G. V. Nagesh Kumar

Fault ride-through enhancement using an enhanced field oriented control technique for converters of grid connected DFIG and STATCOM for different types of faults

With increase in electric power demand, transmission lines were forced to operate close to its full load and due to the drastic change in weather conditions, thermal limit is increasing and the system is operating with less security margin. To meet the increased power demand, a doubly fed induction generator (DFIG) based wind generation system is a better alternative. For improving power flow capability and increasing security STATCOM can be adopted. As per modern grid rules, DFIG needs to operate without losing synchronism called low voltage ride through (LVRT) during severe grid faults. Hence, an enhanced field oriented control technique (EFOC) was adopted in Rotor Side Converter of DFIG converter to improve power flow transfer and to improve dynamic and transient stability. A STATCOM is coordinated to the system for obtaining much better stability and enhanced operation during grid fault. For the EFOC technique, rotor flux reference changes its value from synchronous speed to zero during fault for injecting current at the rotor slip frequency. In this process DC-Offset component of flux is controlled, decomposition during symmetric and asymmetric faults. The offset decomposition of flux will be oscillatory in a conventional field oriented control, whereas in EFOC it was aimed to damp quickly. This paper mitigates voltage and limits surge currents to enhance the operation of DFIG during symmetrical and asymmetrical faults. The system performance with different types of faults like single line to ground, double line to ground and triple line to ground was applied and compared without and with a STATCOM occurring at the point of common coupling with fault resistance of a very small value at 0.001Ω.

Congestion management of power system with interline power flow controller using disparity line utilization factor and multi-objective differential evolution

The restructuring of the electric power market has led to complex power transmission congestion problems. Additionally, scheduled power flows in the transmission line, as well as spontaneous power exchanges have also risen sharply in recent years. The proper placement of IPFC can improve the transmission line congestion problem to a great extent. This paper proposes a disparity line utilization factor (DLUF) for the optimal placement of IPFC to control the congestion in transmission lines. DLUF determines the difference between the percentages of Mega Volt Ampere utilization of each line connected to the same bus. The IPFC is placed in the lines with maximum DLUF. A multiobjective function consisting of reduction of active power loss, minimization of total voltage deviations, minimization of security margin and minimization of installed IPFC capacity is considered for the optimal tuning of IPFC using differential evolution algorithm. The proposed method is implemented for IEEE-30 bus test system under different loading conditions and the results are presented and analyzed to establish the effectiveness on the reduction of congestion.

A Comparative Study of BAT and Firefly Algorithms for Optimal Placement and Sizing of Static VAR Compensator for Enhancement of Voltage Stability

Modern electric power utilities are facing many challenges due to increasing power demand but the growth of power generation and transmission has been limited due to limited resources, environmental restrictions and right-of-way problems. These problems can be minimized by installing Flexible Alternating Current Transmission System (FACTS) devices in modern electric utilities to optimize the existing transmission system. Most effective use of the FACTS devices depend on the fact, how these devices are placed in the power system, i.e. the location and size. An optimal location and size of FACTS devices allows controlling its power flows and thus enhances the stability and reliability of the power systems. In this paper, Firefly Algorithm (FA) and BAT Algorithm (BAT) have been applied and compared to determine the optimal location and size of Static VAR Compensator (SVC) in a power system to improve voltage stability subjected to minimize the active power losses, fuel cost, branching loading and voltage deviation. The effectiveness of the proposed algorithms and improvement of power system stability has been demonstrated on IEEE 57 bus system using fast voltage stability index. The results obtained with variation of parameters of Firefly and BAT Algorithms has been studied and compared with Genetic Algorithm. The results are presented and analyzed.

Differential Evolution Based Tuning of Proportional Integral Controller for Modular Multilevel Converter STATCOM

This paper discusses differential evolution algorithm for tuning of proportional integral controller in modular multilevel converter based STATCOM applications. Unlike conventional VSC based converters, an MMC is known for its distinctive features such as modularity, low harmonic content and flexibility in converter design. The MMC-STATCOM is capable of reactive power compensation, simultaneous load balancing and harmonic cancellation. Differential evolution algorithm is used to tune the proportional integral controller of STATCOM. The proposed model is verified in MATLAB/Simulink and the results are well in proximity with the theoretical analysis.

Multi-Objective Optimal Power Flow using BAT Search Algorithm with Unified Power Flow Controller for Minimization of Real Power Losses

In this paper a multi objective optimal power flow OPF is obtained by using BAT search algorithm BAT with Unified power flow controller UPFC. UPFC is a voltage source converter type Flexible Alternating Current Transmission System FACTS device. It is able to control the voltage magnitudes, voltage angles and line impedances individually or simultaneously. UPFC along with BAT algorithm is used to minimize the total real power generation cost, real power losses in OPF control. The BAT algorithm based OPF has been examined and tested on a 5 bus test system and modified IEEE 30 bus system without and with UPFC. The results obtained with BAT algorithm are compared with Differential Evaluation DE.

Optimal power flow with static VAR compensator based on flower pollination algorithm to minimize real power losses

In this paper, the flower pollination algorithm is used to solve multi-objective problem of optimization in power systems. FPA is an algorithm founded on the pollinating feature of the flowering plants. The weighted sum technique with equal weights has been chosen to solve the multi-objective function. The functions considered are to minimize the power losses in transmission line and cost of the real power generation. In this paper, a shunt type of Flexible AC Transmission System (FACTS) device, namely, Static VAR Compensator (SVC) is used for the purpose of optimal power flow. The results presented here are achieved after performing simulations on an IEEE 14-bus system. The simulation results have been compared with Genetic algorithm (GA). The results show that FPA is more efficient than Genetic algorithm.

Optimal location of thyristor Controlled Series Capacitor to improve power system performance using Line based composite Index

The power system should be monitor frequently to overcome the problems of voltage stability, losses and to enhance the power flow. These problems can be controlled by using the Flexible AC Transmission System (FACTS) devices. They help to improve the voltage profiles and minimize the real power losses of the system. Thyristor Controlled Series Capacitor (TCSC) is one of the FACTS devices which are easier to control than other control devices. In this paper the placement of TCSC has been proposed based on composite index which consists of two line based indexes called Fast Voltage Stability Index (FVSI) and Line Utilization Factor (LUF) to improve the voltage stability and enhance the power transfer capability by minimizing the real power losses. Further for sizing of the TCSC and generation reallocation multi objective function is considered, which consists of real power generation cost, voltage deviation and real power losses. Krill Herd (KH) algorithm is used to solve the multi objective problem. Krill Herd is a nature inspired algorithm. For the verification of the proposed method, simulation is performed on IEEE 14 bus system and it is observed that results were efficient and there is an effective reduce in the losses of the system, voltage deviation and real power generation cost.

Harmonic comparison with modular multilevel converter of multi connection wind energy systems

Presently the global wind energy capacity is increasing rapidly and it has become the fastest developing renewable energy technology. The early technology used in wind turbines was based on squirrel cage induction generators directly connected to the grid through normal converters. In this paper, a new modular multilevel converter based integrated wind energy system for reducing harmonics with different pulse width modulation techniques is proposed. Modular multilevel converter is the state of art technology and hence this converter is integrated with wind energy system. In this paper, harmonics, voltage and current responses at different loads at different wind conditions by using new proposed integrated wind energy system connected to a modular multilevel converter through multi winding transformer are compared. The proposed model of modular multilevel converter integrated to the wind energy system is developed in MATLAB/SIMULINK.

Thyristor Controlled Series Capacitor placement and sizing using BAT search optimizer to enhance power flow

Now-a-days, the power systems networks are more complex. It is difficult to construct the new transmission lines. So to enhance the power transfer capabilities of the transmission lines, Flexible AC Transmission System (FACTS) devices are used. Out of FACTS devices, Thyristor Controlled Series Capacitor (TCSC) is the most suitable device for enhancing the power flow in transmission line. In this paper, TCSC is incorporated in BAT algorithm based optimal power flow to enhance the power flow and reduce the real power losses. BAT search algorithm is also used for the optimal tuning of TCSC. Optimization is done by using GA and BAT algorithms on a 5-bus test system for obtaining voltage magnitude, active power losses, fuel cost and also the parameters of the device to be installed. The results obtained by using a MATLAB code are presented and analyzed.

A Computational Comparison of Swarm Optimization Techniques for Optimal Load Shedding under the presence of Unified Power Flow Controller to Avoid Voltage Instability

Voltage instability has become a serious threat to the operation of modern power systems. Load shedding is one of the effective countermeasures for avoiding instability. Improper load shedding may result in huge technical and economic losses. So, an optimal load shedding is to be carried out for supplying more demand. This paper implements BAT and Firefly algorithms for solving the optimal load shedding problem to identify the optimal amount of load to be shed. This is applied for a multi objective function which conatins minimization of amount of load to be sheded, active power loss minimization and voltage profile improvement. The presence of with and with out Unified Power Flow Controller UPFC on load shedding for IEEE 57 bus system has been presented and analyzed. The results obtained with BAT and Firefly Algorithms were compared with Genetic Algorithm GA.