The booming solar industry has driven the growth of demand for solar inverters. However, solar inverters are a large category with various specifications and models, and their selection is also complex. Today we will introduce what does a solar inverter do and some selection tips.
Main content:
More and more users are having solar systems in their home, and they will have a question before choosing solar inverters for their home solar power system. So what kind of inverter should they choose?
1. What does a solar inverter do
What does a solar inverter do is to convert the DC power generated by the solar batteries into AC power that meets the power quality requirements of the grid. It consists of electronic components (IGBT, capacitors, resistors, reactors, PCB, etc.), structural parts (cabinets, chassis, etc.) and auxiliary materials.
According to specific functions of what does a solar inverter do, it can be divided into: string solar inverter, centralized solar inverters, distributed solar inverters, and micro solar inverters. Solar inverters are the core of the solar power generation industry and are positively related to the development of the solar industry.
2. Classification of solar inverters
According to the output waveform, operation mode, output AC phase number, and power flow direction, it is divided as follows:
- Output waveform: square wave inverter, modified wave inverter, pure sine wave inverter such as pure sine wave inverter 1000w to 3000w inverter;
- Operation mode: off-grid inverter, grid-connected inverter;
- Number of output alternating current phases: single-phase inverter, three-phase inverter;
- Power flow direction: one-way inverter, two-way inverter.
3. How to choose a solar inverter
The basic circuit structure of the inverter is shown in the figure below, which mainly consists of input circuit, output circuit, main inverter switch circuit (main inverter circuit), control circuit, auxiliary circuit and protection circuit.
The factors that determine the selection of solar inverters include technical parameters such as output voltage, load power factor, rated output current, rated output capacity, rated output efficiency, and overload capacity. In addition, there are other requirements such as operating environment conditions, electromagnetic interference and noise requirements, safety performance requirements for protective measures, etc.
Specifically, you can refer to the following points:
① Rated output capacity:
It represents the inverter's ability to supply power to the load. First consideration should be given to having sufficient rated capacity to meet the electrical power requirements of the equipment under maximum load, as well as system expansion and the connection of some temporary loads.
② Output voltage adjustment performance:
The adjustment performance of the output voltage indicates the ability of the inverter to stabilize the output voltage. Generally, the inverter gives voltage regulation rate and load regulation rate.
- Voltage regulation rate: The deviation (%) of the inverter's output voltage within the allowable fluctuation range of the inverter's input DC voltage should be ≤3%;
- Load regulation rate: A high-performance inverter should also provide the deviation (%) of the inverter's output voltage when the load changes from 0 to 100%, which should be ≤6%.
Off-grid solar power generation systems use batteries as energy storage equipment, and the LFP battery terminal voltage can vary up to about 30% of the nominal voltage. Therefore, in order to ensure that the solar power generation system supplies power with a stable AC voltage, the inverter must have good voltage regulation performance.
③ Overall machine efficiency:
The overall efficiency indicates the power loss of the inverter itself. Inverters with larger capacity also provide efficiency values under full load operation and low load operation. Generally, the efficiency of inverters below kW level, like 500w inverter, should be 80% to 85%; the efficiency of 10kW level inverters should be 85% to 90%; the efficiency of larger power inverters must be above 90% to 95%.
In the design of special inverters for solar power generation systems, special attention should be paid to reducing its own power loss and improving the efficiency of the entire machine. This is because the actual efficiency of a 10kW-class general-purpose inverter is only 70% to 80%.
When used in a solar power generation system, it will cause an energy loss of 20% to 30% of the total power generation. Therefore, when the household system is not using power, the inverter should be turned off to reduce losses when power is not used.
④ Protection function:
The inverter should have over-voltage, over-current and short-circuit automatic protection, and other protections such as over-heat protection function, circuit breakage, and phase loss protection.
⑤ Startup performance:
The inverter should start reliably under rated load. A high-performance inverter can be started at full load multiple times without damaging the power switching devices and other circuits. For their own safety, small inverters sometimes use soft start or current limiting starting measures or circuits.
4. What to consider when choosing home solar inverter
① Maximized revenue
What does a solar inverter do? It is a device that converts DC power generated by solar modules into AC power usable by residents. Therefore, power generation conversion efficiency is a priority issue when purchasing an inverter.
At present, it has become a mainstream trend for household solar systems to adopt high-power and high-current components. Therefore, for installing household solar systems, you must first consider inverters adapted to high-current components, which have higher conversion efficiency and lower costs. In addition, there are several important indicator parameters for comparison:
- Inverter efficiency: The maximum efficiency and MPPT efficiency of the inverter are important indicators for considering the power generation of the inverter. The higher the efficiency, the stronger the power generation.
- DC operating voltage range: The wider the DC operating voltage range, the earlier start and later stop, which means longer power generation time and higher power generation.
- Accuracy of MPPT tracking technology: The MPPT tracking technology should have high accuracy, fast dynamic response, and can adapt to rapid changes in illumination, to improve the power generation efficiency.
② Flexible adaptation
The environment of household power stations is relatively complex. Problems such as rural power grid terminals and power consumption will cause inverter AC overvoltage, undervoltage and other alarms. The solar inverter needs to have weak grid support, a wide grid voltage adaptability range, and overvoltage derating, reactive power compensation and other functions to reduce fault alarms.
The number of MPPTs is also one of the important indicators to be considered, multi-channel MPPT configuration can be flexibly configured according to factors such as different orientations, different roofs, and different specifications of components.
③ Installation difficulty
Smaller and lighter models are easier to install. At the same time, you should choose a solar inverter that has been set up in the factory before leaving the factory so that it can be used as long as powered on when getting installed to a household solar system, which saves the debugging time and is more convenient.
④ Safety and stability
Since many solar inverters are installed outdoors, the IP waterproof and dustproof level is a protection index that cannot be ignored, which can effectively protect the inverter from harmful effects in adverse climate environments.
Choose an inverter with IP65 or above to ensure the environment wouldn’t affect what does a solar inverter do. In terms of protecting what does a solar inverter do, in addition to necessary functions such as DC switching, input overvoltage protection, AC short circuit protection, AC output overcurrent protection, and insulation resistance protection, there are three other very important functions:
- DC arc intelligent detection AFCI: It can accurately distinguish the arc signal and quickly shut down to avoid fire and protect the safety of users.
- Fault recording function: Observe and record the AC side voltage and current waveforms of the inverter in real time to quickly locate the problems.
- Smart IV scanning and diagnostics: It can accurately locate string faults and proactively discover problems. With multiple guarantees and stable operation of the power station, you can truly feel at ease.
⑤ Intelligent management
In today's digital era, intelligent devices can provide users with more convenience. Inverters equipped with intelligent management platforms can bring great convenience to users in managing what does a solar inverter do:
First, you can use your smartphone to monitor the power station, check power station operation data anytime and anywhere, and understand the status of the power station in a timely manner. At the same time, manufacturers can discover problems through remote diagnosis, analyze the causes of failures, provide solutions, and solve problems remotely in a timely manner.
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