A method for black start dispatching control of energy storage power station considering SOC self-balancing

Abstract

The present invention provides a method for black start dispatching and controlling an energy storage power station taking into account SOC self-balancing. The present invention implements group balancing control inside the energy storage power station so that the energy storage power station can display the characteristics of an independent power supply to the outside like a microgrid. The present invention does not require additional system configuration. The present invention has the ability to automatically balance the energy storage SOC. An unbalanced energy storage SOC will cause a certain ESS unit to discharge first and then exit the system, thereby accelerating the discharge speed of the remaining ESS units and shortening the service life of the ESS. In the present invention, a SOC self-balancing strategy based on PQ energy storage is proposed in the station control dispatching strategy to keep the energy storage SOC consistent and ensure the safety of energy storage.

Description

Technical Field

[0001] The invention relates to a black start control method for an electrochemical container energy storage power station, and belongs to the field of automatic control of new energy power generation, in particular to black start control of a container energy storage power station. Background Art

[0002] In recent years, with the rapid development of new energy technologies, more and more renewable energy sources (RES) such as photovoltaics and wind turbines have been connected to large power grids, which has continuously increased the installed capacity of distributed power sources. More and more distributed power sources are connected to microgrids through power electronic devices, which brings clean energy while also bringing huge challenges to the reliable operation of the power system. With the rapid development of new energy power generation technology, considering the volatility and intermittent characteristics of RES power output, in order to meet the stable operation of the system, energy storage systems (ESS) of relevant capacity are usually required. With the construction and development of new power systems, energy storage power stations will play a vital role in the power balance of power systems. Under the new power system model, both new energy generation and load are uncontrollable factors, and the dispatching balance of the power grid has to be supported by energy storage systems. It can be predicted that the scale of energy storage power stations will be very large in the future.

[0003] Energy storage power stations use their own charging and discharging characteristics to help the power system achieve dynamic balance of power, and the construction of large-scale energy storage power stations will also give them a richer role value. Energy storage power stations themselves store electricity and have the ability to provide black start power. Therefore, large-capacity energy storage power stations equipped with black start power function will become an important attribute of energy storage systems.

[0004] Energy storage power stations are generally composed of multiple container energy storage units in parallel. The commonly used control types of energy storage power inverters are mainly constant voltage and frequency (volt & frequency, VF) and constant power (PQ) control modes. In general, energy storage power stations work in PQ mode, accept the dispatch of the power grid, and act as a grid regulation function. When the energy storage power source is used as a black start power source, the energy storage inverter needs to work in VF control mode as a voltage source. When the energy storage power station is used as a voltage source, the phase of the sinusoidal voltage waveform output by each energy storage container unit needs to be synchronized. In addition, the imbalance of the energy storage state of charge (State of Charge, SOC) will cause a certain ESS unit to discharge first and then exit the system, thereby accelerating the discharge speed of the remaining ESS units and shortening the service life of the ESS. The ability of the container energy storage unit in VF mode to maintain parallel synchronization determines the capacity of the black start power supply. Due to the high requirements for synchronization capability and the need to consider the balanced energy storage SOC at the same time, the container parallel black start solution in VF mode is difficult to apply in large-capacity energy storage systems. For large-scale energy storage power stations with a capacity of more than 100 megawatts, further research and demonstration of more appropriate black start power supply technology solutions are still needed. Summary of the invention

[0005] The purpose of the present invention is to address the technical problem of implementing black start power supply in large energy storage power stations and to propose a black start solution for group control of energy storage power stations.

[0006] In order to achieve the above object, the technical solution of the present invention is to provide a method for black start dispatching control of an energy storage power station considering SOC self-balancing, which is characterized by comprising the following steps:

[0007] Step 1: Divide all energy storage containers in the energy storage power station into I+1 groups, one of which is a VF energy storage group, and the remaining I groups are PQ energy storage groups, I≥1;

[0008] The VF energy storage group and the PQ energy storage group are connected to the AC common bus through an inverter, and the AC common bus supplies power to the load;

[0009] The VF energy storage group is controlled by a VF controller, and each PQ energy storage group is controlled by a PQ controller. The VF controller and all PQ controllers receive instructions from the main control station of the energy storage power station;

[0010] Step 2: When the energy storage power station is in the black start operation mode, the black start strategy is implemented through the main control station. At this time, the main control station sends instructions to the VF controller, and the VF controller implements the VF control strategy, so that the VF energy storage group automatically establishes the no-load bus voltage and closes the switch in parallel to the AC common bus;

[0011] Step 3: The main control station sends instructions to each PQ controller to start each PQ energy storage group and connect it to the AC common bus.

[0012] Step 4: After the load is connected, the main control station uses the SOC self-balancing energy storage power station dispatching control strategy to dispatch and control each PQ energy storage group, which specifically includes the following steps:

[0013] Step 401: Obtain the SOC value SOC of each PQ energy storage group i 、SOC value of VF energy storage group SOC VF , bus load P L , where SOC i represents the SOC value of the i-th PQ energy storage group;

[0014] Step 402: Calculate and obtain the dispatch output power of each PQ energy storage group. Suppose the dispatch output power of the i-th PQ energy storage group is P i , then:

[0015]

[0016] In the formula, w i is the energy storage capacity of the i-th PQ energy storage group; W all is the total capacity of the entire energy storage power station; n is the regulation coefficient; ΔSOC i is the relative deviation of the state of charge of the i-th PQ energy storage group, ΔSOC i =SOC i -SOC VF ;

[0017] Step 403: The main control station sends the dispatched output power of each PQ energy storage group to the PQ controller of the corresponding PQ energy storage group, and each PQ energy storage group responds to the dispatched output according to the dispatched output power.

[0018] Preferably, the VF energy storage group is composed of multiple energy storage containers working in VF mode and operating synchronously in parallel; each of the PQ energy storage groups is composed of multiple energy storage containers working in PQ mode and connected in parallel.

[0019] Preferably, in step 2, when the VF controller implements the VF control strategy, the VF controller first collects the load voltage and the output current of the inverter, calculates the active power and reactive power output by each PQ energy storage group as a micro power source, and finally generates the control signal required by the inverter through a dual closed-loop control system of voltage and current.

[0020] Preferably, when designing the dual closed-loop control system, a power reference value is first given externally, and then a suitable coordinate transformation reference axis is selected to perform coordinate transformation on the collected load voltage and inverter output current so that the active component and the reactive component are decoupled and controlled separately.

[0021] Preferably, in step 3, after the PQ energy storage group is connected to the AC common bus, the inverter is controlled by the control signal generated by the dual closed-loop control system of voltage and current, so that each PQ energy storage group acts as a micro power source to inject the active power and reactive power calculated in step 2 into the AC common bus.

[0022] Preferably, in step 402, the adjustment coefficient n is adjusted as needed according to specific engineering requirements, so as to change the output value of each PQ energy storage group when the SOC values ​​of the PQ energy storage groups are inconsistent, thereby affecting the speed of balancing the SOC state of each PQ energy storage group.

[0023] The present invention implements group balancing control inside the energy storage power station, so that the energy storage power station can show the characteristics of an independent power supply to the outside world like a microgrid. Compared with the prior art solution, the present invention has the following beneficial effects:

[0024] 1. No additional system configuration is required. In normal mode, the energy storage power station mainly uses its own charging and discharging characteristics to respond to the dispatching requirements of the superior, adjust the power grid, and work in PQ mode. In the case of black start, it will be used as the main power source. Among them, the VF energy storage group only needs to start the VF control strategy in the controller, and the rest of the PQ energy storage does not need to be changed. When building an energy storage power station, the equipment configuration will not be increased, and it is friendly and compatible with different working modes.

[0025] 2. Possess the ability to automatically balance the energy storage SOC. An unbalanced energy storage SOC will cause a certain ESS unit to discharge first and then exit the system, thereby accelerating the discharge speed of the remaining ESS units and shortening the service life of the ESS. In the present invention, a SOC self-balancing strategy based on PQ energy storage is proposed in the station control scheduling strategy to keep the energy storage SOC consistent and ensure energy storage safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the present invention;

[0027] Figure 2 It is a schematic diagram of the layered structure of the present invention;

[0028] Figure 3 is the relationship curve between ΔSOC and acceleration factor;

[0029] Figure 4 The simulation results are shown. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] like Figure 1 As shown, the present embodiment discloses a method for black start dispatching control of an energy storage power station considering SOC self-balancing, including the following steps:

[0032] Step 1: Combine Figure 2 , all the energy storage containers in the energy storage power station are divided into several groups nearby, one of which is the VF energy storage group, and the remaining groups are PQ energy storage groups. The number of PQ energy storage groups can be determined according to the scale of the energy storage power station. It can be one or multiple PQ energy storage groups. The VF energy storage group is composed of multiple energy storage containers working in VF mode that are synchronously connected in parallel; each PQ energy storage group is composed of multiple energy storage containers working in PQ mode in parallel. The PQ control mode is consistent with the normal operating mode of the energy storage power station, and no additional configuration or changes are required.

[0033] The VF energy storage group and the PQ energy storage group are connected to the AC common bus through an inverter, and the AC common bus supplies power to the load.

[0034] The VF energy storage group is controlled by a VF controller, and each PQ energy storage group is controlled by a PQ controller. The VF controller and all PQ controllers receive instructions from the main control station of the energy storage power station.

[0035] Step 2, when the energy storage power station is in the black start operation mode, there is a problem of lack of support for voltage and frequency. In order to solve the above problems, the present invention can generate stable system voltage and frequency through the VF control strategy. Specifically: when the energy storage power station is in the black start operation mode, the black start strategy is implemented by the main control station. At this time, the main control station sends an instruction to the VF controller, and the VF controller implements the VF control strategy, so that the VF energy storage group establishes the no-load bus voltage by itself, and closes the switch in parallel to the AC common bus. When the VF controller implements the VF control strategy, the VF controller first collects the load voltage and the output current of the inverter, calculates the active power and reactive power output by each PQ energy storage group as a micro power source, and finally generates the control signal required by the inverter through the dual closed-loop control system of voltage and current. When designing a dual closed-loop control system, the power reference value is first given externally, and then a suitable coordinate transformation reference axis is selected to perform coordinate transformation on the collected load voltage and the output current of the inverter, so that the active component and the reactive component can be decoupled and controlled separately.

[0036] Step 3: The main control station sends instructions to each PQ controller to start each PQ energy storage group and connect it to the AC common bus. Under the control of the control signal generated by the dual closed-loop control system of voltage and current, the inverter enables each PQ energy storage group to inject the active power and reactive power calculated in step 2 into the AC common bus as a micro power source.

[0037] Step 4: After the load is connected, the main control station uses the SOC self-balancing energy storage power station dispatching control strategy to dispatch and control each PQ energy storage group, which specifically includes the following steps:

[0038] Step 401: Obtain the SOC value SOC of each PQ energy storage group i 、SOC value of VF energy storage group SOC VF , bus load P L , where SOC i represents the SOC value of the i-th PQ energy storage group;

[0039] Step 402: Calculate and obtain the dispatch output power of each PQ energy storage group. Suppose the dispatch output power of the i-th PQ energy storage group is P i , then:

[0040]

[0041] In the formula, w i is the energy storage capacity of the i-th PQ energy storage group; W all is the total capacity of the entire energy storage power station; n is the regulation coefficient; ΔSOC i is the relative deviation of the state of charge of the i-th PQ energy storage group, ΔSOC i =SOC i -SOC VF ;

[0042] like Figure 3 As shown, the adjustment coefficient n can change the output value of each PQ energy storage group when the SOC value of each PQ energy storage group is inconsistent, affecting the speed of balanced adjustment of the SOC state of each PQ energy storage group, and can be adjusted as needed according to specific project needs;

[0043] Step 403: The main control station sends the dispatched output power of each PQ energy storage group to the PQ controller of the corresponding PQ energy storage group, and each PQ energy storage group responds to the dispatched output according to the dispatched output power.

[0044] In the simulation experiment, a VF energy storage group and a PQ energy storage group are set up, each with a capacity of 1MW. The initial stage of the simulation is no-load, and the experimental operation of sudden load increase and decrease is simulated to verify the power response characteristics of the energy storage power station. The experimental results obtained are as follows Figure 4 shown.

Claims

1. A method for black start dispatching control of energy storage power station considering SOC self-balancing, characterized in that: The following steps are involved: Step 1: Divide all energy storage containers in the energy storage power station into I+1 groups, one of which is a VF energy storage group, and the remaining I groups are PQ energy storage groups, I≥1; The VF energy storage group and the PQ energy storage group are connected to the AC common bus through an inverter, and the AC common bus supplies power to the load; The VF energy storage group is controlled by a VF controller, and each PQ energy storage group is controlled by a PQ controller; the VF controller and all PQ controllers receive instructions from the main control station of the energy storage power station; Step 2: When the energy storage power station is in the black start operation mode, the black start strategy is implemented through the main control station. At this time, the main control station sends instructions to the VF controller, and the VF controller implements the VF control strategy, so that the VF energy storage group automatically establishes the no-load bus voltage and closes the switch in parallel to the AC common bus; Step 3: The main control station sends instructions to each PQ controller to start each PQ energy storage group and connect it to the AC common bus. Step 4: After the load is connected, the main control station uses the SOC self-balancing energy storage power station dispatching control strategy to dispatch and control each PQ energy storage group, which specifically includes the following steps: Step 401: Obtain the SOC value SOC of each PQ energy storage group i 、SOC value of VF energy storage group SOC VF , bus load P L , where SOC i represents the SOC value of the i-th PQ energy storage group; Step 402: Calculate and obtain the dispatch output power of each PQ energy storage group. Suppose the dispatch output power of the i-th PQ energy storage group is P i , then: In the formula, w i is the energy storage capacity of the i-th PQ energy storage group; W all is the total capacity of the entire energy storage power station; n is the regulation coefficient; ΔSOC i is the relative deviation of the state of charge of the i-th PQ energy storage group, ΔSOC i =SOC i -SOC VF ; Step 403: The main control station sends the dispatched output power of each PQ energy storage group to the PQ controller of the corresponding PQ energy storage group, and each PQ energy storage group responds to the dispatched output according to the dispatched output power.

2. A method for black start dispatching and controlling an energy storage power station considering SOC self-balancing as claimed in claim 1, characterized in that: The VF energy storage group is composed of multiple energy storage containers working in VF mode and operating synchronously in parallel; each of the PQ energy storage groups is composed of multiple energy storage containers working in PQ mode and connected in parallel.

3. A method for black start dispatching and controlling an energy storage power station considering SOC self-balancing according to claim 1, characterized in that: In step 2, when the VF controller implements the VF control strategy, the VF controller first collects the load voltage and the output current of the inverter, calculates the active power and reactive power output by each PQ energy storage group as a micro power source, and finally generates the control signal required by the inverter through a dual closed-loop control system of voltage and current.

4. A method for black start dispatching and controlling an energy storage power station considering SOC self-balancing as claimed in claim 3, characterized in that: When designing the dual closed-loop control system, a power reference value is first given externally, and then a suitable coordinate transformation reference axis is selected to perform coordinate transformation on the collected load voltage and the output current of the inverter so that the active component and the reactive component are decoupled and controlled separately.

5. A method for black start dispatching and controlling an energy storage power station considering SOC self-balancing as claimed in claim 3, characterized in that: In step 3, after the PQ energy storage group is connected to the AC common bus, the inverter is controlled by the control signal generated by the dual closed-loop control system of voltage and current, so that each PQ energy storage group acts as a micro power source to inject the active power and reactive power calculated in step 2 into the AC common bus.

6. A method for black start dispatching and controlling an energy storage power station considering SOC self-balancing according to claim 1, characterized in that: In step 402, the adjustment coefficient n is adjusted as needed according to specific engineering requirements, so as to change the output value of each PQ energy storage group when the SOC values ​​of the PQ energy storage groups are inconsistent, affecting the speed of balancing the SOC state of each PQ energy storage group.

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