Showing papers by "Doron Shmilovitz published in 2005"

On the control of photovoltaic maximum power point tracker via output parameters

Abstract: A new approach for tracking the maximum power point of photovoltaic arrays is presented. The maximum power point tracker output voltage and current are used for control purposes, rather than for its input voltage and current. It is shown that using the output parameters simplifies the maximum power point tracker controller. Moreover, using this approach, only one out of the two output parameters needs to be sensed. This observation is general and applies regardless of the power stage or the realisation control algorithm. Contrary to what might have previously been assumed, it is theoretically shown that the MPPT control that uses a single output control parameter applies to nearly all practical load types, regardless of the load nature.

On the definition of total harmonic distortion and its effect on measurement interpretation

Abstract: The existence of two different definitions for total harmonic distortion (one in comparison to the fundamental and one in comparison to the signal's root mean square) might cause ambiguity and misinterpretation of measured data. The difference between those definitions is stressed out in this letter. It is suggested that total harmonic distortion measurements in the context of power systems should always adopt the first definition and never the second.

Analysis and design of power gyrators in sliding-mode operation

Abstract: The use of sliding-mode techniques and the insertion of damping networks in fourth-order convertors with both input and output filters lead in certain cases to a stable equilibrium point with gyrator characteristics. The buck convertor with input filter and the Cuk convertor are shown to have stable dynamics and an equilibrium point with gyrator characteristics for certain parameter values. The analytical predictions are verified by means of simulation and experimental results.

Photovoltaic maximum power point tracking employing load parameters

Abstract: Photovoltaic maximum power point tracking can be accomplished by monitoring the readings of the load parameters instead of the photovoltaic panel output parameters. It is demonstrated that load parameters based maximum power point tracking has advantages over conventional method in terms of tracking efficiency and simplicity of the hardware and software involved.

Low-harmonic, three-phase rectifier that applies current injection and a passive resistance emulator

Abstract: A new three-phase diode bridge rectifier that provides low harmonic distortion of the input currents applying current injection technique is proposed in this paper. The rectifier applies a novel passive resistance emulator consisting of four diodes and a transformer with the volt-ampere rating of 3.57% of the rectifier-rated power. Optimization of the transformer turns ratio is performed in order to minimize the input current total harmonic distortion (THD). It is shown that with the optimal turns ratio the input current THD equals 3.72%. Dependence of the input current THD on the load current is analyzed, and it is shown that at low load currents the rectifier operates in the discontinuous conduction mode with the THD of 7.79%. The analytical results are experimentally verified on a 2 kW rectifier, indicating that the input current THD lower than 8% is provided within a wide range of the load current variations applying simple circuitry.

Application of duality for derivation of current converter topologies

Abstract: A unified approach is suggested for the derivation of current-tocurrent converter topologies, which relies on duality principles. As conventional duality rules have restricted utility and are difficult to apply with switched mode circuits, special attention is devoted to switch mode converter element dualities. Also, a special means of viewing complex switched mode topologies as a cascade combination of building blocks is developed. This method simplifies the treatment of circuits containing transformers and switching bridges. The suggested approach provides a universal means for derivation of current-to-current converters by dually transforming voltage-to-voltage converter topologies. Examples of the utilization of this method for derivation of various current-to-current converters, including Buck, Boost, Buck-Boost, ˇ Cuk, Sepic, and Two-Switch Forward, are provided, as well as a practical design example for SMES (Superconducting Magnetic Energy Storage) application.

Resonant converter with Loss Free Resistor Characteristic

Abstract: A novel loss free resistor realization based on a resonant converter is presented. The resonant loss-free resistor is suitable for applications that need a resistive element or high quality rectifier, yet desire a high efficiency and low EMI. Simulations studies were carried out show that the circuit is indeed a loss free resistor and to verify the analysis