A. Hasib Chowdhury

Load frequency control of multi-microgrid using energy storage system

Control of active power and frequency in a power system is referred to as load frequency control (LFC). A linear combination of tie line power between interconnected system and frequency deviations, defined as area control error (ACE), is regulated to zero by LFC such that frequency and tie-line power errors are forced to zeros and a balance is achieved between generation and load. This paper presents an investigation on the LFC of multi-microgrid (MMG) using energy storage system (ESS). The tie-line connected MMG system consists of two microgrids, each made up of a synchronous generator, a PV source, a wind power system, ESS and load. Control strategies are developed based on both, frequency deviation and ACE, to regulate the ESS output. A performance index is defined for comparative assessment of control strategies. Effectiveness of the frequency control strategies is studied through simulation.

Parameterization of active disturbance rejection controller for load frequency control

Active disturbance rejection control (ADRC) has gained significant attraction due to its simple tuning method and robustness against process parameter variations, whether the plant is linear or non-linear, time-varying or time-invariant. In load frequency control, the use of ADRC is proposed to regulate the area control error, frequency error and tie-line error in the presence of internal dynamics and external disturbance. This paper presents a study on the effects of state observer bandwidth, controller bandwidth and sampling period on the performance of the ADRC based load frequency control of single- and multi- area power systems. The study gives good insight in choosing controller parameters for ADRC based LFC.

Design and cost benefit analysis of grid connected solar PV system for the AUST campus

This paper describes a design and detailed analysis of a grid connected solar PV system for the Ahsanullah University of Science and Technology (AUST) campus. Various design considerations are discussed including the factors and parameters with limited data and information resources available for Bangladesh. Cost analysis reveals that the proposed design is economical and cost effective for the AUST campus.

Frequency transient analysis of countrywide blackout of Bangladesh Power System on 1st November, 2014

In this paper, real time frequency transient analysis with respect to frequency control of Bangladesh Power System (BPS) countrywide blackout on 1st November, 2014 is presented which occurred after HVDC station tripped. The inertia constant of a system can be a significant tool for investigating the frequency stability of a system and the frequency transient of power system is a vital index for power system operation and research. The dynamic frequency characteristic of power system is the basis of many important design works such as the design of under frequency load shedding scheme. Therefore, it is obvious and essential to analyze the dynamic frequency characteristic of BPS before countrywide blackout after disturbance. This paper first analysis real time frequency transient and determine the system inertia. Secondly it shows that maintaining nominal level of inertial reserve in real-time operations with unit commitment which can be crucial to ensure stable, secure and reliable operation of BPS. Beside this under frequency scheme should be revised and controlled. BPS network disintegration along with rate of change of frequency should be ensured for adaptive as well as self-healing of the power system.

An approach for classification of power quality disturbances based on Hilbert Huang Transform and Relevance Vector Machine

This paper presents a new approach for power quality disturbances classification using Hilbert Huang Transform (HHT) and Relevance Vector Machine (RVM). A disturbed power signal is first analyzed in terms of intrinsic mode functions (IMFs) by Empirical mode decomposition (EMD). Considering the first three IMFs, the Hilbert transform is then applied to them to obtain HHT outcomes, namely instantaneous amplitude and phase, which are exploited to form the feature vector. The feature vector thus obtained when fed to a RVM classifier is found to effectively classify various classes of power quality disturbances. Simulation results through training and testing show that the proposed method using RVM classifier is superior in performance in comparison to the methods using k nearest neighbour (k-NN) or Support Vector Machine (SVM) as a classifier.

Comparison of dynamic resistance arc furnace models for flicker study

Owing to the nonlinear characteristics, electric arc furnace (EAF) loads can result in serious electrical disturbances such as harmonics and voltage flicker in power system. Amplitude modulation of the supply voltage in the frequency range of 6-10 Hz created by EAF can cause annoying fluctuations of the electric lighting flux. This paper presents comparative study of different EAF models. The static resistance in each piece-wise linear section of the V-I curve of each model is modulated to obtain the dynamic resistance EAF model. Voltage flickers at PCC caused by different dynamic resistance models are measured using MATLAB simulation of the EAF systems and the results are compared with existing fliker limits to see the level of flicker caused by different models and modulation indices.

Comparative study of ADRC and PID based Load Frequency Control

This paper presents a comparative study between Active Disturbance Rejection Control (ADRC) based Load Frequency Control (LFC) and proportional-integral-derivative (PID) based LFC. Both, single-area power system and multi-area power system have been considered where area control error (ACE) has been regulated in the presence of uncertainties in system dynamics and external disturbances. The ADRC proves to be a capable replacement of PID with unmistakable advantage in performance for load frequency control in power system.

Inclusion of slack bus in Newton Raphson load flow study

Load flow solution is an inevitable tool for power system planning and operation. Among various methods of load flow solution techniques Newton Raphson (N-R) and its derivatives are the most popular and widely used ones. In Newton Raphson method one of the generator buses is treated as slack bus which is kept out of calculation during iterations. This is because of the fact that the slack bus is to carry entire loss of the system and total loss cannot be calculated before the end of iterations. The exclusion of slack bus from the load flow iteration restricts many analyses to make. Consideration of distributed slack bus, load flow for Microgrids, study on minimization of system losses etc. cannot be performed when the slack bus is excluded from the iterations. This paper reports the development of a method of including slack bus into the Jacobians for N-R load flow study. The method involves formulating the loss equation and then devising the formula for the terms to be included with the elements of the Jacobian matrix. The modified N-R method is applied to all of the buses and the losses are calculated in each iteration and included with the slack bus. The results obtained using the modified method are compared with those using conventional method. The agreement of the results confirms the accuracy of the developments.

Power system load switching monitoring using wavelet transform based multiresolution signal decomposition

This paper presents a wavelet transform based multiresolution signal decomposition technique for monitoring power system load switching. The proposed method depends on the standard deviations of wavelet coefficients calculated at different resolution levels. Power system signals are decomposed using discrete wavelet transform based filter bank. The simulation results of the study clearly demonstrate that proposed method can efficiently detect and localize power system load switching in time domain. The method can also give information on the magnitude of the load switched and its distance from the observation point.

Optimum economic dispatch of interconnected microgrid with energy storage system

Interconnected microgrid system enhance reliability and reduce spinning reserve due to higher redundancy. It is useful for areas where conventional power grid cannot be connected. This paper presents optimal economic dispatch strategy of distributed generation where two microgrids and a single energy storage system (ESS) are interconnected together. Genetic algorithm is used to minimize the operating cost of the proposed system and to find out the optimum value of the output power produced by distributed generator. The objective function comprises of fuel cost, operation and maintenance cost, as well as cost of emissions. One of the microgrids consists of diesel engine generator, microturbine generator, solar PV and another with fuel cell and wind turbine generator. The ESS is charged from the interconnected microgrids and can be used for load frequency regulation and spinning reserve of the system.