Saturation effects in transformers and shunt reactors can produce harmonics in power systems. Their magnitude can sometimes be found with an electromagnetic transients program, by going from an approximate linear ac steady-state solution directly into a transient simulation in which the nonlinear effects are included. In lightly damped systems, such simulations can take a long time, however, before the distorted steady state is reached. Therefore, another method was developed which uses superposition of steady-state phasor solutions at the fundamental frequency and at the most important harmonic frequencies, with nonlinear inductances represented as harmonic current sources. This method can either be used by itself, or as an improved initialization procedure for electromagnetic transients programs.

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The Voltage-Power (V-P) relationship at the Point of Common Connection (PCC) of Distributed Generators (DG) identifies the overvoltage condition due to DG connections. However, overvoltages are not the only consideration. In the connection of DG in distribution and subtransmission feeders voltage fluctuation and instability are also important issues. This paper provides a systematic analysis of the voltage regulation issue, presents a practical and conservative approach to maximize the DG capacity of a Transformer Station (TS) and to minimize voltage fluctuation while keeping the feeder voltage within an acceptable range, with minimum modification to existing voltage regulating facilities. The approach not only takes into account voltage performance at the PCCs, but also at the TS bus, therefore the entire TS.

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