Solar Inverter

Different Types of Solar Inverters

How do Solar Inverters Work?

What Does a Solar Inverter Do?

The solar inverters are an important component in a solar array. It plays a pivotal role in the functioning of the system to providing protection to the system. The inverter functions are described below.

Solar Inverter Key Terms to Know

Clipping/scalping
This is the term used to describe the energy output that is lost due to undersizing an inverter.
Any given inverter has a maximum power rating (at the residential level, measured in W or kW). When solar supplies DC power in excess of that inverter's maximum power rating (what the inverter can handle), the resulting power is "clipped."
It's important to consider the solar panel arrays' maximum power output and select an inverter with the correct size, model, and type in order to avoid excessive clipping.
It's normal for the dc system size to be about 1.2x greater than the inverter system's max ac power rating. For example, a 12 kW solar PV array paired with a 10 kW inverter is said to have a DC: Ac ratio — or "inverter load ratio"— of 1.2.
When you into account real-world, site-specific conditions that affect power output, it may make sense to size the solar array a bit larger than the inverter's max power rating, as there may be very few "power-limiting days," or instances of clipping for that system.

Inverter efficiency
Inverter efficiency is a percentage that tells us how much DC power input to an inverter comes out as usable ac power. No inverter is 100% efficient, although some come close in favorable conditions. In the conversion from dc to ac, power is lost in the form of heat.

Maximum power
Maximum power is the highest amount of power allowed to feed into an inverter, which is a function of the inverter's specifications or the maximum power a solar panel can produce. This will occur at the optimal trade-off between voltage and current along a given panel's I-V (current and voltage) curve.

Maximum power point (MPP)
A solar system's maximum power output will vary with conditions, such as how much sunlight it receives, temperature, and other factors. A fixed-tilt, stationary, roof or ground-mounted solar PV system might only produce its maximum rated power during a limited period of the day. Every specific solar cell has its own unique I-V curve, which relates its maximum power output to variations in current (I) and voltage (V).

Maximum power point tracker (MPPT)
A device that periodically tracks characteristics of a given panel, string of panels, or system, and optimizes and varies voltage and amperage accordingly in order to produce maximum power.

Microinverter
A device that converts direct current (DC) produced by a single solar panel into alternating current (AC).
Micro-inverters are commonly connected to and installed at the site of, or behind, each individual solar panel in an array. Most micro-inverter makes are installed in the field, while some come panel-integrated by the manufacturer.

Optimizer
A DC-DC converter, optimizer, or "panel optimizer," is a module-level power electronic device that increases the solar system's energy output by constantly measuring the MPPT of each individual panel.
The panel optimizers relay performance characteristics via a monitoring system to facilitate operations and any necessary maintenance. In essence, optimizers support flexible system designs and arrangements – with multiple panel orientations, tilts, azimuths, and module types in a given string.
Perhaps the most advantageous benefit of using a dc optimizer is panel-level MPPT, or max-power point tracking. The result is increased energy harvest from a panel system, especially when subject to periodic or sweeping shade.

Peak power point
Another term for maximum power point (MPP).

String inverter
The device that converts direct current (DC) electricity produced by groups of solar panels (called strings), into usable alternating current (AC) electricity.
String inverters are considered a "mature"solar technology that has proved effective, safe, and reliable. Residential, 240V AC string inverters usually carry manufacturer's warranties of about 10 years.

Factors to Consider When Choosing a Solar Inverter

Stability of output voltage

Solar cells create electricity held in storage batteries before being converted to 220V or 380V AC by solar inverters in photovoltaic systems. The output voltage of storage batteries, on the other hand, is determined by the charge and discharge of storage batteries themselves. Meanwhile, the voltage output variance should not surpass 10percent of the rated value when the load changes unexpectedly.

Rated output frequency

Since their ideal frequency is 50Hz, loads with motors, such as washing machines and refrigerators, will heat up and degrade system efficiency and service life. As a result, the output current of solar inverters should be a steady number, typically 50Hz, with a fluctuation of less than 1% under normal operating conditions.

Waveform distortion of output voltage

The maximum waveform deformation (or harmonic content) should be set for sine wave inverters. The output voltage's total waveform distortion is one way to express it, which should not exceed 5%. (10 percent is allowed for single-phase output).
Since inverters' high-order harmonic output current will generate eddy current and other additional losses on the inductive load, excessive waveform deformation of inverters will cause severe heating to load components, which is not amenable to the safety of equipment and impacts the operational effectiveness of the process.

Load power factor

Sine wave inverters have a load power factor of 0.7 to 0.9, with a rated value of 0.9, and can handle inductive and capacitive loads. Whenever the load power is constant, and the active management of the inverter is low, the power inverter's required capacity grows.

Troubleshooting and Diagnostics: Solar Inverter

When your solar inverter is not functioning properly, there are a few steps you can take to diagnose the issue. First, check the DC and AC disconnect switches to ensure they are turned on. Then, inspect the solar panels for any signs of shading, debris, or damage that could be affecting performance. Additionally, reviewing the inverter display screen for error messages or unusual readings can provide valuable insight into the problem. If you notice any abnormalities during your visual inspection, it's crucial to address them promptly. Clearing away any obstructions that may be blocking sunlight from reaching the panels and cleaning the surface of the panels can improve overall efficiency. Furthermore, consulting the inverter manual for troubleshooting guidance specific to your model can help you identify and resolve common issues.

In some cases, conducting a system reboot by shutting off the inverter, waiting a few minutes, and then turning it back on can reset any minor glitches. However, if these basic troubleshooting steps do not resolve the issue, it may be necessary to seek assistance from a qualified solar technician.