Nabil A. Ahmed

A Stand-Alone Hybrid Generation System Combining Solar Photovoltaic and Wind Turbine with Simple Maximum Power Point Tracking Control

This paper proposes a hybrid energy system combing solar photovoltaic and wind turbine as a small-scale alternative source of electrical energy where conventional generation is not practical. A simple and cost effective control technique has been proposed for maximum power point tracking from the photovoltaic array and wind turbine under varying climatic conditions without measuring the irradiance of the photovoltaic or the wind speed. The proposed system is attractive owing to its simplicity, ease of control and low cost. A complete description of the proposed hybrid system along with detailed simulation results which ascertain its feasibility are given to demonstrate the availability of the proposed system in this paper. Simulation of the hybrid system under investigation was carried out using PSIM software

Quasi-Resonant Dual Mode Soft Switching PWM and PDM High-Frequency Inverter with IH Load Resonant Tank

In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current soft switching pulse modulation single-ended push pull (SEPP) series load resonant inverter with two auxiliary resonant lossless inductor snubbers is proposed for consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each mode equivalent circuits. The new multi resonant high-frequency inverter can regulate its output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of asymmetrical PWM control scheme. The consumer brand-new IH products using proposed ZCS-PWM series load resonant SEPP high-frequency inverter is evaluated and discussed as compared with conventional high-frequency inverter on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM, the pulse density modulation (PDM) strategy is demonstrated for high frequency multi resonant inverter. Its practical effectiveness is substantially proved from an application point of view

Next generation high efficiency high power dc-dc converter incorporating active switch and snubbing capacitor assisted full-bridge soft-switching PWM inverter with high frequency transformer for large current output

This paper presents a new circuit topology of dc busline switch-assisted full-bridge soft-switching PWM inverter type dc-dc power converter which is composed of typical voltage source H full-bridge type high frequency PWM inverter in addition to a single dc busline side power semiconductor switching device for PWM scheme and a capacitive lossless snubber. Under the newly-proposed high frequency inverter link dc-dc high power conditioning and processing circuit, all active power switches in the full-bridge arms and dc busline can achieve ZVS/ZVT turn-off commutation operation. On the other hand, although the conduction power loss of dc busline switch increases a little, the total turn-off switching losses of full-bridge type PWM inverter and dc busline switch with the single lossless capacitive snubber parallel with dc busline can be significantly decreased. As a result, the switching frequency of high frequency inverter power stage using IGBTs can be actually selected more than about 10 kHz. The more the switching frequency of full-bridge inverter increases, the more newly-proposed soft-switching dc-dc power converter with a high frequency transformer link has remarkable advantage as for the power conversion efficiency and power density as compared with the conventional hard-switching inverter type dc-dc power converter. The effectiveness of this new converter topology is proved for low voltage and large current dc-dc power supplies from a practical point of views.

Switched Capacitor Snubber-Assisted Zero Current Soft Switching PWM High Frequency Inverter with Two-Lossless Inductive Snubbers

In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM series load resonant high frequency inverter with two auxiliary edge resonant lossless inductor snubbers is proposed for small consumer induction heating appliances. The operation principle of this high frequency inverter is described using the switching mode equivalent circuits. This newly developed multi resonant high frequency inverter using trench gate IGBTs can regulate its high frequency output AC power under a principle of constant frequency edge-resonant soft switching commutation by asymmetrical PWM control scheme. The high frequency power regulation and actual power conversion efficiency characteristics of consumer brand-new IH products that use the proposed soft switching PWM series load resonant high frequency inverter are evaluated. The practical effectiveness and operating performances of the newly proposed soft switching inverter are discussed as compared with the conventional soft switching high frequency inverters based on simulation and experimental results from an application point of view

Dual-mode time-sharing one-stage single-phase power conditioner using sinewave tracked soft switching PWM boost chopper

The paper presents a novel circuit topology of a high efficiency single-phase sinewave power conditioning and processing converter with a DC-link chemical capacitor. This power conditioner, used as a small scale stand-alone new-energy related power generation system, is composed of time-sharing operated sinewave absolute modulation boost chopper with a bypass diode in the first power processing stage and cascaded with a time-sharing sinewave pulse modulated full-bridge inverter as a second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the power processing stage with the time-sharing dual mode sinewave modulation scheme is described with a simple design example. The paper provides and describes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the effectiveness of this novel one stage sinewave power conditioner related to new-energy generation system is reviewed through the experimental results.

A Novel Circuit Topology of Three-Phase Direct AC-AC PWM Voltage Regulator

Recently, a new generation of ac-ac single-phase and three-phase power converters with more commutations per half cycle has been proposed for ac power or ac voltage conditioning due to the increasing availability and power capability of high frequency controlled-on and off power semiconductor switching devices. This paper presents a novel simple circuit topology of symmetrical PWM ac line conditioning circuit for three phase power systems. The converter topology uses a minimal number of controlled power semiconductor switches and features buck voltage capability. This ac-ac power converter is seen to be an ac voltage regulator with output voltage range of 0-1 p.u. with reasonable current and voltage waveforms. The operating principle and the operation modes of the proposed three-phase direct ac-ac power and voltage conditioner are described and evaluated through a design example based on analytical expression and simulation results

Advanced Single-Stage Soft Switching PWM Power Conditioner with Coupled Inductor PWM Boost Chopper Cascaded PWM Inverter and Time-Sharing Sinusoidal Follow-Up Control Scheme

This paper presents an advanced one-stage power conditioner circuit configuration suitable and acceptable for new energy generation systems specially low voltage large current distributed power supplies as solar photovoltaic and fuel cell or new storage applications as electric double layer capacitors and new type batteries. The circuit configuration depends mainly on eliminating the unreliable electrolytic capacitor DC link and using a bypass diode and coupled inductor assisted boost chopper to increase the boosting ratio and achieving high power conversion efficiency. This power conversion system is a modified version of the DC-DC converter previously proposed by the authors, which is composed of a time-sharing operated sinewave absolute modulated bypass diode and coupled inductor assisted boost chopper to produce a sinewave absolute value tracking AC voltage at the DC link and a sinewave PWM cascaded inverter to produce the sinusoidal AC voltage. This power conditioner is operated by selective time-sharing dual mode pulse pattern signal processing control scheme. The paper discusses also the soft switching operation of the coupled inductor boost chopper using only a passive auxiliary edge-resonant snubber circuit for further improvement in the total power conversion efficiency. The operating principle and the unique features of this new power conditioner are described and evaluated through a design example based on simulation results.

Pulse modulated AC voltage regulator using bidirectional active switches with different control strategies

In this paper, a comparative study of modified phase-angle, extinction-angle, and pulse width modulation control techniques for the purpose of power factor improvement of single-phase AC-AC voltage regulators have been illustrated as applied to a single-phase AC voltage converter by an example of the widely used single-phase induction motor as a dynamic load. Observations on power factor, displacement factor and total harmonic distortion factor are described and discussed on the basis of the simulated and measured results of this work

Novel High Frequency Planner Transformer Linked Soft Switching DC-DC Power Converter with Secondary Side-Phase Shifted PWM Active Rectifying Switches

This paper presents a novel circuit topology of isolated DC-DC power converter, which includes stable and efficient zero voltage soft switching (ZVS) full bridge inverter in the high frequency planner transformer primary-side and zero current soft switching rectifier in its secondary side. This power converter incorporates zero current soft switching (ZCS) phase-shifted PWM controlled two active power switches in series with either right or left leg of full-bridge of a transformer secondary-side. The proposed soft switching DC-DC power converter can achieve a wide soft-switching commutation under wide load variations from an extremely light load to a heavy load at a condition of a constant frequency phase-shifted PWM voltage regulation and high efficiency voltage regulation due to reduced circulating current in the primary side of the transformer. Its operating principle in steady state is described and its performances are evaluated and discussed based on simulation analysis and experimental results obtained on a 2 kW and 40 kHz breadboard power converter setup. The practical effectiveness of this soft-switching DC-DC power converter with a high frequency link is proven on the basis of simulation and experimental results

Dual utility AC voltage line operated soft switching PWM DC-DC power converter with high frequency transformer link for arc welding equipment

This paper presents two new circuit topologies of DC busline series active snubber assisted soft switching PWM full-bridge DC-DC power converter acceptable for either utility AC 200 V-rms or AC 400 V-rms input voltage source. Proposed power converters are composed of a typical voltage source full-bridge high frequency PWM inverter using DC busline side series switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutation operation and consequently the total turn-off switching losses can be significantly reduced. As a result, a high switching frequency for used IGBTs can be actually realized more than about 20 kHz. It is proved that the more the switching frequency of full-bridge inverter increases, the more soft switching PWM DC-DC power converter with a high frequency transformer link has remarkable advantages for its power conversion efficiency and power density as compared with the conventional hard switching PWM inverter type DC-DC converter. The effectiveness of this new converter topology is proved for low voltage and large current DC-DC power supplies as arc welding machine from a practical point of view