Application of Pulse Width Modulation Technology in Inverter Power Supply
The principle of inverter power supply uses thyristor circuits to convert direct current into alternating current, which corresponds to the reverse process of rectification and is defined as inverter. For example, in an electric locomotive using thyristors, when going downhill, the DC motor is used as a generator to brake and convert the locomotive's potential energy into electrical energy, which is then sent back to the AC power grid. For example, if a running DC motor needs to brake quickly, it can also be operated as a generator, converting the motor's kinetic energy into electrical energy and sending it back to the power grid. The circuit that converts direct current into alternating current is called an inverter
The principle of inverter power supply
The reverse process of converting direct current into alternating current using a thyristor circuit, which corresponds to rectification, is defined as inversion. For example, in an electric locomotive using thyristors, when going downhill, the DC motor is used as a generator to brake and convert the locomotive's potential energy into electrical energy, which is then sent back to the AC power grid. For example, if a running DC motor needs to brake quickly, it can also be operated as a generator, converting the motor's kinetic energy into electrical energy and sending it back to the power grid. The circuit that converts direct current into alternating current is called an inverter circuit. In specific situations, the same set of thyristor converter circuits can be used for both rectification and inversion. When the inverter is working in the inverter state, if the AC side of the inverter is connected to the AC circuit, it is simple, but the harmonic content of the output voltage waveform is too high, and the THD (current harmonic distortion rate) is also too high; The harmonic content of the output voltage waveform of the phase-shifting multi overlap inverter power supply is small, that is, the THD is small, but the circuit is more complex. The PWM pulse width modulation inverter power supply, which has both computer circuits and can output voltage waveforms, has been widely used.
The so-called pWM pulse width modulation technology (pWM) is a modulation wave that uses a reference wave (usually a sine wave, sometimes a trapezoidal wave or a sine wave or square wave injected with zero sequence harmonics) as the modulation wave, and a triangular wave (sometimes a sawtooth wave) with a frequency N times the modulation wave as the carrier wave for waveform comparison. In the part where the modulation wave is larger than the carrier wave, a rectangular pulse sequence with equal amplitude and width proportional to the modulation wave is generated to be equivalent to the modulation wave. The analog quantity is replaced by a switching quantity, and the DC power is transformed into a carrier wave by controlling the on/off of the inverter power switch tube. AC power, this technology is called pulse width control inverter technology. Due to the linear variation of the amplitude of the carrier triangle wave (or sawtooth wave), this technology is called pulse width control inversion technology. Due to the linear variation of the upper and lower widths of the carrier triangle wave (or sawtooth wave), this modulation method is also linear. When the modulation wave is a sine wave, the pulse width of the output rectangular pulse sequence changes in a sinusoidal pattern. This modulation technique is commonly referred to as Sinusoidal Pulse Width Modulation (SPWM) technology.
