The "Brain" of Photovoltaic Power Generation System - Inverter, Do You Really Understand?


The "brain" of photovoltaic power generation system - inverter, do you really understand

As the core component of the entire photovoltaic industry chain with extremely intelligent characteristics, the inverter is the only intelligent device in the photovoltaic system that has a variety of digital functions and is directly connected to the power grid. Faced with such an important device in the photovoltaic system, the photovoltaic inverter, do you really understand?

What is the main function of the inverter?

As the power conversion equipment of photovoltaic power station, inverter occupies a pivotal position in the whole power station.
The photovoltaic inverter is a power electronic device that converts the low-voltage direct current generated by the components into alternating current, which is connected to the load or incorporated into the power grid, and is the core device in the photovoltaic system.

The grid-tied inverter has the following main functions:
Converts direct current generated by photovoltaic modules to alternating current
Dynamically find and utilize the maximum power point (MPP) to maximize available power with a maximum power tracker
Record running data
Provides current, voltage and related protection of the local grid

What are the classifications of inverters?

In terms of product types, inverter products are currently mainly divided into four categories, namely:

  1. Centralized inverter (power range is 250KW-10MW, mainly used in large ground power stations)
  2. Distributed inverter (power range is 1MW-10MW, mainly used for complex large-scale ground power stations)
  3. String inverter (power range is 1.5KW-250KW, mainly used for household, industrial and commercial distributed and ground power stations, etc.)
  4. Micro inverter (power range is generally below 4kW, mainly used in distributed and other small and medium-sized power stations.

Based on the consideration of photovoltaic safety issues, it is also increasingly used in large-scale industrial and commercial distributed power stations)

The micro-inverter can invert each component in the system and perform independent MPPT control, which can greatly improve the overall efficiency, and can also avoid the DC high voltage, poor low-light effect, and barrel effect of traditional inverters.

Where is the inverter installed?

1. Installation scheme of common ground distributed projects:
It can be installed under a string of components nearby, and the equipment can be directly fixed on the column by using a fixed bracket installation or by using a hoop type installation.
This solution needs to pay attention to the strength of the bracket and the column and the height of the photovoltaic inverter from the ground, so as to prevent the equipment from being flooded by the rain in heavy rain.

2. Large-scale industrial and commercial plant installation solutions:
Large-scale industrial and commercial roofs are generally open, without ceilings and parapets, where photovoltaic inverters can be hung. In order to reduce the cost of cables, it is generally necessary to self-made mounting brackets, and the inverters are hung on the self-made brackets. The brackets The load-bearing and fixed form of the inverter and the ability to resist typhoons in coastal areas need to be considered.

3. ommon household distributed project rooftop power station installation scheme:
The photovoltaic inverter should be installed on the south wall as much as possible, and its panel should face north to avoid the sun. The installation of the machine should be at a suitable height from the ground so that the LED display can be observed and read.
When installing outdoors, a rain-proof sunshade should be installed on the inverter to avoid direct sunlight and rain.

4. Systems using microinverters:
The microinverter can be mounted directly on the bracket below the module, or integrated with the module for a modular design, enabling plug-and-play.
The micro-inverter is small in size and does not occupy installation space independently. Distributed installation is easy to configure, and it can make full use of space and adapt to applications with different installation directions and angles.

What is MPPT?

MPPT, the abbreviation of Maximum Power Point Tracking, means that the inverter adjusts the output power of the photovoltaic array according to different ambient temperature, light intensity and other characteristics of the outside world, so that the photovoltaic array always outputs the maximum power.
Under the same input power, the number of inverter MPPT circuits affects the power generation of the photovoltaic power station, especially when the power station has problems such as shadow occlusion, different component orientations, and inconsistent component performance.
As the life of the power station is longer (the components are attenuated), the number of MPPT channels increases, the MPPT single channel tracking accuracy is higher, the dynamic response speed is fast, and it can adapt to the rapid changes in illumination and increase the power generation.
Because the micro-inverter product is a fully parallel structure, each component has an independent MPPT, and the power generation between the components does not affect each other.
Since there is no short-board effect, some components such as shadow blocking and dust will not affect the power generation of the entire string of modules, maximizing the output of each module and improving the power generation of the power station.

How does the inverter realize network communication?

The communication methods of photovoltaic inverters mainly include the following:

  1. GPRS/4G communication (suitable for small and medium-sized distributed projects and areas with better mobile signal coverage)
  2. WiFi communication (suitable for user or small industrial and commercial systems, the corresponding area has wireless network coverage)
  3. RS485 communication (applicable to medium and large industrial and commercial projects)
  4. PLC communication (applicable to large-scale photovoltaic power station projects and boost grid-connected projects)
  5. ZigBee communication (for consumer or small industrial and commercial systems)
  6. ZigBee is a new short-range, low-cost, and low-power wireless network technology. It has many advantages, such as large network capacity, short delay, security, and flexible working frequency bands.

The PowMr micro inverter adopts ZigBee wireless communication technology. The energy communicator ECU is responsible for collecting and transmitting the power generation data of the microinverter. The data collection is realized by ZigBee technology, and each ECU can monitor hundreds of inverters.
There is a wireless signal relay function between the micro-inverses, which can relay communication information. The entire system network is built into a cellular (MESH)-shaped communication network, which can make the transmission speed faster and more stable.