Apparatus and method for heat-run test on high-power PWM converters with low energy expenditure

Abstract

Before installation, a voltage source converter is usually subjected to heat-run test to verify its thermal design and performance under load. For heat-run test, the converter needs to be operated at rated voltage and rated current for a substantial length of time. Hence, such tests consume huge amount of energy in case of high-power converters. Also, the capacities of the source and loads available in the research and development (R&D) centre or the production facility could be inadequate to conduct such tests. This paper proposes a method to conduct heat-run tests on highpower, pulse width modulated (PWM) converters with low energy consumption. The experimental setup consists of the converter under test and another converter (of similar or higher rating), both connected in parallel on the ac side and open on the dc side. Vector-control or synchronous reference frame control is employed to control the converters such that one draws certain amount of reactive power and the other supplies the same; only the system losses are drawn from the mains. The performance of the controller is validated through simulation and experiments. Experimental results, pertaining to heat-run tests on a high-power PWM converter, are presented at power levels of 25 kVA to 150 kVA.

Minimum switching loss pulse width modulation for reduced power conversion loss in reactive power compensators

“…However, under practical conditions, this current corresponds to the losses in the two converters. Required amount of reactive power can be circulated www.ietdl.org between the two converters, in the above fashion, with only losses being supplied from the mains [19,20]. In this work, the two converters are controlled in synchronously revolving reference frame, with each converter having an outer voltage loop and two inner current loops [19,20].…”

“…To actually operate the converter at zpf at this power level, two identical PWM converters are connected in parallel to the grid and are operated under reactive‐power circulation mode, with only the converter losses being drawn from the mains [19, 20]. This arrangement enables testing of the converters at power levels, which exceed the rating of the distribution transformer, feeding the experimental setup.…”

“…MSLPWM at zpf Variation of normalised per-phase switching loss for CSVPWM and MSLPWM over a fundamental cycle (pf angle = 90°lag or lead) Schematic diagram of reactive-power circulation test setup[19,20] …”

“…Experimental results at 150 kVA reactive-power circulation a Grid voltage and converter currents with CSVPWM b Results with MSLPWM (v RN : 240 V/div., i R1 , i R2 : 250 A/div., v R2O2 : 500 V/div., x-axis: 5 ms/div.) Phasor diagram of converters operating under zpf lag and lead conditions[19,20] …”

Common-Mode Injection PWM for Parallel Converters

“…The difference in converter terminal voltages is more pronounced under power circulation than power sharing [1]. Such circulating-power mode is useful for conducting heat-run tests Manuscript on high-power converters [1], [21], [22]. While the work in [1] utilizes carrier-interleaving methods for reducing the gridcurrent distortion in parallel converters with unequal terminal voltages, the work in [12] deals with the control of parallelconnected boost rectifiers under unequal load sharing.…”