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Off-grid solar photovoltaics (PV) are promoted as an economical renewable energy system for providing electricity in remote locations far from the grid. However, without on-going maintenance, the performance of these systems will diminish due to battery deterioration leaving them unable to provide the service they were initially designed for. This paper presents analysis and results from a four week cross-disciplinary investigative study carried out in September 2012 into the performance of off-grid PV in health centres and schools in rural communities in Rwanda. A socio-technical approach was taken to understand the reasons for failure. A strategy was subsequently developed to influence user behaviour and increase the PV array size to reduce capacity shortage through the year and improve the lifetime of the lead acid batteries found on these systems. According to the results obtained, the total costs to implement off-grid PV systems can be reduced. Furthermore, the proposed strategy reduces the operating costs of PV below that of a diesel generator according to a projection of prices found in Rwanda which is important in a donor led installation model. [ABSTRACT FROM AUTHOR]

Different faulty states of a doubly fed induction generator (DFIG) connected to a microgrid are investigated in this paper. First, the simulation model consisting of two DFIGs connected to IEEE 34-bus test feeder for two vector control based was set up to investigate the transient performance of the microgrid. Then, different types of faults of the DFIGs, including partial loss of excitation (PLOE), complete loss of excitation (CLOE), and interturn short circuit (ISC) were analyzed through the simulation model using vector control strategy. The experimental results indicate that the active power will increase during the PLOE, and the average increase of the amplitude is about 26%, which will decrease the electromagnetic torque by 8% and increase the voltage at the neighbor node, the stability of the microgrid will be broken eventually. For the CLOE, the active power decreases about 80%, and node voltage decreases by 9.4% due to the inverse absorption of the reactive power. When the ISC occurs, the average node voltage and the active power decrease together. Finally, the suggestion for the detection of the DFIG faults is presented, which could be helpful to protect the DFIG from fault accident. [ABSTRACT FROM AUTHOR]

Expansion of photovoltaic (PV) generation is increasing the challenge for network operators to keep voltages within operational limits. Voltage rise occurs in low voltage (LV) networks when distributed generators export, particularly at times of low demand. However, there is little work quantifying the scale of voltage issues and subsequently potential solutions across large numbers of real networks. In this paper, a method is presented to analyse a large quantity of geographically and topographically varying distribution networks. The impact of PV on voltages in 9163 real LV distribution networks is then quantified. One potential mitigation measure is increased network demand to reduce voltages. In this work, location algorithms are used to identify where increased demand, through energy storage, has the greatest effect on overvoltage. The study explores the impact on overvoltage of two modes of storage installation reflecting differing routes to adoption: purchase of storage by homeowners and purchase by network operators. These scenarios are compared with traditional re-conductoring in the 9163 networks. It is shown that to avoid violation of absolute voltage limits, storage should be installed at strategically important locations. Storage in homes reduces overvoltage, offering clear benefits to the network operator, but very wide deployment is required to completely remove the need for reinforcement. [ABSTRACT FROM AUTHOR]