Hybrid PWM Techniques for a DCM-232 Three-Phase Transformerless Inverter with Reduced Leakage Ground Current

Pulse Width Modulation (PWM) strategies are crucial for controlling DC–AC power converters. In particular, transformerless inverters require specific PWM techniques to improve efficiency and to deal with leakage ground current issues. In this paper, three hybrid PWM methods are proposed for a DCM-232 three-phase topology. These methods are based on the concepts of carrier-based PWM and space vector modulation. Calculations of time intervals for active and null vectors are performed in a conventional way, and the resulting waveforms are compared with a carrier signal. The digital signals obtained are processed using Boolean functions, generating ten signals to control the DCM-232 three-phase inverter. The performance of the three proposed PWM methods is evaluated considering the reduction in leakage ground current and efficiency. The proposed modulation techniques have relevant performances complying with international standards, which make them suitable for transformerless three-phase photovoltaic (PV) inverter markets. To validate the proposed hybrid PWM strategies, numerical simulations and experimental tests were performed.

Method of Locating Ground Fault in Low Resistance Grounding Distribution Network by Grounding Wire Current

Three-core cables are increasingly used in urban distribution networks. The shielding layer, armor layer of the three-core cable and the earthing electrode constitute the earth-electrode network. When a ground fault occurs, a regular ground wire current distribution is formed in the network. This paper analyzes the distribution law of ground current, and according to the distribution law, puts forward a kind of grounding fault location method of neutral point small resistance grounding grid, and finally designs and implements the grounding fault location system.

The resistive ground fault of PWM voltage inverter in the EV charging station

During the direct touch of the inverter output voltage or with the ungrounded shield of the cable connecting the inverter to the motor or other type of load, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 and 16 kHz, flow via a human’s body. Here was proved that Residual Current Device (RCD) ($$I_{\triangle n}$$ I ▵ n = 30 mA) does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter’s voltage is dangerous to health and life. For the authors, the RCD usage in the Voltage Frequency Converters (VFCs) is not a good engineer practice when high-frequency common-mode distortion currents flow through it. The paper presents tests of RCD operation in the event of a resistance ground fault (via human body) during EV battery charging where the PWM voltage inverter is connected to the external rectifier to provide DC charging battery voltage. Finally, the authors propose a method of eliminating common-mode (CM) current from short protection system by using a separate circuit in which the parasitic leakage current omits an RCD.

The Resistive Ground Fault of PWM Voltage Inverter In The EV Charging Station

During the direct touch of the inverter output voltage, the nonsinusoidal ground currents with a basic harmonic frequency between 1.5 kHz and 16 kHz, flow via a human’s body. Here was proved that Residual Current Device (RCD) type AC/IΔn = 30 mA does not switch off the power supply when a ground current with a value of about some hundred milliamps occurs. Because RCDs do not disconnect the power supply, the touch on the inverter’s voltage is dangerous to the health and life. For the authors, RCD usage in Voltage Frequency Converters is not a good engineer practice. The article presents tests of RCD operation in the event of a ground fault during EV battery charging.

Properties: Spectroscopy

This chapter focuses on the spectroscopy of the superconducting state. Various manifestations of macroscopic quantisation are described, including flux quantisation, the Josephson effect, vortices, and the Little–Parks effect. The Ginzburg–Landau theory and its microscopic derivation are presented. An interesting new direction, the search for the lossless ground current state, undergoes an intensive development. If the electronic density of states contains several peaks, it manifests as a multigap structure. Impurity scattering and, especially, the pair-breaking effect can drastically affect the spectrum and lead to gapless superconductivity. Pairing can be induced by the proximity effect (S–N contact). The isotope effect is the signature of the pairing mechanism, but it can be affected by Coulomb terms, magnetic impurities, and polaron formation. The study of fluctuations forms a large area of research. Fluctuations affect the behaviour of heat capacity and nuclear magnetic resonance relaxation, lead to peculiar paraconductivity, and so on.