Showing papers by "Doron Shmilovitz published in 1999"

A novel reversible boost rectifier with unity power factor

Abstract: A boost-driven high-power-factor AC/DC power converter is proposed. It possesses bidirectional power flow capability. A bias capacitor connected in series with the AC source provides a DC voltage boost at the input. Thus, a voltage that is always positive is applied at the input of a conventional boost DC/DC converter. A bidirectional DC/DC boost converter is employed to couple the AC side with the DC output. This converter may be controlled to draw sinusoidal average current at the AC side that is either in phase or 180/spl deg/ out of phase with the AC source. Hence, it can provide either unity power factor rectification or inversion. The topology was employed for the design of an AC/DC battery charger with a unity power factor for rated power of 6 kVA. IGBT devices with anti-parallel diodes are used as switches. The efficiency achieved was over 90% and the THD of the input current under 1.8%. This topology is superior to the conventional diode bridge rectifier followed by a DC/DC boost converter in the following points of comparison: (a) removal of the diode bridge eliminates crossover distortions that are inevitable in a conventional active power factor correction (APFC) circuit with diode rectification bridge at its front end; (b) removal of the diode bridge and usage of two bidirectional switches allows for bidirectional instantaneous power flow which makes possible operation in the inversion mode, in which power is transferred from the DC source to the AC source; and (c) at any instance of time only one semiconductor device conducts (as opposed to three or two in conventional rectifiers), which results in higher efficiency.

A novel rectifier/inverter with adjustable power factor

Abstract: An adjustable power-factor operation of a boost-based bidirectional AC/DC converter is described. It possesses a bi-directional power flow capability. The converter has a bias capacitor connected in series with the AC source which provides a DC voltage boost at the input. By appropriate control of the bias capacitor DC voltage, an always positive voltage is applied to the input of a boost power-factor corrector. This enables removal of a diode bridge rectifier that is commonly employed in switch-mode rectifiers. A bi-directional DC/DC boost converter allows for power factor adjustment in the full range of 0/spl deg/-360/spl deg/. Hence, the circuit can be used to compensate reactive power of other loads while either consuming active power (as in a battery charger) or providing active power (as in photovoltaic systems). The total harmonic distortion of the converter input current is less than 1.2% for any mode of operation. The operational principle of the proposed circuit was verified by Saber simulations.

Simple criteria to evaluate converter dynamics suitability for operation in active power factor correction systems

Abstract: A general approach to evaluate the converter dynamics versus the necessary dynamics for operation as an active power factor corrector is introduced. A simple criterion is developed in the time domain that enables characterization of converter topology and component values for APFC applications. This criterion can be incorporated in the design of APFC circuits to define the upper bounds on reactive component values whereas the lower bound is derived from the ripple requirements. The input current distortions caused by a converter whose characteristics do not meet the minimum requirements are calculated for a boost converter, which is chosen as a particular example.

New switch-mode topology for VAR compensation

Abstract: This paper presents a method of compensating for harmonics and reactive currents generated by nonlinear and/or reactive loads, by employing a bidirectional switch-mode rectifier. In this way, VAR compensation is achieved as a by-product while operating a switch-mode high power factor rectifier. Most bi-directional switch-mode rectifiers are suitable for such an application with some modifications of the control scheme and quantities that need to be sensed. A new switch-mode high power factor rectifier is introduced which has a bi-directional power flow capability and makes it possible to cancel harmonic and reactive currents.