The installation of larger wind farms has introduced new grid integration challenges. Among these, high frequency electrical resonances caused by the cables and lines connecting the wind farm to the grid have been described in literature. These resonances may cause instability as they typically occur at frequencies close to the current controller bandwidth of the wind turbine inverter. Different mitigation techniques have been proposed in the literature to counteract these resonances. However, these techniques lack of generality as they rely on parameter tuning, which varies on a case-by-case scenario. In order to analyse the problem, an impedance-based stability approach has been applied. A systematic technique to derived the sequence-frame converter admittance
has been de�ned, and a stability study methodology including the coupling
between the positive and negative sequence converter admittances has been formulated. Compared to the existing impedance-based stability criterion, where such coupling is ignored, the proposed technique is more accurate in the system stability assessment. The study has shown that the delay introduced by the controller implementation is the main cause of the investigated wind farm stability issues. An innovative hardware implementation of the controller is proposed to compensate for this delay, without altering the converter switching frequency but making a more efficient use of the available hardware processing power. Hence, a more general and portable solution to the problem is proposed, which does not require parameter tuning. An experimental validation of the applied stability analysis methodology and of the proposed mitigation techniques has been carried out, making use of a purposed built prototype of a converter-grid system.
| Date of Award | 20 Sept 2019 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | EPSRC (Engineering and Physical Sciences Research Council) |
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| Supervisor | Agusti Egea Alvarez (Supervisor) & Lie Xu (Supervisor) |
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