PV grid-connection system refers to the system that converts solar power to electric power and transmits to the grid. It mainly consists of solar array, PV combiner box, PV grid- connected inverter, metering and control devices, and grid- connection system. The grid-connected inverter is one of the key equipment in the PV grid connection system, and it is responsible for making the highest power output by solar cell panel, also converts the output DC electric energy to AC electric energy and transmits it to the power grid. RW series PV grid-connected inverter consists of advanced IGBT controlled inverter, protection & control equipment and I/O switchgear etc. The system power capacity portion is designed in modularized structure featuring easy extension, convenient installation and maintenance, optimal layout, and less land occupation. The system control portion is based on the professional control & protection platform featuring abundant hardware resources, complete software functions, and flexible configuration of control/operation parameters, to maximally meet the extension demand of system flexibility and extensibility. There are two types of PV grid-connected inverters provided by Rockwill.
• Central inverter: generally used in large-scale power plant.
• String inverter: suitable for small and medium sized rooftop PV power generation system and small ground power station.
• Soft grid-connected control
The control system can accurately control the inverter output voltage in real-time based on the detected grid voltage and eliminate dynamic/static error to realize impulse-free grid-connection.
• Maximum Power Point Tracking (MPPT) control
The system can search the maximum Power Point automatically based on the collected PV cell information, and control the real time tracking of inverter to achieve the maximum power efficiency.
• Dynamic reactive power control and compensation
In case of voltage drop in the grid, the control system can provide automatic reactive power compensation to maintain the grid voltage based on the voltage dip and duration.
• Islanding detection
The system can rapidly detect the occurrence of islanding and handle it according to the preset strategy.
• Low voltage ride through (LVRT) operation
The PCS-9563 inverter can maintain grid-connection operation and realize LVRT in case of low voltage fault in the grid.
• Power quality (PQ) control
The PV inverter is designed with grid-connection power optimization stability to ensure power quality.
• Various operating modes
The PCS-9563 has three working modes—Standby, Run and Stop, two self-check statuses—Normal and Fault, several running control modes—PQ control, voltage frequency control and Low voltage ride through (LVRT) etc., and several auto control logics—Auto run, Auto stop, Emergency stop etc.
• Auto start/stop
The PCS-9563 PV grid-connection inverter is designed with auto grid connection and manual control is not required. The inverter automatically detects the DC/AC system data in standby mode and automatically shifts to 'Run' mode for grid connection when the running conditions are fulfilled. It tracks the PV array Maximum Power Point (MPP) in real-time and maintains the maximum power output during running.
• Auto fault processing
During grid-interconnection operation, the inverter detects the self-operation condition and the status of PV array and AC grid in real-time. Once any fault or abnormal condition is detected in the PV power generating system, the inverter will stop running, send out alarm signals and enter fault emergency stop mode. The detailed fault information will be displayed on the LCD of control devices. The inverter will continuously detect the system status in fault mode and automatically restore running after the system fault is cleared for 5 minutes.