A New Medium Voltage DC Collection Grid for Large Scale PV Power Plants with SiC Devices

In this paper, a new medium voltage DC collection grid method for large-scale PV plants is proposed. An Interleaved Modular Multilevel (IMMC) DC-DC boost converter is proposed in order to enable medium voltage DC power collection grid followed by a central medium voltage class DC-AC inverter for utility interface. The proposed IMMC converter is synthesized with lower voltage half-bridge SiC inverter blocks connected in series to support medium voltage DC conversion. The half-bridge blocks of the IMMC employ SiC switches, along with high frequency PWM operation enable compact size/weight along with high efficiency conversion. Simulation results are shown for 1500V (DC) to 16kV (DC) conversion with four series connected IMMC inverter blocks powered from two PV plants. A power sharing stage is an integral part of the proposed converter. This enable two series connected PV plants to supply unequal power under partial shading conditions. Control of the power sharing stage for varying insolation from PV (1000-500W/m2) due to shading effect is shown. A design example for 1MW PV power plant block based on the specifications derived from Kuwait Shagaya 60MW solar power plant is discussed. Experimental results on scale down laboratory prototype is included in the paper.

[1]  Antonios Marinopoulos,et al.  Comparison of PV systems with maximum DC voltage 1000V and 1500V , 2013, 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC).

[2]  Prasad Enjeti,et al.  Medium voltage AC collection grid for large scale photovoltaic plants based on medium frequency transformers , 2014, 2014 IEEE Energy Conversion Congress and Exposition (ECCE).

[3]  Youguang Guo,et al.  Modular Medium-Voltage Grid-Connected Converter With Improved Switching Techniques for Solar Photovoltaic Systems , 2017, IEEE Transactions on Industrial Electronics.

[4]  Prasad Enjeti,et al.  A new high power density modular multilevel DC-DC converter with localized voltage balancing control for arbitrary number of levels , 2016, 2016 IEEE Applied Power Electronics Conference and Exposition (APEC).

[5]  Oriol Gomis-Bellmunt,et al.  Topologies for large scale photovoltaic power plants , 2016 .

[6]  Prasad Enjeti,et al.  A new Interconnected Modular Multilevel Converter (IMMC) with sinusoidal voltage output suitable for high performance AC drives , 2017, 2017 IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL).

[7]  Martin Ordonez,et al.  DC-Bus Voltage Range Extension in 1500 V Photovoltaic Inverters , 2015, IEEE Journal of Emerging and Selected Topics in Power Electronics.

[8]  Peter W. Lehn,et al.  A Bidirectional Modular Multilevel DC–DC Converter of Triangular Structure , 2015, IEEE Transactions on Power Electronics.

[9]  H. Alan Mantooth,et al.  Next-generation MVDC architecture based on 6.5 kV / 200 A, 12.5 mΩ SiC H-bridge and 10 kV / 240 A, 20 mΩ SiC dual power modules , 2017, 2017 IEEE Electric Ship Technologies Symposium (ESTS).

[10]  S. Alhajraf,et al.  Optimization of the Technology Mix for the Shagaya 2 GW Renewable Energy Park in Kuwait , 2015 .

[11]  Vassilios G. Agelidis,et al.  Performance of Medium-Voltage DC-Bus PV System Architecture Utilizing High-Gain DC–DC Converter , 2015, IEEE Transactions on Sustainable Energy.

[12]  Johann W. Kolar,et al.  Novel high voltage conversion ratio “Rainstick” DC/DC converters , 2013, 2013 IEEE Energy Conversion Congress and Exposition.

[13]  Liming Liu,et al.  Isolated AC–DC Converter Using Medium Frequency Transformer for Off-Shore Wind Turbine DC Collection Grid , 2017, IEEE Transactions on Industrial Electronics.