The following relates to the voltage regulation arts, power system arts, and related arts.
Conventional electrical power grids in the United States, Europe, and many other countries is maintained as a constant voltage system, in which electrical outlets in a home or business are expected to have a certain voltage. For example, in the United States the expected voltage is usually 110 Vrms (typical in residential house electricity) or 220 Vrms (typical in commercial and some residential environs). In most of Europe the expected voltage is 220 Vrms. (Hereinafter, when not indicated voltages are root-mean-square, i.e. rms, values). In a per-unit nomenclature, the expected voltage is suitably designated 1.00 pu.
In practice, the voltage may deviate from the expected 1.00 pu value, typically due to a mismatch between power generation and demand. For a given power generation level, when the demand is lower than expected the voltage increases, leading to an overvoltage condition. When the demand is higher than expected the voltage decreases, leading to an undervoltage condition. Some such variation is tolerable, and loads typically have power supplies or power regulation circuitry to compensate for some input voltage deviation. However, if the overvoltage or undervoltage condition becomes too severe it can have adverse effects such as degrading load operational efficiency, causing loads to fail due to the supply voltage falling out of operational range, tripping a safety interlock, or so forth. At the grid level, voltage is typically managed from the generation side by adding or reducing generation capacity to maintain grid voltage, although various demand side load (DSL) management approaches are also known.
Voltage fluctuations can also occur at the distribution level, for example due to additional loads coming online or taken offline so as to significantly change the total load being served by an individual feeder circuit. These distribution-level fluctuations are more difficult to correct.