Research On Energy Storage Converter Based On Flexible Battery Group Technology

In recent years, the proportion of new energy source generation, such as wind power and solar energy, rises gradually in the power system of China. For the intermittency and volatility of the new energy power generation, the new energy power generation connected to power system has adverse effects on the grid. Lithium-ion battery energy storage system is able to smooth power fluctuations due to intermittent power, and improve the optimal allocation of energy resources for grid. Energy storage system has become a focus research topic in the field of electric power. Based on the traditional problems that exist in the lithium-ion battery energy storage system, detailed research was carried out about energy storage converter based on flexible battery grouping technology.Firstly, the paper analyzes the reasons caused by the inconsistency of battery pack, and its adverse effects on the capacity, energy utilization and power output of battery pack, and the measures to improve traditional battery inconsistency in the process of traditional battery group. Then focuses on the problems in process of conventional battery group usage, combined with the power electronic technology, the concept of battery flexible group is put forward. The characteristics of flexible battery group technology are analyzed. Expressions of available energy are theoretical derivation for the flexible battery group mode and the traditional battery group mode. Actual data of a passenger car’s battery group was analyzed. Analyze data verify the battery flexible group technology better than traditional battery group technology in battery available energy. This article introduces the structure of the flexible group battery energy storage system, and analyzes different converter topologies applied to battery flexible group.Secondly, the paper studies the control strategies of energy storage converter based on the flexible battery group technology. It introduces the working principle of cascade H bridge converter and its modulation strategy. From the point of view of system, it analyzes grid control strategy, and charge and discharge current independent control strategy with the goal of module current independent control. To solve the imbalance problems of three-phase battery power caused by the battery module current independent control, it analyzes the power balance control strategy when three-phase battery power present imbalanced. Then, it constructs the simulation model of the converter, and carries on the simulation and waveform analysis of the control strategy.Thirdly, an energy storage converter based on the battery flexible group technology is designed. Then, hardware design of main circuit, and hardware and software design of circuit control are introduced.Finally, Experiments are implemented on the storage energy converter to verify the control method, and the experimental waveforms are analyzed.