The10kV5Mvar Cascade STATCOM Device Research And Development

With the kind of electricity load increases, the use of some large inductiveor capacitive load, not only to the grid voltage fluctuations, but also affect thequality of power supply, the reactive power is also a great deal of losses to thepower system and electricity sector. Therefore，how to improve the quality ofpower supply from grid, make the power system operat safely and stabley, is theresearch background of this paper.Static Synchronous Compensator (STATCOM) is a devices which can issueor absorb reactive power with integrate power electronics converter technologyand power semiconductor. In this paper, we use the voltage-bridge invertercircuit as a single inverter unit, Constitute a large-capacity main circuit throughcascade all the single inverter unit,and connect to the system side by connectingreactor system side. To the cascade structure STATCOM,we use carrier phasemodulation technology, superimposed and output approximately sinusoidalvoltage that amplitude and phase can adjust.To the reactive current control, this article uses the direct current controlmethod that track the output current of the device dynamically, so that the outputreactive current can changes with instructions current. This method with respectto the indirect current control, higher requirements on the switching frequency ofthe switching device, but the control method is relatively simple and easy to beimplemented in software.Cascade STATCOM has a common problem,that is the imbalance of dc sidecapacitor voltage, we propose a balanced control method, we can calculatecharging current by compare the size of the set and actual values of the DCcapacitor voltage, make the DC side voltage of each module consist.We introduced Cascade STATCOM device controller hardware design,including the master controller, three-phase sub-controller, power module controller. And descripte the design principle of the power module controllerdetailed, intruduce part of the schematic design. Finally,we did experiments forthe entire device, reactive current output better.