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## Über dieses Buch

This book describes comprehensively theories and methods of the power system voltage stability. It first introduces the basic theory of the power system and the basic concept and classification of the power system stability and discusses the basic concepts of voltage stability, including the mechanism of voltage stability, and influencing factors of transient and medium-term and long-term voltage stability. This book also describes the elemental characteristics and models of important power system in voltage stability analysis and discusses the theories and methods of analysis on steady, transient and medium-term and long-term voltage stability analysis, respectively. Then, this book introduces the measures to improve the voltage stability. Finally, two examples of voltage stability analysis in engineering applications are introduced.
This book is useful as a reference for engineers and technicians who are engaged in dispatching operation, planning, design and scientific research of the power system, and teachers and students of electrical engineering major in colleges and universities.

## Inhaltsverzeichnis

### Chapter 1. Introduction

Abstract
Power is an important secondary energy, playing an irreplaceable role in the development of the national economy. Power safety is directly related to the national economy and social security.
Yong Tang

### Chapter 2. Introduction to Voltage Stability

Abstract
Voltage stability is a branch of power system stability that has developed late. In general, the research on voltage stability can be divided into three stages. In Stage I from 1940s when the first voltage stability criterion dQ/dU [1] was put forward by Malkovich, a Russian scholar, to the mid-1970s, insufficient attention was been paid to voltage stability. In Stage II from the late-1970s to the mid-1980s, attention was paid to the research on static voltage stability.
Yong Tang

### Chapter 3. Characteristics and Models of Power System Elements

Abstract
The electrical energy of the power system is mainly provided by synchronous generators.
Yong Tang

### Chapter 4. Static Analysis of Voltage Stability

Abstract
The static analysis method of voltage stability is to capture the system state on different time sections along the time track. By assuming that the differential of the system state variables on the section is zero, the differential-difference-algebraic equations describing the nonlinear dynamic power system are simplified to pure algebraic equations. Since the early voltage instability accidents are mostly the medium and long-term voltage instability processes, which have a long time span and are usually caused by slow load growth or system output power transfer, the static analysis method has become the mainstream of voltage stability research for a long period of time.
Yong Tang

### Chapter 5. Transient (Short-Term) Voltage Stability

Abstract
The dynamic behavior of power system can be summarized and reflected by the nonlinear differential-difference-algebraic equations (DDAE). The differential equations partially reflect the dynamic behavior of dynamic elements in the power system, the difference equations partially reflect the discrete actions of system elements, and the algebraic equations partially reflect the interaction between dynamic elements and topological constraints of the network in the power system.
Yong Tang

### Chapter 6. Medium and Long-Term Voltage Stability

Abstract
Medium and long-term voltage stability is the stability of a power system that is influenced by slow-changing elements (such as: OEL, OLTC action, power recovery characteristics of loads and others) and the slow changing process of the power system (such as AGC, load growth, operation mode adjustment and others) after the transient stability is guaranteed. The object of medium and long-term voltage stability analysis is the voltage phenomenon after transient time frame, the time range can be tens of seconds to tens of minutes even several hours, it studies the ability that the system reaches the acceptable operating equilibrium point state after disturbance.
Yong Tang

### Chapter 7. Technical Measures to Improve Voltage Stability

Abstract
Power system voltage stability is related to many factors, and different accident mechanisms may lead to voltage collapse accidents with different dynamic characteristics. Therefore, there are variable measures to prevent voltage instability, with different emphasis according to different voltage instability modes.
Yong Tang

### Chapter 8. Examples of Voltage Stability Analysis

Abstract
Big power grid operation as the sign of modern power industry brings self-evident economic effect. However, any accident may cause serious consequences. Therefore, safe operation of the big power grid is an important research subject for electric power workers both at home and abroad. Several typical voltage collapse accidents abroad are the profound warning for us in development of our power grid. In accordance with characteristics of interconnected power grid in China, the power grid structure becomes more and more complicated. There are more and more AC power transmission channels, or AC and DC power transmission channels in parallel for transmitting power intensively across different areas in long distances. The difference between peak and valley loads is enlarged with extensive application of new power transmission technology. Therefore, it is more and more difficult to regulate and control voltage; in some interconnected power grids, the risk probability of voltage collapse accident increases owing to coexistence of insufficient dynamic and reactive standby at center of the end load.
Yong Tang
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