Optimal Tuning of PID Controllers for Generation Control of HVDC Link Interconnected Power System

Interconnections of power systems enable taking advantage of diversity of loads, availability of sources and fuel price in order to supply electricity to the loads at minimum cost with a required reliability. But with interconnections, the power system becomes increasingly complex to operate and the system can become less secure for riding through the major outages. System frequency and system voltage profile matching is the main concern in an interconnected power system. With interconnections, variations in system frequency and voltage increase which may lead to large dynamic swings between different parts of the system. In this paper, the Automatic Generation Control of two interconnected control area power system, with parallel HVDC links for each control area, is modeled as a closed loop control system problem. A step input signal is applied to the closed loop control system to correlate the changes in system load during operation of the power system. The variations in system frequency and voltage are reduced with Proportional Integral Derivative (PID) controllers. These controllers are very widely used for closed loop control systems; however, the tuning of these controllers is difficult. With proper selection of PID controller gains, the dynamic performance of the system is improved and with HVDC links for interconnection, the system stability and tie line deviations are maintained.