Research On Efficiency Optimization Of Asynchronous Motor Driven By Current Source

Motor is a kind of mechanical device to convert electric energy into mechanical energy.It is widely used in industry,agriculture,national defense and people's daily life.Asynchronous motor is the most widely used motor,in most cases,the asynchronous motor is working in light-load mode,which causes a waste of energy.Current source converter topology has the advantages of simple structure,reliable system,easy to realize four-quadrant operation,output current waveform close to sinusoidal wave,etc.It can be applied to fan,pump and compressor load,and these loads have a lot of energy-saving space.Therefore,it is of great significance to study the efficiency optimization of asynchronous motor driven by current source to save energy and restrain environmental pollution.Firstly,the main circuit topology of three-phase current-source converter is studied,and the low-frequency and high-frequency mathematical models of the three-phase current-mode converter in the three-phase stationary coordinate system are established.The generation and distribution of modulation signals in current-mode converters are studied,including the generation mechanism of ternary logic signals,zero-state discrimination,switching state distribution of power devices,etc.In order to meet the requirement of asynchronous motor speed control system for converter,the space vector control strategy of current source converter is determined.The simulation results show that the control strategy can achieve the unity-power factor of the grid side,the current ripple at the DC bus is small,and the output of the inverter is close to the sine wave.Secondly,dynamic mathematical models of asynchronous motor in two-phase stationary , coordinate system considering iron loss and ignoring iron loss are established respectively.At the same time,the vector control system of asynchronous motor driven by current source is simulated.The simulation results show that the output parameters of the motor can meet the control requirements.By studying the loss of asynchronous motor and power converter,the model expression of asynchronous electrical loss considering iron loss is established.Based on the loss model and the Golden Section method,the efficiency optimization strategy is studied,and the improved Golden Section method is proposed.Through simulation comparison,it can be concluded that the efficiency optimization control strategy based on the improved golden section method can achieve the advantages of fast optimization speed,global optimization,small torque ripple,and it is an effective efficiency optimization control algorithm.According to the theoretical analysis,the hardware circuit of the asynchronous motor control system driven by the current source with the core of TMS320F28335 DSP is built,including DSP control circuit,power supply circuit,main circuit and sampling circuit.The relevant software design and experimental verification are carried out.The results verify the feasibility of the research scheme.At the end of the paper,the conclusions and future directions for improvement and research are summarized.