X. Lei

Optimization and Coordination of Damping Controls for Improving System Dynamic Performance

This paper presents a global tuning procedure for FACTS device stabilizers (FDS) and power system stabilizers (PSS) in a multimachine power system using a parameter-constrained nonlinear optimization algorithm implemented in a simulation program. This algorithm deals with such an optimization problem by solving a sequential quadratic programming using the dual algorithm. The main objective of this procedure is to simultaneously optimize preselected parameters of the FDSs and PSSs having fixed parameters in coping with the complex nonlinear nature of the power system. By minimizing a nonexplicit target function in which the oscillatory rotor modes of the generators involved and swing characteristics between areas are included, interactions among the FACTS controls under transient conditions in the multimachine system are improved. A multimachine power system equipped with a TCSC and an SVC, as well as three PSSs, is applied to demonstrate the efficiency and robustness of the tuning procedure presented. The results obtained from simulations validate the improvement in damping of overall power oscillations in the system in an optimal and globally coordinated manner. The simulations also show that the stabilizers tuned are robust in providing adequate damping for a range of conditions in the system.

A large integrated power system software package-NETOMAC

The simulation system NETOMAC/sup (R)/ (Network Torsion Machine Control) offers a wide range of modern methods of analyzing and synthesizing electric power systems. In order to design individual elements of transmission systems or to perform stability calculations on large systems, it is possible to simulate electrical networks in the time domain and also, with the aid of eigenvalue calculations, to study the frequency domain too. These methods find general application in the design of control systems add in analyzing the behavior of large networks. User support is provided in the form of a graphical interface to facilitate the inputting of the electrical systems and control structures, One uniform database is being used for all calculations regardless of whether time domain or frequency domain is being investigated. Workstations, PCs or notebooks provide the platform from which NETOMAC can provide the user with the flexibility, mobility and speed that he needs.

Industrial approaches for dynamic equivalents of large power systems

Issues on the establishment of equivalent networks are becoming essential for the deregulated power market. This paper presents a comprehensive tool for network reduction of large power systems. Through integrating different metrologies into a simulation program, the dynamic equivalent can be established by adopting one common database. With a readily integrated modified Gauss-Newton algorithm, network reduction can be executed under the dynamic conditions either in the time domain or in the frequency domain in coping with nonlinear nature of the system involved. Furthermore, a novel algorithm based on dynamic coherency approach implemented readily into the simulation program is also presented. This novel approach determines coherent generators on nonlinear basis in the time domain using the cross correlation technique, taking dynamic characteristics of the system involved into consideration. Two case studies are presented in this paper. Each of the nonlinear approaches presented is applied for one of the case studies as an application example. The results achieved validate the functionality of the approaches presented.

Optimization-a new tool in a simulation program system [for power networks]

In this paper an optimization tool in the simulation program system NETOMAC is presented. The motivation is to provide users with a simple and efficient way of flexibly solving various optimization problems arising in power systems. The most attractive features of the optimization within the simulation program system are that: (1) an objective function and all constraints related can be implicitly formulated with the block-oriented simulation language; and (2) the performance of various optimizations does not need any modification to the source program. Three improved optimization algorithms have been implemented. These algorithms have been developed in a real problem-oriented way. They are efficient and robust in practical applications. Capabilities of the optimization tool implemented are demonstrated in this paper by solving four optimization problems arising in power systems.

Optimization and coordination of damping controls for improving system dynamic performance

Summary form only given as follows. This paper presents a global tuning procedure for FACTS device stabilizers (FDS) and power system stabilizers (PSS) in a multimachine power system using a parameter-constrained nonlinear optimization algorithm implemented in a simulation program. This algorithm deals with such an optimization problem by solving a sequential quadratic programming using the dual algorithm. The main objective of this procedure is to simultaneously optimize preselected parameters of the FDSs and PSSs having fixed parameters in coping with the complex nonlinear nature of the power system. By minimizing a nonexplicit target function in which the oscillatory rotor modes of the generators involved and swing characteristics between areas are included, interactions among the FACTS controls under transient conditions in the multi-machine system are improved. A multi-machine power system equipped with a TCSC and an SVC as well as three PSSs is applied to demonstrate the efficiency and robustness of the tuning procedure presented. The results obtained from simulations validate the improvement in damping of overall power oscillations in the system in an optimal and globally coordinated manner. The simulations also show that the stabilizers tuned are robust in providing adequate damping for a range of conditions in the system.

Advanced solutions for power system analysis-computer study and real-time simulation

Successful operation of a power system depends largely on the engineers ability to provide safe, reliable and economic service to the customer. Advanced simulation technologies provide useful means to the engineer for the design and analysis of the power system, and assisting them in making reasonable decisions. Due to powerful software and advanced real-time simulators, it became possible to simulate the dynamic behavior of very large power systems including HVDC and FACTS, and to verify the performance of these complex systems with the original control and protection equipment in a fast and accurate manner. The simulation covers stages of development and operation of a power system, such as planning, design, test and also during operation. In this paper advanced software and real-time power system simulation technologies are presented. With practical examples benefits of the simulation for large power systems are also demonstrated.

Coordinated operation of HVDC and FACTS

Over the course of three decades of commercial applications, the HVDC technique has been established as a conventional technology in the area of back-to-back and two-terminal long-distance and submarine cable systems up to 2000 MW and higher. As thyristor-controlled shunt compensation schemes have been introduced into high-voltage transmission for more than two decades, FACTS (flexible AC transmission systems) devices are established as technical and economic means for improving the overall system performance of AC systems. Today, only limited HVDC and FACTS systems are operated in a coordinated manner. However, with increasing complexity of system conditions, e.g. in very weak power systems with enhanced stability requirements, parallel operation of HVDC and FACTS devices is gaining impetus. Innovative technologies can further optimize the HVDC performance under weak and very weak system conditions.

A comprehensive simulation program for subsynchronous resonance analysis

Subsynchronous resonance (SSR) is a condition that can exist in a power system, especially for long distance transmission systems with series compensated line. It can cause shaft fatigue and possible damage or failure of the generator involved. The analysis of the SSR phenomena can be performed usually by using three individual analytical methods-frequency scanning, eigenvalue analysis in the frequency domain and transient torque analysis in the time domain. In this paper the comprehensive simulation program NETOMAC with a complete solution for analyzing SSR is presented. Based on a common data set of the system concerned, both frequency and transient torque analysis can be performed, taking interactions among the spring-mass system of the turbine-generator units and the electrical network into consideration. Two case studies are demonstrated in the paper. The results achieved validate the functionality of the program for SSR analysis.

Analyzing subsynchronous resonance using a simulation program

Subsynchronous resonance (SSR) is a condition that can exist in a power system, especially for long distance transmission systems with series compensated line. It can cause shaft fatigue and possible damage or failure of the generator involved. The analysis of the SSR phenomena can be performed usually by using three individual analytical methods-frequency scanning, eigenvalue analysis in the frequency domain and transient torque analysis in the time domain. In this paper the comprehensive simulation program NETOMAC with a complete solution for analyzing SSR is presented. Based on a common data set of the system concerned, both frequency and transient torque analysis can be performed, taking interactions among the spring-mass system of the turbine-generator units and the electrical network into consideration. Two case studies are demonstrated in the paper. The results achieved validate the functionality of the program for SSR analysis.

FACTS for innovative power transmission system

During past decades, power systems have developed to complex interconnected systems. The interconnections by AC or DC offers technical and economical advantages. However, depending on system configuration also problems can arise. Power electronics for high voltage networks (FACTS) can improve these problems in an economic way. This report covers the development and application of FACTS controllers.