Multi-source integrated configuration sending end power grid frequency safety and stability control method

Abstract

The embodiment of the invention provides a multi-source integrated configuration sending end power grid frequency safety and stability control method, and relates to the technical field of power grids. The method comprises the steps that a high-frequency generator tripping scheme is set, the generator tripping amount of each round is solved, and the setting target of the high-frequency generator tripping scheme is that the generator tripping amount is minimum; setting constraint conditions of the high-frequency generator tripping scheme; setting an interval value between turns; setting extreme anticipated DC power disturbance; supposing that the high-frequency generator tripping scheme is set in the first i-1 rounds, respectively cutting off the units P1, P2,..., Pi-1; the generator tripping capacity of the high-frequency generator tripping scheme is obtained by solving the generator tripping amount of each turn; after determining the total generator tripping amount of each direct current drop point, averagely distributing to each direct current drop point according to the generator tripping amount of each round; and checking the power flow under the direct current locking condition. The method can ensure that the line transmission power is within a limited range, and avoids the influence of secondary disturbance on the system stability.

Description

Technical Field

[0001] The present invention relates to the technical field of power grids, and in particular to a method for safely and stably controlling the frequency of a sending-end power grid with a multi-source integrated configuration. Background Art

[0002] There are many types of power units in the domestic power grid, such as thermal power units, hydropower units, wind power units and other renewable energy power generation. In view of the high-frequency problem after the multi-source coexisting transmission system is operated in an isolated grid, existing studies have theoretically analyzed the impact of wind power access on the system frequency characteristics and proposed a high-frequency control idea for the multi-source coexisting transmission system. Combined with the high-frequency problems existing in the actual power grid, the simulation analysis of the impact of wind power access ratio, the size of the isolated grid's excess active power, the conventional unit startup mode and the load level change on the isolated grid frequency characteristics, proposed a high-frequency control strategy that considers the frequency-dominant factor, and verified the proposed strategy. Summary of the invention

[0003] The purpose of the present invention includes providing a method for safe and stable control of the frequency of a sending-end power grid with a multi-source integrated configuration, which can ensure that the line transmission power is within its limited range and avoid secondary disturbances affecting the stability of the system.

[0004] The embodiments of the present invention can be implemented as follows:

[0005] The present invention provides a method for controlling the frequency of a multi-source integrated configuration sending-end power grid safely and stably, the method comprising:

[0006] S1: Set a high-frequency cutting plan and solve the cutting amount in each round. The setting target of the high-frequency cutting plan is to minimize the cutting amount and ensure that the power disturbance P caused by the expected DC fault is dist ≤P dist.max , P dist.max is the maximum remaining power of the system;

[0007] S2: Set the constraints of the high-frequency cutting scheme;

[0008] S3: Set the interval value between rounds;

[0009] S4: Set the extreme expected DC power disturbance, and when all rounds of high-frequency cutting are operated at the same frequency threshold value, the maximum value of the transient frequency is less than f OPC,set , the minimum value of transient frequency is greater than f UFLS,set1 ;

[0010] S5: Assume that the high-frequency cutting scheme has been set before i-1 rounds, and cut off the units P1, P2, ..., P i-1 ;

[0011] S6: By calculating the machine cutting amount in each round, the machine cutting capacity of the high-frequency machine cutting scheme is obtained;

[0012] S7: after determining the total amount of machine cutting at each DC landing point, evenly distribute it to each DC landing point according to the machine cutting amount in each round;

[0013] S8: Check the power flow under DC blocking condition.

[0014] In an optional implementation, in S1, the objective function of the high-frequency cutting scheme is as follows:

[0015]

[0016] Where P i is the cutting amount of the i-th round of high-frequency cutting machine, and n is the setting round of high-frequency cutting machine.

[0017] In an optional implementation, in S2, the constraints include:

[0018] f ∞,min ≤f ∞ ≤f ∞,max (20)

[0019] f max,B ≤f cr,1 ≤f cr1,max (twenty one)

[0020] f min >f UFLS,set1 (twenty two)

[0021] f max ≤f OPC.set and f cr,n <f OPC.set (twenty three)

[0022] f RoCoF <f wind,set (twenty four)

[0023] f cr,i <f set,i <f cr,i+1 (25)

[0024] P i ≤ΔP wind,i +ΔP i (26)

[0025] P line <P max (27)

[0026]

[0027] In the formula, f ∞ represents the steady-state frequency, f ∞,minRepresents the lower limit of steady-state frequency, f ∞,max represents the upper limit of steady-state frequency, f cr,1 is the frequency threshold value of the first round of high-frequency cutting action, f max,B is the maximum frequency deviation of the system when the DC single-pole is locked under the high probability typical operation mode, f cr1,max is the maximum limit of the first round of action frequency threshold, f UFLS,set1 is the frequency threshold value of the first round of low-frequency load shedding, f min is the minimum value of transient frequency deviation of the system, f max is the maximum value of transient frequency deviation of the system, f OPC,set is the turbine overspeed protection frequency setting value, f cr,n is the frequency threshold of the last round of high-frequency cutting scheme, f RoCoF Indicates the rate of change of system frequency, f wind,set Indicates the frequency protection setting of the wind turbine, f cr,i ,f cr,i+1 are the action frequency thresholds of the i-th and i+1-th rounds in the high-frequency machine cutting scheme, respectively, and f set,i is the frequency protection setting value of the i-th round of fan removal, ΔP wind,i is the fan capacity removed in the i-th round, ΔP i is the capacity of conventional units removed in the i-th round, P i is the cutting amount of the high-frequency cutting machine in the i-th round, P line Indicates the active power of the line after DC blocking, P max Line maximum transmission capacity, P ESS Indicates the energy storage capacity configured at the DC sending end.

[0028] In an optional implementation, in S3, the interval value is calculated as follows:

[0029]

[0030] Where Δf cr is the interval between rounds.

[0031] In an optional implementation, in S4, the following formula is satisfied:

[0032] ΔP min,l <ΔP pre,initial,l <ΔP max,l (30)

[0033] ΔP pre,initial,l =0.5×(ΔP min,l +ΔP max,l ) (31)

[0034] ΔP pre,initial =ΣΔP pre,initial,l / m (32)

[0035] In the formula, ΔP min,l , ΔP max,l , ΔP pre,initial,l It is divided into the minimum estimated value, the maximum estimated value and the estimated initial value when taking the lth high-frequency cutting frequency threshold value, m is the number of high-frequency cutting frequency threshold values ​​taken, ΔP pre,initial Estimate initial values ​​for the solution.

[0036] In an optional embodiment, S5 includes:

[0037] When the disturbance is greater than ΔP critical,i When the i-th round of action is triggered, ΔP critical,i is the critical disturbance ΔP of the i-th round of action critical,i .

[0038] In an optional embodiment, S6 includes:

[0039] The cutting capacity is distributed to each DC landing point according to the ratio of DC transmission capacity.

[0040] In an optional embodiment, S7 includes:

[0041] If the amount of cutting at each location cannot be evenly distributed due to unit power limitation, some locations will be selected for cutting according to the cutting capacity;

[0042] After obtaining the cutting amount of each DC point in each round of high-frequency cutting, select the unit at each DC point.

[0043] In an optional embodiment, S8 includes:

[0044] Calculate the sensitivity of the power margin of the inter-regional transmission line after setting the perturbation value at each trip point, that is:

[0045]

[0046] In the formula, a i is the sensitivity, which reflects the impact of the change in energy storage configuration capacity on the line transmission power margin η, η=P max -P line , η i (P ESS (i) ) is the energy storage configuration capacity P ESS (i) The line transmission power margin index at the time of i (P ESS (i) ,τ i ) is to increase the energy storage perturbation τ i The line transmission power margin index obtained later;

[0047] According to the sensitivity a i Solve for η i (P ESS (i+1) )=0 energy storage configuration capacity:

[0048] η i (P ESS (i+1) ) = η i (P ESS (i) )+a i Δp ESS (i+1) (34)

[0049] In the formula, Δp ESS (i+1) For the i+1th time, the solution is required to be η i (P ESS (i+1) )=0 energy storage configuration capacity;

[0050] Solve to get the energy storage configuration capacity P ESS (i+1) :

[0051] P (i+1) =P (i) +Δp (i+1) (35)

[0052] P (i+1) Substitute into the calculation η i (P (i+1) ), and judge η i (P (i+1) ) satisfies the convergence condition:

[0053] η(P (i+1) )<ε (36)

[0054] If the convergence condition is not met, the sensitivity calculation will be repeated until the convergence condition is met.

[0055] The beneficial effects of the multi-source integrated configuration sending-end power grid frequency safety and stability control method provided by the embodiment of the present invention include:

[0056] During the high-frequency cutting process, the units near the DC landing point are cut off first to ensure that the line transmission power is within its limited range and avoid secondary disturbances affecting system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0058] Figure 1 A flow chart of a method for controlling frequency safety and stability of a power grid at the sending end with a multi-source integrated configuration provided by an embodiment of the present invention;

[0059] Figure 2 It is the local 500kV network power flow distribution under JP double-pole blocking and BJ single-pole blocking fault;

[0060] Figure 3 It is the local 500kV network power flow distribution under BJ double-pole blocking and FF single-pole blocking fault;

[0061] Figure 4 This is the local 500kV network power flow distribution under FF double-pole blocking and BJ single-pole blocking faults. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0063] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0065] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0066] For the sending-end power grid, due to the large amount of external active power, DC blocking will cause the power grid frequency to rise rapidly. If the control is not timely at this time, the system will have high-frequency problems. Therefore, in the high-frequency solution, the high-frequency cutting action frequency must be lower than the OPC action frequency to avoid repeated opening and closing of the unit valve and large power oscillations. When DC is blocked, the power flow state and generator power of the sending-end power grid change, and the power of each node of the power grid also changes accordingly, which may cause excessive changes in line power. Therefore, in the high-frequency cutting process, the units near the DC landing point are preferentially cut off to ensure that the line transmission power is within its limited range and avoid secondary disturbances affecting system stability.

[0067] For the sending-end power grid, due to the large amount of active power transmitted, DC blocking will cause the power grid frequency to increase rapidly. If the control is not timely at this time, the system will have high-frequency problems.

[0068] For areas with concentrated wind energy resources, wind energy is delivered in a centralized mode. Since the frequency protection settings of different wind turbines are different, if a unified frequency is adopted to cut off the wind turbines, it may cause large-scale off-grid operation of wind turbines at a certain frequency, and the system will switch from high frequency to low frequency. Therefore, in the high-frequency solution, the high-frequency cutting action frequency must be lower than the OPC action frequency to avoid repeated opening and closing of the unit's steam valve and large power oscillations. When DC is locked, the power flow state of the sending-end power grid and the power of the generator change, and then the power of each node of the power grid also changes accordingly, which may cause excessive changes in line power.

[0069] By reasonably setting the system's expected DC blocking fault, the system's maximum residual power P is set. dist.max , set the high-frequency cutting plan action rounds, the cutting amount in each round, the starting frequency and the selection of cutting units. At the same time, as the integrated configuration of conventional units, new energy and energy storage at the sending-end new energy transmission base becomes the norm, the power transmission of the sending-end power grid is becoming more stable.

[0070] Please refer to Figure 1 This embodiment provides a method for controlling the frequency of a power grid at the sending end with a multi-source integrated configuration for safety and stability (hereinafter referred to as the method). The multi-sources include conventional power sources, new energy sources, energy storage, etc. The method includes the following steps:

[0071] S1: Set a high-frequency cutting plan and solve the cutting amount in each round. The setting target of the high-frequency cutting plan is to minimize the cutting amount and ensure that the power disturbance P caused by the expected DC fault is dist ≤P dist.max .

[0072] Among them, the high-frequency cutting scheme is recorded as S = {P1, P2, ..., P n}, can reliably suppress the frequency of the sending-end system so that the frequency meets the grid operation requirements.

[0073] The high-frequency cutting machine solution consists of n ternary tables: [fcr,1 ,t1,P1],[f cr,2 ,t2,P2],…,[f cr,n ,t n ,P n ], where f cr,n is the action frequency threshold value of the last round (nth round) of the high-frequency cutting scheme, t n is the nth round of high-frequency cutting action time, P n is the cutting amount of the nth round of high-frequency cutting machine.

[0074] The objective function of the high-frequency cutting scheme is as follows:

[0075]

[0076] Where P i is the cutting amount of the i-th round of high-frequency cutting machine, and n is the setting round of high-frequency cutting machine.

[0077] S2: Set the constraints of the high-frequency cutting solution:

[0078] f ∞,min ≤f ∞ ≤f ∞,max (38)

[0079] f max,B ≤f cr,1 ≤f cr1,max (39)

[0080] f min >f UFLS,set1 (40)

[0081] f max ≤f OPC.set and f cr,n <f OPC.set (41)

[0082] f RoCoF <f wind,set (42)

[0083] f cr,i <f set,i <f cr,i+1 (43)

[0084] P i ≤ΔP wind,i +ΔP i (44)

[0085] P line <P max (45)

[0086]

[0087] Formula (38) indicates that the long-term stable operating frequency of the system should be within the allowable range, f ∞ represents the steady-state frequency, f ∞,min Represents the lower limit of steady-state frequency, f ∞,max Represents the upper limit of steady-state frequency.

[0088] In formula (39), f cr,1 is the frequency threshold value of the first round of high-frequency cutting action, f max,B is the maximum frequency deviation of the system when the DC single-pole is locked under the high probability typical operation mode, f cr1,max It is the maximum limit of the first round action frequency threshold.

[0089] In order to coordinate with underfrequency load reduction and OPC protection, the frequency in the dynamic process should satisfy equations (40) and (42), f UFLS,set1 is the frequency threshold value of the first round of low-frequency load shedding, f min is the minimum value of transient frequency deviation of the system, f max is the maximum value of transient frequency deviation of the system, f OPC,set It is the set value of turbine overspeed protection frequency.

[0090] Formula (6) indicates that the system frequency change rate is less than the frequency protection value set by the wind turbine, thereby avoiding large-scale disconnection of wind turbines due to excessive frequency change rate during transient processes. RoCoF Indicates the rate of change of system frequency, f wind,set Indicates the frequency protection setting of the wind turbine.

[0091] In formula (43), f cr,i ,f cr,i+1 are the action frequency thresholds of the i-th and i+1-th rounds in the high-frequency machine cutting scheme, respectively, and f set,i The frequency protection constant for cutting off the fan in the i-th round.

[0092] The amount of machine cutting per round in the high-frequency cutting scheme is shown in formula (44), where ΔP wind,i is the fan capacity removed in the i-th round, ΔP i Cut off the capacity of conventional units for the i-th round.

[0093] Formula (45) is the line power constraint, P line Indicates the active power of the line after DC blocking, P max The maximum transmission capacity of the line.

[0094] Formula (46) represents the energy storage configured to prevent the power overload caused by power surplus in the case of DC blocking, and the inter-regional line overload is prevented by configuring energy storage. ESS Indicates the energy storage capacity configured at the DC sending end.

[0095] S3: Set the interval value between rounds.

[0096] The number of high-frequency machine cutting rounds and the operating frequencies of the first and last rounds are obtained from equations (39) and (42) in the constraints. The frequency threshold of the first high-frequency machine cutting frequency is greater than the maximum frequency deviation of DC single-pole locking under the main operation mode. A certain margin is left for the operating frequency of the last round. The intermediate rounds are taken at equal intervals. The high-frequency machine cutting delay refers to the low-frequency load reduction and is taken as 0.2s.

[0097]

[0098] Where Δf cr is the interval between rounds.

[0099] S4: Set the extreme expected DC power disturbance, and when all rounds of high-frequency cutting are operated at the same frequency threshold value, the maximum value of the transient frequency is less than f OPC,set , the minimum value of transient frequency is greater than f UFLS,set1 .

[0100] ΔP min,l <ΔP pre,initial,l <ΔP max,l (48)

[0101] ΔP pre,initial,l =0.5×(ΔP min,l +ΔP max,l ) (49)

[0102] ΔP pre,initial =ΣΔP pre,initial,l / m (50)

[0103] Where ΔP min,l , ΔP max,l , ΔP pre,initial,l It is divided into the minimum estimated value, the maximum estimated value and the estimated initial value when taking the lth high-frequency cutting frequency threshold value, m is the number of high-frequency cutting frequency threshold values ​​taken, ΔP pre,initial Estimate initial values ​​for the solution.

[0104] S5: Assume that the high-frequency cutting scheme has been set before i-1 rounds, and cut off the units P1, P2, ..., P i-1 .

[0105] According to the i-1th wheel cutting amount and formula (7), the critical disturbance ΔP of the i-th wheel action can be obtained by analysis: critical,i , when the disturbance is greater than ΔP critical,i According to the method for obtaining the i-1th round of machine cutting, adding the expected DC power disturbance can obtain the i-th round of high-frequency machine cutting amount P i There is a critical value P critical,i, and use this critical amount as the reference value for cutting machine quantity.

[0106] S6: By calculating the amount of machine cutting in each round, the cutting capacity of the high-frequency cutting solution is obtained.

[0107] When selecting the cutting units, if the cutting units are concentrated at the same DC proximal end, it may cause large-scale power flow transfer when different DC are locked. Therefore, the cutting capacity is first allocated to each DC point according to the ratio of DC transmission capacity, that is:

[0108]

[0109] P d1 :P d2 :…:P dk =P 1,base :P 2,base :…:P k,base (52)

[0110] Where P dr is the total power of the rth DC point, k is the number of DCs in the system, P k,base Delivers power to the kth DC line during operation.

[0111] S7: After determining the total amount of machine cutting at each DC landing point, distribute it evenly to each DC landing point according to the amount of machine cutting in each round.

[0112] If the shedding capacity of each point cannot be evenly distributed due to unit power limitation, some points are selected for shedding according to the shedding capacity and the equation (16) is satisfied at the same time. After obtaining the shedding capacity of each DC point in each round of high-frequency shedding, it is necessary to select units at each DC point. The electrical distance between power system nodes is defined as the equivalent impedance Z between two points. eq,ij When selecting the unit, take the DC point as the center and sort all the units from small to large according to the electrical distance to obtain the sequence Z, as shown in the following formula:

[0113] Z=[Z eq,1 ,Z eq,2 ,…,Z eq,m ] (53)

[0114] Assume that in the sequence Z (Z eq,j ,Z eq,j+1 ,Z eq,m-1 ,Z eq,m ) is the equivalent impedance between the mth wind turbine and the DC drop point, then the wind turbine shutdown quantity is judged to satisfy the following formula:

[0115] ΔP wind,i ≥P i (54)

[0116] If equation (18) is satisfied, the amount of cutting in the i-th round is ΔPwind,i If not, then select the conventional units according to the order in sequence Z and increase the number of cut-off units in sequence until the constraint condition (448) is satisfied.

[0117] Since the frequency response characteristics of the actual system are more complex, based on the above-solved cutting amount, we first calculate the amount of wind turbines that can be cut off during the i-th round of cutting. i wind,total , if ΔP i wind,total ﹤P i , then the conventional unit cutting capacity ΔP needs to be increased i For the i-th round of high-frequency cutting, the amount of wind turbine that can be cut is ΔP i wind,total =ΔP i-1 wind,total -ΔP wind,i-1 .

[0118] S8: Check the power flow under DC blocking condition.

[0119] In the above steps, after calculating the amount of each round of cutting, it is necessary to check the power flow under the DC blocking condition to avoid overload of the transmission lines between the sending-end power grid areas when the DC blocking condition occurs. The perturbation method is used for analysis here.

[0120] The sensitivity of the power margin of the inter-regional transmission line after setting the perturbation value at each trip point is:

[0121]

[0122] In the formula, a i is the sensitivity, which reflects the impact of the change in energy storage configuration capacity on the line transmission power margin η, η=P max -P line , η i (P ESS (i) ) is the energy storage configuration capacity P ESS (i) The line transmission power margin index at the time of i (P ESS (i) ,τ i ) is to increase the energy storage perturbation τ i The line transmission power margin index is obtained later.

[0123] Then according to the sensitivity a i Solve for η i (P ESS (i+1) )=0 energy storage configuration capacity:

[0124] η i(P ESS (i+1) ) = η i (P ESS (i) )+a i Δp ESS (i+1) (56)

[0125] In the formula, Δp ESS (i+1) For the i+1th time, the solution is required to be η i (P ESS (i+1) )=0, and then solve for the energy storage configuration capacity P ESS (i+1) .

[0126] P (i+1) =P (i) +Δp (i+1) (57)

[0127] P (i+1) Substitute into the calculation η i (P (i+1) ), and judge η i (P (i+1) ) whether it meets the convergence condition:

[0128] η(P (i+1) )<ε (58)

[0129] If the convergence condition is not met, return to equation (55) and repeat the calculation until the convergence condition is met.

[0130] Example

[0131] Take a provincial power grid as an example. The grid has 3 DC transmission lines with a maximum transmission capacity of 21,600MW. Consider the most serious DC blocking fault, which is 1 DC bipolar blocking and 1 DC unipolar blocking. Analyze the changes in the active power flow of the AC interconnection line between 500kV substations in the regional power grid under the most serious DC blocking fault, and formulate a high-frequency cutting unit configuration plan. The constraints are as follows:

[0132] f ∞,min =49.8Hz

[0133] f ∞,max =50.2Hz

[0134] f max,B =50.5Hz

[0135] f UFLS,set1 =49.25Hz

[0136] fOPC.set =51.5Hz

[0137] f wind,set =0.5Hz

[0138] Figure 2 to Figure 4 Figure 2 shows the power flow changes of the 500kV network AC interconnection line under fault conditions. The solid arrows represent the power flow distribution of the network before the fault occurs, and the dotted arrows represent the power flow distribution of the network after the fault occurs. The power flow in the figure is normalized to 100MW as the reference value.

[0139] The high-frequency cutting scheme determined according to the proposed method is shown in Table 1 below, and the UHV DC locking combined fault is checked. Considering that the capacity of the units in the actual power grid cannot fully match the cutting amount in the scheme, the cutting amount in the scheme is adjusted in combination with the situation of the wind turbines. Considering that the power grid has no thermal power startup and wind power and photovoltaic grid connection in the extremely small wind operation mode, a hydropower unit is added in the third round of cutting. In the strong wind mode, the wind power grid connection increases, so the new energy units removed in the second round of cutting are increased. The adjusted cutting amount in each round is: 2220MW, 1999MW (add 600MW hydropower in the extremely small mode or 250MW wind power in the strong wind mode), 2170MW, 1570MW, 1570MW. The energy storage capacity configured in each round is: 80MW, 120MW, 150MW, 180MW, 210MW.

[0140] Table 1 High frequency cutting machine solution

[0141]

[0142] In the extremely low wind mode, under the faults of BJ DC bipolar blocking and SJ DC unipolar blocking, the power grid high-frequency cutting action was performed 5 times, a total of 9.5GW units were cut off, the maximum frequency of the power grid increased to 51.51Hz, and the recovery frequency was 50.13Hz. Since there is no thermal power startup in the system under this operation mode and the frequency tolerance capacity of the turbine units is much higher than 51.5Hz, the power grid meets the frequency requirements. In the flat wind mode, the power grid high-frequency cutting action was performed 3 times, a total of 6.98GW units were cut off, the maximum frequency of the power grid increased to 51.14Hz, and the recovery frequency was 50.133Hz. Since the grid-connected capacity of new energy is different under different operation modes, the actual total amount of high-frequency cutting is different from the established plan, but it meets the frequency operation requirements of the power grid.

[0143] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid, characterized in that: The method comprises: S1: Set a high-frequency cutting plan and solve the cutting amount in each round. The setting target of the high-frequency cutting plan is to minimize the cutting amount and ensure that the power disturbance P caused by the expected DC fault is dist ≤P dist.max , P dist.max is the maximum remaining power of the system; S2: Set the constraints of the high-frequency cutting scheme; S3: Set the interval value between rounds; S4: Set the extreme expected DC power disturbance, and when all rounds of high-frequency cutting are operated at the same frequency threshold value, the maximum value of the transient frequency is less than f OPC,set , the minimum value of transient frequency is greater than f UFLS,set1 ; S5: Assume that the high-frequency cutting scheme has been set before i-1 rounds, and cut off the units P1, P2, ..., P i-1 ; S6: By calculating the machine cutting amount in each round, the machine cutting capacity of the high-frequency machine cutting scheme is obtained; S7: after determining the total amount of machine cutting at each DC landing point, evenly distribute it to each DC landing point according to the machine cutting amount in each round; S8: Check the power flow under DC blocking condition.

2. The method for controlling the frequency security and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that: In S1, the objective function of the high-frequency cutting scheme is as follows: Where P i is the cutting amount of the i-th round of high-frequency cutting machine, and n is the setting round of high-frequency cutting machine.

3. The method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that: In S2, the constraints include: f ∞,min ≤f ∞ ≤f ∞,max (2) f max,B ≤f cr,1 ≤f cr1,max (3) f min >f UFLS,set1 (4) f max ≤f OPC.set and f cr,n <f OPC.set (5) f RoCoF <f wind,set (6) f cr,i <f set,i <f cr,i+1 (7) P i ≤ΔP wind,i +ΔP i (8) P line <P max (9) In the formula, f ∞ represents the steady-state frequency, f ∞,min Represents the lower limit of steady-state frequency, f ∞,max represents the upper limit of steady-state frequency, f cr,1 is the frequency threshold value of the first round of high-frequency cutting action, f max,B is the maximum frequency deviation of the system when the DC single-pole is locked in the typical operation mode, f cr1,max is the maximum limit of the first round of action frequency threshold, f UFLS,set1 is the frequency threshold value of the first round of low-frequency load shedding, f min is the minimum value of transient frequency deviation of the system, f max is the maximum value of transient frequency deviation of the system, f OPC,set is the turbine overspeed protection frequency setting value, f cr,n is the frequency threshold of the last round of high-frequency cutting scheme, f RoCoF Indicates the rate of change of system frequency, f wind,set Indicates the frequency protection setting of the wind turbine, f cr,i ,f cr,i+1 are the action frequency thresholds of the i-th and i+1-th rounds in the high-frequency machine cutting scheme, respectively, and f set,i is the frequency protection setting value of the i-th round of fan removal, ΔP wind,i is the fan capacity removed in the i-th round, ΔP i is the capacity of conventional units removed in the i-th round, P i is the cutting amount of the high-frequency cutting machine in the i-th round, P line Indicates the active power of the line after DC blocking, P max Line maximum transmission capacity, P ESS Indicates the energy storage capacity configured at the DC sending end.

4. The method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid according to claim 3 is characterized in that: In S3, the interval value is calculated as: Where Δf cr is the interval between rounds.

5. The method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that: In S4, the following formula is satisfied: ΔP min,l <ΔP pre,initial,l <ΔP max,l (12) ΔP pre,initial,l =0.5×(ΔP min,l +ΔP max,l ) (13) ΔP pre,initial =∑ΔP pre,initial,l / m (14) Where ΔP min,l , ΔP max,l , ΔP pre,initial,l It is divided into the minimum estimated value, the maximum estimated value and the estimated initial value when taking the lth high-frequency cutting frequency threshold value, m is the number of high-frequency cutting frequency threshold values ​​taken, ΔP pre,initial Estimate initial values ​​for the solution.

6. The method for controlling the frequency security and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that S5 include: When the disturbance is greater than ΔP critical,i When the i-th round of action is triggered, ΔP critical,i is the critical disturbance ΔP of the i-th round of action critical,i .

7. The method for controlling the frequency security and stability of a multi-source integrated configuration sending-end power grid according to claim 1, characterized in that S6 include: The cutting capacity is distributed to each DC landing point according to the ratio of DC transmission capacity.

8. The method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that: S7 includes: If the amount of cutting at each location cannot be evenly distributed due to unit power limitation, some locations will be selected for cutting according to the cutting capacity; After obtaining the cutting amount of each DC point in each round of high-frequency cutting, select the unit at each DC point.

9. The method for controlling the frequency safety and stability of a multi-source integrated configuration sending-end power grid according to claim 1 is characterized in that: S8 includes: Calculate the sensitivity of the power margin of the inter-regional transmission line after setting the perturbation value at each trip point, that is: In the formula, a i is the sensitivity, which reflects the impact of the change in energy storage configuration capacity on the line transmission power margin η, η=P max -P line , η i (P ESS (i) ) is the energy storage configuration capacity P ESS (i) The line transmission power margin index at the time of i (P ESS (i) ,τ i ) is to increase the energy storage perturbation τ i The line transmission power margin index obtained later; According to the sensitivity a i Solve for η i (P ESS (i+1) )=0 energy storage configuration capacity: or i (P ESS (i+1) )=η i (P ESS (i) )+a i Δp ESS (i+1) (16) In the formula, Δp ESS (i+1) For the i+1th time, the solution is required to be η i (P ESS (i+1) )=0 energy storage configuration capacity; Solve to get the energy storage configuration capacity P ESS (i+1) : P (i+1) =P (i) +Δp (i+1) (17) P (i+1) Substitute into the calculation η i (P (i+1) ), and judge η i (P (i+1) ) satisfies the convergence condition: the(P (i+1) )<e (18) If the convergence condition is not met, the sensitivity calculation will be repeated until the convergence condition is met.

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