Black-start method for energy storage system of new energy power station

Abstract

The invention discloses a black-start method for an energy storage system of a new energy power station. The method comprises a normal black-start mode and a low-electric-quantity black-start mode. Before black start, all converters of the energy storage system are traversed; when a state of charge (SOC) value of a battery connected with at least one converter in the energy storage system is greater than a threshold value, executing a normal black-start mode; and when the SOCs of all the converters in the energy storage system are smaller than a threshold value, executing a low-electric-quantity black-start mode. According to the method, the starting sequence of the converters is preferentially selected, and the photovoltaic inverter is automatically started and the power of the photovoltaic inverter is limited in the black-start process to assist the energy storage system to establish stable voltage and frequency, so that the black-start success rate of the energy storage system is improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage system control, and in particular to a black start method for a new energy power plant energy storage system. Background Technology

[0002] In recent years, an increasing number of off-grid renewable energy power generation systems have been applied in remote mountainous areas, areas without electricity, and islands. However, due to the strong fluctuations and randomness of photovoltaic and wind power output, the instability of renewable energy power generation severely restricts its application. Energy storage technology can achieve peak shaving and valley filling, frequency and voltage regulation, and smoothing load fluctuations, thus becoming an effective supporting technology for improving the reliability of off-grid renewable energy power generation systems.

[0003] Compared to the main power grid, off-grid renewable energy power station energy storage systems are less stable. Firstly, due to their lower capacity and insufficient support margin, grid protection mechanisms often activate and the entire station loses power when the external power grid fails. Secondly, during periods of insufficient sunlight or at night, the energy storage system needs to provide continuous power; improper load distribution can cause the system's batteries to run dry and shut down. In such cases, a black start is required for the renewable energy power station's energy storage system.

[0004] Black start of a renewable energy storage system refers to the process by which the energy storage system of a renewable energy power station automatically restarts and restores power to the entire station when the entire station's energy storage system is shut down and the external power grid loses power, and then gradually restores power supply to the grid in coordination with grid dispatch. This process generally consists of three stages: energy storage system black start, photovoltaic / wind power system recovery, and load recovery. In remote operation and maintenance mode, renewable energy storage power stations are only equipped with a small number of maintenance personnel. In this situation, using traditional methods to gradually start the energy storage system requires manual inspection and operation, which is time-consuming, increases the system's blackout time, and causes unnecessary battery power consumption. When the battery power is too low, traditional manual start-up methods may cause the battery to run out of power during the black start process, leading to black start failure.

[0005] Currently, there is limited research on black-start methods for energy storage systems in new energy power plants. Chinese patent CN201710997335.9 discloses a startup method and system for energy storage-type photovoltaic power plants supporting grid black-start. This method, from the perspective of grid dispatch, predicts the photovoltaic power of multiple photovoltaic energy storage power plants within the grid and selects the optimal one for black-start. However, it does not provide specific startup strategies for individual photovoltaic energy storage power plants, nor does it consider the situation of off-grid photovoltaic energy storage power plants or the special condition of low battery power in the energy storage system. Chinese patent 201910136494.9 discloses a black-start system and method for factory microgrids. This method simply selects energy storage units with high remaining capacity for self-starting, but it does not consider the condition of low battery power in the energy storage system, nor does it make reasonable use of the photovoltaic array during the black-start process. Chinese patent 201710983900.6 discloses an online decision-making method for black-start recovery of distribution network islands based on a dynamic programming model. This method utilizes a diesel generator and energy storage as the main power source for black start to establish a stable voltage and frequency, but does not involve the control method of the energy storage system during black start. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a black-start method for a new energy power plant energy storage system.

[0007] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0008] A black-start method for a new energy power plant energy storage system includes the following steps:

[0009] 1) Collect the main circuit information of the energy storage system, including the grid connection voltage of the energy storage system and the outgoing switch and the position of each collector line switch;

[0010] 2) Collect information from each energy storage converter and photovoltaic inverter. The information of the energy storage converter includes a first start-up permission signal, a battery discharge signal, a first operation signal, the state of charge value of the battery connected to the energy storage converter, and the maximum charging power limit. The information of the photovoltaic inverter includes a second start-up permission signal and a second operation signal.

[0011] 3) Determine if the energy storage system meets the black start conditions. If it does, proceed to step 4); otherwise, terminate this sequential control.

[0012] 4) Sort each energy storage converter in descending order of the state of charge (SOC) value of the corresponding connected battery, and determine the serial number of the energy storage converter whose corresponding battery is depleted and the serial number of the energy storage converter with the largest SOC value of the corresponding connected battery.

[0013] 5) When the maximum value of the state of charge (SOC) of the battery connected to each energy storage converter is greater than SOC_low, the black start mode is executed; when the maximum value of the SOC of the battery connected to each energy storage converter is less than or equal to SOC_low, the low-power black start mode is executed; where SOC_low is a preset low-power black start mode threshold.

[0014] In step 3) above, the black start conditions for the energy storage system are as follows:

[0015] The grid connection point voltage is less than 10% of the rated voltage, the outgoing switch is open, and at least one energy storage converter has a start-up permission signal of 1 and a venting signal of 0.

[0016] In step 5) above, the strategy for executing the black boot mode is as follows:

[0017] ① Start the energy storage converter with the highest state of charge value of the connected battery using a zero-power command;

[0018] ②After the energy storage converter in ① is started, start the other energy storage converters with zero power command, except for the energy storage converter with the largest state of charge value of the battery connected to it and the energy storage converter whose battery has been discharged.

[0019] ③ Close the outgoing line switch;

[0020] ④ Close all collector circuit switches and start the photovoltaic inverter;

[0021] ⑤ Start the corresponding energy storage converter with the battery already discharged using the charging power command.

[0022] In step 5) above, the strategy for implementing the low-power black boot mode is as follows:

[0023] Ⅰ) Close the collector circuit switch;

[0024] II) Start the energy storage converter with the highest state of charge value of the connected battery using a zero-power command;

[0025] III) After the energy storage converter in II) has started up, start any one of the photovoltaic inverters and limit its power to P solar_max to charge the already started energy storage converter; where, j represents the serial number of the energy storage converter, j is an integer, 1≤j≤n, n represents the number of energy storage converters, n is an integer, n≥2; k represents the serial number of the photovoltaic inverter, k is an integer, 1≤k≤m, m represents the number of photovoltaic inverters, m is an integer, m≥2; P(j) represents the maximum charging power limit of the energy storage converter with serial number j, State_pcs(j) represents the operation signal of the energy storage converter with serial number j, and State_inv(k) represents the start command of the photovoltaic inverter with serial number k;

[0026] IV) Start the energy storage converters in descending order of the state of charge (SOC) values ​​of the connected batteries, except for the energy storage converter with the highest SOC value and the energy storage converter whose battery is already depleted.

[0027] V) Start the remaining photovoltaic inverters and limit their respective photovoltaic power to Psolar_max to charge the already started energy storage converters;

[0028] VI) Close the outgoing line switch;

[0029] VII) Start the corresponding energy storage converter with the battery already discharged using the charging power command.

[0030] Compared with existing technologies, this invention enables one-button sequential black-start of the energy storage system and photovoltaic inverter when the battery state of charge (SOC) is normal. When the SOC is low, it can preferentially select the startup sequence of the energy storage converter, coordinating with the interleaved startup of the photovoltaic inverter and limiting its operation to an appropriate power level, thereby improving the black-start success rate of the energy storage system. This invention is applicable to off-grid renewable energy power station energy storage systems, is easy to implement, and is stable and reliable in engineering applications. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the energy storage system structure of a new energy power station in an embodiment of the present invention;

[0032] Figure 2 This is a flowchart of a black start method for a new energy power station energy storage system according to the present invention;

[0033] Figure 3 The flowcharts for the normal black start mode and the low power black start mode of the present invention are shown, wherein (a) is the normal black start mode and (b) is the low power black start mode. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0035] This embodiment provides a black start method for a new energy power station energy storage system. Figure 1 This is a schematic diagram of an energy storage system for a new energy power station, consisting of n energy storage converters and m photovoltaic inverters. Where n ≥ 2 and m ≥ 2. The photovoltaic inverters and energy storage converters are connected to the busbar via their respective collector lines, and ultimately connected to the external power grid or load phase via outgoing switches.

[0036] The station is equipped with a coordination and control device to coordinate and control its photovoltaic energy storage system. This device has the ability to exchange information with the energy storage converter and the photovoltaic inverter, and its information exchange includes the following:

[0037] The information collected from the energy storage converter includes the start-up enable signal Ready_pcs(j), the battery empty signal Empty_pcs(j), the operation signal State_pcs(j), the state of charge value SOC_pcs(j) of the battery connected to the energy storage converter, and the maximum charging power limit P(j).

[0038] The instructions issued to the energy storage converter include the start command Start_pcs(j);

[0039] The information collected from the photovoltaic inverter includes the start-up enable signal Ready_inv(k) and the running signal State_inv(k);

[0040] The instructions issued to the photovoltaic inverter include the start command Start_inv(k) and the power limit Psolar_max;

[0041] Where j represents the serial number of the energy storage converter, j is an integer, 1≤j≤n; k represents the serial number of the photovoltaic inverter, k is an integer, 1≤k≤m.

[0042] The black-start method for the energy storage system of a new energy power station of the present invention is carried out according to the following steps:

[0043] 1) The coordination and control device collects the main circuit information of the photovoltaic power station energy storage system, including the grid connection point voltage uabc_pcc of the energy storage system and the position of the outgoing line switch and the switch of each collector line.

[0044] 2) The coordination control device collects information from each energy storage converter and photovoltaic inverter. The information of the energy storage converter includes the start-up enable signal Ready_pcs(j), the battery discharge signal Empty_pcs(j), the operation signal State_pcs(j), the state of charge value SOC_pcs(j) of the corresponding connected battery, and the maximum charging power limit Ppcs_max(j). The information of the photovoltaic inverter includes the start-up enable signal Ready_inv(k) and the operation signal State_inv(k).

[0045] 3) The coordination control device determines whether the energy storage system meets the black start conditions. The black start conditions are: uabc_pcc < 10%Ue, the outgoing line switch is in the open position, and at least one energy storage converter has a start-up permission signal Ready_pcs of 1 and Empty_pcs of 0. Wherein, Ue is the rated value of the grid connection point voltage.

[0046] 4) Coordinate the black start of the control and traverse the state of charge (SOC) values ​​of the batteries connected to each energy storage converter, sort them from largest to smallest, and determine the sequence number of the energy storage converter whose battery is empty (Empty_pcs(j) = 1) {empty_x} and the sequence number of the energy storage converter with the largest battery SOC value j_max. Wherein, SOC_pcs(j_max) = max{SOC_pcs(1), ...,SOC_pcs(n)}, 0≤j≤n, and empty_x represents the energy storage converter whose battery is empty.

[0047] 5) The coordinating controller selects the energy storage system startup mode based on SOC_pcs(j_max).

[0048] When SOCpcs(j_max) > SOC_low, execute the normal black boot mode:

[0049] 1) Set Ppcs_order(j) to 0 to start the energy storage converter with sequence number j_max using zero power command;

[0050] 2) When the energy storage converter with serial number j_max has finished starting, that is, when State_pcs (j_max) is 1, start the remaining energy storage converters with Ready_pcs(j) as 1 and Empty_pcs(j) as 0 with zero power command.

[0051] 3) Close the outgoing line switch;

[0052] 4) Close all collector line switches and start the photovoltaic inverter with Ready_inv(k) set to 1;

[0053] 5) Set Ppcs_order(empty_x) to a negative value, that is, start the energy storage converter with sequence number {empty_x} with the charging power command.

[0054] When SOC_pcs(j_max)≤SOC_low, execute the low-power black boot mode:

[0055] 1) Close the collector circuit switch;

[0056] 2) Set Ppcs_order(j) to 0, that is, start the energy storage converter with sequence number j_max with zero power command;

[0057] 3) When the energy storage inverter with serial number j_max has finished starting up, i.e., State_pcs(j_max) is 1, start any photovoltaic inverter with Ready_inv(k) of 1 and limit its power to Psolar_max to charge the already started energy storage inverter. ;

[0058] 4) Start the remaining energy storage converters with Ready_pcs(j) equal to 1 and Empty_pcs(j) equal to 0 in descending order of SOC;

[0059] 5) Start the remaining photovoltaic inverters with Ready_inv(k) set to 1; and limit their power to Psolar_max to charge the energy storage converter;

[0060] 6) Close the outgoing line switch;

[0061] 7) Set Ppcs_order(empty_x) to a negative value, that is, start the energy storage converter with sequence number {empty_x} with the charging power command.

[0062] SOC_low is the preset threshold for low-power black start mode.

[0063] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A black-start method for a new energy power station energy storage system, characterized in that, Includes the following steps: 1) Collect the main circuit information of the energy storage system, including the grid connection voltage of the energy storage system and the outgoing switch and the position of each collector line switch; 2) Collect information from each energy storage converter and photovoltaic inverter. The information of the energy storage converter includes a first start-up permission signal, a battery discharge signal, a first operation signal, the state of charge value of the battery connected to the energy storage converter, and the maximum charging power limit. The information of the photovoltaic inverter includes a second start-up permission signal and a second operation signal. 3) Determine if the energy storage system meets the black start conditions. If it does, proceed to step 4); otherwise, terminate this sequential control. 4) Sort each energy storage converter in descending order of the state of charge (SOC) value of the corresponding connected battery, and determine the serial number of the energy storage converter whose corresponding battery is depleted and the serial number of the energy storage converter with the largest SOC value of the corresponding connected battery. 5) When the maximum value of the state of charge (SOC) of the battery connected to each energy storage converter is greater than SOC_low, the black start mode is executed; when the maximum value of the SOC of the battery connected to each energy storage converter is less than or equal to SOC_low, the low-power black start mode is executed; where SOC_low is a preset low-power black start mode threshold. The strategy for executing the black boot mode is as follows: ① Start the energy storage converter with the highest state of charge value of the connected battery using a zero-power command; ②After the energy storage converter in ① is started, start the other energy storage converters with zero power command, except for the energy storage converter with the largest state of charge value of the battery connected to it and the energy storage converter whose battery has been discharged. ③ Close the outgoing line switch; ④ Close all collector circuit switches and start the photovoltaic inverter; ⑤ Start the energy storage converter whose corresponding battery has been discharged using the charging power command; The black start conditions for an energy storage system are as follows: The grid connection point voltage is less than 10% of the rated voltage, the outgoing switch is open, and at least one energy storage converter has a start-up permission signal of 1 and a venting signal of 0.

2. The black-start method for a new energy power station energy storage system according to claim 1, characterized in that, In step 5), the strategy for implementing the low-power black start mode is as follows: Ⅰ) Close the collector circuit switch; Ⅱ) Start the energy storage converter with the highest state of charge value of the connected battery using a zero-power command; III) After the energy storage converter in II) has started up, start any one of the photovoltaic inverters and limit its power to Psolar-max to charge the already started energy storage converter; among which, j represents the serial number of the energy storage converter, j is an integer, 1≤j≤n, n represents the number of energy storage converters, n is an integer, n≥2; k represents the serial number of the photovoltaic inverter, k is an integer, 1≤k≤m, m represents the number of photovoltaic inverters, m is an integer, m≥2; P(j) represents the maximum charging power limit of the energy storage converter with serial number j, State_pcs(j) represents the operating signal of the energy storage converter with serial number j, and State_inv(k) represents the start command of the photovoltaic inverter with serial number k; IV) In descending order of the state of charge (SOC) values ​​of the connected batteries, start the remaining energy storage converters in sequence, except for the one with the highest SOC value and the one whose battery is already depleted. V) Start the remaining photovoltaic inverters and limit their respective photovoltaic power to Psolar_max to charge the already started energy storage converters; VI) Close the outgoing line switch; VII) Start the energy storage converter whose corresponding battery has been discharged using the charging power command.

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