Mobile DRT VLF test system

Project focus

  • Modeling, model verification and system analysis
  • Observer and estimator design for the online and offline estimation of the cable capacity
  • Design of a real-time capable control strategy
  • Optimization of system parameters
  • Implementation and test of the control and estimation strategies at a prototype

Description

In recent years, an increased assembly of regenerative energy source, as, e.g., wind farms (on- and off-shore), photovoltaics and biomass, can be observed. These power plants are typically connected to the distribution network by means of high voltage cables (HV, UHV) with voltages up to 500 kV. To test their functionality and to detect failures, suitable test systems for the on-site test of the cables are required.

Due to the high capacity of the considered high voltage cables, a test with grid frequency (50 Hz) would imply very high reactive power. This directly results in large and bulky test systems. To reduce the amount of reactive power and thus the size of the test systems, cables are frequently tested with very low frequencies (VLF, approx. 0,01 Hz to 10 Hz).

Prototype of the VLF test system designed by mohaupt high voltage

In this project, a prototype of a VLF test system designed by mohaupt high voltage was considered, see Fig. 1. Figure 2 depicts the schematic setup of the test system. It comprises a power module, which drives a series resonance circuit. The resulting amplitude modulated high voltage is demodulated by the demodulator to obtain the desired low frequency high voltage test signal.

Sketch of the DRT VLF test system

In this project, a detailed mathematical model was developed which incorporates the main nonlinear behavior, in particular of the demodulator. Based on an analysis of the model, a reduced envelope model was developed, which was the basis for the subsequent observer and controller design. The control strategy was designed to minimize the losses of the system and to maximize the quality of the test voltage (minimize the THD value). The control strategy was extended by an estimation strategy for the unknown load (i.e. the cable). Finally, it was shown how to optimally choose the parameters of the system in order to increase the control accuracy of the system. The feasibility and robustness of the control and estimation strategy was proven by means of experiments on the prototype.

Setup for the tests of the control and estimation strategy

Selected publications

  • S. Eberharter, W. Kemmetmüller, and A. Kugi, Analysis and System Optimization of a Very Low Frequency High-Voltage Test System, in Proceedings of the 7th IFAC Symposium on Mechatronic Systems & 15th Mechatronics Forum International Conference, Loughborough, UK, 2016, p. 294–300.
    [BibTex]
    @InProceedings{Eberharter16a,
    author = {Eberharter, S. and Kemmetm\"uller, W. and Kugi, A.},
    title = {Analysis and System Optimization of a Very Low Frequency High-Voltage Test System},
    booktitle = {Proceedings of the 7th IFAC Symposium on Mechatronic Systems \& 15th Mechatronics Forum International Conference},
    year = {2016},
    volume = {49},
    number = {21},
    month = {9},
    pages = {294--300},
    doi = {10.1016/j.ifacol.2016.10.570},
    address = {Loughborough, UK},
    issn = {2405-8963},
    }
  • W. Kemmetmüller, S. Eberharter, and A. Kugi, Controller design and experimental validation of a very low frequency high-voltage test system, Control Engineering Practice, vol. 37, p. 32–42, 2015.
    [BibTex] [Download]
    @Article{Kemmetmueller15,
    Title = {Controller design and experimental validation of a very low frequency high-voltage test system},
    Author = {Kemmetm\"uller, W. and Eberharter, S. and Kugi, A.},
    Journal = {Control Engineering Practice},
    Pages = {32--42},
    Volume = {37},
    Year = {2015},
    Doi = {10.1016/j.conengprac.2014.12.011},
    }
  • S. Eberharter, W. Kemmetmüller, and A. Kugi, Mathematical Modeling and Analysis of a Very Low Frequency HV Test System, IEEE Transactions on Power Electronics, vol. 29, iss. 11, p. 5784–5794, 2014.
    [BibTex] [Download]
    @Article{Eberharter14,
    Title = {Mathematical Modeling and Analysis of a Very Low Frequency {HV} Test System},
    Author = {Eberharter, S. and Kemmetm\"uller, W. and Kugi, A.},
    Journal = {IEEE Transactions on Power Electronics},
    Pages = {5784--5794},
    Volume = {29},
    Year = {2014},
    Number = {11},
    Doi = {10.1109/TPEL.2014.2299293},
    }
  • W. Kemmetmüller, S. Eberharter, and A. Kugi, Quasi Optimal Feedforward Control of a Very Low Frequency High Voltage Test System, in Proceedings of the 19th IFAC World Congress, Cape Town, South Africa, 2014, p. 11623–11628.
    [BibTex]
    @InProceedings{Kemmetmueller14a,
    author = {Kemmetm\"uller, W. and Eberharter, S. and Kugi, A.},
    title = {Quasi Optimal Feedforward Control of a Very Low Frequency High Voltage Test System},
    booktitle = {Proceedings of the 19th IFAC World Congress},
    year = {2014},
    month = {8},
    pages = {11623--11628},
    doi = {10.3182/20140824-6-ZA-1003.00356},
    address = {Cape Town, South Africa},
    }
  • W. Kemmetmüller and A. Kugi, Mathematische Modellierung und Analyse eines DRT-VLF-Hochspannungsprüfgenerators, e & i Elektrotechnik und Informationstechnik, vol. 129, iss. 1, p. 18–27, 2012.
    [BibTex] [Download]
    @Article{Kemmetmuller12,
    Title = {{Mathematische Modellierung und Analyse eines DRT-VLF-Hochspannungspr\"ufgenerators}},
    Author = {W. Kemmetm\"uller and A. Kugi},
    Journal = {e {\&} i Elektrotechnik und Informationstechnik},
    Pages = {18--27},
    Volume = {129},
    Year = {2012},
    Number = {1},
    Doi = {10.1007/s00502-012-0073-5},
    }

Project partners and funding