Hybrid Signal Processing and Soft Computing approaches to Power System Frequency Estimation

Dynamic variation in power system frequency is required to be estimated for implementing the correcting measures. This paper presents power system frequency estimation by using RLS-Adaline and KF-Adaline algorithms. In the proposed hybrid approaches the weights of the Adaline are updated using RLS/KF algorithms. Frequency of power system signal is estimated from final updated weights of the Adaline. The performances of the proposed algorithms are studied through simulations for several critical cases that often arise in a power system. These studies show that the KF-Adaline algorithm is superior over the RLS-Adaline in estimating power system frequency. Studies made on experimental data also support the superiority

Grid Connected Renewable Energy Sources and Net Metering: A Review

In this paper, the constraints of a grid connection are presented along with some of the solutions to the problems as proposed by various researchers. Non-renewable energy sources are getting exhausted day by day. There is a need for alternative sources of energy. In this paper, various constraints in the incorporation of grid-connected renewable energy sources and the required solution are discussed. The concept of net metering and associated challenges are presented in this paper

Power system frequency estimation using linear and nonlinear techniques

In an electrical power system frequency is an important parameter. The frequency of operation is not constant but it varies depending upon the load conditions. In the operating, monitoring and controlling of electric device power system parameters are having great contribution. So it is very important to accurately measure this slowly varying frequency. Under steady state conditions the total power generated by power stations is equal to system load and losses. Frequency can deviate from its nominal value due to sudden appearance of generation-load mismatches. Frequency is a vital parameter which influences different relay functionality of power system. This study was made to estimate the frequency of measuring voltage or current signal in presence of random noise and distortion. Here we are first using linear techniques such as complex least mean square (LMS), least square (LS) and recursive least square (RLS) algorithm for measuring the frequency from the distorted voltage signal. Then comparing these results with nonlinear techniques such as nonlinear least mean square (NLMS), nonlinear least square (NLS), nonlinear recursive least square (NRLS) algorithms. The performances of these algorithms are studied through simulation

An extended complex Kalman filter for frequency measurement of distorted signals

ABSTRACT The design of an extended complex Kalman filter for the nieasurenient of power system frequency has been presented in this paper. The design principles and the validity of the model has been outlined. A complex model has been developed to track a distorted signal that belongs to a power system. The model inherently takes care of the frequency measurement along w i t h the amplitude and phase of the signals. The theory has been applied to standard signals representirig the worst-case measurement and network conditions in a typical power system. The proposed algorithm is suitable for realtime applications where the measurement noise and other disturbances are higli. llie coiiiplex quantities can be conveniently handled using a floating point processor. Comparison of the results of the proposed method with those obtained from a real extended Kalnlan filter reveal the superior performance of the former method

Measurement, control and protection of microgrids at low frame rates supporting security of supply

Increasing penetrations of distributed generation at low power levels within electricity networks leads to the requirement for cheap, integrated, protection and control systems. To minimise unit cost, algorithms for the measurement of AC voltage and current waveforms should be implemented on a single microcontroller, which also carries out all other protection and control tasks, including communication and data logging. This limits the frame rate of the major algorithms, although ADCs can be over-sampled using peripheral control processors on suitable microcontrollers. Measurement algorithms also have to be tolerant of poor power quality which may arise, even transiently, within a microgrid, battlefield, or disaster-relief scenario. This thesis analyses the potential magnitude of these interfering signals, and presents suitably tolerant architectures and algorithms for measurements of AC waveforms (amplitude, phase and frequency). These algorithms are shown to be robust and accurate, with harmonic content up to the level of 53% THD, and with the major algorithms executing at only 500 samples per second. This is achieved by the careful optimisation and cascaded use of exact-time averaging techniques, which prove to be useful at all stages of the measurements: from DC bias removal to low-sample-rate Fourier analysis to sub-harmonic ripple removal. Algorithms for three-phase nodal power flow analysis are benchmarked on the Infineon TC1796 microcontroller and require less than 8% of the 2000μs frame time, leaving the remainder free for other algorithms. Furthermore, to optimise security of supply in a microgrid scenario, loss-of-mains must be detected quickly even when there is an accidental or deliberate balance between local active power generation and demand. The measurement techniques are extended to the detection of loss-of-mains using a new Phase Offset relay, in combination with a novel reactive power control technique to avoid the non-detection-zone. These techniques are tested using simulation, captured network transient events, and a real hardware microgrid including a synchronous generator and inverter

Medida continua de la frecuencia en redes eléctricas con perturbaciones electromagnéticas conducidas de baja frecuencia

En esta Tesis se desarrolla un marco de trabajo para la comparación de los diversos métodos que realizan la medida de la frecuencia de la red eléctrica de manera continua, tanto para redes monofásicas como trifásicas. Esta comparación ha sido realizada tanto en ausencia de perturbaciones electromagnéticas, como en presencia de perturbaciones conducidas de baja frecuencia. Las señales de prueba utilizadas son las propuestas por la normativa IEC 61000 para este tipo de perturbaciones electromagnéticas (distorsión armónica, desequilibrio de tensión, fluctuación de tensión, hueco de tensión y variación de frecuencia). También se ha propuesto un nuevo método de medida, con versión monofásica y trifásica, que mejora las prestaciones de los existentes para determinados tipos perturbaciones. Finalmente, se ha evaluado la posibilidad de realización en tiempo real de los distintos métodos de medida. A partir de la normativa indicada, se ha creado un banco de señales de prueba para evaluar las prestaciones de cada método considerado. Estos han sido simulados en Mathcad, procesando las señales de prueba en distintas condiciones de ruido, cuantificación y frecuencia de muestreo. Para comprobar la ejecución en tiempo real de estos métodos, se han codificado en C y ejecutado con un controlador digital de señal. Para la comparación de los distintos métodos de medida de la frecuencia, se ha calculado el error máximo cometido en la estimación de la frecuencia para cada método y cada señal de prueba. El nuevo método de medida propuesto, presenta las mismas prestaciones o mejores que los métodos existentes cuando la tensión de red está distorsionada por armónicos impares, existe desequilibrio de tensión (redes trifásicas), hay fluctuación en la tensión de red, huecos de tensión o variaciones de frecuencia