In this paper we introduce digital Hilbert transformers composed of identical allpass subÞlters that are interconnected via extra multipliers. In the simplest case the overall transfer function corresponds to M Hilbert transformers in cascade where each transformer is derived by frequency shift of a half-band IIR Þlter. The overall transformer can also be designed to have a smaller passband rip...

A circuit configuration of a single-phase nonisolated online uninterruptible power supply (UPS) with 110-V/220-V input–output voltage ratings is proposed, allowing the bypass operation without a transformer even if the input voltage is different from the output voltage. The converter consists of an ac–dc/dc–dc three-level boost converter combined with a double half-bridge inverter. In this type...

VFT (variable frequency transformer) has been recently used as an alternative to HVDC (high voltage direct current) to control power flow between asynchronous networks. VFT consumes less reactive power than a back-to-back HVDC system, provides faster initial transient recovery, and has better natural damping capability. VFT is simply a DFIM (doubly-fed induction machine) where the machine torqu...

This paper presents a new transformer based multilevel inverter, with a novel pulse width modulation scheme to achieve seven-level inverter output voltage. The proposed inverter switching pattern consists of three fundamental frequency sinusoidal reference signals with an offset value, and one high frequency triangular carrier signal. This switching scheme has been implemented using an 8-bit Xi...

Soft-switching DC-DC converter using Phase-Shifted Pulse Width Modulation (PS-PWM) on secondary side of highfrequency transformer is described in the paper. The converter consists of a full-bridge inverter fitted with fast IGBT transistors. The output power of the converter is controlled by rectifier made up of two snap-off diodes in series with MOSFET transistors which is connected on secondar...

Transformer fault diagnosis and repair is a complex task that includes many possible types of faults and demands special trained personnel. In this paper, Petri Nets are used for the simulation of transformer fault diagnosis process and the definition of the actions followed to repair the transformer. An oil thermometer and a Buchholz relay are used for transformer fault detection. Simulation r...