A modular three-phase voltage regulator with fictitious dc-link

A modular three-phase voltage regulator with a fictitious dc-link is proposed. The proposed scheme is the combination of three single-phase modules while each one of the single-phase module is a three-leg ac voltage regulator. Therefore, the proposed voltage regulator reduces the number of main switches and compensates the voltage of each phase independently. Furthermore, a small film ac capacitor is used to replace the electrolytic capacitor, which not only reduce the size of the dc link capacitor and the stress of the switches but also increase the lifetime of the voltage regulator. The proposed scheme can compensate the voltage disturbance such as under-voltage, over-voltage, voltage sag, voltage swell, three-phase voltage unbalance and three-phase load unbalance effectively. Besides, there are several advantages of this structure, for instance: simple system-configuration, rapid voltage-compensation, easy setup-maintenance and decreasing the production cost while increasing the system power density. Eventually, some experimental results are provided to illustrate the steady-state characteristics and transient responses of the proposed modular three-phase voltage regulator.