An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter(TSI),the second harmonic current(SHC)is generated in the frontend dc-dc converter(FDC).To reduce the SHC,optimizing the control strategy of the FDC is an effective and costless approach.Fromthe view of visual impedance,this paper conducts an intensive study on the SHC reduction strategies.Origin of the SHC is illustrated first.Then,the equivalent circuit models of the FDC under different control strategies are proposed to analyse the SHC propagation characteristic.The derived model can offer a better insight into how the inductor SHC is affected by the control parameters.According to the derived models,a synthesis of different control strategies is presented and the relevant parameters are listed for control design to achieve better suppression effect.The benefits and limitations of these control strategies are also discussed.Based on the proposed equivalent circuit models,several optimization methods are proposed to enhance the effect.A 1500 VA TSI prototype is built and simulated on MATLAB/Simulink,verifying the effectiveness of the proposed optimization methods.This paper is aimed to provide a guideline for the control design and control optimization of the TSIs.

Effect of Battery on Moving Properties of Cableless In-Piping Magnetic Actuator

This paper proposes a cableless in-piping magnetic actuator that exhibits a very high-speed locomotion into inner pipe of 8 mm. The cableless magnetic actuator is moved according to the vibration amplitude and resonance energy of a mass-spring system excited by using an electromagnetic force. The iron core size of the bobbin type electromagnet was roughly designed by computer simulation and then optimized experimentally. The proposed actuator incorporates an electrical inverter that directly transforms DC from button batteries into AC. The electrical DC-AC inverter incorporates a mass-spring system, a reed switch and a curved permanent magnet that switch under an electromagnetic force. The duty ratio is changed into this electrical inverter by changing the position of the curved magnet and the reed switch. Experimental result demonstrates that the cableless magnetic actuator was able to move horizontally at 471 m, and horizontal speed at 327 mm/s when Maxell SR621W silver-oxide button batteries were used.