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The objective of this paper is to propose an efficiency model to evaluate the impact of the pulse width modulation (PWM) duty cycle jitter on the efficiency of switching-mode power converter. By taking the product of two perturbation terms into consideration, which is ignored in the conventional average small-signal model, the average efficiency model is proposed first. Due to the nonlinear characteristic of the PWM generator, the multifrequency efficiency model is also developed by considering the sideband frequency. Three different perturbation waves are induced to the control loop of the converter to generate the jitter to observe its impact on the efficiency. The mathematical expression of the efficiency drop based on the proposed multifrequency model is derived. The reason of control-to-output gain's magnitude spike on the Bode plot can be explained by the derived equations. Eventually, the methods to reduce the efficiency drop caused by the jitter are suggested. In spite of various perturbation frequencies, amplitudes, and waveforms, the mathematical calculation, the computer simulation, and the hardware measurement of the efficiency drop are consistent which validate the accuracy of the proposed multifrequency efficiency model. [ABSTRACT FROM AUTHOR]

Presents the introductory editorial for this issue of the publication. [ABSTRACT FROM AUTHOR]

This paper proposes a line current distortion compensation method, which is a fusion of the conventional variable on-time (VOT) control and the average current mode (ACM) control, for DCM/CRM boost PFC converter with zero current switching (ZCS)/zero voltage switching (ZVS)/valley switching (VS)/switching frequency limitation (SFL) functions. In this paper, the mathematical analyses of the line current distortion for the DCM/CRM boost PFC converter with ZCS/ZVS/VS/SFL functions are also derived to explain the causes of the line current distortion. In order to increase efficiency, the ZVS/VS/SFL functions are needed but the line current will be further distorted. To compensate the distorted line current, the ACM-based VOT (ABVOT) control for the DCM/CRM boost PFC converter is proposed. In addition, the constant-on-time-based noise-immunity S/H method is proposed to replace the multiplier, which is always needed for the conventional ACM-based control. The performance of the proposed ABVOT control with S/H method will be demonstrated by simulation and experiment results. [ABSTRACT FROM PUBLISHER]

In this paper, a buck-type power converter as the battery charger for the stand-alone wind power system is proposed. The proposed power converter can harvest the maximum power from the wind turbine while generating pulsating current for the battery bank to improve the charging efficiency. The maximum power point tracking function is realized by the constant on-time control, the circuit parameter design of the power converter, and the characteristics of wind turbine. The pulsating battery charging current is implemented by the discontinuous conduction mode operation of the proposed power converter. Also, the overspeed protection of the wind turbine can be naturally achieved when high power output occurs. Circuit simplicity and high reliability are the major advantages of the proposed power converter. Hardware experimental results from a 400-W prototype circuit are presented to verify the performance of the proposed power converter. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose a feedforward delta modulation (FDM) control for switching-mode power converters. The operation principle and mathematical derivation for both the conventional delta modulation (CDM) and the FDM are presented. The proposed FDM uses the control signal to generate the variable integrating slope to obtain better control ability. By comparing to the CDM, the proposed FDM can improve the performance of the dc–ac inverter. The advantages include the following features: 1) wider switching frequency range with smaller electromagnetic interference; 2) larger fundamental component with less harmonics; 3) higher duty-ratio linearity; and 4) elimination of asymmetrical operation. In addition, the proposed FDM can be applied to the dc–dc converter, which cannot be done by using the CDM. It can achieve the fast transient response with voltage-mode control. The FDM controller design strategy for the dc–dc converter is given in this paper, followed by a design example. Finally, experimental results are shown to verify the performance of the proposed FDM for both the dc–dc inverter and the dc–dc converter. [ABSTRACT FROM PUBLISHER]

Proposes a novel voltage-type active power line conditioners (APLC), which cancels line current harmonics by injecting a compensation current. Two types of harmonic filters; General neuron symbol; Two-layer feedforward neural network; System description; Simulated system performance of APLC; Conclusions.

This article presents a modified asymmetrical half-bridge flyback converter (AHBFC) to fulfill the single-stage step-down ac–dc universal input voltage application. This topology is obtained from the integration of a buck-type power factor correction, an auxiliary energy buffer, and a conventional AHBFC. By sharing common switches and utilizing transformer's leakage inductor, the single-stage circuit can achieve both high power factor (PF) and low total harmonic distortion with the simple constant on-time control while regulating the dc output voltage. In addition, it is able to operate in universal input voltage with low dc link voltage and low output voltage. Moreover, the zero voltage switching and the zero current switching features of the power switches can also be achieved. Detailed analyses and design procedures of the proposed converter are given and verified by the experimental results. Finally, the comparison with reported circuit topologies and power loss analyses verified by experimental results are presented to provide the insight of practical design. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose a novel photovoltaic (PV) micro-inverter with PV current decoupling (PVCD) strategy to achieve maximum power point tracking (MPPT) performance without using large electrolytic capacitors. Conventionally, the grid-connected PV micro-inverter needs a large PV-side electrolytic capacitor to suppress the double-line frequency voltage ripple, which is caused by the injected ac grid power, to achieve the desired MPPT performance. However, the short lifetime electrolytic capacitor will reduce the PV micro-inverter's reliability dramatically. Therefore, different active power decoupling circuits (APDCs) have been proposed in published papers to reduce the required input capacitance so that the long lifetime film capacitor can be used to replace the electrolytic capacitor. Unlike the conventional APDC with charging and discharging modes operation, a novel PVCD strategy, which is based on the concept of current decoupling instead of power decoupling, is proposed to simplify the control mechanism of the PV micro-inverter. Furthermore, to accomplish the proposed current decoupling concept, a novel circuit topology for the PV micro-inverter is also proposed. With the proposed PVCD strategy, the current decoupling tank (CDT) inside the proposed PV micro-inverter can buffer the current difference between the constant current from the PV panel and the rectified sinusoidal current of the ac grid current. Therefore, the input capacitance on the PV-side can be reduced dramatically and the long lifetime film capacitor can be used to replace the electrolytic capacitor. The reliability of the PV micro-inverter with good MPPT performance can be increased. In this paper, the operation principle and the component design of the proposed PV micro-inverter with PVCD strategy will be presented. Simulation results and experimental results of a prototype 240 W PV micro-inverter is shown to verify the performance of the PV micro-inverter with PVCD strategy. [ABSTRACT FROM AUTHOR]

A multi-mode operation for the three-phase photovoltaic (PV) power system with low-voltage ride-through (LVRT) capability is proposed. With the proposed multi-mode control strategy, the active power from the PV arrays can be continuously extracted by the interleaved boost converter during LVRT, whereas the maximum power point tracking operation can be quickly achieved after the grid fault clearance. In addition, the multi-channel boost converter with interleaved operation can increase power conversion efficiency while decreasing the input current ripple. On the other hand, the current amplitude limitation control of the three-phase inverter can provide maximum reactive power under rated current amplitude during the voltage sag period and output the demanded reactive/rated current ratio to meet different LVRT codes. A three-phase 5-kVA prototype PV converter is built and tested to verify the performance of the proposed multi-mode operation strategy and the LVRT capability. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to propose a three-phase back-to-back active power conditioner (APC) with dc-link voltage control strategies for microgrid applications. The demanded active and reactive powers of the APC via bidirectional power flow control can help to regulate the frequency and voltage of microgrids to achieve high stability. Moreover, the dc-link capacitor is the necessary component of the back-to-back APC for power decoupling and power flow balancing. In order to provide the ability to improve the power quality and stability of microgrids as well as to reduce the dc-link capacitance, two dc-link voltage control methods are developed: 1) optimal ac-line current regulation strategy and 2) dynamic dc-link voltage regulation (DDVR) strategy. Under steady state, the proposed optimal ac-line current regulation strategy is able to minimize the change of the input current variation as well as to achieve the dc-link regulation in one 60-Hz cycle. As soon as an abrupt or continuous power change occurs, the dc-link voltage of the APC will be changed dramatically, and the voltage protection could easily be triggered. Therefore, a novel DDVR strategy is proposed in order to prevent the false alarm as well as to reduce the required dc-link capacitance. Thorough mathematical equations corresponding to the proposed dc-link voltage control strategy are presented which can be used to determine the appropriate dc-link capacitance. Computer simulations and hardware experiments obtained from a 5-kVA prototype circuit demonstrate the feasibility and performance of the proposed APC. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to propose a simplified reactive power control (SRPC) strategy for single-phase grid-tied photovoltaic (PV) inverters. With the proposed SRPC strategy, a cost-effective microcontroller can be adopted to achieve an effectively reactive power control. Moreover, the current-mode asynchronous sigma-delta modulation (CASDM) is adopted to enhance the current control's dynamic response and reduce both the current harmonic distortion and electromagnetic interference. In this paper, the operational principle of the proposed SRPC is introduced. Then, the small signal analysis for the PV inverter with the CASDM is presented. Finally, a 1-kVA single-phase PV inverter was built to verify the performance of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to propose a modularized bidirectional single-phase grid-connected inverter (BGI) with constant-frequency asynchronous sigma–delta modulation (CF-ASDM) control for the renewable energy (RE)-supplied dc power system. The proposed BGI can be operated either in the inverter mode (IM) or rectified mode (RM); both are necessary features for the RE-supplied dc power system. By comparing to the conventional ASDM with variable switching frequency, the proposed CF-ASDM can simplify the filter design and can reduce the computational burden of the digital signal processor while maintaining the merit of quick dynamic response. Moreover, the proposed BGI has a redundant central controller which can increase the system reliability. The major contribution of this paper includes developing the modularized BGI with CF-ASDM control scheme for IM and RM operations thoroughly and applying it to the RE-supplied dc power system successfully. In this paper, the mathematical equations to achieve the constant switching frequency operation for the CF-ASDM will be derived. Computer simulations and hardware experiments are shown to verify the performance of the proposed modularized BGI with CF-ASDM control. [ABSTRACT FROM PUBLISHER]

Proposes a soft-switching Zeta converter with an asymmetrical pulsewidth modulation control. Features of the Zeta converter; Operational principle of the converter; Feasibility of converter operation at low to medium power level.

An autonomous dc-bus dual-level control (DDLC) strategy is proposed for the two-stage three-phase photovoltaic power system. During the grid-fault situation, the second-stage inverter may lose the ability to regulate the dc-bus voltage and the first-stage boost converter has to change its mode from maximum power point tracking mode to dc-bus voltage control (DCVC) mode. However, the communication between the two-stage circuits must be established. The circuit complexity and cost will increase while the system's scalability and flexibility will be reduced. With the proposed DDLC strategy, the dc-bus voltage is controlled into different levels for different operation modes, without the need of communication mechanism. No extra sensors or circuits are required. Two important design parameters for the proposed DDLC are derived thoroughly. The computer simulations and hardware experimental results of a 4 kVA prototype circuit are presented to validate the performance of the proposed DDLC strategy. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose the development of a multiinput dc–dc converter (MIC) family, which is composed of isolated and/or nonisolated dc–dc converters. By analyzing five basic isolated dc–dc converters, four isolated pulsating voltage source cells and three isolated pulsating current source cells are generated. Moreover, a semiisolated multiinput converter (S-MIC) for hybrid PV/wind power charger system which can simplify the power system, reduce the cost, deliver continuous power, and overcome high-voltage-transfer-ratio problems is proposed. In this paper, the operational principle of the proposed S-MIC is explained, the small-signal ac model is derived, and the controller design is developed. Computer simulations and experimental results are presented to verify the accuracy of the proposed small-signal ac model and the performance of the proposed S-MIC. [ABSTRACT FROM AUTHOR]

This paper presents single-stage regulators with power-factor correction (PFC) based on an asymmetrical half-bridge topology. The proposed regulator is formed from a boost converter with two coupled inductors and an asymmetrical half-bridge converter with the synchronous switch technique, and it is controlled with pulsewidth modulation to achieve zero-voltage switching (ZVS). The boost converter is operated in discontinues conduction mode to achieve PFC. With the coupled inductors, input current ripple and power factor can be improved significantly. The proposed regulator has the features of constant-frequency operation, ZVS, and low voltage stress imposed on the active switches. Moreover, the regulator can achieve high power factor, high power density, high efficiency, low switching loss, and low component count, which makes its applications at medium-power levels feasible. Experimental results have verified the discussed features of the proposed regulator. [ABSTRACT FROM AUTHOR]