Abstract. Recent environmental issues have accelerated the use of more efficient and energy saving technologies in renewable energy systems. High power high efficiency boost DC/DC converters for the use in photovoltaic, fuel cell systems are discussed in this paper from the viewpoint of power losses and efficiency. State of the art converters with switching frequency within the range of 25 kHz with IGBTs to 100 kHz with power MOSFETs and the highest efficiency close to 98%, depending on the load conditions, is considered. A comparison and discussion of the highest efficiency high power DC/DC boost converters is also presented in this paper.

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Abstmct -In the paper a new configuration of a soft-switched auxiliary resonant transistor pole inverter (ARTPI) is presented. The principle of its operation is discussed, simulation voltage and current transients are given and an analysis of the operation of the proposed inverter is made. The results of simulation calculations of losses and the results of experimental studies of ARTPI under soft switching are presented graphically. Two methods of controlling the inverter are suggested The advantages and disadvantages of this ARTP inverter are discussed.

Absrruci I11 the paper a configuration of a soft-switched Quasi-Resonant Zero Voltage Switching Inverter (QRZVSI) is presented. The principle of its operation with methods of control is discussed, simulation voltage and current transients are given and an analysis of the operation of the proposed inverter is made. A detail analysis of the operation of resonant circuits with bi-directional current flow in the coupling circuit of a conventional inverter was made. The results of simulation calculations of losses anal the resulls of experimental studies of QRZVSI under soft switching are presented graphically. The advantages and disadvantages of tha QRzvS Inverter are discussed. I.. lNTRODUCTlQNRecently, in view of their advantages, interest in high frequency resonant converter systems has increased. High frequency operation, small dimensions, lower weight, hig;la efficiency and low switching losses are only a few of the features of the new topologies. In resonant inverters, semiconductor power devices are switched at zero voltages or currents thus theoretically eliminating switching losses. On the other hand, conduction losses rise in relation bo the peak value of the current wave and complexity of the inverter structure. Resonant inverters should be able 'to operate with PWM and should be so constructed that it is possible tis add simple commutation structures to the main circuits of the conventional voltage inverters.In the article a new inverter system is presented in which the quasi-resonant circuit is used as a system coupling the DC voltage source to a conventional voltage converter. The operation frequency of the quasi-resonant coupling circuit is several times higher than the PWM carrier frequency of' the inverter.In order to limit losses, the number of commutations during operation should be reduced. In the article a PWM control method suitable for a quasi-resonant inverter is presented. The PWM control strategy presented ensures soft-switching of all inverter valves during the flow o f load current in any direction.A detailed analysis of the resonant circuit operation with bi-directional current flow in the coupling circuit of the conventional inverter was made. The problem of the soft switching, of power valves with a return of energy to the supply source though omitted by many authors is a serious application problem. The analytical equations and simulation studies are in agreement with the results of the experimental investigations. An analysis comparing the total losses o f the resonant converter systems studied with the conventional hard switching converter was then made. QUASI-RESONANT ZVS PWM INVERTER.In Fig. 1 the Quasi-Resonant ZVS PWM Inverter analysed is presented. The circuit is simple in comparison with other Resonant Pole Inverters. The topology of the inverter is derived fiom the Auxiliary Resonant Commutated Pole Inverter 184. 1 Io Conventional W lnvertar Fig. 1. Quasi-Resonant ZVS PWM Inverter IJT. A. N ANALYSIS OF ZVS CIRCUIT OPERATIQNThe functioning of the circuit can be represented by t...

Abstract. This paper presents a dual inductor-fed boost converter with an auxiliary transformer and voltage doubler for sustainable energy power converters. The new topology integrates a two-phase boost converter and a dual inductor-fed boost converter. The energy stored and transferred by both inductors can attain a wide input-voltage and load range which uses a constant switching frequency, by controlling the time duration of the simultaneous conduction of the two switches. Among other current-fed type boost converters the presented topology is attractive due to the high voltage conversion ratio, less stress on the components and less switch conduction loss. To verify the feasibility of this topology, the principles of operation, theoretical analysis, and experimental waveforms are presented for a 1 kW prototype.