Khairy Sayed

New High Voltage Gain Dual-boost DC-DC Converter for Photovoltaic Power Systems

Abstract This article presents a new circuit topology of a high-voltage step-up boost DC-DC converter for photovoltaic power systems. The converter boosts the low-output voltage of the solar cell to the required voltage for the load. The proposed circuit has various advantages compared to the conventional boost converters, namely a higher boost rate with low duty cycle, lower voltage stress on components, and higher efficiency. The equations of a dual-boost converter are analyzed, highlighting the advantages of the new DC/DC converter circuit topology. The operation principle is explained using the operating intervals equivalent circuits and operation waveforms. Then, mathematical and theoretical analyses of continuous and discontinuous conduction modes of the converter are presented. Losses and thus efficiency of the proposed converter are calculated using MATLAB (The MathWorks, Natick, Massachusetts, USA). Calculations are used to compare the efficiency of the proposed topology with others available in the literature regarding the benefits of decreasing cost and complexity. A photovoltaic system simulation model is developed using PSIM (Powersim Inc., Woburn, Massachusetts, USA) to validate the proposed converter. The proposed high voltage gain boost converter has been implemented for a 100-W load and tested to verify the principle of operation.

A solar-wind hybrid power system for irrigation in Toshka area

This paper is aimed at calculating the power demand of a combined irrigation and domestic load in Toshka area, Toshka, Egypt. The pipe line system for irrigation is designed. An economic feasibility study has been made for hybrid PV-wind system to power this combined load. Sizing of the hybrid system components was investigated using MATLAB Code and HOMER Package. The energy cost values of the hybrid system agrees reasonably with published those before.

DC-DC converter with three-phase power factor correction for arc welder

This paper presents a PWM converter, which enables to maintain high power-factor of arc welding power supply and to suppress input current harmonics. The main function of this system is to maintain unity power-factor by controlling input current to be sinusoidal, and to generate stable DC output voltage through half-bridge inverter and output rectifier. The proposed converter has high power factor, low harmonic distortion, and tight output regulations. A control scheme is employed to reduce the switching and rectification losses. The modeling and simulation analysis are performed to evaluate the performance characteristics. The proposed converter meets the IEC 61000–3–2 regulations with near-unity power factor and high efficiency.

Design and implementation of stand-alone residential PV system

This paper is focused on construction of a stand-alone residential 2-kW centralized PV system to feed different domestic loads at a home including lighting loads, washing machine, TV, refrigerator and computer. The stand-alone residential 2-kW PV system consists of PV generator, storage batteries, charge regulator, inverter, filter and maximum power point tracking control system. The paper in steps includes PV modeling, software development for monitoring storage batteries, development of maximum power point tracking controller, design and implementation of an inverter and use of a filter to improve the inverter output waveform.

Analysis of overcurrent numerical-relays for protection of a stand-alone PV system

This paper presents an overcurrent protection scheme for a stand-alone PV system consisting of PV array, DCDC converter, DC-AC inverter, relay and circuit breaker to fed an irrigation load. This scheme is based on a numerical relay which is composed of rms current converter, integrator, comparator, low-pass filter and reset logic. The model of the system is simulated using MATLAB/Simulink. The performance of the relay is investigated at normal conditions, even during motor starting of the irrigation load as well as at faulty conditions. The relay succeeds to discriminate between the fault current and the starting current of the motor and operates only under faulty conditions.

Steady-state modeling and control of a microgrid supplying irrigation load in Toshka Area

This paper is aimed at sizing solar-wind-battery standalone microgrid for supplying irrigation and domestic loads in Toshka area, Toshka, Egypt. Not only the MG system components but also the interconnection cables and feeders are sized. Steady-state power flow through the MG system is analysed at varying sun irradiation and wind speed. Modeling of the MG components and their control of system voltages, currents and powers are investigated. Power flows during different MG operation conditions including absence of wind and sun as well as sudden disconnection of the load are studied.

Smart distribution system Volt/VAR control using the intelligence of smart transformer

This paper presents the dynamic performance of a smart distribution system. A detailed power distribution system model has been developed with a smart electronic transformer using the MATLAB/ Simulink power systems simulation package. The results are presented using this simulation to illustrate the capability of Smart transformer units to assist with voltage regulation of LV feeders. Low voltage distribution networks are recovered from minor and severe perturbations in the AC system is verified. Simulations conducted on case study network representing a typical 4-wire LV distribution system under different load/generation conditions. The LV network fed on 22 kV distribution system through a smart transformer. The results demonstrate the improving the network power quality levels and eliminate the voltage unbalance.

New DC rail side soft-switching PWM DC-DC converter with voltage doubler rectifier for PV generation interface

This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type high power dc-dc converter for photovoltaic applications. The proposed step-up DC/DC converters with transformer isolation can obtain high voltage step-up trough turns ratio. The proposed dc-dc power converter is composed of typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 kHz under principle of soft switching.

Analysis of protection system for a microgrid supplying irrigation load in Toshka Area

This paper is aimed at presenting a scheme for the protection of a microgrid (MG) system in Toshka area, Egypt. Detailed descriptions of fault scenarios and system behavior following fault clearing are presented. The fault current calculation methodology is presented based on the estimation of virtual impedances of inverters interfacing distributed generators DGs into the MG. Three-phase and single-phase to ground faults are investigated at different system buses.

Modeling and Simulation of PV Arrays

Modeling of PV generator represents very important goal. Such modeling will allow conducting measurements without the constraints of environmental conditions. In addition it will save the use of an actual PV array, other related equipments and time. The objective of this research work is to develop an accurate and simplified photovoltaic source model. The developed model considers most of environmental variables such as: ambient temperature, solar radiation incident angle, radiation intensity, wind velocity and partial shading. Results of PV array model characteristics are easily obtained by connecting variable resistance across the PV arrays. The simulated characteristics are in good agreement with those obtained from the available experimental data; model can be used to achieve optimal choice and design of the power converter interfacing the PV generator to the utility. Further more, the model will allow choosing the suitable power converter control methods.Copyright