Control method of three-level frequency converter

A technology of three-level frequency converter and control method, which is applied to electrical components, conversion devices for converting AC power input to DC power output, and output power, etc. Inverter, small amount of calculation and other problems, to achieve the effect of simplifying the voltage space vector diagram, reducing the amount of calculation, and reducing the cost of hardware

Active Publication Date: 2015-01-21
CHINA UNIV OF MINING & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The calculation amount of the carrier modulation method is relatively small, but the modulation degree can only reach 1, and the bus voltage cannot be fully utilized; the voltage space vector algorithm has a high voltage utilization rate, but the calculation amount of the multi-level voltage space vector PWM increases with the voltage. The increase in the number of levels increases sharply. In some high-performance occasions, the huge amount of calculation limits the development of multi-level inverters

Method used

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  • Control method of three-level frequency converter
  • Control method of three-level frequency converter
  • Control method of three-level frequency converter

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Experimental program
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Effect test

Embodiment 1

[0038] Embodiment 1: the method comprises the following steps:

[0039] a. Determine the instantaneous per-unit value of the a, b, c three-phase reference voltage used to control the output voltage of the three-level inverter Correct the three-phase reference voltage according to whether the three-level inverter needs to perform neutral point potential balance control and the midpoint potential deviation value;

[0040] b. According to the instantaneous per unit value of the three-phase reference voltage Calculate the three-phase pulse sequence switching flag F a , F b , F c ;

[0041] c. Calculate the action time t of the three-phase virtual voltage space vector a , t b , t c ;

[0042] d. The three-level virtual voltage space vector diagram is formed by superimposing the respective virtual voltage space vectors of the three phases. In order to determine the respective action sequences of the three-phase pulses, according to the action time of the three-phas...

Embodiment 2

[0062] Embodiment 2, the control of the diode-clamped three-level inverter:

[0063] In the control method of the three-level frequency converter of the present invention, first, the diode-type three-level frequency converter is selected as attached figure 2 , where the DC bus voltage V dc It is 270V, which is obtained by uncontrolled rectification using three-phase 380V, and the capacitor C 1 、C 2 、C 3 The value is 5000uF, S a1 , S a2 , S a3 , S a4 , S b1 , S b2 , S b3 , S b4 , S c1 , S c2 , S c3 , S c4 A 1200V / 30A insulated gate bipolar transistor (IGBT) is used, and a resistive inductive load is used, wherein the resistance is 0.9 ohms, the inductance is 4 millihenries, and the switching frequency is selected as 1000 Hz.

[0064] 1. First start the 380V three-phase electricity, and the capacitor C 1 、C 2 、C 3 Precharge until the capacitor voltage reaches 270V;

[0065] 2. With 270V as the base value, the instantaneous per-unit value of the three-phase re...

Embodiment 3

[0079] Embodiment 3, cascaded three-level inverter control:

[0080] In the control method of the three-level frequency converter of the present invention, firstly, the cascaded three-level frequency converter is selected as attached figure 2 , where the DC bus voltage V dc It is 270V, which is obtained by uncontrolled rectification using three-phase 380V, and the capacitor C 1 、C 2 、C 3 The value is 5000uF, S a1 , S a2 , S a3 , S a4 , S b1 , S b2 , S b3 , S b4 , S c1 , S c2 , S c3 , S c4 A 1200V / 30A insulated gate bipolar transistor (IGBT) is used, and a resistive inductive load is used, wherein the resistance is 0.9 ohms, the inductance is 4 millihenries, and the switching frequency is selected as 1000 Hz.

[0081] 1. First start the 380V three-phase electricity, and the capacitor C 1 、C 2 、C 3 Precharge until the capacitor voltage reaches 270V;

[0082] 2. With 270V as the base value, the instantaneous per-unit value of the three-phase reference voltage ...

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Abstract

The invention discloses a control method of a three-level frequency converter, and belongs to a control method of a frequency converter. The control method comprises the steps that a. instant per-unit values of three-phase reference voltage used for controlling output voltage of the three-level frequency converter are determined, and the reference voltage is corrected according to a requirement of the three-level frequency converter on midpoint level balance control or not and according to a midpoint level deviation value; b. three-phase pulse sequence switching flags are calculated according to the instant per-unit values of the three-phase reference voltage respectively; c. the action time of three-phase virtual voltage space vectors is calculated; d. a three-level virtual voltage space vector diagram is superimposed by the three-phase virtual voltage space vectors, and a finally output pulse sequence is recombined and sorted according to the action time of the three-phase virtual voltage space vectors and by combining with the three-phase pulse sequence switching flags; and e. a frequency converter control pulse is generated by hardware, the calculated action time is loaded into a hardware unit, and the hardware unit automatically generates the control pulse as required. The control method has the advantages that a PWM (pulse-width modulation) method of the voltage space vectors is simplified.

Description

technical field [0001] The invention relates to a control method of a frequency converter, in particular to a control method of a three-level frequency converter. Background technique [0002] With the development of power electronics technology and the country's increasing attention to energy saving and efficiency enhancement, multilevel inverters are becoming one of the most popular research directions in the application fields of power supply, motor drive and power system conversion. The number of output levels of the multi-level inverter increases, the output voltage waveform has a high sine degree, the harmonic content is low, the load du / dt and di / dt are small, and the reliability of the system operation is greatly improved. [0003] The pulse width modulation (PWM for short) control algorithm to realize the sinusoidal output waveform of the frequency converter is one of the core algorithms of the frequency converter system control. Commonly used PWM algorithms includ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/487
Inventor 叶宗彬谭国俊邓先明蔡凡陈冬沈龙
Owner CHINA UNIV OF MINING & TECH
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