Thermal test method for high power three‐phase grid‐connected inverters

Abstract

Semiconductor device junction temperatures are maintained within datasheet specified limits to avoid failure in power converters. Burn-in tests are used to ensure this. In inverters, thermal time constants can be large and burn-in tests are required to be performed over long durations of time. At higher power levels, besides increased production cost, the testing requires sources and loads that can handle high power. In this paper, a novel method to test a high power three-phase grid-connected inverter is proposed. The method eliminates the need for high power sources and loads. Only energy corresponding to the losses is consumed. The test is done by circulating rated current within the three legs of the inverter. All the phase legs being loaded, the method can be used to test the inverter in both cases of a common or independent cooling arrangement for the inverter phase legs. Further, the method can be used with different inverter configurations-three-wire or four-wire and for different PWM techniques. The method has been experimentally validated on a 24kVA inverter for a four-wire configuration that uses sine-triangle PWM and a three-wire configuration that uses conventional space vector PWM. Index Terms grid-connected inverter, high power inverters, inverter testing, LCL filter, thermal test NOMENCLATURE Referring to Fig. 2, v RiO , v YiO , v BiO R, Y and B phase inverter output voltages with respect to dc bus mid-point 'O' i Ri , i Yi , i Bi R, Y and B phase inverter-side inductor currents i R , i Y , i B R, Y and B phase grid-side inductor currents v cm Common mode component of voltages v RiO , v YiO , v BiO i cm Common mode current at the inverter output v RiO,dm , v YiO,dm , v BiO,dm Differential mode component of voltages v RiO , v YiO , v BiO i Ri,dm , i Yi,dm , i Bi,dm Differential mode component of currents i Ri , i Yi , i Bi Superscript 'f u' represents the fundamental component. Superscript 'ri' represents the switching ripple component.

Three phase voltage source inverters with grid connected industrial application

“…The grid angle is used to transform the grid currents and voltages from a-b-c reference frame to d-q reference frame by Park transformation as given in Eqn. (1). The error is calculated from the reference and measured d-q currents, and the errors in dq frame are given to PI regulators.…”

“…This expected to be achieved through establishing grid-connected wind farms and solar Photovoltaic (PV) systems. [1]. Most of renewable energy technology produces a DC power output.…”