Load modeling from smart meter data using neural network methods

Electricity load modeling plays a critical role to conduct load forecasting or other applications such as non-intrusive load monitoring. For such a reason, this paper investigates a comparison study of two common artificial neural network methods (Multilayer perceptron (MLP) and radial basis function neural network (RBF-NN) for home load modeling application. The accuracy of load modeling using neural network methods highly depends on chosen variables as the input data set for the networks. For this purpose, data including weather, time, and consumer behavior are considered as the input dataset to train the networks. The results of this study show that the RBF-NN model has higher accuracy in training data. On the other side, the MLP model outperforms in test data. To sum up, the results prove that the load model obtained by MLP has a better performance in terms of mean square and root mean square error indices

Deep Adaptive Ensemble Filter for Non-Intrusive Residential Load Monitoring

Identifying flexible loads, such as a heat pump, has an essential role in a home energy management system. In this study, an adaptive ensemble filtering framework integrated with long short-term memory (LSTM) is proposed for identifying flexible loads. The proposed framework, called AEFLSTM, takes advantage of filtering techniques and the representational power of LSTM for load disaggregation by filtering noise from the total power and learning the long-term dependencies of flexible loads. Furthermore, the proposed framework is adaptive and searches ensemble filtering techniques, including discrete wavelet transform, low-pass filter, and seasonality decomposition, to find the best filtering method for disaggregating different flexible loads (e.g., heat pumps). Experimental results are presented for estimating the electricity consumption of a heat pump, a refrigerator, and a dishwasher from the total power of a residential house in British Columbia (a publicly available use case). The results show that AEFLSTM can reduce the loss error (mean absolute error) by 57.4%, 44%, and 55.5% for estimating the power consumption of the heat pump, refrigerator, and dishwasher, respectively, compared to the stand-alone LSTM model. The proposed approach is used for another dataset containing measurements of an electric vehicle to further support the validity of the method. AEFLSTM is able to improve the result for disaggregating an electric vehicle by 22.5%

Thyristor based short circuit current injection in isolated grids

Embargoed Access, IEEEs general regulations (manuscript version for OA after 24 mnths embargo from publication date) Link to publisher's version: http://doi.org/10.1109/ECCE.2016.7855523This paper proposes a thyristor based short circuit current injector for providing short circuit current in isolated and weak grids, where sufficient fault current to trigger circuit breakers may not be available. This will allow the use of conventional miniature circuit breakers, which requires high fault current for instantaneous tripping. The method has been validated through experiments

A Novel Technique to Mitigate the Overlap-Time Effect in Current Source Inverters

Generally, the current source inverter is considered more reliable than the voltage source inverter due to the presence of inductor as an energy storage element on the DC link, but a disruption in the inductor current could significantly risk its reliability. To guarantee the reliable operation of current source inverter, an overlap time must be added to the gate signals of its switches. This ensures the safe operation of current source inverter but results in increased total harmonic distortion and reduction of DC current utilization ratio. This paper proposes a new technique for reducing the effect of overlap time and improving the performance of pulse width modulated current source inverter. The proposed technique modifies the level-shifted sinusoidal pulse width modulation to mitigate the effect of overlap time. In this paper, the working principle of the proposed technique is presented in detail, and a mathematical relation between the level shifting and overlap time is established. Moreover, a function for the approximation of output AC current is also presented. Finally, results from computer simulations and experiments are presented which validate the effectiveness of the proposed technique

Når blir skipsfarten grønn?

Avisartikkel Fremover 25.4.2018 https://www.fremover.no/debatt/leserbrev/grovfjord/nar-blir-skipsfarten-gronn/o/5-17-401673n av utfordringene i forbindelse med dagens skipsfart er utslipp til luft, hovedsakelig karbondioksid og nitrogenoksider. Disse utslippene er knyttet til oljefyrte forbrenningsmotorer som dominerer dagens skipsflåte. Det er overveiende sannsynlig at det er en direkte sammenheng mellom global oppvarming og utslipp av klimagasser. Utslipp til luft kan også bidra til sur nedbør og svevestøv, for å nevne noe. Disse forurensende petroleumsressursene vil etter hvert armes ut og før eller senere ta slutt

A Review of Power Converters for Ships Electrification

Fully electric ships have become popular to meet the demand for emission-free transportation and improve ships' functionality, reliability, and efficiency. Previous studies reviewed the shipboard power systems, the different types of shipboard energy storage devices, and the influences of the shore-to-ship connection on ports' electrical grid. However, the converter topologies used in the electrification of ships have received very little attention. This article presents a comprehensive topological review of currently available shore-to-ship and shipboard power converters in the literature and on the market. The main goal is to anticipate future trends and potential challenges to stimulate research to accelerate more efficient and reliable electric ships

Conformal Transformation Analysis of Capacitive Wireless Charging

This paper studies the capacitive coupling in a capacitive power transfer (CPT) system designed for charging applications. It proposes mathematical models using the conformal transformation for calculating air-gapped and underwater capacitance and verifies the proposed models using COMSOL multiphysics and measurements. The measured results show that we can achieve nano-farad capacitance ranges if we submerge the capacitor in seawater. The seawater’s capacitance slightly changes when we increase the gap distance or the operating frequency. As the under seawater CPT system can be an attractive option for loosely-coupled charging applications, we further examine the system by focusing on the crosscoupling effects. The results show that the cross-coupling between the plate degrades the system’s power transfer capability and efficiency. With negligible cross-coupling effects, the system gives 129 W output power at an efficiency of 81.2%

Reliable electric power conversion for connecting renewables to the distribution network

When connecting distributed power generation systems to the utility grid, a power converter is normally placed between the main grid and the local micro-grid, at the point of common coupling. In order to synchronize the converter to the utility grid voltages, a synchronizing circuit is needed. A common way of doing this, is to use a phase-locked loop (PLL). This circuit estimates a voltage reference angle which is fed to the control system of the power converter. One of the simplest PLL designs is based on the grid voltage zero crossings. The drawback of this method is that no information about the grid voltage conditions is available in the interval between the zero crossing. The design has been implemented and successfully tested on a Field Programmable Gate Array (FPGA) circuit connected to a power converter. A more advanced way of designing a PLL is by using voltage vector control. The method is more complex and time consuming. On the other hand, information about the grid voltage condition is always available. The design fails to run properly if the grid voltages are unbalanced or distorted. In order to improve the performance, a multi-variable filter tuned at nominal grid frequency may be added. This solution has been implemented on an FPGA circuit and successfully tested. The multi-variable filter will cause an angle displacement if the grid frequency deviates from its nominal value. The author proposes a method called Adaptive Signal Cancellation (ASC), in order to make the PLL frequency independent. The method is based on a method called Delayed Signal Cancellation (DSC) where the grid voltages are inputted and symmetric voltage components are outputted. Instead of delaying signals, the ASC is phase shifting signals, obtaining approximately the same performance. In addition to providing the control circuit with an estimated voltage reference angle, the circuit also outputs signals determining grid voltage conditions: voltage level, symmetry and frequency. These signals can be used in an overhead control structure taking care of power management and protection

Når blir skipsfarten grønn?

n av utfordringene i forbindelse med dagens skipsfart er utslipp til luft, hovedsakelig karbondioksid og nitrogenoksider. Disse utslippene er knyttet til oljefyrte forbrenningsmotorer som dominerer dagens skipsflåte. Det er overveiende sannsynlig at det er en direkte sammenheng mellom global oppvarming og utslipp av klimagasser. Utslipp til luft kan også bidra til sur nedbør og svevestøv, for å nevne noe. Disse forurensende petroleumsressursene vil etter hvert armes ut og før eller senere ta slutt

Thyristor based short circuit current injection in isolated grids

This paper proposes a thyristor based short circuit current injector for providing short circuit current in isolated and weak grids, where sufficient fault current to trigger circuit breakers may not be available. This will allow the use of conventional miniature circuit breakers, which requires high fault current for instantaneous tripping. The method has been validated through experiments