A Novel Zero Dead-Time PWM Method to Improve the Current Distortion of a Three-Level NPC Inverter

Abstract

This paper proposes a novel pulse width modulation (PWM) for a three-level neutral point clamped (NPC) voltage source inverter (VSI). When the conventional PWM method is used in three-level NPC VSI, dead time is required to prevent a short circuit caused by the operation of complementary devices on the upper and lower arms. However, current distortion is increased because of the dead time and it can also cause a voltage unbalance in the dc-link. To solve this problem, we propose a zero dead-time width modulation (ZDPWM) which does not require dead time used in complementary operation. The proposed technique applies the offset voltage to the space vector pulse width modulation (SVPWM) reference voltage for the same modulation index (MI) as the conventional SVPWM, but any complementary switching operation needs dead time. In addition, the proposed method is divided into four operation sections using the reference voltage and phase current to operate switching devices which flow the current depending on the section. This ZDPWM method is simply implemented by carrier and reference voltage that reduce the current distortion, because complementary operation that needs dead time is not implemented. However, the operation section is delayed due to the sampling delay that occurs during the experiment. Therefore, in this paper, we conduct a modeling of sampling delay to improve the delay of operation section. To verify the principle and feasibility of the proposed ZDPWM method, a simulation and experiment are implemented.

Neutral Point Clamped Transformer-Less Multilevel Converter for Grid-Connected Photovoltaic System

“…and yields the control input u (t) among two hysteresis bands: upper hysteresis bands (UU) and lower hysteresis bands (BL) [28][29][30][31]. Such control input u(t) drives the PWM block to give the perfect interface between inverter and grid.…”

“…The authors in [26] dealt with TNP-MLI for PV application with two separate MPPTs for the DC-Link and investigated conduction loss for the inverter. Some similar structure of T type MLI with different PWM scheme is also discussed in [27][28][29][30]. The NPC-MLI majorly suffered by DC-link capacitors balancing.…”

Enhanced TVI for Grid Forming VSC under Unbalanced Faults

“…Voltage and current transductions along with the ADC are also modelled with an equivalent delay and respective digital filters [21]. In short, the considered system model is related to the OSMOSE WP3 demonstrator [9,22], which has been validated during FATs [23].…”

Optimized Synchronous SPWM Modulation Strategy for Traction Inverters Based on Non-Equally Spaced Carriers

“…With the development of inverter technology, the pulse width modulation strategy is being improved and perfected [1][2][3]. Rail traction inverters often exhibit low switching frequencies, limited to a few hundred hertz, due to constraints on power device switching losses [4][5][6].…”