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Your search keyword '"Jovcic, Dragan"' showing total 189 results
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189 results on '"Jovcic, Dragan"'

6. Optimisation of topology, rating, control and insulation coordination of a large series–parallel DC windfarm.

Author

Shehu, Ibrahim Ahmad, Jovcic, Dragan, and Li, Peng

Subjects
OPTIMIZATION algorithms, NET present value, OFFSHORE wind power plants, DRILLING platforms, TOPOLOGY, VOLTAGE control, WIND power plants
Abstract

This study presents the design of a large DC series‐parallel windfarm that considers the key operational challenges in determining the optimal generator equipment rating and DC transmission voltage control. With this topology, offshore platform is not needed, but wind speed dispersion over windfarms and generator outage possibilities demand generator DC output voltages beyond their ratings. An optimization algorithm is developed along with a complete cost model, which includes operational and capital costs with all topology options, in order to inform design decisions. The results are evaluated on a 100‐generator, 25 × 4, 1 GW, 525 kV test wind farm and performance is verified using detailed PSCAD/EMTDC time‐domain simulation. The key finding is that a positive net present value (NPV) is achieved, avoiding power curtailment even under 3% generator outage, when an overvoltage coefficient of 1.145 pu is utilised on all wind generators, assuming use of a suitable DC transmission voltage control. Further, a wide‐ranging parameter sensitivity analysis is performed, and tower arrangement for insulation requirements is proposed. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Defining Short-Time Withstand Current for DC Switchgear in HVDC Systems

Author

Jovcic, Dragan, Shiiki, Motoharu, and Toyoda, Mitsuru

Abstract

This article proposes a methodology for characterizing short-time withstand current with high voltage direct current (HVDC) switchgear, which aims informing the ongoing standardization work on DC switchgear in IEC TC17. To maintain commonalty in methodology with AC switchgear standards, it is proposed that the DC short-time withstand stress is described with an equivalent RMS current and duration, in addition to a peak fault current. Considering much different DC system dynamics, a wide range of DC topologies and DC fault scenarios, it is proposed to utilise Joule integral to determine rated short-time withstand current. DC systems are classified in 3 topologies to account for the industry HVDC experience and the development of future DC grids: VSC HVDC, LCC HVDC, and DC systems with DC CBs. For each topology, short-circuit current waveform is characterized and expressions for rated parameters are derived, considering relevant operating conditions with worst-case stresses. The accuracy of analytical expressions, and the recommended numerical values are verified using detailed simulation models with relevant test cases and a range of operating conditions.

Published
2024
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12. Rotating Frame, Average Value Converter Modeling: Basic principles in building analytical models

Author

Jovcic, Dragan

Abstract

Electrical power converters have become indispensable units in modern power systems, with an increasing number of installations, application fields, and ratings. They are used for power conditioning; for controlling network, regulating generation, or load power; for integrating storage systems; and importantly for integrating most renewable energy plants. As a typical example, a modern wind generator will have two ac–dc converters back-to-back connected, facilitating optimal energy extraction from variable speed wind turbines and ensuring that the power plant meets network connection requirements.

Published
2023
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33. Bidirectional Hybrid HVDC CB With a Single HV Valve.

Author

Jovcic, Dragan, Zaja, Mario, and Hedayati, Mohammad Hassan

Subjects
*FAULT currents, *HYBRID integrated circuits, *BIPOLAR transistors, *TOPOLOGY, *HARDWARE
Abstract

This paper examines two new bidirectional hybrid dc circuit breaker (CB) topologies for application in meshed dc grids. The goal is to retain performance of hybrid dc CB with bidirectional current interruption while reducing semiconductor count, dc CB size, and weight. The fault current is routed to the unidirectional internal valve using multiple additional ultrafast disconnectors. Operation of both topologies is studied using a 320-kV, 16-kA simulation model, as well as demonstrated on a 900-V, 500-A lab prototype. The control systems are presented and discussed in detail. The low-voltage hardware prototypes verify performance of several new technical and operating solutions in laboratory conditions. A comparison is made with the existing dc CB topologies and performance and reliability compromises of each topology are assessed. The conclusion is that it might be possible to halve the dc CB semiconductor count while retaining same 2 ms opening speed and bidirectional operation. [ABSTRACT FROM AUTHOR]

Published
2020
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