CN105743367A - Dead beat control method of pulse width modulation (PWM) rectifier under unbalanced power grid voltage - Google Patents

Dead beat control method of pulse width modulation (PWM) rectifier under unbalanced power grid voltage Download PDF

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Publication number
CN105743367A
CN105743367A CN201610232683.2A CN201610232683A CN105743367A CN 105743367 A CN105743367 A CN 105743367A CN 201610232683 A CN201610232683 A CN 201610232683A CN 105743367 A CN105743367 A CN 105743367A
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China
Prior art keywords
voltage
power
under
active power
reactive power
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CN201610232683.2A
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严广
蔡世冠
李传号
丁欣
刘毅
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China University of Mining and Technology CUMT
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China University of Mining and Technology CUMT
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

The invention discloses a dead beat control method of a pulse width modulation (PWM) rectifier under unbalanced power grid voltage. In the technical scheme, the dead beat control method comprises the following steps subtracting a DC bus voltage given value from an actual value thereof; obtaining an active power given value under the balanced power grid voltage through a proportion integral (PI) controller; carrying out compensation power calculation on the active power given value under the power voltage after 90-degree delay and the balanced power voltage to obtain a power compensation value under the unbalanced power grid voltage, wherein the power compensation value is added to the power given value under the balanced power grid voltage to serve as the power given value under the unbalanced power grid voltage; and calculating to obtain an input voltage reference value under a two-phase static coordinate by a dead beat controller, wherein a switch signal for controlling a power device is generated after space vector pulse width modulation is carried out on the voltage signal. Under the unbalanced power grid voltage, the power fluctuation of the PWM rectifier can be compensated in no need of positive and negative sequence separation, thus, three different control targets of achieving symmetrical sine current of a network side, eliminating active power fluctuation and eliminating reactive power fluctuation are achieved, the system performance is improved, and the system structure is simplified.

Description

PWM rectifier dead-beat control method under a kind of unbalanced electric grid voltage
Technical field
The present invention relates to the control method of voltage type PWM rectifier under a kind of unbalanced electric grid voltage, belong to electric and electronic power converting means control field, particularly PWM rectifier dead-beat control method under a kind of unbalanced electric grid voltage.
Background technology
Voltage type PWM rectifier has that power factor is controlled, Harmonics of Input is few, output DC voltage stability and energy can the advantage such as two-way flow, be widely used in fields such as alternating-current electric transmission, active power filtering, reactive power compensation, D.C. high voltage transmission and new energy grid-connected powers.
Track with zero error each switch periods realize next cycle start time set-point prediction, thus controlling system, there is the advantages such as algorithm is simple, control accurately, dynamic response is fast.Based on dead-beat direct Power Control method without phaselocked loop, it is not necessary to rotating coordinate transformation, and achieve constant frequency control.
At present the research of Three-phase PWM Voltage Rectifier control method is primarily directed under line voltage balance, reality can cause unbalanced source voltage when electrical network generation unbalanced fault or threephase load imbalance.Under unbalanced source voltage, line voltage and electric current will produce positive and negative sequence component, cause gaining merit, reactive power fluctuation and ac-side current distortion imbalance, have a strong impact on systematic function.
For the control of Three-Phase PWM Rectifier under unbalanced source voltage, having scholar to propose based on the dead-beat control method under rest frame, the method is without rotating coordinate transformation, but its power back-off calculates and remains a need for positive and negative sequence component extraction.
Therefore, it is necessary to design PWM rectifier dead-beat control method under a kind of unbalanced electric grid voltage, when control system is run, the separation of positive and negative sequence just the power swing of PWM rectifier can need not be compensated, thus realizing current on line side symmetrical sine, eliminating active power fluctuation, eliminating reactive power fluctuation three different control target, improve systematic function, simplify system structure.
Summary of the invention
Present invention solves the technical problem that and there is provided PWM rectifier dead-beat control method under a kind of unbalanced electric grid voltage, when control system is run, the separation of positive and negative sequence just the power swing of PWM rectifier can need not be compensated, thus realizing current on line side symmetrical sine, eliminating active power fluctuation, eliminating reactive power fluctuation three different control target, improve systematic function, simplify system structure.
The technical scheme is that PWM rectifier dead-beat control method under a kind of unbalanced electric grid voltage, it is characterised in that comprise the following steps: (1), detection three phase network phase voltage, Three-Phase PWM Rectifier input phase current and DC bus-bar voltage；(2) the three phase network phase voltage, step (1) detected and Three-Phase PWM Rectifier input phase current obtain the line voltage under biphase rest frame and input current through Clarke conversion module；(3), the line voltage under the biphase rest frame obtained according to step (2) and input current computing system instantaneous active power and reactive power；(4), the DC bus-bar voltage actual value that DC bus-bar voltage set-point and step (1) obtain being done difference, obtain the active power set-point under line voltage balance through PI controller, making the reactive power set-point under grid balance is 0；(5) the active power set-point under the line voltage balance that, the line voltage under biphase rest frame step (2) obtained obtains with step (2) after 90 ° postpone obtains the active power under unbalanced source voltage and reactive power compensation value through overcompensation power calculation；(6) active power, reactive power compensation value under the lower active power of the line voltage balance that step (4) obtained, reactive power set-point and unbalanced source voltage obtain the active power under unbalanced source voltage, reactive power set-point through giving power computation module；(7) active power under the unbalanced source voltage that electrical network instantaneous active power, reactive power and the step (6) step (3) obtained obtains, reactive power set-point calculate through track with zero error device and obtain the biphase input voltage reference value forbidden under coordinate system, this voltage signal, after space vector pulse width modulation, produces to control the switching signal of power device.
Accompanying drawing explanation
Fig. 1 is Three-phase PWM Voltage Rectifier main circuit structure figure；Fig. 2 is the structure principle chart that the present invention controls system；Fig. 3 is the oscillogram being provided without control method of the present invention；Fig. 4 is the oscillogram adopting the present invention to control target 1；Fig. 5 is the oscillogram adopting the present invention to control target 2；Fig. 6 is the oscillogram adopting the present invention to control target 3.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention will be further described.Three-phase PWM Voltage Rectifier main circuit topological structure is as it is shown in figure 1, ea、eb、ecFor three phase network phase voltage, ia、ib、icPhase current, v is inputted for Three-Phase PWM Rectifiera、vb、vcFor Three-Phase PWM Rectifier AC phase voltage, L, R are inductance and the equivalent resistance of three-phase alternating current reactance device, and C is DC filter capacitor, RLFor DC side load equivalent resistance.
Under unbalanced source voltage, for three-phase without neutral system, line voltage vector, power network current vector commutator AC voltage vector can be expressed as
(1)
(2)
In formula, subscript p, n represent positive and negative sequence component respectively；Subscript、Represent rest frame respectively、Axle component；Subscript d, q represent rotating coordinate system d, q axle component respectively,For line voltage angular frequency.
According to instantaneous power theory, grid side complex power S is represented by
(3)
(4)
Can obtain according to formula (1)-(4)
(5)
(6)
In formula, p0、q0The respectively DC component of active power, reactive power；pc2、qc2Respectively active power, reactive power 2 frequency multiplication cosine component amplitude；ps2、qs2Respectively active power, reactive power 2 frequency multiplication sinusoidal component amplitude.
For three-phase without neutral system, during unbalanced source voltage, three-phase power grid voltage can be expressed as
(7)
In formula,、、Respectively three-phase power grid voltage positive-sequence component；、、Respectively three-phase power grid voltage negative sequence component.
Can obtain according to Clarke conversion
(8)
Can obtain according to formula (1) and formula (2)
(9)
Can obtain according to formula (7)-(9)
(10)
(11)
According to symmetrical component method, the positive and negative sequence component of three-phase power grid voltage can be expressed as
(12)
(13)
In formula, a=ej2π/3。
Can be obtained by formula (8)
(14)
Can obtain according to formula (10)-(14)
(15)
(16)
Can be obtained by formula (1) and formula (2)
(17)
Can obtain according to formula (15)-(17)
(18)
(19)
By formula (18) and formula (19) it can be seen that the positive and negative sequence voltage component on dq coordinate axes can be usedComponent of voltage on coordinate axes and its component of voltage of 90 ° delayed represent.
In like manner can obtain
(20)
(21)
Formula (18), (20) are updated in formula (6), can obtain
(22)
If reference value respectively p meritorious during line voltage balance, reactive powerref-bal、qref-bal, then during unbalanced source voltage, meritorious, reactive power compensation value pcomp、qcompWith its reference value pref、qrefBetween relation can be expressed as
(23)
Due to algorithm self-defect, active power and reactive power fluctuation can not be eliminated while ensureing current on line side symmetrical sine, so the present invention proposes following 3 controls target:
Target 1: eliminate net side negative-sequence current, reduce current on line side harmonic content, it is thus achieved that symmetrical, sinusoidal power network current, make PWM rectifier operate under mean unit power factor state, namely
(24)
Can obtain according to formula (6), (18), (20), (24)
(25)
In formula,, and D1≠0。
According to formula (4), formula (23) and formula (25), arrangement can obtain meritorious, reactive power compensation value under unbalanced source voltage
(26)
Target 2: eliminate active power 2 double-frequency fluctuation, reduces current on line side harmonic content, it is thus achieved that sinusoidal power network current, makes PWM rectifier operate under mean unit power factor state, namely
(27)
Can obtain according to formula (22) and formula (27)
(28)
In formula, D2=2eαeβ⊥-2eβeα⊥, and D2≠0。
According to formula (4), formula (23) and formula (28), arrangement can obtain meritorious, reactive power compensation value under unbalanced source voltage
(29)
Target 3: eliminate reactive power 2 double-frequency oscillation, reduces current on line side harmonic content, it is thus achieved that sinusoidal power network current, makes PWM rectifier operate under mean unit power factor state, namely
(30)
Can obtain according to formula (22) and formula (30)
(31)
In formula,, and D3≠0。
According to formula (4), formula (23) and formula (31), arrangement can obtain meritorious, reactive power compensation value under unbalanced source voltage
(32)
According to formula (23), (26), (29), (31), it is possible to obtain the present invention three kinds under unbalanced source voltage and control the active power set-point p under targetrefWith reactive power set-point qref。
Track with zero error device can be expressed as
(33)
In formula, pref(k+1)、qref(k+1) respectively (k+1) TsMoment electrical network instantaneous active power, reactive power set-point；P (k), q (k) respectively kTsMoment electrical network instantaneous active power, reactive power；E (k), v (k) respectively kTsMoment line voltage and rectifier input voltage reference value, TSFor PWM rectifier switch periods.
By calculated (k+1) TsThe active power set-point p in momentref(k+1), reactive power set-point qrefAnd calculated kT (k+1)sInstantaneous active power p (k) in moment, instantaneous reactive power q (k) calculate the input voltage reference value obtaining under biphase rest frame through formula (33), this voltage signal, after space vector pulse width modulation, produces to control the switching signal of power device.
Fig. 2 is the structure principle chart that the present invention controls system, and its control method specifically includes following steps:
(1), voltage sensor and current sensor is adopted to detect three phase network phase voltage e respectivelya(k)、eb(k)、ec(k), Three-Phase PWM Rectifier input phase current ia(k)、ib(k)、ic(k) and DC bus-bar voltage vdc(k)；(2), the three phase network phase voltage e that step (1) is detecteda(k)、eb(k)、ec(k), Three-Phase PWM Rectifier input phase current ia(k)、ib(k)、icK () obtains the line voltage under biphase rest frame through Clarke conversion module、And input current、；(3), the line voltage under the biphase rest frame obtained according to step (2) and input current computing system instantaneous active power p (k) and reactive power q (k)；(4), by DC bus-bar voltage set-pointThe DC bus-bar voltage actual value v obtained with step (1)dcK () does difference, obtain the active power set-point p under line voltage balance through pi controllerref-balK (), makes the reactive power set-point q under grid balanceref-balK () is 0；(5), the line voltage under the biphase rest frame that step (2) is obtained、Active power set-point p under the line voltage balance obtained with step (2) after 90 ° postponeref-balK () obtains the active power offset p under unbalanced source voltage through overcompensation power calculationcomp(k) and reactive power compensation value qcomp(k)；(6) the active power set-point p under line voltage balance step (4) obtainedref-bal(k), reactive power set-point qref-balActive power offset p under (k) and unbalanced source voltagecomp(k), reactive power compensation value qcompK () obtains the active power set-point p under unbalanced source voltage through given power computation moduleref(k) and reactive power set-point qref(k)；(7) kT that step (3) is obtaineds(k+1) T that moment electrical network instantaneous active power p (k), reactive power q (k) and step (6) obtainsMoment network re-active power set-point pref(k+1), reactive power set-point qref(k+1) kT is obtained through the calculating of track with zero error devicesInput voltage reference value under moment biphase rest frame、, this voltage signal, after space vector pulse width modulation, produces to control the switching signal of power device.
Fig. 3 is the oscillogram being provided without control method of the present invention, when unbalanced source voltage, although can obtain active power and reactive power comparatively smoothly, but electric current there occurs distortion imbalance.
Fig. 4 is the oscillogram adopting the present invention to control target 1, although meritorious comparatively obvious with idle 2 double-frequency fluctuation, but is a cancellation net side negative-sequence current, it is thus achieved that symmetrical, sinusoidal power network current.
Fig. 5 is the oscillogram adopting the present invention to control target 2, although current on line side symmetry is not as, but eliminates active power 2 double-frequency fluctuation, it is thus achieved that sinusoidal power network current.
Fig. 6 is the oscillogram adopting the present invention to control target 3, although current on line side symmetry is not as, but eliminates reactive power 2 double-frequency fluctuation, it is thus achieved that sinusoidal power network current.
In sum, during unbalanced source voltage, the power swing of PWM rectifier need not just can compensated by the control method of the present invention in the separation of positive and negative sequence, thus realizing current on line side symmetrical sine, eliminating active power fluctuation, eliminating reactive power fluctuation three different control target, improve systematic function, simplify system structure.

Claims (1)

1. PWM rectifier dead-beat control method under a unbalanced electric grid voltage, it is characterised in that comprise the following steps: (1), detection three phase network phase voltage, Three-Phase PWM Rectifier input phase current and DC bus-bar voltage；(2) the three phase network phase voltage, step (1) detected and Three-Phase PWM Rectifier input phase current obtain the line voltage under biphase rest frame and input current through Clarke conversion module；(3), the line voltage under the biphase rest frame obtained according to step (2) and input current calculate electrical network instantaneous active power and reactive power；(4), the DC bus-bar voltage actual value that DC bus-bar voltage set-point and step (1) obtain is done difference, obtaining the active power set-point under line voltage balance through pi controller, making the reactive power set-point under grid balance is 0；(5) the active power set-point under the line voltage balance that, the line voltage under biphase rest frame step (2) obtained obtains with step (2) after 90 ° postpone obtains the active power under unbalanced source voltage and reactive power compensation value through overcompensation power calculation；(6) active power, reactive power compensation value under the lower active power of the line voltage balance that step (4) obtained, reactive power set-point and unbalanced source voltage obtain the active power under unbalanced source voltage, reactive power set-point through giving power computation module；(7) active power, reactive power set-point under the unbalanced source voltage that electrical network instantaneous active power, reactive power and the step (6) step (3) obtained obtains calculate the input voltage reference value obtaining under biphase rest frame through track with zero error device, this voltage signal, after space vector pulse width modulation, produces to control the switching signal of power device.
CN201610232683.2A 2016-04-15 2016-04-15 Dead beat control method of pulse width modulation (PWM) rectifier under unbalanced power grid voltage Pending CN105743367A (en)

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WO2023050384A1 (en) * 2021-09-30 2023-04-06 宁德时代新能源科技股份有限公司 Power grid voltage unbalance suppression method and device
CN115967127A (en) * 2022-12-14 2023-04-14 南通国轩新能源科技有限公司 Direct power control system and method based on grid-connected inverter power prediction model

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CN115967127A (en) * 2022-12-14 2023-04-14 南通国轩新能源科技有限公司 Direct power control system and method based on grid-connected inverter power prediction model
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Application publication date: 20160706