Conference Agenda

This paper attempts to overview the application of multi-objective optimization (MOO) in the design of passive electromagnetic interference (EMI) filters. MOO is gaining popularity due to efficient nature-inspired metaheuristics and surrogate modeling techniques, enabling the solution of complex optimization problems spanning across multiple engineering disciplines. The development of EMI filters for power electronics is typically such a task, for which MOO workflows are identified based on the existing literature, and an MOO problem solution is demonstrated on an example, aiming to aid the practical utilization of the technique.

Most active filters for electromagnetic compatibility (EMC) are designed as Single-Input Single-Output (SISO) systems. This work proposes an innovative approach with a control strategy for a Two-Inputs Two-Outputs (TITO) active filter. This model employs two detection points and two injection points, optimizing noise attenuation on power lines. Integrated into the regulation loop, it allows precise control of line currents without relying on the traditional separation of modes (common mode and differential mode), while inherently accounting for mode conversion phenomena. This approach offers a different method for active filter design.

This paper investigates the closed-loop input impedance of the PFC system and the effect of low-frequency zero-crossing phase-lead compensation methods on resonances of PFC input impedance in the supra-harmonics frequency range. An input voltage feedforward active damping approach is further proposed in this paper to actively attenuate the resonance peaks and dips of the PFC input impedance caused by system high quality factor components and the interaction between the converter and the EMI filter. The proposed active damping provides low-frequency zero-crossing phase lead compensation and supra-harmonics frequency range resonance attenuation, which applies to PFC systems with any EMI filters as long as the resonance frequency falls within the converter control bandwidth. Comparative simulation results of real cases show that the proposed active damping can effectively attenuate resonances of PFC input impedance with different types of EMI filters by 9-15 dB, largely reducing potential EMI emission amplification and system stability issues.

The common mode EMI of power electronic systems can often be seen as a sequence of short, periodic disturbance pulses caused by the switching actions of the power transistors. To reduce passive filter components, these individual pulses can be suppressed by injecting appropriate cancellation signals with active EMI filters. By using digitally synthesized cancellation pulses generated by an FPGA with a digital-analog converter (DAC), high EMI suppression can be achieved. These cancellation pulses can be generated with an adaptive finite impulse response (FIR) filter, which takes the PWM signals of the system as input and recreates step responses as fitting cancellation pulses. When asymmetric disturbance pulses occur, multiple FIR filters must be used, as the turn-on transient might cause different waveforms than the turn-off of the same transistor. This paper presents a possible implementation for multiple filters. Additionally, the FIR filter is substituted by another signal generation technique using other storage options available on the FPGA, saving valuable FPGA resources and allowing for much longer cancellation pulses. For demonstration, the extended algorithm is applied to the common mode EMI of a DC-DC converter showing long and asymmetric disturbance pulses. The EMI suppression is evaluated in the test setup with an EMI test receiver, showing high broadband EMI suppression in the considered frequency range of 150 kHz to 30 MHz.