Multi-Level Three-Phase Current Source Inverter based Series Voltage Compensator

This work presents a three-phase series voltage compensator based on a three-level current source inverter. The topology obtains all the benefits of voltage source based multi-level topologies such as reduced harmonic distortion in voltage and current waveforms as well as a proper sharing of the load power among the power valves. Contrary to voltage source based topologies, the proposed configuration requires just a first order filter which in turn reduces the generation of resonances in the distribution system. It is shown that the dc link voltage balancing issue found in multi-level voltage source topologies is also found in the proposed one; however, in this case, the issue is the balancing of the dc link currents. It is found and presented a simple closed control loop that can keep the dc link currents perfectly balanced. This loop operates independently of the loop used to control the series voltage injection thus allowing their decoupled operation. The preliminary results show very low distorted injected voltage. As expected, any modulating technique can be used to gate the arrange of power valves; in this document, a carrier based PWM technique is used to illustrate the gating signal generation method. The document presents the power topology, the model in the stationary abc frame, a simple carrier based modulating technique that allows the dc link current balancing, and a steady state analysis and comparison.