Micro-hydro power plants (μHPPs) are a major energy source in grid-isolated zones because they do not require reservoirs and dams to be built. μHPPs operate in a standalone mode, but a continuously varying load generates voltage unbalances and frequency fluctuations which can cause long-term damage to plant components. One method of frequency regulation is the use of alternating current-alternating current (AC-AC) converters as an electronic load controller (ELC). The disadvantage of AC-AC converters is reactive power consumption with the associated decrease in both the power factor and the capacity of the alternator to deliver current. To avoid this disadvantage, we proposed two rectifier topologies combined with symmetrical switching. However, the performance of the frequency regulation loop with each topology remains unknown. Therefore, the objective of this work was to evaluate the performance of the frequency regulation loop when each topology, with a symmetrical switching form, was inserted. A MATLAB® model was implemented to simulate the frequency loop. The results from a μHPP case study in a small Cuban rural community called ‘Los Gallegos’ showed that the performance of the frequency regulation loop using the proposed topologies satisfied the standard frequency regulation and increased both the power factor and current delivery capabilities of the alternator.
En el presente trabajo se analiza un rectificador trifásico de tipo puente con el interruptor en serie con la carga conmutada con el ángulo simétrico, asistido con los índices de corriente efectiva, potencia activa, potencia reactiva, Potencia aparente, de distorsión y el factor de potencia. El objetivo es aplicar este rectificador conmutado con ángulo simétrico para mejorar el factor de potencia en microcentrales hidroeléc- tricas que operan en régimen aislado, y que regulan la frecuencia variando la potencia disipada en las cargas de lastre con corriente alterna con la alternancia de convertidores de corriente. Se suman las expresiones de los índices anteriores de la corriente alterna con la alternancia del convertidor de corriente. Un ejemplo, se calcula donde ambos convertidores se comparan demostrando la ventaja del circuito rectificador con respecto al factor de potencia del sistema eléctrico.
Palabras clave: conmutación simétrica; convertidor CA-CA; control de frecuencia; factor de potencia; rectificador
AbSTRACT
In the present work is analyzed a type bridge three-phase rectifier with switch in series with the load commuted with symmetrical angle, as- sisting to the indexes effective current, power active, reactive, apparent, of distortion and power factor. The objective is to apply this rectifier commuted with symmetrical angle for the improvement of the power factor in hydroelectric micro centrals that operate in isolated regime, and that they regulate frequency varying the power dissipated in loads ballasts with alternating current in alternating current converters. The expressions of the indexes previous of the alternating current in alternating current converter are summarized. An example is calculated where both converters are compared demonstrating the advantage of the circuit with rectifier regarding the factor of power of the electric system.
Keywords: Rectifier; symmetrical switching; CA-CA converter; power factor; frequency control
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