Grid-Connected Modeling and Dynamic Characteristics Analysis of Gravity Energy Storage System Based on Permanent Magnet Synchronous Generator-Motor

In this paper, a modeling and simulation method of grid-connected system including gravity energy storage mechanical part, permanent magnet synchronous motor and back-to-back converter is proposed. Firstly, based on the principle of gravitational potential energy and electric energy conversion, the energy flow model and power model of gravity energy storage system are constructed to quantify the energy loss and power dynamic characteristics under charging and discharging conditions. Furthermore, the mathematical model of permanent magnet synchronous motor in d-q coordinate system is established, and the zero d-axis current control scheme is designed for the machine-side converter, and the vector control scheme based on grid voltage orientation is designed for the grid-side converter, so as to achieve accurate regulation of motor torque and stable transmission of grid-connected power. Finally, the simulation model of gravity energy storage grid-connected system is built by using MATLAB/SIMULINK platform, and the dynamic performance under different working conditions is analyzed. The results show that the output power of the gravity energy storage is accurately matched with the grid-connected power, the dc side voltage fluctuation is small, the grid-connected voltage and current waveform has high sinusoidality and low harmonic content, and the motor speed and torque response are fast and stable. The research results can provide technical reference for the engineering application of gravity energy storage grid-connected system.