Kuntal Satpathi

Protection strategies for LVDC distribution system

DC power system is gaining popularity. Research is being conducted worldwide on implementation of LVDC (low voltage direct current) and MVDC (medium voltage direct current) in applications such as ship power systems. One major hurdle to this path is the immaturity of the protection systems. This paper deals with the modeling of LV/MVDC power system with different marine loads and faults. Since LV/MVDC power systems are still in preliminary stages, their modeling and fault analysis will help in addressing the requirements of various protection strategies. The system modeling and fault simulations are done in simulation software Power Systems Computer Aided Design (PSCAD). The components of DC ship power system are also described.

Flux estimation based dc bus voltage control in marine dc power system

DC power systems are increasingly being considered for marine applications as they provide certain advantages. Proper modeling and control approach of the system components with suitable dc bus voltage control and power sharing among the generators are important aspects for smooth functioning of the marine dc power system. Conventional bus voltage control in ac systems is usually achieved by using automatic voltage regulator (AVR), which requires the measurement of the generator terminal voltage. Since generators interfaced with the voltage source converter (VSC) system are envisaged in the marine dc power system, determination of generator terminal voltage for voltage control becomes difficult as the measurement is comprised primarily of PWM waveforms. This paper implements the closed loop flux estimation of brushless synchronous generator (BLSG) for dc bus voltage control. This paper also covers the droop control for power sharing among the generators. The proposed method is implemented in Opal-RT which is a real-time simulation platform and the results are discussed in the paper. Apart from the results, the limitations of the closed loop flux control are also highlighted in the paper.

Suitability of Rogowski coil for DC shipboard protection

The achievements made in the field of DC shipboard power systems over the past decade have been impressive. However, the widespread acceptance of DC shipboard power systems is still hindered by the difficulty in ensuring protection of the system. One of the challenges in designing the protection systems is the selection of current sensors. This paper aims to study the suitability of Rogowski coil for use in DC shipboard power system protection relays. This paper describes the design and implementation issues of the Rogowski coil. It is shown that the geometrical orientation of the Rogowski coil has a major impact on the measurement sensitivity of fault currents.

Modelling of DC shipboard power system

Modelling and simulation of emerging DC shipboard power system (SPS) is required to validate the hardware design, converter control and protection algorithms. As DC SPSs may be large and complicated, the simulation of such systems using high fidelity models generally consumes much time and the validation of performance using multiple test scenarios becomes impractical. An alternative method is to conduct such simulations in real-time using a multi-core simulation platform. Real-time simulation also allows protection relays (running embedded protection algorithms) to be verified through ‘hardware in the loop’ techniques. In this paper we discuss the simulation of DC SPSs in real-time using Opal-RT simulation platform. Firstly the system is modelled for non-real-time simulation. Subsequently these models are converted for real-time simulation and executed using RT-Lab on the Opal-RT target. Modelling and control approaches of DC SPS and some of the attributes of Opal-RT are also discussed.

Modeling and Real-Time Scheduling of DC Platform Supply Vessel for Fuel Efficient Operation

DC marine architecture integrated with variable speed diesel generators (DGs) has garnered the attention of the researchers primarily because of its ability to deliver fuel efficient operation. This paper aims in modeling and to autonomously perform real-time load scheduling of dc platform supply vessel (PSV) with an objective to minimize specific fuel oil consumption (SFOC) for better fuel efficiency. Focus has been on the modeling of various components and control routines, which are envisaged to be an integral part of dc PSVs. Integration with photovoltaic-based energy storage system (ESS) has been considered as an option to cater for the short time load transients. In this context, this paper proposes a real-time transient simulation scheme, which comprises of optimized generation scheduling of generators and ESS using dc optimal power flow algorithm. This framework considers real dynamics of dc PSV during various marine operations with possible contingency scenarios, such as outage of generation systems, abrupt load changes, and unavailability of ESS. The proposed modeling and control routines with real-time transient simulation scheme have been validated utilizing the real-time marine simulation platform. The results indicate that the coordinated treatment of renewable-based ESS with DGs operating with optimized speed yields better fuel savings. This has been observed in improved SFOC operating trajectory for critical marine missions. Furthermore, SFOC minimization at multiple suboptimal points with its treatment in the real-time marine system is also highlighted.

Protection of MVDC shipboard power system using Rogowski coil

One of the major challenges faced in the design of DC shipboard power systems (SPS) is the provision of effective DC protection. The selection of the current sensors plays an important role in the detection of fault current in DC systems. The Rogowski coil has emerged as a popular choice of current sensor for use in DC SPS protection system primarily because of its fast response and non-saturable property. This paper presents the modelling and operation of the Rogowski coil and its integration into protection algorithms to achieve effective protection. With this method, the transient conditions experienced during faults can be effectively identified and differentiated.