PULSE WIDTH MODULATION INVERTER
Switching techniques of pulse width modulation (PWM) have been popular in the area of power electronics and drive systems. PWM is commonly used in applications like motor speed control, converters audio amplifiers, etc. PWM is used to adjust the voltage applied to the motor. There is no single PWM method that can suit all applications.
As per the advanced technology in solid-state power electronic devices and microprocessors, various pulse-width modulation (PWM) techniques have been developed for different industrial applications. For the above reasons, the PWM techniques have been the subject of intensive research since the 1970s.
The main objective of the PWM is to control the inverter output voltage and to reduce the harmonic content in the output voltage. Pulse width modulation (PWM) techniques are mainly used for voltage control.
These techniques are the most efficient and they control the drives of the switching devices. The different PWM techniques are Single pulse width modulation, Multiple pulse width modulation, Phase displacement control, Sinusoidal pulse width modulation, Harmonic Injection modulation, Space Vector pulse width modulation, Hysteresis (Delta) pulse width modulation, Selective Harmonic Elimination, and Current Controlled pulse width modulation. The Hysteresis controller is used for the Current source inverter and all the remaining PWM techniques are used for the Voltage source inverter. Sinusoidal and Space Vector PWM techniques are the most widely used. They control the output voltage as well as reduce the harmonics.
What is a PWM Inverter?
A Pulse Width Modulation (PWM) Inverter is an electronic device that converts direct current (DC) voltage into alternating current (AC) voltage. It does this by generating a series of pulses with varying widths, known as PWM signals, to produce an AC voltage waveform that approximates a sine wave.
In a PWM Inverter, the width of the pulses is adjusted based on the input DC voltage and the desired output AC voltage. By controlling the width of the pulses, the PWM Inverter can control the average voltage output, which in turn controls the AC voltage waveform. This makes PWM Inverters highly efficient and precise, as they can produce a high-quality AC waveform with minimal distortion.
PWM Inverter Circuit Diagram
PWM Working Principle
The working principle of Pulse Width Modulation (PWM) is based on the varying widths of electrical pulses to control the average voltage and, therefore, the power delivered to a load.
Here’s how it works:
- A DC voltage source is connected to the input of the PWM inverter.
- The PWM inverter uses a control circuit to generate a reference signal with a fixed frequency and amplitude, which is used as a reference for the PWM pulses.
- The reference signal is compared to a triangular waveform of the same frequency, and the difference between the two signals is used to control the width of the PWM pulses.
- The resulting PWM signals are then amplified and fed to a high-frequency switch, which turns the PWM signals into a square wave voltage.
- The square wave voltage is then filtered to remove the high-frequency components and produce a smooth AC voltage waveform.
PWM Inverter Types & Waveforms
There are two main types of Pulse Width Modulation (PWM) Inverters:
- Sine wave PWM Inverter: This type of PWM Inverter produces a sine wave output, which is a smooth and continuous waveform that is highly suitable for most AC applications. Sine wave PWM Inverters are commonly used in applications where high-quality AC power is required, such as in renewable energy systems, uninterruptible power supplies (UPS), and motor drives.
- Square wave PWM Inverter: This type of PWM Inverter produces a square wave output, which is a sharp and discontinuous waveform that is highly suitable for certain DC applications. Square wave PWM Inverters are commonly used in low-cost applications where the quality of the AC power is not critical, such as in battery-powered devices and power tools.
In terms of the waveform produced by PWM inverters, there are two main types:
- Pure Sine Wave: This waveform is a smooth, continuous waveform that closely resembles a sine wave. Pure sine wave inverters are commonly used in applications where high-quality AC power is required, such as in renewable energy systems and uninterruptible power supplies (UPS).
- Modified Sine Wave: This waveform is a square wave that has been filtered to produce a waveform that is closer to a sine wave. Modified sine wave inverters are commonly used in low-cost applications where the quality of the AC power is not critical, such as in battery-powered devices and power tools.
Application of PWN
Pulse Width Modulation (PWM) is widely used in a variety of applications, some of the most common of which include:
- Renewable Energy Systems: PWM inverters are commonly used in renewable energy systems, such as solar and wind power systems, to convert DC power from solar panels or wind turbines into high-quality AC power for use in homes and businesses.
- Motor Drives: PWM inverters are used in motor drives to control the speed, torque, and direction of AC motors. They are ideal for applications that require precise control over motor speed, such as in elevators, conveyors, and robotic systems.
- Uninterruptible Power Supplies (UPS): PWM inverters are used in UPS systems to provide backup power during power outages. They convert DC battery power into AC power to keep critical systems, such as computers and data centers, running during a power outage.
- Power Tools: PWM inverters are used in battery-powered power tools to convert DC battery power into AC power for use in tools such as drills, saws, and lights.
- Lighting Control: PWM inverters are used in lighting control systems to dim lights and control the brightness of LED lights.
- Electric Vehicle Charging: PWM inverters are used in electric vehicle charging systems to convert AC power from the grid into DC power for charging electric vehicles.
- HVAC Systems: PWM inverters are used in HVAC (heating, ventilation, and air conditioning) systems to control the speed of fans and compressors and to regulate the temperature in a building.