CN113328446A - Method and system for improving operation stability of new energy synchronous motor pair - Google Patents

Method and system for improving operation stability of new energy synchronous motor pair Download PDF

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CN113328446A
CN113328446A CN202010128409.7A CN202010128409A CN113328446A CN 113328446 A CN113328446 A CN 113328446A CN 202010128409 A CN202010128409 A CN 202010128409A CN 113328446 A CN113328446 A CN 113328446A
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synchronous motor
new energy
excitation
synchronous
energy source
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CN113328446B (en
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陈巨龙
赵海森
张裕
刘振铭
孙斌
薛毅
李庆生
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Guizhou Power Grid Co Ltd
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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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • 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
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
    • H02P9/105—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for increasing the stability
    • 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
    • H02P2103/00—Controlling arrangements characterised by the type of generator
    • H02P2103/20—Controlling arrangements characterised by the type of generator of the synchronous type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

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Abstract

The invention provides a method and a system for improving the running stability of a new energy source synchronous motor pair through excitation control, and the method relates to that two independent direct current excitation power supplies are respectively used as excitation devices of a synchronous motor SM and a synchronous generator SG in the synchronous motor pair, and the excitation voltages U of the two excitation power supplies are respectively adjustedfM、UfGThe system comprises a photovoltaic simulator, a synchronous motor pair and a power grid simulator, wherein the synchronous motor pair comprises a photovoltaic simulator, a synchronous motor pair and a power grid simulator, and the synchronous motor pairThe method and the system can effectively reduce the damage of oscillation to a common rotating shaft of the two synchronous motors and improve the operation stability of the new energy synchronous motors to the system.

Description

Method and system for improving operation stability of new energy synchronous motor pair
Technical Field
The invention relates to the technical field of operation and stability of a new energy power system, in particular to a method and a system for improving the operation stability of a new energy synchronous motor through excitation control.
Background
Currently, wind power generation and photovoltaic power generation have kept a strong development trend in recent years as the most mature and promising renewable energy sources at present. In 2017, the wind power installation reaches 1.54 hundred million kilowatts and the photovoltaic power generation installation reaches 1.02 hundred million kilowatts in China, and the total proportion of the wind power installation and the photovoltaic power generation installation accounts for more than 13 percent [1 ]. It is expected that the new energy ratio of some local power grids can reach 80% or even higher in the near future, and the ultrahigh-ratio new energy grid-connected operation becomes an important characteristic of the future power grid structure.
Abundant wind energy and solar energy resources in China are mainly located in the three north region, new energy power generation is mostly located at the tail end of a power grid, the power supply structure is single, the grid structure of the power grid is weak, and the adjusting capacity is limited; in addition, the output of the new energy generator set has obvious intermittence and fluctuation, and the influence on the safety and the stability of the power grid is different from that of the conventional synchronous generator set. With the enlargement of the scale of new energy stations such as wind power plants, photovoltaic power stations and the like, the proportion of new energy in a power grid is higher and higher, and the influence range of the new energy on the power grid is gradually enlarged from part.
However, most of the existing new energy sources are connected to the grid by using power electronic inverters, compared with the traditional generator connected to the grid, the new energy sources are limited in voltage resistance, do not have a frequency regulation function, and cannot well provide stability for a new energy source grid, and in order to solve the problems, two patents with patent numbers of CN 105244911 and CN 105958543 propose a novel grid connection mode, the new energy sources are not directly connected to the grid by using inverters, but a synchronous motor pair is added between the inverters and the grid, that is, the new energy sources are connected to the grid in the form of inverters, synchronous motors and synchronous generators. In this way, some excellent characteristics of the synchronous motor, such as inertia response, over-current capability, synchronous oscillation suppression capability and the like, can be better used for improving the stability of the new energy power grid.
However, experimental studies show that when a disturbance occurs on the grid side, such as an instantaneous drop of the grid frequency, a sudden increase or decrease of the voltage, and a power change on the load side, the new energy synchronous motor oscillates the system in a short time, and although the oscillation time is short, if the oscillation amplitude is too large, the new energy synchronous motor will bring a large impact to each element of the new energy synchronous motor pair, so that the stable operation of the grid cannot be well maintained.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
Therefore, the technical problem to be solved by the present invention is to overcome the defect of unstable oscillation of the new energy source synchronous motor pair under disturbance condition in the prior art, so as to provide a method and a system for improving the operation stability of the new energy source synchronous motor pair through excitation control.
In order to solve the technical problems, the invention provides the following technical scheme: a method and a system for improving the running stability of a new energy source synchronous motor through excitation control are characterized by comprising the following steps:
two independent direct-current excitation power supplies are respectively used as excitation devices of a synchronous motor SM and a synchronous generator SG in a synchronous motor pair;
in the actual grid-connected operation process, the excitation of two excitation power supplies is respectively adjustedVoltage UfM、UfGThereby improving the overall damping of the new energy synchronous motor pair;
when the excitation voltage of the new energy source synchronous motor to the system changes, the excitation flux linkage changes, so that the damping torque component of the new energy source synchronous motor pair is influenced, and the effect of improving the overall damping of the new energy source synchronous motor can be achieved by reasonably adjusting the excitation voltage of the excitation power supply.
As a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: the photovoltaic simulator, the frequency converter, the synchronous motor SM, the synchronous generator SG and the power grid simulator are sequentially connected in series, and two independent direct-current excitation power supplies are respectively connected to the synchronous motor SM and the synchronous generator SG to form a new energy synchronous motor grid-connected experimental system.
As a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: the equation of motion of the synchronous motor SM and the synchronous generator SG can be described as follows:
Figure BDA0002395122620000021
Figure BDA0002395122620000022
in the formula: p-represents a differential operator; Δ — the sign of the change; omegaM、ωG-rotor angular speed of synchronous motor, synchronous generator; omega0-rotor angular velocity rating; h is the inertia time constant;
TeM、TeG-electromagnetic torque of synchronous motors, synchronous generators;
TmM、TmG-synchronous motor, synchronous generator mechanical torque;
KDM、KDGdamping coefficient of synchronous motor and synchronous generator.
As a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: the two motors are coaxially connected, the mechanical torques of the two synchronous machines are equal, and the angular speeds of the rotors are the same, i.e. T can be assumedmM＝TmGTm and ωM＝ωG＝ωrTherefore, by superposing the motion equations in the formula (1) and the formula (2), a motion equation describing the new energy source synchronous motor to the system can be obtained:
Figure BDA0002395122620000031
as a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: the synchronous motor SM and the synchronous generator SG adopt two independent excitation devices, so that respective excitation voltage U can be respectively adjustedfM、UfGThe damping of the synchronous motor and the damping of the synchronous generator can be respectively changed, and the two excitation power supplies are coordinated and matched through the experimental method, so that the damping coefficient K of the synchronous motor to the system in the equation (3) can be realizedDMAnd KDGAnd meanwhile, the overall damping of the new energy source synchronous motor pair is improved, and the new energy source synchronous motor pair can inhibit oscillation in a relatively large way by depending on the excitation action of the new energy source synchronous motor pair after frequency disturbance occurs in the system.
As a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: disturbance is set at the side of a power grid simulator to simulate the fluctuation of the power grid frequency, then the oscillation amplitude A and the steady-state recovery time t of the new energy synchronous motor are observed, and the excitation voltages U of two excitation power supplies are adjusted according to the magnitudes of A and tfM、UfGUntil the oscillation amplitude a and the steady-state recovery time t reach an optimum value.
As a preferable scheme of the method for improving the operation stability of the new energy source synchronous motor through excitation control according to the present invention, wherein: the method for improving the operation stability of the new energy source synchronous motor pair through excitation control is based on a new energy source synchronous motor pair system.
The invention also provides a new energy synchronous motor pair system, wherein: the synchronous motor pair is respectively connected with the photovoltaic simulator and the power grid simulator, the power grid simulator is connected to the wave recorder, and the wave recorder records and receives data and feeds back the data.
The invention has the beneficial effects that:
the invention provides a method for improving the running stability of a new energy source synchronous motor pair through excitation control, wherein in the running process of the new energy source synchronous motor pair, when frequency disturbance occurs, an excitation power supply can improve the overall damping of a system and inhibit the oscillation of the synchronous motor, so that the stability of the new energy source synchronous motor pair during grid-connected running is improved, in addition, the excitation power supply can also provide reactive power support for the synchronous motor, so that the terminal voltage is stabilized, and the method for improving the stability of the new energy source synchronous motor pair through adjusting the excitation voltage provides important technical support for the system of the new energy source synchronous motor on actual power grid engineering landing and practice.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:
fig. 1 is an experimental schematic diagram for improving the operation stability of a new energy synchronous motor according to the invention;
FIG. 2 shows ufAnd ΨLA relation to total excitation current;
FIG. 3 is a schematic diagram of the torque component due to K2 Δ ψ fd in the present invention;
FIG. 4 is a circuit diagram of a DC excitation power supply;
FIG. 5 is a schematic diagram of a synchronous motor pair grid-connected operation flow in the present invention;
FIG. 6 is a graph showing the variation of the motor speed of the load of 100W-500W according to the embodiment of the present invention;
FIG. 7 is a graph of the frequency change of a motor with a load of 100W-500W according to an embodiment of the present invention;
FIG. 8 is a graph showing the variation of the rotational speed of a motor having a frequency of 50Hz to 49.96Hz in accordance with an embodiment of the present invention;
FIG. 9 is a graph of the frequency variation of a motor having a frequency of 50Hz to 49.96Hz in accordance with an embodiment of the present invention;
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
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.
The embodiment provides a method for improving the operation stability of a new energy source synchronous motor pair through excitation control, and the method is based on the synchronous machine theory and the action of an excitation system and adopts a mode of controlling excitation voltage to improve the overall damping of the new energy source synchronous motor pair, so that the operation stability of the new energy source synchronous motor pair is improved. When the new energy synchronous motor pair is disturbed, the excitation system can play a role in regulation, the magnitude of the excitation voltage can influence the damping of the new energy synchronous motor, and reactive support is provided for the power grid side in the operation process. And the new energy synchronous motor pair adopts two independent excitation power supplies which are coordinated and matched, and the damping level of the new energy synchronous motor to the system can be improved to the maximum extent by reasonably configuring the excitation voltages of the two excitation power supplies through experiments, so that the running stability of the new energy synchronous motor to the system is improved.
One obvious characteristic of the new energy synchronous motor is that an excitation power supply bears main control functions such as voltage and damping on a power grid side in the grid-connected operation process. The damping of the synchronous motor mainly comes from mechanical damping and electrical damping, wherein the mechanical damping refers to mechanical friction when the rotor rotates, and the electrical damping refers to electromagnetic torque generated by relative motion of magnetic fields of the stator and the rotor. Electrical damping is related to magnetic flux variations and therefore there are three main sources: damping winding, armature reaction and excitation control. The electrical damping provided actively by excitation control is of major concern in stability analysis, since the damping effect of mechanical damping, damping windings and armature reaction is relatively weak and often uncontrolled.
Further, according to the working principle of the excitation power supply, a circuit diagram of a direct-current excitation power supply with separately excited and self-shunt excitation windings is assumed to be shown in fig. 1, wherein Ry is the resistance of the separately excited winding, and R isRBeing self shunt winding resistance, RCIs an excitation regulating resistor, Rg is an additional resistor of an excitation loop, N1And L1For separately excited winding turns and inductance, N2And L2For self shunt winding turns and inductance, L1And L2Taking into account the saturation non-linearity, iyFor separately excited current iBFor self-excitation current, iFLFor compound excitation current uLfIs a separately excited voltage ufIs the excitation power supply output voltage, i.e. the excitation voltage of the generator. Wherein the separately excited voltage uLfAnd compound excitation current iFLAs an input amount, ufIs the output quantity. Suppose separately excited winding L1And a self-excited winding L2Are equal in flux linkage, i.e. ΨL1＝ΨL2Thus, there is a loop equation:
Figure BDA0002395122620000051
Figure BDA0002395122620000052
due to N1＝N2Excitation of the excitation power supply can be directly performedThe currents are superimposed to obtain the total excitation current, iL fΣ＝iy+iB+iFLAnd is provided with ufThe total exciting current of the corresponding exciting power supply is i on the air gap lineL fΣ0On the idle line is iL fΣ(see FIG. 2 a). Excitation winding flux linkage psi with same excitation power supplyLThe total exciting current of the corresponding exciting power supply is i on the air gap lineL fΣ0On the idle line is iL fΣ(see FIG. 2 b). Then defined by β and L:
Figure BDA0002395122620000061
therefore, the basic relation between the electromagnetic quantity of the excitation power supply is formed, and when the excitation voltage changes, the excitation flux linkage can be changed. When the reactive current is increased due to disturbance on the power grid side, the excitation system can maintain the voltage at the generator end unchanged by adjusting the excitation voltage, so that the stability of the new energy synchronous motor to grid-connected operation is improved, the excitation system can provide positive damping for the generator, the oscillation amplitude of the generator is reduced when the disturbance occurs, and the grid-connected stability of the new energy synchronous motor pair can be improved to a certain extent.
Further, in order to understand the damping characteristics of the new energy source synchronous motor pair, the principle of damping generation needs to be understood first. The synchronous machine air gap electromagnetic torque equation is generally expressed in the form:
ΔTe＝K1Δδ+K2Δψfd (7)
in the formula: Δ Te — amount of change in air gap torque; delta-the amount of change in power angle; delta psifd-the amount of change in excitation flux linkage; k1、K2Coefficients relating to motor parameters and initial conditions etc.
In the formula (7), represented by1Δ δ gives the torque component in phase with Δ δ, so it represents a synchronous torque component; and is formed by K2ΔψfdThe given torque component being due to a change in excitation flux linkage, K2ΔψfdThe component in phase with Δ ω r is the damping torque component, see fig. 3.
The combination formulas (6) and (7) can obtain that the magnitude of the excitation voltage is changed, the excitation flux linkage can be changed, and the damping torque component is changed.
Analyzing the damping characteristic of the new energy synchronous motor to the system, and describing the motion equation of the synchronous motor SM and the synchronous generator SG as follows:
Figure BDA0002395122620000062
Figure BDA0002395122620000063
in the formula: p-represents a differential operator; Δ — the sign of the change;
ωM、ωG-rotor angular speed of synchronous motor, synchronous generator;
ω0-rotor angular velocity rating; h is the inertia time constant;
TeM、TeG-electromagnetic torque of synchronous motors, synchronous generators;
TmM、TmG-synchronous motor, synchronous generator mechanical torque;
KDM、KDG-damping coefficients of synchronous motors, synchronous generators;
because the two motors are coaxially connected, the mechanical torques of the two synchronous machines are equal, and the angular speeds of the rotors are the same, i.e. T can be assumedmM＝TmG＝TmAnd ωM＝ωG＝ωr(ii) a Therefore, by superposing the motion equations in the formula (8) and the formula (9), a motion equation describing the new energy source synchronous motor pair system can be obtained:
Figure BDA0002395122620000071
the synchronous motor SM and the synchronous generator SG adopt two independent excitation devices, so that respective excitation voltage U can be respectively adjustedfM、UfGThe damping values of the synchronous motor and the synchronous generator can be respectively changed, and the damping coefficient K of the synchronous motor to the system in the equation (10) can be realized by coordinating the two excitation power suppliesDMAnd KDGAnd meanwhile, the overall damping of the new energy source synchronous motor pair is improved, so that the new energy source synchronous motor pair can inhibit oscillation in a relatively large way by depending on the excitation action of the new energy source synchronous motor pair after the frequency disturbance of the system occurs, and the stability of the new energy source synchronous motor to grid-connected operation is improved.
The method for adjusting the excitation voltage is applied to a new energy synchronous motor pair system, as shown in figure 4, the system comprises a photovoltaic simulator 1 and a starting switch K1The device comprises a frequency converter 2, a synchronous motor pair 3, a motor excitation power supply 4, a generator excitation power supply 5, a power grid simulator 6, a programmable load 7, a PLC control board 8 and a wave recorder 9, wherein the synchronous motor pair 3 is formed by coaxially connecting rotors of a synchronous motor 301 and a synchronous generator 302. The synchronous motor grid-connection starting process refers to the attached figure 5.
The specific implementation mode is respectively carried out under two working conditions:
1. operating mode with load
Under the condition of load, when the load suddenly changes, the influence of different excitation voltages on the grid-connected stability of the new energy synchronous motor is observed. The implementation steps are as follows:
1) and starting the photovoltaic simulator 1, inputting the set photovoltaic characteristic curve into the photovoltaic simulator 1, and operating the photovoltaic simulator 1 at the rightmost endpoint of the P-V curve at the moment. After the output current is stable, the direct current side of the frequency converter 2 is charged, and the frequency converter 2 is started. The photovoltaic simulator 1 operates in a stable region, and the operating voltage is about 556V.
2) And (3) turning on a motor excitation power supply 4 and a generator excitation power supply 5, adjusting the excitation voltage to 16V, and exciting the synchronous motor pair 3. Subsequently, the inverter 2 is started to drive the synchronous motor 301, and the synchronous motor 301 is dragged to the vicinity of the synchronous speed.
3) The programmable load 7 is started, the load initial value is set to 100W, and then output is performed.
4) After the motor rotates stably at the synchronous speed, the connecting switch K is closed3And the output side of the new energy synchronous motor pair is connected with a programmable load 7.
5) After the new energy source synchronous motor operates stably with the load for about 10s, the load power is increased to 500W, the change condition of the new energy source synchronous motor to the system rotating speed in the whole process is observed, and a oscillograph of the rotating speed is recorded by a oscillograph 9.
Then adjusting the exciting voltage of the two exciting power supplies respectively, and repeating the steps 1-5. The excitation voltage is increased to 36V all the time by taking 4V as a unit, and the experimental results of the rotor speed and the generator frequency change under 6 groups of different excitation voltages are obtained in total, as shown in fig. 6 and 7.
According to the implementation results, under different excitation voltages, the oscillation condition and the stable recovery time of the new energy source synchronous motor to the rotor rotating speed are different. When the excitation voltage of the two excitation power supplies is 24V, the new energy synchronous motor has the minimum oscillation amplitude, the oscillation amplitude is about 1473r/min, and the stable recovery time point is 12.41 s; when the excitation voltage is greater than 24V, the oscillation amplitude is increased along with the increase of the excitation voltage, and when the excitation voltage is increased to 36V, the oscillation amplitude reaches 1470 r/min; when the excitation voltage is less than 24V, the oscillation amplitude still increases along with the reduction of the excitation voltage, and when the excitation voltage is reduced to 16V, the oscillation amplitude is 1466 r/min. Therefore, in the implementation of the load scheme, the adjustment of the magnitude of the excitation voltage is beneficial to improving the oscillation condition of the new energy synchronous motor to the rotor and shortening the stable recovery time. Under the working condition that the load change is 100W-500W, when the excitation voltages of the two excitation power supplies are both about 24V, the new energy source synchronous motor pair is more stable in the operation process.
2. Grid-connected operation condition
Under the grid-connected operation condition of the new energy synchronous motor, the frequency of the grid side is changed, and the influence of different excitation voltages on the grid-connected stability of the new energy synchronous motor is observed. The specific implementation steps are as follows:
1) the photovoltaic simulator 1 is started, the set photovoltaic characteristic curve is input into the photovoltaic simulator 1, the photovoltaic simulator 1 operates in a stable area, and the operating voltage is about 556V.
2) The motor excitation power supply 4 and the generator excitation power supply 5 are turned on, and the excitation voltage is adjusted to 20 to apply excitation to the pair of synchronous machines 3. Subsequently, the inverter 2 is started to drive the synchronous motor 301, and the synchronous motor 301 is dragged to the vicinity of the synchronous speed.
3) The grid simulator 6 is started, the initial operation state is set to be 220V, 50Hz three-phase alternating current, and then the voltage is output.
4) After the motor rotates stably at the synchronous speed, the connecting switch K is closed2And the new energy synchronous motor pair completes grid-connected operation.
5) After the new energy synchronous motor is stable to grid-connected operation, when the frequency of the new energy synchronous motor is changed by about 10s through the control panel of the power grid simulator 6, the frequency of the new energy synchronous motor is reduced from the initial 50Hz to 49.96Hz, the change condition of the new energy synchronous motor to the system rotating speed in the whole process is observed, and a oscillograph of the rotating speed is recorded by the oscillograph 9.
And then adjusting the excitation voltage of the two excitation power supplies respectively, and repeating the steps. The excitation voltage was increased up to 36 in units of 4V to obtain 5 different excitation conditions, as shown in fig. 8 and 9.
According to the implementation result, when the excitation voltage is 24V, the fluctuation of the rotating speed and the frequency is minimum, and the oscillation amplitude is 1464 r/min; when the excitation voltage of the two excitation power supplies is more than 24V, the rotating speed and the frequency change amplitude value are increased along with the increase of the excitation voltage; when the excitation voltage is less than 24V, the rotation speed variation amplitude increases with a decrease in the excitation voltage. Therefore, under the grid-connected condition, when the grid-side frequency changes, the oscillation condition of the new energy synchronous motor to the system rotor can be improved by respectively adjusting the excitation voltages of the two excitation power supplies, and in the embodiment, the optimal excitation voltage of the two excitation power supplies is 24V.
It is important to note that the construction and arrangement of the present application as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in this application. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of this invention. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present inventions. Therefore, the present invention is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims.
Moreover, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not be described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the invention).
It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (9)

1. A method for improving the running stability of a new energy source synchronous motor is characterized by comprising the following steps:
two independent direct-current excitation power supplies are respectively used as excitation devices of a synchronous motor SM and a synchronous generator SG in a synchronous motor pair;
in the actual grid-connected operation process, the excitation voltages U of the two excitation power supplies are respectively adjustedfM、UfGThereby improving the overall damping of the new energy synchronous motor pair;
when the excitation voltage of the new energy source synchronous motor to the system changes, the excitation flux linkage changes, so that the damping torque component of the new energy source synchronous motor pair is influenced, and the effect of improving the overall damping of the new energy source synchronous motor can be achieved by reasonably adjusting the excitation voltage of the excitation power supply.
2. The method for improving the running stability of the new energy source synchronous motor pair according to claim 1, characterized in that: the photovoltaic simulator, the frequency converter, the synchronous motor SM, the synchronous generator SG and the power grid simulator are sequentially connected in series, and two independent direct-current excitation power supplies are respectively connected to the synchronous motor SM and the synchronous generator SG to form a new energy synchronous motor grid-connected experimental system.
3. The method for improving the operation stability of the new energy source synchronous motor pair according to claim 2, characterized in that: the equation of motion of the synchronous motor SM and the synchronous generator SG can be described as follows:
Figure FDA0002395122610000011
Figure FDA0002395122610000012
in the formula: p-represents a differential operator; Δ — the sign of the change; omegaM、ωG-rotor angular speed of synchronous motor, synchronous generator; omega0-rotor angular velocity rating; h is the inertia time constant;
TeM、TeG-electromagnetic torque of synchronous motors, synchronous generators;
TmM、TmG-synchronous motor, synchronous generator mechanical torque;
KDM、KDG-damping coefficients of synchronous motors, synchronous generators.
4. The method for improving the operation stability of the new energy source synchronous motor pair according to claim 3, wherein the method comprises the following steps: because the two motors are coaxially connected, the mechanical torques of the two synchronous machines are equal, and the angular speeds of the rotors are the same, i.e. T can be assumedmM＝TmGTm and ωM＝ωG＝ωrTherefore, by superposing the motion equations in the formula (1) and the formula (2), a motion equation describing the new energy source synchronous motor to the system can be obtained:
Figure FDA0002395122610000021
5. the method for improving the running stability of the new energy source synchronous motor pair according to claim 1, characterized in that: starting the photovoltaic simulator to supply power to the frequency converter, starting two excitation power supplies, and respectively providing excitation voltage U for the synchronous motor SM and the synchronous generator SGfM、UfGAnd the frequency converter is started to drive the new energy synchronous motor to rotate to a synchronous speed, and then the new energy synchronous motor is merged into the power grid simulator.
6. The method for improving the operation stability of the new energy source synchronous motor pair according to any one of claims 3 to 5, wherein the method comprises the following steps: the synchronous motor SM and the synchronous generator SG adopt two independent excitation devices, so that respective excitation voltage U can be respectively adjustedfM、UfGThe damping of the synchronous motor and the damping of the synchronous generator can be respectively changed, and the two excitation power supplies are coordinated and matched through the experimental method, so that the damping coefficient K of the synchronous motor to the system in the equation (3) can be realizedDMAnd KDGAnd meanwhile, the overall damping of the new energy source synchronous motor pair is improved, and the new energy source synchronous motor pair can inhibit oscillation in a relatively large way by depending on the excitation action of the new energy source synchronous motor pair after frequency disturbance occurs in the system.
7. The method for improving the running stability of the new energy source synchronous motor pair according to claim 1, characterized in that: disturbance is set at the side of a power grid simulator to simulate the fluctuation of the power grid frequency, then the oscillation amplitude A and the steady-state recovery time t of the new energy synchronous motor are observed, and the excitation voltages U of two excitation power supplies are adjusted according to the magnitudes of A and tfM、UfGUntil the oscillation amplitude a and the steady-state recovery time t reach an optimum value.
8. The method and the system for improving the operation stability of the new energy source synchronous motor pair according to claim 7 are characterized in that: the method for improving the operation stability of the new energy source synchronous motor pair through excitation control is based on a new energy source synchronous motor pair system.
9. The utility model provides a new forms of energy synchronous machine is to system which characterized in that: including photovoltaic simulator (1), synchronous machine to (3) and electric wire netting simulator (6), synchronous machine connects photovoltaic simulator (1) and electric wire netting simulator (6) respectively to (3), just electric wire netting simulator (6) are connected to oscillograph (9) to receive data and feedback by oscillograph (9) record.
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