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 **load** **frequency** **control** of multi-area multi- source **power** **system** in **deregulated** environment. The Boiler dynamics, Generation Rate Constraint (GRC) and Governor Dead Band (GDB) have been considered to have a more real- istic **power** **system**. The **system** has been investigated all possi- ble of **power** transactions that take place **under** **deregulated** 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.

Show more
19 Read more

Redox Flow Battery (**RFB**) is connected to the **power** **system** 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 [12]. 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

Show more
13 Read more

It is perceived in the **power** **system** 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) [22], genetic **algorithm** (GA) [23], biogeography-based optimization (BBO) [24,25], krill herd **algorithm** (KHA) [26], teaching learning based optimization (TLBO) [27,28], bacteria foraging optimization (BFOA) [7], gravitational search **algorithm** (GSA) [29], **hybrid** PSO-pattern search (hPSO- **PS**) **algorithm** [30], **hybrid** FA-**PS** [31], Tabu search **algorithm** (TSA) [32], quasi-oppositional harmony search **algorithm** (QOHSA) [33,34], BAT **algorithm** [35], backtracking search **algorithm** (BSA) [36], were proposed in the literature. Padhan et al. [4] have designed an optimal LFC by employing firefly **algorithm** (FA) and showed its superiority over other similar optimization techniques. Nanda et al. [6] demonstrated that BFOA has better tuning ability than GA and Zeigler–Nichols (ZN) based controller for an intercon- nected **power** **system**. An improved PSO **algorithm** was elaborated in [8] for a nonlinear multi-area **hybrid** **power** **system** comprising thermal-hydro-gas **power** plant. In [9], lozi map chaotic optimiza- tion **algorithm** was proposed for the design of PID-controller to solve LFC problem in **power** **system**. In [24,25], BBO **algorithm** was successfully designed and applied to a nonlinear intercon- nected **power** **system** 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

Show more
21 Read more

Here a two area four unit **deregulated** **system** 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 **deregulated** **power** environment. The proposed **algorithm** has been applied to tune the controller gains for a two area **deregulated** **power** **system** 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.

Show more
12 Read more

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 **control** **system** 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.

13 Read more

The AGC problem of three area **deregulated** **power** **system** 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 **power** **system**. 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 **deregulated** **power** **system** 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).

Show more
15 Read more

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** [1]. Therefore, **Load** **Frequency** **Control** (LFC) is very important for **power** **system** 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 [2]. A number of **control** techniques have been employed in the design of **load** **frequency** controllers in order to achieve better dynamic performance. Comparing the various types of **load** **frequency** 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.

Show more
10 Read more

ABSTRACT: **Load** **frequency** **control** plays significant role in **power** **system** to provide reliable and quality **power** all the time in Automatic generation **control** (AGC) **system**. For a multi area **hybrid** **power** **system** a controllercentred on the fuzzy logic approach is designed and tested in this paper. **Hybrid** **power** **system** 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.

Show more
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 .

Show more
[44] evaluated the operation of autonomous wind– diesel **system** with the **load** **control**. The basic concept is obtained using the PSCAD/EMTDC computer simulation package. Next, the authors in [45] analyzed the effect of stand-alone **hybrid** **power** **system** consisting WTGs, DEG, FC, and A Eon **frequency** variation. Goyaetal. [46] discussed H∞ **control** theory based on droop characteristics for the **frequency** **control** 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 **hybrid** **power** **system** is proposed in [47]. The design of robust **frequency** controller of SMES in a **hybrid** wind–diesel **power** **system** by using loop shaping **control** technique and tuning of controller parameters using GA is discussed in [48]. The time- domain simulation for small-signal analysis of a **hybrid** **power** generation and energy storage **system** is evaluated in [49]. 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 **load** **power** demand. Also, the **system** **frequency** deviation should be controlled within a very small range efficiently. The effect of wind **power** generation on **power** **system** **frequency** **control** is presented in [50]. The LFC by coordination **control** of WTG and the double layer capacitor in an independent **hybrid** **power** generation renewable energy is presented in [51]. 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 [52]. The **frequency** **control** 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 [53]. The authors [54] presented a stable active **power** **control** of DFIG with wind **power** variations. Depending upon the rotor speed condition,

Show more
Traditional **load** shedding schemes are designed by using a static model of **power** **system** 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 **power** **system** stability in the recent blackouts.

Show more
39 Read more

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 **control** **algorithm** 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**.

Show more
11 Read more

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

Show more
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.

Show more
Abstract— In the **power** **system**, any sudden changes in the **load** leads to **frequency** deviation. But the **frequency** should remain nearly constant for the satisfactory operation of a **power** **system**. So the **Load** **Frequency** **Control** (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 **power** **system**. The addition of small capacity energy storage unit in each area of the **power** **system** 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 **Load** **Frequency** **Control** model of two area interconnected hydro **power** **system**. The proposed work consist of two area interconnected hydro **power** **system** 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 **Load** **Frequency** **Control** in an interconnected hydro **power** **system** 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.

Show more
10 Read more

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.

Show more
11 Read more

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.

Show more
16 Read more

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 [24], 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 [25]. A step-by- step coordinated design procedure for PSS and automatic voltage regulator (AVR) in a strongly coupled **system** is described in [26], which the proposed design approach is useful small-signal complement to established large-signal transient simulation studies. An approach for the design of multiple **power** **system** stabilizers in two-area non reheat thermal **system** for three pre-defined cases is proposed in [27], 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 [28], which the optimization of controller parameters and robustness evaluation of the **control** technique is done on the

Show more
10 Read more