Bruce Fardanesh

A governor/turbine model for a twin-shaft combustion turbine

A twin shaft gas turbine unit was tested for the governor response to disturbances. A computer simulation model is presented as well as the test data which was used to derive values for the model parameters. >

Field tests to validate hydro turbine-governor model structure and parameters

A test procedure was developed to obtain accurate governor models for hydroelectric stations owned by the New York Power Authority to improve the accuracy of stability simulations of the New York State system. Tests were performed on units at three stations and values for parameters of previously available model structures were derived from the information obtained during these tests. However, it was found that the model structures were not adequate to represent the entire range of operating conditions. Additional examination of test measurements and model structures indicated that the model structure needed to be refined. This paper reports on the refinements made to the hydro turbine-governor models which enabled reproduction of the physical system responses. Simulation results indicate that the refined models with the corresponding identified parameters produce responses which closely fit those recorded from the tests performed on three hydro units. >

Future trends in power system control

To buy time for online computations needed for central coordination and to attain wider-area objectives for optimum operation, one has had to resort to decomposition and, therefore, multilevel hierarchical control schemes. This article looks into the future state of power system operations and control based on a number of assumptions and provides an analysis of the direction that this area might take over the next 25 years. Issues related to development of techniques and requirements for fully coordinated, high-bandwidth, and robust controls for power systems are discussed, and some methodologies are suggested. Proceeding toward this ultimate goal, system-wide automatic voltage control (SAVC), system-wide automatic power control (SAPC), and the integrated system-wide automatic control (SAC) concepts are introduced for coordination of injection (shunt) and routing (series) controllers for both real and reactive power.

A common modeling framework of voltage-sourced converters for loadflow, sensitivity, and dispatch analysis

This paper discusses the use of injected shunt and series voltage sources to model voltage-sourced converters (VSC)-based FACTS controllers such as the unified power flow controller (UPFC) and the interline power flow controller (IPFC). Traditional power network models include only shunt voltage injections, and thus the inclusion of series voltage injections provides a new capability of power system models. In addition, the voltage injections are active devices, with reactive power injections when a VSC is operated independently, and also with active power injections when more than two VSCs are coupled. A Newton-Raphson loadflow solution and a network sensitivity analysis are developed based on this framework. The sensitivities can be used for optimal dispatch of FACTS controllers.

Power system state estimation: modeling error effects and impact on system operation

State estimation has been introduced to power systems and implemented in the 60s, using a single frequency, balanced and symmetric power system model under steady state conditions. This implementation is still prevalent today. The single frequency, balanced and symmetric system assumptions have simplified the implementation but have generated practical problems. This paper examines these simplified assumptions and their impact on the state estimation performance. It provides a theoretical basis for the well-known fact that the reliability of the state estimator algorithms has been below expectations. Specifically, sensitivity analysis methods are used to quantify the impact of modeling simplifications and measurement schemes on the performance of state estimation. The results clearly illustrate that the traditional state estimation algorithm is biased. These biases affect the accuracy of state estimation and its convergence characteristics.The paper also reviews the traditional state estimation approach against recent technological advances that have enabled synchronized measurements. The implications and possibilities of this new technology are discussed in this paper. Specifically, an example application of the new technology for a Three Phase State Estimator is described. A power system state estimation based on a) multiphase model, b) voltage and current waveform measurements, and c) synchronized measurements is formulated. The paper focuses on the following: a) modeling, b) implementation, c) observability and d) performance. The overall performance of the system is described in terms of confidence level versus error. These concepts are illustrated with simple systems. In addition, we demonstrate the performance of the proposed methods on an actual system (New York Power Authority system) using actual synchronized measurements. The paper concludes with a commentary on the implications of improved state estimation methods on the security/reliability monitoring and control of an electric power system.

Multifunctional synchronized measurement network [power systems]

In 1992, the New York Power Authority (USA) and the other Empire State Electric Energy Research Corporation member electric utilities initiated the deployment of a network of power system synchronized measurement units using phasor measurement technology on the New York State high-voltage transmission system. This article defines the current and future status of the measurement network, featuring its harmonics measurement and disturbance monitoring.

Transfer Path Stability Enhancement by Voltage-Sourced Converter-Based FACTS Controllers

Dynamic regulation models for voltage-sourced converter (VSC) based flexible ac transmission system (FACTS) controllers are described in this paper. The dynamic models can then be used to analyze these FACTS controllers capability to improve the capability of a power transfer path. The contributions of this paper include showing that the benefits of FACTS controllers are proportional to the MVA ratings and the benefits of multiple FACTS controllers are cumulative. Furthermore, the coupling of dc buses allowing active power circulation between multiple VSC FACTS controllers may offer additional improvement in transfer capability.

Phasor-Measurement-Based State Estimation for Synchrophasor Data Quality Improvement and Power Transfer Interface Monitoring

Validation and data quality improvement of phasor data through state estimation is the first step in ensuring that the synchrophasor data is useful for applications in monitoring, visualization, and control. This paper presents a phasor-measurement-based state estimator (PSE) for improving data consistency by identifying angle biases and current scaling errors in the phasor data using the augmented state vector approach. These errors can arise from issues with the Global Positioning Signal (GPS), timing circuits, instrument channels, and/or data channel scaling. The PSE is demonstrated using several sets of disturbance data from the Central New York Power System. The PSE can also provide estimates of line parameters and transformer tap ratios with sufficient measurement redundancy. Finally, the PSE allows the computation of interface power flows for disturbance and stability monitoring.

Thyristor controlled series compensation application study-control interaction considerations

A study of the potential for control interaction between a proposed thyristor controlled series compensation (TCSC) and an existing static VAr compensator (SVC) is presented. The results indicate that a control interaction exists between the voltage-input power swing damping control (PSDC) of the TCSC, the series compensated AC system resonances, and the SVC controls. The addition of recommended filtering and synthesized angle-input PSDC showed improved performance. >

Operating characteristics of the convertible static compensator on the 345 kV network

Convertible static compensator (CSC), a versatile device based on FACTS technology was designed, developed, manufactured, installed, and tested. The project was a collaborative undertaking by NYPA, EPRI and Siemens Power Transmission & Distribution. The CSC was installed on a 345 kV substation with series elements inserted in two 345 kV lines. The CSC consists of two 100 MVA inverters, two 100 MVA series transformers, and a single 200 MVA shunt transformer with two identical secondary windings. The CSC can be operated in four basic configurations: static synchronous compensator, static synchronous series compensator, unified power flow controller, and interline power flow controller. The CSC was tested under various system conditions and the test results are discussed and analyzed. The tests confirmed the actual power flow control characteristics of the CSC and their close correlation with the design parameters. The CSC utilization on NYPA network results in the increased power flow transfers and enhanced power flow control capability on Marcy-New Scotland and Marcy-Coopers Corners lines. The power flow on Marcy-New Scotland line can be varied by /spl plusmn/125 MW, and on Marcy-Coopers Corners line by /spl plusmn/80 MW.