Automatic Generation Control Regulators Research Articles

Design and analysis of optimal AGC regulator for multi‐area power systems with TCPS and energy storage unit in deregulated environment

AbstractIn today's electric power network, fast changes are the norm, and auxiliary services such as automatic generation control (AGC) play a crucial role in maintaining the quality of the power supply. AGC ensures a balance between power generation, demand, and losses to sustain frequency stability and variation in tie‐line power within a set limit, even when the load changes. To accomplish this, it is always beneficial to consider new approaches to controlling the situation. This paper introduces the design of new AGC regulators that consider deviation in DC tie‐line power as an extra control variable for the turbine controller. In this study, three different deregulated power systems (containing two control areas), namely three thermal generations, the combination of one thermal and two hydro generations, and three hydro generations, including two power distribution companies (DISCOs) in each control area. These optimal AGC regulators are implemented in the proposed thermal–thermal–thermal system to carry out the various power contracts. The results have shown that the dynamic outcomes meet the AGC standards. To improve further dynamic results and the proposed systems' stability margins by incorporating redox flow batteries (RFB). In actual operating conditions, the system parameters do not remain constant due to the aging effect, assumptions made in simplifying the mathematical model, etc. Thus, ±50% deviations in the nominal value of system parameters to assess how well the optimal AGC regulators perform in the system under investigation. The suggested realistic AGC system incorporates many parameter fluctuations and works well with the optimal AGC regulators developed for the proposed plans. This study expanded to include a two‐area, thermal‐hydro‐hydro (THH) system under a deregulated framework connected via an asynchronous transmission link with or without a thyristor‐controlled phase shifter (TCPS) and RFB. The genetic algorithm (GA) can solve many issues and has global search, flexibility to varied problem types, intrinsic parallelism, and the ability to handle massive, complex search spaces. Thus, a two‐area deregulated hydro‐hydro‐hydro system with parallel tie‐lines utilizes GA‐PID, GA‐FOPID, and GA‐(1 + PI)‐FOPID controllers. Moreover, a random load disturbance (RLD) is employed in each section of the offered approach to show the resilience and elite performance of the proposed control strategy. To produce various dynamic reactions in the plans, MATLAB software version R2013a is employed.

Combined frequency and voltage regulation in multi-area system using an equilibrium optimiser based non-integer controller with penetration of electric vehicles

The frequency and terminal voltages in power systems are the two critical operating points that balance active and reactive powers, which must be maintained within predefined limits through automatic generation control (AGC) and automatic voltage regulator (AVR) control loops. To address this issue, in this manuscript, the problem of a combined AGC and AVR is solved using a non-integer order PID controller. Its parameters are adjusted using the recently proposed equilibrium optimiser (EO) technique. Along with conventional sources, renewable energy sources such as geothermal power plants and electric vehicles are considered. The EO-tuned non-integer order PID controller outperformed the traditional integer order PI and PID controllers in view of peak overshoots, undershoots and settling times. The performance of EO is evaluated and found superior against widely used particle swarm optimisation and firefly algorithms in the presence of non-integer order PID controller. Different case studies such as random load disturbance, the effect of nonlinearities, the impact of communication time delay and sensitivity analysis have been performed, which also test the heftiness of the non-integer order PID controller. The obtained results are verified using the real-time digital simulator OPAL-RT (OP4510) for nominal conditions.

SMES-GCSC Coordination for Frequency and Voltage Regulation in a Multi-Area and Multi-Source Power System with Penetration of Electric Vehicles and Renewable Energy Sources

Frequency, tie-line power, and the terminal voltages of synchronized generators must all be kept within prescribed limits to ensure the stability of an interconnected power grid through combined automatic generation control (AGC) and automatic voltage regulator (AVR) loops. Thermal power plants, electric vehicles, and renewable energy sources—including solar and wind, geothermal, and solar thermal power plants—form the two-area integrated power system in present research. A new cascade controller named the cascaded proportional integral derivative (PID) and fractional-order PID (CPID-FOPID) controller is proposed for the first time, whose performance is compared with the PID and FOPID controller. The results show that the proposed cascade controller outperforms PID and FOPID in delivering superior dynamic characteristics, including short settling times and low oscillation amplitudes. A new metaheuristic algorithm named the coot algorithm was applied to optimize the parameters of these controllers. The suggested controller outperforms FOPID in the combined AGC and AVR problem under uncertain conditions (random load disturbance, variable input of solar irradiation, and wind power). Robustness of the controller is tested with significant variation in the turbine time constant of the thermal and geothermal power plant. In this study, authors also investigated the best possible coordination between the superconducting magnetic energy storage (SMES) and gate-controlled series capacitor (GCSC) devices to control both voltage and frequency simultaneously. The effect of communication time to the power system is analyzed in this study. Additionally, the obtained results are satisfactorily validated using OPAL-RT real-time digital simulator.

Comparative Performance Investigation of Genetic Algorithms (GAs), Particle Swarm Optimization (PSO) and Bacteria Foraging Algorithm (BFA) Based Automatic Generation Control (AGC) with Multi Source Power Plants (MSPPs)

This paper presents comparative performance analysis of GAs, PSO and BFA technique-based AGC regulators with MSPPs in each system. Each control area consists of hydro, thermal and gas power plants (HTGPPs) for generation of electricity. In this work, proportional integral derivative (PID) control structure-based AGC regulators are designed by using the above intelligent techniques. However, the cost function for designing of these intelligent controllers is formulated using the integral square error (ISE) performance index. In the previous AGC studies, simulation time for tuning of above intelligent AGC controller to analyze performance was not reported. Therefore, this research work proposes a new study to investigate the performance of these intelligent AGC controllers based upon performance indicators: (i) simulation time of these techniques, (ii) first peak value of transient response, (iii) oscillations in transient response and (iv) settling time of transient response. The parameters of the controllers are evaluated using these techniques and investigations are carried out to find the best performance of the system. Besides, system dynamic performance of BFA-tuned AGC controllers are also demonstrated for +1% to +4% step load disturbance in the respective control areas.

Automatic Rescheduling of Generator for Rotor Speed Regulation by KRASOVSKII’s Theorem

Emergency control of the power system is performed via generator rescheduling or load shedding depending upon the availability of generation and demand. This paper presents a generator rescheduling method based on Krasovskii’s theorem for enhancing rotor speed regulation during multiple contingency conditions. The speed governor in automatic generation control (AGC) and automatic voltage regulator (AVR) are indispensable components of the control mechanism for deploying any control scheme. Contingencies may lead the security state of the power system towards a preventive, emergency, and restorative state. Generally, there is a violation of equality constraints of active and reactive power in the corrective security state. However, in this paper, the corrective security state considers a significant imbalance in active power with a generation capacity always greater than load. For rotor angle stability, active power delivery by the generator met the demands, whilst the turbine and automatic speed governor together balance it by changing the set point of the turbine inlet. This paper investigates the rotor stability by triggering a new set point by the rescheduling of the generator. The strategy proposed encompasses the broad domain of active power imbalance using Krasovskii’s theorem, which is an extensive form of the Lyapunov stability theorem for the nonlinear multivariable autonomous system. The proposed control scheme is deployed on an IEEE-10 machine 39-bus system for validation and feasibility detection. It is found that the proposed scheme is more accurate than the conventional turbine automatic speed governor close loop system. Moreover, there is turbine power-saving up to 400 MW. In addition, the rotor attains steady-state speed quicker up to 5-10 sec and attains synchronous speed in all the cases considered, i.e., single load outage; multiple load outage; area outage; and load increment. The MATLAB® and the CVX platform are used to validate the proposed concept.

Coupling between Automatic Generation Control and Automatic Voltage Regulator While Considering Generation Rate Constraint of Two Areas

This paper describes the implementation of automatic generation control (AGC) and automatic voltage regulator (AVR) under generation rate constraint (GRC) and coupling between automatic generation control and automatic voltage regulator while considering generation rate constrain of two areas for improve and better performance characteristic of load frequency control (LFC) problem. our control aim has to normalize the area control error (ACE), frequency error and tie-line power error in spite of the presences of system uncertainties and external load disturbance, So that the required frequency and power interchange with adjacent structures are maintained in order to reduce the transient deviations and to provide zero steady state error in proper short time, the behavior of the planned is checked by MATLAB SIMULINK software.

Load frequency regulation by de-loaded tidal turbine power plant units using fractional fuzzy based PID droop controller

This study presents a model to analyse and simulate tidal power generation for hybrid power system in the presence of highly infiltrated tidal units. The response of the hybrid system may be at risk without suitable frequency enhancement techniques. The complete load frequency model is a combination of conventional automatic generation control (AGC) and automatic voltage regulator (AVR). AVR is employed to keep the output voltage magnitude of conventional generator at a particular level. The purpose of integrating AGC with AVR is to maintain the equilibrium between system’s generation and load as well as to keep the frequency of system within suitable range. Owing to inclusion of nonconventional sources, the total inertia of the power system is eventually diminished. Conventional PID droop controller demonstrates inefficacy in diminishing the frequency deviations due to slow controlling action. This research proposes a fractional order (FO) fuzzy PID droop in de-loaded area to improvise the frequency excursion over fixed/Fuzzy PID/PID droop controllers. Imperialist competitive algorithm (ICA) is employed to tune the parameters of the controllers. ICA optimized fractional order PID droop control strategy unveils best performance (settling time = 11.65 s, undershoot amplitude = 0.26pu, performance index = 0.072e−6) over the integer order fuzzy PID control (settling time = 12.02 s, undershoot amplitude = 0.278 pu, performance index = 0.189e−6) and PID droop control (settling time = 30.68 s, undershoot amplitude = 0.95 pu, performance index = 0.215e−6). Examination of dynamic responses for abrupt changes in load request divulges the pre-eminence of proposed droop controller strategy with others controllers. The comprehensive study carried out in this paper implies that ICA optimized controller operates properly and has proven its robustness for ±10% variations in system parameters and physical constraints (Generation rate constraints, governor dead band, and time delay). This study also analyses the effect of tidal power plant contribution in the frequency regulation by inertia, primary and secondary frequency control.

Automatic Generation Control (AGC) of Wind Power System: An Least Squares-Support Vector Machine (LS-SVM) Radial Basis Function (RBF) Kernel Approach

The present paper discusses the structural, operational and control complexity of present day modern power systems in the wake of addition of electrical energy from wind turbines. The automatic generation control (AGC) problem of interconnected power system incorporating doubly fed induction generator (DFIG)-based wind turbines has been formulated and the investigations under various system operating conditions are presented. A two-area power system with DFIG-based wind turbines in each area are considered for the investigations. The system non-linearities such as governor dead-band and generation rate constraint are incorporated in the system dynamic model development. A novel AGC scheme using a non-linear least squares-support vector machine is proposed in the work. The proposed regulator is trained using a reliable data set consisting of wide range of operating conditions and area load changes generated by robust control technique. The results obtained with proposed regulator are compared with that achieved with multi-layer perceptron (MLP) and conventional PI regulators under various system operating conditions. The investigations carried out in the work have effectively demonstrated the superiority over MLP and conventional PI-based AGC regulators.

Robust automatic generation control regulators for a two‐area power system interconnected via AC/DC tie‐lines considering new structures of matrix Q

This study discusses the design of robust automatic generation control (AGC) regulators based on the Ricatti-equation approach for a two-area system interconnected via a DC tie-line in parallel with an AC tie-line as an area interconnection between the control areas. The proposed robust AGC regulator designs require only the bounds of the system parameters and enable to ensure the overall asymptotic system stability for all admissible uncertainties. In this study, different models of state cost-weighting matrix ( Q ) are also developed. Various aspects of controllability and observability of the system states which directly or indirectly affect the system dynamics are identified and used in the design of robust AGC regulators. The results obtained with proposed regulator designs in the wake of 1% load disturbance in area-1 and these results are compared with those obtained with optimal AGC regulators to ensure the superiority of the designed AGC regulators. The system eigenvalues are also presented to check the system stability margins available with the implementation of AGC regulators.

Optimal AGC regulator for multi-area interconnected power systems with parallel AC/DC links

AbstractThe problem of simultaneous tuning of the automatic generation control (AGC) regulator’s gains of multi-area interconnected power system is carried out in this manuscript. Based on the types of area interconnections, a power system model consisting of reheat turbines is investigated by two test cases for the AGC study. In one of the test case AC link is used as area interconnection, whereas the parallel combination of AC/DC links is used as area interconnection in other test case. Each test case control area is consisting of plants with reheat thermal turbines. Genetic algorithm (GA) is used to globally optimize the gains of proportional integral-based AGC regulators with simultaneous optimization of frequency bias coefficient and tie-line power flows. The dynamic response curves are obtained for various system states with the implementation of designed GA-based AGC regulators considering 1% load perturbation in one of the areas. The conventional AGC regulators are also developed using the popular...

Hybrid evolutionary algorithm based fuzzy logic controller for automatic generation control of power systems with governor dead band non-linearity

AbstractA new intelligent Automatic Generation Control (AGC) scheme based on Evolutionary Algorithms (EAs) and Fuzzy Logic concept is developed for a multi-area power system. EAs i.e. Genetic Algorithm–Simulated Annealing (GA–SA) are used to optimize the gains of Fuzzy Logic Algorithm (FLA)-based AGC regulators for interconnected power systems. The multi-area power system model has three different types of plants i.e. reheat, non-reheat and hydro and are interconnected via Extra High Voltage Alternate Current transmission links. The dynamic model of the system is developed considering one of the most important Governor Dead Band (GDB) non-linearity. The designed AGC regulators are implemented in the wake of 1% load perturbation in one of the control areas and the dynamic response plots are obtained for various system states. The investigations carried out in the study reveal that the system dynamic performance with hybrid GA–SA-tuned Fuzzy technique (GASATF)-based AGC controller is appreciably superior as...

Automatic Voltage Generation Control for Two Area Power System Based on Particle Swarm Optimization

<p>This article presentes a PID controller for two area power system equipped with both automatic generation control and automatic voltage regulator loops. The research has been done to control two area power systems with PSO optimized self-tuning PID controller. The comparison between different controllers and the suggested PSO based controller illustrates that the proposed controller can generate the best dynamic response for a step load change. For this purpose, MATLAB-Simulink software is used. The obtained results are promising.</p>

Optimal AGC with redox flow batteries in multi-area restructured power systems

This paper attempts to investigate the effect of Redox flow batteries (RFB) in Automatic Generation Control (AGC) of multi-area restructured power systems. Initially, a two-area restructured thermal power system is investigated. For the analysis, optimal AGC regulators (OARs) are designed employing performance index minimization criterion. The advantages of the OARs are shown by comparing the results with Genetic Algorithm (GA) based integral controllers for the same restructured system. MATLAB simulation results further demonstrate significant improvements in the dynamic performance of the system with RFB. System stability enhancement with OARs/RFB is outlined by conducting the system modes study. The study is additionally extended to a more realistic two-area multi-source thermal–hydro–gas restructured system with/without RFB. To add nonlinearities, appropriate generation rate constraints (GRCs) are considered for the thermal, hydro and gas plants. Results verify that OARs are able to satisfy the AGC requirement under varied power transactions taking place in an open power market. The robustness of OARs is demonstrated by sensitivity analysis, which is carried out with wide variation in initial loading, system parameters and magnitude/position of the uncontracted power demands. Finally, the study is extended to a two-area multi-source thermal–hydro power system with/without considering RFB.

Optimal AGC of a multi-area power system with parallel AC/DC tie lines using output vector feedback control strategy

This article presents the design of optimal automatic generation control (AGC) regulators using output feedback control strategy for a multi-area interconnected power system. The power system consists of unidentical areas having diverse type turbines. The parallel AC/DC tie-lines are considered as area interconnection between the areas. Efforts have been made to propose optimal AGC regulators based on feedback of output state variables, which are easily accessible and available for measurement. In addition, a modified area control error incorporating DC tie-line power deviation is used in the design of optimal AGC regulators. The designed optimal AGC regulators are implemented and the system dynamic responses for various system states are obtained considering 1% load perturbation in one of the areas. The system dynamic performance is compared with that obtained with optimal AGC regulators designed using full state vector feedback control strategy. The pattern of closed-loop eigenvalues is also determined to test the system stability.

Guest Editorial

This is an IET Renewable Power Generation Special Section from the 3rd IET Renewable Power Generation Conference that was held in Naples. There was a wide range of topics among which were wind (turbines, offshore wind farms),photovoltaic generation, distribution power systems including power conversion, management of energy by means of demand side management and energy storage taking into consideration power markets. More than 120 papers were included in the conference's technical programme, and the topics covered a broad spectrum within the field of renewable power generation. A selection of papers presented at the Naples conference were considered appreciable by the Conference Session Chairs and invited to submit to the IET Renewable Power Generation journal. After extensive peer review, two significant papers were accepted for publication by the Editor-in-Chief and the Associate Editor. The accepted papers cover both generation by renewable sources and distribution of the energy treating, in particular, aspects related to the integration of renewable sources in the grid and the control and management of a distributed generation network. K. Musasa, M. N. Gitau and R. C. Bansal, in their paper “Dynamic analysis of DC-DC converter internal to an offshore wind farm”, have analysed the automatic generation control (AGC) problem and considered it in interconnected power systems with doubly-fed induction generator (DFIG)-based wind turbines. A non-linear least squares support vector machines (LS-SVM)-based AGC regulator is proposed; this is trained from an off-line data set obtained from designing and implementing the robust controller to power a system under diverse operating conditions and area load changes. An investigation of time response plots reveal that the designed LS-SVM-based AGC regulator shows promising performance for power systems with governor dead-band non-linearity when compared to that obtained with multi-layer perceptron neural networks and conventional PI-based AGC regulators for a wide range of parametric uncertainties and area load disturbances occurring in the area of the power system. In their paper, M. Cresta, F. M. Gatta, A. Geri, M. Maccioni, A. Mantineo and M. Paulucci analyse possible strategies for the control and management of an LV network with distributed generation connected at LV (consisting in photovoltaic power plants equipped with the last generation of inverters) and electric vehicles charging stations (EVCSs). Various possible scenarios have been studied: the LV network as actually operated; the network operated with the EVCS and the network operated with the EVCS and the NAS storage system. The evolution of voltage levels at the LV busbar, of power-factors at the secondary substation and of energy losses in the LV network have been calculated. By analysing the results, it was found that the installation of the EVCS itself does not present any criticality for the considered distribution network. A proposed optimal power flow detects optimal strategies for the management of reactive power flow supplied by the PV inverter and for the control of charge/discharge cycles of the NAS. From an economic point of view, the installation of the NAS appears to be unjustifiable because of both the high investment cost and the increase in operating costs (due to the additional energy losses). Lastly, the “demand response” practice, applied to “secondary substation” customers does not provide significant benefits on the network operation. However, this practice may generally constitute a convenient and effective solution for the implementation of the “load shifting” along a daily load diagram.

Optimal Automatic Generation Control of Asynchronous Power Systems Using Output Feedback Control Strategy with Dynamic Participation of Wind Turbines

—This article presents the design of optimal output feedback automatic generation control regulators for an interconnected power system with dynamic participation of doubly fed induction generator based wind turbines. The power systems consist of plants with hydro-thermal turbines and are interconnected via parallel AC/DC links. Efforts have been made to propose optimal automatic generation control regulators based on feedback of output state variables, which are easily accessible and available for the measurement. The designed optimal output feedback automatic generation control regulators are implemented, and the system dynamic responses for various system states are obtained considering 1% load perturbation in one of the areas. The dynamic performance is compared with that obtained with optimal automatic generation control regulators designed using full state vector feedback. The pattern of closed-loop eigenvalues is also determined to test the system stability.

Automatic Generation Control in an Interconnected Power System Incorporating Diverse Source Power Plants Using Bacteria Foraging Optimization Technique

This article presents automatic generation control (AGC) of a two-area interconnected power system with diverse energy sources using the bacteria foraging optimization technique. The control areas of interconnected power systems consist of hydro, thermal, and gas power plants. In this study, the proportional-integral-derivative (PID) structures of AGC regulators are designed for various case studies identified herein. An artificial intelligent optimization algorithm using the modeling behavior of E. Coli bacteria present in human intestines, is applied to tune the gains of PID structured AGC regulators. The closed-loop system dynamic response plots are obtained with designed AGC regulators for various power system models. The effectiveness of the proposed AGC regulators is demonstrated in the wake of a 1% step load disturbance in one of the control areas. It has been shown that the system dynamic responses subject to a step load disturbance are superior over other power plant combinations in a control area with only thermal and gas power plants participating in the AGC schemes, and it is sluggish/poor when only hydro power plants participated in the AGC scheme as one of the diverse sources in the power system.

Study on Dynamic Participation of Wind Turbines in Automatic Generation Control of Power Systems

This article presents the design of optimal automatic generation control regulators for an interconnected power system incorporating dynamic participation of doubly fed induction generator based wind turbines. Two power system models are identified for the investigations. Power system model 1 is a two-area interconnected power system consisting of identical plants with non-reheat turbines, whereas power system model 2 consists of identical plants with non-reheat turbines and dynamic participation of doubly fed induction generator based wind turbines in both areas. An AC tie-line is used as area interconnection in both power system models. The designed optimal automatic generation control regulators are implemented, and the system dynamic responses for various system states are obtained considering a 1% load disturbance in one of the areas. The pattern of closed-loop eigenvalues is also determined to investigate system stability. From the investigations carried out in the work, it is inferred that the incorporation of doubly fed induction generator based wind turbines in both areas has appreciably improved the dynamic performance of the system under consideration. Moreover, system stability is ensured for both power system models.

LS-SVM Based AGC of an Asynchronous Power System with Dynamic Participation from DFIG Based Wind Turbines

Modern power systems are large and interconnected with growing trends to integrate wind energy to the power system and meet the ever rising energy demand in an economical manner. The penetration of wind energy has motivated power engineers and researchers to investigate the dynamic participation of Doubly Fed Induction Generators (DFIG) based wind turbines in Automatic Generation Control (AGC) services. However, with dynamic participation of DFIG, the AGC problem becomes more complex and under these conditions classical AGC are not suitable. Therefore, a new non-linear Least Squares Support Vector Machines (LS-SVM) based regulator for solution of AGC problem is proposed in this study. The proposed AGC regulator is trained for a wide range of operating conditions and load changes using an off-line data set generated from the robust control technique. A two-area power system connected via parallel AC/DC tie-lines with DFIG based wind turbines in each area is considered to demonstrate the effectiveness of the proposed AGC regulator and compared with results obtained using Multi-Layer Perceptron (MLP) neural networks and conventional PI regulators under various operating conditions and load changes.

AGC of two area power system interconnected by AC/DC links with diverse sources in each area

This paper presents a comprehensive study on dynamic performance of a more realistic power system with diverse sources in each area and interconnected via parallel AC/DC transmission links. The power generation in each area is based on diverse sources such as thermal, hydro and gas. To carry out the investigations, optimal Automatic Generation Control (AGC) regulators are designed and implemented by considering an example of a two area power system for 1% step load disturbance in one of the control areas. In order to assess the improvement in stability of this realistic power system with DC link in parallel with AC tie-line as interconnection, eigenvalue study is also conducted. It has been shown that the transient response of power system subject to a step load disturbance is sluggish/poor in the presence of hydro as one of the diverse source in the power system. But an appreciable improvement in system dynamic performance is achieved by considering parallel AC/DC links as interconnection between areas rather than using AC tie lines only.