CN112271739A - Direct current transmission end power grid subsynchronous oscillation risk assessment method under wind-solar-fire deep peak regulation mode - Google Patents

Direct current transmission end power grid subsynchronous oscillation risk assessment method under wind-solar-fire deep peak regulation mode Download PDF

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CN112271739A
CN112271739A CN202011351734.6A CN202011351734A CN112271739A CN 112271739 A CN112271739 A CN 112271739A CN 202011351734 A CN202011351734 A CN 202011351734A CN 112271739 A CN112271739 A CN 112271739A
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田蓓
徐树文
李宏强
王峰
张爽
牛琳琳
周雷
乔小敏
刘海涛
张星
张迪
薛飞
刘敏
徐得超
王祥旭
徐翌征
王跃
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China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Ningxia Electric Power Co Ltd
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Electric Power Research Institute of State Grid Ningxia Electric Power Co Ltd
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Abstract

The invention provides a method for evaluating the risk of subsynchronous oscillation of a direct-current transmission end power grid in a wind-solar-fire deep peak shaving mode, and belongs to the technical field of power systems. The method comprises the following steps: acquiring subsynchronous oscillation characteristic sample data of a direct current transmission end power grid under the background of wind-solar-fire peak regulation; screening subsynchronous oscillation characteristic sample data until the subsynchronous oscillation characteristic sample data meet a convergence condition to obtain subsynchronous oscillation characteristic data; calculating a comprehensive subsynchronous oscillation risk probability coefficient R according to a subsynchronous oscillation risk comprehensive evaluation modelSSO(t); according to the comprehensive subsynchronous oscillation risk probability coefficient RSSO(t) direct current sending end under mode of evaluating wind-solar fire depth peak regulationAnd (5) power grid subsynchronous oscillation risk. According to the method, a direct current sending end subsynchronous oscillation risk evaluation model under a wind-light-fire peak regulation mode is established, subsynchronous oscillation risk evaluation accuracy is improved, effective data support is provided for power grid dispatching, stable operation of a power grid is maintained, and operation and maintenance reliability of the power grid is enhanced.

Description

Direct current transmission end power grid subsynchronous oscillation risk assessment method under wind-solar-fire deep peak regulation mode
Technical Field
The invention belongs to the technical field of power systems, and particularly relates to a method for evaluating the risk of subsynchronous oscillation of a direct-current transmission end power grid in a wind-solar-fire deep peak shaving mode.
Background
In actual power grid operation, in order to maintain the power grid operation stability in a wind, light and fire peak regulation mode, various modes of wind, light and fire are often adopted to maintain the power grid stability by peak clipping and valley filling. However, in actual operation, the parameters of each generator set of the wind power plant, the photovoltaic power plant and the thermal power plant are different, so that the corresponding operation mode and the control parameters are different, the distribution geographical positions of the generator sets are different, the short circuit ratio of the grid-connected point is reduced due to the increase of the grid-connected quantity and the types of the generator sets, and a weak alternating current system is formed, so that the risk of subsynchronous oscillation is very likely to occur in the deep peak shaving mode of wind, light and fire. The existing evaluation method for the sub-synchronous oscillation risk of the direct current sending end power grid is poor in accuracy, difficult to realize comprehensive evaluation and incapable of meeting the evaluation requirement of the sub-synchronous oscillation risk of the direct current sending end power grid in a wind-light-fire deep peak regulation mode.
Disclosure of Invention
In view of the above, the invention provides a method for evaluating the risk of subsynchronous oscillation of a direct-current transmission end power grid in a wind-light-fire deep peak shaving mode, so as to solve the technical problems that the evaluation method for the risk of subsynchronous oscillation of the direct-current transmission end power grid in the prior art is poor in accuracy and cannot meet the evaluation requirement for the risk of subsynchronous oscillation of the direct-current transmission end power grid in the wind-light-fire deep peak shaving mode.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a direct current transmission end power grid subsynchronous oscillation risk assessment method under a wind-solar-fire deep peak regulation mode comprises the following steps:
acquiring subsynchronous oscillation characteristic sample data of a direct current transmission end power grid under the background of wind-solar-fire peak regulation;
screening subsynchronous oscillation characteristic sample data until the subsynchronous oscillation characteristic sample data meet a convergence condition to obtain subsynchronous oscillation characteristic data;
calculating a comprehensive subsynchronous oscillation risk probability coefficient R according to a subsynchronous oscillation risk comprehensive evaluation modelSSO(t); the subsynchronous oscillation risk comprehensive evaluation model is shown as the formula I:
Figure BDA0002801496700000021
in the formula, gamma is the deviation of the grid connection process and the quasi-synchronization condition under the actual wind-light-fire peak regulation mode; i issThe current is the impact current generated when deviation occurs; mnAn electromagnetic moment to be generated for the occurrence of the deviation; thetaPLnRespectively representing the corresponding output phase angles of the wind, light and fire; cflnA compensation capacitor is connected in series with the three-side loop of the wind-light-fire power supply; t isLLow amplitude torsional vibration for a long time; dfsThe shafting is damaged due to long-time low-amplitude torsional vibration accumulation; zr is the wind resistance value in the wind turbine generator; h is1、h2、h3Respectively are damping characteristic coefficients corresponding to wind, light and fire; omega is the angular velocity of the rotating machine of the brake disk, rad.s-1(ii) a p represents a differential operator; mACnWhen non-synchronous paralleling with 120 degrees phase angle is output, electromagnetic torque corresponding to the three-side loop of the wind-light fire is output; rgnCorresponding parasitic resistance of the wind-solar-fire three-side loop; rhonThe ratio of wind, light and fire to the network is determined; l isflnThe wind, light and fire are respectively filter inductors; etanRepresenting the transmission efficiency of the corresponding wind, light and fire line; fTVElectromechanical torsional vibration of a thermal power generating unit; t isLCThe compensation tolerance of the series compensation capacitor and the loop is set; cSCnA compensation capacitor is connected in series with the wind-solar-energy live line; t is t0To generate an asynchronous motor effect threshold;
according to the comprehensive subsynchronous oscillation risk probability coefficient RSSOAnd (t) evaluating the sub-synchronous oscillation risk of the direct current transmission end power grid in the wind-solar-fire deep peak regulation mode.
Preferably, the probability coefficient R of risk of oscillation according to the comprehensive subsynchronousSSO(t) evaluating the subsynchronous oscillation risk of the direct-current transmission end power grid in the wind-solar-fire deep peak regulation mode, comprising the following steps of:
when at
Figure BDA0002801496700000031
When within the constraint range, RSSO(t) is less than 0.32, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the subsynchronous oscillation risk is low;
when at
Figure BDA0002801496700000032
Within the restricted range, R is more than 0.84SSO(t) is less than or equal to 1, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the risk of subsynchronous oscillation is low.
Preferably, the step of screening the subsynchronous oscillation feature sample data until the subsynchronous oscillation feature sample data meets the convergence condition to obtain the subsynchronous oscillation feature data includes the following steps:
adopting a convergence model to output power to the wind, light and fire three ends
Figure BDA0002801496700000033
Screening to obtain effective convergence wind-light-fire three-terminal output power
Figure BDA0002801496700000034
Wherein k is<n；P1,tk、P2,tk、P3,tkAnd respectively representing the output power of the wind-solar-fire three ends at the time t.
Preferably, the convergence model is as shown in formula ii:
Figure BDA0002801496700000035
in the formula, P1,t max、P2,t max、P3,t maxRespectively representing the maximum value of the output power of the wind-solar-fire three ends at the moment t; eta1 max、η2 max、η3 maxRespectively, represent the maximum value of the transmission efficiency of the wind, solar and fire line.
Preference is given toIn the ground, the damage D of the shafting caused by the long-time low-amplitude torsional vibration accumulation is calculated by the formula IIIfs：
Figure BDA0002801496700000036
In the formula, U (t) is a voltage time function which is output in a mixed mode except for an actual measured value and is related to time under a wind-solar-fire depth peak regulation mode; u' (t) is the derivative of U (t).
Preferably, the damping characteristic coefficient h corresponding to wind-solar fire is calculated by the formula IV1、h2And h3。
Figure BDA0002801496700000041
Figure BDA0002801496700000046
Figure BDA0002801496700000042
Preferably, the electromagnetic moment M generated by the deviation is calculated by formula Vn
Figure BDA0002801496700000043
Wherein C is a fixed constant, and is related to the characteristics of the respective motors; u shapenInputting a voltage; x20Is a rotor leakage inductance; snIs the slip.
Preferably, when asynchronous paralleling with 120-degree output phase angle is calculated through the formula VI, the electromagnetic moment M corresponding to the three-side loop of the wind-light fire is calculatedACn：
Figure BDA0002801496700000044
In the formula, phisccThe shafting torsional vibration of the steam turbine generator unit caused by series capacitance compensation; i is the input current.
Preferably, the electromechanical torsional vibration F of the thermal power generating unit is calculated through the formula VIITV。
Figure BDA0002801496700000045
Preferably, the series compensation capacitance and the loop compensation tolerance T are calculated by the formula VIIILC。
Figure BDA0002801496700000051
According to the technical scheme, the invention provides a method for evaluating the sub-synchronous oscillation risk of a direct current transmission end power grid in a wind-light-fire deep peak regulation mode, which has the beneficial effects that: the method comprises the steps of establishing a direct current sending end subsynchronous oscillation risk assessment model under a wind-light-fire peak regulation mode, comprehensively assessing a power grid subsynchronous oscillation risk of a direct current sending end under a wind-light-fire deep peak regulation mode, improving subsynchronous oscillation risk assessment accuracy, providing effective data support for power grid scheduling, maintaining stable operation of a power grid, and enhancing operation and maintenance reliability of the power grid.
Drawings
FIG. 1 is a flow chart of a direct current transmission end power grid subsynchronous oscillation risk assessment method in a wind-solar-fire deep peak shaving mode.
Detailed Description
The technical scheme and the technical effect of the invention are further elaborated in the following by combining the drawings of the invention.
Referring to fig. 1, in an embodiment, a method for evaluating a risk of subsynchronous oscillation of a dc transmission-side power grid in a wind-solar-fire deep peak shaving mode includes the following steps:
acquiring subsynchronous oscillation characteristic sample data of a direct current transmission end power grid under the background of wind-solar-fire peak regulation;
screening subsynchronous oscillation characteristic sample data until the subsynchronous oscillation characteristic sample data meet a convergence condition to obtain subsynchronous oscillation characteristic data;
calculating a comprehensive subsynchronous oscillation risk probability coefficient R according to a subsynchronous oscillation risk comprehensive evaluation modelSSO(t); the subsynchronous oscillation risk comprehensive evaluation model is shown as the formula I:
Figure BDA0002801496700000061
in the formula, gamma is the deviation of the grid connection process and the quasi-synchronization condition under the actual wind-light-fire peak regulation mode; i issThe current is the impact current generated when deviation occurs; mnAn electromagnetic moment to be generated for the occurrence of the deviation; thetaPLnRespectively representing the corresponding output phase angles of the wind, light and fire; cflnA compensation capacitor is connected in series with the three-side loop of the wind-light-fire power supply; t isLLow amplitude torsional vibration for a long time; dfsThe shafting is damaged due to long-time low-amplitude torsional vibration accumulation; zr is the wind resistance value in the wind turbine generator; h is1、h2、h3Respectively are damping characteristic coefficients corresponding to wind, light and fire; omega is the angular velocity of the rotating machine of the brake disk, rad.s-1(ii) a p represents a differential operator; mACnWhen non-synchronous paralleling with 120 degrees phase angle is output, electromagnetic torque corresponding to the three-side loop of the wind-light fire is output; rgnCorresponding parasitic resistance of the wind-solar-fire three-side loop; rhonThe ratio of wind, light and fire to the network is determined; l isflnThe wind, light and fire are respectively filter inductors; etanRepresenting the transmission efficiency of the corresponding wind, light and fire line; fTVElectromechanical torsional vibration of a thermal power generating unit; t isLCThe compensation tolerance of the series compensation capacitor and the loop is set; cSCnA compensation capacitor is connected in series with the wind-solar-energy live line; t is t0To generate an asynchronous motor effect threshold;
according to the comprehensive subsynchronous oscillation risk probability coefficient RSSOAnd (t) evaluating the sub-synchronous oscillation risk of the direct current transmission end power grid in the wind-solar-fire deep peak regulation mode.
Specifically, the probability coefficient R according to the comprehensive subsynchronous oscillation riskSSO(t) evaluation of wind-solar fire depth modulationUnder the peak mode, the subsynchronous oscillation risk of the direct-current transmission end power grid comprises the following processes:
when at
Figure BDA0002801496700000062
When within the constraint range, RSSO(t) is less than 0.32, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the subsynchronous oscillation risk is low;
when at
Figure BDA0002801496700000063
Within the restricted range, R is more than 0.84SSO(t) is less than or equal to 1, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the risk of subsynchronous oscillation is low.
In a specific embodiment, collecting sub-synchronous oscillation characteristic sample data of a direct current transmission end power grid under the background of wind, light and fire peak regulation comprises collecting relevant parameter data which is easy to cause sub-synchronous oscillation for the direct current transmission end power grid under the background of wind, light and fire peak regulation, wherein relevant parameters at the power grid side mainly comprise: wind power grid point voltage UWPPhotovoltaic grid-connected point voltage UPVThermal power grid-connected point voltage UTPWind power grid point current IWPPhotovoltaic grid-connected point current IPVGrid-connected point current I of thermal powerTPThe output power of the wind, light and fire three ends is P1,t、P2,t、P3,t(ii) a Filter capacitor CflnFilter inductor Lfln. The measured parameters in the control circuit include: thetaPLnRespectively representing the corresponding output phase angles of the wind-light fire. EtanRepresenting transmission efficiency and small-voltage signal disturbance value of corresponding wind-solar-fire line
Figure BDA0002801496700000071
Small signal disturbance value of current
Figure BDA0002801496700000072
Corresponding parasitic resistance RgnRatio of wind, light and fire to each othernSubsynchronous oscillation risk probability index RSSO(t) of (d). Wherein, subscript n is 1, 2, 3 minutesRespectively corresponding to the corresponding parameters of the spectral fire. The shafting torsional vibration of the steam turbine generator unit caused by direct current transmission is phidctThe shafting torsional vibration of the turbo generator set caused by series capacitance compensation is phiscc。
And after the data are collected, screening out values which accord with the load characteristics for calculation, and establishing a direct current transmission end power grid torsional vibration coefficient equation under the wind-solar-fire deep peak regulation mode.
For example, data is combined
Figure BDA0002801496700000073
Screening by substituting constraint conditions of formula (II) to obtain effective convergence data
Figure BDA0002801496700000074
Where n > k, P1,tk、P2,tk、P3,tkAnd respectively representing the output power of the wind-solar-fire three ends at the time t. The constraint judgment conditions for the wind, light and fire data convergence screening are as follows:
Figure BDA0002801496700000075
in the formula, P1,t max、P2,t max、P3,t maxRespectively representing the maximum value of the output power of the wind-solar-fire three ends at the moment t; eta1 max、η2 max、η3 maxRespectively, represent the maximum value of the transmission efficiency of the wind, solar and fire line.
In the wind-light-fire deep peak regulation mode, the wind-light-fire three-side loop series compensation capacitors of the direct-current transmission end power grid are respectively represented as Cfl1、Cfl2、Cfl3When a thermal power generating unit steam turbine generates torsional stress to cause damage to a shaft system, low-amplitude torsional vibration T is generated for a long timeLAccumulation of damage to shafting DfsAt a critical value t0The pre-induced asynchronous motor effect is expressed as formula III:
Figure BDA0002801496700000081
in the formula, U (t) is a voltage time function which is output in a mixed mode except for an actual measured value and is related to time under a wind-solar-fire depth peak regulation mode; u' (t) is the derivative of U (t).
Because the parameter models of all the generator sets are different, after a shafting is damaged, the wind resistance value of a typical structure of a fan in the wind turbine generator set is taken as
Figure BDA0002801496700000082
Correspondingly solving the damping characteristic curve corresponding to wind, light and fire as a formula IV:
Figure BDA0002801496700000083
Figure BDA0002801496700000084
Figure BDA0002801496700000085
in a direct current sending end power grid combined node in an actual wind-light-fire peak regulation mode, quasi-synchronization conditions are difficult to completely meet in a grid connection process, and an impact current I is generated when a deviation gamma occursSAnd the impact current and the deviation are in direct proportion, and the linear expression is IS＝γcosθPLn(t) I, the relationship of the magnitude of the electromagnetic torque generated at the same time is V
Figure BDA0002801496700000086
Wherein C is a fixed constant, and is related to the characteristics of the respective motors; u shapenInputting a voltage; x20Is a rotor leakage inductance; snIs the slip. At thetaPLLWhen the switch is closed at a deviation angle of 180 °, the rush current is maximum, and this is considered to beThe most serious non-contemporaneous juxtaposition; the probability of subsynchronous oscillation occurring is greatly increased. The subsynchronous oscillation risk probability at this time is:
Figure BDA0002801496700000091
if the relationship between the electromechanical interaction and the subsynchronous oscillation is considered, first, from the viewpoint of torsional oscillation analysis of the axis system of the unit, when the closing angle is thetaPLnWhen the wind-solar-thermal power generation device is parallel to about 120 degrees, the electromagnetic torque is the largest, the torsional vibration response of a shafting is the most serious, and therefore the wind-solar-thermal power generation device corresponds to the wind-solar-thermal voltage UWP、UPV、UTPThe phase angle difference of 120 degrees is taken as the key point of torsional vibration analysis, and according to an empirical formula, electromagnetic moment expressions which correspond to 120 degrees and are not in parallel at the same time can be obtained and are shown as a formula VI:
Figure BDA0002801496700000092
where ω is the angular velocity of the rotating machine of the brake disk, rad · s-1And I is the input current. For the obtained result MACnTaking an absolute value, and solving the electromechanical torsional vibration F of the thermal power generating unit in the next stepTVSolving the output (shown in formula VII).
Figure BDA0002801496700000093
In the formula, p represents a differential operator.
Secondly, in a scene of wind, light and fire deep peak regulation, the proportion of the three is adjusted along with the gradual increase of time, and in an initial stage, in a scene of small proportion of fire participation, the whole tends to be stable, and along with the increase of power consumption at a load side, the participation proportion at the current stage cannot maintain the continuous long-term stable operation of a power grid. The input proportion of the thermal power generating unit is increased, and deep peak regulation is participated. At the moment, each line is connected with a compensation capacitor C in seriesSCnTends to be unstable, is easy to generate unstable oscillation phenomenon, and has series compensation capacitor and loop compensation tolerance TLCAre transferred betweenThe function is as in formula VIII.
Figure BDA0002801496700000101
Electromechanical torsional vibration output F of thermal power generating unitTVIn deep peak-shaving mode, series compensation capacitor CSCnUnder action, the relation becomes:
Figure BDA0002801496700000102
the subsynchronous oscillation risk probability index at this time is expressed as:
Figure BDA0002801496700000103
integrating the above expression, under the electromechanical torsional vibration interaction and in a relevant scene, the subsynchronous oscillation risk probability is:
Figure BDA0002801496700000104
synthesizing subsynchronous oscillation risk probability parameters, and increasing the proportion of thermal power participation in the wind-solar-thermal deep peak regulation mode at a critical value t0Before, the asynchronous motor effect is generated, the risk probability of subsynchronous oscillation is improved, and when t0＜t＜tmaxWhen the proportion of the thermal power is more than 60%, the asynchronous motor effect is gradually reduced, but the probability trend of the associated subsynchronous oscillation risk is gradually reduced due to the fact that the electromagnetic torque of the unit is increased and the torsional vibration of the derivative machine is acted, but when the proportion of the thermal power is more than 60%, the probability trend of the associated subsynchronous oscillation risk is gradually reduced
Figure BDA0002801496700000105
The risk probability is increased sharply, and in conclusion, the subsynchronous oscillation risk comprehensive evaluation index is shown as formula I:
Figure BDA0002801496700000106
the technical scheme and technical effects of the present invention are further described below by a specific embodiment.
According to a certain place in northeast, the following data are actually measured, wherein the relevant parameters of the power grid side mainly comprise: wind power grid point voltage UWP660V, photovoltaic grid-connected point voltage UPV380V, thermal power grid point voltage UTP35kV, wind power grid point current IWP12A, photovoltaic grid-connected point current IPV18.2A, thermal power point-connected current ITP60A. Filter capacitor Cfl500 muF, filter inductance LflAt 100 μ F, the measured parameters in the control circuit include: etan＝[70％:65％:60％]Representing the transmission efficiency of the corresponding wind, light and fire line and the corresponding parasitic resistance Rgn＝[800:1000:2000]。
Taking a typical participation proportion rho under two actual wind-solar fire depth peak regulation modesn＝[ρ1,ρ2]Respectively, [ 50%: 30%: 20 percent of]、[30％：20％：50％]。
And after the data are collected, screening out values which accord with the load characteristics for calculation, and establishing a direct current transmission end power grid torsional vibration coefficient equation under the wind-solar-fire deep peak regulation mode.
Data to be recorded
Figure BDA0002801496700000111
Screening is carried out in place of the constraint conditions of formula (II). Substituting the data, and screening to obtain effective convergence data
Figure BDA0002801496700000112
In the wind-light-fire deep peak regulation mode, the wind-light-fire three-side loop series compensation capacitors of the direct-current transmission end power grid are respectively represented as Cfl1＝500μF、Cfl2＝450μF、Cfl3＝550μF，TLD is obtained from formula iii, wherein 1499.95 is about 1500fs＝325。
Because the parameter models of the generator sets are different, after a shafting is damaged, the wind resistance of a typical structure of a fan in the wind turbine generator setValue is taken as
Figure BDA0002801496700000113
The typical solution of the damping characteristic corresponding to wind, light and fire is solved correspondingly as follows:
Figure BDA0002801496700000121
Figure BDA0002801496700000122
Figure BDA0002801496700000123
wherein
Figure BDA0002801496700000124
Find h1＝3.25，h2＝6.98，h3＝5.74。
In a direct current sending end power grid combined node in an actual wind-light-fire peak regulation mode, quasi-synchronization conditions are difficult to completely meet in a grid connection process, and an impact current I is generated when a deviation gamma occursSAnd the impact current and the deviation are in direct proportion, and the linear expression is IS＝γcosθPLLI, the magnitude relation of the electromagnetic torque generated simultaneously is
Figure BDA0002801496700000125
Wherein, C ═ 36; u shapen＝380V；X201000 Ω is the leakage inductance of the rotor; sn0.6. At thetaPLnWhen the switch is switched on at a deviation angle of 180 degrees, the impact current is the largest, and at the moment, the most serious asynchronous parallel condition is generally considered; the probability of subsynchronous oscillation occurring is greatly increased. The subsynchronous oscillation risk probability at this time is:
Figure BDA0002801496700000126
to obtain
Figure BDA0002801496700000127
From the angle of torsional vibration analysis of a unit shafting, when the closing angle is thetaPLLWhen the wind-solar-thermal power generation device is parallel to about 120 degrees, the electromagnetic torque is the largest, the torsional vibration response of a shafting is the most serious, and therefore the wind-solar-thermal power generation device corresponds to the wind-solar-thermal voltage UWP、UPV、UTPThe phase angle difference of 120 degrees is taken as the key point of torsional vibration analysis, and according to the formula VI, the electromagnetic moments M corresponding to 120 degrees when in non-synchronous parallel can be obtainedACn＝[60 85 42]. Where ω is 87.82, rad · s-1. For the obtained result MACnTaking an absolute value, and carrying out next step on solving the electromechanical torsional vibration F of the thermal power generating unit through a formula VIITVSolving of the output to obtain FTV＝1065。
Step 3.2: p represents a differential operator. In the scene of wind, light and fire deep peak regulation, the proportion of the three is adjusted along with the gradual increase of time, and in the initial stage, in the scene of small proportion of fire electricity, the whole tends to be stable, and along with the increase of the power consumption at the load side, the participation proportion at the current stage can not maintain the long-term stable operation of the power grid. The input proportion of the thermal power generating unit is increased, and deep peak regulation is participated. At the moment, each line is connected with a compensation capacitor C in seriesSCnTends to be unstable, is easy to generate unstable oscillation phenomenon, and has series compensation capacitor and loop compensation tolerance TLCThe transfer function between is as follows.
Figure BDA0002801496700000131
Find TLC(S) and inverse Laplace transform to obtain TLC＝0.68
Electromechanical torsional vibration output F of thermal power generating unitTVIn deep peak-shaving mode, series compensation capacitor CSCnUnder the action of the action, the relational expression becomes
Figure BDA0002801496700000132
The subsynchronous oscillation risk probability index is expressed as
Figure BDA0002801496700000133
Step 3.3: integrating the above expression, under the electromechanical torsional vibration interaction and in a relevant scene, the subsynchronous oscillation risk probability is:
Figure BDA0002801496700000134
finishing to obtain:
Figure BDA0002801496700000135
synthesizing subsynchronous oscillation risk probability parameters, and increasing the proportion of thermal power participation in the wind-solar-thermal deep peak regulation mode at a critical value t0Before, the asynchronous motor effect is generated, the risk probability of subsynchronous oscillation is improved, and when t0＜t＜tmaxWhen the proportion of the thermal power is more than 60%, the asynchronous motor effect is gradually reduced, but the probability trend of the associated subsynchronous oscillation risk is gradually reduced due to the fact that the electromagnetic torque of the unit is increased and the torsional vibration of the derivative machine is acted, but when the proportion of the thermal power is more than 60%, the probability trend of the associated subsynchronous oscillation risk is gradually reduced
Figure BDA0002801496700000141
The risk probability is increased sharply, and in conclusion, the subsynchronous oscillation risk comprehensive evaluation index is
Figure BDA0002801496700000142
Wherein the content of the first and second substances,
Figure BDA0002801496700000143
when at
Figure BDA0002801496700000144
When within the constraint range, RSSOAnd (t) is less than 0.32, the subsynchronous oscillation risk probability is considered to be extremely high, and the wind-light fire output is effectively adjusted to perform adjustment.
When at
Figure BDA0002801496700000145
Within the restricted range, R is more than 0.84SSOAnd (t) is less than or equal to 1, namely the subsynchronous oscillation risk probability is considered to be extremely high, at the moment, the participation proportion of the line capacitance is effectively adjusted, and the line is overhauled to be effectively adjusted.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (10)

1. A direct current sending end power grid subsynchronous oscillation risk assessment method under a wind-solar-fire deep peak regulation mode is characterized by comprising the following steps:
acquiring subsynchronous oscillation characteristic sample data of a direct current transmission end power grid under the background of wind-solar-fire peak regulation;
screening subsynchronous oscillation characteristic sample data until the subsynchronous oscillation characteristic sample data meet a convergence condition to obtain subsynchronous oscillation characteristic data;
calculating a comprehensive subsynchronous oscillation risk probability coefficient R according to a subsynchronous oscillation risk comprehensive evaluation modelSSO(t); the subsynchronous oscillation risk comprehensive evaluation model is shown as the formula I:
Figure FDA0002801496690000011
in the formula, gamma is the deviation of the grid connection process and the quasi-synchronization condition under the actual wind-light-fire peak regulation mode; i issThe current is the impact current generated when deviation occurs; mnElectromagnetic fields generated for deviationsMoment of force; thetaPLnRespectively representing the corresponding output phase angles of the wind, light and fire; cflnA compensation capacitor is connected in series with the three-side loop of the wind-light-fire power supply; t isLLow amplitude torsional vibration for a long time; dfsThe shafting is damaged due to long-time low-amplitude torsional vibration accumulation; zr is the wind resistance value in the wind turbine generator; h is1、h2、h3Respectively are damping characteristic coefficients corresponding to wind, light and fire; omega is the angular velocity of the rotating machine of the brake disk, rad.s-1(ii) a p represents a differential operator; mACnWhen non-synchronous paralleling with 120 degrees phase angle is output, electromagnetic torque corresponding to the three-side loop of the wind-light fire is output; rgnCorresponding parasitic resistance of the wind-solar-fire three-side loop; rhonThe ratio of wind, light and fire to the network is determined; l isflnThe wind, light and fire are respectively filter inductors; etanRepresenting the transmission efficiency of the corresponding wind, light and fire line; fTVElectromechanical torsional vibration of a thermal power generating unit; t isLCThe compensation tolerance of the series compensation capacitor and the loop is set; cSCnA compensation capacitor is connected in series with the wind-solar-energy live line; t is t0To generate an asynchronous motor effect threshold;
according to the comprehensive subsynchronous oscillation risk probability coefficient RSSOAnd (t) evaluating the sub-synchronous oscillation risk of the direct current transmission end power grid in the wind-solar-fire deep peak regulation mode.
2. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind-solar-fire deep peak shaving mode according to claim 1, wherein the risk probability coefficient R is based on the comprehensive subsynchronous oscillationSSO(t) evaluating the subsynchronous oscillation risk of the direct-current transmission end power grid in the wind-solar-fire deep peak regulation mode, comprising the following steps of:
when at
Figure FDA0002801496690000021
0＜t≤t0When within the constraint range, RSSO(t) is less than 0.32, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the subsynchronous oscillation risk is low;
when at
Figure FDA0002801496690000022
t0＜t≤tmaxWithin the restricted range, R is more than 0.84SSO(t) is less than or equal to 1, the evaluation result is that the subsynchronous oscillation risk is high; otherwise, the evaluation result is that the risk of subsynchronous oscillation is low.
3. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid under the wind-solar-fire deep peak shaving mode according to claim 1, wherein the step of screening subsynchronous oscillation characteristic sample data until the subsynchronous oscillation characteristic sample data meets a convergence condition to obtain the subsynchronous oscillation characteristic data comprises the following steps: adopting a convergence model to output power to the wind, light and fire three ends
Figure FDA0002801496690000023
Screening to obtain effective convergence wind-light-fire three-terminal output power
Figure FDA0002801496690000024
Wherein k is<n；P1,tk、P2,tk、P3,tkAnd respectively representing the output power of the wind-solar-fire three ends at the time t.
4. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind-solar-fire deep peak shaving mode according to claim 3, wherein the convergence model is as shown in formula II:
Figure FDA0002801496690000025
in the formula, P1,t max、P2,t max、P3,t maxRespectively representing the maximum value of the output power of the wind-solar-fire three ends at the moment t; eta1 max、η2 max、η3 maxRespectively, represent the maximum value of the transmission efficiency of the wind, solar and fire line.
5. As in claimThe method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind-solar-fire deep peak regulation mode is characterized in that D, which is used for calculating shafting damage caused by long-time low-amplitude torsional oscillation accumulation through formula IIIfs：
Figure FDA0002801496690000031
In the formula, U (t) is a voltage time function which is output in a mixed mode except for an actual measured value and is related to time under a wind-solar-fire depth peak regulation mode; u' (t) is the derivative of U (t).
6. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind-solar-fire deep peak shaving mode according to claim 1, wherein the damping characteristic coefficient h corresponding to wind-solar-fire is calculated by a formula IV1、h2And h3。
Figure FDA0002801496690000032
Figure FDA0002801496690000033
Figure FDA0002801496690000034
7. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind, light and fire deep peak regulation mode according to claim 1, wherein the deviation is calculated by formula V to generate the electromagnetic moment Mn：
Figure FDA0002801496690000035
Wherein C is a fixed constant, and is related to the characteristics of the respective motors; u shapenInputting a voltage; x20Is a rotor leakage inductance; snIs the slip.
8. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid under the wind-solar-fire deep peak regulation mode according to claim 1, wherein the electromagnetic moment M corresponding to the wind-solar-fire three-side loop when asynchronous paralleling with an output phase angle of 120 degrees is calculated through a formula VIACn：
Figure FDA0002801496690000041
In the formula, phisccThe shafting torsional vibration of the steam turbine generator unit caused by series capacitance compensation; i is the input current.
9. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid under the wind-solar-fire deep peak shaving mode according to claim 1, characterized in that the electromechanical torsional oscillation F of the thermal power generating unit is calculated through a formula VIITV。
Figure FDA0002801496690000042
10. The method for evaluating the risk of subsynchronous oscillation of the direct-current transmission-end power grid in the wind-solar-fire deep peak shaving mode according to claim 1, wherein the series compensation capacitance and the loop compensation tolerance T are calculated according to a formula VIIILC。
Figure FDA0002801496690000043
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