scholarly journals Design Methodology for Three-Phase Four-Wire T-Type Inverter With Neutral Inductor

2021 ◽  
Vol 6 (1) ◽  
pp. 93-105
Author(s):  
Li Zhang ◽  
Keyword(s):  
Resonant Frequency ◽  
Design Methodology ◽  
Neutral Current ◽  
Low Frequency ◽  
Current Loop ◽  
Three Phase ◽  
Zero Sequence ◽  
Resonant Controller ◽  
Zero Sequence Voltage ◽  
Unbalanced Loads

Three-level (3L) converters have been widely used in industry for decades. Compared to the three-phase-three-wire (3P3W) 3L inverter, the three-phase-four-wire (3P4W) one is able to supply the unbalanced loads but has to afford much larger filter inductors because the neutral wire provides a path for high-switching zero-sequence currents. To save filter inductances, a neutral inductor is proposed to insert in the neutral wire. Meanwhile, a complete design methodology is put forward to design the filter inductors and the neutral inductor. With low-frequency zero-sequence currents flowing through the neutral wire, the three-phase load voltages might become unbalanced and/or distorted. To improve the voltage quality, a resonant controller, with the resonant frequency at fundamental output frequency (fo), is presented to add into the zero-sequence voltage loop for balancing load voltages; concurrently, the other resonant controller, with the resonant frequency at 3fo, is presented to insert in the zero-sequence voltage loop or neutral current loop for mitigating voltage distortion. Finally, all of the proposed works are verified on a 3P4W T-type inverter.

Zero-Sequence Circulating Current Reduction for Three-Phase Three-Level Modular Photovoltaic Grid-Connected System

2013 ◽  
Vol 339 ◽  
pp. 539-544
Author(s):  
Fu Sheng Wang ◽  
Xiao Fei Wang ◽  
Zhang Ping Shao ◽  
Xing Zhang
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Component ◽  
Equivalent Model ◽  
High Frequency Component ◽  
Circulating Current ◽  
Three Phase ◽  
Zero Sequence ◽  
Reduction Methods ◽  
Current Reduction

An equivalent model is established for zero-sequence circulating current (ZSCC) in three-phase three-level modular photovoltaic grid-connected system, and ZSCC is classified by frequency into high-frequency and low-frequency components. A parallel solution based on improved LCL filter is proposed to reduce high frequency component of ZSCC, and the low-frequency component of ZSCC can be reduced by using the ZSCC controller. The ZSCC model analysis and reduction methods are verified by experimental results based on a 10 kW three-phase three-level modular photovoltaic grid-connected system.

Towards a transformer transient model as a lumped-distributed parameter system

2017 ◽  
Vol 36 (3) ◽  
pp. 741-750 ◽  
Author(s):  
Sergey E. Zirka ◽  
Yuriy I. Moroz ◽  
Ebrahim Rahimpour
Keyword(s):  
Power Transformer ◽  
Low Frequency ◽  
Fortran Program ◽  
Transient Model ◽  
Content Type ◽  
Voltage Range ◽  
Three Phase ◽  
Wide Range ◽  
Loss Prediction ◽  
Zero Sequence

Purpose The purpose of this study is to develop a topological model of a three-phase, three-limb transformer for low-frequency transients. The processes in the core limbs and yokes are reproduced individually by means of a dynamic hysteresis model (DHM). A method of accounting for the transformer tank with vertical magnetic shunts at the tank walls is proposed and tested on a 120 MVA power transformer. Design/methodology/approach The model proposed has been implemented independently in a dedicated Fortran program and in the graphical pre-processor ATPDraw to the ATP version of the electromagnetic transient program. Findings It was found that the loss prediction in a wide range of terminal voltages can only be achieved using a DHM with variable excess field component. The zero sequence properties of the transformer can be accurately reproduced by a duality-derived model with Cauer circuits representing tank wall sections (belts). Research limitations/implications In its present form, the model proposed is suitable for low-frequency studies. Its usage in the case when transformer capacitances are involved should be studied additionally. Practical/implications The presented model can be used either as an independent tool or serve as a reference for subsequent simplifications. Social/implications The model proposed is aimed at meeting the needs of electrical engineering and ecology-minded customers. Originality/value Till date, there were no experimental data on zero-sequence behavior of three-phase, three-limb transformer with vertical magnetic shunts, so no verified transient model existed. The model proposed is probably the first that matched this behavior and reproduced measured no-load losses for a wide voltage range.

Method for determining the zero-sequence voltage of a three-phase network with error correction

2020 ◽  
Vol 0 (1) ◽  
pp. 17-23
Author(s):  
Анатолій Андрійович Щерба ◽  
Дмитро Костянтинович Маков ◽  
Валерій Іванович Чибеліс
Keyword(s):  
Error Correction ◽  
Three Phase ◽  
Zero Sequence ◽  
Zero Sequence Voltage

scholarly journals Unbalanced and Reactive Currents Compensation in Three-Phase Four-Wire Sinusoidal Power Systems

2020 ◽  
Vol 10 (5) ◽  
pp. 1764 ◽  
Author(s):  
Rafael Montoya-Mira ◽  
Pedro A. Blasco ◽  
José M. Diez ◽  
Rafael Montoya ◽  
Miguel J. Reig
Keyword(s):  
Power Systems ◽  
Positive Sequence ◽  
Electrical System ◽  
System A ◽  
Compensation Methods ◽  
Three Phase ◽  
Zero Sequence ◽  
Unbalanced Loads ◽  
Wire System

In an unbalanced linear three-phase electrical system, there are inefficient powers that increase the apparent power supplied by the network, line losses, machine malfunctions, etc. These inefficiencies are mainly due to the use of unbalanced loads. Unlike a three-wire unbalanced system, a four-wire system has zero sequence currents that circulate through the neutral wire and can be compensated by means of compensation equipment, which prevents it from being delivered by the network. To design a compensator that works with unbalanced voltages, it is necessary to consider the interactions between it and the other compensators used to compensate for negative-sequence currents and positive-sequence reactive currents. In this paper, through passive compensation, a new method is proposed to develop the zero sequence current compensation equipment. The method does not require iteration algorithms and is valid for unbalanced voltages. In addition, the interactions between all compensators are analyzed, and the necessary modifications in the calculations are proposed to obtain a total compensation. To facilitate the application of the method and demonstrate its validity, a case study is developed from a three-phase linear four-wire system with unbalanced voltages and loads. The results obtained are compared with other compensation methods that also use passive elements.

scholarly journals On-Line Detection of Voltage Transformer Insulation Defects Using the Low-Frequency Oscillation Amplitude and Duration of a Zero Sequence Voltage

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 619 ◽  
Author(s):  
Hongwen Liu ◽  
Ke Wang ◽  
Qing Yang ◽  
Lu Yin ◽  
Jisheng Huang
Keyword(s):  
Low Frequency ◽  
Line Detection ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Voltage Transformer ◽  
Transformer Winding ◽  
Zero Sequence ◽  
On Line ◽  
Zero Sequence Voltage ◽  
Winding Insulation

The insulation degradation of a voltage transformer winding is not easy to find, but it may ultimately cause the transformer to explode, leading to accidents such as phase-to-phase short circuits. At present, power transformers, lightning arresters, and other equipment have on-line methods to detect the insulation state. However, there is no mature method for the on-line monitoring of voltage transformer winding insulation. In this study, a small current disturbance method based on a zero-sequence loop is proposed. The characteristic parameters of the low-frequency oscillation of zero-sequence voltage after a disturbance are used to evaluate the insulation state of the winding and detect faults. Theoretical modeling, simulation tests, and field tests show that when the insulation resistance of the voltage transformer winding is in the range 0–40 kΩ, a low frequency oscillation of about 10 Hz can be detected on the zero-sequence voltage, and its amplitude and duration are proportional to the degree of damage to the insulation. This can hence be used as a criterion for the on-line detection of voltage transformer winding insulation defects.

Sign in / Sign up

Export Citation Format

Share Document