Mathematical Modeling and Analysis of a Very Low Frequency HV Test System

Controller design and experimental validation of a very low frequency high-voltage test system

“…In the simplest demodulation strategy, all thyristors of the positive branch are switched on for the positive half-wave and all thyristors of the negative branch for the negative half-wave of the desired output voltage u l . As already discussed in Eberharter et al (2014), this demodulation strategy leads to a significant deviation in u l from the desired sinusoidal output voltage, especially for large values of C l . Fig.…”

“…Afterwards, a simplified mathematical model and an envelope model are derived. For a more detailed system description and modeling of the DRT system, the reader is referred to Eberharter et al (2014).…”

“…In parallel to this arrangement, a discharging resistor R d;i and a capacity C dm;i , which is required to guarantee a homogeneous voltage distribution across the modules , are placed. The energy required for the switching of the thyristors is extracted from the high carrier frequency voltage across each SVU module, see Eberharter et al (2014). Fig.…”

“…3 shows an equivalent circuit diagram of the DRT system presented in Section 2.1. For the development of the mathematical model, the following assumptions and simplifications are made, see also Eberharter et al (2014) and Kemmetmüller et al (2014): the overall demodulator can be approximated by a continuously adjustable resistor R dm ðtÞ and a parallel capacitance C dm , neglecting the modular design of the demodulator. The value of C dm is defined by a capacitance network comprising the parallel capacitances C dm;i of the N SVU modules and the stray capacitances between the modules and the housing of the DRT system.…”

“…To extend the range of VLF test systems to higher voltage levels, a VLF test system based on the so-called differential resonance technology (DRT) was developed. This type of VLF system allows a mobile VLF testing of cables up to 500 kV rms and higher, see Eberharter, Kemmetmüller, and Kugi (2014) and Mohaupt and Bergmann (2010).…”