Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module
Thesis (PhD)--Stellenbosch University, 2024.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2024
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867614015341985792 |
|---|---|
| access_status_str | Open Access |
| author | Coetzer, Kurt |
| author2 | Rix, Arnold Johan |
| author_browse | Coetzer, Kurt Rix, Arnold Johan |
| author_facet | Rix, Arnold Johan Coetzer, Kurt |
| author_sort | Coetzer, Kurt |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/130345 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:45:19.124Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/130345 Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module Coetzer, Kurt Rix, Arnold Johan Wiid, P. G. Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. Electromagnetic interference Photovoltaic cells Electric circuits, Nonlinear UCTD Thesis (PhD)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Electromagnetic interference (EMI) can couple into photovoltaic (PV) installations – inducing currents and voltages which, if large enough in amplitude, can cause damage. Modelling this coupling is not straightforward. The behaviour of a PV module is particularly challenging to emulate as the nonlinear operation of the PV cells and bypass diodes needs to be considered, as well as the coupling and radiation characteristics of the module. Little research has been performed on the response of PV modules to EMI. A small subset of this work is validated through measurement, and an even smaller subset involves modelling. Where modelling is documented in the literature, it is generally done using a wire-based representation of each PV module. These wire-based equivalent models are seen in any of the following three contexts: analytical voltage derivations which result from the application of Faraday’s Law to the loop area formed by the wires; high-voltage laboratory experiments; or computational electromagnetic (CEM) simulations. These three contexts all have their limitations and when a wire-based formulation is used in any of these contexts in the literature, it is never fully validated – it is simply assumed to be correct. Using a series of careful measurements, this dissertation assesses the validity of wire-based equivalent models applied in this context. The impedance, internal string-to-string coupling, and radiation characteristics of two real PV modules are assessed in the frequency domain using a vector network analyser (VNA). A large and a small PV module were chosen to investigate the influence of electrical s ize and l ayout. The r esults are compared to CEM implementations of wire-based equivalent models. These comparisons produced error margins which exceeded 600% in some contexts. Furthermore, most wire-based equivalent model implementations make no attempt to model linearised PV cell or bypass diode behaviour in small-signal scenarios, let alone their nonlinear behaviour in large-signal applications. Thus, wire-based equivalent models are shown to be unsuitable for EMI-related PV research at any frequency below 50 MHz. Given that the shortcomings of the approach generally used in the literature have now, for the first time, been demonstrated, the question remains – how should the response of a PV module to EMI be modelled? AFRIKAANSE OPSOMMING: This dissertation answers this question by proposing a novel, measurement-validated methodology, which works in two stages. Firstly, it simulates the coupling and radiation characteristics using advanced original three-dimensional (3D) representations, which are assessed to at least 50MHz using a CEM solver. Then, the results of the CEM solver are linked to a nonlinear circuit representation which independently considers the operation of each PV cell and bypass diode within the module. This combination of linked CEM and circuit representations produces a circuit-CEM hybrid methodology. Implementing the proposed circuit-CEM hybrid methodology requires multiple inputs. The first input investigated was the circuit representation of a bypass diode. No detailed models of the class of Schottky diode commonly used in bypass diode applications were found in the literature, let alone one suitable for high-frequency applications. Multiple bypass diodes were assessed using direct current (DC), unbiased small-signal alternating current (AC), and DCbiased small-signal AC measurements. The results of these measurements were used to produce a novel high-frequency bypass diode circuit model, which is presented along with the relevant parameters. The developed model is able to consider any combination of DC, small-signal AC, and large-signal transient behaviour, and exhibits improved reverse-bias performance over other standard Schottky diode circuit models. The second input to the circuit-CEM methodology is a PV cell model. The procedure applied when assessing the bypass diodes was adapted to investigate the circuit behaviour of the PV cells within the large and the small PV module. This resulted in the development of another novel circuit representation, which was also suitable for any combination of DC, small-signal AC, and large-signal transient behaviour, and again exhibited improved reverse-bias accuracy. The third, and final, input required by the circuit-CEM hybrid methodology is a 3D representation of a PV module. As wire-based equivalent models had already been demonstrated to be unsuitable, four original 3D structures – termed the Level 1-4 models – are proposed. Each subsequent level builds on the complexity of the previous level. All of these structures incorporate much higher levels of detail than a wire-based model and individually represent each cell and bypass diode within the PV module at locations which correspond with their actual locations in a real PV module. In small-signal contexts, linearised versions of the fully integrated circuit-CEM hybrid models demonstrate much higher levels of accuracy when compared to the wire-based models found in the literature. Improvements by up to a factor of 400 are noted when the resulting circuit- CEM hybrid model is assessed from the impedance perspective. In the internal string-tostring coupling scenario, the acclaimed Feature Selective Validation (FSV) method objectively determined that the Level 1-4 novel circuit-CEM hybrid models produced results which were generally classified as “Good” to “Excellent”. By comparison, the results produced by wirebased equivalent representations were graded as either “Poor” or “Very Poor”. For large-signal scenarios, the importance of incorporating each aspect of the proposed circuit-CEM hybrid models is demonstrated by simulating the response of the model to a nearby lightning current. Wire-based equivalent models were shown to overestimate induced voltages and currents. Combining improved 3D structures with linearised PV cell circuit models produces equal and opposite-polarity voltage and current results when the polarity of the lightning waveform is reversed – a clear flaw when attempting to model the large-signal behaviour of a nonlinear system. Utilising both improved 3D structures and nonlinear PV cell circuit models addresses this shortcoming so long as the real PV module being modelled does not contain bypass diodes. Should bypass diodes be present in the real PV module, then they must be represented in a nonlinear manner in simulations. The proposed circuit-CEM hybrid methodology, along with its measurement-derived parameters, novel 3D structures, and original circuit models, allows for the nonlinear EM-related behaviour of a PV module to be modelled in a manner which is both easily spatially reconfigurable and produces results at unprecedented levels of accuracy – when compared with the performance of the unvalidated wire-based equivalent models found in the literature, this is a “quantum leap” in EMI-related PV research. Doctorate 2024-02-29T07:25:36Z 2024-04-26T14:13:48Z 2024-02-29T07:25:36Z 2024-04-26T14:13:48Z 2024-03 Thesis https://scholar.sun.ac.za/handle/10019.1/130345 en_ZA en_ZA Stellenbosch University xx, 209 : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Electromagnetic interference Photovoltaic cells Electric circuits, Nonlinear UCTD Coetzer, Kurt Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title | Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title_full | Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title_fullStr | Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title_full_unstemmed | Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title_short | Nonlinear high-frequency circuit-electromagnetic hybrid modelling of photovoltaic module |
| title_sort | nonlinear high frequency circuit electromagnetic hybrid modelling of photovoltaic module |
| topic | Electromagnetic interference Photovoltaic cells Electric circuits, Nonlinear UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/130345 |
| work_keys_str_mv | AT coetzerkurt nonlinearhighfrequencycircuitelectromagnetichybridmodellingofphotovoltaicmodule |