Spectral Grid Impedance Identification on the Low-, Medium- and High-Voltage Level – System Design, Realization and Measurement Results of Grid Impedance Measurement

Abstract

The frequency dependent grid impedance at the terminals of an electrical supply grid is an essential parameter for power quality and grid feedback analysis. In this contribution the identification of the grid impedance is achieved using spectral excitation currents at the corresponding grid connection point, which generate measureable changes in the grid voltage spectra. Different measurement systems based on this method have been successfully realized for the low-and medium-voltage level. A measurement system for the high-voltage level is currently being realized. The application of the measurement systems are facing quite different external framework conditions leading to specific system designs for each measurement device. The spectral grid impedance identification on these voltage levels is done through fast switching of an ohmic load with power electronic. The requirements and setup of the grid impedance measurement systems are outlined and measurement results on the low-and medium-voltage level are presented and discussed. The systems can be used to evaluate grid connection points and to verify other active or passive grid impedance identification methods on different voltage levels.

Test methodology for validation of multi‐frequency models of renewable energy generators using small‐signal perturbations

“…As another option, the Thevenin impedance can be calculated using current perturbation tests via an additional shunt current source device in the test bench [18][19][20][21][22][23][24][25]. The impedance calculation procedure for current perturbation tests is given in the Appendix A of this paper.…”

“…[16] introduces a validation approach based on analysing power quality measurements and providing validation margins for each harmonic. In [17][18][19][20][21][22][23][24][25], impedance measurement test topologies have been proposed using small-signal perturbations via converter-based devices. A perturbation can be either a voltage source in series or a current source parallel with the AC grid [18][19][20][21][22][23], as illustrated in Figure 1.…”

“…In [18][19][20][21][22][23][24], the experimental implementation of current perturbation (I pert ( f h )) using an additional shunt device is explained and demonstrated, as shown in Figure 1(a). Accordingly, the series-connected impedance (Z cl ) is used to divert the perturbation current flow towards the DUT [22].…”

“…Accordingly, the series‐connected impedance () is used to divert the perturbation current flow towards the DUT [22]. The design aspects of a test device for the realisation of current perturbations in low voltage (LV), medium voltage (MV), and high voltage (HV) levels are explained in [23]. Besides, series voltage perturbation () is another method for impedance measurement test, as illustrated in Figure 1(b).…”

Impact of Lossy Compression Techniques on the Impedance Determination

“…The device includes highly accurate sensors for the measurement of voltage and current wave forms. Figure 2 shows a simplified scheme of the measurement setup to evaluate the impedance of the three-phase mid voltage PCC [10,11]. A resistive load is switched by an insulated gate bipolar transistor (IGBT), while the measurement loop (e.g., L1-L2) is selected by a B6 thyristor bridge.…”