Unified Non-Inverting and Inverting PWM AC–AC Converter With Versatile Modes of Operation

Abstract

This paper proposes unified non-inverting and inverting AC-AC converter (UNI-AC) using pulse width modulation (PWM) for the utility voltage compensation. It offers four effective switching states to regulate the output voltage in bipolar manner, facilitating versatile modes of operation with different number of switching states being modulated. Each mode of the proposed UNI-AC is able to compensate both the grid voltage sag and swell problems due to its bipolar voltage gain. The operational principle and comparison for all these modes are investigated in details. Also, the UNI-AC is reversible and compatible with full range of power factor. Other technical merits offered by the proposed approach include the compact hardware installation, reduced switch voltage stress (also low dv/dt) and decreased control complexity. Detailed analysis and experimental verification are presented in this paper. Index Terms-Bipolar voltage gain, PWM direct ac-ac converter, utility voltage compensation, versatile modes of operation.

A Single‐Phase Buck‐Boost Matrix Converter with Low Switching Stresses

“…The current conduction paths for the turn on and turn off period of high frequency switching devices are highlighted in Figures 1(a) and 1(b), respectively. PWM average switching model with duty cycle "d" for positive input voltage based on the analysis in [29] is obtained as follows.…”

“…The conduction losses of low switching frequency devices depend on forward bias voltage of fast recovery diode ( ), its on-state resistance ( ), on-state resistance of MOSFET ( ), and magnitude of conducted current ( ) as current conducted by each switch is the same as the inductor. The conduction losses are computed by considering the sinusoidal output current [29] in the form = (max) sin( ). The conduction losses of the proposed converter and the converter in [31] are computed in (18) and (19), respectively.…”

“…The coupled inductors as in [28] solve the problems of voltage and current surges, but it increases the size and cost of the switching converters. An ac-to-ac converter with common grounding and bipolar voltage gain is proposed in [29]. It operates in noninverting buck and inverting buck-boost mode to compensate the grid voltage sag and swell problem.…”

A Single-Phase Buck and Boost AC-to-AC Converter with Bipolar Voltage Gain: Analysis, Design, and Implementation

“…The non-z-source AC voltage controllers, in [22][23][24][25][26], eliminate the extra circuit elements but their inverting buck-boost operation requires high voltage switching stresses, high inductor ripple current and high switching currents. This results in high switching, conduction, and filtering of the inductor's DCR resistance losses.…”

A New CUK-Based Z-Source Inverter

“…In [17], an AC-side voltage doubling converter is presented. Another interesting topology named UNI-AC (unified non-inverting and inverting AC-AC converter) is proposed in [18]. On the other hand, a Z-source inverter was first proposed in [19], which can achieve a boost function of input DC voltage by its X-shaped impedance network.…”