Fuel cell stacks and photovoltaic panels generate low DC voltages and these voltages need to be boosted before converted to AC voltage.
In addition, the voltage stresses on the main switch and Output diode are reduced by a passive clamp circuit; so therefore low resistance RDS (ON) for the main switch can be adopted to reduce conduction loss.The key factors for renewable energy power conversion systems in industrial applications are Efficiency, power quality, and reliability. Du 3 suggested a novel scheme to improve performances of high-voltage large-capacity photovoltaic power stations. The power transformation of photovoltaic framework is separated into two phases, i.e. photovoltaic system is divided into two stages, i.e. DC/DC power conversion and DC to AC power conversion.
In DC to DC stage, many power units are connected in parallel, each one of which includes a photovoltaic array and a non isolated DC/DC converter. The DC to AC power conversion is equivalent to a voltage source in series with a current source.A family of a single-switch three-diode dc–dc pulse width-modulated (PWM) converters operating at constant frequency and constant duty cycle is presented by Ismail 4. They described that the converters are different from the conventional DC–DC step-up converters, and they posses very higher voltage gain with small output voltage ripples. In any case, A high advance up converter with high advance up pick up and low diode voltage push, reasonable for green power source change by utilizing a coupled inductor and exchanged capacitor, accomplishes high advance up transformation proportion without embracing greatly high obligation proportion or high turns proportion. The voltage spike that occurs on the power switch is alleviated allowing a low-voltage-rated power switch with low RDS(ON) and thus reduces the conduction losses is presented by Kuo-Ching Tseng5,6,13.
High Step-Up Trans-Inverse (Tx-1) DC–DC Converter for Distributed Generation System is presented by Yam 7. The topology utilizes magnetic coupling for boosting its output voltage, unlike other converters with coupled magnetic and voltage gain is increased by reducing its magnetic turn’s ratio. The name “Trans-inverse (Tx-1)” is used for representing this inverse operating principle of the converter. The converter draws a continuous current from the source, and suitable for many types of renewable sources. Its leakage energy from the coupled magnetic has further been recycled and transferred to the load by an integrated regenerative snubber circuit. Moreover, the use of DC-current-blocking capacitors has also helped to prevent core saturation.
Ching 8 Proposed a novel high step-up converter for fuel-cell system applications. They illustrated a two-phase version configuration. Initial, an interleaved structure is adjusted for diminishing information and yield swells . Then, a Cuk-type converter is integrated to the first phase to achieve a much higher voltage conversion ratio and avoid operating at extreme duty ratio. Also, extra capacitors are included as voltage dividers for the two stages for diminishing the voltage worry of dynamic switches and diodes. A novel two-switch high-step-up isolated converter with voltage lift is proposed by Liang 9 .In this paper; the proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain.
A novel high step-up dc/dc converter is presented for renewable energy applications 10. The energy stored in the leakage inductance is recycled with the use of a passive clamp circuit. The voltage stress and the conduction losses power switch are reduced.Review of Non isolated High-Step-Up DC/DC Converters in Photovoltaic Grid-Connected Applications is given by Li11.He suggested in the residential PV grid-connected system, the PV parallel connected configuration can be employed rather than the series connected configuration due to the safety and the PV array utility rate consideration.
Moreover, the non isolated high-step up converters are introduced in order to reduce the system cost and to improve the converter efficiency since the common mode current with the large PV area in these applications can be solved effectively. The limitations of the conventional boost converter in high-step-up, low-cost, and high-efficiency PV grid-connected system are analyzed. Most of high-step-up topologies three level boost converter, Cascade boost converter, High step up boost converter with coupled inductor and switched capacitor, High step up interleaved soft switching converter are summarized and classified into several categories based on the circuit structure.
Interleaved High Step-Up ZVT Converter With Built-In Transformer Voltage Doublers Cell for Distributed PV Generation System is presented by Weichen Li12.In this paper, the concept of built-in transformer voltage doublers cell is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed built-in transformer voltage doublers cell is composed of three transformer windings, two voltage doublers diodes, and two voltage doublers capacitors.
The voltage doublers capacitors are charged and discharged alternatively to double the voltage gain. The switch obligation cycle and the transformer turns proportion can be utilized as two controllable flexibilities to lift the voltage proportion adaptable. The dynamic clamp scheme is received to reuse the spillage vitality, ingest the turn kill voltage spikes, and accomplish Zero-Voltage Switching operation for all dynamic switches.