INVERTERS
The brain of solar photovoltaic power systems
What Is A Solar Inverter?
In techHUB #1, the working principles of solar panels have been described, which illustrates how solar PV panels generate direct current (DC) power from sunlight. However, most household appliances use alternating current (AC) power which is normally drawn from the public power grid. Therefore, solar energy in its original form (DC form) is not useful. A solar inverter is one of the most crucial components in a solar system since it is capable of converting DC power to AC power.
How Do Solar Inverters Work?
In figure 1, Q1, Q2, Q3, and Q4 are semiconductor switches or power switches. Depending on the application’s power capacity and switching frequency, these power switches can be either gate turn-off (GTO) thyristor, integrated gate commutated thyristor (IGCT), metal oxide semiconductor field-effect transistor (MOSFET) or insulated gate bipolar transistor (IGBT), etc.
By turning on and off those power switches in the correct manner, the current flowing through the load changes its own direction continuously as shown in figure 2. The obtained current waveform (in the square waveform) is then filtered out by a dedicated filter circuit to generate a smooth sine wave AC power, which can finally be used to power household appliances.
Types of Inverters and Recommendation of Inverters for particular sites
There are three most popular types of solar inverters: String inverters, Microinverters, and Inverters integrated with power optimizers.
String inverters:
String inverters are the most cost-effective inverter option. If your roof had little shading throughout the day and did not face in numerous directions, a string inverter would normally be a great option for your system.
At GreenElec, we are dedicated to designing and installing tier 1 inverters including SMA Solar Technology AG (German brand). Due to the SMA’s advanced PV optimization technology
ShadeFix, solar production can still be optimized even in shaded conditions. Therefore, in some conditions where there is not much shading on the roof, SMA solar systems may outperform solar systems with module-level power electronics (MLPEs)
Microinverters:
Microinverters are one type of module-level power electronics (MLPEs), which can usually be mounted on the back of the solar panel to convert DC power generated by your solar panels into AC power on your roof, avoiding high DC voltage running on the roof. Instead, the output voltage of microinverters is typically 240V AC which brings down the potential of causing fire on a hot day. Microinverters provide comprehensive panel-level performance monitoring which means any issues in the system can be pinpointed and resolved with ease.
At GreenElec, Enphase microinverter is our preferred brand, which has been designed and commissioned for our clients in the last 10 years.
Inverters integrated with power optimizers:
Power optimizer systems offer many of the same benefits as microinverters and are typically viewed as a compromise between microinverters and regular string inverters.
Power optimizers are also one type of module-level power electronics (MLPEs). However, rather than converting DC electricity to AC electricity at each solar panel, the DC power of each solar panel is optimized by its embedded power optimizer. The optimized DC power will then be converted to AC power at the simplified grid-connected inverter.
Generally, when your roof is shaded for most of the day, the panel-level optimization provided by power optimizers typically results in higher solar power production than a string inverter alone. Power optimizers, similar to microinverters, reduce the impact of panel shading on system performance while also enabling panel-level performance monitoring.
At GreenElec, SolarEdge Power Optimizers are a preferred solution for commercial and residential system designs as it provides our clients:
- More Energy
- Flexible Design Solutions
- Panel Level Visibility
- Superior Safety Elements
- Long Warranties
Author: Hieu Uong
Electrical Designer & Estimator
GreenElec
