The Study Of Coordinated Control Strategy Of Dual PWM Based Improved Load Power Feedforward

Because the dual PWM converter has advantages of small grid current harmonic,adjustable dc bus voltage,unit power factor closely,bi-directional flow of energy,so it is gradually replacing the converter of diode uncontrolled rectifier and half controlled thyristor rectifier.The dual PWM converter includes rectifier and inverter side,the core is the rectifier side.In numerous rectifer control algorithms,DPC is one of the most effective control algorithms.The switching table adopted in traditional DPC has its limitations,so using a new swiching table to decrease instantaneous reactive power fluctuation and frequency of switching devices.The strategies of variable frequency speed control system of dual PWM can be devided into independent control strategy and coordinated control strategy.Compared with independent control strategy,coordinated control strategy can enhance disturbance-resistant performance and robustness of the system.However,it also has limitations.For example,when the motor transforms status from forward electric state to forward braking state,energy realises reverse flow and load changes seriously.So dc bus voltage will have larger fluctuation and the steady state error is larger than it was before the load mutation,and the overshoot is also bigger.For the shortcomings of traditional load power feedforward,a method of variable PI parameter is proposed,which is combined with traditional load power feedforward.Finally,Making up improved load power feedforward.Compared with the pute load power feedforward,the disturbance-resistant performance and adaptability are imprvoed.The dynamic and steady state characteristics are also further modified,which has important practical significance to reduce volume and costs of the capacitor.Finally,though Matlab/Simulink,the result shows good effectiveness and practicability of this method.Finally,using this improved load power feedforward control method in servo control system of the permanent magnet synchronous motor and controlled rectifier instead uncontrolled rectifier,realizing rapid and accurate positioning of the motor.At the same time,the dynamic and static characteristic of dc bus voltage are improved.