Research And Application On Power Quality Control Strategy Of Electric Spring

As more and more renewable energy sources are connected into power grid, the fluctuating of renewable energy sources will result in fluctuation and flicker of grid voltage and harmonic pollution, and even make a threat to conventional power generation and lead to the breakdown of the power system. The stable operation of the power grid is facing severe challenges. With the development of power electronic technology, the usage of nonlinear load is increasing in the distribution system, the widely use of nonlinear loads leads to serious harmonic pollution. The voltage distortion will cause poor power quality, affect the safe and economic operation of the equipment, and increase the interference of the communication system. The extensive use of renewable energy and the nonlinear load will affect the power quality.In order to keep the power system stable, an electronic equipment "electric spring" is put forward. Electric spring can perform voltage regulation, harmonic compensation and power factor correction, to fulfill a new paradigm in the future smart grid. However,the existing power factor correction strategy of electric spring is proposed under the condition of ideal power grid, the strategy is not suitable for the power grid voltage which contains harmonic components, such as industrial electrical network with large number of rectifier devices and arc furnaces. In this paper, an optimal control strategy of power factor correction is proposed to realize the maximum power factor. To reduce the harmonic content of the power grid with a huge amount of nonlinear loads, a new control strategy is also proposed for the electric spring with nonlinear load, which can achieve voltage regulation, harmonic compensation and power factor correction simultaneously.The main work of this paper i is as follows:1. The voltage stabilization principle and control strategy of the electric spring are analyzed under the island mode and grid-connected mode.2. The power factor correction principle of electric spring under the ideal and distorted power grid are introduced, then a new control strategy with harmonic current loop is put forward, which can achieve the maximum power factor correction function under the distorted power grid.3. The compensation principle of electric spring with nonlinear load is analyzed, a control strategy is proposed for the electric spring with nonlinear load, which can achieve voltage regulation, harmonic compensation and power factor correction simultaneously.4. To verify the correctness of the theoretical analysis and control strategy, all of the above control strategies are verified by MATLAB/Simulink. Moreover, the experimentalplatform was also built to verify the effectiveness of proposed strategy.