Research On Voltage Fluctuation Control Based On Three Port Flexible Multi-State Switch

The widespread using of electrical energy has led to a large number of power quality problems,especially the voltage fluctuations due to sharp increasing in non-linear loads.For large-area scattered factory load and residential load,single-ended voltage fluctuation control equipment can not meet the requirements.Flexible multi-state switch(FMSS)is a recent research hotspot.It can achieve mutual currents and dynamically and efficiently suppress voltage fluctuations in multiple ports.Therefore,this paper studies the performance of voltage fluctuations based on three-port FMSS.The specific research contents are as follows:Taking the three-port FMSS of back-to-back structure as the research object,the mathematical model is analyzed under the synchronous rotating dq coordinate system.Based on the power exchange principle between three-port FMSS and three-sided AC system,the double closed-loop control strategy is given to realize multiple control objectives.The outer loop control technology of "PI + steady state inverse model" is used to solve the nonlinear coupling problem of the mathematical model.The inner loop control technology of voltage feed-forward and current feedback is used to solve the problem of current coupling and grid voltage disturbance.The three-port FMSS model is built by Matlab/Simulink software.By control the power flow between FMSS and AC system,the study verified the correctness of the model as well as the feasibility of control strategies.According to the voltage fluctuation compensation control principle in distribution network,the suppression effect of voltage fluctuation and the effectiveness of voltage regulation strategy are analyzed under two different working conditions.The three-port FMSS has different working modes.Under different users,the optimal mode is obtained by comparing the magnitude voltage fluctuation of the PCC point.A distribution network voltage optimization model is established with three-port FMSS.Taking full account of security,the model takes the minimum sum of the node voltage deviations as the objective function.The above model is solved by using DNLP solver on GAMS platform.The voltage distributions of IEEE14 and IEEE33 test system are optimized to improve the overall voltage fluctuation of distribution network.