Design of a Power Electronic On-Load Tap Changer (OLTC) Transformer for Grid Voltage Regulation Using PSCAD Software Int

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Design Of A Power Electronic On Load Tap Changer Oltc Transformer For Grid Voltage Regulation Using Pscad Software Int 1 (172.7 KiB) Viewed 34 times

Design Of A Power Electronic On Load Tap Changer Oltc Transformer For Grid Voltage Regulation Using Pscad Software Int 2 (95.88 KiB) Viewed 34 times

Design of a Power Electronic On-Load Tap Changer (OLTC) Transformer for Grid Voltage Regulation Using PSCAD Software Introduction Traditionally in distribution networks, voltage control or voltage regulation is achieved via automatic tap changer transformers. These transformers use taps made of mechanical switches that can be operated under load. In cases where repeated voltage fluctuation takes place, the mechanical switches undergo frequent wear and tear during change of taps due to the arcing phenomenon. These mechanical taps have the advantage of high overload capacity and low on-state losses. However, electronic tap changers use semiconductor switches that do not have any arcing problems and they provide flexibility in operation but suffer from much higher steady state losses. The basic idea in this assignment or coursework is to use the semiconductor switches to provide an arc-free tap changing process as shown in Figure 1 . To achieve this, two back-to-back connected Thyristors or IGBTs can be employed for the electronic switches. Also, a low-level control scheme needs to be developed for building a prototype within PSCAD software. rIgure 1: Uiv-Load i ap cnanger iranstormer Circuit Description In figure 1 above, a 13800 V(13.8KV)/4160 V transformer has five taps on the primary winding, namely −5%,−2.5% (for reduced N1 ), 0% (nominal), +2.5% and +5% (for increased N1 ). When S2 is closed (on load), the load voltage V2 reduces to 4050 from 4160 V. The objective is to maintain 4160 across the load using PSCAD and the associated control schemes. To understand the concept, the following numerical example with regard to figure 1 is provided.
With primary voltage (V1) and secondary turns (N2) fixed, either V2 or N1 must be adjusted. However, as the objective is to raise V2 from 4050 back to nominal 4160 V, then N1 must be reduced. V2 needs to increase by 4160-4050= 110 V Percentage increase in V2 is =41604160−4050​=0.026 or 2.6% We know: V2V1​=N2N1​ Or V2 =V1N2N1​ V1 and N2 are fixed, hence, N1 must be reduced (-ve sign) by 2.6%. The nearest tap to select is −2.5%. Connect terminal C to tap number −1. Objective: - Design a circuit that provides the necessary features required for Grid Voltage Regulation as discussed above (You could use Figure 1 as your design). - Discuss all steps of your circuit's design, control and calculation (You could use the calculation of numerical example shown above). - Construct your circuit within the PSCAD software. Then via simulation demonstrate the electronics tap changing concept as per the requirements discussed above in the Circuit Description section.