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

Reconfiguration and load balancing in the LV and MV distribution networks for optimal performance

Abstract: To get the distribution network to operate at its optimum performance in an automated distribution system reconfiguration was been proposed and researched. Considering, however, that optimum performance implies minimum loss, no overloading of transformers and cables, correct voltage profile, and absence of phase voltage and current imbalances, network reconfiguration alone is insufficient. It has to be complemented with techniques for phase rearrangement between the distribution transformer banks and the specific primary feeder with a radial structure and dynamic phase and load balancing along a feeder with a radial structure. This paper contributes such a technique at the low-voltage and medium-voltage levels of a distribution network simultaneously with reconfiguration at both levels. While the neural network is adopted for the network reconfiguration problem, this paper introduces a heuristic method for the phase balancing/loss minimization problem. A comparison of the heuristic algorithm with that of the neural network shows the former to be more robust. The approach proposed here, therefore for the combined problem, uses the neural network in conjunction with a heuristic method which enables different reconfiguration switches to be turned on/off and connected consumers to be switched between different phases to keep the phases balanced. An application example of the proposed method using real data is presente

Theoretical analysis of tuned HVAC line for low loss long distance bulk power transmission

One of the main objectives of the smart grid initiative is to enable bulk power transmission over long distance, with reduced transmission losses. Besides the traditional high-voltage alternating current (HVAC) transmission, with the advancement in power electronics, high-voltage direct current (HVDC) transmission is increasingly becoming important. One of the main factors impacting the transmission line parameters and the losses is the length of the transmission line (overhead). In this paper, a concept of tuned high-voltage AC line is presented for long (>250>250 km) transmission line. A tuned line is where the receiving-end voltage and current are numerically equal to the corresponding sending-end values. This paper presents the detailed theoretical analysis of the tuned HVAC line, suggesting adaptation of the transmission frequency as per the length of the line. The simulation of a tuned HVAC line is performed using the PSCAD/EMTDC. Simulation results for two different line lengths, substantiate the theoretical analysis of reducing the reactive power absorbed in the line, while increasing the active power transmission.Accepted versio

Disturbance detection in the MV and the LV distribution networks using time-domain method

With the growing need for disturbance-free power distribution, there has been significant focus under the ‘Smart Grid’ initiative on fault and disturbance analysis. Compared to the high voltage (HV) transmission systems where high-end relays can be used, medium- and low-voltage (MV, LV) distribution systems employ low-end relays for cost reason. Therefore, computationally inexpensive signal processing algorithms are needed for disturbance identification at the MV and the LV distribution systems. In this paper, a novel amplitude tracking square wave concept is presented, which can effectively represent the complex sinusoidal signals under disturbance. The amplitude tracking square wave is very sensitive to any degradation introduced in the sinusoidal signals due to disturbances. These are typically reflected in the time-domain as spikes in the square wave, without requiring any frequency analysis. This makes it particularly attractive for embedding into the MV and the LV relays with limited computational resources. Successful application of the algorithm on real disturbance records substantiate its potential.Accepted versio

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.NRF (Natl Research Foundation, S’pore)Accepted versio

Modeling of Room Temperature Dynamics for Efficient Building Energy Management

peer reviewedHeating, ventilating and air-conditioning systems have a significant share in the energy consumed by buildings. Modeling of room temperature dynamics is the first-step in designing an efficient air-conditioning system. In this regard, this paper proposes a semi-nonlinear thermal model: ordinary differential equation, with parameters as nonlinear functions of ambient temperature and cooling air flow-rate. To validate the performance of the model, a three-roomed building, equipped with an air-conditioning system is modeled, and Navier-Stokes equations are solved to simulate the temporal evolution of temperatures for different ambient temperatures and cooling air flow-rates. The steady-state temperature and transient solution parameters of the thermal model are assumed to be polynomial functions of ambient temperature and flow-rate, and are determined by minimizing the errors between the thermal model- and the computational fluid dynamics-based solutions of final and transient temperatures, respectively. The proposed thermal model of third-order and nonlinear type transient coefficients is shown to predict the temporal evolution of temperature accurately. Further increase in prediction accuracy is achieved by recursively updating the parameters online using extended Kalman filter. The high prediction accuracy of the proposed thermal model makes it a potential candidate for the design of an optimal temperature regulator