Abstract
In this paper, concepts and methods of hybrid control systems are adopted to establish a hierarchical dynamic automatic voltage control (HD-AVC) system, realizing the dynamic voltage stability of power grids. An HD-AVC system model consisting of three layers is built based on the hybrid control method and discrete event-driven mechanism. In the Top Layer, discrete events are designed to drive the corresponding control block so as to avoid solving complex multiple objective functions, the power system’s characteristic matrix is formed and the minimum amplitude eigenvalue (MAE) is calculated through linearized differential-algebraic equations. MAE is applied to judge the system’s voltage stability and security and construct discrete events. The Middle Layer is responsible for management and operation, which is also driven by discrete events. Control values of the control buses are calculated based on the characteristics of power systems and the sensitivity method. Then control values generate control strategies through the interface block. In the Bottom Layer, various control devices receive and implement the control commands from the Middle Layer. In this way, a closed-loop power system voltage control is achieved. Computer simulations verify the validity and accuracy of the HD-AVC system, and verify that the proposed HD-AVC system is more effective than normal voltage control methods.
Highlights
With the ever-expanding scale and increasing complexity of power systems since 1960s–1970s, theories and technologies of automatic voltage control (AVC) aimed at secure, stable and economical operation of the whole power system have become important research subjects [1,2].Currently, research on voltage control mostly focuses on power systems in a static status with stable operation, under the circumstances of which only slight voltage control adjustments are made so as to realize a certain function or certain indicators
Traditional secondary voltage control applied to all the generators; hierarchical control applied to all the generators, with certain load-shedding and reactive power devices taken into consideration at the same time
The reactive load in each load bus is evenly doubled from second 0 to second 60. Under such circumstances the three following programs are studied by comparison: traditional AVR control applied to all the generators; 2 traditional secondary voltage control applied to all the generators;
Summary
With the ever-expanding scale and increasing complexity of power systems since 1960s–1970s, theories and technologies of automatic voltage control (AVC) aimed at secure, stable and economical operation of the whole power system have become important research subjects [1,2]. If the variation range and variation rate of the system voltage exceed the permitted limits, appropriate control measures are necessary to ensure the dynamic voltage quality and system security. This is referred to as dynamic voltage control. To realize dynamic voltage stability control, concepts and methods of hybrid control system are introduced in this paper [6] to set up a hierarchical dynamic automatic voltage control (HD-AVC). A hybrid hierarchical control system model is set up, with the Top Layer analyzing the power system’s dynamic voltage stability, constructing discrete events to drive the corresponding control block, and generating and sending out control strategies to the Middle Layer in case the system security is “threatened”. In this paper an IEEE-22 bus system is adopted as an example for simulation research, verifying that the proposed system for dynamic voltage control is effective
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