随着我国经济的快速发展，电力负荷增长迅猛，电力供不应求，同时也对供电可靠性和供电质量提出了更高的要求。配电网是电力系统的最后一个环节，直接向用户供电，与用户联系最为紧密。由于配电网具有供电半径大、降压层次多和自动化水平低等特点，往往使得末端用户的电压质量无法得到保证。因此必须对配电网进行电压无功控制，配电网电压无功控制是保证电力系统安全经济运行的一个有效手段，是降低网损、提高电压质量的重要措施。 本文对配电网电压无功控制的现状进行了分析，指出了其中存在的问题，并对配电网低电压问题产生的原因进行了详细分析。重点研究了改变有载调压变压器的变比、无功补偿装置的投切容量对电压、功率因数以及有功损耗的影响。分析了传统变电站基于九区图的电压无功控制策略，并给出了数学模型。 传统的配电网电压无功控制一般只能实现局部的电压无功优化，容易出现变电站低压侧母线电压处于合格区间范围，配变调节手段已用尽，而用户电压仍越限的情况。在变电站电压无功控制原理的基础上提出了配电网电压无功三级联调控制算法，电压无功上下限的确定原则遵循变电站的九区图控制策略，电压无功控制目标为全局节点电压偏移度最小。配电网电压无功三级协调控制是利用配电网实时运行数据，即配电网运行参数以及各个可控变量的状态和裕度，然后经过优化计算，得出各个可控变量的调整措施，通过前推回代法预判调控方案对各节点电压的影响，计算出电压偏移度，然后根据电压偏移度最低的原则挑选出满足要求的方案，如果方案数大于1，那么按功率因数最优原则和有功损耗最小的原则删选出最优方案。 最后将配电网三级联调算法运用到某一配电网，取得较好的控制效果和经济效益，最大程度上改善了用户电压，并同时改善了功率因数，降低了有功损耗。

With rapid economic development, the power load is growing rapidly, power is of shortage, and higher requirements are needed for keeping power supply reliability and quality. Distribution network is the last part of the power system, and power is supplied directly to the user, which is most closely linked with the user. As the distribution network with a large radius, with levels of transforming voltage, and with low level of automation, those often make that the enduser's voltage quality can not be guaranteed. It is necessary to control voltage and reactive power of the distribution network. The control of voltage and reactive of distribution network is an effective means to ensure safe and economic operation of power systems, also are important measures to reduce network losses and improve voltage quality. This paper introduces and analyzes the latest status of voltage and reactive power control of the distribution system, which pointes out the problems. Then this paper has a detailed analysis on the reasons that causes the problem of low voltage of distribution network. Reactive power control works by changing the on-load tap transformer turns ratio, reactive power compensation device switching capacity to achieve change in voltage, power factor and power loss. Then this paper describes the traditional voltage and reactive power control strategy of substation based on nine-area diagram, and gives the mathematical model. The traditional distribution network reactive power control is generally achieved only partial optimization of voltage and reactive power, so it has certain limitations, prone to accrue that substation’s bus of low voltage side is qualified, but distribution transformer is unable to adjust, while the user’s voltage still exceed the limited voltage. Distribution network voltage and reactive power coordination control of three levels algorithm is on the basis of the substation voltage and reactive power control strategy. The upper and lower limits of voltage and reactive power are determined according to the principles of substation’s the nine zones control strategy, and the objective of voltage and reactive control is minimum voltage offset of all global nodes. Coordination and control of voltage and reactive power of distribution network used real-time operating data of distribution network, that is, grid operation parameters and state of controllable variables and the margin. Adjust the various controllable variables, and judges the effect of the regulation program on each node voltage, then calculate out the voltage offset, then select the scheme that meet the requirements of minimum voltage offset. If the program number is more than one, then choose the best scheme by the principle of optimal power factor and minimum power loss. Finally, apply the algorithm to two real distribution networks, which obtains better control results and economic benefits, and improve the users' voltage to the maximum extent and improve the power factor, and reduce the power loss at the same time.