Variable Frequency Drive System Based On Single-stage Boost Inverter

With the popularity of various household appliances,the problems of energy supply and environmental issues are aggravated tremendously.A large number of researches indicate that the employment of variable frequency driving scheme has great potential in energy saving,which will obviously improves the energy efficiency of household appliances such as refrigerators,air conditioners and washing machines.In the traditional variable frequency driving system,the DC bus capacitor is usually the electrolytic capacitor of hundreds or thousands microfarad to maintain the stability of DC bus voltage.However,the used large electrolytic capacitor reduces the lifetime of system,results in the low input power factor and causes the hidden shoot-through problem.Based on the above-mentioned problems,this paper studies and designs a variable frequency driving system based on single-stage boost inverter.This paper analyzes the operating principle of the single-stage boost inverter and the traditional six distributed shoot-through modulation strategy,on the basis of these analyses,a hybrid six distributed shoot-through modulation strategy is proposed.Taking quasi Z-source inverter as an example,the effects of different shoot-through modes on the inductor current ripple and the voltage stress of switches are analyzed.According to the adopted shoot-through control strategy,the parameters of the passive network are designed to determine the inductance and capacitance.In the meantime,the losses of the inverter are analyzed and the superiority of the hybrid six distributed shoot-through modulation strategy is verified by the experiment.In addition,the research on the current situation of variable frequency driving technology without electrolytic capacitors are conducted in this paper.On the basis of the traditional variable frequency driving system,the problem of the lifetime of system and bridge arm straight-through is solved fundamentally by replacing the electrolytic capacitor with the passive network on the rectified output side.By raising the bus voltage,the expansion of the frequency range of the motor and the improvement of efficiency are achieved,while also allowing the system to withstand deep grid voltage drops.The control strategy of input current for single-stage boost variable frequency driving system is analyzed in order to improve the input power factor.Besides,simulations are carried out to verify the correctness of the proposed system scheme.Finally,a prototype of single-stage boost variable frequency driving system is designed and established,including voltage and current sampling module,opto-isolator driving module and motorspeed sampling module.The system is controlled by digital control technology and the experimental results verify the effectiveness and feasibility of the proposed system and control strategy.