Current Control of Electrolytic Capacitor-Less Variable Frequency Drive System for Synchronous Reluctance Motors Based on Power Balancing and Compensation

The electrolytic capacitor-less variable frequency drive scheme using film capacitors to replace electrolytic capacitors has been partially applied in the field of washing machines and air conditioners driven by permanent magnet synchronous motors, due to its advantages of good reliability and low cost. However, recently, with the development and application of synchronous reluctance motors to replace permanent magnet synchronous motors, the existing methods have problems such as id = 0 control unsuitable for synchronous reluctance motors, low power factor on the input side, and poor motor running performance and other problems. Therefore, firstly, this paper takes the variable frequency drive system for the synchronous reluctance motors as the research object, analyses the influence of the value of the bus capacitance on the performance of the variable frequency drive system, and provides a theoretical basis for the selection of bus capacitance. Secondly, a current control strategy based on power balance and compensation is proposed, which includes current feeding based on power balance, input voltage phase detection based on a phase-locked loop, and output voltage vector regulation based on power compensation. To verify the correctness of the proposed method, a platform was built and tested, and the experimental results show that the electrolytic capacitor-less variable frequency drive system for synchronous reluctance motors using the method proposed in this paper not only improves the power factor at the input side of the drive system but also reduces the fluctuation of the motor speed and torque, which in turn improves the operating performance of the motor.