Double PWM coordinated control based on energy mathematic model

Based on double PWM structure, this paper analyzes the energy relationship between each part of the system according to the system energy flow in balanced energy state and unbalanced energy state and builds the energy mathematic model of double PWM. In order to solve the problems of DC bus voltage fluctuation and the mismatch in system output power and the motor power caused by the imbalance between system output energy and dissipated energy, the constraints of DC bus voltage fluctuation and grid-side current component in the d axis are added to ensure the system energy a smooth variance. Using constraints to correct outer voltage loop and inter loop power, the output energy of rectifier side can fastly match the loss energy of inverter side. So the double PWM structure can ensure coordinated control of each part of the system. According to the results of simulation, the system can realize the fast balance in system energy and reduce DC bus voltage fluctuation when the power of load motor suddenly varies. This method also can reduce the harmonic current and capacity of the DC side capacitors.