EMTP simulations and experimental verification of an all-active hybrid converter arrangement for filtering power system harmonics and STATCOM

Active filters and advanced static VAr compensators (STATCOM) are hampered in their application at medium voltage levels (e.g. 13.8 kV) due to the need for a line-frequency interface transformer. A novel per-phase approach eliminates the need for a line-frequency transformer by series connection of slow-switching converters and a fast-switching PWM converter. The slow-switching converters operate in voltage-mode to counteract the utility voltage while the PWM converter operates in a current-control mode to control the injected current. Experimental results of a DSP-based laboratory prototype operating in steady state are presented to establish the concept validity. EMTP simulations address many practical aspects of this scheme-operation under steady stare conditions; transients such as startup, faults, sudden over- and under-voltages; and DC bus voltage regulation. The simulation results demonstrate the technical feasibility of this approach for implementing it in utility systems