Hierarchical Coordination Frequency Control Strategy of Battery Energy Storage/Gas Turbine under Off-Grid State
Liu Xiaolong1,2, Li Xinran2, Meng Ya2, Chen Changqing2, Yang Yang2
1. College of Electrical and Information Engineering Hunan Institute of Engineering Xiangtan 411104 China; 2. College of Electrical and Information Engineering Hunan University Changsha 410082 China
Abstract：The micro-grid contains a large number of power electronic devices, and the random output of renewable energy makes the frequency stability control under the independent operation of micro-grid more challenging. In the current research work, the frequency stability of the micro-grid system is effectively improved by using battery energy storage as an auxiliary frequency modulation control unit. However, the energy is very limited when off grid, and the battery energy storage needs to be used as a power support unit to supply power for part of the load. Auxiliary frequency modulation using battery energy storage may cause its state of charge (SOC) to deviate from the planned value, affecting normal power supply. On the other hand, during the control process, the output of battery energy storage and synchronous generator (gas engine, diesel engine, etc.) is adjusted according to the frequency deviation of the system, which is relatively passive. Based on the above analysis, taking the photovoltaic / battery energy storage / gas turbine micro-grid under the master-slave control mode as the research background, taking the battery energy storage and gas turbine as the main control units, the corresponding frequency control strategies are proposed. (1) Taking gas turbine as the main control unit, a hierarchical coordinated frequency control strategy for gas turbine/battery energy storage based on model predictive control(MPC) and low-pass filtering(LPF) algorithm is proposed. In the upper minute level control, the model predictive control is used to continuously adjust the power output plan with the goal of minimizing the battery energy storage SOC and the power output change, reducing the source load power deviation. At the same time, the low pass filtering algorithm is used to divide the frequency, so that the gas turbine can bear the low-frequency disturbance component to avoid the frequency fluctuation caused by the slow response speed of the gas turbine; In the bottom second level control, based on the upper level output benchmark, the battery energy storage output is dynamically adjusted through virtual droop/inertia control and SOC self recovery control, and the gas turbine is jointly involved in frequency modulation to further suppress the system frequency fluctuation. Simulation analysis shows that the proposed method can not only effectively reduce the frequency fluctuation of the system, but also well follow the battery energy storage SOC plan curve, thus ensuring that the off grid system can continue to operate stably according to the energy supply plan. (2) Taking battery energy storage as the main control unit, a gas turbine/battery energy storage coordinated control strategy based on model predictive control and low-pass filtering algorithm is proposed. The upper minute level control is the same as part (1). Through model predictive control and low-pass filtering algorithm, the power output plan is continuously adjusted in a rolling manner to reduce the source load power deviation. In the bottom second level control, it mainly depends on the main battery energy storage to quickly stabilize the unplanned fluctuations and ensure the frequency stability of the off grid system. Simulation analysis shows that the proposed method can not only keep the main battery energy storage SOC in the best state as far as possible, but also ensure that the system can run stably for a long time; In addition, the gas turbine can be kept in a stable operating state as far as possible to avoid frequent reciprocating action to damage the equipment.
刘小龙, 李欣然, 孟娅, 陈常青, 杨徉. 离网状态储能/燃气机分层协调频率控制策略[J]. 电工技术学报, 2023, 38(17): 4800-4810.
Liu Xiaolong, Li Xinran, Meng Ya, Chen Changqing, Yang Yang. Hierarchical Coordination Frequency Control Strategy of Battery Energy Storage/Gas Turbine under Off-Grid State. Transactions of China Electrotechnical Society, 2023, 38(17): 4800-4810.
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2023, Vol. 38 
