Pub Date : 2020-11-02DOI: 10.1109/eGRID48559.2020.9330629
Niklas Wehbring, J. Saat, A. Moser
The integration of DC technology into existing AC systems represents a possible response to challenges at all grid levels. As consequence, hybrid AC/DC systems emerge providing more flexibility in grid operation. To guarantee secure and efficient network operation of these systems, adequate operating points for controllable devices such as converters are required. We present a comparison of suitable hierarchical control concepts for different types of hybrid AC/DC networks with focus on medium-voltage. For this purpose, we evaluate three different OPF formulations used for regular set point updates. The OPFs are tested on an adapted 511 bus MV network based on real data. Moreover, we provide solutions to locally adapt set points and topological fall back measures in case of outages or changes of system state including an overview of different local controllers for set point attainment and retention.
{"title":"Three-level control architecture for hybrid AC/DC distribution grids","authors":"Niklas Wehbring, J. Saat, A. Moser","doi":"10.1109/eGRID48559.2020.9330629","DOIUrl":"https://doi.org/10.1109/eGRID48559.2020.9330629","url":null,"abstract":"The integration of DC technology into existing AC systems represents a possible response to challenges at all grid levels. As consequence, hybrid AC/DC systems emerge providing more flexibility in grid operation. To guarantee secure and efficient network operation of these systems, adequate operating points for controllable devices such as converters are required. We present a comparison of suitable hierarchical control concepts for different types of hybrid AC/DC networks with focus on medium-voltage. For this purpose, we evaluate three different OPF formulations used for regular set point updates. The OPFs are tested on an adapted 511 bus MV network based on real data. Moreover, we provide solutions to locally adapt set points and topological fall back measures in case of outages or changes of system state including an overview of different local controllers for set point attainment and retention.","PeriodicalId":296524,"journal":{"name":"2020 5th IEEE Workshop on the Electronic Grid (eGRID)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116943259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-02DOI: 10.1109/eGRID48559.2020.9330631
Moazzam Nazir, J. Enslin
The HVDC systems are typically utilized for long distance power transmission due to their advantages like minimal-loss bulk power transmission, advanced control features and capability to interconnect asynchronous AC networks. Among the two most common HVDC technologies; voltage source converter HVDC (VSC-HVDC) and line commutated converter HVDC (LCC-HVDC), the former has enhanced control features along with non-dependence upon synchronous machines for commutation. However, it suffers from higher losses due to the involvement of high-speed switching, involves sophisticated gate-driver circuitry, has a weak overload capability, suffers from non-availability in higher ratings and lower reliability due to higher component count. This paper is focused on enhancing the reliability along with reduced control complexity of the highly mature LCC-HVDC technology by converting the inverter-side transformer into smart one through integration of a power electronics-based module between its neutral and converter-station ground. The module enables the conventional converter transformer to perform voltage regulation, harmonics isolation, voltage and impedance balancing. This leads to enhanced robustness of LCC-HVDC against commutation failure, minimization of DC power recovery time and protection against disturbances, such as, solar storms and high-elevation nuclear explosions. The proposed approach is also depicted to introduce power flow control capabilities in AC-tie lines for parallel AC/DC transmission. The PSCAD/EMTDC is utilized to evaluate the proposed approach on the CIGRE benchmark model and the results verify it as a promising solution to multiple HVDC problems.
{"title":"Hybrid Smart Converter Transformer for HVDC with Advanced Grid Support","authors":"Moazzam Nazir, J. Enslin","doi":"10.1109/eGRID48559.2020.9330631","DOIUrl":"https://doi.org/10.1109/eGRID48559.2020.9330631","url":null,"abstract":"The HVDC systems are typically utilized for long distance power transmission due to their advantages like minimal-loss bulk power transmission, advanced control features and capability to interconnect asynchronous AC networks. Among the two most common HVDC technologies; voltage source converter HVDC (VSC-HVDC) and line commutated converter HVDC (LCC-HVDC), the former has enhanced control features along with non-dependence upon synchronous machines for commutation. However, it suffers from higher losses due to the involvement of high-speed switching, involves sophisticated gate-driver circuitry, has a weak overload capability, suffers from non-availability in higher ratings and lower reliability due to higher component count. This paper is focused on enhancing the reliability along with reduced control complexity of the highly mature LCC-HVDC technology by converting the inverter-side transformer into smart one through integration of a power electronics-based module between its neutral and converter-station ground. The module enables the conventional converter transformer to perform voltage regulation, harmonics isolation, voltage and impedance balancing. This leads to enhanced robustness of LCC-HVDC against commutation failure, minimization of DC power recovery time and protection against disturbances, such as, solar storms and high-elevation nuclear explosions. The proposed approach is also depicted to introduce power flow control capabilities in AC-tie lines for parallel AC/DC transmission. The PSCAD/EMTDC is utilized to evaluate the proposed approach on the CIGRE benchmark model and the results verify it as a promising solution to multiple HVDC problems.","PeriodicalId":296524,"journal":{"name":"2020 5th IEEE Workshop on the Electronic Grid (eGRID)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133912928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-02DOI: 10.1109/eGRID48559.2020.9330670
G. C. Leandro, K. Sano, N. Okada
This paper proposes a protection circuit for the shunt capacitor equipped with a series inverter (active SC) under a voltage sag in the distribution grid. The voltage sag causes the discharge of the shunt capacitors, resulting in a large inrush current that may damage the series inverter. The proposed protection circuit is composed of varistors connected in parallel with the inverters, and a series AC circuit breaker. When the large inrush current flows into the inverter, all of its power devices are turned off. Then, almost all of the inrush current flows into the varistors. As a result, the proposed method mitigates the inrush current of the inverter. Computer simulations are carried out to investigate the behavior of the active SC during balanced and unbalanced voltage sags. Simulation results demonstrate that the proposed protection circuit is able to mitigate the overcurrent in the inverter by a factor close to 2.5 under a balanced voltage sag. It was also verified that the circuit protects the inverter from unbalanced voltage sags caused by a single and double-line-to-ground faults.
{"title":"A Protection Circuit for the Shunt Capacitor equipped with a Series Inverter under Voltage Sags","authors":"G. C. Leandro, K. Sano, N. Okada","doi":"10.1109/eGRID48559.2020.9330670","DOIUrl":"https://doi.org/10.1109/eGRID48559.2020.9330670","url":null,"abstract":"This paper proposes a protection circuit for the shunt capacitor equipped with a series inverter (active SC) under a voltage sag in the distribution grid. The voltage sag causes the discharge of the shunt capacitors, resulting in a large inrush current that may damage the series inverter. The proposed protection circuit is composed of varistors connected in parallel with the inverters, and a series AC circuit breaker. When the large inrush current flows into the inverter, all of its power devices are turned off. Then, almost all of the inrush current flows into the varistors. As a result, the proposed method mitigates the inrush current of the inverter. Computer simulations are carried out to investigate the behavior of the active SC during balanced and unbalanced voltage sags. Simulation results demonstrate that the proposed protection circuit is able to mitigate the overcurrent in the inverter by a factor close to 2.5 under a balanced voltage sag. It was also verified that the circuit protects the inverter from unbalanced voltage sags caused by a single and double-line-to-ground faults.","PeriodicalId":296524,"journal":{"name":"2020 5th IEEE Workshop on the Electronic Grid (eGRID)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129789201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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