CN103078526A - Current source type rectifier and grid-connected control method based on virtual resistor - Google Patents

Abstract

The invention discloses a current source type PWM (Pulse-Width Modulation) rectifier and a grid-connected control method based on a virtual resistor. A grid-connected rectifier consists of commercial power, an alternating-current filtering inductor, an alternating-current filtering capacitor, a three-phase current source type rectifier, a direct-current inductor, a direct-current capacitor and a digital controller. Sampled alternating-current filtering capacitance voltage is transmitted to a microprocessor to perform digital phase locking, and after phase locking is finished, the alternating-current filtering capacitance voltage and phase are transmitted to an alternating-current controller. The alternating-current controller consists of a coordinate converter, a virtual impedance regulator and a divider. The coordinate converter converts the three-phase alternating-current filtering capacitance voltage into the voltage under a two-phase static coordinate system, after the voltage is regulated by the virtual resistance regulator, current passing through a virtual resistor is obtained, control amount of the alternating-current side is obtained through the divider, the control amount is superposed on the control amount on the direct-current side, a driving signal obtained through a PWM generator is transmitted to a driving plate, and after the signal is amplified by the driving plate, the connection and disconnection of a three-phase current source type rectifying bridge switch are controlled. The control effect of the virtual resistance regulator in the alternating-current controller is equivalent to the control effect that a resistor is directly connected in parallel on an alternating-current capacitor, so that oscillation can be effectively damped, loss is not caused, and ultraharmonics in grid-connected current can be effectively inhibited. The rectifier is high in dynamic response speed, stable in dynamic response and high in power factor, the total harmonic distortion rate of the grid-connected current is low, and the method can be applied to an uninterruptible power supply.

Description

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

Technical field

The present invention relates to the control method of a kind of current source type rectifier steady control and the low total percent harmonic distortion of grid-connected current of realization, belong to the field of Rectifier.

Background technology

Traditional ups power adopts phase controlled rectifier usually, and DC bus-bar voltage is about 400V.But because its power factor is low, large to electric network pollution, replaced by the high-frequency PWM rectifier based on full control device gradually.The high-frequency PWM rectifier is divided into two kinds of voltage-source type and current source types, wherein the needed DC bus-bar voltage of current source type PWM rectifier is lower than the peak-to-peak value of AC voltage, therefore when DC bus-bar voltage is the 400V left and right sides, can be under the prerequisite that keeps existing DC bus-bar voltage and rear class inverter with current source type PWM current transformer, finish the upgrading work of UPS with lower cost, and also be good selection for the high power UPS of a new generation.

Because current source type rectifier AC uses inductance capacitor filtering, easily produce resonance at AC, affect the waveform of grid-connected current and may cause shutdown.With respect to the voltage-source type rectifier, the transient model exponent number of current source type rectifier is high, coupling is strong, and has nonlinear characteristics, and the Direct Current Control and the indirect current control that are usually used in the voltage-source type rectifier are difficult to directly use on the current mode rectifier.Nonlinear control method has solved the problem of the non-linear close coupling of current source type rectifier in theory well, can carry out damping to AC by closed-loop control, but control performance is strong to the dependence of system parameters, to the parameter sensitive, and realizes complicated.

In theory, the mode of parallel resistance is to suppress the most simple and efficient mode of vibration on ac filter electric capacity, but can't practical application because resistance can produce power consumption.

Summary of the invention

The present invention be directed to the deficiencies in the prior art, on the basis of current source type rectifier DC side closed-loop control, a kind of active damping control technology that realizes virtual resistance at AC by the FEEDBACK CONTROL of of ac that proposes, can effectively suppress the resonance that the Inductor capacitive filter occurs, and reduced total percent harmonic distortion of grid-connected current, and do not affect stability and the dynamic response characteristic of DC side.

Current source type rectifier based on virtual resistance of the present invention is comprised of rectifier bridge, microprocessor and rectifier bridge power device driver element, and described rectifier bridge is connected communication by rectifier bridge power device driver element with microprocessor; The AC of described rectifier bridge disposes ac filter inductance, ac filter electric capacity and AC voltage sensor successively; DC side at rectifier bridge disposes dc inductance, DC voltage-stabilizing electric capacity, direct voltage detecting unit and direct current detection unit.

Phase-locked loop, dc voltage controller, AC current control device, adder and space vector PWM pulse generate unit be equipped with successively in the described microprocessor.

Coordinate transformation unit, d axle virtual resistance adjuster, q axle virtual resistance adjuster and divider are arranged in the described AC current control device.

Further, described virtual resistance adjuster comprises high pass filter and virtual electric lead ring joint.

Utilize described current source type rectifying device based on virtual resistance to realize that the control method that suppresses resonance and reduce the total percent harmonic distortion of grid-connected current is:

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

Second step: after the direct voltage detecting unit of rectifier bridge DC side and direct current detection unit inspection dc voltage and electric current, microprocessor are sampled to this voltage and current, with itself and the given u of direct voltage _RefAs the input of microprocessor internal dc voltage controller, calculate the controlled quentity controlled variable of DC side.The computational methods of controlled quentity controlled variable are as follows:

u _err＝u _ref-u _o (1)

$v_o=v_{\mathrm{otemp}}+\frac{{\mathrm{\ω}}_n^3{L}_{\mathrm{dc}}{C}_{\mathrm{dc}}}{311}{T}_s{u}_{\mathrm{err}}---\left(2\right)$

$u_{\mathrm{dc}}=v_o-\frac{2.2{\mathrm{\ω}}_n^2{L}_{\mathrm{dc}}{C}_{\mathrm{dc}}-1}{311}{u}_o-\frac{1.9{\mathrm{\ω}}_n{L}_{\mathrm{dc}}}{311}{i}_{\mathrm{dc}}---\left(3\right)$

V in the formula _oAnd v _OtempBe the intermediate variable in the computational process, T _sBe sample frequency, L _Dc, C _DcBe respectively dc inductance and DC voltage-stabilizing capacitance, ω _nBe the undamped oscillation frequency of improved DC side system, general value is more slightly larger than the resonance frequency of DC side inductance capacitance.

The 3rd step: the coordinate transformation unit in the AC current control device by coordinate transform with the ac filter capacitance voltage u under the three phase static coordinate system _a, u _bAnd u _cBe transformed to the voltage u under the two-phase rotating coordinate system _dAnd u _q, u _dAnd u _qAccount form be:

$\left[\begin{array}{c}{u}_d\\ u_q\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}\sin \left(\mathrm{\ωt}\right)& \sin (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})& \sin (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})\\ \cos \left(\mathrm{\ωt}\right)& \cos (\mathrm{\ωt}-\frac{2}{3}\mathrm{\π})& \cos (\mathrm{\ωt}+\frac{2}{3}\mathrm{\π})\end{array}\right]\left[\begin{array}{c}{u}_a\\ u_b\\ u_c\end{array}\right]---\left(4\right)$

Then with u _d, u _qAs 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 respectively _HP) and electric lead ring joint 1/R _HConsist of, wherein ω _HPBe the corner frequency of high pass filter, R _HFor needs that realize with the virtual resistance ac filter Capacitance parallel connection, the digital algorithm of d axle and q axle virtual resistance adjuster is realized being respectively in the microprocessor:

$I_{\mathrm{dDamp}}\left(k\right)=\frac{{2u}_d\left(k\right)-{2u}_d(k-1)+(2-{\mathrm{\ω}}_{\mathrm{HP}}{T}_s)I_{\mathrm{dDamp}}(k-1)}{(2+{\mathrm{\ω}}_{\mathrm{HP}}{T}_s)R_H}---\left(5\right)$

$I_{\mathrm{qDamp}}\left(k\right)=\frac{{2u}_q\left(k\right)-{2u}_q(k-1)+(2-{\mathrm{\ω}}_{\mathrm{HP}}{T}_s)I_{\mathrm{qDamp}}(k-1)}{(2+{\mathrm{\ω}}_{\mathrm{HP}}{T}_s)R_H}---\left(6\right)$

U wherein _d(k), u _q(k) be respectively the input of d axle and the current bat of q axle virtual resistance adjuster; _DDamp(k), I _QDamp(k) be the output of the current bat of virtual resistance adjuster; u _d(k-1), u _q(k-1) be an input of clapping on the virtual resistance adjuster, initial value is 0; I _DDamp(k-1), I _QDamp(k-1) be an output of clapping on the virtual resistance adjuster, initial value is 0; T _sBe the time in sampling interval, the output of virtual resistance adjuster just controlled amount after divider is divided by dc bus current.

The 4th the step: with adder with AC controlled quentity controlled variable and the addition of DC side controlled quentity controlled variable, obtain the master control amount and produce the space vector PWM pulse by space vector PWM pulse generate unit, microprocessor is removed pulse blocking, the break-make of the pwm pulse of microprocessor output each pipe of control rectifier bridge after rectifier bridge power device driver element amplifies, along with the slowly rising of given voltage, rectifying device smooth starting.

Beneficial effect of the present invention is: the present invention is not increasing hardware cost, is not wasting under the prerequisite of energy, the control method that the current source type rectifier suppresses resonance and reduces the total percent harmonic distortion of grid-connected current is proposed, by above-mentioned digital control algorithm, be equivalent to resistance in parallel on AC electric capacity, thereby the resonance that can effectively suppress Inductor electric capacity, and total percent harmonic distortion of reduction grid-connected current, and do not affect stability and the dynamic response characteristic of DC side, control is convenient, successful.

Description of drawings

Fig. 1 is the current source type rectifying device simplified electrical circuit diagram based on virtual resistance;

Fig. 2 is current source type rectifying device main circuit part;

Fig. 3 is for using virtual resistance to carry out the control block diagram of active damping;

Fig. 4 is for using the whole device schematic diagram of current source type of passive damping;

Fig. 5 is for using the whole device schematic diagram of current source type of virtual resistance;

Among the figure: 1, rectifier bridge; 2, ac filter electric capacity; 3, AC voltage sensor; 4, ac filter inductance; 5, utility grid; 6, dc inductance; 7, direct current detection unit; 8, DC voltage-stabilizing electric capacity; 9, direct voltage detecting unit; 10, load; 11, microprocessor; 12, rectifier bridge power device driver element; 13, dc voltage controller; 14, phase-locked loop; 15, AC current control device; 16, adder; 17, space vector PWM pulse generate unit; 18, coordinate converter; 19, d axle virtual resistance adjuster; 20, q axle virtual resistance adjuster; 21, divider.

Embodiment

Such as Fig. 1, current source type rectifier based on virtual resistance of the present invention is: be comprised of rectifier bridge 1, microprocessor 11 and rectifier bridge power device driver element 12, described rectifier bridge 1 is connected communication by rectifier bridge power device driver element 12 with microprocessor 11; AC at rectifier bridge 1 disposes ac filter electric capacity 2, AC voltage sensor 3 and ac filter inductance 4 successively, and ac filter inductance 4 links to each other with utility grid 5; DC side at rectifier bridge 1 disposes dc inductance 6, direct current detection unit 7, DC voltage-stabilizing electric capacity 8 and direct voltage detecting unit 9, connects load 10 behind the DC voltage-stabilizing electric capacity 8.This current source type rectifying device main circuit part as shown in Figure 2.

Dc voltage controller 13, phase-locked loop 14, AC current control device 15, adder 16 and space vector PWM pulse generate unit 17 are arranged in the described microprocessor 11.

Coordinate converter 18, d axle virtual resistance adjuster 19, q axle virtual resistance adjuster 20 and divider 21 are arranged in the described alternating-current controller 15.

Utilize the current source type rectifier based on virtual resistance of the present invention to realize that the method for network control system is: after rectifier powered on and starts shooting, AC voltage sensor 3, direct current detection unit 7 and direct voltage detecting unit 9 began to detect respectively ac filter capacitance voltage u _a, u _b, u _cAnd dc bus current and DC bus-bar voltage.The signal that 11 pairs of detecting units of microprocessor detect is sampled, and obtains the digital quantity of each signal in microprocessor.Use 14 pairs of ac filter capacitance voltages of phase-locked loop u _a, u _bAnd u _cCarry out phase-lockedly, obtain the phase theta of ac filter capacitance voltage.With the given u of dc bus current, DC bus-bar voltage and direct voltage _RefAs the input of dc voltage controller 13, calculate the controlled quentity controlled variable of DC side.The computational methods of DC side controlled quentity controlled variable are shown in (1), (2) and (3) formula.With ac filter capacitance voltage u _a, u _b, u _cWith the input of phase theta as alternating-current controller 15, calculate the controlled quentity controlled variable of AC.DC side controlled quentity controlled variable and AC controlled quentity controlled variable obtain the master control amount after adder 16 additions, with the input of master control amount as space vector PWM pulse generate unit 17, obtain pwm pulse after the modulation.After removing pulse blocking, microprocessor 11 begins to export pwm pulse, the break-make of pwm pulse control rectifier bridge 1 each pipe after rectifier bridge power device driver element 12 amplifies, and rectifier is started working.Along with the slowly rising of given voltage, flow directing device smooth starting.

Wherein the detailed process that realizes of alternating-current controller is: by coordinate converter 18 with the ac filter capacitance voltage u under the three phase static coordinate system _a, u _bAnd u _cBe transformed to the voltage u under the two-phase rotating coordinate system _dAnd u _q

With u _d, u _qRespectively as the input of d axle virtual resistance adjuster 19 and q axle virtual resistance adjuster 20.Use control principle block diagram that virtual resistance carries out active damping as shown in Figure 3, the virtual resistance adjuster among the figure in the dotted line frame is by high pass filter s/ (s+ ω _HP) and electric lead ring joint 1/R _HConsist of, wherein ω _HPBe the corner frequency of high pass filter, R _HRealize for needs with the ac filter Capacitance parallel connection virtual resistance.The virtual resistance adjuster realizes that at the digital algorithm in the microprocessor shown in formula (5) and (6), its effect is equivalent on ac filter electric capacity limit and a resistance, as shown in Figure 4.

U in the formula _d(k), u _q(k) be the input of the current bat of virtual resistance adjuster; I _DDamp(k), I _QDamp(k) be the output of the current bat of virtual resistance adjuster; u _d(k-1), u _q(k-1) be an input of clapping on the virtual resistance adjuster, initial value is 0; I _DDamp(k-1), I _QDamp(k-1) be an output of clapping on the virtual resistance adjuster, initial value is 0; T _sBe the time in sampling interval.The output of virtual resistance adjuster just obtains the controlled quentity controlled variable of AC after divider 21 is divided by dc bus current.Ac modulation amount control rectifier bridge switching tube break-make, brachium pontis flows through additional electric current I _KDamp(k), as shown in Figure 5, realized the introducing of virtual resistance.

Scheme of the present invention is on the basis of rectifying device DC side closed-loop control, AC is carried out controlling based on the open loop of active damping, realize the inhibition of wave filter on AC side resonance and the reduction of the total percent harmonic distortion of grid-connected current, and do not affected steady-state characteristic and the dynamic response of DC side.

Claims (5)

1. based on the current source type rectifier of virtual resistance, it is characterized in that: described rectifier is comprised of rectifier bridge, microprocessor and rectifier bridge power device driver element, and described rectifier bridge is connected communication by rectifier bridge power device driver element with microprocessor; The AC of described rectifier bridge disposes ac filter inductance, ac filter electric capacity and AC voltage sensor successively; DC side at rectifier bridge disposes dc inductance, DC voltage-stabilizing electric capacity, direct voltage detecting unit and direct current detection unit.

2. the current source type rectifier based on virtual resistance as claimed in claim 1 is characterized in that: be equipped with successively phase-locked loop, dc voltage controller, AC current control device, adder and space vector PWM pulse generate unit in the described microprocessor.

3. the current source type rectifier based on virtual resistance as claimed in claim 1 is characterized in that: coordinate transformation unit, d axle virtual resistance adjuster, q axle virtual resistance adjuster and divider are arranged in the described AC current control device.

4. the current source type rectifier based on virtual resistance as claimed in claim 3 is characterized in that: described virtual resistance adjuster comprises high pass filter and virtual electric lead ring joint.

5. utilize the current source type rectifying device based on virtual resistance as claimed in claim 1 to realize that the control method that suppresses resonance and reduce the total percent harmonic distortion of grid-connected current is:

The first step: after rectifier powers on and starts shooting, microprocessor locking pulse, the AC voltage sensor senses ac filter capacitance voltage u of rectifier bridge _a, u _bAnd u _c, behind this voltage of microprocessor samples it is carried out 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, with 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

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

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

V in the formula _oAnd v _OtempBe the intermediate variable in the computational process, T _sBe sample frequency, L _Dc, C _DcBe respectively dc inductance and DC voltage-stabilizing capacitance, ω _nBe the undamped oscillation frequency of improved DC side system, general value is more slightly larger than the resonance frequency of DC side LC.

The 3rd step: the coordinate transformation unit in the AC current control device by coordinate transform with the ac filter capacitance voltage u under the three phase static coordinate system _a, u _bAnd u _cBe transformed to the voltage u under the two-phase rotating coordinate system _dAnd u _q, u _dAnd u _qAccount form be:

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

Then with u _d, u _qAs 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 respectively _HP) and electric lead ring joint 1/R _HConsist of, wherein ω _HPBe the corner frequency of high pass filter, R _HFor needs that realize with the virtual resistance ac filter Capacitance parallel connection, the digital algorithm of d axle and q axle virtual resistance adjuster is realized being respectively in the microprocessor:

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

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

U wherein _d(k), u _q(k) be respectively the input of d axle and the current bat of q axle virtual resistance adjuster; I _DDamp(k), I _QDamp(k) be the output of the current bat of virtual resistance adjuster; u _d(k-1), u _q(k-1) be an input of clapping on the virtual resistance adjuster, initial value is 0; I _DDamp(k-1), I _QDamp(k-1) be an output of clapping on the virtual resistance adjuster, initial value is 0; T _sBe the time in sampling interval, the output of virtual resistance adjuster just controlled amount after divider is divided by dc bus current;

The 4th the step: with adder with AC controlled quentity controlled variable and the addition of DC side controlled quentity controlled variable, obtain the master control amount and produce the space vector PWM pulse by space vector PWM pulse generate unit, microprocessor is removed pulse blocking, the break-make of the pwm pulse of microprocessor output each pipe of control rectifier bridge after rectifier bridge power device driver element amplifies, along with the slowly rising of given voltage, rectifying device smooth starting.

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