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Introduction
Published in L. Ashok Kumar, S. Albert Alexander, Computational Paradigm Techniques for Enhancing Electric Power Quality, 2018
L. Ashok Kumar, S. Albert Alexander
Interruption can result in loss of production in an office, retail market, or industrial factory. The loss of electrical service and the time required to return back to electrical service causes lost production. Some types of events cannot “ride through” even short interruptions. “Ride through” is the ability of equipment to tolerate the power disturbance for a particular time. For example, in a plastic injection molding plant, a short interruption of 0.5 second takes 6 hours to restore production.
Frequency Controls for AC Motors
Published in Sylvester J. Campbell, Solid-State AC Motor Controls, 2020
The four important conditions of incoming line voltage are discussed below. Allowable voltage variation from nameplate for rated output. Most inverters are designed for operation with voltage variations at the input terminals of +10% and -5%. The +10% limit is usually based on the peak inverse voltage withstand capability of the power devices. The -5% generally means that the inverter will stay on line but will not necessarily develop rated output horsepower. This is particularly true for PWM inverters unless a chopper stage is added to the dc link.Allowable voltage unbalance between phases. Unbalanced incoming line voltages can result in unbalanced currents in the input or converter stages. Most manufacturers design for input line voltage unbalances not to exceed 2% phase to phase.Allowable voltage distortion in the voltage waveform. Distortion from the fundamental sine wave of line voltage, such as may be caused by other inverters or rectifiers can affect inverter performance. This was discussed in Section 5.13.Ride-through capability during voltage interruption or reduction. “Ride-through capability” refers to the length of time the inverter will attempt to stay in the on condition in the event of a power interruption. There are no generally agreed upon numbers for this capability, which is usually defined in terms of cycles of the incoming line frequency. If the ride-through capability is too long, the driven process will begin to slow down, and could become difficult to restart without elaborate restart sequencing, possibly including with other parts of the process. If the time period is too short, nuisance tripping can result. An in-between area appears to be on the order of five cycles. This is also the typical hold-in time for other electrical devices using electromagnetic relays. (There is usually no point in trying to hold the inverter on the line when everything else has dropped off!)
Discriminatory Protection Analysis of Three-Phase Asynchronous Motors During Power Disturbances
Published in Electric Power Components and Systems, 2019
Nsilulu Tresor Mbungu, Ramesh C. Bansal, Raj M. Naidoo, Mandangi Jean-Pierre Bazolana
Figures 4–7 show the different impacts that occur in the stator during the voltage disturbance. This has an essential value of transient stator current and depends on the dip value of voltage disturbance and the duration of the short interruption. As it is shown in Figures 4(a) and 6(a), when the voltage dip and the remaining voltage on the IM have significant value, the transient stator current is about 18 per unit value of the nominal stator current. This is decreasing, and it lasts up to 0.6 s to reach the standard per unit value of the stator current. Therefore, the protection of an IM for this specific study case can be discriminated according to the results found in Figures 4(a) and 6(a). By allowing an IM to ride through voltage disturbance due to voltage sag or short interruption, the peak of stator current and the transient time can be considered to discriminate all protections of an IM. Usually, the time of voltage sag that an IM can ride through lasts from 0.3 to 0.6 s, but this study focusses explicitly in the context of voltage sag that lasts up 0.1 s and short interruption up 0.5 s as described in Figures 4–7. The scheme assists in analyzing the impact of peak current in the stator so that a proper protection philosophy can be considered.
Testing of low-voltage ride through capability compliance of wind turbines – a review
Published in International Journal of Ambient Energy, 2018
Rini Ann Jerin A, Palanisamy Kaliannan, Umashankar Subramaniam
A steady rise in the grid integration of wind power has necessitated new requirements in the grid codes to maintain the stability of the grid. Therefore, stringent grid codes for low-voltage ride through (LVRT) capability is proposed for maintaining the operation of wind turbines during voltage sag condition without tripping (Krause 2011). The LVRT requirement varies with each country, based on the requirements of Transmission System Operators. LVRT is a prominent aspect in the field of wind energy research and is carried out under the classification of grid code revision, LVRT solutions and LVRT testing tools (Jauch et al. 2007). Testing of the LVRT capability of wind turbines is pivotal for wind turbine manufacturers, to establish the credibility of the LVRT capability of the wind generator or wind farm. But the research with respect to LVRT testing tools is not focused effectively so far. Several solutions are proposed for LVRT capability with respect to turbine type, but the actual working and the implications with respect to the grid conditions of the respective installation need to be tested and verified before implementation. Therefore, LVRT testing is quite essential before confirming the viability of the proposed solution (Rodríguez et al. 2002).
Harmonic Level Minimization Using Neuro–Fuzzy-Based SVPWM
Published in IETE Journal of Research, 2018
Bhanu Ponnapalli, Pappa Natarajan
The DFIG system is highly vulnerable to grid faults which are not able to ride through and such problem is called as Fault Ride-through (FRT) problem. The introduction of grid faults in DFIG causes the high-voltage dip (due to overcurrent) that leads to damage in static and rotor windings. The suitable parameter selection of DFIG plays the major role in the reduction of power fluctuations and enhancement of power transfer capability. The grid connection with the wind turbine generators based on Low Voltage Ride-through (LVRT) capability suppresses the power fluctuations effectively. The solutions to the enhancement of LVRT are divided into two categories, namely hardware and software solutions. Crowbar circuits, DC-link choppers, grid-side converters, and voltage restorers are examples of hardware solutions. Under severe grid fault conditions, the provision of control strategies to enhance the LVRT capability falls into the software solutions. The insertion of Superconducting Coil (SC) with the optimization techniques supports the FRT capability improvement effectively. The simultaneous tuning of an inductance of the SC, the initial energy in the SC, and the control parameters of the DC–DC converters achieve the power fluctuations. The regulation of DC quantities by using the PI-controlling technique suffers from steady state error. The dynamic changes in load makes the operation of PI system to fail. The compensation against the lower order harmonics offers significant improvement alternate to PI controllers.