This paper presents the simulation studies on a Cascaded H-Bridge converter based Distribution Static Synchronous Compensator (DSTATCOM) for improving the power quality of a distribution system. Voltage source converter based DSTATCOM has been established as the most preferred solution for management of reactive power in distribution utilities and for improving voltage regulation, power factor and power quality in industries. For high power applications, cascaded H-Bridge converter is the most ideal choice compared to two-level inverter with series connected power devices. In the present work DSTATCOM controller is designed using DQO modelling for reactive power management and thereby improving the power factor in distribution systems. The dc link voltage and the three phase load currents are used as feedback signals for the controller and it is designed in such a way that DSTATCOM is able to supply the reactive current demanded by the load both during steady state and transient conditions using sinusoidal pulse width modulation control.
1. Cascaded H-Bridge Converter
3. Reactive power compensation
4. Sinusoidal PWM
SIMULINK BLOCK DIAGRAM:
Fig. 1. The cascade H-bridge converter based DSTATCOM.
EXPECTED SIMULATION RESULTS
Fig. 2. The phase voltage (top trace ) and line-to-line voltages of H-bridge
Fig. 3. Source phase voltage (top trace) and source phase Current (bottom
trace) with DSTATCOM in closed loop power factor control mode.
Fig. 4. DC link voltage (Vd,) (Top or First Trace), direct and quadrature axis
source currents (Second Trace) ,inverter currents Id and Iq (Third Trace) and
load reactive current (Bottom Trace).
Fig 5. Individual Capacitor voltages of three level Cascaded H-Bridge
The paper presents the principle of operation of cascaded H-bridge converter and simulation studies on cascaded converter based DSTATCOM using Sinusoidal PWM control. It is observed that the DSTATCOM is capable of supplying the reactive power demanded by the load both during steady state and transient operating conditions. The harmonics in cascaded H-bridge three-level inverter current are less compared to two-level inverter operating at same switching frequency.
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