CN102255530A - Three-phase PWM (Pulse-Width Modulation) rectifying device based on predictive current control - Google Patents

Abstract

The invention relates to a three-phase PWM (Pulse-Width Modulation) rectifying device based on predictive current control and belongs to the technical field of an alternated current of power electronics. The invention provides a three-phase PWM rectifying device, a control system of which is realized by a DSP (Digital Signal Processor). The three-phase PWM rectifying device mainly comprises a predictive current controller, a digital PI (Proportional Integral) regulator, a main circuit, an alternated voltage sampling regulating circuit and an alternated current sampling regulating circuit. The predictive current control under a two-phase static coordinate is adopted in the three-phase PWM rectifying device; the PI regulator is taken as an outer voltage ring; an output value of the PI regulator is an amplitude value of a three-phase command current; after the amplitude value of a command current is multiplied by an input alternated voltage phase signal of a power grid, the command current is acquired; and then the command current is subjected to 3/2 conversion, thereby acquiring the command current under a two-phase (alpha-beta) static coordinate; and a command voltage at input side of a rectifier is calculated.

Description

A kind of three-phase PWM rectifying device based on predicted current control

Technical field the present invention relates to a kind of three-phase PWM rectifying device based on predicted current control, belongs to power electronics and exchanges technical field.

Background technology is at present in the application of power electronics, most convertor assemblys have all adopted PWM rectification link, and the key of PWM rectifier systems is the control to electric current, and Current Control Strategy mainly is divided into two kinds, a kind of is indirect current control, and another is a Direct Current Control.Indirect current control, promptly the width of cloth is controlled mutually, and the proposition time is not early introduced the ac-side current sampled value in control structure, and calculates modulation voltage according to AC side voltage, thereby controls ac-side current indirectly.Direct Current Control is promptly introduced the ac-side current sampling in control structure, compares with current reference value, and the structure current closed-loop, thus can improve the precision of Current Control and the response speed of system.The current closed-loop form of Direct Current Control mainly contain stagnate chain rate and PI regulate two kinds, this is extensive a kind of control strategy of employing at present.

The PWM rectifier not only can realize that the rectifier output voltage of rectifier is adjustable within the specific limits, and can make the sineization of current on line side, and net side power factor is adjustable.Therefore, the PWM rectifier is the focus of studying in the field of power electronics at present.

And these rectification link great majority employings is controlled rectification source or the uncontrollable rectification source that power electronic device constitutes, so just inevitably brought pollution to electrical network, mainly be because electrical network has been injected a large amount of current harmonicss, and reduced the power factor of electrical network.

Summary of the invention is in order to address the above problem, and the invention reside in provides a kind of three-phase PWM rectifying device based on predicted current control.

The present invention includes the Three-Phase PWM Rectifier device, control system adopts digital signal processor DSP to realize, mainly comprises predicted current control, digital pi regulator, main circuit, alternating voltage sampling modulate circuit and alternating current sampling modulate circuit.

The present invention adopts the predicted current control under the two-phase rest frame, outer voltage adopts pi regulator, its output valve is the amplitude of three-phase instruction current, after multiplying each other, the amplitude of instruction current and electrical network input ac voltage phase signal obtain instruction current, obtain instruction current under two-phase (alpha-beta) rest frame through 3/2 conversion again, by calculating the command voltage of input side rectifier.

The main circuit of above-mentioned Three-Phase PWM Rectifier has adopted six switch three-phase half bridge circuit topologys, and device for power switching has been selected IGBT.

Above-mentioned alternating voltage sampling modulate circuit and alternating current sampling modulate circuit, alternating voltage and current signal obtain sampled signal by voltage sensor and current sensor respectively, voltage signal and current signal amplify (dwindling) by voltage regulation one-level amplifier respectively and handle and electric current first order amplifier is amplified (dwindling) and handled then, pass through the voltage signal that voltage regulation secondary amplifier and electric current second level amplifier are converted to sampled signal DSP acceptable 0～3.3V again.

Advantage of the present invention: the present invention has adopted the predicted current control under the two-phase rest frame, can obtain simple method for designing.Because the component of correlative on α, β axle is separate, realized decoupling zero, so control algolithm is simple, is easy to Digital Realization.

Description of drawings

Fig. 1 is main circuit topology figure of the present invention;

Fig. 2 is alternating voltage sampling modulate circuit;

Fig. 3 is alternating current sampling modulate circuit;

Fig. 4 is an electrical schematic diagram of the present invention.

Among the figure; 1, predicted current control, 2, digital pi regulator, 3, voltage sensor, 4, the computing of alternating voltage one-level is amplified, and 5, the computing of alternating voltage secondary amplifies, 6, current sensor, 7, the computing of alternating current one-level is amplified, and 8, the computing of alternating current secondary amplifies, 9, main circuit.

Embodiment

The Three-Phase PWM Rectifier device adopts the predicted current control 1 under the two-phase rest frame, outer voltage adopts digital pi regulator 2, its output valve is the amplitude of three-phase instruction current, after multiplying each other, the amplitude of instruction current and electrical network input ac voltage phase signal obtain instruction current, obtain instruction current under two-phase (alpha-beta) rest frame through 3/2 conversion again, by calculating the command voltage of input side rectifier.Implementation procedure is as follows:

Accompanying drawing 1 is the main circuit topology figure of three phase rectifier device, and by the mathematical analysis to main circuit topology, it is as follows to obtain three-phase (a-b-c) rest frame equation:

$\left\{\begin{array}{c}{U}_{\mathrm{AO}}=e_a-(L\frac{{\mathrm{di}}_a}{\mathrm{dt}}+{\mathrm{Ri}}_a)\\ U_{\mathrm{BO}}=e_b-(L\frac{{\mathrm{di}}_b}{\mathrm{dt}}+{\mathrm{Ri}}_b)\\ U_{\mathrm{CO}}=e_c-(L\frac{{\mathrm{di}}_c}{\mathrm{dt}}+{\mathrm{Ri}}_c)\end{array}\right.---\left(1\right)$

Adopt transformation matrix (2), the three-phase system under three-phase (a-b-c) rest frame is transformed in two-phase (alpha-beta) rest frame.

$T_{\mathrm{\α\β}/\mathrm{abc}}=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]---\left(2\right)$

Formula (3) is the equation of system in two-phase (alpha-beta) coordinate system:

$\left\{\begin{array}{c}{U}_{\mathrm{\α}}=e_{\mathrm{\α}}-(L\frac{{\mathrm{di}}_{\mathrm{\α}}}{\mathrm{dt}}+{\mathrm{Ri}}_{\mathrm{\α}})\\ U_{\mathrm{\β}}=e_{\mathrm{\β}}-(L\frac{{\mathrm{di}}_{\mathrm{\β}}}{\mathrm{dt}}+{\mathrm{Ri}}_{\mathrm{\β}})\end{array}\right.---\left(3\right)$

From formula (3) as can be seen, by control U _α, U _βValue, can change alternating current i _α, i _β, each is measured at (t to formula (3) _k, t _K+1) average in the time interval, can obtain:

${\stackrel{\‾}{U}}_{\mathrm{\α}}={\stackrel{\‾}{e}}_{\mathrm{\α}}-\frac{1}{T_S}{\∫}_{t_k}^{t_{k+1}}(L\frac{{\mathrm{di}}_{\mathrm{\α}}}{\mathrm{dt}}+{\mathrm{Ri}}_{\mathrm{\α}})\mathrm{dt}$

$={\stackrel{\‾}{e}}_{\mathrm{\α}}-\frac{L}{T_S}[i_{\mathrm{\α}}\left(t_{k+1}\right)-i_{\mathrm{\α}}\left(t_k\right)]-\frac{R}{T_S}{\∫}_{t_k}^{t_{k+1}}{i}_{\mathrm{\α}}\mathrm{dt}---\left(4\right)$

${\stackrel{\‾}{U}}_{\mathrm{\β}}={\stackrel{\‾}{e}}_{\mathrm{\β}}-\frac{1}{T_S}{\∫}_{t_k}^{t_{k+1}}(L\frac{{\mathrm{di}}_{\mathrm{\β}}}{\mathrm{dt}}+{\mathrm{Ri}}_{\mathrm{\β}})\mathrm{dt}$

$={\stackrel{\‾}{e}}_{\mathrm{\β}}-\frac{L}{T_S}[i_{\mathrm{\β}}\left(t_{k+1}\right)-i_{\mathrm{\β}}\left(t_k\right)]-\frac{R}{T_S}{\∫}_{t_k}^{t_{k+1}}{i}_{\mathrm{\β}}\mathrm{dt}---\left(5\right)$

With

Be respectively (U _α, U _β) and (e _α, e _β) at the mean value of a control cycle, T _S=t _K+1-t _kSuppose under the situation of negligible resistance R, in the one-period

Be equivalent to command voltage

Then have:

$\left\{\begin{array}{c}{U}_{\mathrm{\α}}^{*}={\stackrel{\‾}{e}}_{\mathrm{\α}}-\frac{L}{T_S}{[i}_{\mathrm{\α}}\left(t_{k+1}\right)-i_{\mathrm{\α}}\left(t_k\right)]\\ U_{\mathrm{\β}}^{*}\text{=}{\stackrel{\‾}{e}}_{\mathrm{\β}}-\frac{L}{T_S}[i_{\mathrm{\β}}\left(t_{k+1}\right)-i_{\mathrm{\β}}\left(t_k\right)]\end{array}\right.---\left(6\right)$

Suppose that in one-period net side actual current can the trace command electric current, then has

With

Formula (6) can be write as:

$\left\{\begin{array}{c}{U}_{\mathrm{\α}}^{*}={\stackrel{\‾}{e}}_{\mathrm{\α}}-\frac{L}{T_S}{{[i}_{\mathrm{\α}}}^{*}\left(t_{k+1}\right)-i_{\mathrm{\α}}\left(t_k\right)]\\ U_{\mathrm{\β}}^{*}\text{=}{\stackrel{\‾}{e}}_{\mathrm{\β}}-\frac{L}{T_S}[{i_{\mathrm{\β}}}^{*}\left(t_{k+1}\right)-i_{\mathrm{\β}}\left(t_k\right)]\end{array}\right.---\left(7\right)$

α in the following formula, the β component has been realized decoupling zero.

Be the command voltage that be applied to the power model input side, adjust main circuit power switch state, thereby realize the PWM rectifier function according to the command voltage value.

The main circuit of Three-Phase PWM Rectifier has adopted six switch three-phase half bridge circuit topologys, its structure as shown in Figure 1, device for power switching has been selected IGBT.

Accompanying drawing 2 and accompanying drawing 3 are respectively alternating voltage sampling modulate circuit and alternating current sampling modulate circuit, alternating voltage and current signal obtain sampled signal by voltage sensor 3 and current sensor 6 respectively, amplify 4 (dwindling) and alternating current one-level computing amplification 7 processing by the computing of alternating voltage one-level respectively then, process, alternating voltage secondary computing amplification 5 and the computing of alternating current secondary amplify 8 respectively again, and second level amplifier is converted to sampled signal the voltage signal of DSP acceptable 0～3.3V.

Predicted current control 1 among Fig. 4, outer voltage adopts digital pi regulator 2, predicted current control 1 and digital pi regulator 2 control main circuits 9.

Claims (7)

1. three-phase PWM rectifying device based on predicted current control, comprise Three-Phase PWM Rectifier device and control system, control system mainly comprises predicted current control (1), digital pi regulator (2), main circuit (9), alternating voltage sampling modulate circuit and alternating current sampling modulate circuit.

2. a kind of three-phase PWM rectifying device based on predicted current control according to claim 1, control system adopts digital signal processor DSP to realize.

3. a kind of three-phase PWM rectifying device according to claim 1 based on predicted current control, wherein alternating voltage sampling modulate circuit comprises voltage sensor (3), (4) are amplified in the computing of alternating voltage one-level and (5) are amplified in the computing of alternating voltage secondary.

4. a kind of three-phase PWM rectifying device based on predicted current control according to claim 1, wherein alternating current sampling modulate circuit comprises that (7) are amplified in current sensor (6), the computing of alternating current one-level, (8) are amplified in the computing of alternating current secondary.

5. a kind of three-phase PWM rectifying device according to claim 1 based on predicted current control, wherein main circuit (9) has adopted six switch three-phase half bridge circuit topologys, and device for power switching has been selected IGBT.

6. a kind of three-phase PWM rectifying device according to claim 1 based on predicted current control, wherein in the alternating voltage sampling modulate circuit, alternating voltage obtains sampled signal by voltage sensor (3), amplify (4) by the computing of alternating voltage one-level then and handle, the voltage signal that (5) are converted to sampled signal DSP acceptable 0～3.3V is amplified in computing through the alternating voltage secondary again.

7. a kind of three-phase PWM rectifying device according to claim 1 based on predicted current control, wherein in the alternating current sampling modulate circuit, alternating current obtains sampled signal by current sensor (6), then by after alternating current one-level computing amplification (7), the alternating current secondary computing amplification (8) sampled signal being converted to the voltage signal of DSP acceptable 0～3.3V.

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