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From square wave to sine wave: How do inverters affect our power quality?
Inverters play a vital role in today's energy management systems, especially in renewable energy and power conversion applications. The main function of the inverter is to convert direct current (DC) into alternating current (AC), and the type and quality of the AC waveform it generates affects the operating efficiency and safety of the equipment. Therefore, understanding how the inverter works and its impact on power quality is not only a need for professionals, but also important for general users.
Basic working principle of inverter
Inverters use various electrical and electronic devices and circuits to convert DC voltage to AC voltage. These devices can be roughly divided into static inverters and rotating inverters according to the working method. The static inverter usually does not contain any motion components and depends on electronic components for conversion.
"The output waveform of the inverter can be square waves, sine waves, or improved sine waves, which has a great impact on the operation of subsequent equipment."
Different types of output waveforms and their impacts
The type of waveform produced by the inverter is a key factor affecting power quality. The following are the main inverter waveform types:
Square Wave
A square wave is the simplest waveform, but its total harmonic distortion (THD) is about 48.3%, which may have an adverse effect on connected audio equipment and generate unnecessary "buzzing" sound.
Sine Wave
A sine wave inverter can generate a multi-step sine waveform. This type of inverter is usually called a pure sine wave inverter. Although the label of "pure sine wave inverter" is common in the market, in reality the representative output waveforms of these inverters are not always so perfect.
“Most consumer-grade inverters still don’t get the power output to be a perfect sine wave, but for most electronics they are fine with that output.”
Modified Sine Wave
Improved sine waves are composed of two square waves, which are alternately switched after a certain delay. Although the THD of this waveform is still high compared to a pure sine wave, many economical inverters use this design.
Approximate sine wave PWM
Pulse Width Modulation (PWM) methods that approximate sine waves use rapid switching to create a waveform that can be processed by a low-pass filter, which more closely approximates the shape of a sine wave.
Application scope of inverter
With the advancement of technology, inverters are gradually being widely used in different processes, ranging from motor frequency control to uninterruptible power supply systems:
- Solar inverter: In a photovoltaic system, the inverter is responsible for converting the direct current (DC) electricity collected from the sun into alternating current (AC) electricity for home or business use.
- Uninterruptible Power Supply (UPS): used to provide instant AC power when power is cut off to ensure that equipment is not affected.
- Electric vehicles: Variable frequency inverters are used to regulate the speed of electric motors, enhancing efficiency and performance.
- High-voltage direct current (HVDC) transmission: Converts alternating current into direct current to improve transmission efficiency during long-distance power transmission.
With the rise of renewable energy and the growing demand for power quality, the technological development of inverters will become more important. Faced with an ever-changing technological landscape, businesses and home users must adapt to a variety of output waveform characteristics to ensure the normal operation and efficiency of their devices. In this context, we might as well think about: In the future energy transformation, how to choose the right inverter to improve our quality of life and energy efficiency?
