اقدامات کنترل پیشگیرانه بهینه با استفاده از روش برنامه ریزی خطی فازی چند هدفه

This paper presents a proposed procedure depends on the multi-objective fuzzy linear programming (MFLP) technique to obtain the optimal preventive control actions, for power generation and transmission line flows, to overcome any emergency conditions. The proposed procedure is very significant to eliminate violation constraints and to give an optimal preventive action for multi-operating conditions. The proposed multi-objective functions are: minimizing the generation cost function, maximizing the generation reserve at certain generator, maximizing the generation reserve for all generation system and maximizing the preventive action for one or more critical transmission line. Numerical examples are presented in order to show that the proposed MFLP technique achieves a feasible economical cost in addition to the maximal preventive control actions for power systems.

In normal operation of power systems, the constrained optimal dispatch imposed by active and reactive power generation and/or transmission line capacities must be satisfied. It has been recognized for many years that the economic dispatch may be unsafe, that is, it may not be capable to keep the system in a normal state after a major disturbance (sudden increasing in load and/or generation outages). This led to the concept of system preventive control action, and to the view that the objective of system operation is to keep the system in a normal state during the relatively long periods between disturbances. This insures that, the system will not depart from the normal state on the occurrence of a major disturbance. The approach of security regions was first proposed by Hnylicza et al. [1]. Fischl et al. [2], [3] and [4] developed methods to identify security regions and utilize these regions in contingency selection transmission planning. The idea of security regions was extended by Banaker and Galiana [5], where a method to construct the so-called “security corridors” is suggested for security assessments. Using the duality concept of mathematics programming, Dersin and Levis [6] characterized explicitly the feasibility sets of load demands. Wu and Kumagei [7] derived hyperbox subsets of the steady-state security regions based on nonlinear load flow equations. Liu [8] presented a method to compute maximal steady-state security regions based on dc load flow model. But the numerical testing indicates that the algorithms used to expand the initial region produces only nearly maximal security regions. The fuzzy set theory is a natural and appropriate tool to represent inexact relations [9]. It has been applied for optimal power flow and scheduling with crisp constraints [10]. Based on the fuzzy set theory, an optimal power flow problem can be modified to include fuzzy constraints and fuzzy objective functions. A fuzzy set method was applied to the optimal power flow problem [11]. Another application of fuzzy logic to the unit commitment problem was demonstrated in Ref. [12]. A MFLP method was presented in Ref. [13] to obtain the optimal reactive power transmission loss and maximize voltage stability margin. In this paper, the MFLP is applied to effectively model for maximizing the preventive control actions.

This paper presents a proposed procedure to obtain the optimal preventive control actions using the (MFLP) technique to overcome any emergency may occur in power systems. This procedure allows the power system operator to ramp the power generation and transmission lines constraints corresponding to the amount of the preventive control actions requirements. The MFLP is successfully applied to achieve multi-objective functions, which are required to obtain the optimal preventive actions in power systems. When the preventive actions are prepared, there are different constraints can be increased to avoid any emergency condition and to steer the system to the normal state. With the use of the MFLP technique, a smooth variations of the control actions that allow the decision-maker to solve the emergency condition problem with minimum incremental generation costs. Therefore, the operator can trade off between preparing of sufficient preventive action with increasing the generation cost or making load shedding.