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State estimation of phase shift transformers
Estimating the state of a power systems is an integral part of real-time power system analysis. In the state estimation process, measurements coming from power substations are compared to the power flow models of generators, lines and transformers to detect measurement or model errors. The method esti-mates the voltage magnitude and phase angle as well as active and reactive power flow in lines and transformers. The estimated values are then used in real-time network analysis to ensure a safe and efficient operation of the power system at all times.
Keywords: Power systems modelling, state estimation, nonlinear optimization, sensor fusion
The energy transition and liberalisation of energy markets have increased the need for phase shifting transformers to operate all network elements within their operational limits. By changing the transform-er’s complex voltage ratio, the flow in phase shift transformers and adjacent network elements can be adjusted. The tap, indicating the current complex voltage ratio, must be telemetered from substations, so that phase shift transformers are represented correctly in simulations. Erroneously telemetered or non-telemetered transformer taps of in-phase transformers (real voltage ratio, no phase shift) or symmetrical phase shifters (unit voltage ratio with phase shift) can be detected and replaced by current weighted least square state estimation methods. However, numerically robust methods to estimate asymmetrical phase shift transformers (voltage ratio and phase shift are coupled), common in the network of Swissgrid, have not been studied in detail. Therefore, this thesis pursues potential approaches to improve the estimation of asymmetrical phase shifters.
The energy transition and liberalisation of energy markets have increased the need for phase shifting transformers to operate all network elements within their operational limits. By changing the transform-er’s complex voltage ratio, the flow in phase shift transformers and adjacent network elements can be adjusted. The tap, indicating the current complex voltage ratio, must be telemetered from substations, so that phase shift transformers are represented correctly in simulations. Erroneously telemetered or non-telemetered transformer taps of in-phase transformers (real voltage ratio, no phase shift) or symmetrical phase shifters (unit voltage ratio with phase shift) can be detected and replaced by current weighted least square state estimation methods. However, numerically robust methods to estimate asymmetrical phase shift transformers (voltage ratio and phase shift are coupled), common in the network of Swissgrid, have not been studied in detail. Therefore, this thesis pursues potential approaches to improve the estimation of asymmetrical phase shifters.
The tasks of the thesis include:
1)Review of transformer models and state estimation methods
2)Performance evaluation and limitations of current state estimation methods applied to asymmet-rical phase shifters
3)Development of a state estimation method suitable for asymmetrical phase shifters
4)Evaluate the method using real measurement data from Swissgrid
Basic understanding of power system modelling, state estimation and mathematical optimization is desir-able. The master thesis will be located at the Swissgrid headquarters in Aarau. The student will also have regular meetings with the supervisor at ETH.
The tasks of the thesis include:
1)Review of transformer models and state estimation methods
2)Performance evaluation and limitations of current state estimation methods applied to asymmet-rical phase shifters
3)Development of a state estimation method suitable for asymmetrical phase shifters
4)Evaluate the method using real measurement data from Swissgrid
Basic understanding of power system modelling, state estimation and mathematical optimization is desir-able. The master thesis will be located at the Swissgrid headquarters in Aarau. The student will also have regular meetings with the supervisor at ETH.
Marc Hohmann, marc.hohmann@swissgrid.ch - contact at Swissgrid
Miguel Picallo, miguelp@ethz.ch - supervisor at ETH
Marc Hohmann, marc.hohmann@swissgrid.ch - contact at Swissgrid
Miguel Picallo, miguelp@ethz.ch - supervisor at ETH