Abstract
General pulse width modulation (PWM) model for multi-phase neutral point (NP) clamped (NPC) 3-level inverter (3LI) is described. A novel PWM strategy for $N$ -phase NPC 3LI with unconditional NP voltage balance is proposed as well as its carrier-based realization, in which PWM sequences are generated by comparing a single carrier wave with double modulation waves. The proposed PWM strategy is consistent with the principle of virtual space vector PWM (VSVPWM). However, the mechanism of NP voltage balance under the proposed PWM strategy is based on precisely calculating and executing level 1 action time of each phase, which may be influenced by some non-ideal factors. To avoid that, an active NP voltage control for the proposed PWM strategy is put forward. Then 3-phase and 5-phase NPC 3LIs are built as examples to verify the correctness of the proposed PWM strategy. Finally, the experimental results indicate that the proposed PWM strategy has better NP voltage control abilities.
Highlights
In recent years, researchers have been paying increasingly attentions to multi-level inverters [1], which have a lot of merits
To perfectly control neutral point (NP) voltage like virtual space vector PWM (VSVPWM), a novel carrier-based pulse width modulation (PWM) strategy is proposed in this paper, which can be extended to N -phase NPC 3-level inverter (3LI)
This paper presents a novel PWM strategy for N -phase neutral point clamped 3-level inverter (NPC 3LI) with unconditional NP voltage balance and its carrierbased realization
Summary
Researchers have been paying increasingly attentions to multi-level inverters [1], which have a lot of merits. Jiang et al.: Carrier-Based PWM Strategy Providing NP Voltage Oscillation Elimination for Multi-Phase NPC 3LI modulation wave It can realize pre-compensation for an unbalanced NP voltage condition. To perfectly control NP voltage like VSVPWM, a novel carrier-based PWM strategy is proposed in this paper, which can be extended to N -phase NPC 3LI. 1. A PWM strategy suitable for N -phase NPC 3LI is proposed, which can achieve NP voltage balance unconditionally under any modulation index and power factor. Active NP voltage control method can be realized by this approach, but it is complex to analyze the total compensation current Another approach is adjusting the duty ratios of level 1 of these phases corresponding to u2. Small DC-link capacitor can be used, such as film capacitor with a long life span
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