A control method for a high frequency link inverter using cycloconverter techniques

Abstract

Ihis paper descrites a new control methcd for a high-frequency link inverter using cycloconverter techniques a d discusses its cutput voltage characteristics.In t h i s mthcd, the cyclmverter ccnverts a high frequency voltage to a low frequency voltage by operating in three mcdes: positive rectifying d e , negative rectifying d e and free-&eeling mode. Pulse width dulation (€'"I control is performed at the cycloconverter.Numerical analysis and experiments show that the cutput voltage can be proportionally controlled by a reference voltage and that the cut@ i-mmmics can be decreased to a sufficient low level.A surge reduction circuit is presented for the inverter. This circuit can effectively reduce the switching surge. High ccnversion efficiency of over 90% is obtained under an output pxer of 1 kW. 1.In recent years, m y low prw uninterruptible power supplies (UPSs) of less than 5 kVA have been used to protect quipnent such as p e r m 1 cnnputers, word processors and loa1 area network terminals, fran failures and tenprary disturbances of the cannercia1 AC p e r supply. As these upss are often installed in offices, decreasing in size and weight of UPSs has teccme an iIIprtant goal.The size and weight of a UPS can be reduced by using a high-frequency link inverter, in which the l w frequency transformer is replaced by a high frequency one using high frequency switching techniques. Conventional highfrequency link inverters use three powerconversion stages: a Cc to high-frequency AC cmversion stage, a high-frequency AC to CC conversion stage and a Dc to lar-frequency AC CUIversion stage. Since these omversion stases are cawcted in cascade, the Conversion loss becanes large.The number of conversion stages can be decreased by utilizing cyclaxxlverter techni attain a high-frequency link inverter m' Fs). l h i s papr descrites a new m t r o l methd for a high frequency link inverter using cycloconverter techniques, and discusses its output voltage characteristics. CIRCUIT m G € i R A T I a AND CPERATICN Circuit OxfiqurationThe basic circuit configuration of the high-flink inverter is sham in Fig. 1. ' Ihe main circuit is rrmposed of a prinary inverter circuit, a high-frequency transforner, a cyclooomrerter circuit and an AC filter. S5 -,S are bidirecti-1 ordoff switches thraqh whicfl current can f l w in both directions. 'Ihe block diagram of the m t r o l circuit is Skmn in Fig. 2 . This control circuit is canp e d of an oscillator (OSC), a FiM signal generation circuit and logic circuits for the prinary inverter and for the cycloaxlverter. All these circuits are s y n c h i z e d by the oscillator signal. Primry w cycloconverter AC Filter Imerter Transformer s -s . uidirecti-1 switcher 5 8' Fig. 1 Basic configuration of the high frequency link inverter. PWH signal generation circultFig. 2 Block diagram for the m t r o l circuit.

Review of Isolated Matrix Inverters: Topologies, Modulation Methods and Applications

“…An alternative approach is to apply isolated DC-AC topologies without an evident intermediate DC-link. In these converters, the HFT secondary voltage can be converted to low frequency (LF) AC using an active rectifier and unfolder (Figure 1b) [35][36][37][38][39][40][41][42], or by using single HF AC to LF AC conversion (Figure 1c) [43][44][45][46][47][48][49][50][51][52][53]. Despite both of these approaches are commonly referred to as single-stage DC-AC converters, the systems with unfolding stage technically feature an additional low-frequency link (with rectified sine-wave) and, therefore, are considered as a quasi-single stage in this paper.…”

“…On the other hand, the topologies with unified HF AC to LF AC stage are performing AC-AC conversion directly, using bidirectional semiconductor switches, which is a distinctive feature of matrix converters [54]. In the literature, such systems are also referred to as HF-link inverters [39,52], cycloconverters [43,48] or single-stage inverters (converters) [30,32], but are all considered as isolated matrix inverters in this review. These systems are often capable of transferring power in both directions and can achieve soft switching conditions in semiconductors with advanced modulation methods [46][47][48][49][50][51][52][53][54][55][56].…”

“…In the literature, such systems are also referred to as HF-link inverters [39,52], cycloconverters [43,48] or single-stage inverters (converters) [30,32], but are all considered as isolated matrix inverters in this review. These systems are often capable of transferring power in both directions and can achieve soft switching conditions in semiconductors with advanced modulation methods [46][47][48][49][50][51][52][53][54][55][56]. Such features, together with a wide range of possible industrial applications, have attracted increased interest of research groups in isolated matrix inverters for many years.…”

Feasible single-phase UPS incorporating switched-mode PFC rectifier with high-frequency transformer link

“…Another system topology is to use a high-frequency linked sinewave PWM cycloconverter using bidirectional active switches which provides the isolated power stage to the high-frequency PWM inverter in the UPS (Muroyama et al 1989, Tokunaga et al 1992. The sinewave PWM cycloconverter directly converts the output voltage of the high-frequency transformer into a low frequency output voltage for the UPS.…”

A new control scheme for high-frequency link inverter design

“…Fig. 1(b) shows the solution diagram based on the principle of high-frequency link inverter [1,2]. The size and the weight of the system can be reduced by using the high-frequency link inverter, where the low frequency transformer is replaced by a high-frequency transformer and high speed switching devices are used in it.…”