Non-linear properties and efficiency improvements of a bi-directional isolated DC-AC converter with soft commutation
ABSTRACT This paper presents the operation principle and the properties of a single-phase DC-AC converter with medium frequency transformer and soft commutation. The influence of the non-dissipative snubber capacitor and the transformer parasitic components for ZVS and ZCS are explained in relation with their influence of the output characteristic. Additionally the effect of the semiconductor voltage drop is considered to get a precise circuit model for steady-state continuous operation. Finally efficiency improvements of this phase-shift PWM DC-AC converter are achieved by actively short-circuiting the circulating current at the AC-side during full load operation.
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ABSTRACT: This paper introduces a new bidirectional, isolated DC-DC converter. A typical application for this converter can be found in the auxiliary power supply of hybrid electric vehicles. A dual half-bridge topology has been developed to implement the required power rating using the minimum number of devices. Unified zero-voltage switching was achieved in either direction of power flow with neither a voltage-clamping circuit nor extra switching devices and resonant components. All these new features allow high power density, efficient power conversion, and compact packaging. Complete descriptions of operating principle and design guidelines are provided in this paper. An extended state-space averaged model is developed to predict large- and small-signal characteristics of the converter in either direction of power flow. A 1.6-kW prototype has been built and successfully tested under full power. The experimental results of the converter's steady-state operation confirm the soft-switching operation, simulation analysis, and the developed averaged model. The proposed converter is a good alternative to full-bridge isolated bidirectional DC-DC converter in medium-power applications.IEEE Transactions on Industry Applications 04/2003; · 1.67 Impact Factor
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ABSTRACT: The use of electrical equipment in rail and ship transportation is bound to consideration on mass and size, particularly because of conventional low frequency transformers. On this paper, an optimized multilevel converter with medium frequency transformer is presented. It allows to adapt voltage from primary generators (6.6kV) to service use (440V). From a pseudo continuous model of the converter, we present a method to improve its working and to define a corresponding operating domain.01/2001;
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ABSTRACT: A novel ac/dc converter topology incorporates a voltage source converter with capacitive snubbers and a cycloconverter, connected by a transformer. By alternately commutating the two converters it is possible to achieve soft switching conditions for all of the semiconductor elements. A control method is studied by which it is possible to reduce the transformer core losses by only magnetising the transformer when a PWM pulse should be applied on the ac side of the system. Furthermore, it is shown that resonant commutation of the voltage source converter is possible by utilizing the cycloconverter for short circuiting the transformer terminals.01/2002;