On-line monitoring of winding insulation health using high frequency common mode voltage from PWM

Partial discharge (PD) testing has been used for over 60 years primarily as a method to assess condition of the stator winding insulation in motors and generators rated 6 kV and above. More recently it has also been used by some machine manufacturers as a means of assuring the quality of the insulation on single winding elements (coils and bars). Although both on-line and off-line tests mainly use a high voltage capacitor to detect the PD, the PD measuring systems in use work either in the low frequency (LF) regime (less than about 1 MHz) or in the very high frequency (VHF) (30-300 MHz) range. By reference to several international standards, published work as well as some experiments described in this contribution, the advantages and disadvantages of the two approaches are compared. Based on this work, it is now clear that off-line PD tests should be done in the LF range. For on-line tests, either method may be used, but use of the VHF method has become more widespread with machine end users, since the owners themselves can perform and interpret the results with a relatively low risk of false indications.

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A High-Frequency Link Single-Stage PWM Inverter With Common-Mode Voltage Suppression and Source-Based Commutation of Leakage Energy

IEEE Transactions on Power Electronics ◽

10.1109/tpel.2013.2280600 ◽

2014 ◽

Vol 29 (8) ◽

pp. 3907-3918 ◽

Cited By ~ 45

Author(s):

Kaushik Basu ◽

Ned Mohan

Keyword(s):

High Frequency ◽

Single Stage ◽

Common Mode ◽

Pwm Inverter ◽

Common Mode Voltage

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Common-Mode Voltage Analysis and Reduction for the Quasi-Z-Source Inverter with a Split Inductor

Applied Sciences ◽

10.3390/app10238713 ◽

2020 ◽

Vol 10 (23) ◽

pp. 8713

Author(s):

Wenjie Liu ◽

Yongheng Yang ◽

Tamas Kerekes ◽

Elizaveta Liivik ◽

Dmitri Vinnikov ◽

...

Keyword(s):

High Frequency ◽

Experimental Tests ◽

Voltage Source ◽

Leakage Currents ◽

Common Mode ◽

Pv Systems ◽

Common Mode Voltage ◽

Reduction Strategies ◽

Frequency Components ◽

Converter Topology

In transformerless grid-connected photovoltaic (PV) systems, leakage currents should be properly addressed. The voltage fluctuations between the neutral point of the grid and the PV array, i.e., common-mode voltage (CMV), will affect the value of the leakage currents. Therefore, the leakage currents can be attenuated through proper control of the CMV. The CMV depends on the converter topology and the modulation strategy. For the quasi-Z-source inverter (qZSI), the amplitude of the high-frequency components in the CMV increases due to the extra shoot-through (ST) state. The CMV reduction strategies for the conventional voltage source inverter (VSI) should be modified when applied to the qZSI. In this paper, an input-split-inductor qZSI is introduced to reduce the CMV, in which all the CMV reduction strategies for the VSI can be used directly with appropriate ST state insertion. Moreover, the proposed method can be extended to impedance source converters with a similar structure. Simulations and experimental tests demonstrate the effectiveness of the proposed strategy for the qZSI in terms of CMV reduction.

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Common-Mode Reduction SVPWM for Three-Phase Motor Fed by Two-Level Voltage Source Inverter

Energies ◽

10.3390/en13153884 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3884

Author(s):

Jian Zheng ◽

Mingcheng Lyu ◽

Shengqing Li ◽

Qiwu Luo ◽

Keyuan Huang

Keyword(s):

High Frequency ◽

Pulse Width ◽

Pulse Width Modulation ◽

Voltage Source ◽

Switching Frequency ◽

Voltage Source Inverter ◽

Large Magnitude ◽

Common Mode ◽

Common Mode Voltage ◽

Three Phase

Aiming at the problem of large magnitude and high frequency of common-mode voltage (CMV) when space vector pulse width modulation (SVPWM) is used in a three-phase motor fed by a two-level voltage source inverter, a common-mode reduction SVPWM (CMRSVPWM) is studied. In this method, six new sectors are obtained by rotating six sectors of conventional SVPWM by 30°. In odd-numbered sectors, only three non-zero vectors with odd subscripts are used for synthesis, while in even-numbered sectors, only three non-zero vectors with even subscripts are used for synthesis. The actuation durations of three non-zero vectors in each switching period in each sector are given. Simulation and experimental results show that, compared with the conventional SVPWM, the CMV magnitude of CMRSVPWM is reduced by 66.67% and the CMV frequency of CMRSVPWM is reduced from the original switching frequency to the triple fundamental frequency. At the same time, the current, torque and speed of the motor are still good.

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