A new class of hybrid AC/AC direct power converters

Abstract

Abstract-Variable voltage and variable frequency conversion of electrical energy from an AC source to an AC load is done in traditional power converters via a DC-link where an energy storage element (electrolytic capacitors) is situated. Despite its well-known benefits, it has the disadvantage of being bulky and to limit the converter lifetime. On the other hand, Direct Power Conversion (DPC) is an attractive concept, which doesn't need an energy storage buffer, but has two main disadvantages: reduced voltage transfer ratio (<0.86) and low immunity to voltage supply disturbances. This paper proposes a new approach to perform the power conversion by mixing various standard topologies of wellknown power converters in order to improve their performance/behavior. Simulation and experimental results prove that the hybrid structures are able to boost the output voltage capability (some above unity) and/or to fully compensate unbalanced voltage supply.

Implementation of a Hybrid AC–AC Direct Power Converter With Unity Voltage Transfer

“…The Hybrid Direct Power Converter is based on integrating an AVS at the intermediate dc link of a TMC [11], [12], as shown in Fig. 2(a).…”

“…The AVS of the HDPC can be of any type of dc to dc converter [11]. However, the following discussions are focused on using a simple dc to dc reversible boost converter for the AVS [12].…”

A predictive current control scheme for a hybrid AC/AC direct power converter

“…Implementation of Space Vector Modulation (SVM) for a twostage MC has been discussed in [9,10] and [13]; a similar approach as in [10,13] can be used for the HDPC. As shown in Fig.…”

“…The proposed control structure allows using the fixed frequency pulse width modulation therefore synchronization of switching of the AVS can be achieved to maintain the sinusoidal input currents. The predictive control also offers simple DSP based digital control without requiring any external circuitry like in the case of hysteresis current controller [13]. The paper presents an analytical study, control technique, modulation scheme and the important details of a realistic simulation model and simulation results of the proposed control scheme for HDPC.…”

“…Therefore, it is important to investigate alternative converter structures such as the DPC which has unity load voltage transfer to replace the traditional drives providing the possibility to have cost effective, compact industrial motor drives while fulfilling the standard power quality regulations. Hybrid Direct Power Converter (HDPC) structures as proposed in [13] offer improved robustness to supply voltage variations and provide unity VTR, which overcome the main draw back of CMC. In this paper, a new predictive current controller for a HDPC based on two-stage MC topology is proposed.…”