Equipment and experimental test setups

Experimental setup

Input impedance measurement

A test set up is available to measure the input and output impedances of switching converters. One example is the input impedance of a grid-connected rectifier whose input impedance was measured in a range from 10 Hz up to 25 kHz. The experimental laboratory setup is shown in Fig. 1a, and the result of the measurements is shown in Fig. 1b. It shows that the impedance of converters can change abruptly at high frequencies, which may cause oscillations between two or more converters connected to each other or to the same grid.


Figure 1a: Measurement set up for converter impedances.


Figure 1b: Input impedance of a boost PFC converter.


Test setup for photovoltaic converters

In order to be able to test commercially available converters for photovoltaic systems, a test system has been developed. By this test setup, the behaviour of the converter towards harmonic pollution, voltage dips can be analysed. Moreover, more common tests are performed, the efficiency of the converter is measured and the maximum power point tracking algorithm is verified. A schematic representation of the test setup is given in Figure 2. The mains is represented by the PAS1000, the photovoltaic panels are represented by the Delta power supplies. Efficiency measurements, harmonic analysis of grid voltage and converter current are obtained by the Voltech power analyser.

Figure 2: Schematic representation of the test setup.


  • A 15 kW three-phase mains simulation system (3x PAS5000 4-quadrant amplifier of Spitzenberger & Spies): this voltage amplifier can create voltages with adjustable amplitude, frequency and waveform. It can be used for the steady-state voltage to be applied on the converter terminals, as well as for small deviations, necessary to measure small-signal impedances.
  • For single-phase applications, there is also a small version of this amplifier: PAS1000.
  • Two 3-kW DC power supplies of Delta Electronics, used in parallel or series connection to represent any renewable energy generator.
  • A network analyser HP-3562A, able to generate frequency sweeps, measure two channels, calculate impedances, amplitudes, phase angles…
  • A power analyser Voltech PM3000A: to measure power, phase angles, total harmonic distortion, harmonics…
  • A scale model of a distribution line used for the experimental verification of harmonic propagation simulations