Abstract:
Regenerative AC-AC converters are required for
serving AC loads that draw and return power during operation,
when input is also taken from an AC source. AC motor drives,
static VAR compensators, harmonic compensators and inverter
testbeds are some of the examples using regenerative AC-AC
converters. Generally, these are implemented as 2-level converters
and operated with Pulse Width Modulated (PWM) control,
incorporating higher switching frequencies. The use of higher
switching frequencies leads to correspondingly higher switching
losses and EMI issues. This paper describes the development
of a 5-level regenerative AC-AC converter that can deliver
equally good performance but operating at very low switching
frequencies. It was developed as part of a testbed for performance
testing of grid-tie solar PV inverters. The output specifications
were accordingly drawn to comply with the requirements of
IEEE1547. Input specifications were chosen to produce sinusoidal
current and inphase with input voltage all the times. The
converter employed back-to-back connected 5-level neutral point
clamped (NPC) structure with middle DC-link. The input stage is
operated with current control and the output stage with voltage
control. DC-link capacitors were equipped with separate voltagebalancing
circuits so that the voltage across each capacitor
could be regulated at the nominal value all the times. The
details of design, operation, control and simulation with operating
waveforms are presented in the paper.
Citation:
Karunadasa, J.P., Bandara, I.B.H., Dayananda, W.D.D., Kumara, K.G.S.U., & Tennakoon, G.M.R. (2018). High performance AC-AC regenerative 5-level NPC converter with capacitor voltage balancing. In R. Samarasinghe & S. Abeygunawardana (Eds.), Proceedings of 2nd International Conference on Electrical Engineering 2018 (pp. 1-7). Institute of Electrical and Electronics Engineers, Inc. https://ieeexplore.ieee.org/xpl/conhome/8528200/proceeding