Dynamics and Control of Electric Transmission and Microgrids

3Modeling and Simulation of Synchronous Generator Dynamics

3.1 Introduction

Synchronous generators are extensively used in power stations, supplying bulk electric power over high‐voltage (HV) or extra‐high‐voltage (EHV) transmission lines to load centres. Generally AC transmission is used, however, in some cases (particularly from remote hydropower stations), the generators may be transmitting power over bipolar HVDC lines. The nominal voltage (phase to phase) of generators is limited below 40 kV and a step‐up generator transformer is used to increase the voltage to the transmission level. The generator may be driven by steam, hydro or gas turbines. In microgrids at lower power levels, the generators may be driven by diesel engines. The fuel used may be coal or gas in thermal stations whereas natural or enriched uranium is used in nuclear power plants. In hydro stations, the kinetic energy of water drives the hydro turbines.

In the early stages of power development, the only dynamic components in power systems were synchronous generators. The prime mover control was used to regulate speed (frequency) and power output. The fast‐acting static excitation with high gain electronic voltage regulators were developed in the 1960s. For stability analysis, simple models based on the swing equation (3.1) were used. The swing equation describes the variation of rotors frequency as [1–5]:

(3.1)

where and are mechanical torque and power acting on the rotor, and and are electrical torque ...