Optimum Power Supply Schemes And Its Evaluation Method For County-level Power Grid With Abundant Hydropower Stations

In China, there are abundant hydro-power resources. However, a large number of distribution generators are built and interconnected into distribution network in county-level power grid. The generation capacity varied with the wet and dry seasons. And the amplitude of voltage in the grid changes largely and frequently. Then how to improve the quality of the power supply and the reliability is the needed research work in this thesis.From the perspective of improving the voltage quality and reliability and decreasing the power loss, in this thesis how the factors, such as different operation schemes of the hydro-power stations, irrational structure of the power grid impact on normal operation of the network are analyzed. The voltage, reactive power, losses and maxim short current of an example network are calculated. The technology of solving the difficulty in reactive power outputting is studied. Further the schemes for improving the voltage quality are put forward.Long transmission lines and lack of voltage regulator are the possible reasons why the reactive power outputting is restricted for hydro power units. Through research, we realize that single voltage regulating measurement applying in the network is not enough to satisfy the voltage quality and supply reliability requirements. Voltage regulating technology, voltage regulator combined with shunt reactors and capacitors together are effective to control the voltage and reactive in network with abundant small hydro power stations. Compare some simple technical and economical indices between proposed power supply schemes, the results showed that comprehensive utilization of voltage regulator and setting shunt capacitor are effective method to solve both the voltage and the reactive power problem in network with abundant small hydro power stations.