A Novel Phase Current Reconstruction Method for a Three-Level Neutral Point Clamped Inverter (NPCI) with a Neutral Shunt Resistor

Abstract

This paper presents three phase current reconstruction methods for a three-level neutral point clamped inverter (NPCI) by measuring the voltage of a shunt resistor placed in the neutral point of the inverter. In order to accurately acquire the phase currents from the shunt resister, the dwell time of the active voltage vectors need to exceed the minimum time. On the other hand, if the time of active voltage is shorter than the minimum time, the current measurement becomes impossible. In this paper, unmeasurable regions for current are classified into three areas. Area 1 is a region in which both phase currents can be measure. Therefore, it is not necessary to restore the current. In Area 2, only one phase current can be measured. Thus, an estimation or restoration method is needed to measure another phase current. In this paper, the current estimation method using an electrical model of the motor is proposed. Area 3 is the region in which both phase currents can not be measured. In this case, it is necessary to move the voltage vector to the current measurable area by injecting the voltage. In this paper, Area 3 is divided into 36 sectors to inject optimal voltage. The proposed methods have the advantages of high current measurement accuracy and low THD (total harmonic distortion). The effectiveness of the proposed methods are verified through experimental results.

Experimental Evaluation of the Performance of a Three-Phase Five-Level Cascaded H-Bridge Inverter by Means FPGA-Based Control Board for Grid Connected Applications

“…Novel structures are continuously suggested [24,25] and ways to control them [26][27][28]. Efficiency, dimension, weight, and reliability influence the cost of manufacturing inverters.…”

“…By according the PI integrator time constant T I equal to the plant time constant T I = L T /r T , with the aim to delete the slower plant pole and supposing a perfect pole-zero cancellation, the current closed-loop transfer function W(s) become of the second order Equation (24).…”

Three-Phase Five-Level Cascade Quasi-Switched Boost Inverter

“…The benefits of the multilevel power inverter topologies are as follows: improved output waveforms, low electromagnetic interference (EMI), and small filter size [1][2][3]. Neutral point clamped (NPC), flying capacitors, and cascaded H-bridge (CHB) inverters [4][5][6][7][8][9][10][11][12][13][14] are three basic multilevel inverter structures. Among these structures, the CHB structures [9][10][11][12][13][14] have unique merits: higher output voltage, flexibility, and power levels.…”

Sector Subdivision Based SVPWM Strategy of Neutral-Point-Clamped Three-Level Inverter for Current Ripple Reduction

“…The topology of three-level inverters can be divided into three categories: cascade H-bridge (CHB) [4], flying capacitor (FC) [5], and neutral-point-clamped (NPC) [6]. Among them, NPC three-level inverters are the most widely used in medium-voltage high-power industrial applications, such as traction drive, mine hoister, and wind power generation [7][8][9].…”