| Small hydropower is a kind of renewable green energy. The development of small hydropower plays an important role in China's economic and social development. Especially the characteristics of small hydropower protect the security of the regional electricity supply. However, because most of the small hydropower has the characteristics of being a hydropower station, power generation are affected by seasonal river. When the load also changes, there will be some problems accessing a large number of small hydro power operations. Especially when there is valley load in small water power high flow period, that is to say, a large number of hydropower generations with under load, which cause boosting bus voltage, even beyond the maximum amount.Reactive power and voltage of power network is an important problem which directly influences voltage quality of the system as well as which relates to economical operation of power network. During the previous calculation of reactive power and voltage in the power network, reactive power insufficiency and the system under-voltage are always concerned. In the same way, we should consider the problem that reactive power surplus and over-voltage during the period of high flow but under load.This paper analyzes the characteristics of small hydro power, focusing on the analysis of small water single net balance of reactive power and voltage stability problems, which mainly includes the following parts:(1) Voltage is too high in wet periods of low load part. Through analysis, calculation, testing and other means of system, a solution to voltage and reactive power has been proposed after research. In introducing the reactive power flow and voltage on the basis of the system theory of reactive power compensation, as well as focusing on the principle of compensation for reactive power and reactive power balance theory, it is introduced in this paper a variety of reactive power compensation equipment and performance characteristics, and a basis was provided under different network to use the appropriate reactive power control.(2) Analysis of the basic principles of leading phase Operation, phase operation of the generator of static stability, end flux leakage is theoretically analyzed and summarized. Reactive power calculation was figured out on the power network on condition that the loss minimum of the active power network was object function. Several optimizing compensatory schemes were put forward. Based on the calculation result and the analysis of all schemes, the most reasonable and feasible optimizing scheme could be achieved. Meanwhile, the feasibility that the system voltage could be adjusted was demonstrated. According to the experience of leading phase operation of the same type units and the suggestion of manufacturers, the generator excitation system was improved to ensure stable function of auto voltage adjusting device during lagging phase and leading phase operation. The experiment of leading phase operation and adjusting voltage of generator was carried on through electrical power plant. Based on the result, a thorough analysis was taken on the step-down effect, stable limitation, capability of absorbing reactive power when generator operating under excitation, which could be used as a foundation of generator operating under excitation.(3) Calculated by the actual power flow, a main network calculating equivalence model of power network was constructed. Proposed phase operation by generator, regulating transformer tap Shunt Reactor, three basic ways to control wet small water grid and load voltage are put forward.(4) Through analysis and calculation, obtained amount of the voltage regulator controls the amount of the sensitivity matrix equation...
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