Power quality improvement of small hydro station

Abstract

Paper presents generation system dedicated to small hydro power station. The conventional generation system uses cage induction generator which demand of reactive power is very high and then its power quality in transients and steady state is very poor. To improve the quality of power, a three level NPC power electronic parallel compensator is applied. The generation system reactive current and power is controlled using voltage oriented method. The rotating x-y frame responds space vector of the grid voltage. To prove such system a laboratory 7.5 kW generation stand was built and tested. The NPC three level converter operation was tested in transient condition during turn-on the generator to grid. As result of compensator operation the peak current was reduced. In steady state the compensator produces reactive power demanded by the generator and then the generation system reactive power demand is null.

Asynchronous Grid Connection of a Cage Induction Generator Excited by a Power Electronic Converter

“…For these conditions component u Mx equals U M and u My equals zero [10], [11]. The output signal of the DC-bus voltage regulator Ru DC establishes the reference signal i * P x , and i * P y is referenced from stator voltage controller Ru M or reactive power controller Rq G depending on the operation mode.…”

“…However, in both systems the induction generator demand on the reactive power is covered by the grid, so the capacitor bank is used to partially compensate for reactive power demand [8], [9]. As the reactive power of the induction machine depends on its active power, the parallel-connected electronic converter might precisely satisfy variable profile reactive power demand [9]- [11]. Connection of an excited induction generator to the grid without an inrush current, i.e., with synchronization, is possible, but the source of mechanical power should be equipped with a precise speed controller [12].…”

Analysis of squirrel-cage induction generator start-up supported by reactive power compensator

“…A reactive power compensation is usually provided by capacitor bank, but that solution does not allow to precise reduce the reactive power delivered from the grid (Sharaf et al, 2010). A capacitor bank may be replaced by the STATCOM, which delivers a reactive power precisely as much as the induction generator needs (Aparna et al, 2017;Swagat et al, 2018;Wi sniewski et al, 2012;Wi sniewski and Koczara, 2013), as it is shown in Figure 1. The parallel electronic compensator is a compromise between simplicity and robustness of capacitor banks compensator and cost and controllability of back-to-back converter interface (Meier et al, 2014).…”

Reduced converter topology for integrated wind and small‐hydro energy generation system

“…This increases the losses and needs the de-rating of the machine. These power quality issues can be mitigated to increase the system efficiency as discussed in [16,17]. Authors have worked on a hybrid system control and operation.…”