Power Optimizers in a Solar Inverter
An inverter is the heart of your solar energy system. It turns the direct current (DC) flowing in from your solar panels into alternating current (AC) electricity that can be used by your appliances and power the grid when you produce more than you consume.
Inverters also monitor your system’s performance and can synchronize with the grid. Some inverters even participate in smart grid functions like voltage regulation and frequency control.
Power Optimizers
Power optimizers (sometimes known as module level power electronics, or MLPE) are small DC-to-DC converters that sit on the back of PV modules and convert the DC output of each panel to a different voltage and current. They help the string inverter run more efficiently by reducing resistance and voltage drop to match the PV panel’s maximum power point.
SolarEdge’s optimizers track each panel’s peak power in real time and regulate each PV module’s output to reduce voltage, improving the efficiency of a solar energy system. Solar Inverter The optimizers then send the regulated electricity to the central inverter. They’re also compatible with existing systems, allowing for more modules to be added to a solar array without the need for additional inverters.
When it comes to solar, optimizers are one of the most important tools in an installer’s toolkit. By enabling larger PV systems and maximizing the efficiency of the system, they lead to higher revenues for installers and lower electricity bills for home and business owners.
They also mitigate module mismatch loss caused by manufacturing tolerance, partial shading and aging. Lastly, optimizers can help with safety, as they are equipped with a rapid shutdown function to ensure that the high DC voltage produced by the solar panels will be safely reduced to a safe level when the inverter is turned off.
The downside to optimizers is that they require extra cabling for each PV module to which it is attached. This leads to a voltage drop of around 0.27 V per power optimizer in full sun, which can add up quickly and reduce your system’s performance. This is why some manufacturers have combined power optimizers with microinverters to create so-called smart modules. While the increased cost of this “hybrid” approach can lead to higher upfront costs, it is claimed to be the lowest-cost solution overall.
MPPT Circuits
The MPPT circuit in a solar inverter helps the PV panel deliver the maximum power to the battery. It works by constantly tracking the varying output from the solar panel and matching it to the optimal current. This allows the PV to run at the maximum power point (MPP) under a variety of conditions.
The LT8611 MPPT controller is designed to achieve high efficiency and operate with minimal heat dissipation. It achieves this by using a microcontroller to periodically scan the PV array operating range and determine the best voltage and current to match the MPP. The microcontroller drives the LT8611 SYNC pin high or low, depending on the condition of the solar irradiance.
In between MPPT scans the microcontroller will let the input voltage divider and the tracking function of the LT8611 operate at their maximum performance. This means that the panel will operate at its maximum power point, but the battery charge current will vary with changes in the solar irradiance.
MPPT is a DC-to-DC converter that optimizes the output current of the PV to exactly match the battery voltage. There are several different types of MPPT techniques, including Buck-Boost, CUK, and other characteristic conversion circuits.
All of these MPPT algorithms vary in complexity, speed of convergence, required hardware, required sensors and other factors. They all work differently, but they all achieve the same goal: to maximize the power that is delivered to the battery. In this way, they are much like a car transmission which varies the ratio between engine speed and torque in order to get the most power out of the motor. MPPT is simply a newer technology that does the same for a solar PV array. The result is that your solar inverter will be able to provide more energy from your PV panels at a lower cost.
String Inverters with Optimizers
Power optimizers are placed underneath and inside each solar panel to offer a hybrid solution between a standard string inverter and microinverters. They work to increase energy production by conditioning DC electricity before sending it to a central inverter to be converted into AC current. They help to eliminate the power loss caused by shade or mismatched panel configurations. Power optimizers also allow for panel-level performance monitoring, which can be useful when troubleshooting any issues on a roof-by-panel basis.
A major drawback of using a traditional string inverter system is that a single panel failure can negatively impact the output of all other panels connected in series to it. This is because the inverter is forced to reduce the output of the whole string to match the lowest producing panel, which may be partially obscured or covered with debris at a given time. Power optimizers can help to minimize this issue by allowing each individual panel to operate at peak efficiency independently of the others, regardless of whether it’s receiving afternoon shade or being blocked by debris.
In addition to this, power optimizers also provide a more efficient current conversion process than a standard string inverter. This can be especially helpful when your solar panel array is located on a sloped or uneven rooftop solar batteries manufacture where the panels will need to be tilted differently in order to maximize power production.
While a power optimiser system can be more expensive than a simple string inverter setup, it offers many of the same benefits. This includes improved energy production over the lifetime of your solar system, lower installation costs, and a simpler layout. In addition, since it’s still a DC-powered system, power optimisers can be easily paired with a rapid shutdown device to meet NEC 2017 and 2020 requirements.