In this paper, an attempt has been made for the ﬁrst time to apply a hybrid Differential Evolution (DE) and Pattern Search (PS) optimized Modiﬁed Integral Derivative (MID) controller for loadfrequencycontrol of multi-area multi- source powersystem in deregulated environment. The Boiler dynamics, Generation Rate Constraint (GRC) and Governor Dead Band (GDB) have been considered to have a more real- istic powersystem. The system has been investigated all possi- ble of power transactions that take place underderegulated environment. The proposed hybrid technique takes advantage of global exploration capabilities of DE and local exploitation capability of PS. The advantage of proposed hDE-PS tech- nique over DE and Genetic Algorithm (GA) has also been demonstrated. It is observed that better dynamic performance is obtained with proposed hDE-PS optimized MID controller compared to I and ID controller. Uniﬁed Power Flow Controller (UPFC) is added in the tie-line for improving the system performance. Additionally, Redox Flow Batteries (RFBs) are included in area-1 along with UPFC in order to improve the system performance. It is observed that in all the cases (poolco based, bilateral based and contract violation based) the deviation of frequency becomes zero in the steady state with coordinated application of UPFC and RFB which assures the AGC requirements. Additionally, sensitivity analy- sis is carried out to show the robustness of the MID controller under poolco based scenario. From simulation results, it is observed that the parameters of the proposed hDE-PS opti- mized MID controllers are need not be reset even if the system is subjected to wide variation in loading condition and system parameters. Finally, the simulation results are demonstrated that the proposed approach provides desirable performance against random step load disturbance.
Redox Flow Battery (RFB) is connected to the powersystem of both areas, in which the input given is the change in frequency (real power) of that area and output will be as per the load requirement and either charges or discharges the power. As RFB has fast response, hunting due to delay in response does not occur . Because of this reason, ACE is fed directly as a command signal LFC to control the output of RFB. Transfer function model of RFB is as shown in Figure 5 and the change in power (ΔP rfb ) is given Equation
It is perceived in the powersystem that parameter values in the various power generating units, viz. governors, turbines, genera- tors etc., are endlessly varying w.r.t time subject to system and power flow condition. Thus, the controller parameters design at normal operation may not able to give satisfactory performance under external disturbed and/or parameter uncertainty condition. To ensure robustness and to preserve the system stability, various populations based meta-heuristic optimization techniques such as particle swarm optimization (PSO) , genetic algorithm (GA) , biogeography-based optimization (BBO) [24,25], krill herd algorithm (KHA) , teaching learning based optimization (TLBO) [27,28], bacteria foraging optimization (BFOA) , gravitational search algorithm (GSA) , hybrid PSO-pattern search (hPSO- PS) algorithm , hybrid FA-PS , Tabu search algorithm (TSA) , quasi-oppositional harmony search algorithm (QOHSA) [33,34], BAT algorithm , backtracking search algorithm (BSA) , were proposed in the literature. Padhan et al.  have designed an optimal LFC by employing firefly algorithm (FA) and showed its superiority over other similar optimization techniques. Nanda et al.  demonstrated that BFOA has better tuning ability than GA and Zeigler–Nichols (ZN) based controller for an intercon- nected powersystem. An improved PSO algorithm was elaborated in  for a nonlinear multi-area hybridpowersystem comprising thermal-hydro-gas power plant. In , lozi map chaotic optimiza- tion algorithm was proposed for the design of PID-controller to solve LFC problem in powersystem. In [24,25], BBO algorithm was successfully designed and applied to a nonlinear intercon- nected powersystem and showed its superiority over other opti- mization methods. However, the performance of BBO is highly determined by the maximum emigration and immigration rate, mutation probability, the step size of integration, habitat modifica- tion
Here a two area four unit deregulatedsystem with considering physical constraints such as GRC and TD in presence of IPFC and RFB with PIDF controller and all these parameters are tuned with Particle Swarm Optimization (PSO) algorithm. The results are compared with DE and BFOA algorithms. Here considering some parameters in PSO technique like, Swarm size(=50), Step size (=50), problem dimension(=8) and parameters (c 1 = c 2 = 1.02 and w = 0.9). Then corresponding tuned parameters and output
In this work, a new a new global search optimization algorithm, the Artificial Cooperative Search Algorithm (ACS) has been introduced for the solution of LFC problem in deregulatedpower environment. The proposed algorithm has been applied to tune the controller gains for a two area deregulatedpowersystem with coordinated control of TCPS, RFB and AC-DC parallel tie-lines and has been tested under various possible bilateral contracts. The simulation results reveal that the coordinated operation of TCPS, RFB and AC-DC tie-line along with controller designed using ACS algorithm suppresses the frequency deviations and tie-line power deviations effectively. The area frequency responses and tie-line power flow response exhibit less overshoot less undershoot and minimum settling time in the presence of TCPS, RFB and AC-DC parallel tie-lines.
They can perform poorly in some applications. PID controllers, when used alone, can give poor performance when the PID loop gains must be reduced so that the controlsystem does not overshoot, oscillate or hunt about the control set point value. A problem with the Derivative term is that small amounts of measurement or process noise can cause large amounts of change in the output.
to meet the increased electrical load.The synchronous (constant speed) governor cannot be used if two or more generators are electrically connected to the same system since each generator would have to have precisely the same speed setting or they would fight each other, each trying to pull the system’s speed (or frequency) to its own setting. To run two or more generating units in parallel, the speed governors are provided with a feedback signal that causes the speed error to go to zero at different values of generator output.
The AGC problem of three area deregulatedpowersystem is considered here with the non-linearities. Hybrid combinations of Neuro and fuzzy is used as a controller to evaluate frequency and tie-line responses of multi source powersystem. The simulations are carried out for the possible electricity contracts and also for large de- mand variations using HCPSO, RCGA, ANN controllers and the results were compared. Table 1 depicts tie line power deviations for all the scenarios using the various controllers. The values show that the tie line power ex- change between the areas, ANFIS controller reaches the exact exchange of power between the areas with mini- mum deviations compared to other controllers. Table 2 shows the comparison of GENCO power deviation for the three scenarios with theoretical and the simulated values by Equation (10). In this ANFIS accomplish its controller task perfectly in getting the same value as it gains in theoretical calculation. The plant parameters for three area deregulatedpowersystem used for modeling the control structure is presented in Table 3. The results illustrate that proposed controller proves good dynamic performance over the others in terms of settling time, overshoot and undershoot (Table 4 and Table 5).
Nowadays, electricity generation is very important because of its increasing necessity. The dynamic behavior of the system depends on disturbances and on changes in the operating point. The quality of the generated electricity in power stations is depending on the system output, it has to be of constant frequency and should maintain the scheduled power . Therefore, LoadFrequencyControl (LFC) is very important for powersystem in order to supply reliable and quality electric power. The conventional controllers such as PI, PID can give control action for one particular operating condition, where as in real situation the parameters change from time to time. So it is difficult to arrange the required gains to achieve zero frequency deviation. Hence there is a necessity to provide automatic correction. However research is going on and several methods are developed to overcome this difficulty . A number of control techniques have been employed in the design of loadfrequency controllers in order to achieve better dynamic performance. Comparing the various types of loadfrequency controllers, the most common and widely employed is the conventional proportional (PI) controller. Conventional controller is simple for implementation but gives large frequency deviation. Most of state feedback controllers based on linear optimal control theory have been proposed to achieve better performance. Fixed gain controllers are designed at nominal operating conditions and fail to provide best control performance over a wide range of operating conditions. So to keep the system performance near to its optimum it is desirable to track the operating conditions and use updated parameters to compute the control. Adaptive controllers with self adjusting gains settings have been proposed for LFC to achieve the function compared to PI Controller.
ABSTRACT: Loadfrequencycontrol plays significant role in powersystem to provide reliable and quality power all the time in Automatic generation control (AGC) system. For a multi area hybridpowersystem a controllercentred on the fuzzy logic approach is designed and tested in this paper. Hybridpowersystem consist of three area having thermal, thermal with re-heater and hydro generating units connected through tie lines. The system model will be designed in MATLAB Simulink and the comparative analysis will be done with the conventional PI controller based control scheme.
voltage, impedance and the phase angle in transmission circuit and hence control the power flow. Among the converter based FACTS devices Static Synchronous Compensator (STATCOM) and Unified Power Flow Controller (UPFC) are considered in this paper. Static and dynamic analysis of the standard 5 bus system is done in MATLAB .The result of network with and without using UPFC and STATCOM are compared in terms of active and reactive power flows in the line and at the bus to analyze the performance of the devices Iinjected voltage, Injected phase , phase distortion are also shown graphically .
 evaluated the operation of autonomous wind– diesel system with the loadcontrol. The basic concept is obtained using the PSCAD/EMTDC computer simulation package. Next, the authors in  analyzed the effect of stand-alone hybridpowersystem consisting WTGs, DEG, FC, and A Eon frequency variation. Goyaetal.  discussed H∞ control theory based on droop characteristics for the frequencycontrol by using parallel operated battery in isolated island. The PSO based design of the robust fuzzy logic-based-PID controller for LFC in isolated wind–diesel hybridpowersystem is proposed in . The design of robust frequency controller of SMES in a hybrid wind–diesel powersystem by using loop shaping control technique and tuning of controller parameters using GA is discussed in . The time- domain simulation for small-signal analysis of a hybridpower generation and energy storage system is evaluated in . The authors presented that the power generation from the WTG, PV, DEG, and FC with energy stored or released from the BESS and FESS can effectively meet the variations in loadpower demand. Also, the systemfrequency deviation should be controlled within a very small range efficiently. The effect of wind power generation on powersystemfrequencycontrol is presented in . The LFC by coordination control of WTG and the double layer capacitor in an independent hybridpower generation renewable energy is presented in . In the suggested method, the load variation is decreased to low and high frequency domain by FC and capacitor, respectively. The GA based PID controller for LFC of independent hybrid generation systems consisting different renewable energy generation and storage systems such as three a DEG, FCs, WTGs, and a PV, a BESS, and an FESS is presented in . The frequencycontrol of wind energy storage system (BESS taken as energy storage system) based on model predictive control approach; having tested on real measurement from a power grid is discussed in . The authors  presented a stable active powercontrol of DFIG with wind power variations. Depending upon the rotor speed condition,
Traditional load shedding schemes are designed by using a static model of powersystem which are set to disconnect fixed amounts of load using a predetermined fixed number of step sizes and usually do not provide optimized settings for different system conditions. These are conservative in the amount of load effectively shed and the frequency excursion ranges of UFLS schemes are too wide; because of neglecting the actual system state and magnitude of disturbance. In addition, it was found that the present schemes were not safe enough to maintain powersystem stability in the recent blackouts.
network and fuzzy logic controllers are used. The various activities that are performed by DSTATCOM are transients elimination and balancing of unbalanced loadsVarious that has been demonstrated in Zero Voltage Regulation and Power Factor Correction modes of DSTATCOM with dc voltage regulation. For the compensation or suppression of harmonics in nonlinear loads the DSTATCOM shows a satisfactory performance which can be seen in the simulation results of DSTATCOM.The performance has been found better for this application because the extracted reference source currents exactly traced out,that means compensated the sensed source currents during the steady state as well as dynamic conditions i.e,under fluctuating conditions of the distribution system.Although the implemented methods provide the distortion levels within the specified IEEE standards(that means 5% of harmonics are allowed)achieving balanced load currents from the unbalanced system was a difficult task which leads to the flow of neutral current.The other problem that we have overcame here is without any overshoots/undershoots we have regulated the DC bus voltage of the DSTATCOM to the rated value.The description of the BP controlalgorithm is carried out by the simulation results under non linear loads.It can also be said that a DSTATCOM though it is conceptually similar to a STATCOM at the transmission level,its control scheme should be such that in addition to complete reactive power compensation, power factor correction and total harmonic distortion are also checked. The results are also verified for UPFC.Thus,the two objectives of the thesis were attained by modeling and simulating the neutral compensator and UPFC.Therefore the proposed method made an enhancement in the power quality in the distribution system.
The LFC problem has been augmented with valuable research contributions from time to time, such as LFC regulator designs to cope with parameter variations uncertainties, load characteristics, excitation control and parallel ac/dc transmission links. The microprocessor based LFC Controller, robust controller, self-tuning and adaptive controllers designs have also been presented. The most recent advance in this area is the application of concepts such as neural networks, fuzzy logic and genetic algorithms to tackle the difficulties associated with the design of LFC controllers for power systems with nonlinear models and/or insufficient knowledge about the system required for its accurate modeling. Apart from advances in control concepts, there have been many changes during the last decade or more, such as deregulation of the power industry and use of superconducting magnetic energy storage, wind turbines and photovoltaic cells as other sources of electrical energy to the system. Because of these, the control philosophies associated with the LFC problem have changed to accommodate their dynamics and their effects on the overall system dynamic performance. Generally, the methodologies of LFC controller designs can be categorized as
This FACTS topology provides much more flexibility than the SSSC for controlling the line active and reactive power because active power can now be transferred from the shunt converter to the series converter, through the DC bus. Contrary to the SSSC where the injected voltage Vs is constrained to stay in quadrature with line current I, the injected voltage Vs can now have any angle with respect to line current. If the magnitude of injected voltage Vs is kept constant and if its phase angle with respect to V1 is varied from 0 to 360 degrees, the locus described by the end of vector V2 (V2=V1+Vs) is a circle as shown on the phasor diagram. As is varying, the phase shift δ between voltages V2 and V3 at the two line ends also varies. It follows that both the active power P and the reactive power Q transmitted at one line end can be controlled.
Abstract— In the powersystem, any sudden changes in the load leads to frequency deviation. But the frequency should remain nearly constant for the satisfactory operation of a powersystem. So the LoadFrequencyControl (LFC) is an important issue in interconnected power systems. Energy storage units are very important for damping out the oscillations due to sudden changes in the powersystem. The addition of small capacity energy storage unit in each area of the powersystem can effectively restrain the system oscillations. Hence in this paper, the Superconducting Magnetic Energy Storage (SMES) Units and Super Capacitor Energy Storage (SCES) Units are incorporated in the LoadFrequencyControl model of two area interconnected hydro powersystem. The proposed work consist of two area interconnected hydro powersystem with SMES and SCES units has been designed to improve the dynamic performance of the system and also Integral Square Error (ISE) technique is used to obtain the optimal integral gain settings. The simulation result shows that the LoadFrequencyControl in an interconnected hydro powersystem with SCES units is considerably improved the system dynamics such as peak overshoot, settling time and frequency oscillations as compared to that of the system with SMES units and also the system without SMES and SCES units.
Fuzzy set theory derives from the fact that almost all-natural classes and concepts are fuzzy rather than crisp in nature. Fuzzy systems are model free systems in which all things are matters of degree. These systems use an inferential approach oriented towards system analysis and decision support. Fuzziness describes event ambiguity. It matters the degree, to which an event occurs, not whether it occurs or occurs in random to what degree it occurs is fuzzy. Whether an ambiguous event occurs - as when we say, "there is 20 percent chance of light rain tomorrow" - involves compound uncertainties, the possibility of fuzzy event emerges. Fuzzy systems store benefits of fuzzy associates or common sense "rules". Fuzzy programming admits degrees. They systems "reason” with parallel associate's interference. When asked a question or given an input, fuzzy systems fire each fuzzy rule in parallel, but to a different degree, to infer a conclusion or output. Thus fuzzy systems reason with sets, “fuzzy" or multi valued sets, instead of bivalent propositions. They estimate sampled functions from input to output. They may use linguistic or numeric samples for example they may use HEAVY, LONGER or number (relative) for the degree of fuzziveness. Fuzzy interpretations of data are a natural and intuitively plausible way to formulate and solve various problems in pattern recognition.
Abstract—Magnetic resonant wireless power transfer (WPT) is an emerging technology that may create new applications for wireless power charging. However, low eﬃciency resulting from resonant frequency drift is a main obstructing factor for promoting this technology. In this paper, a novel method of coordinating the operating frequency and load resistor is proposed to prevent frequency drift. The system eﬃciency and input impedance are obtained by solving the system equivalent equations. In addition, the new resonant frequencies can be obtained by solving the input impedance equations. Moreover, the process of the coordination method is illustrated. When resonant frequency drift occurs, the system can now operate at the resonant state, and the eﬃciency can be improved by using the proposed method. The WPT system via magnetic resonance coupling is designed. Simulated and experimental results validating the proposed method are given.
pole shift theory to control a low-head hydro power plant connected as a single machine to an infinite bus (SMIB) system is presented in , which a state-space model with two-input and two-output variables is considered. The prospective of parameter space methods for robust control and algorithm for a robust controller based a pole shifting adaptive control technique are presented in . A step-by- step coordinated design procedure for PSS and automatic voltage regulator (AVR) in a strongly coupled system is described in , which the proposed design approach is useful small-signal complement to established large-signal transient simulation studies. An approach for the design of multiple powersystem stabilizers in two-area non reheat thermal system for three pre-defined cases is proposed in , which the optimal parameters of the PSS are obtained employing genetic algorithm using integral of time multiplied absolute value of the error criteria. A fractional order PID for single area LFC for all three types of turbines (non-reheated, reheated and hydro turbines) is designed in , which the optimization of controller parameters and robustness evaluation of the control technique is done on the