New energy minimum inertia demand calculation method and system for power system

Abstract

The invention discloses a new energy minimum inertia demand calculation method for a power system. The method comprises the following steps: acquiring data information of a target power system; performing equivalence on a speed regulator and a prime mover model of each generator set in the target power system; constructing a new energy minimum inertia demand mathematical model considering the lowest frequency point of the target power system; and calculating the minimum inertia demand value of the new energy of the target power system based on the constructed mathematical model. The invention also discloses a system for realizing the new energy minimum inertia demand calculation method for the power system. According to the method, through system equivalence and model construction, calculation of the minimum inertia demand of the new energy of the power system is achieved, the optimization problem can be conveniently embedded and implemented, and the method is high in reliability, good in accuracy, convenient to apply and high in efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a method and system for calculating the minimum inertia requirement of new energy for an electric power system. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring the stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] At present, environmental problems are becoming more and more serious, so more and more new energy power generation systems are beginning to be connected to the power grid and generate electricity. At the same time, with the retirement of thermal power units and other reasons, the proportion of conventional thermal power generating units in the power system is declining year by year; this will lead to a decrease in the equivalent inertia constant of the power system, which will greatly affect the safe and stable operation of the power system. The stable operation of the power system requires the determination of the equivalent inertia of the synchronous unit and the new energy unit, and based on this, the frequency safety of the low inertia system is guaranteed.

[0004] At present, the traditional calculation scheme for the minimum inertia requirement of new energy in the power system generally adopts a trial-and-error scheme based on time domain simulation. Although this scheme can obtain relatively good evaluation results, it cannot be integrated into the optimization problem for modeling and solving; this makes the existing calculation scheme for the minimum inertia requirement of new energy in the power system extremely inconvenient to apply and has poor efficiency. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for calculating the minimum inertia requirement of new energy for a power system, which has high reliability, good accuracy, convenient application and high efficiency.

[0006] A second objective of the present invention is to provide a system for implementing the method for calculating the minimum inertia requirement of new energy for the power system.

[0007] The method for calculating the minimum inertia requirement of new energy for a power system provided by the present invention comprises the following steps:

[0008] S1. Obtain data information of the target power system;

[0009] S2. Based on the data information obtained in step S1, the governor and prime mover models of each generator set in the target power system are equivalent based on the first-order inertial joint;

[0010] S3. Based on the simplified model, a mathematical model of the minimum inertia demand of new energy sources considering the lowest frequency point of the target power system is constructed;

[0011] S4. Based on the mathematical model constructed in step S2 and step S3, the minimum inertia demand value of new energy of the target power system is calculated.

[0012] The step S1 of acquiring the data information of the target power system specifically includes the following steps:

[0013] Acquire data information of the target power system; the data information includes frequency regulation parameters of synchronous generators in the target power system, and frequency regulation parameters of new energy units in the target power system and corresponding value ranges.

[0014] According to the data information obtained in step S1, step S2 performs equivalence on the governor and prime mover models of each generator set in the target power system based on the first-order inertial joint, which specifically includes the following steps:

[0015] The complete frequency domain model of the speed governor and prime mover is expressed as

[0016]

[0017] Where ΔP G (s) is the frequency domain expression of the active power variation of the unit; K m is the ratio of the capacity of the mth unit to the capacity of all units; F H is the power ratio of the high pressure cylinder; T R is the speed regulator constant; R is the regulation rate; s is the Laplace operator; Δf(s) is the frequency domain expression of the frequency change;

[0018] The simplified frequency domain model of the speed governor and prime mover is expressed as

[0019]

[0020] Where k is the first equivalent parameter; T is the second equivalent parameter;

[0021] Assume Δf as the step response, Substituting Δf(s) into the full frequency domain model and simplified frequency domain model of the speed governor and prime mover, we get

[0022]

[0023]

[0024] For the full frequency domain model, the transformation is

[0025]

[0026] Then the time domain model is converted into

[0027]

[0028] For the simplified frequency domain model, the conversion is

[0029]

[0030] Then the time domain model is converted into

[0031]

[0032] Finally, the least squares method is used to fit the first-order inertia link with the speed regulator and prime mover model of the synchronous unit. The response type is unit step response, and the response curve time length is 5 seconds.

[0033] The step S3, based on the simplified model, constructs a mathematical model of the minimum inertia demand of new energy considering the lowest frequency point of the target power system, which specifically includes the following steps:

[0034] Set the governor and prime mover to the active power disturbance Δp L After that, the output power remains stable, and the corresponding frequency deviation calculation formula is:

[0035]

[0036] Where Δf is the system frequency deviation; H e is the system equivalent inertia time constant; t is time; -m Δω is the frequency deviation derivative;

[0037] Speed ​​governor output Δp Gi (t) is

[0038]

[0039] Where K i is the equivalent droop coefficient of the i-th unit, and k i is the inverse of the adjustment rate of the i-th unit, S Bi is the installed capacity of the i-th unit, S B is the total installed capacity of all units in the system; T i is the equivalent time constant of the i-th unit;

[0040] The speed regulator output Δp Gi (t) is approximated by the following formula:

[0041] Δp Gi (t)≈C i ·m Δω ·t

[0042] Where C i is the set constant, and 0<C i <k i ;

[0043] The speed regulator output Δp Gi Combining the two equations of (t), we get

[0044]

[0045] Then we get the setting constant C i The expression is

[0046]

[0047] Where t min is the time of the frequency extreme point;

[0048] The mathematical expression of the system frequency deviation is:

[0049]

[0050] Where H e is the system equivalent inertia time constant; N is the number of all units participating in frequency regulation in the system;

[0051] Integrate and solve the mathematical expression of the system frequency deviation to obtain

[0052]

[0053] Where Δp L is the active disturbance;

[0054] The maximum frequency deviation point time solution formula is:

[0055]

[0056] Substitute it into the frequency deviation calculation formula to obtain the maximum frequency deviation point time t min for

[0057]

[0058] Thus, the maximum frequency deviation point Δf is obtained min The expression is

[0059]

[0060] Where f B is the system reference frequency;

[0061] Finally, the mathematical model of the minimum inertia requirement of the system considering the maximum frequency deviation point is obtained:

[0062]

[0063]

[0064] In the formula The first expression of the minimum inertia to meet the maximum frequency deviation of the system (unit: s); Δf ref is the reference value of the system frequency change rate; The second representation of the minimum inertia to meet the maximum frequency deviation of the system (unit: MW·s); P B It is the sum of the active capacity of all units in the system.

[0065] The mathematical model constructed based on step S2 and step S3 in step S4 is used to calculate the minimum inertia requirement value of the target power system, which specifically includes the following steps:

[0066] The following formula is used as the mathematical model of the minimum inertia requirement of the system considering the frequency change rate:

[0067]

[0068] In the formula RoCoF is the minimum inertia requirement of the system considering the frequency change rate; ref is the reference value of the system frequency change rate;

[0069] Finally, the minimum inertia requirement value of new energy is calculated using the following formula:

[0070]

[0071] Where I SG The inertia provided for the synchronous units in the system.

[0072] The present invention also provides a system for implementing the method for calculating the minimum inertia demand of new energy for an electric power system, comprising a data acquisition module, a model equivalent module, a model construction module and a demand calculation module; the data acquisition module, the model equivalent module, the model construction module and the demand calculation module are connected in series in sequence; the data acquisition module is used to acquire data information of a target electric power system, and upload the data information to the model equivalent module; the model equivalent module is used to perform equivalent operation on the governor and prime mover models of each generator set in the target electric power system based on a first-order inertia joint according to the received data information, and upload the data information to the model construction module; the model construction module is used to construct a mathematical model of the minimum inertia demand of new energy for the target electric power system considering the lowest frequency point based on the received data information and based on a simplified model, and upload the data information to the demand calculation module; the demand calculation module is used to calculate the minimum inertia demand value of new energy for the target electric power system based on the constructed mathematical model according to the received data information.

[0073] The method and system for calculating the minimum inertia requirement of new energy for the power system provided by the present invention not only realizes the calculation of the minimum inertia requirement of new energy for the power system through system equivalence and model construction, but also the scheme of the present invention can be more conveniently embedded in the optimization problem and implemented, with high reliability, good accuracy, easy application and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 The figure is a schematic diagram of the method flow of the present invention.

[0075] Figure 2 It is a schematic diagram of the equivalent frequency model in the method of the present invention.

[0076] Figure 3 It is a schematic diagram of a simplified equivalent frequency model in the method of the present invention.

[0077] Figure 4 It is a schematic diagram of a simplified equivalent frequency model of multiple units in the method of the present invention.

[0078] Figure 5 Schematic diagram of inertia calculation results of an embodiment of the method of the present invention.

[0079] Figure 6 Schematic diagram of frequency deviation comparison of an embodiment of the method of the present invention.

[0080] Figure 7 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0081] like Figure 1 The method flow chart of the method of the present invention is shown as follows: The method for calculating the minimum inertia requirement of new energy for the power system disclosed in the present invention comprises the following steps:

[0082] S1. Acquire data information of the target power system; specifically includes the following steps:

[0083] Acquire data information of the target power system; the data information includes frequency regulation parameters of synchronous generators in the target power system, and frequency regulation parameters of new energy units in the target power system and corresponding value ranges;

[0084] S2. Based on the data information obtained in step S1, the governor and prime mover models of each generator set in the target power system are equivalent based on the first-order inertial joint; specifically, the steps include:

[0085] Figure 2 In the frequency domain, the complete frequency domain model of the speed governor and prime mover is expressed as

[0086]

[0087] Where ΔP G (s) is the frequency domain expression of the active power variation of the unit; K m is the ratio of the capacity of the mth unit to the capacity of all units; F H is the power ratio of the high pressure cylinder; T R is the speed regulator constant; R is the regulation rate; s is the Laplace operator; Δf(s) is the frequency domain expression of the frequency change;

[0088] Figure 3 In the frequency domain, the simplified model of the speed governor and prime mover is expressed as

[0089]

[0090] Where k is the first equivalent parameter; T is the second equivalent parameter;

[0091] Assume Δf as the step response, Substituting Δf(s) into the full frequency domain model and simplified frequency domain model of the speed governor and prime mover, we get

[0092]

[0093]

[0094] against Figure 2 The corresponding complete frequency domain model is converted into

[0095]

[0096] Then the time domain model is converted into

[0097]

[0098] against Figure 3 The corresponding simplified frequency domain model is converted into

[0099]

[0100] Then the time domain model is converted into

[0101]

[0102] Finally, the least square method is used to fit the first-order inertia link with the speed governor and prime mover model of the synchronous unit. The response type is unit step response, and the response curve time length is 5 seconds.

[0103] S3. Based on the simplified model, a mathematical model of the minimum inertia demand of new energy sources considering the lowest frequency point of the target power system is constructed; specifically, the following steps are included:

[0104] Set the governor and prime mover to the active power disturbance ΔpL After that, the output power remains stable, and the corresponding frequency deviation calculation formula is:

[0105]

[0106] Where Δf is the system frequency deviation; H e is the system equivalent inertia time constant; t is time; -m Δω is the frequency deviation derivative;

[0107] Figure 4 In the case of speed regulator output Δp Gi (t) is

[0108]

[0109] Where K i is the equivalent droop coefficient of the i-th unit, and k i is the inverse of the adjustment rate of the i-th unit, S Bi is the installed capacity of the i-th unit, S B is the total installed capacity of all units in the system; T i is the equivalent time constant of the i-th unit;

[0110] The speed regulator output Δp Gi (t) is approximated by the following formula:

[0111] Δp Gi (t)≈C i ·m Δω ·t

[0112] Where C i is the set constant, and 0<C i <k i ;

[0113] The speed regulator output Δp Gi Combining the two equations of (t), we get

[0114]

[0115] Then we get the setting constant C i The expression is

[0116]

[0117] Where t min is the time of the frequency extreme point;

[0118] Combination Figure 4 , the mathematical expression of the system frequency deviation is

[0119]

[0120] Where H e is the system equivalent inertia time constant; N is the number of all units participating in frequency regulation in the system;

[0121] Integrate and solve the mathematical expression of the system frequency deviation to obtain

[0122]

[0123] Where Δp L is the active disturbance;

[0124] The maximum frequency deviation point time solution formula is:

[0125]

[0126] Substitute it into the frequency deviation calculation formula to obtain the maximum frequency deviation point time t min for

[0127]

[0128] Thus, the maximum frequency deviation point Δf is obtained min The expression is

[0129]

[0130] Where f B is the system reference frequency;

[0131] Finally, the mathematical model of the minimum inertia requirement of the system considering the maximum frequency deviation point is obtained:

[0132]

[0133]

[0134] In the formula The first representation of the minimum inertia to satisfy the maximum frequency deviation constraint of the system (in s); Δf ref is the reference value of the system frequency change rate; The second representation of the minimum inertia that satisfies the maximum frequency deviation constraint of the system (unit: MW·s); P B It is the sum of active capacity of all units in the system;

[0135] S4. Based on the mathematical model constructed in step S2 and step S3, the minimum inertia requirement value of new energy for the target power system is calculated; specifically, the steps include:

[0136] The following formula is used as the mathematical model of the minimum inertia requirement of the system considering the frequency change rate:

[0137]

[0138] In the formula RoCoF is the minimum inertia requirement of the system considering the frequency change rate; ref is the reference value of the system frequency change rate;

[0139] Finally, the minimum inertia requirement value of new energy is calculated using the following formula:

[0140]

[0141] Where I SG The inertia provided for the synchronous units in the system.

[0142] The method of the present invention is further described below in conjunction with an embodiment:

[0143] The scheme of the present invention is verified by using an improved IEEE39 node system;

[0144] Table 1 is a schematic table of relevant parameters of the system in an embodiment of the present invention:

[0145] Table 1 Schematic diagram of system related parameters

[0146] Unit No. Rated active capacity / MW K Inertia constant / s 1 1000 25 4.8 2 595 20 5.0 3 680 22 5.0 4 680 22 5.4 5 510 20 5.0 6 680 22 5.6 7 595 20 5.7 8 595 20 4.7 9 850 25 3.8 10 850 25 4.5 load / 1 /

[0147] A 500MW new energy unit is added to nodes 3, 4 and 22 respectively, and a random disturbance is set at each time node with a 12h evaluation period. The traditional method for setting the virtual inertia parameters of the wind turbine unit is usually to set fixed parameters within a certain period. In contrast, the evaluation results obtained by the present invention are used to set the parameters at each time node. Figure 5 The calculation results of the minimum inertia requirement of the new energy using the present invention are given. Figure 6 The system frequency extreme value after setting the virtual inertia parameters by the traditional method and the calculation method based on the present invention. Figure 5 It can be seen that the maximum frequency deviation of the system exceeds the limit in most time periods when the parameters are set based on the traditional method, while the maximum frequency deviation of the system does not exceed the limit after the parameters are set according to the calculation results of the present invention, which shows that the results of the present invention are more accurate.

[0148] like Figure 7The above is a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for realizing the method for calculating the minimum inertia demand of new energy for the power system comprises a data acquisition module, a model equivalent module, a model construction module and a demand calculation module; the data acquisition module, the model equivalent module, the model construction module and the demand calculation module are connected in series in sequence; the data acquisition module is used to acquire data information of the target power system, and upload the data information to the model equivalent module; the model equivalent module is used to perform equivalent operation on the governor and prime mover models of each generator set in the target power system based on the first-order inertia joint according to the received data information, and upload the data information to the model construction module; the model construction module is used to construct a mathematical model of the minimum inertia demand of new energy considering the lowest frequency point of the target power system based on the received data information and the simplified model, and upload the data information to the demand calculation module; the demand calculation module is used to calculate the minimum inertia demand value of new energy for the target power system based on the constructed mathematical model according to the received data information.

Claims

1. A method for calculating the minimum inertia requirement of new energy for a power system, comprising the following steps: S1. Obtain data information of the target power system; S2. Based on the data information obtained in step S1, the governor and prime mover models of each generator set in the target power system are equivalent based on the first-order inertial joint; S3. Based on the simplified model, a mathematical model of the minimum inertia demand of new energy sources considering the lowest frequency point of the target power system is constructed; S4. Based on the mathematical model constructed in step S2 and step S3, the minimum inertia demand value of new energy of the target power system is calculated.

2. The method for calculating the minimum inertia requirement of new energy for the power system according to claim 1 is characterized in that The step S1 of acquiring the data information of the target power system specifically includes the following steps: Acquire data information of the target power system; the data information includes frequency regulation parameters of synchronous generators in the target power system, and frequency regulation parameters of new energy units in the target power system and corresponding value ranges.

3. The method for calculating the minimum inertia requirement of new energy for the power system according to claim 2 is characterized in that According to the data information obtained in step S1, step S2 performs equivalence on the governor and prime mover models of each generator set in the target power system based on the first-order inertial joint, which specifically includes the following steps: The complete frequency domain model of the speed governor and prime mover is expressed as Where ΔP G (s) is the frequency domain expression of the active power variation of the unit; K m is the ratio of the capacity of the mth unit to the capacity of all units; F H is the power ratio of the high pressure cylinder; T R is the speed regulator constant; R is the regulation rate; s is the Laplace operator; Δf(s) is the frequency domain expression of the frequency change; The simplified frequency domain model of the speed governor and prime mover is expressed as Where k is the first equivalent parameter; T is the second equivalent parameter; Assume Δf as the step response, Substituting Δf(s) into the full frequency domain model and simplified frequency domain model of the speed governor and prime mover, we get For the full frequency domain model, the transformation is Then the time domain model is converted into For the simplified frequency domain model, the conversion is Then the time domain model is converted into Finally, the least squares method is used to fit the first-order inertia link with the speed regulator and prime mover model of the synchronous unit. The response type is unit step response, and the response curve time length is 5 seconds.

4. The method for calculating the minimum inertia requirement of new energy for the power system according to claim 3 is characterized in that The step S3, based on the simplified model, constructs a mathematical model of the minimum inertia demand of new energy considering the lowest frequency point of the target power system, which specifically includes the following steps: Set the governor and prime mover to the active power disturbance Δp L After that, the output power remains stable, and the corresponding frequency deviation calculation formula is: Where Δf is the system frequency deviation; H e is the system equivalent inertia time constant; t is time; -m Δω is the frequency deviation derivative; Speed ​​governor output Δp Gi (t) is Where K i is the equivalent droop coefficient of the i-th unit, and k i is the inverse of the adjustment rate of the i-th unit, S Bi is the installed capacity of the i-th unit, S B is the total installed capacity of all units in the system; T i is the equivalent time constant of the i-th unit; The speed regulator output Δp Gi (t) is approximated by the following formula: Δp Gi (t)≈C i ·m Δω ·t Where C i is the set constant, and 0<C i <k i ; The speed regulator output Δp Gi Combining the two equations of (t), we get Then we get the setting constant C i The expression is Where t min is the time of the frequency extreme point; The mathematical expression of the system frequency deviation is: Where H e is the system equivalent inertia time constant; N is the number of all units participating in frequency regulation in the system; Integrate and solve the mathematical expression of the system frequency deviation to obtain Where Δp L is the active disturbance; The maximum frequency deviation point time solution formula is: Substitute it into the frequency deviation calculation formula to obtain the maximum frequency deviation point time t min for Thus, the maximum frequency deviation point Δf is obtained min The expression is Where f B is the system reference frequency; Finally, the mathematical model of the minimum inertia requirement of the system considering the maximum frequency deviation point is obtained: In the formula The first representation of the minimum inertia that satisfies the maximum frequency deviation constraint of the system; Δf ref is the reference value of the system frequency change rate; The second representation of the minimum inertia that satisfies the maximum frequency deviation constraint of the system; P B It is the sum of the active capacity of all units in the system.

5. The method for calculating the minimum inertia requirement of new energy for the power system according to claim 4, characterized in that The mathematical model constructed based on step S2 and step S3 in step S4 is used to calculate the minimum inertia requirement value of the new energy of the target power system, which specifically includes the following steps: The following formula is used as the mathematical model of the minimum inertia requirement of the system considering the frequency change rate: In the formula RoCoF is the minimum inertia requirement of the system considering the frequency change rate; ref is the reference value of the system frequency change rate; Finally, the minimum inertia requirement value of new energy is calculated using the following formula: Where I SG The inertia provided for the synchronous units in the system.

6. A system for implementing the method for calculating the minimum inertia requirement of new energy for a power system according to any one of claims 1 to 5, characterized in that It includes a data acquisition module, a model equivalent module, a model construction module and a demand calculation module; the data acquisition module, the model equivalent module, the model construction module and the demand calculation module are connected in series in sequence; the data acquisition module is used to acquire data information of the target power system and upload the data information to the model equivalent module; the model equivalent module is used to perform equivalent operation on the governor and prime mover models of each generator set in the target power system based on the first-order inertia joint according to the received data information, and upload the data information to the model construction module; The model construction module is used to construct a mathematical model of the minimum inertia demand of new energy for the target power system considering the lowest frequency point based on the received data information and a simplified model, and upload the data information to the demand calculation module; the demand calculation module is used to calculate the minimum inertia demand value of new energy for the target power system based on the constructed mathematical model according to the received data information.

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