In order to overcome the above mentioned problems, multilevel inverter came into picture and attracted more attention because of their significant properties. They offer lower total harmonic distortion (THD), low dv/dt device switch voltage stress, lowering the switch voltage and power rating etc. The multilevel inverter is well suited for high power medium voltage applications and in particular dominated by cascaded multilevel inverter and neutral point clamped multilevel inverter.
In these medium voltage applications cascaded multilevel inverter and neutral point clamped multilevel inverter requires transformer to obtain electrical isolation between active DC sources of the H-bridge or NPC converter cells. This condition introduces losses, increases converter footprint, making converter costly, bulky and complex. The main drawback of the cascaded multilevel converter coupled with the transformer makes circulation current between phase during unbalanced network conditions and it may cause asymmetrical phase voltages.
The modular multilevel inverter has strong potential to replace cascaded multilevel converter in medium voltage applications . This paper, presents the design of a solar photovoltaic power conversion system with single stage modular multilevel converter. Currently intensive research is going on in MMC and it has high potential for medium power applications. Modular multilevel converters have several advantages over conventional multilevel topologies. Those significant are as follows. • Generate low harmonic output voltage, this eliminates filtering requirements. • For medium voltage application, it allows to avoid interfacing transformer. Modular structure allows to extend higher number of levels easily. •
Contents 1. Introduction 1. 1 The Fundamental Problem of Communications 51. 2 The Transmission Medium-Attenuation Constraints 91. 3 The Transmission Medium- Interference Constraints 121. 4 The Transmission Medium- Bandwidth Constraints 131.5 DSL Keeps Unshielded Twisted Pair (UTP) Copper Cable Attractive as a Premises Transmission Medium 181. 6 A Brief History of DSL 211. 7 Program 222. xDSL ...
Capacitor voltage balancing is attainable independent of the load. Although MMC are investigated with many applications, but it has not been reported in the literature with single stage solar PV power conversion system. This paper demonstrates the effective implementation of the photovoltaic supported MMC for grid interface which satisfy all the control objectives like maximum power transferring under varying environmental conditions, synchronizing grid utility voltage with output current for unity power factor operation and low total harmonic distortion.
Ssection II gives introduction about Abstract— This paper makes an attempt to develop grid connected solar photovoltaic array power conversion using modular multilevel converter. The proposed system makes use of single stage power conversion with maximum power point tracking and modular multilevel converter (MMC) as interfacing unit into the grid. Here perturb & observe method of maximum power point algorithm is used to regulate the DC link voltage of the MMC and to synchronize the grid utility voltage with the current for attaining near unity power factor operation under varying environmental conditions.
Among various renewable energy resources such as solar, wind, tidal, geothermal, biomass etc. , the solar photovoltaic system being more attractive and promising green resource because of its abundant availability, safe resource, cost free and eco-friendly . The solar photovoltaic (PV) modules directly converts the light energy into the electrical energy, but energy obtained from the PV module acts as low voltage DC source and has relatively low conversion efficiency. In order to improve the efficiency and convert low voltage DC source into usable AC ource, the power electronics converters are used to transform DC into AC. Conventional inverter topologies such as voltage source inverter (VSI) and the current source inverter (CSI) are being utilized to convert solar power generated electrical power into the utility grid. Whereas these topologies require additional DC/DC converter stage resulting in a two stage power conversion and also require interfacing transformer to inject power into the grid. These topologies not only increase the circuit complexity but also increase the cost and space requirements.
INTRODUCTION “Because we are now running out of gas and oil, we must prepare quickly for a third change, to strict conservation and to the use of coal and permanent renewable energy sources, like solar power.” – JIMMY CARTER, televised speech, Apr. 18, 1977 In times such as today, cumulative solar energy production accounts for less than 0.01% of total Global Primary Energy demand. And the ...