1 basic configuration
A set of photovoltaic power generation systems mainly includes solar arrays, photovoltaic inverters and AC circuit breakers. The basic configuration is shown in the figure below. A photovoltaic string composed of photovoltaic modules converts solar energy into direct current electrical energy. The inverter acts as an intermediate unit to convert this DC energy into AC power that meets the requirements of the grid and feeds it into the grid.
2 main equipment
2.1 Solar array
The solar array uses XXX solar modules, and its performance parameters are shown in the table below.
2.2 Photovoltaic inverter
The photovoltaic inverter uses XXX type PV inverter, and its input and output parameters are shown in the following table.
The internal circuit principle of the string type PV inverter is shown in the following figure, which mainly includes DC EMC filter, MPPT and boost circuit, inverter, protection circuit, AC EMC filter and human-machine interface and communication interface. section.
The inverter allows one-way PV string access. The inverter configures an MPPT tracker for the PV input to ensure that the DC string generated by the PV string is maximized by the inverter. The inverter circuit converts direct current into alternating current energy. The protection function circuit monitors the operating condition during the operation of the inverter, and triggers the internal relay under abnormal working conditions to protect the internal components of the inverter from damage. In addition, the DC switch safely cuts off the DC side current. The inverter machine has a human-computer interaction interface for operation and display, which can be used for maintenance and user viewing real-time or historical operation information, as well as product fault information. In addition, the inverter RS485 interface provides the option to monitor the health of the entire PV solar panel mounting system.
3 equipment installation
The electrical installation of the inverter includes DC side electrical connection, AC side electrical connection and communication cable electrical connection.
3.1 Electrical connection diagram
3.2 Inverter external wiring
The external terminal block is located at the bottom of the inverter as shown below. Includes DC side, AC side, and communication terminals. This makes electrical connection without opening the upper cover of the inverter and the terminals are all in-line waterproof terminals, which ensures the safety of the wiring personnel and the wiring is convenient.
3.3 Connection Cable Specification
3.4 AC side electrical connection
The grid connected to the string type XXX PV inverter must have the following conditions, otherwise the inverter will not work.
Grid voltage: 174~274V;
Grid frequency: 47~53Hz/57~63Hz;
The inverter is connected to the grid via three wires (L, N and PE). The interface to the grid is the AC terminal, and the power fed into the grid is single-phase. (Sunshine power supply provides the corresponding AC connector for the AC side electrical connection of the inverter).
3.5 AC circuit breaker
In order to protect the inverter's AC side circuit and personal safety during wiring, a two-pole circuit breaker is configured as a protection device for each inverter. It is recommended that the AC breaker short-circuit current be 13A.
3.6 Solar PV panel grounding
Since the string type XXX type photovoltaic inverter is a transformerless type, it is required that the positive electrode and the negative electrode of the photovoltaic array cannot be grounded, otherwise the inverter may be irreparably damaged.
In this photovoltaic power generation system, all non-current-carrying metal parts and equipment casings should be connected to the earth, such as the solar panel mounting structure support of photovoltaic modules, inverter casings, etc.
The grounding diagram is shown below
3.7 Communication connection
The RS485 communication connection can be used to transfer the inverter's operation information to the host computer or local data storage display device (such as SolarInfo Logger) that has monitoring software (such as SolarInfo Insight) installed.
If there is only one inverter, the RS485 communication cable with the plug-in plug can be used for communication.