Decoupling of Fluctuating Power in Single-Phase Systems Through a Symmetrical Half-Bridge Circuit

Abstract

Single-phase ac/dc or dc/ac systems are inherently subject to the harmonic disturbance that is caused by the wellknown double-line frequency ripple power. This issue can be eased through the installation of bulky electrolytic capacitors in the dc link. Unfortunately, such passive filtering approach may inevitably lead to low power density and limited system lifetime. An alternative approach is to use active power decoupling so that the ripple power can be diverted into other energy storage devices to gain an improved system performance. Nevertheless, all existing active methods have to introduce extra energy storage elements, either inductors or film capacitors in the system to store the ripple power, and this again leads to increased component costs. In view of this, this paper presents a symmetrical half-bridge circuit which utilizes the dc-link capacitors to absorb the ripple power, and the only additional components are a pair of switches and a small filtering inductor. A design example is presented and the proposed circuit concept is also verified with simulation and experimental results. It shows that at least ten times capacitance reduction can be achieved with the proposed active power decoupling method, and both the input current and output voltage of the converter can be well regulated even when very small dc-link capacitors are employed.

DQ reference frame modeling and control of single-phase active power decoupling circuits

“…Unfortunately, E-caps are also known to be very vulnerable under high temperature operation, and they may bring design difficulties if long lifetime is desired for the power converter, e.g. in PV and light-emitting diode (LED) applications [9][10][11][12][13][14][15][16][17].…”

“…Fig. 1 presents some of recently proposed single-phase active power decoupling circuits which are essentially derived from threephase circuit configurations [9][10][11][12]. As shown, a third switching leg is introduced into the circuit, and it can essentially provide a new input to the system and be modulated in such a way that the instantaneous power flow between ac and dc sides is always balanced.…”

“…In terms of controller design, the aforementioned research works [9][10][11][12][13][14][15][16][17] also employ a similar control structure, where the required inductor current / capacitor voltage compensation reference is calculated according to the instantaneous power balancing equation, and then simple proportional resonant (PR) controllers can be designed for zero steady-state reference tracking. Although being effective in power decoupling, this kind of control approach is essentially an indirect regulation to the dc-link ripple voltage and its control accuracy is highly parameter dependent.…”

DC-Side Harmonic Mitigation in Single-Phase Bridge Inverter

“…The first type is the control strategy that injects 3th, 5th harmonic to the AC-side actively to reduce the AC-side pulsation power directly [3] . The second type is to parallel an active power filter, and then transfer the low-frequency power to extra energy-storage elements by controlling the active power filter [4] . The last type is to compensate for the AC-side pulsation power by controlling the low-frequency power within the system [5] .…”

An Efficiency Improved Active Power Decoupling Circuit with Minimized Implementation Cost

“…Instead of simply using large E-caps for ripple power attenuation, various active power decoupling circuits have been proposed to reduce the dc-link capacitance requirement in single-phase systems [4][5][6][7][8][9][10][11], and the basic concept of active power decoupling is to use inductors or film capacitors to store the system ripple power in ac form through proper modulation of active circuits. In this case, the instantaneous power from ac side and dc side can be balanced and the dc-link capacitance can theoretically be zero.…”