Control method of Vienna rectifier under power grid imbalance

A technology of power grid imbalance and control method, which is applied in the direction of electrical components, high-efficiency power electronic conversion, output power conversion device, etc., can solve the problems of output voltage secondary ripple, rectifier input current distortion, etc., and achieve simple control method, beneficial effect

Active Publication Date: 2021-10-01

NANJING UNIV OF AERONAUTICS & ASTRONAUTICS

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AI-Extracted Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to realize the operation control of the Vienna rectifier under the unbalanced power grid, solve the proble...

Abstract

The invention relates to a control method of a Vienna rectifier under power grid imbalance, and belongs to the field of electric energy conversion. The method mainly comprises the steps of calculation of a power grid orthogonal signal and a power grid frequency, calculation of a current reference value under an unbalanced power grid, control over a Vienna rectifier under an unbalanced aviation wide frequency conversion power grid, and suppression of input current harmonic waves and output voltage fluctuation of the Vienna rectifier. Aiming at the rectifier, the method provided by the invention provides a new control strategy for the three-phase rectifier due to the fact that the current methods applied to the aviation wide frequency conversion power grid for controlling the rectifier under the three-phase imbalance are few. According to the invention, a three-phase phase-locked loop and power grid positive and negative sequence component calculation are not needed, the control algorithm is simple, the method is suitable for an aviation wide frequency conversion power grid with the frequency changing in the range of 360-800 Hz, and it can be guaranteed that the Vienna rectifier maintains high-power-factor operation and stable direct current output voltage under the working condition that the power grid is unbalanced.

Application Domain

Efficient power electronics conversionAc-dc conversion

Technology Topic

Power gridRectiformer +12

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Examples

Experimental program(3)

Example Embodiment

[0046] Example 1:

[0047] figure 1 The VIENNA rectifier topology applying the present invention is shown in the figure. a , V b , V c Three-phase input voltage, L a L b L c Inspiration, D 1 ~ D 6 Diode, s 1 ~ S 6 Switching tube, C 1 , C 2 For output capacitance, R 0 Load.

[0048] figure 2 The schematic diagram of the VIENNA rectifier control method is shown in the power grid of the present invention. In this embodiment, the VIENNA rectifier switching frequency is 200KHz, the sampling frequency of the DSP digital controller is 100KHz, and the runtime control step includes the following parts:

[0049] 1) DSP digital controller sampling grid VIENNA rectifier three-phase input voltage signal V a , V b , V c , Three-phase input current signal I a I b I c And output voltage signal V dc.

[0050] 2) Triangular input voltage signal V a , V b , V c pass through image 3 The second-order general integrator with the locking ring structure is calculated to obtain a three-phase input voltage orthogonal signal QV with a phase shift 90 °. a , QV b , QV c And the grid frequency Ω.

[0051] 3) Put the output voltage reference value V dc_ref Substate the sampled output voltage V dc , Obtain the error between the output voltage and the actual value, feed the error feed ratio-integral regulator, constitute the voltage rings of the VIENNA rectifier, the output of the voltage ring is k m.

[0052] 4) Output of the voltage ring m Orthogonal signal QV with three-phase input voltage a , QV b , QV c According to the formula (1) ~ (3), the three-phase current reference value I is obtained. a_ref I b_ref I c_ref.

[0053] i a_ref = K m (-qv b + QV c ) (1)

[0054] i b_ref = K m (-qv c + QV a ) (2)

[0055] i c_ref = K m (-qv a + QV b ) (3)

[0056] 5) Put the current reference value i a_ref I b_ref I c_ref Sampling signal I a I b I c Error feed Figure 4 The quasi-resonance regulator shown, the calculated grid frequency ω as the resonant frequency of the quasi-a-resonant regulator, constitutes the current rings of the Vienna rectifier.

[0057] 6) Output of the VIENNA rectifier current ring a U b U c Summary zero sequence component U offset Thus, three-phase modulation wave u x,offset , Zero sequence component U offset Modulated with three-phase modulation wave u x,offset The expression is as shown in the formula (4), (5):

[0058]

[0059] U x,offset = U x + U offset , X = a, b, c (5)

[0060] Where u offset For zero-order components, used to increase the modulation ratio of the rectifier, u max U min Three-phase modulation wave u x,offset The maximum and minimum values are obtained by comparing the three-phase modulation wave value.

[0061] 7) Wave U x,offset Acceptance with the triangular carrier to get the on-time T at the switch tube x,on , The on-time expression is as shown in the formula (7):

[0062]

[0063] The intercourse of modulation wave and carrier needs to decide according to the positive and negative decision of the modulated wave, when the adjustment wave is a squares, the same direction carrier is intercured, such as Figure 5 The reverse carrier is intercured when the adjustment wave is negative half a week, such as Image 6 Indicated.

[0064] 8) A three-phase duty cycle signal D is obtained according to the on-time on the switch tube. a , D b , D c , Send the PWM module of the digital controller output three-phase drive signal to achieve the control of the rectifier.

[0065] The technical solution of the present invention is not limited to the above-described embodiments, and the technical solution obtained by equivalent replacement is all within the scope of the present invention.

[0066] In order to verify the superiority and feasibility of the present invention, the VIENNA rectifier control method proposed under the power grid inbalance proposed by the present invention is simulated and experimental verification by constructing simulation model and experimental prototype.

Example Embodiment

[0067] Simulation Example 1:

[0068] The VIENNA rectifier control method is used with the grid imbalance of the present embodiment, and the simulation model is built on the PLECS simulation software, and the VIENNA rectifier of the aviation application is simulated. The steps are as follows:

[0069] 1) Set the input voltage effective value a phase 103V, B-phase 115V, C-phase 126V, three-phase voltage exist of 10% imbalance, input voltage frequency 400Hz, output voltage 360V, output power 4.5 kW, switch frequency 200kHz, sampling frequency 100kHz, input inductance 150μH, output capacitor 440μF.

[0070] 2) Using conventional voltage current double loop Pi control, by Figure 7 It can be known that the rectifier input current is distortion, and the input current has a total harmonic distortion rate (THD) to 4.89%, and the output voltage has a secondary ripple of about 6V.

[0071] 3) The method of controlling the proposed grid imbalance, by Figure 8 It can be known that the rectifier input current harmonic content is greatly reduced, THD is 1.6%, and the secondary ripple of the output voltage is suppressed.

[0072] 4) Set at 0.1s Time The power network frequency is hopped from 400 Hz to 420 Hz. Figure 9 It can be seen that the input current is adjusted after approximately 20 ms, and the input current is high before and after the frequency change is high, and the output voltage is stable.

[0073] 5) Resetting the grid frequency is 800 Hz, the remaining circuit parameters are unchanged, set 0.1s Time The power network frequency is hopped by 800Hz to 780 Hz, by Figure 10 It can be seen that the input current is adjusted after approximately 15 ms, and the input current is high before and after the frequency change is high, and the output voltage is stable.

[0074] It can be seen from the simulation results that the control method of the present invention can suppress the VIENNA rectifier input current harmonics and output voltage secondary ripples in three phase imbalance inputs, and the control effect can still be maintained when the grid frequency changes.

Example

[0075] Experiment example 1:

[0076] The VIENNA rectifier control method is performed by the grid imbalance of the present embodiment, and experimental verification is performed by 4.5 kW Air Vienna Rectifier prototype platform. The steps are as follows:

[0077] 1) Set the three-phase input source input voltage effective value a phase 103V, the B phase 115V, the C-phase 126V, the three-phase voltage exists, the input voltage frequency is 400 Hz, the output voltage is 360V, the output power is 4.5 kW, the switching frequency is 200KHz , The sampling frequency is 100KHz, input inductance 150μH, output capacitor 440μF.

[0078] 2) Using conventional voltage current double loop Pi control, by Figure 11 It can be known that the rectifier input current is distortion, and the input current has a total harmonic distortion (THD) to 8.54%, and the output voltage has a secondary ripple of about 3.5V.

[0079] 3) The method of controlling the proposed grid imbalance, by Figure 12 It can be known that the rectifier input current harmonic content is greatly reduced, THD is 4.75%, and the secondary ripple of the output voltage is suppressed.

[0080] 4) Set the three-phase source input frequency from 400 Hz to 420 Hz, by Figure 13 It can be seen that the input current returns to stabilize after approximately 5 ms.

[0081] 5) Set the three-phase source input frequency by 800 Hz to 780 Hz, by Figure 14 It can be seen that the input current is adjusted after approximately 4.35 ms to resume stability.

[0082] It can be seen from the experimental results that the method of controlling the VIENNA rectifier input current harmonic and output voltage secondary ripple can be suppressed under three-phase imbalance input, and the control effect can still be maintained when the power grid frequency changes.

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Classification and recommendation of technical efficacy words

Simple control method
conducive to realization

Control method of Vienna rectifier under power grid imbalance

AI-Extracted Technical Summary

Problems solved by technology

Abstract

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Examples

Example Embodiment

Example Embodiment

Example

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Description & Claims & Application Information

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