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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...
Through the effective combination of energy storage technologies, distributed generations, load and various controllers, Microgrid is energy-efficient and could realize the independent control. Microgrid is an important direction for the development of future grid. Microgrid is now actively promoted all over the world. Its technical requirements of operation control and protection have not been standardized...
This paper examines the use of the symmetrical components theory for the representation of unbalanced conditions, when using the concept of analog emulation for highspeed power system analysis. This concept has been proven and validated through the realization of a mixed-signal hardware platform dedicated to power system studies. Computations related to the grid are handled by analog electronics,...
A Smart Transformer (ST) is a power electronics-based transformer that aims not only to substitute the traditional transformer but to upgrade also the LV and MV grid. In order to limit the costs, the ST must be carefully designed, constraining the current carried by the ST. In this paper a Combined Frequency and Voltage Controller is proposed, in order to manage a possible overload without derating...
The classical equal area criterion in the power-angle domain, which is typically used for power systems planning/stability studies, is modified to the time domain for out-of-step protection. Wide-area measurements are necessary to obtain the power-angle information if the traditional equal area criterion is applied for out-of-step detection. However, its time-domain modification requires only the...
This paper compares the performance of different droop-based control techniques in an islanded microgrid that operates solely on electronically interfaced distributed energy resources (DERs). Specifically, the following techniques are compared: conventional droop-based control including a full pulse width modulating (PWM)-based voltage source converter (VSC) with power, voltage and current controls;...
In the previous paper [1], transient stability of power system with high-penetration photovoltaic (PV) was assessed by simulation analysis of IEEE 9-bus power system model with infinite bus. Through the simulation analysis, it was concluded that the transient stability is better in the case with PV without low-voltage ride-through (LVRT) capability installed. This is because the synchronous generator...
Modeling of distributed generation and associated controllers have a considerable influence on the results of transient stability analysis. Synchronous generators and induction generators are two common types of generators which are used for distributed generation, for example in micro-turbines and wind turbines. In this paper, the effect of detail of modeling of synchronous generators on the transient...
Spontaneous faults in medium voltage grid are often preceded by a number of self-extinguishing faults. Therefore, it is useful to recognize and localize the self-extinguishing faults. The detected component could then be repaired or replaced in advance, to prevent the persistent fault This paper describes the self-extinguishing fault phenomena and the recognition methodology. The techniques to locate...
Equipping one support structure with DC and AC systems in parallel can increase the transport capacity of existing transmission corridors. The constant electric field of the DC system induces a constant DC component into the AC systems in near vicinity. All magnetic equipment including an iron core is in danger to saturate. Especially current transformers (CTs) for protection issues can be influenced...
Applications of superconductivity in power systems, especially in transmission systems, is a subject of study since 1970s. Superconductors' advantage of providing an almost lossless transmission system, due to the non-existence of joule losses, has been highlighted during the last decades. However, the absence of resistance and its ability to damp oscillatory phenomena, which in case of a superconducting...
The power rating of Modular Multilevel Converter based HVDC has increased rapidly over the past decade, with individual links in the gigawatt power range now technically feasible and further power increases on the horizon. Such large links may be required to provide ancillary services such as fast frequency response or emergency power re-routing in the event of a system disturbance. Providing such...
This paper propose a test grid for investigation of slow coherency concept in nowadays active distributions power systems with small scale hydro units. The slow coherency concept is studied by increasing the model complexity of the small scale hydro generators. The purpose is to obtain a small signal equivalent suitable for the studies of the main bulk transmission system.
The concept of Wide-Area Measurement Systems (WAMS) envisages the transmission of current and voltage phasor samples from remote Phasor Measurement Units (PMUs) to control centres, relays or controllers. Compression of the high frequency samples of sinusoidal waveforms into phasors is usually done using Discrete-Fourier Transform(DFT)-like algorithms. The phasor data is normally useful only when the...
Transient stability of photovoltaic-hydro microgrid systems is poor due to lack of inertia and the intermittent nature of photovoltaic systems. The stability of such systems can be improved by using virtual synchronous machines which add inertia into the system to allow for higher PV penetration without losing stability. A PV-hydro system was simulated in MATLAB/Simulink to analyze the transient stability...
This paper presents experiences in applying electromechanical oscillation damping estimation methods in real-time use from the transmission system operator's perspective. A wavelet based method and a method based on the multivariate autoregressive model are used for real-time monitoring of electromechanical oscillations. The paper analyzes the performance of these methods both under transient and...
Transient stability of doubly-fed induction machine (DFIM) in hydro pumped storage plant (PSP) is analyzed and compared with synchronous machine in this paper. Model of turbine governor and model of converter control of DFIM are presented as they are applied in computer software for dynamic analyses of electric-power system. The principle of frequency control—i.e., permanent droop—and control of network...
The increase in the size of the current eletric power systems (EPSs) has led to the development of monitoring techniques of EPSs, which includes SCADA (Supervisory Control and Data Acquisition) systems, WAMS (Wide Area Measurement System) and also, disturbance records systems. Disturbance records systems are based on oscillographic records, generated by Digital Fault Recorders (DFRs) and allows the...
Space vector theory is a widely used tool to model synchronous and asynchronous machines. In this paper the induction machine dynamic equations were written in terms of space vectors, employing the stationary reference frame. Also, a general short-circuit current expression was derived and decomposed into positive and negative sequence components. In order to validate and compare the model developed...
This paper describes the influence of replacing centralised generation by distributed generation (DG) with a full converter (e.g. type 4 wind turbines, solar power) from a short-circuit power and a voltage support point of view. To allow investigating the influence the settings of the voltage support of the DG units, an iterative approach based on linear network calculations is used. Inherently, the...
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