This paper presents a novel seven-level inverter topology for medium-voltage high-power applications. It consists of eight active switches and two inner flying-capacitor units forming a similar structure as in a conventional Active Neutral Point Clamped (ANPC) inverter. This unique arrangement reduces the number of active and passive components. A simple modulation technique reduces cost and complexity in the control system design without compromising reactive power capability. In addition, compared to major conventional 7-level inverter topologies such as the Neutral Point Clamped (NPC), Flying Capacitor (FC), Cascaded H-bridge (CHB) and Active NPC (ANPC) topologies, the new topology reduces the dc-link voltage requirement by 50%. This recued dc-link voltage makes the new topology appealing for various industrial applications. Experimental results from a 2.2 kVA prototype are presented to support the theoretical analysis presented in this paper. The prototype demonstrates a conversion efficiency of around 97.2% ± 1% for a wide load range.
- Multilevel Inverter
- 7-level inverter
- Active Neutral Point Clamped (ANPC) inverter
- Flying Capacitor
- Voltage Source Converter
In this paper, a novel eight-switch seven-level Active Neutral Point Clamped inverter is proposed. Modulation techniques are explored and operation under both active and reactive power factor conditions are systematically analyzed. A comparative analysis and a set of design guidelines are presented and followed by simulation and experimental verification. Compared to conventional seven-level inverter topologies, the ANPC inverter topology requires only eight power devices for a single-phase design and halves the dc-link voltage required to produce a given ac voltage output magnitude when compared to similar circuits. For applications such as for a grid-connected PV system, this may help eliminate additional power conversion stages (boost converters) and therefore increase the efficiency and reliability of the system. Further, this reduces the voltage stress on the dc-link capacitor, which reduces the cost and size of the system design. The inverter can operate at any power factor (leading or lagging) without requiring any changes to the modulation scheme. Compared with other seven-level configurations, the performance demonstrated by the new inverter is highly competitive, potentially making it an appropriate topology choice for a wide-range of power conversion applications, e.g. variable-speed drives, electric vehicles (V2G/G2V technologies), grid-connected renewable energy systems.
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