Voltage Balancing Control of Three-Level Active NPC Converter Using SHE-PWM

Abstract

This paper presents a neutral point voltage control strategy for the three-level active neutral point clamped (ANPC) converter using selective harmonic elimination pulsewidth modulation (SHE-PWM). The control strategy introduces a small change in the switching angles, which varies the duty cycle of the zero-level switching state, controls the neutral point current and, therefore, the neutral point voltage. The decision to vary a given switching angle takes into account the polarity of the output currents and the voltage across the lower dc-link capacitor. The effectiveness of the proposed strategy is verified through extensive simulation studies and experimentally validated using a low power laboratory prototype. Index Terms-Active neutral point clamped converter (ANPC), neutral point voltage control, pulse-width modulation (PWM), selective harmonic elimination (SHE).

Modified Unipolar Carrier-Based PWM Strategy for Three-Level Neutral-Point-Clamped Voltage Source Inverters

“…In recent year, several modulation strategies for a threelevel NPC VSI have been developed [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. They could be mainly classified into carrier-based pulsewidth modulation (CB-PWM) [11][12][13][14][15][16][17][18], space vector modulation (SVM) [19][20][21][22][23][24][25][26], and selective harmonic elimination (SHE) [27][28][29][30].…”

“…They could be mainly classified into carrier-based pulsewidth modulation (CB-PWM) [11][12][13][14][15][16][17][18], space vector modulation (SVM) [19][20][21][22][23][24][25][26], and selective harmonic elimination (SHE) [27][28][29][30]. Among these PWM strategies, the CB-PWM has probably been the most popular due to its simplicity of implementation, which based on the comparison between the modulation reference signals and two triangular carriers.…”

Neutral-Point Voltage Balancing Method for Three-Level Inverter Systems with a Time-Offset Estimation Scheme

“…However, they are not cost-effective because they require additional hardware. Other approaches were proposed in [15]- [17]. However, their use is limited.…”

High-Performance Motor Drives

“…A well documented problem presented in this converter is the unbalance of the capacitors produced by asymmetries in the converter hardware and mainly the operational conditions [15]. Several strategies to deal with this problem have been proposed, mainly focused to modify the modulation strategy [16] [17]. Another issue of this converter is the unequal distribution of losses, which causes that the outer switches switching losses differ from the central ones, depending on the operation condition.…”

“…Another issue of this converter is the unequal distribution of losses, which causes that the outer switches switching losses differ from the central ones, depending on the operation condition. This problem cannot be easily addressed using the conventional scheme and modified topologies like active neutral point clamped (ANPC) have been proposed [16]. In this converter, the clamping diodes are replaced by controlled switches, then selecting the appropriate combination of switches it is possible to reduce and equally distribute the losses.…”