The results of the proposed hybrid approach are compared with PSO, EP and hybrid EP. The comparison exhibits the effectiveness of the proposed approach in terms of solution quality and computation time.
This paper is organized as follows: The reactive power dispatch problem is introduced in section 2. The swarm technique is briefed in section 3. The direct search technique is introduced in section 4. The hybrid approach is explained in section 5. Test cases and numerical solutions are presented in section 6. Conclusions are drawn in section 7.
2.PROBLEM FORMATION.
The purpose of the ORPD is to minimize the system real power losses. The general ORPD with normal power system condition can be formulated [9] as follows:.
The objective function is represented as:.
P. N. Rajnarayanan Asst. Prof EEE.
Theni Kammavar Sangam College of Technology, Theni, Tamilnadu.
65.
where, PL.
nl.
State variables are restricted by adding them as a quadratic penalty terms to the objective function. Therefore, the equation (1) is changed to the following form: min.
Min.
= network real power loss.
= number of lines.
(1).
The power loss is a non-linear function of bus voltages, which are functions of control variables. The minimization problem is subject to operating constraints [9], which are limits on various control variables (the inequality constraints) and power flow constraints (the equality constraints).
Equality constraints:.
(2) where,.
Vi = voltage magnitude at ith bus.
Gij, Bij = mutual conductance and susceptance between.
bus i and j.
θij = voltage angle difference between bus i and j.
NB-1 = total number of buses excluding slack bus NPQ = set of PQ buses.
Ni = number of buses.
Inequality Constraints:.
In the control variables, the generator bus voltages (AVR operating values) are taken as continuous variable; the transformer tap settings are taken as discrete variable and shunt susceptance values are taken as binary variable. The load bus voltages and reactive power generation Qg are taken as state variables.