Photovoltaic medium-voltage connection module

Medium-voltage connection modules enable large-scale PV systems to efficiently connect to the grid, reducing cable requirements and improving system scalability.OverviewPhotovoltaic (PV) medium-voltage (MV) connection modules are designed to link PV arrays directly to medium-voltage grids, typically above 1 kV AC or DC. By increasing the system voltage, these modules allow higher power transmission with smaller conductor cross-sections, reducing material costs and installation complexity while enabling larger PV subsystems (up to 10–12 MVA per transformer) compared to low-voltage systems (3–5 MVA) (Fraunhofer ISE) .Key ComponentsMedium-Voltage String Inverters MV string inverters convert DC from PV strings to AC at medium voltage levels. Recent developments include 1.5 kV AC inverters and pilot 3 kV DC systems, using high-blocking silicon carbide (SiC) semiconductors for high efficiency and compact design .MVDC Networks and Converters For distributed or remote PV installations, medium-voltage DC (MVDC) networks are used. These networks employ DC/DC converters and DC solid-state transformers (DCSST) to connect low-voltage PV strings to MVDC collection systems. They integrate maximum power point tracking (MPPT) and provide galvanic isolation via high-frequency transformers .Multilevel Converters Cascaded H-Bridge Multilevel Converters (CHB-MLC) are commonly used for MV grid connection. They offer low total harmonic distortion (THD), high voltage operation, and can supply three-phase loads from multiple DC sources. Isolation is achieved using multi-winding high-frequency transformers, which also reduce DC voltage ripples and improve power quality .Protection and Switching Devices Medium-voltage modules include surge protection devices, switch-disconnectors, and insulation monitoring systems to ensure safe operation under overvoltage, lightning strikes, or network disturbances. Compact designs allow integration into string combiner boxes or inverter stations .AdvantagesReduced Cable Requirements: Doubling voltage can reduce conductor cross-section by ~75%, lowering copper and aluminum usage and installation costs .Higher Power Density: Fewer transformers and switchgear are needed for the same plant capacity, freeing space for additional PV modules .Scalability: Medium-voltage modules support larger PV subsystems and long-distance collection networks, suitable for linear or agro-PV installations .Economic and Environmental Benefits: Reduced material use and installation effort improve project economics and lower CO2 emissions associated with aluminum and copper production .ApplicationsMedium-voltage connection modules are particularly suited for:Large-scale PV power plants (>50 MWp)Distributed PV systems with long collector networksPilot projects testing 3 kV string inverters and MVDC networksIntegration into hybrid or dual-purpose PV installations along roads, dikes, or agricultural land .Future OutlookOngoing projects like PVgoesMV and MS-LeiKra demonstrate the technical feasibility of MV PV systems and contribute to standardization efforts. As raw material constraints and grid integration challenges grow, medium-voltage PV modules are expected to become a standard solution for cost-effective, high-capacity solar power plants .