Introduction

The previous chapter introduced some important concepts in the tuning of PSSs in multi-machine power systems. The purpose of this chapter is to demonstrate the application of the associated techniques for the analysis and tuning of PSSs in a fourteen-generator power system which, without continuously acting PSSs, is inherently unstable. Each ‘generator’ in this system, in fact, represents a power station which accommodates between one and twelve units; the number of units in-service (nu) depends on the particular operating condition. The units in a power station are assumed to be identical, therefore the rating of the equivalent generator for a station is nu times the rating of a single unit. It is assumed that the individual generators in each power station are fitted with identical excitation systems and PSSs.

In a later chapter a class of stabilizers known as Power Oscillation Dampers (PODs) are discussed; these are stabilizers that can be fitted to power-electronic based transmission devices such as FACTS (e.g. Static Var Compensators) and HVDC transmission. The analysis and tuning of POD stabilizers are demonstrated by means of examples in Chapter 11. In the fourteen-generator power system described in this chapter the Static Var Compensators (SVCs) are fitted with continuously acting voltage regulators controlling bus voltage, but are not fitted with stabilizers.

The steps in the tuning of PSSs of machines in a multi-machine system are explored, commencing with (i) the eigen-analysis of the system with all PSSs out of service, and (ii) the associated analysis based on Mode Shapes and Participation Factors. The PSSs are then tuned using the P-Vr approach discussed in Section 9.4. Having completed the determination of the PSS parameters, the effect on the shifts of eigenvalues associated with the rotor modes are assessed as the damping gains of the PSSs are increased; ideally over the range of operating conditions such shifts are directly to the left in the complex s-plane.

In practice a new power station is built to supply energy to an existing power system in which many of the existing generators may already be fitted with PSSs. The latter PSSs would have been tuned and their parameters set to fixed values. The PSSs in a new power station have to be tuned to satisfy the damping and other performance criteria of the system operators over the range of system operating conditions and contingencies.