DC-Bus Voltage Range Extension in 1500 V Photovoltaic Inverters

• Published in: IEEE journal of emerging and selected topics in power electronics Vol. 3; no. 4; pp. 901 - 917
• Main Authors: Serban, Emanuel, Ordonez, Martin, Pondiche, Cosmin
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.12.2015; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 1000V and 1500V PV systems; Arrays; Control systems; DC-bus voltage utilization; Inverters; Modulation; Motors; Temperature distribution; Third-harmonic zero-sequence; Three phase modulation; Voltage control; third-harmonic zero-sequence (3H-ZS); 1000 and 1500 V PV systems; dc-bus voltage utilization; three-phase modulation
• ISSN: 2168-6777; 2168-6785
• DOI: 10.1109/JESTPE.2015.2445735

Solar plants based on single-stage conversion photovoltaic (PV) inverters (no dc-dc boost stage) have gained popularity due to their simplicity, high efficiency, and cost effectiveness. Existing PV plants mostly operate under 1000 V and are subject to wide dc-bus voltage variations due to the effect of PV cell temperature and the voltage of the maximum power point (well below the open-circuit voltage). In particular, attractive locations, such as U.S.-Canada mountain and central regions, are subject to extreme PV surface temperatures, making the dc-bus voltage variation a challenge for single-stage solar inverters. This paper investigates 1500 V solar inverters with a focus on dc-bus voltage range extension capabilities through novel modulation and power devices utilization. A comparative analysis with the existing 1000 V solar inverters is presented to illustrate the significant advantages of the wide dc-bus range in 1500 V systems. A lower voltage limit in the dc-bus is achieved by employing a novel voltage reactive power dc-bus control strategy and modified modulation. A higher dc-bus peak voltage is obtained by maximizing the use of power switches. As a result, the 1500 V inverter dc-bus voltage is significantly extended to capture energy under extreme PV surface temperatures, greatly improving the limited range of traditional 1000 V inverters. Simulations and experimental results using a three-phase three-level neutral point-clamped inverter level are presented to validate the proposed dc-bus extension range, control strategy, and modulation scheme.