Research On Model Predictive Control And New Structure For Dynamic Voltage Restorer

Grid voltage swells or sags easily result in sensitive load faults. Dynamic Voltage Restorer(DVR) generates compensation voltage to stabilize loads at nominal voltage, which is an effective and economical method to improve voltage quality dynamically in power distribution network. Model predictive control strategy and novel structure of DVR is studied in this paper.Firstly, the basic working principle, circuit structure and compensation voltage detection of DVR is illustrated. By comparing the advantages and disadvantes of different detection strategies, the method of instantaneous reactive power theory dq conversion is selected. The simulation of voltage sags or swells with different ranges and harmonics is established to provide correct compensation voltage reference value for control part of DVR.Secondly, the model predictive voltage control strategy based on traditional DVR is designed. According to establish the predictive function in dq coordinate system, the switch status which makes the cost function minimum is selected out to trace the compensation voltage reference value. Thus, rolling optimization is formed to realize the real-time load voltage compensation. Compared with feedforward decoupling PI control strategy, simulation validates that model predictive voltage control strategy can improve dynamic response speed and steady-state accuracy of DVR without adjusting parameters repeatedly.Finally, improved DC energy storageless direct AC/AC power DVR is proposed. Compared to traditional DVR based on voltage source inverter, this novel restorer does not use energy storage devices, which is low cost and easy to maintain. Non-complementary control commutation strategy and predictive control method are designed. By using a discret state observer, the control signals have been obtained by predicting the system state and performing its algorithm in previous cycle, which saves the algorithm execution time compared with existing instantaneous voltage control. Experiment results based on experimental prototype verifies the validity of the proposed plan.