Neutral-Point Voltage Balancing for Mission Profile Emulator of Three-Level T-type PV Inverter Using Extra Bridge

Mission profile emulation (MPE) is a promising method that uses converters to emulate grid characteristics in laboratory tests of Three-Level T-type PV inverters (3LT
²
I). The shared DC-link between emulator and 3LT
²
I realizes energy recycling, but introduces an extra zero-sequence loop. This loop deactivates conventional 3LT
²
I neutral-point balancing methods that generate common-mode voltage, bringing excessive current burden to common-mode choke. Therefore, a neutral-point voltage balancing method using an extra converter leg is proposed in this paper, which is implemented by controlling the DC-link as an LC-filtered converter. In this scheme, the pressure of common-mode choke can be relieved, and the behaviors of the extra bridge is fully decoupled from 3LT
²
I under test, ensuring isolation and accuracy of testing during emulation. Simulation and results further confirm the feasibility and effectiveness of proposed method.