The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

Bidirectional dual-bridge dc/dc converter with high frequency isolation is gaining more attentions in renewable energy system due to small size and high-power density. In this paper, a dual-bridge series resonant dc/dc converter is analyzed with two simple modified ac equivalent circuit analysis methods for both voltage source load and resistive load. In both methods, only fundamental components of voltages and currents are considered. All the switches may work in either zero-voltage-switching or zero-current-switching for a wide variation of voltage gain, which is important in renewable energy generation. It is also shown in the second method that the load side circuit could be represented with an equivalent impedance. The polarity of cosine value of this equivalent impedance angle reveals the power flow direction. The analysis is verified with computer simulation results. Experimental data based on a 200 W prototype circuit is included for validation purpose.

Analysis and Design of High-Frequency Isolated Dual-Bridge Series Resonant DC/DC Converter

Unfilled gap of prolonged energy demand by conventional energy sources and consent of global warming as its vulnerable outcome provides a vent to search compatible option. Augmentation in use of solar energy reveled through last 3 decades portrays its heterogeneous rewards in the prevailing energy scenario. Nevertheless solar PV system arises as viable option in the critical power system era its low efficiency energy conversion attribute necessitates an efficient power conversion system. The nonlinearity of I–V (current–voltage) characteristic and its alteration for an assorted insolation and temperature values may enable the alteration in terminal voltage. This may deviates maximum power point due to which the available maximum power delivery to load can be differed. Literature of this field reiterated that the uniform insolation and partial shading condition demands undeniable need of maximum power point tracking. Nonetheless through investigation in this direction furnishes the availability of a bunch of such techniques; each of them posses its own pros and cones. This ubiquitous trait of available maximum power point tracking (MPPT) techniques unfolds the complexity in its precise selection. To diminish such complexity this paper offers a state of art of various MPPT technique and their comprehensive comparative analysis based on 110 standard research articles. The focus of this paper is to offer a better commencement and to furnish valued information for investigators of this field.

Maximum power point tracking (MPPT) techniques: Recapitulation in solar photovoltaic systems

Maximum power point tracking (MPPT) is an integral part of a system of energy conversion using photovoltaic (PV) arrays. The power-voltage characteristic of PV arrays operating under partial shading conditions exhibits multiple local maximum power points (LMPPs). In this paper, a new method has been presented to track the global maximum power point (GMPP) of PV. Compared with the past proposed global MPPT techniques, the method proposed in this paper has the advantages of determining whether partial shading is present, calculating the number of peaks on P – V curves, and predicting the locations of GMPP and LMPP. The new method can quickly find GMPP, and avoid much energy loss due to blind scan. The experimental results verify that the proposed method guarantees convergence to the global MPP under partial shading conditions.

An Improved MPPT Controller for Photovoltaic System Under Partial Shading Condition

String inverter photovoltaic (PV) systems with bypass diodes require improved global maximum power point tracking (GMPPT) algorithms to effectively reach the absolute maximum power operating point. Several GMPPT algorithms have been proposed to deal with this problem, but most of them require scanning wide voltage ranges of the PV array from nearly zero voltage to open-circuit voltage that increases the scanning time and, in turn, causes energy loss. This paper presents a novel GMPPT method which significantly restricts the voltage window search range and tracks the global power peak rapidly in all shading conditions. Simulation tests and experimental comparisons with another GMPPT algorithm are presented to highlight the features of the presented approach.

Global MPPT Scheme for Photovoltaic String Inverters Based on Restricted Voltage Window Search Algorithm

Seven indicators variations for multiple PV array configurations under partial shading and faulty PV conditions

This study describes a new application of flying capacitor multi-level inverters whereby a three-phase, four-leg three-level inverter is used for harmonic current cancellation and unbalanced current compensation in a four-wire system. A direct three-dimensional-pulse-width modulation (3D-PWM) scheme is developed to deal with the increased state redundancy in the four-leg flying capacitor multi-level inverter. Test results show much superior performance in the four-leg case, which may allow the use of smaller DC supply capacitors. A new modified dead-beat current control algorithm is proposed and combined successfully with the 3D-PWM modulation technique in a hardware demonstrator of a complete active filter.

/pdf/three-phase-four-leg-flying-capacitor-multi-level-inverter-2wmvarrg0l.pdf

Benjamin Chong

Papers

Seven indicators variations for multiple PV array configurations under partial shading and faulty PV conditions

Three-phase four-leg flying-capacitor multi-level inverter-based active power filter for unbalanced current operation

Controller design for integrated PV-converter modules under partial shading conditions

Multilevel DC-Link Converter Photovoltaic System with Modified PSO Based on Maximum Power Point Tracking

Maximum power exploitation for grid-connected PV system under fast-varying solar irradiation levels with modified salp swarm algorithm