CN101873100A - Simplified Phase Voltage Reconstruction Method for Three-level Frequency Converter - Google Patents

Abstract

The simplified phase voltage reconstruction method for three-level inverters is suitable for inverters with three-level topology. The frequency converter can supply power for the squirrel cage motor speed control system, the winding motor double-fed speed control system and the synchronous motor speed control system. Its working method is: divide the vector space output by the traditional three-level inverter into six small hexagons, and carry out the corresponding output phase voltage reconstruction algorithm in each small hexagon. Then, the purpose of three-level calculation is achieved through coordinate translation and compensation calculation. Its algorithm is relatively simple, and the result obtained can completely replace the output sensor, and it is more accurate than directly using the SVPWM command. The adoption of this method simplifies the composition of the system and improves the reliability and stability of the system.

Description

Simplified Phase Voltage Reconstruction Method for Three-level Frequency Converter

technical field

The invention relates to a simplified phase voltage reconstruction method for a three-level frequency converter, which is suitable for squirrel-cage motors, winding motors and synchronous motors powered by the three-level frequency converter.

Background technique

In the three-level high-performance motor vector control system, the accuracy of the output phase voltage has a great influence on the performance of the system. There are two traditional methods at present, one is to use the output voltage sensor to sample into the control system through AD. The second is to directly use the command of SVPWM as the actual output phase voltage.

For the first method, it is necessary to increase the number of corresponding AD channels while adding sensors, and the voltage output by the three-level inverter is a ladder wave, and the value collected by the usual instantaneous sampling A/D converter is not the actual waveform in the The average value in a switching cycle cannot truly reflect the size of the output voltage in this switching cycle. For the second method, the narrow pulse problem is the source of its inaccuracy, because not all outputs are exactly the same as the SVPWM command given, especially in the low-speed and high-speed sections of the motor, the narrow pulse problem is more serious.

At the same time, since the three-level output level is half more than that of the two-level topology, and the output voltage vector is three times that of the two-level, if the output voltage sequence is directly passed, the main vector, zero vector and sub-vector are added respectively. It is very difficult to calculate the time. However, there are relatively mature calculation formulas for two levels. We use the traditional two-level topology inverter output voltage to calculate, which reduces the calculation amount and reduces the system hardware structure. Compared with the second method, we can obtain more precise output voltage.

Therefore, in the frequency converter with three-level topology, adopting the simplified three-level phase voltage reconstruction algorithm will improve the technical guarantee of the reliability and accuracy of the control system.

Contents of the invention

Technical problem: The object of the present invention is to provide a method for output phase voltage reconstruction in a three-level topology and a frequency conversion device using the method. On the one hand, it simplifies the hardware structure of the frequency converter with three-level topology, and on the other hand, it improves the reliability and accuracy of the frequency conversion device.

Technical solution: A simplified phase voltage reconstruction method for a three-level frequency converter according to the present invention. The specific implementation process is as follows:

The first step: first sample the DC bus voltage V _dc of the frequency converter, and record the results;

Step 2: According to the space vector diagram of the three-level inverter and the space vector diagram of the three-level inverter, it is composed of six small hexagons composed of traditional two-level space vectors, and thus calculate A and B , the action time of phase C T _a , T _b , T _c , and the phase voltage V _an , V _bn , V _cn of phase A, B, and C under the two-level topology structure are reconstructed according to the carrier time T _s of the system calculate,

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; an</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; bn</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cn</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; ,</span>$

Step 3: For the reconstruction of the output phase voltage under the three-level topology, use coordinate translation to locate the voltage vectors to be reconstructed on the small hexagons centered on V1, V2, V3, V4, V5, and V6 Each small hexagon can be regarded as a space voltage vector diagram of a two-level topology; and then the components of the centers of each small hexagon on the A, B, and C axes are used as compensation amounts. Added to the result produced by phase voltage reconstruction in a two-level topology,

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; an</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; bn</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cn</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}<span\; class="notranslate">\; ,</span>$

According to the different small hexagons where the reference voltage vector is located, the compensation amounts of A, B, and C phases in each case are obtained as follows:

small hexagon number Phase A compensation V _{a_compensation} Phase B compensation V _{b_compensation} Phase C compensation V _{c_compensation} 1 +V _dc /3 -V _dc /6 -V _dc /6 2 +V _dc /6 +V _dc /6 -V _dc /3 3 -V _dc /6 +V _dc /3 -V _dc /6 4 -V _dc /3 +V _dc /6 +V _dc /6 5 -V _dc /6 -V _dc /6 +V _dc /3 6 +V _dc /6 -V _dc /3 +V _dc /6

Beneficial effects: the above method and the frequency conversion device adopting the method use the equivalent relationship of three levels and two levels on the space voltage vector to directly obtain the output voltage of each phase through corresponding calculation through the DC bus information and the action time information of each phase, For the motor control system, the corresponding voltage sensor is omitted, which simplifies the hardware structure of the system. At the same time, the reliability of the phase voltage obtained by this method is high, which is higher than the method of directly using the reference voltage vector to estimate the phase voltage. Accuracy, improving the speed control accuracy of the system in the high-speed section and low-speed section.

Description of drawings

Figure 1 is a three-level space voltage vector diagram,

Figure 2 is a three-level space voltage vector decomposed into six small hexagonal diagrams,

Figure 3 is a diagram of the compensation voltage in the simplified phase voltage reconstruction algorithm under the three-level topology.

Figure 4 is a diagram of a frequency conversion device using a simplified phase voltage reconstruction algorithm under a three-level topology.

In the figure: three-phase AC input power supply 1, power switch 2, frequency converter with three-level topology 3, controlled motor 4, panel 5 for speed setting and start signal, system controller 6, voltage sensor 7, trigger optical fiber 8. Motor A-phase current sensor 9 , motor C-phase current sensor 10 , encoder 11 .

Detailed ways

The space vector diagram of the three-level inverter shown in Figure 1 can be considered to be composed of six small hexagons composed of traditional two-level space vectors, and each small hexagon that constitutes the space vector diagram of the three-level inverter The hexagons are all centered on the vertices of the inner small hexagons, as shown in Figure 2.

Assuming that the current carrier period is T _s , T _a , T _b , and T _c are the action time of phases A, B, and C respectively, then the output reconstruction formula of the phase voltage under the two-level topology is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; an</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; bn</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cn</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

For the reconstruction of the output phase voltage under the three-level topology, the coordinate translation can be used to position the voltage vectors to be reconstructed in the small hexagons centered on V1, V2, V3, V4, V5, and V6. , as shown in Figure 2, each small hexagon can be regarded as a space voltage vector diagram of a two-level topology. Then, the components of the centers of each small hexagon on the A, B, and C axes are used as the compensation amount, and added to the result of phase voltage reconstruction under the two-level topology, as shown in Figure 3.

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; an</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; bn</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; cn</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; compensation</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

According to the different small hexagon numbers in Fig. 2 where the reference voltage vector is located, the compensation amounts of A, B, and C phases in all cases can be obtained as shown in Table 2:

Table 2: Phase voltage compensation amount under different small hexagon numbers

small hexagon number Phase A compensation V _{a_compensation} Phase B compensation V _{b_compensation} Phase C compensation V _{c_compensation} 1 +V _dc /3 -V _dc /6 -V _dc /6 2 +V _dc /6 +V _dc /6 -V _dc /3 3 -V _dc /6 +V _dc /3 -V _dc /6 4 -V _dc /3 +V _dc /6 +V _dc /6

small hexagon number Phase A compensation V _{a_compensation} Phase B compensation V _{b_compensation} Phase C compensation V _{c_compensation} 5 -V _dc /6 -V _dc /6 +V _dc /3 6 +V _dc /6 -V _dc /3 +V _dc /6

The simplified three-level phase voltage reconstruction principle of the present invention:

The controller 6 and the three-level power converter 3 are mainly used to supply power to the controlled motor 4 , as shown in FIG. 4 . Among them, the DC bus voltage signal measured by the voltage sensor 7 is fed back to the controller 6, and the speed setting and start signals are given to the controller 6 by the operation panel 5. The corresponding voltage reference vector is given by processing, the small hexagon number of the vector is judged, and then triggered by the three-level trigger module and the optical fiber 8 . In this way, the speed closed-loop control system of the controlled motor is formed, which can accurately control the speed of the controlled motor

The three-level phase voltage reconstruction calculation obtains the small hexagon number of the current reference voltage vector and the respective action times of A phase, B phase, and C phase through the DC bus voltage and the three-level trigger module. Based on the formulas (4), (5), and (6), the determined compensation amount is compensated according to the compensation amount in Table 1.

The simplified phase voltage reconstruction method of the three-level frequency converter of the present invention is mainly composed of a controlled motor and a control system. The winding of the controlled motor 4 is connected to a frequency converter 3 with a three-level topology, and the frequency converter 3 is connected to a three-phase AC input power source 1 through a power switch 2 . The A and C phases of the motor winding are connected to the system controller 6 through the current sensors 9 and 10, the DC bus voltage is connected to the system controller 6 through the voltage sensor 7, and the speed given signal and the start signal are connected to the system controller through the operation panel 5 6, the system controller 6 controls the IGBT on or off for the frequency converter 3 of the three-level topology structure through the optical fiber 8. The speed feedback signal of the system is calculated by the encoder 11, and the phase voltage is obtained by the simplified three-level phase voltage reconstruction algorithm of this aspect.

Claims (1)

1. simplified phase-voltage reconstruction method of three-level converter is characterized in that this reconstructing method specific implementation process is:

The first step: at first to the DC bus-bar voltage V of frequency converter _DcSample, and the record result;

Second step: according to the three dimensional vector diagram of three-level converter, the three dimensional vector diagram of three-level converter, formed, calculate T action time of A, B, C phase thus by the little hexagon that six two traditional level space vectors constitute _a, T _b, T _c, the while is at the subcarrier time T of system _sCarry out the phase voltage V of A, B, C phase under the two level topological structures _An, V _Bn, V _CnThe calculating of reconstruct,

$V_{\mathrm{an}}=V_{\mathrm{dc}}(\frac{2}{3}{T}_a-\frac{1}{3}{T}_b-\frac{1}{3}{T}_c)/T_s$

$V_{\mathrm{bn}}=V_{\mathrm{dc}}(\frac{2}{3}{T}_b-\frac{1}{3}{T}_a-\frac{1}{3}{T}_c)/T_s$

$V_{\mathrm{cn}}=V_{\mathrm{dc}}(\frac{2}{3}{T}_c-\frac{1}{3}{T}_b-\frac{1}{3}{T}_a)/T_s,$

The 3rd step: for the reconstruct of output phase voltage down of three level topological structures, utilize coordinate translation, it is to carry out in the little hexagon at center that the voltage vector that needs reconstruct is positioned at respectively with V1, V2, V3, V4, V5, V6, and each little hexagon just can be regarded the space voltage vector figure of one two level topological structure as; And then each little hexagonal center component on A, B, C axle measured by way of compensation, be added on the result who produces with phase-voltage reconstruction under the two level topological structures,

$V_{\mathrm{an}}^{\&prime;}=V_{\mathrm{dc}}(\frac{2}{3}{T}_a-\frac{1}{3}{T}_b-\frac{1}{3}{T}_c)/T_s+V_{a\_\mathrm{compensation}}$

$V_{\mathrm{bn}}^{\&prime;}=V_{\mathrm{dc}}(\frac{2}{3}{T}_b-\frac{1}{3}{T}_a-\frac{1}{3}{T}_c)/T_s+V_{b\_\mathrm{compensation}}$

$V_{\mathrm{cn}}^{\&prime;}=V_{\mathrm{dc}}(\frac{2}{3}{T}_c-\frac{1}{3}{T}_b-\frac{1}{3}{T}_a)/T_s+V_{c\_\mathrm{compensation}},$

According to the different little hexagon that reference voltage vector is positioned, the compensation rate that obtains A, B under each situation, C phase is as follows:

Little hexagon number A phase compensation rate V _{a_compensation} B phase compensation rate V _{b_compensation} C phase compensation rate V _{c_compensation} ??1 ??+V _dc/3 ??-V _dc/6 ??-V _dc/6 ??2 ??+V _dc/6 ??+V _dc/6 ??-V _dc/3 ??3 ??-V _dc/6 ??+V _dc/3 ??-V _dc/6 ??4 ??-V _dc/3 ??+V _dc/6 ??+V _dc/6 ??5 ??-V _dc/6 ??-V _dc/6 ??+V _dc/3 ??6 ??+V _dc/6 ??-V _dc/3 ??+V _dc/6 。

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