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A novel control strategy for solving unbalanced three-phase load in low voltage power grid is proposed in this paper. The compensating current determined by a new method based on instantaneous voltage vector orientation, which overcomes the shortcomings of phase-locked loops (PLL) in the traditional detection methods. A static var generator (SVG) is employed to compensate the unbalanced current obtained...
The rotating part of a large steam turbinegenerator is typically composed of individual turbine rotors that support the turbine blades or a generator rotor that holds the generator windings. These individual parts are usually attached together by bolted couplings. Although this combined rotating part of the turbine-generator can be excited in torsion by oscillating torques applied to its various components,...
The global demand for energy is increasing at a breathtaking pace. This sharp increase in world energy demand will require significant investment in new power generating capacity and grid infrastructure. Considering the present energy scenario and the degrading environmental conditions, distributed generation seems to be a promising option. Distributed Generation generally refers to small-scale electric...
Electricity supply to Universiti Teknologi PETRONAS (UTP) is provided by two generating units at gas district cooling (GDC) plant located in the campus. Under normal operation, UTP power system is operating in island mode and during emergency, it will be connected to utility grid of Tenaga Nasional Berhad (TNB). Each generating unit is grounded through neutral earthing resistor (NER). It has been...
A black start is the process of restoring a power station to operation without relying on external power sources. Normally, the electric power used within the plant is provided from the station generators. The high-voltage grid provides station service power through the transmission lines if all the main generators are shut down. This off-site power source is not available during a wide-area outage...
The appropriate control strategy of grid-side converter (GSC) under unbalanced grid fault is important for wind power generator's fault-ride-through (FRT) capacity. Based on the basic principles of voltage space vector control, this paper studied the mathematical model of GSC under unbalanced grid conditions, and developed one efficient separation method of positive and negative sequence components...
Distributed energy resources are increasingly being connected to the utility grid by means of an inverter. The basic information necessary for these inverter-connected distribution units are the frequency and phase angle of the utility grid. The phase angle can be estimated using phase-locked loops (PLLs). Voltage unbalance, harmonics and other kinds of undesirable pertubations are common conditions...
Power quality is a main concern in power systems with generators driven by internal combustion engines, especially by low- and medium-speed diesel engines. The torque in internal combustion engines, which is the superposition of the torques from each cylinder, has periodic oscillations. These torque oscillations, once the generator is connected to the grid, result in power fluctuations and voltage...
In directly-driven permanent magnet synchronous generator (PMSG) system, a fast, robust and precise phase angle detector is most important to calculate feedback variables for control the power factor and the flow of active,reactive power. Because the grid side converter of directly-driven PMSG system is connected to the power network directly, the angle information can be easily corrupted by the distorted...
In this paper, we utilize joint time-frequency analysis to inspect frequency-varying currents at the grid connection of a variable speed wind turbine system. Through simulation experiments based on a PSCAD dynamic model, frequency-varying characteristics of the currents are investigated and compared with the wind speed. Of particular note is the appearance of nonharmonic frequencies when the wind...
The paper focuses on the design of a power interface for connecting a small power wind turbine to a single phase power plant. In general, when the wind speed drops under a given level, the traditional systems are not able to work in a satisfactory way. The proposed technique, which employs a step-up power converter for feeding the utility grid through an unidirectional full bridge inverter, allows...
This paper deals with a high-powered, low-loss and digital current disturbance generator. It can produce harmonic current, active current, inductive reactive current and capacitive reactive current, so it is able to simulate kinds of actual industrial situations. By using energy feedback technology, the generator feeds the power consumed by the current disturbance back to the grid. Thus, it can save...
This paper presents a new method for power quality improvement in four-wire islanded microgrids (MG). The main studied aspects related to power quality are voltage - frequency control, and unbalances compensation. While the voltage and frequency control were studied before by the authors of this paper, the unbalances compensation is the main topic. Two unbalance compensation controllers are used,...
The paper presents a variable speed solution for optimal operation of a group of small water turbines integrated in a medium voltage AC grid. As the efficiency of hydro machines is dependent on the water flow, which usually exhibits a large variation, operation at variable speed is considered. Due to the fact that all hydro generators are AC machines, the connection to the 50 Hz power grid can be...
The fixed pitch fixed speed wind turbines are used in China commonly. The main problem of this type of wind turbine system is the low availability of wind energy. A solution is to change it to variable speed wind turbine system and to interconnect it to power grid through rectifying circuit and inverter unit. In this work, a new-style equipment is also designed which can regulate the excitation current...
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