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In this paper, a general lumped circuit modeling method is proposed to describe the conducted electromagnetic interference (EMI) coupling mechanism for the switching power converters. The EMI characteristics of the converters can be analytically deduced from a circuit theoretical viewpoint. The shunt and series impedance insertion method is introduced to identify the differential-mode (DM) and common-mode (CM) noise impedances and voltage sources. The procedure of parameters estimation for the noise models comprises several simple measurements and is convenient to be implemented. Experimental illustrations are also included to verify the validity of the proposed method. Comparison between the measured and predicted results shows that the EMI modeling method can provide adequate prediction of the EMI feature for power-switching converters. Index Terms--Conducted electromagnetic interference (EMI), lumped circuit models, noise sources and impedances, power-switching converters.

Recently, there has been an increase in the application of fuzzy logic controllers (FLCs) for control of power electronic converters. Due to the FLCs' complex algorithm, their realization often calls for a compromise between cost and performance. In this paper, it is shown that the rule table of most of the two-input FLCs used with power converters can be approximated into a single nonlinearity. This allows the controller to be easily realized using simple, fast, and inexpensive analog circuits. The simplified 'nonlinear function controller (NLFC)' developed in this manner is shown to be equivalent in performance to the original FLC through simulations. The NLFC concept is then applied to PI-FLC, a type of FLC popular in power converter control applications. This results in the PI-FLC being replaced by a simple 'nonlinear PI controller (NPIC).' Using this simplification, the design of NPICs to obtain good dynamic performance in power converters is explained. An example design of NPIC for controlling a dc-dc boost power converter is presented. Experimental results are also presented to demonstrate the superior dynamic performance of the converter with NPIC versus that of a linear-PI controller. Index Terms--Dynamic response, fuzzy control, fuzzy logic, pulsewidth-modulated (PWM) power converters, switched-mode power supplies, Topelitz matrices.

This paper proposes a design criterion for calculating the resonant auxiliary elements of zero-voltage transition dc-dc pulsewidth-modulated (PWM) converters that use a dc auxiliary voltage source. The proposed criterion is based on stored energy in resonant auxiliary elements and takes into account the influence of the auxiliary voltage source value. Using this criterion, the reactive energy can be kept at a minimum level and a reduction of the auxiliary elements current ratings is achieved, which leads to lower conduction losses and improved converter efficiency. In addition, a reduction in size of auxiliary magnetic elements can be accomplished. To illustrate the usefulness of the proposed design criterion, the paper compares results obtained from the True-PWM Zero-Voltage Switching pole boost converter designed according to the proposed criterion, and from the original design guidelines. Experimental results show an efficiency gain of about 1% for a wide load range and 1.5% at full load. In addition, a reduction of about 52% in the auxiliary transformer volume for the implemented prototype was achieved, ensuring a reduction in overall converter size. Experimental results were obtained using a 1-kW 100-kHz laboratory prototype. Index Terms--DC-DC power conversion, pulsewidth-modulated (PWM) power converters, switching circuits.

This paper deals with the design of the output impedance of uninterruptible power system (UPS) inverters with parallel-connection capability. In order to avoid the need for any communication among modules, the power-sharing control loops are based on the P/Q droop method. Since in these systems the power-sharing accuracy is highly sensitive to the inverters output impedance, novel control loops to achieve both stable output impedance and proper power balance are proposed. In this sense, a novel wireless controller is designed by using three nested loops: 1) the inner loop is performed by using feedback linearization control techniques, providing a good quality output voltage waveform; 2) the intermediate loop enforces the output impedance of the inverter, achieving good harmonic power sharing while maintaining low output voltage total harmonic distortion; and 3) the outer loop calculates the output active and reactive powers and adjusts the output impedance value and the output voltage frequency during the load transients, obtaining excellent power sharing without deviations in either the frequency or the amplitude of the output voltage. Simulation and experimental results are reported from a parallel-connected UPS system sharing linear and nonlinear loads. Index Terms--DC-AC power conversion, pulsewidth-modulated (PWM) inverters, uninterruptible power systems (UPSs).

A review of high-performance, state-of-the-art, active power-factor-correction (PFC) techniques for high-power, single-phase applications is presented. The merits and limitations of several PFC techniques that are used in today's network-server and telecom power supplies to maximize their conversion efficiencies are discussed. These techniques include various zero-voltage-switching and zero-current-switching, active-snubber approaches employed to reduce reverse-recovery-related switching losses, as well as techniques for the minimization of the conduction losses. Finally, the effect of recent advancements in semiconductor technology, primarily silicon-carbide technology, on the performance and design considerations of PFC converters is discussed. Index Terms--Boost converter, constant frequency, continuous conduction mode (CCM), power-factor correction (PFC), zero-current switching (ZCS), zero-voltage switching (ZVS).

This paper proposes a new three-phase single-stage power-factor corrector buck-boost-type rectifier topology. The typical topology uses a bridge configuration with six switches. This new topology only requires four switches, improving the rectifier efficiency as only one reverse-blocking power semiconductor conducts at any time. A vector-based sliding-mode control method for the three-phase input currents is also proposed. This fast and robust technique uses sliding mode to generate [alpha][beta] space-vector modulation, which forces the input line currents to track a suitable sinusoidal reference. A near-unity power-factor operation of the rectifier is obtained using a sinusoidal reference in phase with the input source voltages. A proportional-integral controller is adopted to regulate the output voltage of the converter. This external voltage controller modulates the amplitude of the current references. The characteristics of the new rectifier are verified with experimental results. Index Terms--AC-DC power converters, harmonic distortion, power-factor correction, proportional-integral (PI) controller, vectorial sliding-mode approach.

A new control strategy has been developed for interfacing a neutral-point-clamped active rectifier with the mains. In particular, a method, based on the modulation of the input currents amplitudes, is proposed to compensate the dc-link capacitors voltages fluctuations. The proposed strategy gives good results in all the operating conditions, but it appears to be very useful especially in no-load or low-load operations, where other methods fail. Analytical, simulation, and experimental results, derived from a reduced-scale prototype, are presented and confirm the validity of the proposed approach. Index Terms--AC-DC power conversion, active rectifiers, high-power drives, medium-voltage drives, neutral-point-clamped (NPC) rectifiers, pulsewidth modulation (PWM).

Most of the loads in ac distribution systems have positive incremental impedance characteristic. However, power electronic loads, when tightly regulated, sink constant power from the system. Therefore, they have negative incremental impedance characteristic. This can cause negative impedance instability. Power electronic loads usually have a controlled or uncontrolled rectifier at the front end. In this paper, these loads are modeled using the generalized state-space averaging method. An assessment of their effects in ac distribution systems is also presented. Experimental results are presented to verify the proposed analysis. Index Terms--Analysis, constant power loads, dc/dc power converters, generalized state-space averaging, modeling, simulation, stability, state-space averaging.