Sungrow’s 1500VDC, 3-phase, PV grid-connected string inverter is an integral piece of the PV power system. These inverters convert the direct current (DC) power, that has been generated from the PV modules, into grid-compatible, AC current before supplying output to the utility grid. It’s revolutionary design substantially reduces installation time and balance-of-system costs, for utility-scale PV systems. The SG125HV, packs an impressive 125kW of capacity into a transformer-less cabinet, which weighs a mere 76kg. As opposed to a transformer, the inverter relies on integrated circuits (ICs), in order to meet regulatory standards for safety, and to attain a high-level of performance with a very small footprint.
The SG125HV comes with Sungrow’s patented, five-level, topology design, which enables the inverter to boost the maximum efficiency to over 98.9%. Replacing the transformer with integrated circuitry also eliminates the need for AC combiner-boxes. The 5MW PV power-block design further reduces AC transformer and labor costs. DC side cabling costs, in many installations, are also cut significantly.
Teardown: Sungrow SG125HV
- Full-power operation with no degradation at 50 ℃
- DC 1500V, AC 600V – provides a low, initial investment option
- 1 to 5 MW power-block design for lower AC transformer and labor cost
- Max. DC/AC ratio up to 1.5
- Virtual central concept, easy for O&M work
- Compact design and lightweight for easy installation
- Compliance with both IEC and UL safety, EMC and grid support regulations
- Low/High voltage ride through (L/HVRT)
- Active & reactive power control and power ramp rate control
- Automated output-derating guards against overload or potential faults
External and Enclosure
- Size 670 x 902 x 296 mm and weight 76 kg
- Protection Class IP65 NEMA 4X
- Operating ambient temperature from -25°C to 60°C
Functional Block Diagram
- PWM Microcontroller: TI TMS320F280230PT Piccolo Microcontrollers. High efficiency 50MHz 32-Bit CPU with 10-bit references analog comparators to control the PWM outputs.
- Digital Signal Processing: TI TMS320F2837 Dual-Core DelfinoTM Microcontroller. 32-bit floating-point microcontroller unit (MCU) designed for advanced closed-loop control applications, sensing and signal processing.
- Programmable Logic Device (PLD): Lattice LCMXO2-2000HC. 2.5V/3.5V Field Programmable Gate Array with 2112 Look-Up tables (LUT) and 79 I/Os.
DC Input and AC Output Switches
- Surge Protector: Parafoudre DS50VGPV-1500G/51. Type 2, 1500 VDC max. surge protector for photovoltaic.
- Photovoltaic Switch Disconnectors: Eaton NZM 2 N2-4-250-S15-DC. Switch-disconnectors for 1500VDC for two-pole switching with 250A rated operational current.
- Gate Driver: Broadcom (Avago Technologies) ACNT-H313 (2pcs for booster stage). 2.5A output current IGBT gate drive optocoupler in 15mm Stretched SO8 Package.
- AC Switch: MERZ ML3-125-E-1851. 125A rated uninterrupted current 45kW open type emergency-off switches.
- AC EMI Filter: LST762
DC EMI Filter
- Current Transducer: LEM LA 200-P. 200A and 3kV insulation closed-loop hall effect current transducer.
- Reed Relay: Meder Electronic KT05-1A. 5V coil voltage, 80ohm, 1000V switching voltage 1 Form A contact reed relay.
- SiC MOSFET: CREE C2M1000170D (2pcs for booster stage). 1700V, 5A, 1ohm C2MTM N-channel enhancement mode Silicon Carbide power MOSFET.
- Phototransistor: Vishay CNY66B (2pcs). 1450Vpk very high-isolation voltage phototransistor in 700mil DIP4 package.
- Rectifier: ST STTH6003CW (2pcs). 300V, 2x 30A dual high frequency secondary rectifier.
- Inverter: Infineon F5L200R12N2H3 (3pcs for 3-phase inverter stage). 1200V/200A IGBT module with active five-level topology.
- DC-Link: Faratronic C3D (4pcs). 900VDC, 40µF low building height DC-link metal film capacitor.
Current Sensor: Broadcom (Avago Technologies) ACNT-H79A (3pcs). ±1% gain tolerance Optical isolation amplifier in in 15mm Stretched SO8 Package.
- Snubber: Faratronic C3H (6pcs). 850VDC, 3µF IGBT snubber capacitor.
- DC-Link: Faratronic C3N (3pcs). 600VDC, 250µF DC-link capacitor.
- Gate Driver: Broadcom (Avago Technologies) ACNT-H313 (24pcs for 3-phase inverter stage). 2.5A output current IGBT gate drive optocoupler in 15mm Stretched SO8 Package.
DC Bus, AC Filter and AC Relays
- AC Filter: Faratronic C6A (12pcs). 440VAC, 10µF metalized polypropylene film AC filter capacitor.
- Interference Suppression: Faratronic MKP65 (6pcs). 440VAC 1µF metalized polypropylene interference suppression capacitor.
- AC Relay: Song Chuan 511XP1-1AH-F-C-12VDC (6pcs). 690VAC 160A, Form 1A SPDM contact PCB terminal AC Relay.
- Current Transducer: LEM LA 200-P (3pcs). 200A and 3kV insulation, closed-loop hall effect current transducer.
- Leakage Current Transducer: LEM CTSR 1.5-TP/SP18. 1.5A leakage current transducer with galvanic separation, between primary and secondary circuits.
Sungrow has really upped the game with the SG125HV. Reduced installation and maintenance costs, superior efficiency, and very tight controls, coupled with the inherent reliability of ICs make a very strong case for the SG125HV. Comprehensive data storage of routine and faults serve to document that strong case, once online. While real estate is not typically a concern in these systems, the compact design still makes for a cleaner and simpler circuit, which is easier to service. Any engineer, tasked with designing a large-scale PV installation, should certainly consider this inverter, for the project.