Power Flow Optimization

Abstract

In the basic load flow problem, the so-called control variables are specified, permitting the feasibility of solution. We recall that the control variables consist of real power generation at all generation busses except the slack bus, and voltage magnitudes at all generation busses. The specification of these control variables is not arbitrary. It is based on several considerations. The first major consideration is that of satisfying all power demands within the acceptable tolerances for voltage levels, without violating the limits on generation levels, transmitted currents, and powers. (These demands and limits are normally referred to as the equality and inequality constraints, respectively.) There are usually wide ranges of control variable values for which all of these constraints are satisfied. As a result, one selects those control variable values which will minimize (or maximize) a desired performance index. One possible performance index can be the total losses in the transmission network. Another one can be the cost of generation needed to meet the demand. Yet a third performance index may reflect a combination of operating cost, security considerations, and possibly pollution levels.