Method for eliminating harmonic wave in Z-source alternating current (AC)/AC converter by using pulse-width modulation (PWM)

Abstract

The invention discloses a method for eliminating harmonic wave in a Z-source alternating current (AC) / AC converter by using pulse-width modulation (PWM), and belongs to the field of signal processing method. The method comprises the following steps of: extracting fundamental wave amount of input voltage through lowpass filtering; and generating a modulation function of which the duty cycle varies along with time through open-loop control by using an error signal which is generated by comparing a fundamental wave amount and an overall amount of an input voltage in real time and by adopting a non-constant duty cycle control mode. The modulation function controls breakover of two groups of serial four-quadrant switches and regulates output of load voltage, and restrains low subharmonic voltage of the input voltage, and moreover, a duty cycle value can be slightly regulated in real time through the output voltage control step to stabilize the output voltage. By the method, only the simple lowpass filtering and sampling and the feed-forward open-loop control are required, and the requirement of the system for controller band width is obviously reduced; and the method is strong in stability and reliability, and the adaptive capacity to emergency harmonic distortion at an alternating current system side is improved.

Description

technical field [0001] The invention relates to a method for eliminating harmonics in a Z-source AC / AC converter by using PWM, and belongs to the field of signal processing methods. Background technique [0002] Harmonic problems in power systems have a long history. At present, the grid voltage waveform often deviates from the sinusoidal waveform and is distorted, and the waveform distortion is becoming more and more serious. The connection of nonlinear loads to the power supply system and the existence of nonlinear components in the power supply system itself are the root causes of the distortion of the voltage waveform of the power grid. The main harmonic sources of the power system are: motors and generators, transformers and reactors, high-order harmonics caused by the nonlinear volt-ampere characteristics of arcs, various types of converters, electric locomotives, and dimming lights. load. The existence of harmonics will cause various harms to the power system or lo...

AI Technical Summary

Problems solved by technology

Harmonics will cause resonance phenomenon in the power grid, affect the effectiveness of power flow calculation, increase network loss, etc.

Harmonics can cause various electrical equipment to fail, such as increasing the load of the motor, resulting in periodic changes in oscillating torque and rotational speed; the skin effect increases the copper loss and iron loss of the motor and transformer and overheats; it causes hysteresis in the transformer core. Phenomenon, increase noise; cause motor and transformer insulation medium strength to decrease, shorten service life; reduce power cable capacity, aggravate aging, increase leakage current; affect communication equipment, automatic and remote control devices, relay protection and measuring devices, Normal operation of instrumentation

Images