DC magnetisation of transformers

Ahfock, A.; Hewitt, Andrew

doi:10.1049/ip-epa:20050440

Cited by 16 publications

(6 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This technique was introduced by the author which give a brief about the DC offset which is already known as before, as the excessive injection of DC into AC can prompt issues such as corrosion in underground equipment [29], transformer magnetizing current distortion and transformer saturation [30] and failure in the function of the protective equipment [31]. In this manner rules and measures have been set up to control the DC injection [32].…”

Section: Differential Amplifiermentioning

confidence: 99%

“…The transformer operating point can be shifted by small amount of DC current, which increases the RMS magnetizing current and causes additional winding losses [43], [44], [45]. This increase in the primary current leads to an overheat for the winding of the transformer and trip the input protection that leads to a reduction in the lifetime of the transformer [30].…”

Section: New Approach Using DC Link Current Sensorsmentioning

confidence: 99%

See 1 more Smart Citation

Review of DC Offset Compensation Techniques for Grid Connected Inverters

Elghareeb

El-Refaey

Moussa

et al. 2018

IJPEDS

View full text Add to dashboard Cite

<p><strong></strong>Limitations of DC injection into the AC network is an important operational requirement for grid connected photovoltaic systems. There is one way to ensure that this issue needs a power transformer as a connection to the AC network. However, this solution adds cost, volume, mass, and power losses. Ideally there shouldn't be any DC at the output of the inverter, but practically, a small amount of DC current is present. Therefore, in this paper there are techniques for the DC offset elimination are proposed. Some have drawbacks which was treated by another technique. Also there are best solutions for eliminating DC offset as in section 17, and 18 as it explains how to reduce the DC offset in a transformerless operation with reducing the power losses, mass and the cost effect.</p>

show abstract

Section: Differential Amplifiermentioning

confidence: 99%

Section: New Approach Using DC Link Current Sensorsmentioning

confidence: 99%

Review of DC Offset Compensation Techniques for Grid Connected Inverters

Elghareeb

El-Refaey

Moussa

et al. 2018

IJPEDS

View full text Add to dashboard Cite

show abstract

“…DC injection of grid connected power converters is caused by the delay mismatch in gating circuits and imperfections of power switches [12], by the offset in current sensing [13], by DC injection based methods for detecting the stator resistance and temperature in grid-connected AC machines [14], while other sources of DC bias include geomagnetic induced currents [15], HVDC transmission, railway signalling equipment and similar. Even a small DC bias may result in saturation of power transformers [16], an increase in their iron losses, increased corrosion and erroneous operation of measurement and protective equipment. Relevant norms [11] prescribe the DC injection limit as 0.5% of the grid-connected power converter rated current.…”

Section: Introductionmentioning

confidence: 99%

Detection and suppression of parasitic DC voltages in 400V AC grids

Vukosavic¹

2015

FACTA U EE

View full text Add to dashboard Cite

Grid connected static power converters inject parasitic DC currents due to the offset in current sensing, control imperfections, asymmetries in power switches and other secondary effects. Ever growing number of grid connected converters contributes to an increase of DC bias in AC grids, and this brings the cores of distribution transformers closer to saturation and increases their power losses. This paper provides sensitivity analysis of distribution transformers to the DC bias, and considers solutions for detecting and compensating the parasitic DC components in AC grids. Active compensation methods can be advantageously used in suppressing the DC bias at grid connection point of the power converter. The sensing approach proposed in this paper makes use of saturable ferromagnetic cores and a low cost DSP for signal analysis and processing. Proposed algorithm uses distortion of the magnetizing current of a parallel connected saturable core due to the bias. Experimental results demonstrate the capability for detecting and compensating the bias voltages far below 1 mV in 0.4 kV grids. The paper describes the principles of DC bias detection and it provides the guidelines for the proper design of magnetic components. High precision of the proposed DC bias sensing is thoroughly verified on the experimental setup connected to a 0.4 kV grid.

show abstract

“…Ideally the output current of the inverter will be purely AC, but in practice, unless special measures are taken, it will contain a small amount of DC. Injection of DC into the AC mains, if excessive, can lead to problems such as corrosion in underground equipment [1], transformer saturation and transformer magnetising current distortion [2] and malfunction of protective equipment [3]. Therefore guidelines and standards have been set up to regulate DC injection [4].…”

Section: Introductionmentioning

confidence: 99%