Earlier, the method used for fabrication of pure sine wave inverter was linear technology that resulted in less-efficient inverters at high prices. The modern technique used is PWM that created highly efficient systems.
As the popularity of utilizing the alternate sources of power like wind and solar energy is constantly on the rise, it also has increased the demand for the static inverter systems for the function of changing DC energy stored in the batteries to standard AC form. Most of them follow the same fundamental idea, that is a DC supply of moderately low voltage and practically excellent stability is transformed by a oscillator having high and step-up transformer. This DC current has the voltage with magnitude in proportion to the maximum level of the required AC voltage. After this, a power phase at the output produces the desired AC voltage from DC of higher voltage.
In general, there are two types of DC-AC inverters coming in the market at present. One model is known as the "pure sine-wave" inverter that generates sine waves in range of 3% (-30 dB) of Total Harmonic Distortion (THD). These are excellent solution when there is a requirement for clean, close- sine-wave power output for medical apparatus, industrial equipments and various other critical applications.
For instance, some are employed for use in boats and other Recreational Vehicles (RVs) as the core source of power supply and some of them even deliver power back to the electricity power grid. The waveforms, near to the sine waves, with negligible alteration, are necessary at any rate. These equipments come in a range of sizes up to many thousand watts and are generally costly. The conventional methods adopted for creating these models integrated considerable linear technology, decreasing their efficiency and adding on to their cost.
Latest digital sinewave inverter designs put to use the pulse-width modulation (PWM) for feeding a pulsed waveform that allows for significantly easy filtration to realize a close approximation to a pure sine wave form. The good thing about PWM technique is that the switching methods are employed in the power phase, which leads to considerably high efficiency. But this approach also involves the pulse width made to differ in accordance with the amplitude of a sine wave, therefore, calling for quick switching and major control circuitry. This is for the reason that the frequency of the PWM signal is required to be greater than the wave output to be synthesized, for making sure that the PWM signal is filtered successfully. Consequently, there are a lot of complexities involved with regard to this approach as well as it introduces switching losses.
