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This paper presents the situation of the photovoltaic power plants nationwide (Romania) and in particular the situation of the photovoltaic (PV) power plants in Mureş county. It also describes the minimal technical conditions that a PV power plant must fulfill before it is connected to the national grid. A particular case study consists of the impact that the PV power plant in Chirileu has on the...
High voltage bushing forms an essential part of a power transformer and its insulation condition is of high importance in a transformer's reliability. Transformer failure statistics indicate considerable contribution from bushing failures, which makes the monitoring of power transformer bushings essential. Several off-line and on-line methods are available for condition assessment of these components...
Large Offshore wind farms are planned in China and some are under constructions. DC grid or multi-terminal HVDC is the promising technology to delivery large offshore wind power over long distances. DC grid voltage levels need to be built to design optimal DC grid, without this voltage levels, DC grid may be sub-optimal, not cost-effective. This paper proposes the study framework of building voltage...
This paper presents the first results of the project “Optimization of fuel cell CHP systems as a component for future building energy supply in smart cities” at Bielefeld University of Applied Sciences. Main focus on modeling and simulating a fuel cell-based micro-CHP-system and scrutinizing electrical and thermal driven operating modes.
In this paper it is proposed an approach to detect, identify and correct series and shunt branch parameter errors of a transmission line using a geometrical view. Firstly it is tested if any of the measurement equations have a gross error using the J(x) index, but with the measurement error as the objective function. Next, to conclude for transmission line i-j parameter error, the corresponding measurements...
This paper analyses the performance of synchronously rotating onshore wind turbines. Variable-speed variable-pitch wind turbines are considered. The reason for synchronization of wind turbines is visual impact. Therefore, synchronization is performed during the day, while at night wind turbines operate at their normal operating mode. Wind farm of nine wind turbines is analysed in order to determine...
Nowadays, renewable energy sources are more reliable and developed than before in which wind power is a considerable factor. Therefore, A thorough comprehensive knowledge about modeling, control and responses of wind generators to practical disturbances is very necessary and vital. The double fed induction generator (DFIG) is popular and effective for a wind turbine with the noticeable characteristics...
Phasor measurement units have been installed on the power systems for grasping system static and dynamic behavior over wide area. Synchrophasor brings effective information of the power system disturbances such as the sudden supply and demand imbalance of the system. However, huge amount of synchrophasor data over the wide area power systems requires some techniques to extract the disturbances. In...
Controllable shunt reactors (CSR) are widely used in the electric energy systems of Russia, especially in the 500 kV voltage class transmission substations. Generator carrying rated active and reactive power has significant loss of active power in stator and rotor circuits, its excitation systems, and generator transformers. Installation of CSR at the power station buses leads to the reduction of...
Agent based techniques are used to coordinate demand and supply for increasing the embedding capacity of dispersed, badly predictable, renewable energy based power systems. VPPs (Virtual Power Plants) using this technology have demonstrated their feasibility in field tests and currently are scaled up to satisfy requirements for massive rollout [1]. These agent-based VPPs mostly are used in normal...
The market economy dictates the terms of unification of the energy systems of the countries that leads to a change in number of interconnections, the increase of the transmitted power, and therefore, it is necessary to reconfigure the networks and, consequently, the recalculation of their normal modes, as well as the project assessment of static stability is required. Stability is an important constraint...
A protection algorithm using a voltage-controlled overcurrent element for a looped collection circuit in a wind farm is suggested in this paper. Because the proposed algorithm uses voltage relaying signals as well as current relaying signals, any fault in the looped collection circuit can be cleared by voltage-controlled overcurrent relays located at the two adjacent relaying points, the nearest place...
A Smart Transformers (ST) is an automated transformer based on the latest power electronics and communication technologies. It aims not only at replacing the traditional transformer, but at providing also ancillary services to the grid, thanks to the greater flexibility offered by power electronics. However, in the case of grid overload caused by high load demand or high production from renewable...
The principal manifestations, causes and harms of automatic voltage control (AVC) mismatch in hierarchical and regional large-scale power systems are summarized. Based on the analysis of the essence of AVC mismatch, a game model of volt/var control is presented. The payoff function which consists of the relevant operation indices in a certain control mechanism and includes the control avails and costs...
Among the power system corrective controls, defensive islanding is considered as the last resort to secure the system from severe cascading contingencies. The objective is to maintain the stability of the resulting subsystems and to reduce the total loss of load in the system. The slow coherency based islanding can successfully be applied for the defensive islanding. In this paper, two new partitioning...
This paper proposes a novel DC-side controller for grid-connected voltage source converters during asymmetrical faults. The controller is based on a modified second order generalized integrator (SOGI). The main objective is to mitigate the second order harmonic voltage oscillation on DC link as well as the positive sequence third-order harmonic current injection into the AC grid, due to negative sequence...
Characteristics of the current emission for new developed devices are changing resulting in lower low order harmonics and an increase in high order harmonics. For the low voltage network this results in an increase in high order harmonic voltages, violating more often the limits for the harmonic voltages at the 15th and 21th order harmonic. To improve this situation harmonic current could be reduced,...
Power-to-Gas can contribute with valuable balancing power and seasonal storage capacity to future power systems. In Portugal, forecasts for 2020 show significant excess of renewable energy generation that can be transformed by power-to-gas technology and fed into the natural gas infrastructure. This work suggests an innovative approach to assess future power-togas integration potentials at the national...
In isolated electricity networks the penetration of renewable energy sources offers, among others, the advantage of distributed electricity. At the same time, as penetration levels increase, controls and regulations need to be imposed in order to alleviate rising grid integration issues. Some of these can be prevented through the use of dynamic tariffs enabling Demand Side Management. In this work,...
Forecasting and acquiring of short-term demand for frequency control reserve is a significant driver of cost for transmission system operators (TSO). A method is presented of identifying the significance of different factors by analyzing the correlation between historical data of actual reserve activation and renewable energy feed-ins, planned and unplanned power plant outages, vertical load, renewable...
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