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This paper examines the application of a diodeclamped multilevel inverter (DCMLI)-based distribution static compensator (DSTATCOM) connected to a three-phase, four-wire (3p4w) distribution system. The DCMLI has an inherent unbalancing problem among its dc capacitor voltages. Additionally, when the load contains a dc part, the neutral point of the compensator also becomes unbalanced. In this paper, the effects of different loading conditions on the dc capacitor voltages of the inverter are studied. Two new control circuits are proposed for equalizing the capacitor voltages. Different control techniques are presented for the equalizing circuits. Equations of the proposed equalizing controllers are developed corresponding to the control of the switching devices. Comparative studies of different control techniques and the performances of the two controllers are performed. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the proposed equalizing controller circuits. Index Terms--Capacitor voltage equalization, dc-dc converter control, diode-clamped multilevel inverter (DCMLI), distribution static compensator (DSTATCOM), equalizing circuit.

In this paper, load compensation using multilevel inverter-based distribution static compensator (DSTATCOM) is presented. The DSTATCOM is connected to a three-phase four-wire (3p4w) distribution system. Two different multilevel inverter topologies are used to realize the DSTATCOM. They are diode-clamped multilevel inverter (DCMLI) and flying capacitor multilevel inverter (FCMLI). A compensating technique has been derived, which uses the state feedback control to the multilevel inverters-based DSTATCOMs. A switching strategy for the multilevel inverters that ensures utilization of all output voltage states of the inverter for efficient tracking of references has been proposed. The schemes of dc-link capacitor voltage control for DCMLI and flying capacitor voltage control for FCMLI have been discussed. Comparative studies of performances of the two DSTATCOM topologies are performed. The simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the proposed control scheme. Index Terms--Diode-clamped multilevel inverter (DCMLI), distribution static compensator (DSTATCOM), flying capacitor multilevel inverter (FCMLI), switching control.

Flying capacitor multilevel inverter (FCMLI) is a multiple voltage level inverter topology intended for high voltage and power operations with low distortion. It uses capacitors, called flying capacitors for clamping the voltage across the power semiconductor devices. In this paper, the implementation of a distribution static compensator (DSTATCOM) using an FCMLI is presented. A hysteresis current control technique for controlling the injected current by the FCMLI-based DSTATCOM is discussed. A new method for controlling the flying capacitor voltages is proposed which ensures that their voltages remain constant and at the same time maintain the desired current profile under the hysteresis current control operation. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the control scheme and the FCMLI-based DSTATCOM. Index Terms--Distribution static compensator (DSTATCOM), flying capacitor multilevel inverter (FCMLI), hysteresis, voltage-source converter (VSC).

The flying capacitor multilevel inverter (FCMLI) is a multiple voltage level inverter topology intended for high-power and high-voltage operations at low distortion. It uses capacitors, called flying capacitors, to clamp the voltage across the power semiconductor devices. A method for controlling the FCMLI is proposed which ensures that the flying capacitor voltages remain nearly constant using the preferential charging and discharging of these capacitors. A static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC) based on five-level flying capacitor inverters are proposed. Control schemes for both the FACTS controllers are developed and verified in terms of voltage control, power flow control, and power oscillation damping when installed in a single-machine infinite bus (SMIB) system. Simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the control scheme and the FCMLI-based flexible alternating current transmission system (FACTS) controllers. Index Terms--FCMLI, multilevel inverter, power oscillation damping, SMIB, SSSC, STATCOM.