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

A technology for eliminating harmonics and converters, applied in the field of signal processing, can solve the problems of reduced dielectric strength of motors and transformers, increased network loss, and shortened service life, so as to ensure high-quality output load voltage, improve accuracy and reliability Sexuality, the effect of eliminating low-order harmonic components

Inactive Publication Date: 2013-01-16
SHANDONG DANENG TECH
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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

Method used

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

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Embodiment Construction

[0023] The present invention will be further described below in conjunction with accompanying drawing.

[0024] Such as figure 1 As shown, it is a circuit structure diagram of a Z-source AC / AC converter in the present invention, and the switching elements in the figure are four unidirectional power switches. Q1, Q2, Q3, Q4 are reversely connected in series respectively to form two sets of four-quadrant switches S1 and S2, and D1~D4 are respectively connected in parallel at both ends of Q1~Q4 as body diodes. Two identical capacitors C1, C2 and two identical inductors L1, L2 form a Z-source X-shaped symmetrical network, which plays the role of filtering and energy storage. Lf is the series filter inductance.

[0025] Let the equivalent duty cycle of S1 be D, and the switching period be T s . Due to the complementary conduction of S1 and S2, the equivalent duty cycle of S2 is 1-D, ignoring the influence of the dead zone. According to the on-off status of the switching eleme...

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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...

Claims

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Application Information

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IPC IPC(8): H02M1/12
Inventor 解大宋元锋王斯斯张延迟周长金庄俊鹏张玉涛王雷刘林泉何伟荆延飞
Owner SHANDONG DANENG TECH
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