Inverters are essential to the transition to renewable energy because they convert the direct current (DC) output of solar panels into usable AC. They are also used to provide electricity to various household and commercial establishments.
The evolution of inverters has been instrumental in the rapid growth of renewable energy. They are more energy-efficient, cheaper, and are generally more reliable.
DC Power vs AC Power
DC power is simply the one-way flow of a current. In solar cells, the current will vary slightly during the day, but it will always flow the one way.
AC power has its own unique characteristics, such as the varying intensities of its currents. There are also different types of waves that form when the current is plotted against time.
The inverter’s job is to take the DC power and convert it to an AC power curve.
Converting DC Power to AC Power
Early AC-powered devices have used mechanical switches to control the flow of electricity. This type of switch produces a cyclic current with varying frequency and duration.
Instead of turning off the current, the switch reverses it and generates an alternating current. The frequency can be adjusted by the device’s speed.
Some types of equipment, such as fans and audio equipment, can run on AC power. However, for most households and businesses, this type of power is not ideal.
Sine Wave Inverters
To successfully convert DC to AC, an inverter will require more complex electronics.
Sine wave inverters work in three stages: the oscillator stage, the booster or amplifier stage, and finally the transformer stage.
The first step in converting DC to AC is the oscillation stage. This process produces a set of alternating currents with a frequency of 60 Hz. Although the DC current is now converted to an AC current, the waves are too small to provide much power.
The booster stage takes the signal from the oscillation stage and amplifies it. This produces higher-than-normal waves and provides enough power to operate.
The voltage control stage is the last component that’s involved in converting DC to AC. It’s important that the stability of the AC supply is maintained to avoid issues with equipment and the grid.
Pure Sine Wave vs Modified Sine Wave Inverters
There are two main types of sine wave inverters: pure sine wave and modified sine wave. The former uses more expensive electronics to produce a more stable and smooth sine wave, while the latter uses simpler but still powerful electronics.
The figure below compares outputs from a modified sine waver inverter and a pure sine wave inverter.
Modern Inverters for Solar Arrays
Modern inverters have plenty of functions to help maximize the power and energy from solar panels. They can also help avoid grid disruptions.
When it comes to solar power, the output voltage and current changes as the sun rises. This is why inverters are very smart to take advantage of these changes.
The smart inverters can also alter the impedance of a circuit to make sure that the solar panels are operating at their maximum power point. This feature, which is called maximum power point tracking, can also be used to prevent system failures.
One of the main advantages of having multiple inputs is that it allows the panels to be controlled separately and operate at their maximum power points. This eliminates the need for one controller to operate the various parts of the array. Instead, it allows the panels to be controlled using their separate MPPTs.
Inverters that are known as microinverters are also known to operate at the panels’ maximum power point. They can also be used when the sun gets too hot to provide sufficient power.
Due to the large amount of solar power being used in Australia, the country’s grid power can become unstable. This can lead to network regulators’ concerns when it comes to system reliability.
A good solar inverter can regulate the frequency and provide a great quality of sine wave. However, they also need to be controlled to provide a good power factor.
The power factor, which is a measure of how well the AC and DC components of a solar inverter match up, is also used to evaluate the system’s performance.
Modern inverters can now provide power factor correction for the output power. This benefit is very helpful in transitioning to green power.