Solar power inverters change the direct current (DC) electricity generated by your solar panels into alternating current (AC) energy that your lamp can use. They also ensure that no DC electricity runs to the external power lines, protecting line workers from injury.

Smart inverters can communicate two-way with the grid and perform a variety of grid-support functions.

Grid-Tied Inverters

Grid-tied inverters, also known as microinverters, convert your solar panels’ collected direct current (DC) power into alternating current (AC) energy that can be used in your home or sold to the grid. These inverters also monitor the flow of electricity between your solar system and the utility grid.

Modern grid-tied inverters are engineered to constantly optimize their output power by tracking the maximum power point of your solar array. This maximizes your solar power inverters production and helps you qualify for NET metering, which reduces your monthly utility bill.

One of the downsides to grid tied systems is that they aren’t powered by batteries, and must immediately disconnect during a power outage. This is necessary to protect the line workers who are trying to restore the electricity supply. This is a reason why cheap plug-and-play grid tie inverters are not legal.

Battery-Based Inverters

Inverter batteries are a key component of off-grid solar power systems in RVs, van conversions, cabins and tiny homes. These battery based inverters convert DC solar energy to AC electricity to run appliances and devices.

A battery-based inverter also gives you the freedom to travel or live off-grid without worrying about recharging your solar power system. A battery-based inverter allows you to use solar energy on cloudy days or during an outage.

Battery-based inverters for solar use advanced power electronics to produce AC electricity from a variety of sources including a battery bank, solar panels or the grid. These inverters often have a built-in BMS or battery management system that monitors and controls the state of charge, temperature and voltage of your solar batteries.

Some battery-based inverters (like the ones sold by Blue Pacific Solar) have a pure sine wave output that's compatible with most appliances and sensitive electronics. Others (like the Trace and Xantrex inverters) give you a modified sine wave, which can be compatible with simple appliances but can cause noise or damage to some electronics.

String Inverters

Rather than producing grid-matching AC power at the back of each panel, string inverters produce it in a central location. This approach is economical at the upfront cost, but limits system expandability in the future. A single failing inverter or shaded panel can wreak havoc on the whole solar power system.

One way to mitigate this limitation is to pair a string inverter with power optimizers. These modules optimize the DC output of each solar panel so that they can maintain maximum production even when some panels are shaded or impaired by mismatch with the rest of the system.

Another benefit of adding optimizers or microinverters is individual panel monitoring. With these options, you can see how each panel is performing on a smartphone app or in your web monitoring portal (Fronius offers SolarWeb). It can help to quickly spot panels that are being affected by shading or getting assaulted by bird poop. And while this extra level of monitoring adds to the overall project expense, it may prove more cost-effective in the long run.

Multilevel Inverters

A multilevel solar micro inverters is a power converter that generates stepped output voltage by using multiple dc voltage sources. This is a more advanced version of a conventional two-level inverter and can provide a number of benefits including lower harmonics, reduced current stress on components and higher efficiency.

There are several different types of multilevel inverters but the most common is a symmetrical MLI. This uses a H-bridge unit as one of the polarity sections and allows for up to five output levels. Other topologies include diode clamped and flying capacitor MLIs. These topologies have more switches, diodes and capacitors, which increases the component count and can lead to increased cost and complexity.

To control the multilevel inverter, a closed-loop system is required. This can be implemented with a variety of methods including repetitive control, space vector modulation and proportional resonant control. Linear current regulators are also used to limit the input current and suppress dc current transients.