Single-phase Neutral Point Clamped Research Articles

CBPWM and SVPWM equivalent relationship on single‐phase NPC N ‐level inverters with arbitrary sequence

Single-phase multilevel neutral-point-clamped (NPC) voltage source inverter has been widely applied in AC traction drive system, the carrier-based pulse width modulation (CBPWM) method and the space vector pulse width modulation (SVPWM) method are mainly two modulation methods for single-phase NPC multilevel converters, and there is a certain relationship between these two modulation strategies. In this study, the unified relationship between SVPWM and CBPWM in single-phase three-level and five-level NPC has been analysed. Then by injecting the zero-sequence component into the initial modulation wave, the same switching state and output current as SVPWM can be achieved through modulation waves decomposed under the CBPWM strategy. Finally, the unified theory of SVPWM and CBPWM in an N-level inverter with an arbitrary number of segments sequence was deduced. The simulation and experimental results illustrate that the unified theory between CBPWM and SVPWM is correct. With the zero-sequence injected, CBPWM can realise the same effect as SVPWM, but the former is simpler than the latter, which is easy to promote for higher-level applications.

Simulation of Single Phase 3-level Z-source NPC Inverter with PV System

This paper elucidates simulation of single phase 3-level z-source neutral point clamped (NPC) inverter with PV system. single phase NPC inverter employed due to its advantages like less voltage stress, reduced harmonic content, minimsed CMV and voltage stress is low. Z-source network is engaged to boost input voltage getting from the photovoltaic system, which is manoeuvre in shoot through and non-shoot through conditions. This proposed scheme utilized to enhance the output voltage, minimise THD and the leakage current can be avoided with help of split inductor connected with output of inverter system. sinusiodal pulse width modulation (SPWM) used as control technique for the proposed 3-level z-source NPC inverter. The simulation results of this scheme has been verified using matlab/simulink.

Harmonic Analysis of Single-Phase Neutral-Point-Clamped Cascaded Inverter in Advanced Traction Power Supply System Based on the Big Triangular Carrier Equivalence Method

An advanced traction power supply system based on a single phase neutral-point-clamped (NPC) cascaded inverter is studied. The big triangular carrier equivalence method in double coordinate system is proposed, which can reduce one coordinate system, thus simplifying the calculation. Based on the big triangular carrier equivalence method, the harmonic characteristics of a single phase NPC cascaded inverter are calculated by double Fourier transform and voltage harmonics expressions of 5-level, 9-level and 13-level output waveforms are derived. Finally, the performance and calculated results of the proposed method were verified by simulations and experiments. The result provides a theoretical basis for further studies on traction network resonance.

Implementation of Active NPC Circuits in Transformer-Less Single-Phase Inverter With Low Leakage Current

Transformer-less grid-connected photovoltaic (PV) systems face the challenge of keeping low leakage current due to their nonisolation configurations. To better attenuate the leakage current in the single-phase systems, a few neutral-point-clamped (NPC) topologies have been proposed. This paper further proposes an active NPC method by only employing one additional switch to connect the midpoint dc link and the freewheeling circuit of traditional single-phase PV inverters. After exploring the operational principles of freewheeling circuits, the construction method and the implementation of active NPC circuits in transformer-less single-phase inverters are elaborated in detail. Since only the leakage current flows through the additional NPC switch, the presented single-phase NPC inverters could still maintain the high operational efficiency with the further attenuated leakage current. The experimental results verified the theoretical findings.

Design and analysis of an LC trap/LCR output filter for a single-phase NPC three-level inverter

This article presents a filter design approach and the efficiency analysis of a single-phase Neutral Point Clamped (NPC) three-level inverter with a combined LC trap and LCR filter system. The multilevel inverter system using NPC type inverter is suitable for high-power application. The single-phase NPC three-level inverter operates normally at low switching frequency. The proposed LC trap filter is comprised of a conventional LCR output filter. By adding an LC trap filter, the need for a low-value damping resistor and low LC cut-off frequency is eliminated. Use of the high-value damping resistor increases the efficiency of the output filter system. The controller used is DSP (TMS320C31). The effectiveness of the proposed system is verified by SPICE simulation and experimental results.