CN102916597B - PWM (pulse width modulation) rectifier input and output power compensation control method in voltage asymmetry - Google Patents
PWM (pulse width modulation) rectifier input and output power compensation control method in voltage asymmetry Download PDFInfo
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Abstract
The invention discloses a PWM (pulse width modulation) rectifier input and output power compensation control method in voltage asymmetry. The technical scheme mainly includes that the PWM rectifier input and output power compensation control method in voltage asymmetry includes: negating an output active power actual value and an input reactive power actual value of a system prior to respectively enabling the negated values to pass through band-pass filters and PI (proportional integral) controllers, performing second harmonic compensation voltage computation to obtain an output active power second harmonic compensation item and an input reactive power second harmonic compensation item respectively, adding voltage reference values obtained by vector control with the second harmonic compensation items respectively, and performing reverse Park transformation by using a network voltage position angle as a transformation angle, so that reference voltages in a two-phase static coordinate system are obtained, and switching signals of a power device are generated after voltage signals are subjected to space vector pulse width modulation. By the PWM rectifier input and output power compensation control method in voltage asymmetry, input reactive power pulses and output active power pulses of a PWM rectifier can be compensated directly, and stable control of unity power factor running and direct-current bus voltage of the system is realized.
Description
Technical field
When the present invention relates to a kind of asymmetrical voltage, PWM rectifier input-output power compensating control method, belongs to electric and electronic power converting means control field, particularly PWM rectifier input-output power compensating control method during a kind of asymmetrical voltage.
Background technology
When line voltage unbalanced fault causes electrical network imbalance of three-phase voltage, the PWM rectifier based on the design of voltage condition of three-phase balance inputs reactive power by appearance two multiplied frequency harmonic, can not realize unity power factor and run; Active power of output, by appearance two multiplied frequency harmonic, causes DC bus-bar voltage to produce two double-frequency fluctuation.
For the control of Three-Phase PWM Rectifier under line voltage unbalanced fault, scholar is had to propose to set up the positive and negative sequence double-current ring control strategy that two current controllers implemented respectively in forward and backward synchronous rotating frame align, negative-sequence current carries out independent control.Have scholar to propose to be asked for by power bridge input side power the method for positive and negative sequence electric current, the method can obtain comparatively stable power output, suppresses DC bus-bar voltage fluctuation.In above method, controller all needs to implement at synchronous rotating frame, and needs to decompose positive and negative sequence component.In order to improve the response speed of Three-Phase PWM Rectifier, can align outside electric current loop, negative-sequence current reference value calculates, have scholar according to the positive and negative sequence given value of current value calculated, in two-phase rest frame, adoption rate-resonant controller aligns, negative-sequence current is unified regulates.Although the positive and negative sequence that the method avoids in current inner loop calculates, in order to calculate positive and negative sequence given value of current value, positive and negative sequence decomposition must be carried out to component each in system, adding the operand of control program.In addition, the method can not realize the unity power factor operation of system.
Therefore, PWM rectifier input-output power compensating control method when being necessary to design a kind of asymmetrical voltage, make system can realize unity power factor to run, simultaneously, do not need positive and negative sequence to decompose and can carry out direct compensation to the power output pulsation of PWM rectifier again, keep constant DC bus-bar voltage, the input and output quality of rectifier under effective raising line voltage unbalanced fault condition.
Summary of the invention
PWM rectifier input-output power compensating control method when the technical problem that the present invention solves there is provided a kind of asymmetrical voltage, the method does not need positive and negative sequence decomposition computation, and by carrying out direct compensation to the input-output power pulsation of PWM rectifier, realize system unit power factor to run and stable DC bus-bar voltage, ensure system input and output quality.
Technical scheme of the present invention is: PWM rectifier input-output power compensating control method during a kind of asymmetrical voltage, it is characterized in that comprising the following steps: (l), detection three-phase power grid voltage, three-phase input current and DC voltage, and by phase-locked loop detection of grid voltage angular velocity of rotation and position angle; (2), the three-phase power grid voltage detected and three-phase input current are obtained line voltage under two-phase static coordinate and input current through 3/2 conversion module; (3), by the line voltage under two-phase static coordinate and input current carry out Park conversion with line voltage position angle, obtain d, q axle line voltage and input current under synchronously rotating reference frame; (4), reactive power and active power of output is inputted according to the line voltage under a upper moment output voltage and two cordic phase rotators and input current computing system; (5) the system active power of output, step (4) obtained and input reactive power actual value negate also obtain the inverse value of system active power of output and input reactive power two harmonic actual value respectively through band pass filter 1, band pass filter 2, again through PI controller 1, PI controller 2 calculated by two frequency multiplication bucking voltages and obtain active power of output and input reactive power two frequency multiplication compensation term respectively, wherein the angular speed of band pass filter is set to two times of line voltage synchronous rotary angular speed; (6) difference of the DC voltage actual value, by DC voltage set-point and step (1) obtained, after PI controller 3, calculates the set-point of d shaft current under rotating coordinate system; (7) the d shaft current under the rotating coordinate system, the set-point of d shaft current under the rotating coordinate system calculated in step (6) and step (3) calculated is subtracted each other, then d axle output voltage values under PI controller 4 calculates rotating coordinate system, if q shaft current set-point is 0, the q shaft current that itself and step (3) calculate is subtracted each other, then q axle output voltage values under PI controller 5 calculates rotating coordinate system, by d, q axle output voltage values d, q shaft voltage reference value under decoupling compensation calculates rotating coordinate system; (8), d, q shaft voltage reference value under rotating coordinate system is calculated through bucking voltage, the two frequency multiplication compensation term obtained with step (5) respectively are again added, with line voltage position angle for angle of transformation carries out anti-Park conversion, obtain the voltage under two-phase rest frame, this voltage signal, after space vector pulse width modulation, produces the switching signal controlling power device.
As further execution mode, the angular speed of band pass filter described in step (5)
ω obe set to two times of line voltage synchronous rotary angular speed 2
ω g, its frequency-domain expression is:
Control method of the present invention is in line voltage unbalanced fault situation, do not need to carry out calculating Sum decomposition to the positive and negative sequence component in system, direct compensation can be carried out to the input reactive power of PWM rectifier and active power of output pulsation, realize the unity power factor operation of system and the stability contorting of DC bus-bar voltage, ensure that the input and output quality of system.Algorithm is simple, easily realizes.
Accompanying drawing explanation
Fig. 1 is Three-phase PWM Voltage Rectifier main circuit structure figure; Fig. 2 is the graph of a relation of system variable in different coordinates under line voltage unbalanced fault; The structure principle chart of Fig. 3 control system of the present invention; Fig. 4 is the input-output power oscillogram under vector control; Fig. 5 is the input-output power oscillogram under the present invention controls; Fig. 6 is the DC bus-bar voltage oscillogram under vector control; Fig. 7 is the DC bus-bar voltage oscillogram under the present invention controls.
specific implementation method
Below in conjunction with accompanying drawing, the present invention will be further described.Three-phase voltage type pwm converter main circuit structure as shown in Figure 1, in Fig. 1,
p i,
q iwith
p o,
q obe respectively electrical network input power and rectifier power output,
u a,
u b,
u cfor AC three-phase voltage source,
i a,
i b,
i cfor three-phase alternating current side input current,
v a,
v b,
v cfor power bridge input side three-phase voltage,
u dcfor DC voltage, O is electrical network mid point,
lwith
rbe respectively inlet wire inductance and equivalent resistance thereof,
cfor dc-link capacitance.In the ideal case, can think that electrical network input power equals the power sum that rectifier power output and inlet wire inductance and equivalent resistance consume, and rectifier power output equals DC side and bearing power sum.
Balance at electrical network three-phase voltage and under stable case, the Mathematical Modeling of PWM rectifier under synchronous rotating frame can be obtained:
(1)
In formula
u d,
u qbe respectively d, q axle component of line voltage,
i d,
i qbe respectively d, q axle component of ac-side current,
v d,
v qbe respectively d, q axle component of power bridge AC input voltage,
w gfor line voltage angular velocity of rotation.
Under synchronous rotating frame, system active power of output and input reactive power equation are
(2)
In formula:
p o,
q ibe respectively active power of output and input reactive power.
During unbalanced grid faults, each electricity of system comprises positive sequence component, negative sequence component and zero-sequence component.For three-phase without neutral system, not can think to there is zero-sequence component, therefore in the rotated coordinate system, only consider the positive sequence component in system charge and negative sequence component.If Fig. 2 is static α β coordinate system, forward and backward synchronous speed
ω grotate dq
p, dq
nvector correlation figure between coordinate system.In figure, subscript n, p represent forward and backward synchronous rotating frame respectively,
fbroad sense represents voltage, current phasor.
As shown in Figure 2, under unbalanced grid faults, between each variable of system, coordinate transformation relation is:
(3)
In formula, subscript n, p represent forward and backward synchronous rotating frame respectively, subscript n, and p represents positive and negative sequence component respectively.
The form of each electricity of system corresponding positive and negative sequence component in forward and backward rotating coordinate system when can draw unbalanced grid faults according to above formula:
(4)
Can system equation be obtained by Fig. 2 and Shi (1)-(4):
(5)
Under unbalance grid fault, two frequency multiplication equations of system active power of output and input reactive power are
(6)
Wherein
In formula
p oc2,
p os2be respectively the cosine of active power of output, sinusoidal two harmonic amplitudes,
q ic2,
q is2be respectively cosine, the sinusoidal two harmonic amplitudes of input reactive power.
Under unbalanced grid faults condition, system power can be expressed as the form of DC quantity and two harmonic sums.When electrical network generation unbalanced fault, each electricity is rotating forward in rotating coordinate system all containing two frequency multiplication of acs.Therefore during unbalance grid, the control key of PWM rectifier is the suppression to its two harmonic.
System active power of output can be obtained under negative sequence component under reverse sync rotating coordinate system in formula (6) is transformed into forward synchronous rotating frame, input reactive power two harmonic is
(7)
During stable state, ignore the impact of current differential item and equivalent resistance in formula (4), substituted into formula (7) and arrange as calculated and can obtain
(8)
From formula (8), positive sequence component is DC component, and negative sequence component is 2 harmonics.Make d axle and line voltage vector in the same way, now
=0.Because 2 harmonics of line voltage q axle fluctuate near 0, in order to reduce control system complexity, ignore this wave component, can obtain system power 2 frequency multiplication equation is
(9)
In electrical network generation unbalanced fault situation, DC component when considering stable situation can think constant, in order to embody the control to power two harmonic, can obtain formula (9) differentiate
(10)
Wherein
Can obtain according to formula (5) and formula (10)
(11)
In formula
,
be respectively PWM rectifier two frequency multiplication in synchronous rotating frame and control reference voltage, it can be designed to by resonance Controlling principle in proportion
(12)
Wherein
(13)
(14)
In formula
k p1,
k i1be respectively the ratio of PI controller, integral coefficient,
,
be respectively meritorious, reactive power two frequency multiplication command value.Control voltage in formula (12)
with
coefficient can by regulate proportionality coefficient
k prcompensate, formula (13) can be saved as electric voltage feed forward compensation term.Therefore, formula (12) can be reduced to
(15)
Formula (15) is final bucking voltage computational process.
According to formula (1), in synchronous rotating frame, convertor controls reference voltage can be designed to respectively:
(16)
Wherein
In formula
,
be respectively current transformer and control reference voltage,
k p,
k ibe respectively the ratio of controller, integral coefficient,
,
be respectively controller instruction current.In addition, decoupling compensation calculates and can carry out according to formula (16).
In electrical network generation unbalanced fault situation, adding the governing equation after power pulsations bucking voltage is
(17)
Fig. 3 is the structure principle chart of control system of the present invention, and its control method specifically comprises the steps:
L (), employing voltage sensor and current sensor detect three-phase power grid voltage respectively
u a,
u b,
u c, three phase network electric current
i a,
i b,
i c, adopt phase-locked loop detection of grid voltage angular velocity of rotation
ω gand position angle
θ;
(2) three-phase power grid voltage, step (l) detected
u a,
u b,
u cwith three phase network electric current
i a,
i b,
i cline voltage under 3/2 conversion module obtains two-phase rest frame
u α,
u βand input current
i α,
i β;
(3) line voltage under the two-phase rest frame, step (2) calculated
u α,
u βwith power network current
i α,
i βwith line voltage position angle
θcarry out Park conversion, obtain the line voltage under synchronously rotating reference frame
u d,
u qwith power network current
i d , i q;
(4), according to a upper moment output voltage reference value
v d_1 *,
v q_1 *and the line voltage under two cordic phase rotators that calculate of step (3)
u d,
u q, power network current
i d , i qcalculate system active power of output
p o, input reactive power
q i;
(5) the system active power of output, step (4) obtained and input reactive power actual value
p o,
q iobtain respectively through band pass filter (1), band pass filter (2) after negate the inverse value of two harmonic actual values of system active power of output and input reactive power-
p o2,-
q i2, then calculate through two frequency multiplication bucking voltages of PI controller 1, PI controller 2 through type (15) and obtain active power of output and input reactive power two frequency multiplication compensation term respectively
v dn *,
v qn *, wherein the angular speed of band pass filter is set to two times of line voltage synchronous rotary angular speed;
(6) difference of the DC voltage actual value, by DC voltage set-point and step (1) obtained, after PI controller 3, calculates the set-point of d shaft current under rotating coordinate system
i d *, and establish the set-point of q shaft current
i q *be 0;
(7), by the set-point of d, q shaft current under the rotating coordinate system that calculates in step (6)
i d *with
i q *d, q shaft current under the rotating coordinate system calculated with step (3) respectively
i dwith
i qsubtract each other, then calculate through PI controller 4, PI controller 5 and obtain d, q axle PI controller output valve under rotating coordinate system respectively
u d 'with
u q ';
(8), according to the PI controller output valve that step (7) calculates
u d 'with
u q ', through type (16) obtains voltage reference value
v d0 *with
v q0 *, by voltage reference value
v d0 *with
v q0 *respectively with two double frequency voltage compensation term
v dn *,
v qn *be added, with the line voltage position angle detected in step (1)
θfor angle of transformation carries out anti-Park conversion, obtain the voltage under two-phase rest frame, this voltage signal, after space vector pulse width modulation, produces the switching signal controlling power device.
The angular speed of PR controller in Fig. 3
ω obe set to two times of line voltage synchronous angular velocities 2
ω g, expression formula is:
(21)
Fig. 4, Fig. 5 are active power of output and the input reactive power oscillogram of PWM rectifier when adopting input power back off control and employing control method of the present invention, power waveform under being controlled as can be seen from Fig. 4 input power back off, when unbalance grid fault, input reactive power two double frequency power of system is inhibited, but two frequency multiplication pulsation have appearred in active power of output; And active power of output when adopting the present invention to control in Fig. 5 is effectively suppressed with two frequencys multiplication pulsation of input reactive power, ensure that output is meritorious, input the stable of reactive power.
Fig. 6, Fig. 7 are respectively DC voltage oscillogram when adopting input power back off control and control method of the present invention, as seen from Figure 6, when electrical network generation unbalanced fault, there are two double-frequency fluctuation in the PWM rectifier DC bus-bar voltage adopting input power back off to control, has a strong impact on the output quality of system; As seen from Figure 7, adopt the present invention to control effectively to suppress DC bus-bar voltage to fluctuate, obtain comparatively stable DC bus-bar voltage.
In sum, control method of the present invention effectively can suppress two double-frequency fluctuation of rectifier active power of output and input reactive power under unbalance grid fault condition, can obtain comparatively stable DC voltage, effectively improves the Control platform of converter; Amount of calculation is little compared with the double-current control method based on positive and negative sequence d, q coordinate, control structure is simple, system of can simultaneously eliminating exports secondary pulsation that is meritorious, input reactive power, and the unity power factor simultaneously realizing system runs and stable DC busbar voltage.
Claims (1)
1. PWM rectifier input-output power compensating control method during an asymmetrical voltage, it is characterized in that comprising the following steps: (l), detection three-phase power grid voltage, three-phase input current and DC voltage, and by phase-locked loop detection of grid voltage angular velocity of rotation and position angle; (2), the three-phase power grid voltage detected and three-phase input current are obtained line voltage under two-phase static coordinate and input current through 3/2 conversion module; (3), by the line voltage under two-phase static coordinate and input current carry out Park conversion with line voltage position angle, obtain d, q axle line voltage and input current under synchronously rotating reference frame; (4), reactive power and active power of output is inputted according to the line voltage under a upper moment output voltage and two cordic phase rotators and input current computing system; (5) obtain system active power of output respectively through band pass filter 1, band pass filter 2 and input the inverse value of reactive power two harmonic actual value after the system active power of output, step (4) obtained and the negate of input reactive power actual value, again through PI controller 1, PI controller 2 calculated by two frequency multiplication bucking voltages and obtain active power of output and input reactive power two frequency multiplication compensation term respectively, wherein the angular speed of band pass filter 1 and band pass filter 2 is set to two times of line voltage synchronous rotary angular speed; (6) difference of the DC voltage actual value, by DC voltage set-point and step (1) obtained, after PI controller 3, calculates the set-point of d shaft current under rotating coordinate system; (7) the d shaft current under the rotating coordinate system, the set-point of d shaft current under the rotating coordinate system calculated in step (6) and step (3) calculated is subtracted each other, then d axle output voltage values under PI controller 4 calculates rotating coordinate system, if q shaft current set-point is 0, the q shaft current that itself and step (3) calculate is subtracted each other, then q axle output voltage values under PI controller 5 calculates rotating coordinate system, by d, q axle output voltage values d, q shaft voltage reference value under decoupling compensation calculates rotating coordinate system; (8), d, q shaft voltage reference value under rotating coordinate system is calculated through bucking voltage, the two frequency multiplication compensation term obtained with step (5) respectively are again added, with line voltage position angle for angle of transformation carries out anti-Park conversion, obtain the voltage under two-phase rest frame, this voltage signal, after space vector pulse width modulation, produces the switching signal controlling power device.
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| CN105262121B (en) * | 2015-09-30 | 2018-01-05 | 南方电网科学研究院有限责任公司 | Negative-sequence current control method and system under flexible direct current power transmission system non-equilibrium state |
| CN107070193B (en) * | 2016-12-09 | 2019-06-25 | 南京理工大学 | A method of for optimizing Vienna rectifier input current |
| CN112787496B (en) * | 2019-11-07 | 2021-12-31 | 广东美芝制冷设备有限公司 | Variable frequency controller, control method thereof and variable frequency electric appliance |
| CN115313500B (en) * | 2022-10-12 | 2023-08-04 | 深圳库马克科技有限公司 | Control method of four-quadrant power unit |
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| EP1128535A2 (en) * | 2000-02-11 | 2001-08-29 | Oxford Magnet Technology Limited | Power converter controll loop |
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| EP1128535A2 (en) * | 2000-02-11 | 2001-08-29 | Oxford Magnet Technology Limited | Power converter controll loop |
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| 不平衡电网电压条件下PWM整流器功率谐振补偿控制策略;王萌等;《中国电机工程学报》;20120725;第32卷(第21期);第46-53页 * |
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