CN103078526B - Current source type rectifier and grid-connected control method based on virtual resistor - Google Patents

Abstract

The invention discloses a grid-connected control method of a current source type PWM rectifier based on a virtual resistance. The grid-connected rectifier consists of mains power, an AC filter inductor, an AC filter capacitor, a three-phase current source type rectifier bridge, a DC inductor, a DC capacitor and Composition of digital controllers. The sampled AC filter capacitor voltage is sent to the microprocessor for digital phase locking, and the AC filter capacitor voltage and phase are sent to the AC controller after the phase locking is completed. The AC current controller consists of a coordinate transformer, a virtual impedance regulator and a divider. The coordinate converter converts the voltage of the three-phase AC filter capacitor into the voltage in the two-phase static coordinate system, obtains the current flowing through the virtual resistance after passing through the virtual resistance regulator, and then obtains the control value of the AC side through the divider, and superimposes it to On the control quantity of the DC side, the drive signal is obtained by the PWM generator and then sent to the driver board, and the signal is amplified by the driver board to control the on-off of the three-phase current source type rectifier bridge switch tube. The virtual resistance regulator in the AC current controller is equivalent to directly paralleling the resistance on the AC capacitor in terms of control effect, which can effectively damp the oscillation, but without loss, and can effectively suppress the higher harmonics in the grid-connected current . The rectifier has fast and stable dynamic response, high power factor and low total harmonic distortion rate of grid-connected current, and can be applied to uninterruptible power supply.

Description

Current source rectifier and grid-connected control method based on virtual resistance

technical field

The invention relates to a control method for stably controlling a current source rectifier and realizing a low total harmonic distortion rate of grid-connected current, belonging to the field of rectifier control methods.

Background technique

The traditional UPS power supply usually uses a phase-controlled rectifier, and the DC bus voltage is about 400V. However, due to its low power factor and heavy pollution to the power grid, it has been gradually replaced by high-frequency PWM rectifiers based on full-control devices. High-frequency PWM rectifiers are divided into two types: voltage source type and current source type. Among them, the DC bus voltage required by the current source type PWM rectifier is lower than the peak-to-peak voltage of the AC side voltage. Therefore, when the DC bus voltage is about 400V, use the current source The type PWM converter can complete the upgrading of UPS at a lower cost under the premise of maintaining the existing DC bus voltage and the rear inverter, and it is also a good choice for a new generation of high-power UPS.

Since the AC side of the current source rectifier uses inductance-capacitor filtering, it is easy to generate resonance on the AC side, which affects the waveform of the grid-connected current and may cause shutdown. Compared with the voltage source rectifier, the transient model of the current source rectifier has high order, strong coupling, and has nonlinear characteristics. It is difficult to use the direct current control and indirect current control of the voltage source rectifier in the current source rectifier. apply directly. The nonlinear control method solves the problem of strong nonlinear coupling of the current source rectifier in theory. The AC side can be damped through closed-loop control, but the control performance is highly dependent on the system parameters and is sensitive to parameter changes. Implement complex.

In theory, connecting a resistor in parallel with the AC filter capacitor is the simplest and most effective way to suppress oscillation, but it cannot be practically applied because the resistor will generate power consumption.

Contents of the invention

The present invention aims at the deficiencies of the prior art. On the basis of the closed-loop control of the DC side of the current source rectifier, it proposes an active damping control technology that realizes the virtual resistance through the feedback control of the AC quantity on the AC side, which can effectively suppress The resonance of the inductor-capacitor filter on the AC side reduces the total harmonic distortion rate of the grid-connected current without affecting the stability and dynamic response characteristics of the DC side.

The virtual resistance-based current source rectifier of the present invention is composed of a rectifier bridge, a microprocessor and a rectifier bridge power device drive unit, and the rectifier bridge communicates with the microprocessor through the rectifier bridge power device drive unit; The AC side of the rectifier bridge is equipped with an AC filter inductor, AC filter capacitor and AC side voltage sensor in sequence; the DC side of the rectifier bridge is equipped with a DC inductor, a DC voltage stabilizing capacitor, a DC voltage detection unit and a DC current detection unit.

The microprocessor is sequentially equipped with a phase-locked loop, a DC voltage controller, an AC current controller, an adder and a space vector PWM pulse generating unit.

The AC current controller includes a coordinate transformation unit, a d-axis virtual resistance regulator, a q-axis virtual resistance regulator and a divider.

Further, the virtual resistance regulator includes a high-pass filter and a virtual conductance link.

The control method for suppressing resonance and reducing the total harmonic distortion rate of grid-connected current by using the virtual resistance-based current source rectifier device is as follows:

Step 1: After the rectifier is powered on, the microprocessor blocks the pulse, and the AC side voltage sensor of the rectifier bridge detects the AC filter capacitor voltages u _a , _ub and _uc , and the microprocessor samples the voltages and performs phase-locking to obtain them The phase of the AC filter capacitor voltage;

Step 2: The DC voltage detection unit and the DC current detection unit on the DC side of the rectifier bridge detect the voltage and current of the DC side. After the microprocessor samples the voltage and current, it is compared with the DC voltage given u _ref as the microprocessor The input of the internal DC voltage controller is used to calculate the control value of the DC side. The calculation method of the control quantity is as follows:

u _err = u _ref - u _o (1)

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; otemp</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}}{\mathrm{<span\; class="notranslate">\; 311</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; err</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2.2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 311</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1.9</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}}{\mathrm{<span\; class="notranslate">\; 311</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; dc</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, v _o and v _otemp are intermediate variables in the calculation process, T _s is the sampling frequency, L _dc and C _dc are the values of the DC inductance and DC voltage stabilizing capacitor respectively, and ω _n is the undamped oscillation of the modified DC side system Generally, the frequency is slightly higher than the resonant frequency of the inductor and capacitor on the DC side.

Step 3: the coordinate transformation unit in the ac current controller transforms the ac filter capacitor voltages u _a , u _b and _uc in the three-phase stationary coordinate system into voltages u _d and u in the two-phase rotating coordinate system through coordinate transformation _q , u _d and u _q are calculated as:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<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>$

Then u _d and u _q are respectively used as the input of the d-axis and q-axis virtual impedance regulators. The d-axis and q-axis virtual resistance regulators are both composed of a high-pass filter s/(s+ω _HP ) and a conductance link 1/ R _H constitutes, where ω _HP is the corner frequency of the high-pass filter, R _H is the virtual resistance that needs to be realized in parallel with the AC filter capacitor, and the digital algorithm implementations of the d-axis and q-axis virtual resistance regulators in the microprocessor are respectively:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; dDamp</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</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">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; HP</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; dDamp</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; HP</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; h</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">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; qDamp</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</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">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; HP</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; qDamp</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; HP</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; h</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>$

Among them, u _d (k), u _q (k) are the input of the current beat of the d-axis and q-axis virtual resistance regulator respectively; _dDamp (k), I _qDamp (k) are the output of the current beat of the virtual resistance adjuster; u _d (k-1), u _q (k-1) are the input of the last beat of the virtual resistance regulator, and the initial value is 0; I _dDamp (k-1), I _qDamp (k-1) are the The output of one beat has an initial value of 0; T _s is the sampling interval time, and the output of the virtual resistance regulator is divided by the DC bus current by the divider to obtain the control quantity.

Step 4: Use an adder to add the control quantity of the AC side and the control quantity of the DC side to obtain the total control quantity, and then generate a space vector PWM pulse through the space vector PWM pulse generation unit, and the microprocessor releases the pulse blockade, and the output of the microprocessor The PWM pulse is amplified by the drive unit of the rectifier bridge power device to control the on-off of each tube of the rectifier bridge. As the given voltage rises slowly, the rectifier device starts smoothly.

The beneficial effect of the present invention is that: the present invention proposes a control method for current source rectifiers to suppress resonance and reduce the total harmonic distortion rate of grid-connected current without increasing hardware costs and wasting energy. Through the above-mentioned digital control algorithm, It is equivalent to connecting a resistor in parallel with the capacitor on the AC side, which can effectively suppress the resonance of the inductor and capacitor on the AC side, and reduce the total harmonic distortion rate of the grid-connected current without affecting the stability and dynamic response characteristics of the DC side. Convenient and effective.

Description of drawings

Fig. 1 is a simplified circuit diagram of a current source rectifier device based on a virtual resistance;

Fig. 2 is the main circuit part of the current source type rectifier device;

Figure 3 is a control block diagram of active damping using virtual resistors;

Figure 4 is a schematic diagram of a current source type device using passive damping;

Fig. 5 is a schematic diagram of a current source type device using a virtual resistor;

In the figure: 1. Rectifier bridge; 2. AC filter capacitor; 3. AC side voltage sensor; 4. AC filter inductor; 5. Mains grid; 6. DC inductor; 7. DC current detection unit; 8. DC voltage regulator Capacitance; 9. DC voltage detection unit; 10. Load; 11. Microprocessor; 12. Rectifier bridge power device drive unit; 13. DC voltage controller; 14. Phase-locked loop; 15. AC current controller; 16. Adder; 17. Space vector PWM pulse generating unit; 18. Coordinate converter; 19. d-axis virtual resistance regulator; 20. q-axis virtual resistance regulator; 21. Divider.

Detailed ways

As shown in Fig. 1, the current source type rectifier based on the virtual resistance of the present invention is: composed of a rectifier bridge 1, a microprocessor 11 and a rectifier bridge power device drive unit 12, and the described rectifier bridge 1 is driven by a rectifier bridge power device The unit 12 is connected and communicated with the microprocessor 11; the AC filter capacitor 2, the AC side voltage sensor 3 and the AC filter inductor 4 are sequentially arranged on the AC side of the rectifier bridge 1, and the AC filter inductor 4 is connected to the mains grid 5; The DC side is equipped with a DC inductor 6 , a DC current detection unit 7 , a DC voltage stabilization capacitor 8 and a DC voltage detection unit 9 , and the DC voltage stabilization capacitor 8 is followed by a load 10 . The main circuit part of the current source rectifier device is shown in Fig. 2 .

The microprocessor 11 includes a DC voltage controller 13 , a phase-locked loop 14 , an AC current controller 15 , an adder 16 and a space vector PWM pulse generating unit 17 .

The AC controller 15 includes a coordinate converter 18 , a d-axis virtual resistance adjuster 19 , a q-axis virtual resistance adjuster 20 and a divider 21 .

The method for realizing network control by using the virtual resistance-based current source rectifier of the present invention is as follows: after the rectifier is powered on, the AC side voltage sensor 3, the DC current detection unit 7 and the DC voltage detection unit 9 start to detect the AC filter capacitance respectively The voltages u _a , u _b , u _c as well as the DC link current and the DC link voltage. The microprocessor 11 samples the signals detected by the detection unit to obtain the digital quantities of each signal in the microprocessor. Use the phase-locked loop 14 to phase-lock the AC filter capacitor voltages u _a , _ub and _uc to obtain the phase θ of the AC filter capacitor voltage. The DC bus current, the DC bus voltage and the given DC voltage u _ref are used as the input of the DC voltage controller 13 to calculate the control quantity of the DC side. The calculation method of the control quantity on the DC side is shown in formulas (1), (2) and (3). The AC filter capacitor voltages u _a , _ub , _uc and phase θ are used as the input of the AC controller 15 to calculate the control quantity of the AC side. The DC side control quantity and the AC side control quantity are added by the adder 16 to obtain the total control quantity, and the total control quantity is used as the input of the space vector PWM pulse generating unit 17, and the PWM pulse is obtained after modulation. The microprocessor 11 starts to output PWM pulses after unlocking the pulse blockade, and the PWM pulses are amplified by the rectifier bridge power device drive unit 12 to control the on-off of each tube of the rectifier bridge 1, and the rectifier starts to work. As the given voltage increases slowly, the DC device starts up smoothly.

The specific process of the AC controller is as follows: through the coordinate converter 18, the AC filter capacitor voltages u _a , u _b and u _c in the three-phase stationary coordinate system are transformed into voltages u _d and u _q in the two-phase rotating coordinate system .

U _d and u _q are respectively used as the inputs of the d-axis virtual resistance adjuster 19 and the q-axis virtual resistance adjuster 20 . The control principle block diagram of active damping using virtual resistance is shown in Figure 3. The virtual resistance regulator in the dotted line box in the figure is composed of a high-pass filter s/(s+ω _HP ) and a conductance link 1/R _H , where ω _HP is the corner frequency of the high-pass filter, and R _H is the virtual resistance that needs to be realized in parallel with the AC filter capacitor. The digital algorithm implementation of the virtual resistance regulator in the microprocessor is shown in formulas (5) and (6), and its effect is equivalent to adding a resistor beside the AC filter capacitor, as shown in Figure 4.

In the formula, u _d (k), u _q (k) are the current beat input of the virtual resistance adjuster; I _dDamp (k), I _qDamp (k) are the current beat output of the virtual resistance adjuster; u _d (k-1 ), u _q (k-1) is the input of the last beat of the virtual resistance regulator, the initial value is 0; I _dDamp (k-1), I _qDamp (k-1) is the output of the last beat of the virtual resistance regulator , the initial value is 0; T _s is the sampling interval time. The output of the virtual resistance regulator is divided by the DC bus current by the divider 21 to obtain the control value of the AC side. The AC modulation value controls the on-off of the rectifier bridge switch tube, and the bridge arm flows through an additional current I _kDamp (k), as shown in Figure 5, which realizes the introduction of virtual resistance.

The solution described in the present invention is based on the closed-loop control of the DC side of the rectifier device, and performs an open-loop control based on active damping on the AC side, thereby realizing the suppression of the filter resonance on the AC side and the improvement of the total harmonic distortion rate of the grid-connected current. decrease without affecting the steady-state characteristics and dynamic response of the DC side.

Claims (1)

1. based on the current source type rectifier of virtual resistance, be made up of rectifier bridge, microprocessor and rectifier bridge power device driver element, described rectifier bridge is connected with microprocessor is communicated by rectifier bridge power device driver element; The AC of described rectifier bridge is configured with ac filter inductance, ac filter electric capacity and AC voltage sensor successively; DC inductance, DC voltage-stabilizing electric capacity, direct voltage detecting unit and direct current detection unit is configured with in the DC side of rectifier bridge; Ac filter electric capacity is parallel with virtual resistance;

Phase-locked loop, DC voltage controller, AC current control device, adder and space vector PWM pulse generate unit is equipped with successively in described microprocessor;

Coordinate transformation unit, d axle virtual resistance adjuster, q axle virtual resistance adjuster and divider is had in described AC current control device;

Described virtual resistance adjuster comprises high pass filter and virtual conductance link; It is characterized in that:

Current source type rectifier based on virtual resistance realizes suppressing resonance and the control method reducing grid-connected current total harmonic distortion factor is:

The first step: rectifier powers on after start, microprocessor locking pulse, the AC voltage sensor senses ac filter capacitance voltage u of rectifier bridge _a, u _band u _c, after this voltage of microprocessor samples, it is carried out to the phase place of phase-locked acquisition ac filter capacitance voltage;

Second step: the direct voltage detecting unit of rectifier bridge DC side and direct current detection unit inspection DC voltage u _oand current i _dc, after microprocessor is sampled to this voltage and current, by itself and the given u of direct voltage _refas the input of microprocessor internal DC voltage controller, calculate the controlled quentity controlled variable u of DC side _dc, the computational methods of controlled quentity controlled variable are as follows:

u _err＝u _ref-u _o

$v_o=v_{\mathrm{otemp}}+\frac{{\mathrm{\&omega;}}_n^3{L}_{\mathrm{dc}}{C}_{\mathrm{dc}}}{311}{T}_s{u}_{\mathrm{err}}$

$u_{\mathrm{dc}}=v_o-\frac{{2.2\mathrm{\&omega;}}_n^2{L}_{\mathrm{dc}}{C}_{\mathrm{dc}}-1}{311}{u}_o-\frac{1.9{\mathrm{\&omega;}}_n{L}_{\mathrm{dc}}}{311}{i}_{\mathrm{dc}}$

V in formula _oand v _otempfor the intermediate variable in computational process, T _sfor sample frequency, L _dc, C _dcbe respectively DC inductance and DC voltage-stabilizing capacitance, ω _nfor the undamped oscillation frequency of improved DC side system, general value is more slightly larger than the resonance frequency of DC side LC;

3rd step: the coordinate transformation unit in AC current control device by coordinate transform by the ac filter capacitance voltage u under three-phase static coordinate system _a, u _band u _cbe transformed to the voltage u under two-phase rotating coordinate system _dand u _q, u _dand u _qaccount form be:

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}\sin \left(\mathrm{\&omega;t}\right)& \sin (\mathrm{\&omega;t}-\frac{2}{3}\mathrm{\&pi;})& \sin (\mathrm{\&omega;t}+\frac{2}{3}\mathrm{\&pi;})\\ \cos \left(\mathrm{\&omega;t}\right)& \cos (\mathrm{\&omega;t}-\frac{2}{3}\mathrm{\&pi;})& \cos (\mathrm{\&omega;t}+\frac{2}{3}\mathrm{\&pi;})\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]$

Then by u _d, u _qrespectively as the input of d axle and q axle virtual impedance adjuster, described d axle and q axle virtual resistance adjuster are all by high pass filter s/ (s+ ω _hP) and conductance link 1/R _hform, wherein ω _hPfor the corner frequency of high pass filter, R _hfor need to realize with the virtual resistance of ac filter Capacitance parallel connection, in microprocessor, the digital algorithm of d axle and q axle virtual resistance adjuster realizes being respectively:

$I_{\mathrm{dDamp}}\left(k\right)=\frac{{2u}_d\left(k\right)-{2u}_d(k-1)+(2-{\mathrm{\&omega;}}_{\mathrm{HP}}{T}_s)I_{\mathrm{dDamp}}(k-1)}{(2+{\mathrm{\&omega;}}_{\mathrm{HP}}{T}_s)R_H}$

$I_{\mathrm{qDamp}}\left(k\right)=\frac{{2u}_q\left(k\right)-{2u}_q(k-1)+(2-{\mathrm{\&omega;}}_{\mathrm{HP}}{T}_s)I_{\mathrm{qDamp}}(k-1)}{(2+{\mathrm{\&omega;}}_{\mathrm{HP}}{T}_s)R_H}$

Wherein u _d(k), u _qk () is respectively the input of d axle and the current bat of q axle virtual resistance adjuster;

I _dDamp(k), I _qDampk () is the output of the current bat of virtual resistance adjuster; u _d(k-1), u _q(k-1) be an input of clapping on virtual resistance adjuster, initial value is 0; I _dDamp(k-1), I _qDamp(k-1) be an output of clapping on virtual resistance adjuster, initial value is 0; T _sfor sampling interval duration, the output of virtual resistance adjuster just obtains controlled quentity controlled variable through divider divided by after DC bus current;

4th step: AC controlled quentity controlled variable is added with DC side controlled quentity controlled variable by adder, space vector PWM pulse is produced through space vector PWM pulse generate unit after obtaining master control amount, pulse blocking removed by microprocessor, the pwm pulse that microprocessor exports controls the break-make of each pipe of rectifier bridge after rectifier bridge power device driver element amplifies, along with the slowly rising of given voltage, rectifying device smooth starting;

Wherein: L _dcfor DC inductance, C _dcfor DC voltage-stabilizing electric capacity, R _hfor virtual resistance, u _ofor VD, i _dcfor DC inductance electric current.