Two-area Interconnected Power Research Articles

Robust Load Frequency Control of Interconnected Power System in Smart Grid

In this paper, the coordinated control of vehicle to grid (V2G) power control and proportional-integral (PI) tuned with particle swarm optimization (PSO), based on H-infinity control, are integrated to control the frequency regulation of interconnected power system in Smart Grid (SG) environment. The plug-in hybrid electric vehicle (PHEV) can compensate the deficient load frequency control (LFC) capacity. In this way V2G power control is applied to compensate for the LFC capacity. For charging the batteries, power is supplied from grid-to-vehicle (G2 V). The traditional controller performance is compared for working with multiple uncertainty-based H∞ controllers and the results proved the predominant performance of the proposed control. To check the system robustness against uncertainty, the PI controller gain and State of Charge (SOC) deviation are optimized using the PSO-based multiple uncertainty-based H∞ controller. Different specimens have been analyzed to ensure the entire working of the developed model. A series of simulation results are presented for the dynamic response of power systems which is superior to other design methods obtained from the literature. Simulation results of two-area interconnected intelligent power system show that frequency deviations are minimal and within specified limits.

Fuzzy-PI based automatic generation control of two-area interconnected nonlinear power system

This paper presents the modelling, simulation and performance analysis of automatic generation control (AGC) of two-area interconnected nonlinear power system using fuzzy logic system. Fuzzy control, one of the intelligent control techniques, uses the human expert knowledge to make control decisions. Mamdani fuzzy inference system has been used to tune proportional-integral controller for AGC of two-area interconnected nonlinear power system. To compare the results the conventional integral control is also presented. The simulation of control schemes has been carried by developing MATLAB-SIMULINK models. The simulation results and analysis justify the comparative advantages of fuzzy control method.

Damping of low frequency oscillations in a hydro-thermal power system using thyristor controlled series compensator

Thyristor controlled series capacitor (TCSC) is a series type flexible AC transmission system (FACTS) device which can effectively change the impedance of a transmission line. This paper is concerned with developing a linear incremental model for a TCSC and its application to improve the performance of automatic generation control (AGC) of two-area interconnected hydrothermal power system. The optimised integral gain values of AGC are obtained using integral squared error (ISE) technique. A quadratic performance index considering a step load perturbation in either of the areas is considered for minimisation. Simulation results suggest that, incorporating a TCSC is very effective in damping the low frequency oscillations in area frequencies as well as the tie-power after a sudden load perturbation in any of area compared to AGC without TCSC.

Application of Modified Biogeography Based Optimization in AGC of an Interconnected Multi-Unit Multi-Source AC-DC Linked Power System

An attempt has been made for the effective application of biogeography based optimization and its modified version to solve load frequency control (LFC) problem. Two-area interconnected multi-unit multi-source power system having thermal, hydro and gas power plant without and with AC-DC link is considered for study. Proportional-integral-derivative controller is used as secondary controller in LFC system and its gains are tuned by proposed algorithms through minimization of integral time absolute error based objective function. The results confirm the effectiveness of proposed algorithms after comparing results with other evolutionary algorithms like differential evolution (DE), teaching learning based optimization (TLBO) for the similar test system. The robustness of proposed algorithm is checked with different objective functions like integral square error, integral absolute error, integral time square error criterions and under different loading conditions. Critical analysis of results reveals that proposed method gives better performance than that obtained with DE, TLBO.

Load Frequency Control of a Two-Area Thermal-Hybrid Power System Using a Novel Quasi-Opposition Harmony Search Algorithm

In the present work, a two-area thermal-hybrid interconnected power system, consisting of a thermal unit in one area and a hybrid wind-diesel unit in other area is considered. Capacitive energy storage (CES) and CES with static synchronous series compensator (SSSC) are connected to the studied two-area model to compensate for varying load demand, intermittent output power and area frequency oscillation. A novel quasi-opposition harmony search (QOHS) algorithm is proposed and applied to tune the various tunable parameters of the studied power system model. Simulation study reveals that inclusion of CES unit in both the areas yields superb damping performance for frequency and tie-line power deviation. From the simulation results it is further revealed that inclusion of SSSC is not viable from both technical as well as economical point of view as no considerable improvement in transient performance is noted with its inclusion in the tie-line of the studied power system model. The results presented in this paper demonstrate the potential of the proposed QOHS algorithm and show its effectiveness and robustness for solving frequency and power drift problems of the studied power systems. Binary coded genetic algorithm is taken for sake of comparison.

Robust SMES controller design for stabilization of inter-area oscillation considering coil size and system uncertainties

It is well known that the superconducting magnetic energy storage (SMES) is able to quickly exchange active and reactive power with the power system. The SMES is expected to be the smart storage device for power system stabilization. Although the stabilizing effect of SMES is significant, the SMES is quite costly. Particularly, the superconducting magnetic coil size which is the essence of the SMES, must be carefully selected. On the other hand, various generation and load changes, unpredictable network structure, etc., cause system uncertainties. The power controller of SMES which is designed without considering such uncertainties, may not tolerate and loses stabilizing effect. To overcome these problems, this paper proposes the new design of robust SMES controller taking coil size and system uncertainties into account. The structure of the active and reactive power controllers is the 1st-order lead-lag compensator. No need for the exact mathematical representation, system uncertainties are modeled by the inverse input multiplicative perturbation. Without the difficulty of the trade-off of damping performance and robustness, the optimization problem of control parameters is formulated. The particle swarm optimization is used for solving the optimal parameters at each coil size automatically. Based on the normalized integral square error index and the consideration of coil current constraint, the robust SMES with the smallest coil size which still provides the satisfactory stabilizing effect, can be achieved. Simulation studies in the two-area four-machine interconnected power system show the superior robustness of the proposed robust SMES with the smallest coil size under various operating conditions over the non-robust SMES with large coil size.

Design of Decentralized Biased Controllers for Load-Frequency Control of Interconnected Power Systems

This article proposes a design of biased controllers for the decentralized load-frequency control of interconnected power systems. Conventional load-frequency controllers are usually implemented in a proportional plus integral form using area control error (ACE) in order to obtain satisfactory results. In this article, the optimum proportional plus integral biased controllers are designed using integral squared error (ISE) criterion as well as maximum stability margin (MSM) criterion to obtain better transient and steady-state responses. These controllers are designed and implemented in a two-area interconnected thermal power system. The system was simulated and the frequency and tie-line power deviations resulting for a step load disturbance are presented. The results reveal that the biased controllers provide better transient as well as steady-state response and increased stability margin when compared with the responses obtained using conventional controllers. It is also found that the biased controllers are less sensitive to the changes in system parameters.