Showing papers by "Surya Santoso published in 2009"

Bridging the gap between signal and power

Abstract: This article focuses on problems and issues related to PQ and power system diagnostics, in particular those where signal processing techniques are extremely important. PQ is a general term that describes the quality of voltage and current waveforms. PQ problems include all electric power problems or disturbances in the supply system that prevent end-user equipment from operating properly.

Impact of pulse loads on electric ship power system: With and without flywheel energy storage systems

Abstract: This paper presents the analysis of pulse load operation on the health of a simplified electric ship power system. Two scenarios of the pulse load operation, with and without an energy storage system have been addressed. The energy storage used is a flywheel as it has a very fast time response in supplying high power demands. The health of the electric ship power system is monitored by observing key indicators in the components critical to the working such as the generator and propulsion motor. The time-domain simulation of two test cases is carried out in the PSCAD/EMTDC software platform. The results underscore the vital importance of the flywheel energy storage system in maintaining the stability of the ship power system in the event of pulse load operation.

Wind power forecasting and error analysis using the autoregressive moving average modeling

Abstract: This paper presents a method for wind power forecasting and studies the relationship between the accuracy of the forecast and wind power variability. Actual wind power measurement data is applied to model an auto regressive moving average (ARMA) process. Burg and Shanks algorithms are then utilized to determine the model coefficients. Variability, accuracy and measured error in forecasts generated by the model are used to asses the data and the quality of the forecast. The model is shown to have good accuracy in forecasts within one hour and declines in accuracy further ahead in time. Drawing comparisons between forecasts generated for cases of differing data variability, the aggregate power generation of a group of wind farms is shown to have better accuracy in forecasts than the single wind farm.

Variable rotor-resistance control of wind turbine generators

Abstract: By adding a variable external resistance to the rotor of an induction generator used in a wind turbine, it is possible to manipulate the torque-speed curve and control the output power. The hardware implementation is accomplished by a set of three-phase external resistors connected in series with the rotor windings. To vary the effective value of the external resistance, a three-phase diode bridge and a DC chopper with a variable duty cycle is commonly used. Thus, the wind turbine generator operates at variable slip above synchronous speed. This method is less flexible than a doubly-fed induction generator, but does not require the use of slip rings to access the rotor circuit. This paper describes the construction of a time-domain electromechanical model for a wind turbine. The model is used to evaluate control strategies for the output power based on stator power, the equivalent circuit, or aerodynamic torque. All are capable of maintaining a constant power beyond rated wind speed. The transient performance of the controllers is also compared and control based on the aerodynamic torque is found to be the fastest, albeit with high transient power deviations.

The Annual Black Start Service Selection Analysis of ERCOT Grid

Abstract: This paper evaluates ERCOT's existing annual Black Start service selection analysis and subsequently presents novel selection procedures. ERCOT procures Black Start resources annually through a competitive process. It selects and awards contracts to qualifying resources after completing a Black Start unit selection analysis, which selects a group of Black Start resources that meet a set of system selection criteria consisting of system reliability and minimum cost parameters. A current analysis methodology exists, but due to its inherent limitations, it is very labor intensive. Further analysis methodology development is performed to streamline the selection process, enable additional functions, reduce the manual intervention of personnel, and overall to improve the selection analysis. This paper analyzes the current Black Start automatic program analysis, and proposes new methodologies, programming improvements, and enhanced user ability.

Development and analysis of an ESS-based application for regulating wind farm power output variation

Abstract: Using energy storage systems (ESS) for regulating wind farm power output variation is a promising application. It is known that wind farm output variation has negative impact on load following and grid voltage stability. ESS can be used to store certain amount of wind power and re-dispatch it appropriately. In this way ESS can reduce the wind farm output variation and the adverse stability-related impact. The concept is simple but comprehensive investigation is required to develop the ESS-based application and measure its effectiveness. This paper presents a study into this area. First, the ESS-based application settings are developed. Then, the ESS effects on wind power integration, voltage stability, and load-demand mismatch reduction is quantified and analyzed. The results show that ESS of certain ratings can make the wind farm output a better match for the load-demand while raising the grid voltage stability significantly. The ESS typically needs to perform only a few charge-discharge cycles per day. This is advantageous in preserving the ESS life.

Estimation of System Damping Parameters Using Analytic Wavelet Transforms

Abstract: This paper presents an efficient methodology for estimating the damping of a power system in which multiple resonant frequency components exist. The proposed method was developed using the analytic wavelet transforms and requires only the intrinsic transient portion of the voltage waveform (i.e., the free response due to capacitor bank energizing). The method can estimate the damping ratios of the selected modes and is free from the unimodal restriction of the Hilbert damping analysis. Thus, the method can provide more accurate system modal information.

Estimating transient response of simple AC and DC shipboard power systems to pulse load operations

Abstract: The sources of transients in an electric ship power system include those encountered in conventional terrestrial power systems as well as certain sources unique to the shipboard environment such as the pulse load. This paper explains the modeling of the electric ship power system components including the pulse load for studying the effects of the transients in different frequency ranges. The models of AC and DC power systems are compared for these frequency ranges.

Validation and analysis of wind power plant models using short-circuit field measurement data

Abstract: This paper describes the use of field measurements to validate a wind power plant model. A three-phase time-domain wind power plant model, based on the Western Electricity Coordinating Council generic model, has been developed with this validation in mind. The available fault data consists of the three-phase voltages and currents measured at the point of interconnection (POI) of the wind plant with the grid. For validation, the measured voltage data is injected into the simulation model and the current response from the model is compared to the measured current data from the real-world wind plant. Real power and reactive power flows calculated from the measured data and the model output are compared. The advantage of this validation method, namely use of currents in addition to real and reactive power flows, is also discussed. Comparison with a positive-sequence model is also provided.

Generation adequacy assessment of power systems with wind generation: A system operations perspective

Abstract: The increasing wind penetration levels in today's power systems are creating challenges for system operators when maintaining adequate system reliability. Since ancillary service requirements are usually based on historical performance and engineering experience, a tool which could assess the system reliability status and determine when additional services are needed would be very beneficial for system operators, especially for systems experiencing large wind fluctuations. In this paper, an approach is proposed to assess the operational system generation adequacy by considering the generators' forced outages, the load forecasting deviations, and most importantly the wind forecasting deviations. The objective of this approach is to present a quantitative method of evaluating the hourly and daily reliability risk levels on a day-ahead and hour-ahead basis. Using probabilistic methods, an operational reliability assessment tool is developed to assist system operators in identifying high risk periods and making the necessary adjustments to ensure acceptable levels of system reliability.

Time-domain power system simulator as an efficient tool for teaching and learning electric power quality phenomena

Abstract: Electric power quality (PQ) phenomena involve the interaction between various elements of the power system. Due to the complex nature of the phenomena, electric PQ education at the undergraduate level is challenging. The instructional method is typically based on the traditional descriptive-inquiry approach. This article suggests that a time-domain computer-based simulation tool be used to supplement the traditional approach. The combined method allows students to simulate complex phenomena in a controlled environment so as to investigate the interaction between power system elements that give rise to the phenomena, and how the phenomena impact the system. The combined method is expected to reinforce and enhance the student learning process. The article then presents three simulation examples to demonstrate how the time-domain simulation method can be integrated into the traditional descriptive-inquiry method. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 214–224, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae20194

A comparative metric to quantify the variability of wind power

Abstract: The stochastic nature of wind power severely affects the stability of the electric grid. It is well known that power quality and project economics are adversely affected by increased intermittency and variability. Thus, an accurate, simple, and powerful metric for comparing the variability of different power sources would serve as a useful figure of merit. The current coefficient of variation metric has significant shortcomings for quantifying the variability of a stochastic power source's output. This paper exposed those shortcomings in detail and a new metric is proposed for quantifying the variability of power from a wind farm in particular or for an intermittent power source in general. The proposed metric is calculated from the spectral decomposition of a power source's autocorrelation function. The intermittency metric compares the components of the wind power that vary with infra-diurnal frequencies to the mean power output.

Design and performance of a scaled electromechanical wind turbine power train model

Abstract: Many wind turbine designs employ induction machines, operating as fixed speed, squirrel cage generators, or as variable speed, wide slip and double fed induction generators (DFIG). In order to study, prototype, and demonstrate the effectiveness of each design, an electro-mechanical model of a wind turbine power train has been constructed at an approximate scale of 1:1000, relative to a utility-scale wind turbine. The power train model includes the rotor, the gearbox, and the generator. The model was characterized under a range of steady state conditions. Electrical measurements were made with a commercial power quality analyzer, and rotational speed measured with a contact tachometer.

Phasor measurement unit placement Algorithm

Abstract: The importance of having phasor measurement units or PMUs in an electric grid is widely recognized. However, the number of PMUs on a large system is limited by cost and the placement of PMUs must be addressed. The main objective of this research is to create an algorithm to identify buses that are the best candidates for PMU placement based on certain requirements. The monitoring of certain grid events like transmission line failure or generator failure must be possible from the selected PMU locations. In addition, the PMUs must be distributed evenly so that critical parts of the grid are visible. At the same time, there should be no or little redundancy in the PMU readings unless it is intentional to provide additional data reliability. The algorithm, once developed, is then applied to the electric network directed and operated by the Electric Reliability Council of Texas (ERCOT). After analyzing the results, clusters or group of buses are identified in each operational area in the ERCOT gird, where the PMUs should be located. The PMU can be located at any of the bus in the cluster. In future it is desirable to expand the algorithm to consider the geographical divisions in the ERCOT grid along with the commercial divisions.