Birgitte Bak-Jensen

Instantaneous power compensation in three-phase systems by using p-q-r theory

This paper proposes a novel power compensation algorithm in three-phase four-wire systems by using p-q-r theory. The p-q-r theory is compared with two previous instantaneous power theories, p-q theory and cross vector theory. The p-q-r theory provides two-degrees of freedom to control the system currents by only compensating the instantaneous imaginary power without using any energy storage element. The definition of powers maintains power conservation, and agrees well with the general understanding of power. Simulation results show the superiority of p-q-r theory both in definition and compensation.

Integration of Vehicle-to-Grid in the Western Danish Power System

The Danish power system is characterized by a large penetration of wind power. As the nature of the wind power is unpredictable, more balancing power is desired for a stable and reliable operation of the power system. The present balancing power in Denmark is provided mostly by the large central power plants followed by a number of decentralized combined heat and power units and connections from abroad. The future energy plans in Denmark aim for 50% wind power capacity integration which will replace many conventional large power plant units. The limited control and regulation power capabilities of large power plants in the future demands for new balancing solutions like vehicle-to-grid (V2G) systems. In this paper, aggregated electric vehicle (EV)-based battery storage representing a V2G system is modeled for the use in long-term dynamic power system simulations. Further, it is analyzed for power system regulation services for typical days with high and low wind production in the Western Danish power system. The results show that the regulation needs from conventional generators and the power deviations between West Denmark and Union for the Coordination of Electricity Transmission (UCTE) control areas are significantly minimized by the faster up and down regulation characteristics of the EV battery storage.

Review of islanding detection methods for distributed generation

This paper presents an overview of power system islanding and islanding detection techniques. Islanding detection techniques, for a distribution system with distributed generation (DG), can broadly be divided into remote and local techniques. A remote islanding detection technique is associated with islanding detection on the utility side, whereas a local technique is associated with islanding detection on the DG side. Local techniques can further be divided into passive techniques, active techniques and hybrid techniques. These islanding detection techniques for DG are described and analyzed.

Novel STATCOM Controller for Mitigating SSR and Damping Power System Oscillations in a Series Compensated Wind Park

This paper addresses implementation issues associated with a novel damping control algorithm for a STATCOM in a series compensated wind park for mitigating SSR and damping power system oscillations. The IEEE first benchmark model on SSR is adopted with integrating aggregated self-excited induction generator-based wind turbine to perform the studies. The potential occurrence and mitigation of the SSR caused by induction generator effects as well as torsional interactions, in a series compensated wind park, are investigated. The auxiliary subsynchronous damping control loop for the STATCOM based on a novel design procedure of nonlinear optimization is developed to meet the damping torque in the range of critical torsional frequencies. The intelligent shaft monitor (ISM) scheme with synthesized special indicator signals is developed and examined in the STATCOM control structure. The performances of the controllers are tested in steady-state operation and in response to system contingencies, taking into account the impact of SCRs. Simulation results are presented to demonstrate the capability of the controllers for mitigating the SSR, damping the power system oscillation, and enhancing the transient stability margin in response to different SCRs.

A Simple Adaptive Overcurrent Protection of Distribution Systems With Distributed Generation

A significant increase in the penetration of distributed generation has resulted in a possibility of operating distribution systems with distributed generation in islanded mode. However, overcurrent protection of an islanded distribution system is still an issue due to the difference in fault current when the distribution system is connected to the grid and when it is islanded. This paper proposes the use of adaptive protection, using local information, to overcome the challenges of the overcurrent protection in distribution systems with distributed generation. The trip characteristics of the relays are updated by detecting operating states (grid connected or island) and the faulted section. The paper also proposes faulted section detection using time overcurrent characteristics of the protective relays. Simulation results show that the operating state and faulted section can be correctly identified and the protection system settings can be updated to clear the faults faster.

ARIMA-Based Time Series Model of Stochastic Wind Power Generation

This paper proposes a stochastic wind power model based on an autoregressive integrated moving average (ARIMA) process. The model takes into account the nonstationarity and physical limits of stochastic wind power generation. The model is constructed based on wind power measurement of one year from the Nysted offshore wind farm in Denmark. The proposed limited-ARIMA (LARIMA) model introduces a limiter and characterizes the stochastic wind power generation by mean level, temporal correlation and driving noise. The model is validated against the measurement in terms of temporal correlation and probability distribution. The LARIMA model outperforms a first-order transition matrix based discrete Markov model in terms of temporal correlation, probability distribution and model parameter number. The proposed LARIMA model is further extended to include the monthly variation of the stochastic wind power generation.

Probabilistic load flow: A review

This paper reviews the development of the probabilistic load flow (PLF) techniques. Applications of the PLF techniques in different areas of power system steady-state analysis are also discussed. The purpose of the review is to identify different available PLF techniques and their corresponding suitable applications so that a relatively accurate and efficient PLF algorithm can be determined for the concerned system, e.g. a distribution system with large integration of renewable energy based dispersed generations.

Detection of faults and ageing phenomena in transformers by transfer functions

In this paper the performance of a new transformer diagnosis method is tested experimentally. The method is called model-based diagnosis because the diagnosis is based on an identified model of the component-the transfer function. Two test series are carried out to evaluate the method on transformers, a sensitivity test series and an ageing test series. The purpose of the sensitivity test series is to determine how close the identified transformer model is connected to the physical condition of the modelled transformer. The purpose of the ageing test series is to determine if it is possible to identify a development in the transfer function of the transformer towards breakdown. Based on the two test series it is concluded that the detection of failures and ageing phenomena in transformers by transfer functions is dependent on detectable changes in relatively few characteristic transformer parameters-basically lumped winding capacitances, total losses and core reluctance. >

Aspects of Relevance in Offshore Wind Farm Reliability Assessment

The worldwide increase of installed wind power capacity demands the inclusion of wind farm (WF) models into power system reliability assessment. This paper looks at this issue from available literature, and presents a list of factors that highly influence offshore WF generation. An example of sequential Monte Carlo simulation applied to an offshore WF is described using a new synthetic wind-speed generator. The simulation includes some of the reliability factors highlighted in the paper and their influence on reliability assessment

Optimal Operation of Plug-In Electric Vehicles in Power Systems With High Wind Power Penetrations

The Danish power system has a large penetration of wind power. The wind fluctuation causes a high variation in the power generation, which must be balanced by other sources. The battery storage-based Plug-In Electric Vehicles (PEVs) may be a possible solution to balance the wind power variations in the power systems with high wind power penetrations. In this paper, the integration of plug-in electric vehicles in the power systems with high wind power penetrations is proposed and discussed. Optimal operation strategies of PEV in the spot market are proposed in order to decrease the energy cost for PEV owners. Furthermore, the application of battery storage based aggregated PEV is analyzed as a regulation services provider in the power system with high wind power penetrations. The western Danish power system where the total share of annual wind power production is more than 27% of the electrical energy demand is chosen as the studied case. The results show that an optimal operation of PEV in both spot market and regulation market can not only decrease the energy costs for PEV owners, but also significantly decrease the power deviations between West Denmark and Union for the Coordination of Electricity Transmission (UCTE) control areas.