CN109546874B - Source-load decoupling model modeling method for independent power system with pulse load - Google Patents

Source-load decoupling model modeling method for independent power system with pulse load Download PDF

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CN109546874B
CN109546874B CN201811390711.9A CN201811390711A CN109546874B CN 109546874 B CN109546874 B CN 109546874B CN 201811390711 A CN201811390711 A CN 201811390711A CN 109546874 B CN109546874 B CN 109546874B
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axis
voltage
load
source
current
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CN109546874A (en
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王勇
刘正春
尹志勇
刘金宁
谷志峰
郭利
王文婷
汪雄剑
安树
曹曼
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Army Engineering University of PLA
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/162—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/34—Modelling or simulation for control purposes
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC

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  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

The invention discloses a source load decoupling model modeling method of an independent power system with a pulse load, and relates to the technical field of motor control models. The method comprises the following steps: simplifying an equivalent model by using a synchronous generator, and constructing a coupling equivalent model of the synchronous generator and a pulse load; deriving a source load coupling relation of alternating current and direct current side voltage and current of a coupling equivalent circuit model of the synchronous generator and the pulse load by introducing three bridge arm switching functions of the rectifier; and (3) enabling the power supply to be equivalent to an ideal voltage source by enabling the internal impedance of the alternating current side to be equivalent to the direct current side, and constructing the source-loaded decoupling model. The method can reflect the details of the influence of source-load coupling on the DC side operation mechanism, and can reduce the analysis difficulty.

Description

Source-load decoupling model modeling method for independent power system with pulse load
Technical Field
The invention relates to the technical field of motor control models, in particular to a source load decoupling model modeling method for an independent power system with a pulse load.
Background
At present, the operation characteristic research of PL-IPS (IPS refers to an independent power system, i.e. IPS with pulse Load) is to independently model and analyze a source end (generator set) or a Load end (rectification type pulse Load), and the mathematical correlation and the coupling rule between the source and the Load are not deeply considered. The source-to-load coupling relationship of PL-IPS can not only affect the power output and performance of the pulse load, but also affect the operation characteristics and stability of the system and the power supply. However, considering the source-to-source coupling increases the difficulty of theoretical analysis of the system.
Disclosure of Invention
The invention aims to solve the technical problem of how to provide a source load decoupling model modeling method of an independent power system with a pulse load, which can reflect the influence details of source load coupling on a direct current side running mechanism and reduce the analysis difficulty.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a source-borne decoupling model modeling method of an independent power system with a pulse load is characterized by comprising the following steps:
simplifying an equivalent model by using a synchronous generator, and constructing a coupling equivalent model of the synchronous generator and a pulse load;
deriving a source load coupling relation of alternating current and direct current side voltage and current of a coupling equivalent circuit model of the synchronous generator and the pulse load by introducing three bridge arm switching functions of the rectifier;
and (3) enabling the power supply to be equivalent to an ideal voltage source by enabling the internal impedance of the alternating current side to be equivalent to the direct current side, and constructing the source-loaded decoupling model.
The further technical scheme is as follows: the coupling equivalent model of the synchronous generator and the pulse load is constructed by the following method:
simplifying the synchronous generator, and constructing a rotor loop flux linkage equation of the synchronous generator as follows:
Figure BDA0001873999010000021
wherein the content of the first and second substances,
Figure BDA0001873999010000022
are d-axis exciters respectivelyThe magnetic flux linkage comprises a magnetic winding flux linkage, a q-axis short-circuit winding current flux linkage, a d-axis damping winding flux linkage and a q-axis damping winding flux linkage; i.e. ifd、ifq、ikd、ikqD-axis excitation winding current, q-axis short-circuit winding current, d-axis damping winding current and q-axis damping winding current respectively; i.e. id、iqRespectively outputting d-axis current and q-axis current for the unit;
Figure BDA0001873999010000023
and
Figure BDA0001873999010000024
are respectively ifd、ifq、idAnd iqThe non-periodic component of (a); x is the number offds、xfqs、xkds、xkqsLeakage reactance of a d-axis excitation winding, a q-axis short-circuit winding, a d-axis damping winding and a q-axis damping winding are respectively arranged; x is the number ofadD-axis armature reaction synchronous reactance is the mutual reactance of three windings of the d axis; x is the number ofaqThe q-axis armature reaction synchronous reactance is the mutual reactance of the three windings of the q axis;
obtaining i from equation (1)fd、ikd、ifqAnd ikqAnd then, substituting the Park flux linkage equation to obtain the d and q axis flux linkage formula as follows:
Figure BDA0001873999010000025
wherein the content of the first and second substances,
Figure BDA0001873999010000026
is a magnetic linkage of the d-axis,
Figure BDA0001873999010000027
is a q-axis flux linkage, xd、xqAre respectively d-axis and q-axis winding self-inductance, x "d、x”qD-axis and q-axis super-transient equivalent reactances respectively;
the current equation between the phases c and a is as follows:
Figure BDA0001873999010000028
wherein idcThe rotor angle is theta, namely theta is the rotor angle, namely omega t;
substituting the formula (2) and the formula (3) into a voltage equation of the motor, the d-axis voltage and the q-axis voltage can be obtained as follows:
Figure BDA0001873999010000031
wherein u isdFor d-axis voltage, u, of a synchronous generatorqIs the q-axis voltage of the synchronous generator, and r is the armature resistance of the synchronous generator;
let x "d＝x”qThen, a simplified equivalent model of the synchronous generator is obtained as follows:
Figure BDA0001873999010000032
wherein u isa、ub、ucA phase voltage a, b phase voltage c and a phase voltage x respectively output by the AC side of the synchronous generatortFor commutation reactance, xt＝(x”d+x”q) 2; r is the armature resistance; e1The amplitude of the electromotive force of the synchronous generator is delta, and the initial phase angle of the synchronous generator is delta;
Figure BDA0001873999010000033
Figure BDA0001873999010000034
x'd、x'qd-axis and q-axis transient reactances respectively;
the pulse load rectifier in the independent power system adopts a three-phase bridge type full-control rectification structure, the conduction sequence of 6 thyristors is VT1 → VT2 → VT3 → VT4 → VT5 → VT6, a trigger angle α is set to be 0 degrees, the state switching frequency M in a cycle is set to be 6, and switching functions S of three bridge arms of abc are introduceda、Sb、Sc：
Figure BDA0001873999010000035
The power supply outputs an AC side voltage ua、ub、ucAnd the DC side voltage u of the pulse loaddcIs in the coupling relation of
udc＝Saua+Sbub+Scuc(7)
Substituting the formulas (5) and (6) into the formula (7) to obtain a DC side voltage udc
Figure BDA0001873999010000041
rs＝r，Ls＝xt；
Let the DC side current of the pulse load be idcThen the power supply outputs three-phase current i on the AC sidea、ib、icAnd the pulse load direct side current idcIs in the coupling relation of
ix＝Sxidc(x＝a,b,c) (9)
Equations (8) and (9) are source-to-load coupling equivalent models of the voltage and current of the synchronous generator (source end) and the pulse load (load end).
Preferably, the synchronous generator is simplified by:
1) ignoring non-periodic components of damping winding current
Figure BDA0001873999010000042
And
Figure BDA0001873999010000043
2) the influence of the rotor circuit on the alternating current is neglected.
The further technical scheme is as follows: the equivalent voltage of an ideal voltage source on the direct current side is obtained by the following method:
substituting formula (9) into formula (8), and obtaining the productCurrent side voltage udc
Figure BDA0001873999010000044
rs＝r，Ls＝xt；
Calculate to know Sa 2+Sb 2+Sc 22, and
Figure BDA0001873999010000045
to obtain
Figure BDA0001873999010000046
It can be known that Saea+Sbeb+ScecIs the equivalent voltage of an ideal voltage source on the direct current side of a pulse load.
The further technical scheme is that the formula of the source-borne decoupling model is as follows:
Figure BDA0001873999010000051
in the formula, ea、eb、ecIs an ideal voltage source, then Saea+Sbeb+ScecIs an ideal power supply voltage eabcEquivalent to the voltage on the DC side of the pulse load, let it be edc；(-2Ls(didc/dt)-2rsidc) Is the coupling voltage of the impedance in the power supply of the synchronous generator.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the method, the source-load coupling key parameters are equivalent to the load-end direct-current side from the source-end alternating-current side, so that the power supply is equivalent to an ideal power supply, the coupling relation between the source-end coupling key parameters and the load-end direct-current side is removed, the influence details of the source-load coupling on the load-end direct-current side operation mechanism can be reflected when the direct-current side is subjected to theoretical analysis, and the difficulty of the theoretical analysis can be reduced.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a schematic block diagram of a pulsed load in a method according to an embodiment of the invention;
FIG. 2 is a d-axis transient reactance equivalent circuit diagram in an embodiment of the present invention;
FIG. 3 is a q-axis transient reactance equivalent circuit diagram in an embodiment of the present invention;
FIG. 4 is an equivalent circuit diagram of a PL-IPS source-to-load coupling model in an embodiment of the present invention;
FIG. 5 shows u in an embodiment of the present inventiondcAnd u⊥ dc ofA waveform diagram;
FIG. 6 is an equivalent circuit diagram of a decoupling model of a PL-IPS source load in an embodiment of the present invention;
fig. 7 is a flow chart of a method according to an embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention are 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.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
As shown in fig. 7, an embodiment of the present invention discloses a source-borne decoupling model modeling method for an independent power system with a pulse load, including the following steps:
simplifying an equivalent model by using a synchronous generator, and constructing a coupling equivalent model of the synchronous generator and a pulse load;
deriving a source load coupling relation of alternating current and direct current side voltage and current of a coupling equivalent circuit model of the synchronous generator and the pulse load by introducing three bridge arm switching functions of the rectifier;
and (3) enabling the power supply to be equivalent to an ideal voltage source by enabling the internal impedance of the alternating current side to be equivalent to the direct current side, and constructing the source-loaded decoupling model.
The above steps are described in detail with reference to the following specific contents:
pulse load definition and characterization:
the occurrence of impulse loads stems from special functional requirements such as high power impulse weapons, electromagnetic guns, radars, electromagnetic ejection devices, laser transmitters, and the like. With the development of high-power pulse technology, the control precision of the pulse load is improved, and the working frequency range is widened. The electrical characteristics of the pulse devices are characterized by low average power, high peak power and continuous periodic pulsation.
Through research on various equipment load characteristics, the load characteristics are defined as: after sudden change of the electrical characteristic parameter value within a short duration, the electrical characteristic parameter value quickly returns to the initial state, and the sudden change has high peak power, but low average power and certain periodic load. For example, the operating frequency of a phased array radar transmitter may reach 400Hz, the peak power may reach 50kW, and the average power may be only 2.8 kW. The pulsed load is characterized by:
(1) having a continuous periodicity, duty cycle TPLGenerally less than 1 s;
(2) the load state can change instantly, and the action time is short;
(3) the power change is fast, the peak power is very high, and the average power is lower;
according to the working frequency, the pulse load can be divided into a high-frequency pulse load (such as an AC-DC, a DC-AC converter and the like), a medium-frequency pulse load (such as a medium-frequency radar, an avionic load and the like) and a low-frequency pulse load (such as an electromagnetic gun, a ship electronic load and the like); according to the characteristics of the power supply, the load can be divided into alternating current and direct current pulse loads.
Typical structure of rectification type pulse load:
various pulse devices are complex in circuit structure and various in parameters, and the establishment of a pulse load typical structure is a precondition for researching PL-IPS source load coupling characteristics. Aiming at the rectification type pulse load, the method simplifies non-key parameters and characteristics, retains the external characteristics of power pulsation of the pulse load, and constructs a typical model structure.
Typical structure of rectification type pulse load:
the research on various pulse devices shows that due to the slow electromechanical regulation speed, the diesel generator set cannot directly provide instantaneous electric energy for the power transmitting module, and energy storage devices are inevitably added at the front end of the diesel generator set to provide instantaneous high-power pulses. Therefore, the typical structure of the rectification type pulse load can be described as a cascade structure of "ac side rectification module → energy storage unit → dc side pulse power consumption unit", as shown in fig. 1, wherein the dc side pulse power consumption unit can be simulated by switching a resistive load.
In the structure, a rectifier (wherein, a switch can select components such as a diode, a thyristor and an IGBT) is arranged on an alternating current side, and an energy storage unit adopts a capacitor CesEnergy storage (accumulator, super capacitor or other energy storage devices can be selected), direct current side inductor LdcFor filtering out DC side switch S1、S2Induced peak current, AC side inductance LsThe impulse current for smoothing the AC side simulates different power losses on the DC side by adjusting the size of the rheostat R. Analog controller output sequence sH、sLRespectively controlling switches S1、S2So as to simulate the high-frequency and low-frequency pulse characteristics of the pulse load.
Pulse characteristic simulation and model application range:
in order to generate the pulse characteristics shown in FIG. 1 for the DC side power, let g (t) be a unit period rectangular wave expression, there are
sH＝gH(t)，sL＝gL(t) (1)
gH(T) is a high-frequency periodic rectangular wave with a period THDuty ratio of rH；gL(T) is a high-frequency periodic rectangular wave with a period TLDuty ratio of rL. It can be seen that the waveform has both high and low frequency parameters, such as the repetition frequency f of the radar deviceLAnd carrier frequency fH. From this, a pulse power waveform p can be obtainedPLThe general expression for (t) is:
pPL(t)＝ppeak×gL(t)×gH(t) (2)
then its average power is:
PPL＝ppeak×rL×rH(3)
the formula is general and can represent the pulse power characteristic of the pulse load when r isHWhen 100%, there is gH(t) 1, then pPL(t)＝ppeak×gL(t), at this time, the pulse load continuously operates in a low-frequency period; when r isLWhen 100%, there is gL(t) 1, then pPL(t)＝ppeak×gH(t) when the pulsed load continues to operate in the high frequency mode.
For analytical convenience, two control switches S can be used1、S2As a switch S0Switching function of
s0(t)＝gH(t)×gL(t) (4)
s0(T) has a variable period TPL(frequency f)PL) And a duty cycle r.
As can be seen from the structure of FIG. 1, the DC side energy dissipation unit needs to bear the maximum pulse current, and the switch S is arranged at the position due to the requirement of high-frequency switching0IGBT devices are suitably selected. According to the voltage class of 600V-1700V and the power range of 60kW (100A/600V) -1020 kW (600A/1700V) of the IGBT device commonly used in the market at present, the structure is suitable for simulating rectification type pulse equipment in the occasions of medium and small power (the peak power is less than 1MW) and low voltage (the voltage on the direct current side is less than 2 kV).
PL-IPS source-borne coupling mathematical model establishment:
the PL-IPS diesel generator set is limited in capacity and small in inertia coefficient, the effective value of bus voltage is prone to fluctuation caused by continuous and periodic power fluctuation of a pulse load, the bus voltage supplies power to the direct current side of the pulse load through a rectifier, and fluctuation of the bus voltage further causes fluctuation of load power and peak power, so that power oscillation of the whole system is aggravated. This relationship between load operating characteristics and power supply operating characteristics is referred to as "source-to-load coupling".
The operation characteristics and rules of the PL-IPS are different from those of a public network system due to the strong source load coupling, so that when the PL-IPS is subjected to theoretical analysis, the operation characteristics of the pulse load can not be discussed independently without a power supply, and the operation characteristics of the diesel generator set can not be discussed independently without a load. The PL-IPS source load coupling mathematical relationship is deduced to find out the coupling relationship of source load key parameters (voltage, frequency and power), and a theoretical basis is laid for the PL-IPS AC/DC side transient and steady state operation characteristic research.
The synchronous generator and the pulse load coupling equivalent circuit:
when a large power grid system is modeled, an ideal voltage source is often adopted as a power supply; in a stand-alone power system with low inertia, this process does not reflect stability problems in the system. The mechanical processes of a synchronous generator are slower than the electromagnetic processes, so that at the instant of disturbance occurrence, its operating characteristics depend mainly on the variations of the respective electromagnetic quantities.
The essential simplification is first made to the synchronous generator ① ignoring the aperiodic component i of the damping winding currentkdAnd ikq(faster decay); ② neglecting the effect of the rotor circuit on the alternating current; ③ xadThe synchronous reactance is a d-axis armature reaction synchronous reactance, namely the mutual reactance of three windings (a d axis, excitation and damping) of the d axis; x is the number ofaqThe reactance is a q-axis armature reaction synchronous reactance, namely the mutual reactance of three q-axis windings (q-axis equivalent damping with a larger time constant corresponding to a transient process and equivalent damping with a smaller time constant corresponding to a sub-transient process). The rotor loop flux linkage equation is:
Figure BDA0001873999010000091
wherein the content of the first and second substances,
Figure BDA0001873999010000092
respectively a d-axis excitation winding flux linkage, a q-axis short-circuit winding current flux linkage, a d-axis damping winding flux linkage and a q-axis damping winding flux linkage; i.e. ifd、ifq、ikd、ikqD-axis excitation winding current, q-axis short-circuit winding current, d-axis damping winding current and q-axis damping winding current respectively; i.e. id、iqRespectively outputting d-axis current and q-axis current for the unit;
Figure BDA0001873999010000093
and
Figure BDA0001873999010000094
are respectively ifd、ifq、idAnd iqThe non-periodic component of (a); x is the number offds、xfqs、xkds、xkqsLeakage reactance of a d-axis excitation winding, a q-axis short-circuit winding, a d-axis damping winding and a q-axis damping winding are respectively arranged; x is the number ofadD-axis armature reaction synchronous reactance is the mutual reactance of three windings of the d axis; x is the number ofaqThe q-axis armature reaction synchronous reactance is the mutual reactance of the three windings of the q axis; d. the q-axis transient reactance equivalent circuit is shown in fig. 3.
Obtaining i from equation (5)fd、ikd、ifqAnd ikqAnd then, substituting the Park flux linkage equation to obtain the flux linkage formulas of the d axis and the q axis as follows:
Figure BDA0001873999010000101
wherein the content of the first and second substances,
Figure BDA0001873999010000102
is a magnetic linkage of the d-axis,
Figure BDA0001873999010000103
is a q-axis flux linkage, xd、xqAre respectively d-axis and q-axis winding self-inductance, x "d、x”qD-axis and q-axis super-transient equivalent reactances respectively;
(one) current equation during commutation, c phase → a phase as an example, when:
Figure BDA0001873999010000104
wherein idcFor rectifying the system dc side current, θ is the rotor angle, i.e., θ ═ ω t.
Substituting the equation (6) and the equation (7) into the voltage equation of the motor, the voltage equation of the d and q axes can be obtained as follows:
Figure BDA0001873999010000105
wherein u isdFor d-axis voltage, u, of a synchronous generatorqIs the q-axis voltage of the synchronous generator, and r is the armature resistance of the synchronous generator;
let x "d＝x”qThen, then
Figure BDA0001873999010000106
Wherein u isa、ub、ucA phase voltage a, b phase voltage c and a phase voltage x respectively output by the AC side of the synchronous generatortFor commutation reactance, xt＝(x”d+x”q) 2; r is the armature resistance; e1The electromotive force amplitude of the synchronous generator is delta, and the initial phase angle of the synchronous generator is delta.
Figure BDA0001873999010000111
Figure BDA0001873999010000112
x'd、x'qD-axis and q-axis transient reactances respectively;
(II) Voltage equation during conduction, taking conduction of phases a and b as an example, in this case
Figure BDA0001873999010000113
Substituting the equations (6) and (10) into the voltage equation of the motor can obtain
Figure BDA0001873999010000114
Also let x "d＝x”qThen, then
Figure BDA0001873999010000115
Comparing the equations (9) and (12), it can be seen that the output voltage equations of the synchronous generator during the commutation and conduction are the same, i.e. both can be expressed as an ideal voltage source eabc(t) is connected with the internal impedance in series, and r is used for distinguishing internal parameters of the source end and the carrier end convenientlysR (armature resistance), Ls＝xt(commutation reactance having a value of (x) "d+x”q) And/2), a synchronous generator and pulse load equivalent circuit model, namely a PL-IPS source load coupling model is shown in FIG. 4.
PL-IPS key parameter source carries coupling relation:
based on the PL-IPS source-to-load coupling model shown in FIG. 4, a source-to-load coupling mathematical relation of key parameters (voltage, power and frequency) of PL-IPS is further deduced.
Derivation of source-carried voltage coupling relation:
1. source-load coupling relation of pulse load direct-current side voltage
For the convenience of derivation, the rectifier in fig. 4 adopts a simpler three-phase bridge full-control rectification structure, the conduction sequence of 6 thyristors is VT1 → VT2 → VT3 → VT4 → VT5 → VT6, the firing angle α is set to 0 °, the number of state switching times in a cycle is set to 6 (6-pulse rectification circuit, if 12-pulse rectification is adopted, M is 12), and the switching functions S of three bridge arms abc are introduceda、Sb、Sc：
Figure BDA0001873999010000121
Then electricity is generatedSource output ac side voltage ua、ub、ucEquivalent to DC side voltage udcComprises the following steps:
udc＝Saua+Sbub+Scuc(14)
let the DC side current of the pulse load be idcThen, the AC side current ia、ib、icIs composed of
ix＝Sxidc(x＝a,b,c) (15)
Substituting the formulae (12), (13) and (15) into the formula (14) to obtain a DC side voltage udc
Figure BDA0001873999010000122
Calculate to know Sa 2+Sb 2+Sc 22, and
Figure BDA0001873999010000123
to obtain
Figure BDA0001873999010000124
Equations (16) and (15) are source-to-load coupling equivalent models of the voltage and the current of the synchronous generator (source end) and the pulse load (load end).
It can be known that Saea+Sbeb+ScecFor an equivalent voltage of an ideal voltage source on the dc side of a pulsed load, the equation indicates: load side DC side voltage udcIs determined by the equivalent internal impedance of the unit.
The source-load coupling relation of the output voltage of the power supply is as follows:
the expression of the instantaneous value of the three-phase voltage of the known synchronous generator is ua、ub、ucTransformed into ud, u by synchronous coordinatesq：
Figure BDA0001873999010000131
Wherein, VtThe voltage amplitude of the generator terminal phase is equal to the effective value U of the power supply
Figure BDA0001873999010000139
And (4) doubling. From the above formula can be seen
Figure BDA0001873999010000132
Then, the formula (16) is substituted into the formula (12) and then substituted into the formula (18) to obtain the product
Figure BDA0001873999010000133
Calculate to know Sa 2+Sb 2+Sc 22 and SaSb+SbSc+ScSa1, de ═ 1
Figure BDA0001873999010000134
In a clear view of the above, it is known that,
Figure BDA0001873999010000135
the amplitude of the phase voltage of the ideal voltage source is set to be
Figure BDA0001873999010000136
U0Is an ideal effective value of voltage source, having
Figure BDA0001873999010000137
Then there is
Figure BDA0001873999010000138
The formula indicates that: the amplitude V of the output voltage of the synchronous generator is obtained due to the equivalent internal impedance of the diesel generator settLoaded DC side voltage idcThe influence of (c).
Therefore, the equations (16) and (19) are source-to-source voltage coupling equations for PL-IPS. The formula shows that the voltage amplitude V of the output phase of the power supplyt(or effective voltage value U) and pulse load DC side voltage UdcDue to the close correlation of the equivalent internal impedance of the diesel generator set.
Derivation of source-carried power coupling relation:
based on the instantaneous power theory, defining the instantaneous active power p at the AC sidePLAnd instantaneous virtual power qPLAs shown in equation (20), where the instantaneous virtual power corresponds to the conventional reactive power, it is proportional to the energy exchanged between the system phases, but does not contribute to the energy transfer between the source loads, and is denoted by the symbol "vai". By substituting formulae (12) and (16) for formula (20), it is possible to obtain:
Figure BDA0001873999010000141
can know udc＝(uaSa+ubSb+ucSc) For the DC side voltage, define u⊥dc＝(uabSc+ubcSa+ucaSb)。
The above formula shows that the instantaneous active power p at the AC sidePLIs a DC side voltage udcAnd a direct side current idcQ, and qPLIs u⊥dcAnd idcThe product of (a). Therefore, corresponding to the concept of instantaneous active and virtual work on the AC side, u is expresseddc＝(uaSa+ubSb+ucSc) And u⊥dc＝(uabSc+ubcSa+ucaSb) Which are respectively called "equivalent active voltage" and "equivalent virtual active voltage" on the dc side, and the theoretical waveforms thereof are shown in fig. 5.
As can be seen from fig. 5: u. ofdcIs the output voltage of the rectifier, which is mainly in the form of direct current with ripple having a frequency of 6f0And the fluctuation amplitude is small; and u⊥dcIs a frequency of 6f0The average value of the sawtooth wave voltage of (1) is 0, and the physical meaning thereof isMeaning the voltage that the rectifier uses for power exchange during operation.
It is noted that the actual instantaneous active power of the ① pulsed load produces p at resistor RRBut p isPL≠pRFrom the viewpoint of power conservation, there are
Figure BDA0001873999010000142
②qPLIs essentially a direct-current side inductance LdcCapacitor CesThe power exchanged during operation, which is not consumed, has
Figure BDA0001873999010000143
The equation (20) is the instantaneous power p on the AC side of PL-IPSPL、qPLAnd the coupling relation with the voltage and the current on the direct current side of the pulse load.
Analyzing the coupling relation of the source carrier frequency:
substituting the formula (20) into the motion equation of the rotor of the synchronous generator to obtain
Figure BDA0001873999010000151
Figure BDA0001873999010000152
Wherein, delta is the power angle of the generator, H is the moment of inertia, PmIs mechanical power, PDFor damping power, PeIs electromagnetic power, omega is actual angular frequency of the generator, omega0Rated angular frequency of the generator, f system frequency, f0The system nominal frequency.
The formula shows that the system frequency is correlated with the voltage and current of the direct current side of the pulse load, and the formula is a coupling relation formula of the PL-IPS system frequency and the voltage and current of the pulse load.
PL-IPS Source-borne decoupling model:
due to the non-linearity of the rectification type pulse load, the difficulty of theoretical analysis is greatly increased by considering source-load coupling. If the source-load coupling key parameters can be equivalent to the direct current side from the alternating current side, so that the power supply is equivalent to an ideal power supply, and the coupling relation between the power supply and the ideal power supply is removed, the details of the influence of the source-load coupling on the operation mechanism of the direct current side can be embodied when the theoretical analysis is carried out on the direct current side, and the difficulty of the theoretical analysis can be reduced.
The source-borne "decoupling" model of PL-IPS is derived mathematically, and equation (16) is written as follows
Figure BDA0001873999010000153
In the formula, ea、eb、ecIs an ideal voltage source, then Saea+Sbeb+ScecIs an ideal power supply voltage eabcEquivalent to the voltage on the DC side of the pulse load, let edc. This equation shows that the DC side voltage u under source-to-load couplingdcCan be divided into two parts, ① ideal power supply eabcGenerated DC side voltage edc② coupling voltage of power supply internal impedance (-2L)s(didc/dt)-2rsidc)。
Therefore, when the pulse load direct current side operation mechanism is researched, the internal impedance (the resistor r) of the power supply can be adjustedsAnd a reactance Ls) Equivalent to the dc side, and the power source can be regarded as an ideal voltage source from the load side. Thus, the PL-IPS source-borne coupling model of FIG. 4 can be equated to a source-borne "decoupling" model, as shown in FIG. 6.
In the figure, the impedance on the AC side is equivalent to the impedance on the DC side, and the equivalent resistance value is 2rsAn equivalent inductance of 2Ls；udcIs the output voltage of the DC side in the 'source load coupling' state, edcIs the output voltage of the DC side in the decoupling state, and the physical meaning is an ideal voltage source eabcThe equivalent voltage on the dc side.
Will switch function Sa、Sb、ScExpansion into Fourier series to obtain edcExpression (2)
Figure BDA0001873999010000161
Wherein ω is 2 π f0，f0For the frequency, f, of the power supply system (diesel-electric set) on the AC side0E is the ideal voltage source voltage peak value at 50Hz,
Figure BDA0001873999010000165
it can be seen that edcConsists of a direct current term and a multiple harmonic term of 6 (Mn, n is 1, 2, 3 …, M is 6), the amplitude of the cosine term gradually decreases with increasing number n, wherein
Figure BDA0001873999010000162
Thus, the 6 th harmonic term is its primary harmonic term. The value of M is determined by the number of state switching times in one cycle of the rectifier, and is referred to as a "6-pulse rectifier circuit" herein when M is 6. If a 12-pulse rectifier circuit is used, M is 12. Thus, edcCan be approximately expressed as
Figure BDA0001873999010000163
Calculated to obtain edcHas an average value and a maximum value of
Figure BDA0001873999010000164
The source-loaded decoupling model enables the coupling voltage to be equivalent to the load direct current side, and enables the source end to be equivalent to an ideal voltage source, so that the influence of the operation characteristic of the source end on the pulse load direct current side is not needed to be considered when the characteristic analysis of the pulse load direct current side is carried out, and the analysis difficulty is greatly reduced.
It should be noted that the model is derived from the equation (12) to the equation (22), and the derivation process of the equation (12) only considers the electromagnetic equation of the synchronous generator and does not consider the mechanical equation of the prime mover (the coupling relation of the mechanical rotating speed is derived as the equation (21), so that the model is only suitable for theoretical analysis of the PL-IPS source-borne coupling electrical characteristics, and the analysis of the rotating speed (system frequency) of the diesel generator set is reflected from the power side and is directly verified from actual tests.

Claims (1)

1. A source-borne decoupling model modeling method of an independent power system with a pulse load is characterized by comprising the following steps:
simplifying an equivalent model by using a synchronous generator, and constructing a coupling equivalent model of the synchronous generator and a pulse load;
the coupling equivalent model of the synchronous generator and the pulse load is constructed by the following method:
simplifying the synchronous generator, and constructing a rotor loop flux linkage equation of the synchronous generator as follows:
Figure FDA0002293244190000011
wherein the content of the first and second substances,
Figure FDA0002293244190000012
respectively a d-axis excitation winding flux linkage, a q-axis short-circuit winding current flux linkage, a d-axis damping winding flux linkage and a q-axis damping winding flux linkage; i.e. ifd、ifq、ikd、ikqD-axis excitation winding current, q-axis short-circuit winding current, d-axis damping winding current and q-axis damping winding current respectively; i.e. id、iqRespectively outputting d-axis current and q-axis current for the unit;
Figure FDA0002293244190000013
Figure FDA0002293244190000014
and
Figure FDA0002293244190000015
are respectively ifd、ifq、idAnd iqThe non-periodic component of (a); x is the number offds、xfqs、xkds、xkqsLeakage reactance of a d-axis excitation winding, a q-axis short-circuit winding, a d-axis damping winding and a q-axis damping winding are respectively arranged; x is the number ofadD-axis armature reaction synchronous reactance is the mutual reactance of three windings of the d axis; x is the number ofaqThe q-axis armature reaction synchronous reactance is the mutual reactance of the three windings of the q axis;
obtaining i from equation (1)fd、ikd、ifqAnd ikqAnd then, substituting the Park flux linkage equation to obtain the d and q axis flux linkage formula as follows:
Figure FDA0002293244190000016
wherein the content of the first and second substances,
Figure FDA0002293244190000017
is a magnetic linkage of the d-axis,
Figure FDA0002293244190000018
is a q-axis flux linkage, xd、xqAre respectively d-axis and q-axis winding self-inductance, x "d、x”qD-axis and q-axis super-transient equivalent reactances respectively;
the current equation between the phases c and a is as follows:
Figure FDA0002293244190000019
wherein idcThe rotor angle is theta, namely theta is the rotor angle, namely omega t;
substituting the formula (2) and the formula (3) into a voltage equation of the motor, the d-axis voltage and the q-axis voltage can be obtained as follows:
Figure FDA0002293244190000021
wherein u isdFor d-axis voltage, u, of a synchronous generatorqIs the q-axis voltage of the synchronous generator, and r is the armature resistance of the synchronous generator;
let x "d＝x”qThen, a simplified equivalent model of the synchronous generator is obtained as follows:
Figure FDA0002293244190000022
wherein u isa、ub、ucA phase voltage a, b phase voltage c and a phase voltage x respectively output by the AC side of the synchronous generatortFor commutation reactance, xt＝(x”d+x”q) 2; r is the armature resistance; e1The amplitude of the electromotive force of the synchronous generator is delta, and the initial phase angle of the synchronous generator is delta;
Figure FDA0002293244190000023
Figure FDA0002293244190000024
x'd、x'qd-axis and q-axis transient reactances respectively;
the pulse load rectifier in the independent power system adopts a three-phase bridge type full-control rectification structure, the conduction sequence of 6 thyristors is VT1 → VT2 → VT3 → VT4 → VT5 → VT6, a trigger angle α is set to be 0 degrees, the state switching frequency M in a cycle is set to be 6, and switching functions S of three bridge arms of abc are introduceda、Sb、Sc：
Figure FDA0002293244190000025
The power supply outputs an AC side voltage ua、ub、ucAnd the DC side voltage u of the pulse loaddcIs in the coupling relation of
udc＝Saua+Sbub+Scuc(7)
Substituting the formulas (5) and (6) into the formula (7) to obtain a DC side voltage udc
Figure FDA0002293244190000031
rs＝r，Ls＝xt；
Let the DC side current of the pulse load be idcThen the power supply outputs three-phase current i on the AC sidea、ib、icAnd the pulse load direct side current idcIs in the coupling relation of
ix＝Sxidc(x＝a,b,c) (9)
The formula (8) and the formula (9) are source load coupling equivalent models of the synchronous generator and the pulse load voltage and current;
deriving a source load coupling relation of alternating current and direct current side voltage and current of a coupling equivalent circuit model of the synchronous generator and the pulse load by introducing three bridge arm switching functions of the rectifier;
the synchronous generator is simplified by the following method:
1) ignoring non-periodic components of damping winding current
Figure FDA0002293244190000032
And
Figure FDA0002293244190000033
2) neglecting the influence of the rotor loop on the alternating current;
the source-carried decoupling model is constructed by equating the internal impedance of the alternating current side to the direct current side to make the power supply equivalent to an ideal voltage source,
the equivalent voltage of an ideal voltage source on the direct current side is obtained by the following method:
substituting formula (9) into formula (8), and obtaining direct-current side voltage u through mathematical derivationdc
Figure FDA0002293244190000034
rs＝r，Ls＝xt；
Calculate to know Sa 2+Sb 2+Sc 22, and
Figure FDA0002293244190000035
to obtain
Figure FDA0002293244190000041
It can be known that Saea+Sbeb+ScecThe equivalent voltage of an ideal voltage source on the direct current side of the pulse load;
the formula of the source-borne decoupling model is as follows:
Figure FDA0002293244190000042
in the formula, ea、eb、ecIs an ideal voltage source, then Saea+Sbeb+ScecIs an ideal power supply voltage eabcEquivalent to the voltage on the DC side of the pulse load, let it be edc；(-2Ls(didc/dt)-2rsidc) Is the coupling voltage of the impedance in the power supply of the synchronous generator.
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