With the rapid growth of installed capacity of photovoltaic (PV), the PV power stations equipped with energy storage (ES) have become a new type of black-start power supply. Taking the Photovoltaic-Battery Energy Storage Systems (PV-BESS) as the black-start power source can improve the black-start ability of the regional power grid and broaden the application prospect of PV power generation. In this paper, a stratified optimization strategy for black-start of PV-BESS is proposed, which combines the key issues in the process of black-start of PV-BESS. Stratified optimization strategy is divided into data analysis layer, optimization coordination layer and scheduling control layer. The data analysis layer combines the requirements of the black-start process. Firstly, the similarity matrix ranking method is used to improve the PV power prediction method. Secondly, based on probability inclination, the PV power index is designed to evaluate the feasibility of black-start by calculating the PV lower limit power and the executable probability inclination. The optimization coordination layer is based on the state space model of black-start of PV-BESS, combined with the control strategy of PV as the main part and ES as the auxiliary part, the optimization objectives of the maximum utilization rate of PV and tracking the ideal value of state of charge (SOC) of ES is formulated. The optimal model is solved by model predictive control, and the output power of PV and ES is controlled to complete the black-start process. The actual historical data in the power grid with a high proportion of PV sources are used as the basic data for simulation. The simulation of black-start based on MATLAB/Simulink verifies the rationality of the stratified optimization strategy, which provides a reference for the realization of black-start of PV-BESS.

With the increasing participation of wind generation in the power system, a wind power plant (WPP) with an energy storage system (ESS) has become one of the options available for a black-start power source. In this article, a method for the energy storage configuration used for black-start is proposed. First, the energy storage capacity for starting a single turbine was determined. Then, a hierarchical planning model was established. This model did not consider the starting efficiency of the WPP, but it did consider the layout of the energy storage in the WPP and the balance of the terminal voltage when starting the WPP. Finally, the feasibility and value of the proposed method and model were verified in a 49.5 MW WPP with an ESS (a power rating of 2.24 MW and energy capacity of about 1.68 MWh). The result suggests that configuring an ESS with a small capacity on the side of the turbine can achieve black-start for a WPP with an ESS as the power source.

Wind curtailment of power grid is severe during heating period in the `Three North'(northwest china, north china, and northeast china) area of China, and the `wind-heat conflict' causes insufficient of power system peaking, which is one of the main reasons that impacts wind power consumption. To enhancing flexibility of power system by configuring flexible load is an effective means to improving wind power acceptance. This paper, based on the dispatch of the cogeneration unit, analyzed the composition and operation rules of battery energy storage-heat storage system. Considering the constraints of power system and thermal system, the coordinative dispatching model of battery energy storage and regenerative electric boiler is established. Based on a regional power grid in the `Three North' area of China is used to simulate the acceptance of wind power under different modes of operation. The results show that in the way of power alternative, the regenerative electric boiler has the best effect of eliminating wind and abandoning wind, and the environmental benefits are obvious. When the thermal storage electric boiler is matched with an excessively large new adding heat load, the thermal power unit in the electric power for heating accounts for a relatively high amount of electricity, and the efficiency of energy utilization is low. Considering the battery storage price is greatly reduced, the peak shaving effect of battery energy storage and thermal storage electric boiler coordinated operation is the most obvious, and it is of great significance for the safe and stable operation of wind power and high-wind power infiltration grid.

Large scale wind power integration has a negative influence on the frequency response. Assistant measurement improves the frequency stability of power systems under high wind penetration. The Proportional Curtailment Strategy (PCS) for wind turbines provides a primary frequency reserve for power systems. To solve the worthless curtailed wind power, the PCS is used to improve the utilization of wind power curtailment. Then the wind turbine and the lithium battery Energy Storage System (ESS) provide primary frequency reserves together. Different control strategies of ESS have been proposed based on the different methods for selecting valid reserves. The economic benefits of different control strategies have been compared based on the same frequency regulation reserve. The optimal control strategy is the maximum method. The economic benefit of the maximum value method is ¥4,445,300.

Modeling and state of charge (SOC) estimation of Lithium cells are crucial techniques of the lithium battery management system. The modeling is extremely complicated as the operating status of lithium battery is affected by temperature, current, cycle number, discharge depth and other factors. This paper studies the modeling of lithium iron phosphate battery based on the Thevenin’s equivalent circuit and a method to identify the open circuit voltage, resistance and capacitance in the model is proposed. To improve the accuracy of the lithium battery model, a capacity estimation algorithm considering the capacity loss during the battery’s life cycle. In addition, this paper solves the SOC estimation issue of the lithium battery caused by the uncertain noise using the extended Kalman filtering (EKF) algorithm. A simulation model of actual lithium batteries is designed in Matlab/Simulink and the simulation results verify the accuracy of the model under different operating modes.