3-11. If reverse flow, return to step 1.

[0048] Step 3-11: increasing the charging power of the energy storage converter, switching the energy storage converter from the shutdown state to the startup state and charging mode, and determining the charging power of the energy storage converter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery, and then returning to step 1;

[0049] Step 3-12: Switch the energy storage converter to the shutdown state and then return to step 1.

[0050] The charging power increase is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient, and the charging power reduction is the product of the maximum charging power of the energy storage battery and the charging power growth coefficient.

[0051] The value of the battery charging power growth coefficient and the battery discharging power growth coefficient is n%, where n is an integer divisible by 100.

[0052] The value of n is 1, 2, 4, 5, 10, 20 or 50.

[0053] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: the present invention can operate automatically and adjust the charging and discharging power of the energy storage system in real time, thereby controlling the energy storage system to achieve peak shaving and valley filling, avoiding reverse current and transformer overload problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Attached Figure 1 Schematic diagram of photovoltaic energy storage system.

[0055] Attached Figure 2 It is a flow chart of the energy storage peak shaving and valley filling control method of the present invention. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0057] Embodiment 1: The energy storage system connected to the power grid includes an energy storage device, and the energy storage device includes an energy storage battery and an energy storage converter (PCS) connected to the energy storage battery. Figure 1 The figure shows a photovoltaic energy storage system connected to the power grid. In addition to the energy storage device, it also includes a photovoltaic device, a transformer, etc. The mains power of the power grid is connected to the 400V bus through the transformer, and the photovoltaic device and the energy storage device are connected to the 400V bus. The user's electrical equipment can also be connected to the 400V bus. A smart meter can be set between the power grid and the 400V bus to detect power. The photovoltaic device includes multiple photovoltaic panels and multiple inverters connected to the photovoltaic panels one by one. Each inverter is connected to the 400V bus via a smart meter. The energy storage converter is also connected to the 400V bus via a smart meter. The energy storage converter has an on state and an off state, and it can select a charging mode or a discharging mode.

[0058] For the energy storage system, the following energy storage peak shaving and valley filling control method is proposed, which is used to control the energy storage system connected to the power grid to achieve peak shaving and valley filling.

[0059] In this method, the following parameters need to be preset:

[0060] 1. Battery charging power growth factor: The battery charging power growth factor is used to indicate the percentage of power increase when adjusting the charging power of the energy storage battery in the energy storage system;

[0061] 2. Battery discharge power growth coefficient: The battery discharge power growth coefficient is used to indicate the percentage of power increase when adjusting the discharge power of the energy storage battery in the energy storage system;

[0062] 3. Mains power reverse flow prevention threshold: The mains power reverse flow prevention threshold is used together with the detected mains power to determine whether there is reverse flow between the photovoltaic energy storage system and the power grid. When the detected mains power is greater than the mains power reverse flow prevention threshold, it is judged as no reverse flow, otherwise it is no reverse flow.

[0063] The above battery charging power growth coefficient and battery discharging power growth coefficient are set to n%, where n is an integer divisible by 100, for example, n is 1, 2, 4, 5, 10, 20 or 50. In the same solution, the battery charging power growth coefficient and the battery discharging power growth coefficient can be the same or different and can be set as needed. Usually, the mains power backflow prevention threshold is greater than the rated discharge power of the energy storage battery * the battery discharge power growth coefficient / 100.

[0064] As attached Figure 2 As shown, the energy storage peak shaving and valley filling control method, the energy storage system includes an energy storage device, the energy storage device includes an energy storage battery, and an energy storage converter connected to the energy storage battery, and the energy storage peak shaving and valley filling control method includes the following steps:

[0065] Step 1: Determine whether the current time is within the peak time period, if so, proceed to step 2, if not, proceed to step 3.

[0066] In step 1, if the peak time start time ≤ current time < peak time end time, then the current time is judged to be within the peak time period. Since the peak time period is often divided into several segments, it is necessary to make a judgment for each segment separately. In this embodiment, the peak time period is divided into two segments as an example, the first peak time period lasts from the peak time start time 1 to the peak time end time 1, and the second peak time period lasts from the peak time start time 2 to the peak time end time 2, then step 1 specifically includes the following steps:

[0067] Step 1-1: Determine whether the peak time start time 1 ≤ current time < peak time end time 1 is established. If so, the current time is within the peak time period, so execute step 2. If not, execute step 1-2;

[0068] Step 1-2: Determine whether the peak time start time 2 ≤ current time < peak time end time 2 is established. If so, the current time is within the peak time period, so execute step 2; otherwise, execute step 3.

[0069] Step 2: The current time is within the peak time period, determine the working state of the energy storage converter and whether it meets the charge and discharge constraints of the energy storage device, and determine whether there is reverse flow between the energy storage system and the power grid. If the energy storage converter is in the off state or the on state and the discharge mode, meets the charge and discharge constraints of the energy storage device, and does not have reverse flow, then increase the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the off state and does not meet the charge and discharge constraints of the energy storage device or has reverse flow, then return to step 1. If the energy storage converter is in the on state and the discharge mode and does not meet the charge and discharge constraints of the energy storage device or has reverse flow, then reduce the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the on state and the charging mode, switch the energy storage converter to the off state and return to step 1.

[0070] In step 2, the energy storage device charge and discharge constraints include: the state of charge (SOC) of the energy storage battery > the discharge depth of the energy storage battery; the state of charge (SOC) of the energy storage battery < the charging depth of the energy storage battery; the discharge power of the energy storage converter < the maximum discharge power of the energy storage battery; the charging power of the energy storage converter < the maximum charging power of the energy storage battery. Among them, the state of charge of the energy storage battery > the discharge depth of the energy storage battery and the discharge power of the energy storage converter < the maximum discharge power of the energy storage battery can be classified as the energy storage device discharge constraint, and the state of charge of the energy storage battery < the charging depth of the energy storage battery and the charging power of the energy storage converter < the maximum charging power of the energy storage battery can be classified as the energy storage device charging constraint.

[0071] In this step 2:

[0072] (1) The method of increasing the discharge power of the energy storage inverter is: switching the energy storage inverter in the shutdown state to the power-on state and the discharge mode, and determining the discharge power of the energy storage inverter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, or determining the discharge power increase based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the increased discharge power of the energy storage inverter based on the current discharge power of the energy storage inverter and the discharge power increase. The discharge power increase is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient. For the solution of switching the energy storage inverter from the shutdown state to the power-on state and the discharge mode, it is equivalent to adding the above discharge power increase to the original discharge power of 0, thereby obtaining the discharge power of the energy storage inverter;

[0073] (2) The method of reducing the discharge power of the energy storage inverter is: determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the reduced discharge power of the energy storage inverter based on the current discharge power of the energy storage inverter and the discharge power reduction amount, or switching the energy storage inverter in the power-on state and discharge mode to the power-off state. The discharge power reduction amount is the product of the maximum discharge power of the energy storage battery and the battery discharge power growth coefficient. For the solution of switching the energy storage inverter from the power-on state and discharge mode to the power-off state, it is equivalent to reducing the original discharge power to 0.

[0074] Based on this, step 2 specifically includes the following steps:

[0075] Step 2-1: Determine whether the energy storage converter is in the shutdown state, if so, execute step 2-2, if not, execute step 2-5;

[0076] Step 2-2: Determine whether the state of charge of the energy storage battery is greater than the depth of discharge of the energy storage battery. If so, execute step 2-3; if not, return to step 1;

[0077] Step 2-3: Determine whether the detected mains power > mains power reverse flow prevention threshold value is satisfied, that is, determine whether there is reverse flow between the energy storage system and the power grid. If so, that is, there is no reverse flow, then execute step 2-4; if not, that is, there is reverse flow, then return to step 1;

[0078] Step 2-4: Increase the discharge power of the energy storage converter, switch the energy storage converter in the shutdown state to the startup state and discharge mode, determine the discharge power of the energy storage converter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, the discharge power of the energy storage converter is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient, that is, it is equivalent to increasing the discharge power increase amount on the basis of the discharge power of 0, and the discharge power increase amount is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient, and then return to step 1;

[0079] Step 2-5: Determine whether the energy storage converter is in the power-on state and the discharge mode, if so, execute step 2-6, if not, execute step 2-12;

[0080] Step 2-6: Determine whether the state of charge of the energy storage battery is greater than the depth of discharge of the energy storage battery. If so, execute step 2-7; otherwise, execute step 2-11;

[0081] Step 2-7: Determine whether the detected mains power > mains power reverse flow prevention threshold value is satisfied, that is, determine whether there is reverse flow between the energy storage system and the power grid. If so, that is, there is no reverse flow, then execute step 2-8; if not, that is, there is reverse flow, then execute step 2-10;

[0082] Step 2-8: Determine whether the discharge power of the energy storage converter is less than the maximum discharge power of the energy storage battery. If so, execute step 2-9; otherwise, return to step 1;

[0083] Step 2-9: Increase the discharge power of the energy storage converter, determine the discharge power increase based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, the discharge power increase is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient, and obtain the increased discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power increase, the increased discharge power of the energy storage converter is the sum of the current discharge power of the energy storage converter and the discharge power increase, and then return to step 1;

[0084] Step 2-10: reducing the discharge power of the energy storage inverter, determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, the discharge power reduction amount being the product of the maximum discharge power of the energy storage battery and the battery discharge power growth coefficient, and obtaining the reduced discharge power of the energy storage inverter based on the current discharge power of the energy storage inverter and the discharge power reduction amount, the reduced discharge power of the energy storage inverter being the difference between the current discharge power of the energy storage inverter and the discharge power reduction amount, and then returning to step 1;

[0085] Step 2-11: reduce the discharge power of the energy storage converter, switch the energy storage converter in the on state and the discharge mode to the off state, and then return to step 1;

[0086] Step 2-12: Switch the energy storage converter to the shutdown state and return to step 1.

[0087] Step 3: When the current time is in the off-peak time period, determine the working state of the energy storage inverter and whether it meets the charging and discharging constraints of the energy storage device and the working constraints of the energy storage inverter. If the energy storage inverter is in the on state and charging mode or the off state and meets the charging and discharging constraints of the energy storage device and the working constraints of the energy storage inverter, then increase the charging power of the energy storage inverter and return to step 1. If the energy storage inverter is in the on state and charging mode and does not meet the charging and discharging constraints of the energy storage device or the working constraints of the energy storage inverter, then reduce the charging power of the energy storage inverter and return to step 1. If the energy storage inverter is in the on state and discharging mode, switch the energy storage inverter to the off state and return to step 1.

[0088] In step 3, the working constraints of the energy storage converter are: the discharge power of the energy storage converter is less than the maximum discharge power of the energy storage battery, and the charging power of the energy storage converter is less than the maximum charging power of the energy storage battery.

[0089] In this step 3:

[0090] (1) The method for increasing the charging power of the energy storage inverter is: determining the charging power increase based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the increased charging power of the energy storage inverter based on the current charging power of the energy storage inverter and the charging power increase, or switching the energy storage inverter in the shutdown state to the power-on state and charging mode, and determining the charging power of the energy storage inverter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery. The charging power increase is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient. For the solution of switching the energy storage inverter from the shutdown state to the power-on state and charging mode, it is equivalent to adding the above charging power increase to the original charging power of 0, thereby obtaining the charging power of the energy storage inverter;

[0091] (2) The method of reducing the charging power of the energy storage inverter is: determining the amount of charging power reduction based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the reduced charging power of the energy storage inverter based on the current charging power and charging power increase of the energy storage inverter, or switching the energy storage inverter in the power-on state and charging mode to the power-off state. The amount of charging power reduction is the product of the maximum charging power of the energy storage battery and the charging power growth coefficient. For the solution of switching the energy storage inverter from the power-on state and charging mode to the power-off state, it is equivalent to reducing the original charging power to 0.

[0092] Based on this, step 3 specifically includes the following steps:

[0093] Step 3-1: Determine whether the energy storage converter is in the power-on state and charging mode, if yes, execute step 3-2, if no, execute step 3-8;

[0094] Step 3-2: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-3; if not, execute step 3-7;

[0095] Step 3-3: Determine whether the detected mains power > mains power reverse flow prevention threshold value is satisfied, that is, determine whether there is reverse flow between the energy storage system and the power grid. If so, that is, there is no reverse flow, then execute step 3-4; if not, that is, there is reverse flow, then execute step 3-6;

[0096] Step 3-4: Determine whether the charging power of the energy storage converter is less than the maximum charging power of the energy storage battery. If so, execute step 3-5; otherwise, return to step 1;

[0097] Step 3-5: Increase the charging power of the energy storage inverter, determine the charging power increase based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, the charging power increase is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient, and obtain the increased charging power of the energy storage inverter based on the current charging power of the energy storage inverter and the charging power increase, the increased charging power of the energy storage inverter is the sum of the current charging power of the energy storage inverter and the charging power increase, and then return to step 1;

[0098] Step 3-6: reduce the charging power of the energy storage inverter, determine the charging power reduction amount based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, the charging power reduction amount is the product of the maximum charging power of the energy storage battery and the charging power growth coefficient, and obtain the reduced charging power of the energy storage inverter based on the current charging power of the energy storage inverter and the charging power increase, the reduced charging power of the energy storage inverter is the difference between the current charging power of the energy storage inverter and the charging power increase, and then return to step 1;

[0099] Step 3-7: Reduce the charging power of the energy storage converter, switch the energy storage converter in the power-on state and the charging mode to the power-off state, and then return to step 1;

[0100] Step 3-8: Determine whether the energy storage converter is in the shutdown state, if so, execute step 3-9, if not, execute step 3-12;

[0101] Step 3-9: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-10; if not, return to step 1;

[0102] Step 3-10: Determine whether the detected mains power > mains power reverse flow prevention threshold is met, that is, determine whether there is reverse flow between the energy storage system and the power grid. If so, that is, there is no reverse flow, then execute step 3-11; if not, that is, there is reverse flow, then return to step 1;

[0103] Step 3-11: Increase the charging power of the energy storage inverter, switch the energy storage inverter in the shutdown state to the power-on state and charging mode, and determine the charging power of the energy storage inverter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery. The charging power of the energy storage inverter is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient, which is equivalent to increasing the charging power increase amount on the basis of the charging power of 0, and the charging power increase amount is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient, and then return to step 1;

[0104] Step 3-12: Switch the energy storage converter to the shutdown state and return to step 1.

[0105] The above scheme provides a method for energy storage peak-shaving and valley-filling to prevent reverse flow and transformer overload for the microgrid, which can avoid the reverse grid access (reverse flow) of the energy storage device or the overload operation (overload) of the user's transformer. It can be seen that the scheme includes the following processes and steps:

[0106] 1. Collect information on users’ electricity usage periods, energy storage devices and transformer rated parameters;

[0107] 2. Enter the collected information in the strategy configuration table as the judgment conditions for each process when the plan is running;

[0108] 3. In the strategy configuration table, enter the battery charging power growth coefficient and the battery discharging power growth coefficient. These two items are the key parameters for implementing this solution. They specify the specific values ​​that need to be adjusted for the charging and discharging power of the energy storage device in the scenarios where the user's power consumption is normal, the user's power consumption is too low but the energy storage device is still discharging, and the user's power consumption is too high but the energy storage device is still charging. Through these two parameters, this solution implements the charging and discharging power adjustment without manual operation during the peak-shaving and valley-filling operation of the energy storage device;

[0109] 4. In the strategy configuration table, enter the mains power backflow prevention threshold, which is also a key parameter for implementing this strategy. It specifies when the strategy needs to adjust the charging and discharging power of the energy storage device and the direction of the adjustment (increase or decrease);

[0110] 5. The microgrid operates according to the scheme and adjusts the charging and discharging power of the energy storage device according to the instructions output in the scheme.

[0111] Compared with the existing solutions, this solution focuses on improving the existing solutions in the microgrid, which do not design a peak-shaving and valley-filling strategy for energy storage to prevent reverse flow and transformer overload, resulting in the energy storage device not being able to adjust the charging and discharging power in real time according to the user's power consumption, so it is easy for the energy storage device's power to be reversed to the grid or the user's transformer to be overloaded. This solution designs a peak-shaving and valley-filling strategy for energy storage that can prevent reverse flow and transformer overload, and does not require frequent manual operation. It only needs to pre-set the strategy operation conditions, and the strategy can run automatically. After the strategy is run, it will not affect the peak-shaving and valley-filling operation of the energy storage device in the microgrid, and can effectively prevent the reverse grid-connection of the energy storage device or the overload of the user's transformer.

[0112] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling energy storage peak shaving and valley filling, used to control an energy storage system connected to a power grid to achieve peak shaving and valley filling, wherein the energy storage system comprises an energy storage device, the energy storage device comprises an energy storage battery, and an energy storage converter connected to the energy storage battery, characterized in that: The energy storage peak shaving and valley filling control method comprises the following steps: Step 1: Determine whether the current time is within the peak time period, if yes, go to step 2, if no, go to step 3; Step 2: Determine the working state of the energy storage converter and whether the energy storage device charge and discharge constraint conditions are met, and determine whether there is reverse flow between the energy storage system and the power grid. If the energy storage converter is in the off state or the on state and the discharge mode, meets the energy storage device charge and discharge constraint conditions, and does not have reverse flow, then increase the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the off state and does not meet the energy storage device charge and discharge constraint conditions or reverse flow, then return to step 1. If the energy storage converter is in the on state and the discharge mode and does not meet the energy storage device charge and discharge constraint conditions or reverse flow, then reduce the discharge power of the energy storage converter and return to step 1. If the energy storage converter is in the on state and the charging mode, switch the energy storage converter to the off state and return to step 1. Step 3: Determine the working state of the energy storage converter and whether the charge and discharge constraints of the energy storage device and the working constraints of the energy storage converter are met. If the energy storage converter is in the power-on state and charging mode or the power-off state and meets the charge and discharge constraints of the energy storage device and the working constraints of the energy storage converter, then increase the charging power of the energy storage converter and return to step 1. If the energy storage converter is in the power-on state and charging mode and does not meet the charge and discharge constraints of the energy storage device or the working constraints of the energy storage converter, then reduce the charging power of the energy storage converter and return to step 1. If the energy storage converter is in the power-on state and discharging mode, switch the energy storage converter to the power-off state and return to step 1. The charging and discharging constraints of the energy storage device include: the state of charge of the energy storage battery > the discharge depth of the energy storage battery; the state of charge of the energy storage battery < the charging depth of the energy storage battery; the discharge power of the energy storage inverter < the maximum discharge power of the energy storage battery; the charging power of the energy storage inverter < the maximum charging power of the energy storage battery; the working constraints of the energy storage inverter are: the discharge power of the energy storage inverter < the maximum discharge power of the energy storage battery, and the charging power of the energy storage inverter < the maximum charging power of the energy storage battery.

2. The energy storage peak shaving and valley filling control method according to claim 1, characterized in that: In step 1, if the peak hour start time ≤ the current time < the peak hour end time, it is determined that the current time is within the peak hour period.

3. The energy storage peak shaving and valley filling control method according to claim 1, characterized in that: A mains power anti-backflow threshold is preset, and in step 2, the detected mains power and the mains power anti-backflow threshold are used to determine whether there is a backflow between the energy storage system and the power grid. When the detected mains power is greater than the mains power anti-backflow threshold, it is determined that there is no backflow.

4. The energy storage peak shaving and valley filling control method according to claim 1, characterized in that: In step 2, the method for increasing the discharge power of the energy storage converter is: switching the energy storage converter in the shutdown state to the power-on state and the discharge mode, and determining the discharge power of the energy storage converter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, or determining the discharge power increase amount based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the increased discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power increase amount; The method for reducing the discharge power of the energy storage inverter is: determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the discharge power of the energy storage inverter after the reduction based on the current discharge power of the energy storage inverter and the discharge power reduction amount, or switching the energy storage inverter in the power-on state and discharge mode to the power-off state.

5. The energy storage peak shaving and valley filling control method according to claim 4 is characterized in that: The step 2 comprises the following steps: Step 2-1: Determine whether the energy storage converter is in a shutdown state, if yes, execute step 2-2, if no, execute step 2-5; Step 2-2: Determine whether the state of charge of the energy storage battery > the depth of discharge of the energy storage battery is established, if so, execute step 2-3, if not, return to step 1; Step 2-3: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 2-4. If so, return to step 1. Step 2-4: increasing the discharge power of the energy storage converter, switching the energy storage converter from the shutdown state to the startup state and the discharge mode, and determining the discharge power of the energy storage converter based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and then returning to step 1; Step 2-5: Determine whether the energy storage converter is in the power-on state and the discharge mode, if yes, execute step 2-6, if no, execute step 2-12; Step 2-6: Determine whether the state of charge of the energy storage battery> the depth of discharge of the energy storage battery is established, if so, execute step 2-7, if not, execute step 2-11; Step 2-7: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 2-8. If so, execute step 2-10. Step 2-8: Determine whether the discharge power of the energy storage converter is less than the maximum discharge power of the energy storage battery. If so, execute step 2-9; otherwise, return to step 1; Step 2-9: increasing the discharge power of the energy storage converter, determining the discharge power increase amount based on the set discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the increased discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power increase amount, and then returning to step 1; Step 2-10: reducing the discharge power of the energy storage converter, determining the discharge power reduction amount based on the set battery discharge power growth coefficient and the maximum discharge power of the energy storage battery, and obtaining the reduced discharge power of the energy storage converter based on the current discharge power of the energy storage converter and the discharge power reduction amount, and then returning to step 1; Step 2-11: reducing the discharge power of the energy storage converter, switching the energy storage converter in the on state and the discharge mode to the off state, and then returning to step 1; Step 2-12: Switch the energy storage converter to the shutdown state and then return to step 1.

6. The energy storage peak shaving and valley filling control method according to claim 5, characterized in that: The discharge power reduction amount is the product of the maximum discharge power of the energy storage battery and the battery discharge power growth coefficient, and the discharge power increase amount is the product of the maximum discharge power of the energy storage battery and the discharge power growth coefficient.

7. The energy storage peak shaving and valley filling control method according to claim 1, characterized in that: In step 3, the method for increasing the charging power of the energy storage converter is as follows: determining the charging power increase amount based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the charging power of the energy storage converter after the current charging power of the energy storage converter and the charging power increase amount, or switching the energy storage converter in the shutdown state to the power-on state and the charging mode, and determining the charging power of the energy storage converter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery; The method for reducing the charging power of the energy storage inverter is: determining the charging power reduction amount based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, and reducing the charging power of the energy storage inverter based on the current charging power of the energy storage inverter and the charging power increase, or switching the energy storage inverter in the power-on state and charging mode to the power-off state.

8. The energy storage peak shaving and valley filling control method according to claim 7, characterized in that: The step 3 comprises the following steps: Step 3-1: Determine whether the energy storage converter is in the power-on state and the charging mode, if so, execute step 3-2, if not, execute step 3-8; Step 3-2: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-3; otherwise, execute step 3-7; Step 3-3: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 3-4. If so, execute step 3-6. Step 3-4: Determine whether the charging power of the energy storage converter is less than the maximum charging power of the energy storage battery. If so, execute step 3-5; otherwise, return to step 1; Step 3-5: increasing the charging power of the energy storage converter, determining the charging power increase amount based on the set battery charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the increased charging power of the energy storage converter based on the current charging power of the energy storage converter and the charging power increase amount, and then returning to step 1; Step 3-6: reducing the charging power of the energy storage converter, determining the amount of reduction in charging power based on the set charging power growth coefficient and the maximum charging power of the energy storage battery, and obtaining the reduced charging power of the energy storage converter based on the current charging power of the energy storage converter and the charging power increase, and then returning to step 1; Step 3-7: reducing the charging power of the energy storage converter, switching the energy storage converter in the power-on state and the charging mode to the power-off state, and then returning to step 1; Step 3-8: Determine whether the energy storage converter is in a shutdown state, if yes, execute step 3-9, if no, execute step 3-12; Step 3-9: Determine whether the state of charge of the energy storage battery is less than the depth of charge of the energy storage battery. If so, execute step 3-10. If not, return to step 1. Step 3-10: Determine whether there is reverse flow between the energy storage system and the power grid. If not, execute step 3-11. If reverse flow, return to step 1. Step 3-11: increasing the charging power of the energy storage converter, switching the energy storage converter from the shutdown state to the startup state and charging mode, and determining the charging power of the energy storage converter based on the battery charging power growth coefficient and the maximum charging power of the energy storage battery, and then returning to step 1; Step 3-12: Switch the energy storage converter to the shutdown state and then return to step 1.

9. The energy storage peak shaving and valley filling control method according to claim 8, characterized in that: The charging power increase is the product of the maximum charging power of the energy storage battery and the battery charging power growth coefficient, and the charging power reduction is the product of the maximum charging power of the energy storage battery and the charging power growth coefficient.

10. A method for controlling peak shaving and valley filling of energy storage according to any one of claims 5 to 9, characterized in that: The value of the battery charging power growth coefficient and the battery discharging power growth coefficient is n%, where n is an integer divisible by 100.

11. The energy storage peak shaving and valley filling control method according to claim 10, characterized in that: The value of n is 1, 2, 4, 5, 10, 20 or 50.

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