Study Of Rwandan Grid-Connected Variable Speed Small Scale Hydropower Plants

Rwanda is known as the country of thousand hills, and it is also the country of numerous rivers that flow down these hills which can be tapped to generate electricity. Despite this enormous exploitable hydropower potential in this country, but it has one of the lowest hydropower utilization rates in general and insufficient power generation capacity in particular. This problem has been putting a curb on the development of the country. To mitigate the electrical power deficit, low-cost additional power plants must be established.As one of the mainstream clean and renewable energy, small scale hydro are low initial and running cost, but vulnerable to water flow and should be deliberately controlled. If Rwanda exploits all its small scale hydropower sources at maximum efficiency, not only the electrical power generation capacity will increase but also the power production cost will decrease and hence the number of population accessing electrical energy will also increase. Besides, there will be a greenhouse gas emission reduction in conformity with the Kyoto Protocol.The variable speed operation is a good solution to optimal exploitation of these small scale hydropower plants in Rwanda. Water flow in many rivers is being decreased to critical levels, resulting firstly in low power production capacity; secondly in out of service of some power plants designed to run at fixed speed. Cyclo-converter permits variable speed functioning in order to optimize the turbine working point so that the power plant works at maximum efficient for any flow of water.The paper firstly concentrates on assessment of hydro-power potential and its exploitation as CDM projects; secondly the research assesses the steady state behavior of power network when a variable speed small scale hydropower plant is connected to it. Thirdly, the behavior of the system when the grid is under temporary three phase to ground fault is also assessed. Besides literature review, the matlab/Simulink software is used to accomplish the aforementioned tasks.