Study On Closed-loop Control Of Matrix Converter With Self-tuning Fuzzy PID Strategy

Matrix converter(MC), is a new structure of direct AC-AC power converter, with many advantages of:1) sinusoidal input current/output voltage, few harmonics;2) without intermediate DC link, small in size, quickly dynamic response, power densities;3) energy could flow in both directions;4) The output voltage amplitude, frequency, and power factor of network side can be controlled independently,5)the commutation and invertion can be achieved through different control law. MC have great practical application value in the field of variable voltage and variable frequency and variable-speed constant-frequency wind-power generation.The basic structure, working principle and communication problem of Matrix converter were analyzed. The simulation platform of line-to-line voltages synthesis strategy and indirect space vector strategy have been constructed. Both line-to-line voltages synthesis strategy under four unbalance conditions and indirect space vector strategy under input balance and distortion were simulated and analyzed to convert the frenquency from10Hz to25Hz, the line-to-line voltages synthesis strategy was verified to have stronger anti jamming ability.Based on the simulation platform of indirect space vector strategy, a novel closed-loop controller based on modified fuzzy PID control is proposed to improving the output stability of matrix converter(MC) under load unbalance. The output line voltage of MC is converted into two direct current components under the d-q axis by Park transformation. These two components are controlled to track the d, q components of reference voltage by the modified fuzzy PID controller. The correction function is an index function with the errors and their derivative as arguments, and its parameters are reasonably adjusted through the variation law of errors. The coordinating factor which change the output weights between the fuzzy controller and PID controller is adopted and the linear interpolating algorithm is proposed to eliminate the stable state error of system and enhance the control precision of fuzzy controller. Simulation results show that the strategy can improve the control quality of the system and let the MC have good dynamic and static performance.The laboratory has produced a prototype of a matrix converter whose power was5kw. The hardware of the overall structure, main circuit, control circuit etc. of matrix converter are analyzed. The software programming of indirect space vector strategy and experiments are carried out, the experimental results are presented to verify the validity and correctness of the matrix converter design.