Abstract
Problem statement: In switched mode PWM inverter EMI noise occurs during high (dv/dt) transient period. This EMI noise is mitigated using Active Common mode EMI filter in front of the source. Approach: This study proposes a new active common mode Electromagnetic Interference (EMI) filter for switched mode PWM Inverter applications. The proposed filter is based on current sensing and compensation circuit which utilizes fast transistor amplifier for current compensation. The amplifier is biased with an isolated low voltage DC power supply. Hence it is possible to construct an active filter independent of the source voltage of equipment. Thus this filter can be used in any application regardless of working voltage. The proposed switched mode PWM inverter operated in 180° mode of operation. It’s otherwise called as quasi square wave mode. Results: Simulation of output wave form is verified by using MATLAB Simulink model results and also its effectiveness has been verified hardware output wave forms. The hardware for this project is designed and developed for 50V, 50Hz three phase Fractional Horse Power (FHP) motor. Conclusion: In this Study the concept of the new active common mode EMI filter and quasi square PWM inverter has been proposed. The corresponding simulated output waveforms are verified with the Active Common mode EMI filter; it is possible to use low-voltage transistors for the amplifier by introducing coupling capacitors between the power line and the amplifier circuit. Thus the ACEF can be applied to various power electronic systems regardless of the working voltage. Also it helps in improving the performance of additional filter stages.
Highlights
Switched-mode DC to AC Inverters are used in AC motor drives and uninterruptible AC power supply where the objective is to produce AC output whose magnitude and frequency can both be controlled
Switched Mode PWM inverter noise: Rapid change in voltage and current of a switching power converter Electromagnetic Interference (EMI) is in two forms: Radiated and conducted
Because both the conducted EMIs come from the same energy source and energy is dissipated somewhere, blocking the conducted EMI can often lead to increase in radiation. (Rao et al, 2011) an effective EMI suppression strategy has to be made on a thorough understanding of the EMI mechanism, so that EMI will be reduced at the source instead only being blocked after it is generated
Summary
Switched-mode DC to AC Inverters are used in AC motor drives and uninterruptible AC power supply where the objective is to produce AC output whose magnitude and frequency can both be controlled. The PWM Inverter is inherent noise source that makes abrupt voltage transitions (high dv/dt) companied by switching actions (Skibinski et al, 1999; Karthikeyan and Duraiswamy, 2011). It is coupled with the stray capacitance of the load machine the high frequency current is generated, which affects the operation of nearby equipment due to the conducted and radiated EMI. Proposed filter is a New Active Common mode Electromagnetic Interference Filter (ACEF) In this filter Inductance (L) only is varied while capacitance is kept constant.
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