CN110649664B - Enhanced control method for three-vector prediction optimization based on extended active power theory - Google Patents

Enhanced control method for three-vector prediction optimization based on extended active power theory Download PDF

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CN110649664B
CN110649664B CN201910896350.3A CN201910896350A CN110649664B CN 110649664 B CN110649664 B CN 110649664B CN 201910896350 A CN201910896350 A CN 201910896350A CN 110649664 B CN110649664 B CN 110649664B
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CN110649664A (en
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冉晓洪
徐波
冷仕鹏
刘开培
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Wuhan University WHU
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
    • 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
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only

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Abstract

The invention provides an enhancement control method of three-vector prediction optimization based on an extended active power theory. The method comprises the steps of collecting network side three-phase voltage, network side three-phase current and direct current side capacitor voltage to obtain voltage and current under a two-phase static coordinate system; establishing a novel mathematical model of active power and reactive power of the grid-side two-phase static coordinate system based on an extended instantaneous active power theory according to the voltage and the current of the grid-side two-phase static coordinate system, and respectively deriving and discretizing; analyzing the composition of the average power and the frequency doubling component of the AC/DC converter under the unbalanced power grid condition; establishing a novel active and reactive power deviation square sum minimum cost function model; determining a first acting non-zero voltage vector, a second acting non-zero voltage vector and a zero voltage vector; further, the optimal acting time of the first acting non-zero voltage vector, the second acting non-zero voltage vector and the zero voltage vector is calculated. The method has the advantages of no need of extra power compensation calculation, small power pulsation and small harmonic content of the current on the network side.

Description

Enhanced control method for three-vector prediction optimization based on extended active power theory
Technical Field
The invention belongs to the technical field of operation and control of a converter of a flexible direct current transmission system, and particularly relates to an enhanced control method of three-vector prediction optimization based on an extended active power theory.
Technical Field
The AC micro-grid and the DC micro-grid become main components of a power distribution network in China gradually and respectively consist of a distributed power supply, an energy conversion device, an energy storage device and an AC/DC load, wherein an AC/DC converter connecting the AC micro-grid and the DC micro-grid becomes an important support of the whole micro-grid, and the stable operation capability of the AC/DC converter under the complex power grid operation condition has important influence on the safe and reliable operation of the micro-grid. Therefore, the research on the stable control of the AC/DC converter under the complex grid operation condition, particularly under the unbalanced grid condition, has important practical significance.
At present, as the rapid development of model predictive control technology has become one of the important control methods of power electronic converters, the method has wide application in AC/DC converters, mainly including: the method comprises the following steps of single-vector/multi-vector model predictive control of a converter under a normal operation condition and single-vector/multi-vector model predictive control with power compensation under an unbalanced power grid condition, but the control method needs to calculate extra power compensation in each control period and is large in calculation amount. Therefore, scholars propose single-vector and multi-vector model predictive control methods under unbalanced power grid conditions based on the extended instantaneous power theory, the control methods do not need sequence component decomposition and extra power compensation calculation, the single-vector model predictive control method is developed to the multi-vector model predictive control technology, and the control precision is higher and higher. In order to further enrich the diversity and control precision of model prediction technology, the invention defines a calculation method for expanding instantaneous active power, introduces the method into the design of a controller of an AC/DC converter under the condition of an unbalanced power grid, and provides an enhanced control method based on three-vector prediction optimization of an expanded active theory. The control method does not need sequence component decomposition, a phase-locked loop, extra power compensation calculation and the like, and has the characteristics of high control precision and good control performance.
Disclosure of Invention
The technical scheme of the system is a three-vector prediction optimization enhancement control method based on an extended active power theory, and is characterized by comprising the following steps: the system comprises a three-phase alternating current power grid, a three-phase filter inductor, a three-phase voltage sensor, a three-phase current sensor, a direct current voltage sensor, a main controller, a three-phase AC/DC converter, a direct current side capacitor and a direct current side load;
the three-phase alternating current power grid is connected with the three-phase voltage sensor through a wire; the three-phase power grid is connected with the three-phase current sensor through a wire; the direct current side capacitor is connected with the direct current voltage sensor through a lead; the main controller is respectively connected with the three-phase voltage sensor, the three-phase current sensor and the direct current voltage sensor in sequence through leads; the main controller is connected with the three-phase AC/DC converter through a lead; the three-phase alternating current power grid, the three-phase filter inductor, the three-phase AC/DC converter, the direct current side capacitor and the direct current side load are sequentially connected in series through a lead.
The invention provides an enhancement control method of three-vector prediction optimization based on an extended active power theory, which mainly comprises the following steps:
step 1: collecting network side three-phase voltage, network side three-phase current and direct current side capacitor voltage, and respectively converting abc coordinate systems of the network side three-phase voltage and the network side three-phase current into an alpha beta coordinate system by using Clarke transformation so as to obtain voltage and current under a two-phase static coordinate system;
step 2: establishing a novel mathematical model of active power and reactive power of the grid-side two-phase static coordinate system based on an extended instantaneous active power theory according to the voltage and the current of the grid-side two-phase static coordinate system, and respectively deriving and discretizing;
and step 3: analyzing the composition of the average power and the second harmonic component of the AC/DC converter under the unbalanced power grid condition based on a novel mathematical model of active power and reactive power;
and 4, step 4: based on the power analysis of a converter under the condition of an unbalanced power grid, a novel active power deviation and reactive power deviation square sum minimum cost function model is established by taking the elimination of double-frequency fluctuation of active power and the guarantee of the sine of current on the grid side as control targets;
and 5: determining a first action nonzero voltage vector, a second action nonzero voltage vector and a zero voltage vector by utilizing a defined novel active power deviation and reactive power deviation square sum minimum cost function model;
step 6: respectively solving the partial derivatives of the defined novel active power deviation, reactive power deviation square and minimum cost function model to obtain a first action nonzero voltage vector, a second action nonzero voltage vector and the optimal action time of the zero voltage vector;
and 7: a switching signal is sent out by utilizing a space vector modulation method to inhibit a second harmonic component of novel active power of the AC/DC converter under the condition of unbalanced grid voltage and reduce the harmonic content of current on the grid side;
preferably, in step 1, the grid-side three-phase voltage is:
acquiring the three-phase voltage of the grid side through the three-phase voltage sensor;
the A-phase grid voltage is eaThe B-phase grid voltage is ebThe C-phase grid voltage is ec；
Collecting the three-phase current of the grid side through the three-phase current sensor;
in the step 1, the three-phase current at the network side is as follows:
the A-phase grid current is iaThe B-phase grid current is ibThe C-phase grid current is ic；
In the step 1, the voltage of the direct current side capacitor is as follows:
collecting the direct current side capacitance voltage through the direct current voltage sensor;
the voltage of the DC side capacitor is udc；
Transmitting the network side three-phase voltage, the network side three-phase current and the direct current side capacitor voltage to the main controller;
respectively converting an abc coordinate system of the three-phase voltage on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure BDA0002210395650000031
Figure BDA0002210395650000032
wherein e isαCorresponding three-phase voltage on grid side to grid voltage value on alpha axis, eβCorresponding the three-phase voltage on the network side to the voltage value of the power grid on the beta axis;
respectively converting an abc coordinate system of the three-phase current on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure BDA0002210395650000033
Figure BDA0002210395650000034
wherein iαThe grid side three-phase current corresponds to the grid current value i on the alpha axisβThe three-phase current at the network side corresponds to the current value of the power grid on a beta axis;
the grid-side three-phase voltage vector e can be expressed as:
e＝eα+jeβ
the grid-side three-phase current vector i can be expressed as:
i＝iα+jiβ
in addition, the amplitude and the phase angle of the three-phase voltage vector on the grid side are respectively as follows:
Figure BDA0002210395650000035
Figure BDA0002210395650000036
wherein E is the amplitude of the three-phase voltage vector on the network side, theta1Is the phase angle of the three-phase voltage vector at the network side;
preferably, in step 2, a novel mathematical model of active power and reactive power is established based on the extended instantaneous active power theory, and the expression is as follows:
Figure BDA0002210395650000041
wherein i*Is the conjugate of the grid-side three-phase current vector i, and e' represents the voltage vector obtained after the grid-side three-phase voltage vector e is delayed by 1/4 grid periods, PnewThe method comprises the steps of representing novel active power based on an extended instantaneous active power theory, Q representing reactive power based on the extended instantaneous active power theory, and Im representing the imaginary part of a vector; e.g. of the typeαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβFor the three-phase network voltage to correspond to the network voltage value on the beta axis, iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβIs corresponding to the current of the three-phase power gridThe grid current value on the beta axis; e'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay;
in step 2, the new active power and reactive power derivation is respectively:
Figure BDA0002210395650000042
wherein e is a three-phase voltage vector on the network side, e*Is the conjugate of a grid-side three-phase voltage vector e, e' represents a voltage vector obtained after the grid-side three-phase voltage vector e is delayed by 1/4 power grid periods, v is a converter output voltage vector, v*For the conjugate of the converter output voltage vector v, R is the parasitic resistance value of the grid-side filter, L is the inductance value of the grid-side filter, and ω is the grid angular frequency;
discretizing the derivative of the novel active power and the reactive power into:
Figure BDA0002210395650000043
wherein k ispiRepresenting a voltage vector of vi(i-0, 1,2, …,7) new active power variation size, kqiRepresenting a voltage vector of vi(i is 0,1,2, …,7) and e is the amount of change in reactive power*kIs a three-phase voltage vector e on the network sidekIn kTsMagnitude of time, e'kRepresenting three-phase voltage vector e on network sidekVoltage vector obtained after 1/4 power grid cycles are delayed in kTsSize of the moment, ekFor grid side three-phase voltage vector at kTsMagnitude of time, vi *kFor converter output voltage vector vi kIn kTsSize of the moment, Pnew,kShowing the novel active power based on the theory of expanding the active power in kTsMagnitude of time, QkExpressing reactive power at kT based on the theory of expanding active powersThe magnitude of the time, R is the parasitic resistance of the net-side filterThe value, L is the inductance value of the grid side filter, ω is the grid angular frequency;
preferably, the analyzing the average power and the second harmonic component of the AC/DC converter under the unbalanced grid condition in step 3 specifically includes:
the novel active power and reactive power under the unbalanced grid voltage condition can be expressed as:
Figure BDA0002210395650000051
the average power and the second harmonic component of the novel instantaneous active power are as follows:
Figure BDA0002210395650000052
Figure BDA0002210395650000053
Figure BDA0002210395650000054
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component of the power grid current under the negative sequence rotating coordinate system,
Figure BDA0002210395650000055
is a direct current component of the novel active power,
Figure BDA0002210395650000056
the cosine coefficient of the double frequency component of the active power,
Figure BDA0002210395650000057
the sine term coefficient is a frequency doubling component of the novel active power;
Figure BDA0002210395650000058
the average power and the second harmonic component of the instantaneous reactive power are:
Figure BDA0002210395650000059
Figure BDA00022103956500000510
Figure BDA00022103956500000511
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component, Q, of the grid current in a negative sequence rotating coordinate system0Being a direct component of reactive power, Qc2Coefficient of the cosine term of the double frequency component of the reactive power, Qs2The coefficient is a sine term of a frequency doubling component of the reactive power;
by comparison, it can be seen that,
Figure BDA0002210395650000061
and
Figure BDA0002210395650000062
that is, under the condition of an unbalanced power grid, the novel 2-frequency multiplication fluctuation of active power is eliminated, and simultaneously the 2-frequency multiplication fluctuation of reactive power is also eliminated;
preferably, in step 4, in order to eliminate the active power ripple and obtain the unity power factor, the sine of the grid current is ensured, and the equation can be described as follows:
Figure BDA0002210395650000063
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay; i.e. iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβIs the grid current value i 'of the three-phase grid current corresponding to the beta axis'αIs the value of the grid voltage i 'on the delayed alpha axis'βThe value is the power grid voltage value on the beta axis after time delay;
Figure BDA0002210395650000064
the reference value of the novel active power is obtained;
solving the corresponding reference current as follows:
Figure BDA0002210395650000065
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βFor the value of the grid voltage on the beta axis after the delay,
Figure BDA0002210395650000066
is a reference value of the novel active power,
Figure BDA0002210395650000067
for the reference value of the three-phase grid current corresponding to the grid current on the alpha axis,
Figure BDA0002210395650000068
corresponding the three-phase grid current to the reference value of the grid current on the beta axis;
obtaining a current reference value according to calculation, eliminating active power pulsation based on an extended instantaneous active power theory, obtaining a unit power factor, and ensuring the sine of the current of the power grid, wherein the power compensation size is as follows:
Figure BDA0002210395650000069
wherein the content of the first and second substances,
Figure BDA00022103956500000610
reference value, Q, for new active powerrefIs a reference value of reactive power, PcompMagnitude of compensation for new active power, QcompThe compensation quantity is the reactive power; by comparison, the control target of eliminating active power pulsation, obtaining unit power factor and ensuring power grid current sine is realized on the basis of an expansion instantaneous active power theory under the condition of an unbalanced power grid, and extra power compensation is not needed.
The step 4 of establishing a novel active power deviation and reactive power deviation square sum minimum cost function model specifically comprises the following steps:
in each control period, two adjacent non-zero voltage vectors and a zero voltage vector are used for synthesizing an expected vector, and by using the slope magnitude of the novel active power and reactive power, the magnitude of the novel active power and reactive power at the end of each control period can be expressed as:
Figure BDA0002210395650000071
wherein, Pnew(k +1) is novel active power at (k +1) TsSize of (D), Pnew(k) For new active power in kTsSize of the time, kp1For the first acting non-zero voltage vector to the new active power variation, kp2Variation of novel active power for second acting non-zero voltage vectorAmount, kp0The variation of the zero vector to the novel active power; q (k +1) is reactive power at (k +1) TsThe magnitude of the time, Q (k), is the reactive power in kTsSize of the time, kq1For the variation of the first acting non-zero voltage vector on the reactive power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
after each control cycle is finished, the error amounts of the novel active power and the novel reactive power are respectively
Figure BDA0002210395650000072
Wherein, Δ PnewThe error magnitude of the novel active power is shown, the delta Q is the error magnitude of the reactive power,
Figure BDA0002210395650000073
reference value, Q, for new active powerrefIs a reference value of reactive power;
therefore, the cost function of the square sum of the active power deviation and the reactive power deviation established in step 4 is:
J(t1,t2)＝(ΔPnew)2+(ΔQ)2
preferably, the determining of the first acting non-zero voltage vector, the second acting non-zero voltage vector and the zero vector in step 5 is specifically as follows:
firstly, through the defined cost function, the minimum value of the cost function determined by traversing six non-zero voltage vectors is marked as JrAnd records the corresponding voltage vector VrI.e. a first acting non-zero voltage vector;
determining the second acting non-zero voltage vector taking into account VtMust be and VrTwo adjacent nonzeroVoltage vector Vr-1And Vr+1Then calculate V separatelyr-1,Vr+1Value of cost function Jr-1And Jr+1If the voltage vector V is non-zeror-1Corresponding cost function value Jr-1Greater than a non-zero voltage vector Vr+1Corresponding cost function value Jr+1Then V ist＝Vr+1Otherwise, Vt＝Vr-1；
Wherein the zero vector is selected based on the minimum switching principle, and when the determined second acting non-zero voltage vector is V2，V4And V6At that time, t is the very beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V7(ii) a When the determined second applied non-zero voltage vector is V1，V3And V5Then t is the beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V0；
The determined voltage vectors in step 5 have 8 voltage vectors, wherein six non-zero voltage vectors are:
V1＝(1,0,0),V2＝(1,1,0),V3＝(0,1,0),V4＝(0,1,1),V5＝(0,0,1),V6＝(1,0,1)；
the two zero voltage vectors in step 5 are:
V0＝(0,0,0),V7＝(1,1,1)；
preferably, in step 6, the optimal operation time of the first operation nonzero voltage vector, the second operation nonzero voltage vector and the zero voltage vector is as follows:
Figure BDA0002210395650000081
wherein the content of the first and second substances,
Figure BDA0002210395650000082
and is provided with
Θ＝kq0kp2-kq1kp2-kq2kp0+kq1kp0-kq0kp1+kq2kp1
Wherein k isp1For the first acting non-zero voltage vector to the new active power variation, kp2For the second acting non-zero voltage vector, kp0The variation of the zero vector to the novel active power; k is a radical ofq1For the variation of the first acting non-zero voltage vector on the reactive power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
Figure BDA0002210395650000091
reference value, Q, for new active powerrefIs a reference value of reactive power, TsRepresents a control period; pnew(k) To new active power kTsThe magnitude of the time, Q (k), is the reactive power kTsThe size of the moment;
suppose t1+t2>TsThen, the correction formula is:
Figure BDA0002210395650000092
thus, the action time of the zero voltage vector is:
t0＝Ts-t1-t2
step 7, after determining the action time of the first action nonzero voltage vector, the second action nonzero voltage vector and the zero voltage vector, sending a switching signal to suppress a second harmonic component of the novel active power of the AC/DC converter under the unbalanced grid voltage condition and reduce the harmonic content of the current on the grid side by using a space vector modulation method;
the method has the advantages that the control method does not need extra power compensation calculation, realizes unbalanced control under a static coordinate system, and has small power pulsation, small harmonic content of network side current and high precision.
Drawings
FIG. 1: optimizing and enhancing a control flow chart for three-vector prediction based on an extended active theory;
FIG. 2: the active power and reactive power results of the enhanced control based on the extended active theory;
FIG. 3: the three-phase voltage and three-phase current result of the enhanced control based on the extended active theory;
FIG. 4: the simulation result of the A-phase voltage and the A-phase current based on the extended active theory is obtained;
FIG. 5: phase current spectrum diagram.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical solution of the present invention is further specifically described by embodiments with reference to fig. 1 to 5. In the embodiment of the invention, in order to verify the effectiveness of the three-vector prediction optimization enhancement control algorithm based on the extended active power theory, a model of a three-phase two-level AC/DC converter is built for simulation verification.
In the embodiment of the present invention, an AC/DC converter system is constructed, including: the system comprises a three-phase alternating current power grid, a three-phase filter inductor, a three-phase voltage sensor, a three-phase current sensor, a direct current voltage sensor, a main controller, a three-phase AC/DC converter, a direct current side capacitor and a direct current side load;
the three-phase alternating current power grid is connected with the three-phase voltage sensor through a wire; the three-phase power grid is connected with the three-phase current sensor through a wire; the direct current side capacitor is connected with the direct current voltage sensor through a lead; the main controller is respectively connected with the three-phase voltage sensor, the three-phase current sensor and the direct current voltage sensor in sequence through leads; the main controller is connected with the three-phase AC/DC converter through a lead; the three-phase alternating current power grid, the three-phase filter inductor, the three-phase AC/DC converter, the direct current side capacitor and the direct current side load are sequentially connected in series through a lead.
The three-phase alternating current grid model is TSGC-9 kVA; the three-phase filter inductor is selected as GT-LOR-0012; the model of the three-phase voltage sensor is ZMPT 107; the three-phase current sensor is selected to be ZMCT 101B; the direct-current voltage sensor is selected from HCPL 7840; the master controller is TMS320F28069 in type selection; the three-phase AC/DC converter consists of six IGBTs, and the selection type of the IGBT is 2MBI200U 4H-170-50; the direct current side capacitor is selected to be an electrolytic capacitor of 2200 mu F; the DC side load is selected to be a 31 ohm resistor.
The flow chart of the three-vector prediction optimization enhancement control method based on the extended active power theory is shown in fig. 1. The unbalance degree of the power grid voltage is set to be 10%, the sampling frequency is 12.8kHz, the reference value of novel active power is 3000W, the reference value of reactive power is 0Var, the direct-current side capacitor is 2200 muF, the load resistor is 31 omega, and the positive sequence voltage amplitude V of the power grid is V+Set to 122.45V, negative sequence voltage magnitude V-Set to 12.245V. Further, the dc voltage is set to 300V, and it is assumed that the dc voltage is controlled by an inverter at the opposite end.
The following describes the embodiments of the present invention with reference to fig. 1 to 5:
step 1: collecting network side three-phase voltage, network side three-phase current and direct current side capacitor voltage, respectively converting abc coordinate systems of the network side three-phase voltage and the network side three-phase current into alpha beta coordinate systems by Clarke transformation, and obtaining voltage and direct current side capacitor voltage under a two-phase static coordinate systemCurrent flow; wherein, the positive sequence voltage amplitude V+122.45V, negative sequence voltage amplitude V—12.245V;
in the step 1, the three-phase voltage at the network side is as follows:
acquiring the three-phase voltage of the grid side through the three-phase voltage sensor;
the A-phase grid voltage is eaThe B-phase grid voltage is ebThe C-phase grid voltage is ec；
Collecting the three-phase current of the grid side through the three-phase current sensor;
in the step 1, the three-phase current at the network side is as follows:
the A-phase grid current is iaThe B-phase grid current is ibThe C-phase grid current is ic；
In the step 1, the voltage of the direct current side capacitor is as follows:
collecting the direct current side capacitance voltage through the direct current voltage sensor;
the voltage of the DC side capacitor is udc；
Transmitting the network side three-phase voltage, the network side three-phase current and the direct current side capacitor voltage to the main controller;
respectively converting an abc coordinate system of the three-phase voltage on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure BDA0002210395650000111
Figure BDA0002210395650000112
wherein e isαCorresponding three-phase voltage on grid side to grid voltage value on alpha axis, eβCorresponding the three-phase voltage on the network side to the voltage value of the power grid on the beta axis;
respectively converting an abc coordinate system of the three-phase current on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure BDA0002210395650000113
Figure BDA0002210395650000114
wherein iαThe grid side three-phase current corresponds to the grid current value i on the alpha axisβThe three-phase current at the network side corresponds to the current value of the power grid on a beta axis;
the grid-side three-phase voltage vector e can be expressed as:
e＝eα+jeβ
the grid-side three-phase current vector i can be expressed as:
i＝iα+jiβ
in addition, the amplitude and the phase angle of the three-phase voltage vector on the grid side are respectively as follows:
Figure BDA0002210395650000115
Figure BDA0002210395650000116
wherein E is the amplitude of the three-phase voltage vector on the network side, theta1Is the phase angle of the three-phase voltage vector at the network side;
step 2, establishing a novel mathematical model of active power and reactive power based on an extended instantaneous active power theory, wherein the expression is as follows:
Figure BDA0002210395650000121
wherein i*Is the conjugate of the grid-side three-phase current vector i, and e' represents the voltage vector obtained after the grid-side three-phase voltage vector e is delayed by 1/4 grid periods, PnewRepresenting novel active power based on extended instantaneous active power theory, Q representing being based on extended instantaneousReactive power of an active power theory, Im represents that an imaginary part is taken for a vector; e.g. of the typeαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβFor the three-phase network voltage to correspond to the network voltage value on the beta axis, iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβThe current value of the power grid corresponding to the three-phase power grid current on the beta axis is obtained; e'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay;
in step 2, the new active power and reactive power derivation is respectively:
Figure BDA0002210395650000122
wherein e is a three-phase voltage vector on the network side, e*Is the conjugate of a grid-side three-phase voltage vector e, e' represents a voltage vector obtained after the grid-side three-phase voltage vector e is delayed by 1/4 power grid periods, v is a converter output voltage vector, v*For the conjugate of the converter output voltage vector v, R is the parasitic resistance value of the grid-side filter, L is the inductance value of the grid-side filter, and ω is the grid angular frequency; in the invention, R is 0.3 omega, L is 10mH, and omega is 314 rad/s;
discretizing the derivative of the novel active power and the reactive power into:
Figure BDA0002210395650000123
wherein k ispiRepresenting a voltage vector of vi(i-0, 1,2, …,7) new active power variation size, kqiRepresenting a voltage vector of vi(i is 0,1,2, …,7) and e is the amount of change in reactive power*kIs a three-phase voltage vector e on the network sidekIn kTsMagnitude of time, e'kRepresenting three-phase voltage vector e on network sidekVoltage vector obtained after 1/4 power grid cycles are delayed in kTsSize of the moment, ekFor grid side three-phase voltage vector at kTsMagnitude of time, vi *kFor converter output voltage vector vi kIn kTsSize of the moment, Pnew,kShowing the novel active power based on the theory of expanding the active power in kTsMagnitude of time, QkExpressing reactive power at kT based on the theory of expanding active powersThe magnitude of the moment, R is the parasitic resistance value of the grid-side filter, L is the inductance value of the grid-side filter, and omega is the grid angular frequency; in the invention, R is 0.3 omega, L is 10mH, and omega is 314 rad/s;
and step 3: analyzing the composition of the average power and the second harmonic component of the AC/DC converter under the unbalanced power grid condition based on a novel mathematical model of active power and reactive power;
the analysis of the average power and the second harmonic component of the AC/DC converter under the unbalanced power grid condition in the step 3 specifically comprises the following steps:
the novel active power and reactive power under the unbalanced grid voltage condition can be expressed as:
Figure BDA0002210395650000131
the average power and the second harmonic component of the novel instantaneous active power are as follows:
Figure BDA0002210395650000132
Figure BDA0002210395650000133
Figure BDA0002210395650000134
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component of the power grid current under the negative sequence rotating coordinate system,
Figure BDA0002210395650000135
is a direct current component of the novel active power,
Figure BDA0002210395650000136
the cosine coefficient of the double frequency component of the active power,
Figure BDA0002210395650000137
the sine term coefficient is a frequency doubling component of the novel active power;
Figure BDA0002210395650000138
the average power and the second harmonic component of the instantaneous reactive power are:
Figure BDA0002210395650000141
Figure BDA0002210395650000142
Figure BDA0002210395650000143
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component, Q, of the grid current in a negative sequence rotating coordinate system0Being a direct component of reactive power, Qc2Coefficient of the cosine term of the double frequency component of the reactive power, Qs2The coefficient is a sine term of a frequency doubling component of the reactive power;
by comparison, it can be seen that,
Figure BDA0002210395650000144
and
Figure BDA0002210395650000145
that is, under the condition of an unbalanced power grid, the novel 2-frequency multiplication fluctuation of active power is eliminated, and simultaneously the 2-frequency multiplication fluctuation of reactive power is also eliminated;
and 4, step 4: based on the power analysis of a converter under the condition of an unbalanced power grid, a novel active power deviation and reactive power deviation square sum minimum cost function model is established by taking the elimination of double-frequency fluctuation of active power and the guarantee of the sine of current on the grid side as control targets;
in step 4, in order to eliminate active power pulsation and obtain a unit power factor and ensure the sine of the current of the power grid, the equation can be described as follows:
Figure BDA0002210395650000146
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay; i.e. iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβIs the grid current value i 'of the three-phase grid current corresponding to the beta axis'αIs the value of the grid voltage i 'on the delayed alpha axis'βThe value is the power grid voltage value on the beta axis after time delay;
Figure BDA0002210395650000147
the reference value of the novel active power is obtained;
solving the corresponding reference current as follows:
Figure BDA0002210395650000148
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βFor the value of the grid voltage on the beta axis after the delay,
Figure BDA0002210395650000151
is a reference value of the novel active power,
Figure BDA0002210395650000152
for the reference value of the three-phase grid current corresponding to the grid current on the alpha axis,
Figure BDA0002210395650000153
corresponding the three-phase grid current to the reference value of the grid current on the beta axis;
obtaining a current reference value according to calculation, eliminating active power pulsation based on an extended instantaneous active power theory, obtaining a unit power factor, and ensuring the sine of the current of the power grid, wherein the power compensation size is as follows:
Figure BDA0002210395650000154
wherein the content of the first and second substances,
Figure BDA0002210395650000155
reference value, Q, for new active powerrefIs a reference value of reactive power, PcompMagnitude of compensation for new active power, QcompThe compensation quantity is the reactive power; by comparison, the control target of eliminating active power pulsation, obtaining unit power factor and ensuring power grid current sine is realized on the basis of an expansion instantaneous active power theory under the condition of an unbalanced power grid, and extra power compensation is not needed.
The step 4 of establishing a novel active power deviation and reactive power deviation square sum minimum cost function model specifically comprises the following steps:
in each control period, two adjacent non-zero voltage vectors and a zero voltage vector are used for synthesizing an expected vector, and by using the slope magnitude of the novel active power and reactive power, the magnitude of the novel active power and reactive power at the end of each control period can be expressed as:
Figure BDA0002210395650000156
wherein, Pnew(k +1) is novel active power at (k +1) TsSize of (D), Pnew(k) For new active power in kTsSize of the time, kp1For the first acting non-zero voltage vector to the new active power variation, kp2For the second-acting non-zero voltage vector to the new active power variation, kp0The variation of the zero vector to the novel active power; q (k +1) is reactive power at (k +1) TsThe magnitude of the time, Q (k), is the reactive power in kTsSize of the time, kq1For the variation of the first acting non-zero voltage vector on the reactive power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
after each control cycle is finished, the error amounts of the novel active power and the novel reactive power are respectively
Figure BDA0002210395650000161
Wherein, Δ PnewThe error magnitude of the novel active power is shown, the delta Q is the error magnitude of the reactive power,
Figure BDA0002210395650000162
is newReference value of active power, QrefIs a reference value of reactive power;
therefore, the cost function of the square sum of the active power deviation and the reactive power deviation established in step 4 is:
J(t1,t2)＝(ΔPnew)2+(ΔQ)2
and 5: determining a first action nonzero voltage vector, a second action nonzero voltage vector and a zero voltage vector by utilizing a defined novel active power deviation and reactive power deviation square sum minimum cost function model;
in step 5, the determination of the first acting non-zero voltage vector, the second acting non-zero voltage vector and the zero vector is specifically as follows:
firstly, through the defined cost function, the minimum value of the cost function determined by traversing six non-zero voltage vectors is marked as JrAnd records the corresponding voltage vector VrI.e. a first acting non-zero voltage vector;
determining the second acting non-zero voltage vector taking into account VtMust be and VrTwo adjacent non-zero voltage vectors Vr-1And Vr+1Then calculate V separatelyr-1,Vr+1Value of cost function Jr-1And Jr+1If the voltage vector V is non-zeror-1Corresponding cost function value Jr-1 is greater than the non-zero voltage vector Vr+1Corresponding cost function value Jr+1Then V ist＝Vr+1Otherwise, Vt＝Vr-1；
Wherein the zero vector is selected based on the minimum switching principle, and when the determined second acting non-zero voltage vector is V2，V4And V6At that time, t is the very beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V7(ii) a When the determined second applied non-zero voltage vector is V1，V3And V5Then t is the beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V0；
The determined voltage vectors in step 5 have 8 voltage vectors, wherein six non-zero voltage vectors are:
V1＝(1,0,0),V2＝(1,1,0),V3＝(0,1,0),V4＝(0,1,1),V5＝(0,0,1),V6＝(1,0,1)；
the two zero voltage vectors in step 5 are:
V0＝(0,0,0),V7＝(1,1,1)；
step 6: respectively solving the partial derivatives of the defined novel active power deviation, reactive power deviation square and minimum cost function model to obtain a first action nonzero voltage vector, a second action nonzero voltage vector and the optimal action time of the zero voltage vector;
in step 6, the optimal action time of the first action non-zero voltage vector, the second action non-zero voltage vector and the zero voltage vector is as follows:
Figure BDA0002210395650000171
wherein the content of the first and second substances,
Figure BDA0002210395650000172
and is provided with
Θ＝kq0kp2-kq1kp2-kq2kp0+kq1kp0-kq0kp1+kq2kp1
Wherein k isp1For the first acting non-zero voltage vector to the new active power variation, kp2For the second acting non-zero voltage vector, kp0The variation of the zero vector to the novel active power; k is a radical ofq1For the first action non-zero voltage vector pairAmount of change in work power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
Figure BDA0002210395650000173
reference value, Q, for new active powerrefIs a reference value of reactive power, TsRepresents a control period; pnew(k) To new active power kTsThe magnitude of the time, Q (k), is the reactive power kTsThe size of the moment;
suppose t1+t2>TsThen, the correction formula is:
Figure BDA0002210395650000174
thus, the action time of the zero voltage vector is:
t0＝Ts-t1-t2
and 7: a switching signal is sent out by utilizing a space vector modulation method to inhibit a second harmonic component of novel active power of the AC/DC converter under the condition of unbalanced grid voltage and reduce the harmonic content of current on the grid side;
step 7, after determining the action time of the first action nonzero voltage vector, the second action nonzero voltage vector and the zero voltage vector, sending a switching signal to suppress a second harmonic component of the novel active power of the AC/DC converter under the unbalanced grid voltage condition and reduce the harmonic content of the current on the grid side by using a space vector modulation method;
the simulation results of the three-vector prediction optimization enhancement control method based on the extended active theory are shown in fig. 2 to 5. Fig. 2 shows results of novel active power, conventional active power and reactive power under an unbalanced grid condition, fig. 3 shows simulation results of voltage and current of a three-phase grid under the unbalanced grid condition, fig. 4 is a phase diagram of voltage and current of an a-phase grid side, and fig. 5 is a frequency spectrum diagram of current under the unbalanced grid condition. As shown in fig. 2 and fig. 3, the new active power and reactive power of the three-vector prediction optimization enhanced control strategy based on the extended active theory can be controlled to be constant and effectively track their reference values, and the power ripple is small, the net side current is sinusoidal, and the control precision is high, but at this time, the traditional active power has larger power ripple. As can be seen from fig. 4, the grid-side voltage and the grid-side current are in phase, so the proposed control method can realize the unit power operation of the AC/DC converter. Under the condition of unbalanced grid voltage, the harmonic content of the grid-side current is higher due to the action of the negative sequence component, but the enhanced control strategy provided by the invention can not only make the grid-side current sinusoidal, but also make the harmonic content very low, which is only 0.54%, as shown in fig. 5.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
It should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (1)

1. An enhancement control method of three-vector prediction optimization based on an extended active power theory is characterized by comprising the following steps:
step 1: collecting network side three-phase voltage, network side three-phase current and direct current side capacitor voltage, and respectively converting abc coordinate systems of the network side three-phase voltage and the network side three-phase current into an alpha beta coordinate system by using Clarke transformation so as to obtain voltage and current under a two-phase static coordinate system;
step 2: establishing a novel mathematical model of active power and reactive power of the grid-side two-phase static coordinate system based on an extended instantaneous active power theory according to the voltage and the current of the grid-side two-phase static coordinate system, and respectively deriving and discretizing;
the novel active power definition based on the extended instantaneous active theory is the inverse number of the cross product of a current signal and a voltage quarter-cycle delay signal;
the reactive power definition based on the extended instantaneous active power theory is consistent with the reactive power definition based on the traditional instantaneous power theory;
step 2, establishing a novel mathematical model of active power and reactive power based on an extended instantaneous active power theory, wherein the expression is as follows:
Figure FDA0003015198650000011
wherein i*Is the conjugate of the grid-side three-phase current vector i, and e' represents the voltage vector obtained after the grid-side three-phase voltage vector e is delayed by 1/4 grid periods, PnewRepresenting the novel active power based on the extended instantaneous active power theory in the step 2, Q representing the reactive power based on the extended instantaneous active power theory in the step 2, and Im representing the imaginary part of the vector; e.g. of the typeαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβFor the three-phase network voltage to correspond to the network voltage value on the beta axis, iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβThe current value of the power grid corresponding to the three-phase power grid current on the beta axis is obtained; e'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay;
in step 2, the new active power and reactive power derivation is respectively:
Figure FDA0003015198650000012
wherein e is a three-phase voltage vector on the network side, e*Is the conjugate of the grid-side three-phase voltage vector e, and e' represents the result obtained after the grid-side three-phase voltage vector e is delayed by 1/4 grid cyclesV is the converter output voltage vector, v*For the conjugate of the converter output voltage vector v, R is the parasitic resistance value of the grid-side filter, L is the inductance value of the grid-side filter, and ω is the grid angular frequency;
discretizing the derivative of the novel active power and the reactive power into:
Figure FDA0003015198650000021
wherein k ispiRepresenting a voltage vector of vi(i-0, 1,2, …,7) new active power variation size, kqiRepresenting a voltage vector of vi(i is 0,1,2, …,7) and e is the amount of change in reactive power*kIs a three-phase voltage vector e on the network sidekIn kTsMagnitude of time, e'kRepresenting three-phase voltage vector e on network sidekVoltage vector obtained after 1/4 power grid cycles are delayed in kTsSize of the moment, ekFor grid side three-phase voltage vector at kTsMagnitude of time, vi *kFor converter output voltage vector vi kIn kTsSize of the moment, Pnew,kShowing the novel active power based on the theory of expanding the active power in kTsMagnitude of time, QkExpressing reactive power at kT based on the theory of expanding active powersThe magnitude of the moment, R is the parasitic resistance value of the grid-side filter, L is the inductance value of the grid-side filter, and omega is the grid angular frequency;
and step 3: analyzing the composition of the average power and the second harmonic component of the AC/DC converter under the unbalanced power grid condition based on a novel mathematical model of active power and reactive power;
and 4, step 4: based on the power analysis of a converter under the condition of an unbalanced power grid, a novel active power deviation and reactive power deviation square sum minimum cost function model is established by taking the elimination of double-frequency fluctuation of active power and the guarantee of the sine of current on the grid side as control targets;
and 5: determining a first action nonzero voltage vector, a second action nonzero voltage vector and a zero voltage vector by utilizing a defined novel active power deviation and reactive power deviation square sum minimum cost function model;
step 6: respectively solving the partial derivatives of the defined novel active power deviation, reactive power deviation square and minimum cost function model to obtain a first action nonzero voltage vector, a second action nonzero voltage vector and the optimal action time of the zero voltage vector;
and 7: a switching signal is sent out by utilizing a space vector modulation method to inhibit a second harmonic component of novel active power of the AC/DC converter under the condition of unbalanced grid voltage and reduce the harmonic content of current on the grid side;
in the step 1, the three-phase voltage at the network side is as follows:
collecting the three-phase voltage of the grid side through a three-phase voltage sensor;
the A-phase grid voltage is eaThe B-phase grid voltage is ebThe C-phase grid voltage is ec；
Collecting the three-phase current of the grid side through a three-phase current sensor;
in the step 1, the three-phase current at the network side is as follows:
the A-phase grid current is iaThe B-phase grid current is ibThe C-phase grid current is ic；
In the step 1, the voltage of the direct current side capacitor is as follows:
collecting the direct current side capacitance voltage through a direct current voltage sensor;
the voltage of the DC side capacitor is udc；
Transmitting the network side three-phase voltage, the network side three-phase current and the direct current side capacitor voltage to a main controller;
respectively converting an abc coordinate system of the three-phase voltage on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure FDA0003015198650000031
Figure FDA0003015198650000032
wherein e isαCorresponding three-phase voltage on grid side to grid voltage value on alpha axis, eβCorresponding the three-phase voltage on the network side to the voltage value of the power grid on the beta axis;
respectively converting an abc coordinate system of the three-phase current on the grid side into an alpha beta coordinate system by Clarke transformation, wherein the method comprises the following steps:
Figure FDA0003015198650000033
Figure FDA0003015198650000034
wherein iαThe grid side three-phase current corresponds to the grid current value i on the alpha axisβThe three-phase current at the network side corresponds to the current value of the power grid on a beta axis;
the grid-side three-phase voltage vector e can be expressed as:
e＝eα+jeβ
the grid-side three-phase current vector i can be expressed as:
i＝iα+jiβ
in addition, the amplitude and the phase angle of the three-phase voltage vector on the grid side are respectively as follows:
Figure FDA0003015198650000035
Figure FDA0003015198650000036
wherein E is the amplitude of the three-phase voltage vector on the network side, theta1Is the phase angle of the three-phase voltage vector at the network side;
the analysis of the average power and the second harmonic component of the AC/DC converter under the unbalanced power grid condition in the step 3 specifically comprises the following steps:
the novel active power and reactive power under the unbalanced grid voltage condition can be expressed as:
Figure FDA0003015198650000041
the average power and the second harmonic component of the novel instantaneous active power are as follows:
Figure FDA0003015198650000042
Figure FDA0003015198650000043
Figure FDA0003015198650000044
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component of the power grid current under the negative sequence rotating coordinate system,
Figure FDA0003015198650000045
is a direct current component of the novel active power,
Figure FDA0003015198650000046
the cosine coefficient of the double frequency component of the active power,
Figure FDA0003015198650000047
is a double frequency of the novel active powerSinusoidal term coefficients of the components;
Figure FDA0003015198650000048
the average power and the second harmonic component of the instantaneous reactive power are:
Figure FDA0003015198650000049
Figure FDA00030151986500000410
Figure FDA00030151986500000411
wherein e isdq +Is the positive sequence component of the grid voltage under the positive sequence rotating coordinate system idq +Is the positive sequence component of the grid current in a positive sequence rotating coordinate system, edq -Is the negative sequence component of the grid voltage under the negative sequence rotating coordinate system idq -Is the negative sequence component, Q, of the grid current in a negative sequence rotating coordinate system0Being a direct component of reactive power, Qc2Coefficient of the cosine term of the double frequency component of the reactive power, Qs2The coefficient is a sine term of a frequency doubling component of the reactive power;
by comparison, it can be seen that,
Figure FDA0003015198650000051
and
Figure FDA0003015198650000052
that is, under the condition of an unbalanced power grid, the novel 2-frequency multiplication fluctuation of the active power is eliminated, and the 2-frequency multiplication fluctuation of the reactive power is also eliminated;
in step 4, in order to eliminate active power pulsation and obtain a unit power factor and ensure the sine of the current of the power grid, the equation can be described as follows:
Figure FDA0003015198650000053
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βThe value is the power grid voltage value on the beta axis after time delay; i.e. iαIs the power grid current value i of the three-phase power grid current corresponding to the alpha axisβIs the grid current value i 'of the three-phase grid current corresponding to the beta axis'αIs the value of the grid voltage i 'on the delayed alpha axis'βThe value is the power grid voltage value on the beta axis after time delay;
Figure FDA0003015198650000054
the reference value of the novel active power is obtained;
solving the corresponding reference current as follows:
Figure FDA0003015198650000055
wherein e isαFor the three-phase network voltage to correspond to the network voltage value on the alpha axis, eβMapping the three-phase mains voltage to the mains voltage value, e 'on the β -axis'αIs the value of the grid voltage on the delayed alpha axis, e'βFor the value of the grid voltage on the beta axis after the delay,
Figure FDA0003015198650000056
is a reference value of the novel active power,
Figure FDA0003015198650000057
for the reference value of the three-phase grid current corresponding to the grid current on the alpha axis,
Figure FDA0003015198650000058
corresponding the three-phase grid current to the reference value of the grid current on the beta axis;
obtaining a current reference value according to calculation, eliminating active power pulsation based on an extended instantaneous active power theory, obtaining a unit power factor, and ensuring the sine of the current of the power grid, wherein the power compensation size is as follows:
Figure FDA0003015198650000061
wherein the content of the first and second substances,
Figure FDA0003015198650000062
reference value, Q, for new active powerrefIs a reference value of reactive power, PcompMagnitude of compensation for new active power, QcompThe compensation quantity is the reactive power; by comparison, based on the theory of expanding instantaneous active power under the condition of an unbalanced power grid, the control targets of eliminating active power pulsation, obtaining unit power factor and ensuring the sine of the current of the power grid are taken, and extra power compensation is not needed;
the step 4 of establishing a novel active power deviation and reactive power deviation square sum minimum cost function model specifically comprises the following steps:
in each control period, two adjacent non-zero voltage vectors and a zero voltage vector are used for synthesizing an expected vector, and by using the slope magnitude of the novel active power and reactive power, the magnitude of the novel active power and reactive power at the end of each control period can be expressed as:
Figure FDA0003015198650000063
wherein, Pnew(k +1) is novel active power at (k +1) TsSize of (D), Pnew(k) For new active power in kTsSize of the time, kp1Is as followsOne-action non-zero voltage vector to the variation, k, of the new active powerp2For the second-acting non-zero voltage vector to the new active power variation, kp0The variation of the zero vector to the novel active power; q (k +1) is reactive power at (k +1) TsThe magnitude of the time, Q (k), is the reactive power in kTsSize of the time, kq1For the variation of the first acting non-zero voltage vector on the reactive power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
after each control cycle is finished, the error amounts of the novel active power and the novel reactive power are respectively
Figure FDA0003015198650000064
Wherein, Δ PnewThe error magnitude of the novel active power is shown, the delta Q is the error magnitude of the reactive power,
Figure FDA0003015198650000071
reference value, Q, for new active powerrefIs a reference value of reactive power;
therefore, the cost function of the square sum of the active power deviation and the reactive power deviation established in step 4 is:
J(t1,t2)＝(ΔPnew)2+(ΔQ)2；
in step 5, the determination of the first acting non-zero voltage vector, the second acting non-zero voltage vector and the zero vector is specifically as follows:
firstly, through the defined cost function, the minimum value of the cost function determined by traversing six non-zero voltage vectors is marked as JrAnd records the corresponding voltage vector VrI.e. a first acting non-zero voltage vector;
determining the second acting non-zero voltage vector taking into account VtMust be and VrTwo adjacent non-zero voltage vectors Vr-1And Vr+1Then calculate V separatelyr-1,Vr+1Value of cost function Jr-1And Jr+1If the voltage vector V is non-zeror-1Corresponding cost function value Jr-1Greater than a non-zero voltage vector Vr+1Corresponding cost function value Jr+1Then V ist＝Vr+1Otherwise, Vt＝Vr-1；
Wherein the zero vector is selected based on the minimum switching principle, and when the determined second acting non-zero voltage vector is V2，V4And V6At that time, t is the very beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V7(ii) a When the determined second applied non-zero voltage vector is V1，V3And V5Then t is the beginning0T 4 and last t0The voltage vector of/4 is V0At t0/4+t1/2+t2/2+t0The zero voltage vector at the time point/2 is V0；
The voltage variables determined in step 5 have 8 voltage vectors, wherein the six non-zero voltage vectors are as follows:
V1＝(1,0,0),V2＝(1,1,0),V3＝(0,1,0),V4＝(0,1,1),V5＝(0,0,1),V6＝(1,0,1)；
in step 5, the two zero voltage vectors are:
V0＝(0,0,0),V7＝(1,1,1)；
in step 6, the optimal action time of the first action non-zero voltage vector, the second action non-zero voltage vector and the zero voltage vector is as follows:
Figure FDA0003015198650000072
wherein the content of the first and second substances,
Figure FDA0003015198650000073
and is provided with
Θ＝kq0kp2-kq1kp2-kq2kp0+kq1kp0-kq0kp1+kq2kp1
Wherein k isp1For the first acting non-zero voltage vector to the new active power variation, kp2For the second acting non-zero voltage vector, kp0The variation of the zero vector to the novel active power; k is a radical ofq1For the variation of the first acting non-zero voltage vector on the reactive power, kq2For the variation of the second acting non-zero voltage vector to the reactive power, kq0The variation of the zero vector to the reactive power; t is t1Is the magnitude of the first acting non-zero voltage vector2Is the magnitude of the second acting non-zero voltage vector0The action time size of the zero vector;
Figure FDA0003015198650000081
reference value, Q, for new active powerrefIs a reference value of reactive power, TsRepresents a control period; pnew(k) To new active power kTsThe magnitude of the time, Q (k), is the reactive power kTsThe size of the moment;
suppose t1+t2>TsThen, the correction formula is:
Figure FDA0003015198650000082
thus, the action time of the zero voltage vector is:
t0＝Ts-t1-t2；
and 7, after determining the action time of the first action non-zero voltage vector, the second action non-zero voltage vector and the zero voltage vector, sending a switching signal to inhibit a second harmonic component of the novel active power of the AC/DC converter under the condition of unbalanced grid voltage and reduce the harmonic content of the current on the grid side by using a space vector modulation method.
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