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Micro-grid is defined as a local power network with distributed energy resources (DERs) as micro-power sources scattered throughout the supply area. For reliable and short range transmission of power, micro-power sources are controlled as standalone as well as grid-synchronized power sources. The idea is to design a resilient, efficient and cost effective infrastructure based on advanced communication...
Microgrid(μG) is a concept of feeding local loads incorporating Renewable Energy Source and energy storage systems through inverters to maintain a local power system near to the load center. Microgrid should work both in presence and absence of grid to increase the quality, reliability and efficiency of power delivery. Inverters used in Microgrid have to work in both grid tied and standalone mode...
Energy generation via Photovoltaic (PV) technologies has increased in the last years. Large scale PV generation have attracted interest among countries due to low operation cost and wide PV resource disposition. However, some operative challenges in large scale PV plants had been detected: power imbalance, low power quality in terms of total harmonic distortion (THD), power factor and conversion efficiency,...
Battery energy storage system(BESS) connected to the grid by power conversion system(PCS). Currently Cascaded Multilevel Converter(CMC) and Modular Multilevel Converter (MMC) are two more advanced topologies for PCS. This paper compares CMC and MMC topologies in aspects of efficiency, harmonic characteristics, reliability, control system complexity and cost, the simulation results are presented. Suggestions...
Photovoltaic systems are a widespread form of green energy, that is becoming increasingly considered also as a form of economical investment. Their reliability is consequently becoming a concern. In this paper we focus on the reliability of the DC-AC converters (inverters) of photovoltaic (PV) systems. We analyze the effects of the faults likely to affect their operation in the field. We show that...
Current energy paradigm of mixed renewables seems to urgently require reactive power provision at various feed-in points of the utility grid. Photovoltaic (PV) inverters are able to provide reactive power in a decentralized manner at the grid-connection point even outside active power feed-in operation, especially at night. This serves as a motivation for utilizing the PV inverters at night for reactive...
In this paper a new control method is introduced for grid-connected inverter (GCI) to inject sinusoidal current to grid in presence of nonlinear load and distorted grid voltage conditions. The proposed control method consists of two parts: current reference generation and current controller. To generate current reference, a new algorithm, based on Recursive Discrete Fourier Transform, is proposed...
In large drive applications load-commutated inverters (LCIs) are one of the most used technologies, mainly because of their excellent reliability records. However, LCIs are known to generate interharmonics. They can interact with the mechanical system at torsional natural torsional frequencies of the rotating train, both on the inverter and on rectifier side in weakly connected power systems, such...
In high-power electric drives the use of multiple three-phase stator windings, supplied by voltage-source PWM inverters, is a design strategy for power rating, performance and reliability enhancement. Possible drawbacks, highlighted in the literature, come from the high-frequency circulation currents that originate in motor phases due to PWM switching. When a synchronous machine is used as the motor,...
This paper analyses the mathematic model of multiphase induction motor, and the magnetic motive force generated by the harmonic currents. Compared to three phase drives, the multiphase motor drives have the advantage of performances on dead-time effect, common mode voltage, technology of non-sinusoidal source fed and reliability. A universal multi-phase voltage source inverter (VSI) is constructed...
New York City has set a goal to increase its installed photovoltaic (PV) capacity from 1.1 MW in 2005 to 8.1 MW by 2015. A key barrier to reaching this goal, however, is the complexity of the interconnection process on secondary network distribution systems (network). Although most areas of the country use simpler radial distribution systems to distribute electricity, many larger metropolitan areas...
UPS provides emergency power when utility power is not available, so the reliability of UPS is more important than inverter drive systems. In this paper, a fault diagnosis system for UPS is proposed using FFT frequency analysis of output current of inverter side of UPS under linear and nonlinear load conditions. Software PLL for precise synchronization of one period sampling and double buffer memory...
This paper presents a control scheme based on random switching hybrid nonsinusoidal PWM (RS-HNSPWM) in stand-alone inverter-based distributed generation source to regulate and produce a sinusoidal voltage at the point of common coupling (PCC). Due to the nonlinear currents, drown by the nonlinear loads, VPCC becomes nonsinusoidal. The proposed controller takes VPCC as an input and generates a nonsinusoidal...
Pulse width modulated (PWM) inverter can generate common-mode voltage (CMV) which will decrease the system reliability. Firstly, some theoretic analysis and experimental results validate the characteristics of CMV and its adverse effects in this paper, and the methods for its cancellations are also presented. Then a novel inverter output active filter based on a single-phase inverter and a five-winding...
In a motor-drive system, there are many factors which can be considered as a figure of merit in drive control algorithm. All of these factors should be evaluated simultaneously to achieve the reliable performance of drive. In this paper, an optimization problem is constructed on a direct torque controlled induction motor drive using a candidate from different parts of drive system: inverter loss from...
This paper presents the Z - source inverter for adjustable speed drive system. The Z - source inverter employs a unique impedance network couple with inverter main circuit. By controlling the shoot through duty cycle, the Z - source inverter system using MOSFETS provide ride - through capability during voltage sags, reduces line harmonics, improves power factor and high reliability, and extends output...
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