CN110311382B - Idle speed point setting method for improving idle speed grid-connection success rate of synchronous phase modulator - Google Patents

Idle speed point setting method for improving idle speed grid-connection success rate of synchronous phase modulator Download PDF

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CN110311382B
CN110311382B CN201910633489.9A CN201910633489A CN110311382B CN 110311382 B CN110311382 B CN 110311382B CN 201910633489 A CN201910633489 A CN 201910633489A CN 110311382 B CN110311382 B CN 110311382B
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point
grid
idle speed
phase modulator
condition
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CN110311382A (en
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孙毅超
曹泽宇
丁楠木
王�琦
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YANGZHOU JIANGDU DISTRICT POWER SUPPLY BRANCH OF STATE GRID JIANGSU ELECTRIC POWER Co.,Ltd.
YANGZHOU YONGMAO ELECTRIC POWER CONSTRUCTION Co.,Ltd.
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Nanjing Normal University
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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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1885—Arrangements for adjusting, eliminating or compensating reactive power in networks using rotating means, e.g. synchronous generators
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

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Abstract

The invention discloses a method for setting an idle speed point for improving the idle speed grid-connection success rate of a synchronous phase modulator, which comprises the following steps: at the initial stage of phase modulator starting, dragging the phase modulator to start through an SFC static frequency conversion system under the coordination of a starting excitation loop, measuring the phase angle difference between the phase modulator and a power grid side when the rotor rotates at a speed 1.05 times of a rated speed, judging whether grid connection can be realized through a phase difference measured value, if grid connection cannot be realized, continuing to increase the rotating speed to the next idling point, measuring the phase difference again to judge whether grid connection can be realized, and repeating the process until the grid connection can be successfully realized; and then, an SFC static frequency conversion system is switched on, the phase modulator enters an idle speed state, and meanwhile, the excitation system is switched to a main excitation loop and is merged into a power grid through a quasi-synchronization device. The invention greatly improves the grid-connection success rate under the phase modulator idling grid-connection mode and reduces the resource waste caused by the restart due to grid-connection failure.

Description

Idle speed point setting method for improving idle speed grid-connection success rate of synchronous phase modulator
Technical Field
The invention relates to the field of power electronics, in particular to an idle speed point setting method for improving the idle speed grid-connected success rate of a synchronous phase modulator.
Background
In recent years, with the development of high-voltage direct-current transmission, China has built an alternating-current and direct-current hybrid power grid with the highest world voltage level and the largest scale, and by virtue of the characteristics of long transmission distance and large capacity, the alternating-current and direct-current hybrid power grid becomes an important way for energy allocation in China at present. Meanwhile, the problem of the 'strong direct weak direct current' of the power grid is more and more prominent, and the problems are specifically represented as excessive reactive power in a power supply concentration area, insufficient reactive power in a load concentration area and increasingly prominent voltage stability.
The phase modulator is used as traditional large-scale reactive compensation equipment, not only can provide reactive support for a power grid, but also can provide voltage support for the power grid through forced excitation; secondly, the phase modulator has strong overload capacity, and can still output a large amount of reactive power in the low-voltage process; the reactive compensation characteristic range of the final phase modulator is wide, and the reactive compensation device can not only emit reactive power in the phase-lag operation, but also absorb the reactive power in the phase-advance operation. In a receiving-end power grid with multiple direct-current feed-ins, a synchronous phase modulator usually plays roles in multiple aspects such as improving the direct-current multiple-feed-in short-circuit ratio, reducing the failure probability of multiple-circuit direct-current commutation, improving the system voltage stability level under serious faults and the like.
At present, 300Mvar phase modulators constructed in China mostly adopt an idle speed grid-connection mode, namely, after the synchronous phase modulators are started, rotors of the synchronous phase modulators are accelerated to about 1.05 times of rated rotating speed through a frequency conversion system, the frequency difference between the actual power grid frequency and the rated power grid frequency and the phase angle difference between the voltage of the synchronous phase modulators and the voltage of a power grid side are measured, and if the preset grid-connection condition is met, the control of the frequency conversion system on the synchronous phase modulators is cut off, and grid-connection operation is carried out. However, the rotation speed is uncontrollable and irreversible in the mode, so that once grid connection fails, the phase modulator can be started only after being stopped, and resource waste is caused. Neglecting the terminal voltage factor which can be regulated by excitation, the grid connection process mainly faces the contradiction between the frequency difference and phase angle difference conditions and the grid connection impact: the grid-connected frequency difference and the phase angle difference are set too large, the occurrence probability of a synchronous grid-connected point is high, but grid-connected impact is large; and the grid-connected frequency difference and the phase angle difference are set to be too small, so that grid-connected impact is small but the occurrence probability of synchronous grid-connected points is low. Therefore, how to improve the grid-connected success rate under the harsh grid-connected condition and avoid resource waste caused by repeated restarting is a key problem of the application economy of the novel synchronous phase modulator. Meanwhile, the prior art also has no method for judging whether the grid connection is successful after meeting the grid connection condition.
The patent with publication number CN109066803A proposes a method for improving synchronization grid-connection success rate of a large synchronous phase modulator, which is premised on that a grid-connection point exists during the idle speed period, thereby eliminating the grid-connection failure problem caused by the lead time error of a synchronization device, wherein the frequency difference of the grid-connection condition selected by the example in the patent is 0.8Hz, and in the actual situation, when the frequency difference of the grid-connection condition is less than 0.5Hz, the probability that the grid-connection point does not exist is greatly reduced, and the patent method cannot be implemented. The patent publication 106849180a proposes a large phase modulator startup grid-connected control method, which needs to perform many times of inertial velocity experimental measurements on a phase modulator, thereby possibly causing resource waste. In the patents with publication numbers CN107453404A and CN107910904A, optimization and improvement are made on a camera grid-connected system or grid-connected time sequence, but the problem of grid-connected success rate is not considered. In the patent publication CN109038684A, the selection of the grid-connection requirement frequency difference is from the maximum frequency difference under all conditions, and this selection would result in an excessively large frequency difference, and neglect the influence of the frequency difference on the grid-connection impact.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects of the prior art, the invention aims to provide a method for judging whether a synchronous phase modulator is lazy in synchronization success and a lazy point setting method for improving the lazy in synchronization success rate of the synchronous phase modulator.
The technical scheme is as follows: the method for judging whether the synchronous phase modulator is in the idle speed grid connection success state comprises the following steps:
(S1) measuring the phase angle difference between the voltage of the synchronous phase modulator at the lazy-speed point and the voltage on the power grid side
Figure GDA0002525428480000021
(S2) phase angle difference based on measurement
Figure GDA0002525428480000022
Frequency difference upper limit delta f required by grid connection*Upper limit of phase angle difference
Figure GDA0002525428480000023
Judging whether the synchronization phase modulator is successfully connected to the grid at the idle speed point or not; the judging process comprises the following steps:
when Δ f*When the condition a is satisfied, if
Figure GDA0002525428480000024
If the condition b is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
when Δ f*When the condition c is satisfied, if
Figure GDA0002525428480000025
If the condition d is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
condition a:
Figure GDA0002525428480000026
condition b:
Figure GDA0002525428480000027
condition c:
Figure GDA0002525428480000031
condition d:
Figure GDA0002525428480000032
in the formula, ωcFor synchronizing the rotor angular velocity, omega, of phase-modifiers at the idle speed point0The angular speed corresponding to the power grid frequency, d omega/dt is the angular speed slip during the phase modulator idling,
Figure GDA0002525428480000033
mod represents the phase angle difference measurement from the grid side for each time the lazy point is reached, with a period of 360 being the remainder.
Further, when ω iscWhen the following conditions are satisfied, ω among the conditions a to d involved in the determination process in step (S2)cFrom omegac0Instead of:
Figure GDA0002525428480000034
wherein, ω isc0Representing the rotor angular velocity of the synchronous phase modifier at an initial coasting point; k-24, 25, 26, 27 … …; when k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … ….
The invention discloses a method for setting an idle speed point for improving the idle speed grid-connection success rate of a synchronous phase modulator, which comprises the following steps of:
(S1) accelerating the rotor speed of the synchronous phase modifier to the initial idle speed point through the frequency conversion system, and measuring the initial idle speed pointPhase angle difference between synchronous phase modulator terminal voltage and power grid side voltage
Figure GDA0002525428480000035
(S2) based on the phase angle difference measured at the initial coasting Point
Figure GDA0002525428480000036
Frequency difference upper limit delta f required by grid connection*Upper limit of phase angle difference
Figure GDA0002525428480000037
Judging whether the final grid connection can be realized, if so, taking the initial idle speed point as a final idle speed point; and otherwise, sequentially accelerating the rotor speed of the current synchronous phase modulator to the next idle speed point through the frequency conversion system, judging whether the final grid connection can be realized or not based on the phase angle difference measured at each idle speed point until the idle speed point capable of realizing the final grid connection is found, and taking the found idle speed point as the final idle speed point.
In the step (S1), accelerating the rotor speed of the synchronous phase modulator to each of the idle points by the frequency conversion system includes: and transmitting the phase angle difference measured at each idle speed point as a feedback quantity to a control system of the frequency conversion system so as to control the acceleration of the synchronous phase modulator.
Further, the synchronous condenser rotor speed at the initial coasting point is about 1.05 times the rated speed.
In step (S2), the angular velocity ω of the synchronous phase modulator at each of the coasting pointscSatisfies the following conditions:
Figure GDA0002525428480000041
wherein, ω isc0The rotor angular velocity of the synchronous phase modifier at the initial idle speed point; omega0The angular speed is corresponding to the frequency of the power grid; d omega/dt is the angular speed slip during the phase modulator idling; when k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … ….
Judging whether the final grid connection can be realized or not based on the phase angle difference measured at each coasting speed point comprises the following steps:
when Δ f*When the condition a' is satisfied, if
Figure GDA0002525428480000042
If the condition b' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
when Δ f*When the condition c' is satisfied, if
Figure GDA0002525428480000043
If the condition d' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
the condition a':
Figure GDA0002525428480000044
condition b':
Figure GDA0002525428480000045
condition c':
Figure GDA0002525428480000046
under the condition d':
Figure GDA0002525428480000047
in the formula: Δ f*、
Figure GDA0002525428480000051
Respectively represents the upper limit of the frequency difference and the upper limit of the phase angle difference of the grid connection requirement, omegac0For synchronizing the rotor angular velocity, ω, of the phase modifier at the initial idle speed point0The angular speed corresponding to the power grid frequency, d omega/dt is the angular speed slip during the phase modulator idling,
Figure GDA0002525428480000052
mod represents the phase angle difference measurement from the grid side for each time the lazy point is reached, with a period of 360 being the remainder.
Has the advantages that: compared with the prior art, the method has the following advantages:
(1) whether grid connection is successful or not can be judged when the frequency difference and the phase angle difference meet grid connection conditions, and the judging method is simple and convenient, high in accuracy and free of experimental measurement in advance;
(2) the existing phase modulator idling grid-connected mode can only be started after the phase modulator stops running once grid-connected fails, so that certain resource waste is caused; the invention can adjust the phase angle difference of the synchronous phase modulator to the existence of the grid-connected point through the method of adjusting the idle speed point under the condition that the upper limit of the frequency difference and the upper limit of the phase angle difference required by grid connection are harsh, thereby effectively improving the grid-connected success rate of the novel synchronous phase modulator in the idle speed grid-connected mode and avoiding the resource waste caused by grid-connected failure.
In a word, the invention can realize the judgment of success of the energy and the grid connection, can greatly provide the grid connection success rate of the novel synchronous phase modulator in the idle grid connection mode, and has the advantages of simple circuit structure, easy control realization and higher practical engineering application value.
Drawings
Fig. 1 is a schematic diagram of a grid-connected topology according to an embodiment of the present invention;
FIG. 2(a) is a schematic diagram showing the variation of the rotor speed of the synchronous phase modulator with time when the frequency difference is positive at the final grid-connection time; FIG. 2(b) is a schematic diagram showing the variation of the rotor speed of the synchronous phase modulator with time when the frequency difference is negative at the final grid connection time;
FIG. 3(a) shows a frequency difference Δ f required for grid connection*0.1Hz, phase angle difference
Figure GDA0002525428480000053
A plot of phase modulator speed variation during idle speed conditions; FIG. 3(b) shows the frequency difference Δ f required for grid connection*0.15Hz, phase angle difference
Figure GDA0002525428480000054
And (5) setting process under the condition.
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the grid-connected topology according to the present invention includes: the device comprises a frequency conversion system, a control system, a quasi-synchronization device, a phase modulator, an excitation system, a main excitation loop and a starting excitation loop. The frequency conversion system preferably adopts an SFC static frequency conversion system. And in the phase modulator starting stage, starting an excitation circuit to access an excitation system, accessing an SFC static frequency conversion system to a phase modulator stator circuit, and carrying out speed-raising operation on the phase modulator under the control of a control system, wherein a quasi-synchronization device measures the frequency difference, the phase angle difference and the voltage difference between the stator terminal voltage of the synchronous phase modulator and the power grid side in real time. The controller determines whether the inertia speed point needs to be set or not based on the measurement result according to the method of the invention, and sets the inertia speed point as required to determine the final inertia speed point. After the final idle speed point is determined, the SFC static frequency conversion system is cut open, the excitation loop is started to be cut open, the main excitation loop is accessed to the excitation system, the machine end voltage is established, the phase modulator enters the idle speed stage, after the frequency difference, the phase angle difference and the voltage difference of the phase modulator on the power grid side, which are measured by the quasi-synchronization device, meet the grid-connected conditions, the control system sends an instruction to enable the phase modulator on the stator side to be accessed to a 500kV bus, and the phase modulator is connected to the power grid.
Firstly, the grid-connected requirement is analyzed based on the grid-connected topological structure, and a judgment condition for judging whether the grid connection can be successfully realized is obtained.
First, this constraint can be ignored since the voltage difference can be adjusted by the phase modulator excitation. Then, selecting a moment when the opening time of the frequency conversion system is 0, namely the starting moment of the idle speed, and the angular speed of the phase modulator is omega at the momentc(in the invention, the rotating speed of the phase modulator and the frequency of the power grid are both converted into electrical angular velocity with the unit of rad/s), and the phase angle difference between the phase modulator and the power grid is
Figure GDA0002525428480000061
The default is the angle of the power grid advanced phase modulator, and the angular speed of the power grid is omega0The final grid-connection time point is ta. Assuming a phase angle difference of grid-connection requirement of
Figure GDA0002525428480000062
Frequency difference of Deltaf*。
The method is characterized in that the following requirements are met under the constraint condition of frequency difference of grid connection requirements:
Figure GDA0002525428480000063
where d ω/dt is the angular velocity slip during the phase modulator coasting.
And respectively discussing phase angle difference constraint conditions required by grid connection according to the two conditions that the final grid connection time frequency difference is positive or negative.
1) The final grid connection time frequency difference is positive
The phase modulator speed variation is shown in fig. 2(a), and the angular difference constraint condition in this case is:
Figure GDA0002525428480000064
in the formula:
Figure GDA0002525428480000065
represents the amount of phase angle difference change during the coasting, i.e., the shading portion of the oblique stripes in fig. 2(a), and:
Figure GDA0002525428480000066
carry in and simplify:
Figure GDA0002525428480000071
2) the frequency difference at the final grid connection time is negative
The phase modulator speed variation is shown in fig. 2(b), in which case the angular difference constraint is:
Figure GDA0002525428480000072
in the formula:
Figure GDA0002525428480000073
and
Figure GDA0002525428480000074
the amount of change in the phase angle difference is represented,
Figure GDA0002525428480000075
representing the shading part of the oblique stripes in FIG. 2(b),
Figure GDA0002525428480000076
represents a cross-hatched portion in fig. 2(b), and:
Figure GDA0002525428480000077
Figure GDA0002525428480000078
carry in and simplify:
Figure GDA0002525428480000079
the two conditions are combined to obtain:
Figure GDA00025254284800000710
the solution of the equation set is a grid-connected point which meets the grid-connected requirement, and the solution of the equation set of the first two-dimensional equation can be obtained by:
① when satisfied
Figure GDA00025254284800000711
Time (i.e., condition a)
Where mod () represents a 360 cycle remainder.
The condition for the solution of the equation to exist (i.e., condition b) is:
Figure GDA00025254284800000712
②
Figure GDA0002525428480000081
time (i.e., condition c)
The condition for the solution of the equation to exist (i.e., condition d) is:
Figure GDA0002525428480000082
or
Figure GDA0002525428480000083
Therefore, by the method, whether the grid connection can be successfully carried out or not can be conveniently judged when the measured frequency difference and the measured phase angle difference meet the grid connection requirement.
However, with synchronous phase modifier rotor angular velocity ωcIn the above method for determining whether the grid connection is successful, the threshold value and ω are usedcIn relation thereto, the decision threshold or criterion is therefore also a function of ωcBut may vary. In order to ensure that the judgment standard of whether each idling point can be successfully connected to the grid remains unchanged, the omega of each idling point can be controlledcThe following conditions are satisfied:
Figure GDA0002525428480000084
in the formula: omegac0For synchronous condenser rotor angular velocity at the initial coast down point, k is 24, 25, 26, 27 … …. When k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … …. Thus, since the mod () function represents a remainder on 360, the following components included in all of conditions a through d are for ωcAnd ωc0The calculation results are consistent:
Figure GDA0002525428480000085
in other words, when ω iscWhen the specific value conditions are met, the process of judging whether the grid connection can be successfully carried out can be converted into the following steps:
when Δ f*When the condition a' is satisfied, if
Figure GDA0002525428480000086
If the condition b' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
when Δ f*When the condition c' is satisfied, if
Figure GDA0002525428480000087
If the condition d' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
the condition a':
Figure GDA0002525428480000091
condition b':
Figure GDA0002525428480000092
condition c':
Figure GDA0002525428480000093
under the condition d':
Figure GDA0002525428480000094
or
Figure GDA0002525428480000095
Based on the method for judging whether the synchronization can be successfully carried out, the method for setting the idle speed point for improving the idle speed synchronization success rate of the synchronous phase modulator is introduced below. The method specifically comprises the following steps:
step S1: in the initial stage of starting, the stator side of the phase modulator is connected to the SFC static frequency conversion system, under the coordination of a starting excitation loop, the rotor rotating speed of the synchronous phase modulator is accelerated to an initial idle speed point (namely an acceleration stop point commonly used in the industry, the corresponding rotor angular speed of the acceleration stop point is 1.05 times of the rated rotating speed), and a quasi-synchronization device measures the phase angle difference between the voltage at the end of the phase modulator and the voltage at the side of a power grid at the moment and transmits the phase angle difference as feedback information to a control system of the SFC static frequency conversion system so as to control the subsequent acceleration process, as shown in figure 1.
Step S2: judging whether final grid connection can be realized or not based on the phase angle difference measured at the initial idling speed point, if so, taking the initial idling speed point as a final idling speed point; and otherwise, sequentially accelerating the rotor speed of the current synchronous phase modulator to the next idle speed point through the frequency conversion system, judging whether the final grid connection can be realized or not based on the phase angle difference measured at each idle speed point until the idle speed point capable of realizing the final grid connection is found, and taking the found idle speed point as the final idle speed point.
The condition for judging whether the grid connection can be successfully carried out at each idle speed point is the same without the influence of the rotor angular speed omega of the synchronous phase modulatorcInfluence of variation, ω at each coasting PointcThe value of (a) should satisfy the following calculation formula:
Figure GDA0002525428480000101
in the formula: omegac0For synchronous condenser rotor angular velocity at the initial coast down point, k is 24, 25, 26, 27 … …. When k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … ….
In step S2, it is determined whether or not the final grid connection can be achieved by the method described above (i.e., the method including the conditions a 'to d').
The beneficial effects of the invention are verified by simulation, in the simulation, the angular speed slip value during the inertia speed period is derived from the frequency slip design value of the Zalutter phase modulator, namely d omega/dt is 0.12625 × 2 pi r/s, and the angular speed corresponding to the rated rotating speed is 100 pi r/s, namely 1.05 times of the rated rotating speedAngular velocity omegac0105 rr/s. FIGS. 3(a) and 3(b) show the phase modulator rotation speed ω with increasing k during the coasting point setting processcAnd phase angle difference measurement
Figure GDA0002525428480000102
The grey shaded area in the graph is the phase angle difference measured value which accords with the successful grid-connection condition
Figure GDA0002525428480000103
And (3) a range. FIG. 3(a) shows a frequency difference Δ f required for grid connection*0.1Hz, phase angle difference
Figure GDA0002525428480000104
Setting process under the condition, and FIG. 3(b) shows the frequency difference Δ f of the grid connection requirement*0.15Hz, phase angle difference
Figure GDA0002525428480000105
And (5) setting process under the condition. As can be seen, for the starting phase angle difference measurement
Figure GDA0002525428480000106
Under the condition of falling outside the gray shadow area, the inertia speed point setting method can effectively adjust the phase angle difference measurement value
Figure GDA0002525428480000107
So that the grid connection success area (namely the gray shaded area) is entered.
Therefore, the problem that grid connection failure caused by grid connection points possibly does not exist when the speed is accelerated to 1.05 times of rated rotating speed in the prior art can be solved. The method can judge whether the grid-connected point exists in the lazy speed period only by the phase angle difference measurement value at the acceleration finishing moment without going through the lazy speed process. If the grid-connected point does not exist, the system continues to accelerate the camera to the next idling point and then judges until the grid-connected point is judged to exist. Therefore, the invention can set the lazy speed point as the condition of the grid-connected point during the lazy speed period, thereby improving the grid-connected success rate.

Claims (7)

1. A method for judging whether a synchronous phase modulator is in idle speed synchronization success is characterized by comprising the following steps:
(S1) measuring the phase angle difference between the voltage of the synchronous phase modulator at the lazy-speed point and the voltage on the power grid side
Figure FDA0002525428470000011
(S2) phase angle difference based on measurement
Figure FDA0002525428470000012
Frequency difference upper limit delta f required by grid connection*Upper limit of phase angle difference
Figure FDA0002525428470000013
Judging whether the synchronization phase modulator is successfully connected to the grid at the idle speed point or not; the judging process comprises the following steps:
when Δ f*When the condition a is satisfied, if
Figure FDA0002525428470000014
If the condition b is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
when Δ f*When the condition c is satisfied, if
Figure FDA0002525428470000015
If the condition d is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
condition a:
Figure FDA0002525428470000016
condition b:
Figure FDA0002525428470000017
condition c:
Figure FDA0002525428470000018
condition d:
Figure FDA0002525428470000019
or
Figure FDA00025254284700000110
In the formula, ωcFor synchronizing the rotor angular velocity, omega, of phase-modifiers at the idle speed point0The angular speed corresponding to the power grid frequency, d omega/dt is the angular speed slip during the phase modulator idling,
Figure FDA00025254284700000111
mod represents the phase angle difference measurement from the grid side for each time the lazy point is reached, with a period of 360 being the remainder.
2. The method for judging whether the synchronous phase modulator can be lazily connected to the power grid according to claim 1, wherein when ω is ωcWhen the following conditions are satisfied, ω among the conditions a to d involved in the determination process in step (S2)cFrom omegac0Instead of:
Figure FDA0002525428470000021
wherein, ω isc0Representing the rotor angular velocity of the synchronous phase modifier at an initial coasting point; k-24, 25, 26, 27 … …; when k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … ….
3. A method for setting an idle speed point for improving the idle speed grid-connection success rate of a synchronous phase modulator is characterized by comprising the following steps:
(S1) accelerating the rotor speed of the synchronous phase modifier to an initial idling point through a frequency conversion system, and measuring the phase angle difference between the voltage of the synchronous phase modifier at the initial idling point and the voltage of the power grid side
Figure FDA0002525428470000022
(S2) based on the phase angle difference measured at the initial coasting Point
Figure FDA0002525428470000023
Frequency difference upper limit delta f required by grid connection*Upper limit of phase angle difference
Figure FDA0002525428470000024
Judging whether the final grid connection can be realized, if so, taking the initial idle speed point as a final idle speed point; and otherwise, sequentially accelerating the rotor speed of the current synchronous phase modulator to the next idle speed point through the frequency conversion system, judging whether the final grid connection can be realized or not based on the phase angle difference measured at each idle speed point until the idle speed point capable of realizing the final grid connection is found, and taking the found idle speed point as the final idle speed point.
4. The method for setting the lazy point to improve the success rate of the synchronization of the lazy synchronization of the synchronous phase modulators according to claim 3, wherein the rotor speed of the synchronous phase modulators at the initial lazy point is about 1.05 times of the rated speed.
5. The lazy-point adjustment method for increasing lazy-grid success rate of synchronous phase modulators according to claim 3, wherein in the step (S2), the angular velocity ω of the synchronous phase modulator at each lazy-pointcSatisfies the following conditions:
Figure FDA0002525428470000025
wherein, ω isc0The rotor angular velocity of the synchronous phase modifier at the initial idle speed point; omega0The angular speed is corresponding to the frequency of the power grid; d omega/dt is phase modifier inertiaAngular velocity slip during speed; k-24, 25, 26, 27 … …; when k is 24, corresponds to an initial coasting point, in which case ω isc＝ωc0(ii) a Each successive idler point corresponding to the initial idler point when k is 25, 26, 27 … ….
6. The method for improving the lazy point adjustment of the synchronization phase modulator lazy grid connection success rate according to claim 5, wherein in the step (S2), the step of judging whether the final grid connection can be realized based on the phase angle difference measured at each lazy point comprises:
when Δ f*When the condition a' is satisfied, if
Figure FDA0002525428470000031
If the condition b' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
when Δ f*When the condition c' is satisfied, if
Figure FDA0002525428470000032
If the condition d' is met, the grid connection success can be realized, otherwise, the grid connection failure is realized;
the condition a':
Figure FDA0002525428470000033
condition b':
Figure FDA0002525428470000034
condition c':
Figure FDA0002525428470000035
under the condition d':
Figure FDA0002525428470000036
or
Figure FDA0002525428470000037
In the formula: Δ f*、
Figure FDA0002525428470000038
Respectively represents the upper limit of the frequency difference and the upper limit of the phase angle difference of the grid connection requirement, omegac0For synchronizing the rotor angular velocity, ω, of the phase modifier at the initial idle speed point0The angular speed corresponding to the power grid frequency, d omega/dt is the angular speed slip during the phase modulator idling,
Figure FDA0002525428470000039
mod represents the phase angle difference measurement from the grid side for each time the lazy point is reached, with a period of 360 being the remainder.
7. The method for setting the lazy point to improve the lazy grid connection success rate of the synchronous phase modulator according to claim 3, wherein the step (S1) of accelerating the rotor speed of the synchronous phase modulator to each lazy point by the frequency conversion system comprises: and transmitting the phase angle difference measured at each idle speed point as a feedback quantity to a control system of the frequency conversion system so as to control the acceleration of the synchronous phase modulator.
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