Research On The Strategy Of Suppressing The Double Frequency Ripple In DC Side Of Single-Phase Voltage Source PWM Rectifier

The single-phase voltage source PWM rectifier has been widely used in a variety of power occasions because of its characteristics of bidirectional energy flow and unit power factor.However,in order to suppress the double frequency pulsation of the DC voltage,a large capacitance capacitor needs to be connected in parallel to both ends of the DC bus for voltage stabilization,which increases the volume and cost of the system and also affects the overall service life of the converter.Therefore,suppressing the double-frequency pulsation of the DC voltage while reducing the size of the energy storage capacitor has important practical significance for the development of the miniaturization of the rectifier and the improvement of the system life.This paper first analyzes the working principle of the rectifier under the unipolar modulation mode,establishes the mathematical model of the rectifier,and designs the double closed-loop control structure based on the model.After that,the reason for the generation of pulsating power is analyzed,and the decoupling circuit is connected in parallel on the DC side to absorb the pulsating power.The buck-boost mode of the power decoupling circuit and the principle of suppressing the double frequency pulsation of the DC voltage are explained in depth,then a simple,universal control strategy is proposed for the decoupling circuit.Compared with other control schemes,this control strategy does not require the use of redundant voltage and current sensors,and the control of the front and rear stages of the circuit does not affect each other to achieve decoupling,and then the decoupling circuit is controlled to achieve the purpose of pulsating power transfer and restraining the large fluctuation of DC voltage.At the same time,based on the control strategy proposed in this paper,the mathematical relationship between the decoupling capacitance and the parameters is derived in detail when the decoupling circuit works in the buck-boost mode and the expression of the decoupling capacitance is obtained.The decoupling principle of the control strategy is explained in the mathematical analysis.According to the calculated parameters,the scheme of suppressing the DC voltage double frequency pulsation and the control strategy of the decoupling circuit in this paper are simulated and verified respectively in the scenarios of low power and high power.Finally,this paper builds an experimental prototype based on the designed parameters.Then the effectiveness and feasibility of the scheme used in this paper for suppressing the double-frequency ripple of the DC voltage and reducing the capacitance value of the capacitor are verified through experiments.