Power Control Method for Composite Energy Storage Systems Utilizing Wavelet Analysis

Due to the stochastic, intermittent, and fluctuating nature of wind speed variations, power fluctuations occur in wind power generation systems. Energy storage technology plays a crucial complementary role in renewable energy generation by mitigating these fluctuations. This paper focuses on the study of short-term output power fluctuations in the system. Firstly, based on the principles of a first-order low-pass filtering algorithm, the paper calculates, analyzes, and discusses the smoothing effects of different cutoff frequencies on wind power, while meeting the goal of smoothing power fluctuations in wind power generation systems. The cutoff frequency of the first-order low-pass filtering algorithm is determined to be 0.3. Secondly, through comparative analysis of reconstruction errors, the paper determines that the wavelet decomposition level used is 6. Based on the power characteristics of energy storage components, signals of different fluctuation frequencies are allocated to lithium iron phosphate batteries and supercapacitors for smoothing via control of power electronic devices. Thirdly, the paper optimizes the power allocation method for compound energy storage systems, considering the state of charge, and employs a fuzzy PI control method to control the charging and discharging of the energy storage system. Compared to traditional PI control methods, the working state of the energy storage devices is more stable, with a decrease of 1.87% in SOC fluctuation for lithium iron phosphate batteries and a decrease of 0.64 % for supercapacitors. This protects the use of energy storage equipment, and simulation validates the feasibility of this method.