JOURNAL OF ELECTRICAL POWER SYSTEMS
Year:2012 | Volume:1 | Issue:1|Papers Count:8

In restructured power systems, Independent System Operator (ISO) uses a lot of tools to minimize the costs while delivering the power to consumers in a reliable and stable state. To minimize the costs, ISO uses security-constrained unit commitment (SCUC), and schedules unit reserves for reliability point of view. For stability point of view, ISO implements optimal power flow (OPF) to secure the bus voltage margins, and to reduce the losses. In this paper, an algorithm is proposed to include this optimal generation scheduling with transmission lines parameters, and a case study is implemented to verify the proposed algorithm.

Power systems are faced with numerous contingencys. Each of these contingencys can have different effects on the network. Therefore, it is important that these contingencys are studied. This paper presents a new approach to determine optimal location of Unified Power Flow Controller (UPFC) and Phase Shifter Transformer (PST) under single line contingency (N-1 contingency). The optimization objective is chosen to minimize the average loadability on highly loaded transmission lines. Optimization problem is implemented with nonlinear programming (NLP) method in MATLAB and GAMS software on the IEEE 30 bus test systems. In this approach contingency ranking and comparison between UPFC and PST devices is done. The simulation results demonstrate the effectiveness of the proposed algorithm to enhance the system security and minimize the average loadability under single line contingency.

The smart grid utilizing will bring favorable efficiency in the distribution networks. Correct usage of this knowledge can be beneficial for both utilities and customers. In the conventional power systems, the distribution networks are intermediate between the transmission and generation and they consider as passive parts. By using smart grids and micro grids like wind turbines, fuel cells, CHPs and …, the distribution networks convert to active part of the power systems. This subject causes that many problems of the power system like power flow, stability, reliability, security and short circuit and … are impressed by these grids. In these situations, using the micro grids will certainly affect on the control systems, power control center and operation of the distribution networks. On the other hand, it is need to determining the generation time and value of the energy source and also time controlling of the home equipments for applying the load and energy management programs in point of client electrical cost reduction and their adhesions for cooperation in smart grid plans. In this paper, it is tried to evaluating these networks in different aspects as power quality, economic dispatch and protection control.

Deregulation policy has caused some changes in the concepts of power systems reliability assessment and enhancement. In this paper, generation reliability and market price are considered, and a method for their assessment using power plants' flexibility and neural networks is proposed. Also, due to the stochastic behavior of power market and generators’ forced outages, Monte Carlo Simulation is used for reliability evaluation. The proposed method is assessed on IEEE-Reliability Test System with satisfactory results. The results further showed that if price elasticity of demand increases, reliability will improve and market price will decrease. Also, flexible plants can merger and uplift the market price.

In restructured systems, locational marginal prices are highly increased in load peak and short circuit durations. Uses of energy management programs such as demand response program are one of the tools that can help to independent system operator for locational marginal prices’ control. In this paper, optimal implementation of emergency demand response program is considered for locational marginal prices control. Also, imperialist competition algorithm is used to optimize the proposed prices for consumers that are connected to different buses for both peak and emergency states that lead to minimize the cost of system and the maximum of public benefit arising from the implementation of the emergency demand response program. The curve of New York regional load and IEEE 14 buses test system is used to test the proposed approach. The results are comprised with each other in two modes: without implementing energy management programs and when the proposed price is the same for all consumers.

In order to improve power quality of electrical distribution networks, a lot of methods are used that their most efficient and effective is the usage of custom power equipment. This equipment has designed based on voltage source inverter and each of its equipment is suitable for compensation of some power quality phenomenon. Distribution Static Synchronous Compensator (D-STATCOM) is one of the custom power equipment that bus reactive power is controlled by current injection and is caused to fix bus voltage in installment location. D-STATCOM performance is simulated based on sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) using PSCAD/EMTDC software in improvement of voltage sag and swell, and these modulations are used to produce switching signals of voltage source inverter the equipment. D-STATCOM performance is compared with each other applying these modulations. D-STATCOM based on SVPWM restores voltages sag and swell effectively. In addition, it produces lower distribution harmonic.

In this paper, we use Thyristor Controlled Series Capacitor (TCSC) and Power System Stabilizer (PSS) simultaneous controllers to increase the stability of the single machine infinite bus (SMIB) and two-machine power system. Then, we use the Particle Swarm Optimization (PSO) algorithm to optimize the parameters of simultaneous PSS and TCSC controllers. The dynamic instability is created as a result of the imbalance between input mechanical power and output electric power and the low damping torque. One of the effective alternatives to solve this problem is to install a PSS in the generators to damp the electro-mechanical oscillations made by the sudden load disturbances. Application of the TCSC is the most effective reactive compensation method in the long transmission lines and are considered as the useful devices to control the power transmitted from these lines. PSS and TCSC can combine with each other for further stability, therefore their coordination is very important. The simulation results in this paper show an appropriate function of simultaneous PSS and TCSC controllers after creating the disturbance in the power system.

Multi-objective optimization is one of the most important problems in engineering, so a lot of ways have been used by researchers during past years. Most of ways that have been used in the past were based on single-objective problems that they had to change to multi-objective ways by using different methods, but now we have some ways that are multi-objective basically. For example NSGA-II is one of the most important ways for this goal. So in this paper after introduce algorithm and Microgrid networks we use this algorithm in for solving a multi-objective problem in a 14 buses Microgrid for two objective such as cost and pollution and after that we compare results of algorithm with classic way and at the end result of Pareto curve will show quality of using this algorithm in Microgrids.