阅读说明：本技术 一种考虑光伏发电机故障穿越特性的负荷模型构建方法 (Load model construction method considering fault ride-through characteristic of photovoltaic generator ) 是由 王�琦 潘晓杰 赵兵 徐友平 肖昌育 党杰 邵德军 骆攀登 郝杰 程势高 贾琦 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种考虑光伏发电机故障穿越特性的负荷模型构建方法,并公开了该方法在计算时所使用的负荷模型与其中的参数计算方法,其中负荷模型的构建方法,包括收集获取网络拓扑数据、分布式光伏发电系统数据、变电站负荷设备构成数据、负荷设备特性数据,然后依据上述收集的数据,分别计算出配电网络等值阻抗、考虑故障穿越特性的等值光伏发电机参数、不考虑故障穿越特性的等值光伏发电机参数、静态负荷模型参数、动态负荷模型参数,依据上述数据得到一般形式的负荷模型,最后输出该负荷模型中的数据。(The invention discloses a load model construction method considering the fault ride-through characteristic of a photovoltaic generator, and discloses a load model used in the method during calculation and a parameter calculation method thereof, wherein the load model construction method comprises the steps of collecting and acquiring network topology data, distributed photovoltaic power generation system data, substation load equipment composition data and load equipment characteristic data, respectively calculating equivalent impedance of a power distribution network, equivalent photovoltaic generator parameters considering the fault ride-through characteristic, equivalent photovoltaic generator parameters not considering the fault ride-through characteristic, static load model parameters and dynamic load model parameters according to the collected data, obtaining a load model in a general form according to the data, and finally outputting the data in the load model.)

1. A load model construction method considering the fault ride-through characteristic of a photovoltaic generator is characterized by comprising the following steps:

acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment physical mechanism characteristic data;

calculating equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation;

calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic;

according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride-through characteristic, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride-through characteristic;

calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

according to the physical mechanism characteristics of the induction motor, all motors in the power distribution and supply area of the transformer substation are equivalent to a single-machine equivalent model, and the electrical parameters of the motors are calculated;

and calculating reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance.

2. The method for constructing a load model considering the fault-ride-through characteristics of photovoltaic generators as claimed in claim 1, wherein the load model is obtained by adding an equivalent photovoltaic generator considering the fault-ride-through characteristics and an equivalent photovoltaic generator not considering the fault-ride-through characteristics to a virtual bus of a comprehensive load model considering the power distribution network.

3. The method for constructing a load model considering the fault-ride through characteristics of a photovoltaic generator according to claim 1, wherein the step of calculating the static load equivalent parameters of the power supply and distribution area of the load site based on the power load data of the power supply and distribution area of the load site further comprises:

establishing a polynomial load model;

calculating the total stator winding copper loss ∑ P_cu1Rated slip S of equivalent motor_nAnd an equivalent inertia time constant H;

stator resistance R for calculating equivalent motor model_SStator leakage reactance X_SRotor resistance R_rRotor leakage reactance X_rAnd an excitation reactance X_m。

4. The method for building the load model considering the fault ride-through characteristic of the photovoltaic generator according to claim 1, wherein the step of calculating the reactive compensation of the distribution and supply area of the substation according to the reactive power balance specifically comprises:

acquiring the reactive power output of the photovoltaic motor considering the fault ride-through characteristic;

obtaining the reactive power output of the photovoltaic motor without considering the fault ride-through characteristic;

and calculating reactive compensation of the distribution and power supply area of the high-voltage transformer substation.

5. The method for constructing the load model considering the fault ride-through characteristic of the photovoltaic generator according to claim 1, wherein the step of calculating the equivalent impedance of the distribution network including the load sites of the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the substation specifically comprises:

wherein Z is_DRepresenting the equivalent impedance of the distribution network; p_hRepresenting the active power, Q, of the distribution line or of the transformer's feeder terminal_hIndicating reactive power, U, of distribution line or transformer h-terminal_hIndicating the bus voltage, Z, of the feeder terminal of the line or transformer_hRepresenting the impedance of the distribution line or transformer h, I_L,kRepresenting the kth load branch current, I_PV1,iRepresenting the output current of a photovoltaic generator I taking into account the low voltage ride through characteristic, I_PV2,jThe output current of the photovoltaic generator j without considering the low voltage ride through characteristic is shown, f is the number of distribution lines or transformer buses, l is the number of load branches, m is the number of distributed photovoltaic generators considering the low voltage ride through characteristic, and n is the number of distributed photovoltaic generators not considering the low voltage ride through characteristic.

6. The method for constructing the load model considering the fault ride-through characteristic of the photovoltaic generator according to claim 1, wherein the step of calculating the equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic specifically comprises:

obtaining and summing the active power output of each photovoltaic generator:

m is the number of photovoltaic generators considering the fault ride-through characteristic and contained below the high-voltage load node, P_PV1,iFor the active power output, P, of the respective photovoltaic generator i (i ═ 1, … …, m)_PV1The sum of the actual active power output of all the photovoltaic generators considering the fault ride-through characteristic;

calculating the percentage N of the active output of each photovoltaic generator considering the fault ride-through characteristics to the active output of all photovoltaic generators considering the fault ride-through characteristics under the power supply and distribution area where the voltage load nodes are located_1,i：

N_1，i＝P_PV1，i/P_PV1 i＝1,...,m；

Calculating control parameters of the equivalent distributed photovoltaic generator considering the fault ride-through characteristic, and adopting the active power output PPV1 of each distributed photovoltaic generator considering the fault ride-through characteristic, wherein i accounts for the percentage N1 of the sum PPV1 of the active power outputs of the distributed photovoltaic generators considering the fault ride-through characteristic, and i is a weighting factor to be synthesized:

in the formula, K_PV1，iFor preset control parameters, K, of the distributed photovoltaic generator i taking into account the fault-ride-through behaviour_PV1The parameter values are aggregated for a model of an equivalent distributed photovoltaic generator that takes into account fault ride-through characteristics.

7. The method for constructing the load model considering the fault ride-through characteristic of the photovoltaic generator according to claim 1, wherein the step of calculating equivalent distributed photovoltaic power generation system model parameters not considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system not considering the fault ride-through characteristic specifically comprises:

and taking n as the number of the photovoltaic generators which are contained under the high-voltage load node and do not consider the fault ride-through characteristic, and obtaining the active power P of each photovoltaic generator j (i is 1, … …, n)_PV2,jAnd the actual active output P of all photovoltaic generators without considering the fault ride-through characteristic below the high-voltage load node_PV2The sum of the active power output of n photovoltaic generators without considering the fault ride-through characteristic is as follows:

an active power P of each photovoltaic generator j (j ═ 1.. multidot.n) without consideration of fault ride-through characteristics_PV2,jPercentage N of active output of all photovoltaic generators without considering fault ride-through characteristics under power distribution area where high-voltage load nodes are located_2,jComprises the following steps:

N_2，j＝P_PV2,j/P_PV2 j＝1,...,n

the control parameters of the equivalent distributed photovoltaic generator without considering the fault ride-through characteristic adopt the active output P of each distributed photovoltaic generator without considering the fault ride-through characteristic_PV2,jThe sum P of the active power output of the distributed photovoltaic generator without considering the fault ride-through characteristic_PV2Percentage of (N)_2,jFor the integration of the weighting factors, the calculation formula is as follows:

in the formula, K_PV2，jFor preset control parameters, K, of the distributed photovoltaic generator j without taking into account the fault-ride-through characteristics_PV2And aggregating parameter values for the equivalent distributed photovoltaic generator model without considering the fault ride-through characteristic.

8. The method for constructing the load model considering the fault ride-through characteristic of the photovoltaic generator as claimed in claim 1, wherein the step of calculating the dynamic load equivalent parameters of the power supply and distribution area of the load site based on the power load data of the power supply and distribution area of the load site specifically comprises:

calculating the total stator winding copper loss Σ Pcu 1:

∑P_cu1＝∑P_n-∑P_emn；

calculating the rated slip Sn of the equivalent motor:

S_n＝∑P_cu2/∑P_emn；

calculating an equivalent inertia time constant H:

H＝∑E_energy/(∑P_emn-∑P_cu2)

wherein, P_emnFor rated electromagnetic power, T, of the motor_emnIs rated torque, S_nIs the rated slip, P, of the rotor_nIs rated active power, P_cu2For rotor winding copper loss, E_energyIs kinetic energy; sigma P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged.

9. The method for building the load model considering the fault ride-through characteristic of the photovoltaic generator according to claim 1, wherein the step of calculating the reactive compensation of the distribution and supply area of the substation according to the reactive power balance specifically comprises:

and setting m as the number of photovoltaic generators considering fault ride-through characteristics and contained below the high-voltage load node, and acquiring the reactive output Q of each photovoltaic generator i (i is 1.. eta., m)_PV1,iAnd then considering the actual reactive output Q of the equivalent photovoltaic generator with the fault ride-through characteristic_PV1For the sum of m photovoltaic generators considering the fault ride-through characteristic, the calculation formula is as follows:

and setting n as the number of photovoltaic generators which are contained under the high-voltage load node and do not consider fault ride-through characteristics, and acquiring the reactive output Q of each photovoltaic generator j (i is 1.. multidot.n)_PV2，jAnd the actual reactive output Q of the equivalent photovoltaic generator without considering the fault ride-through characteristic_PV2Reactive power output for n photovoltaic generators without considering fault ride-through characteristicsAnd the calculation formula is as follows:

reactive compensation Q of high-voltage transformer substation power distribution and supply area is calculated according to reactive power balance_SC：

-Q_SC＝Q-Q_D-(Q_IM+Q_Z+Q_I+Q_P-Q_PV1-Q_PV2)

Wherein Q is the reactive power of the sending end of the equivalent branch; q_DThe reactive loss is equivalent impedance of the power distribution network; q_IMReactive power absorbed for the induction motor; q_Z、Q_IAnd Q_PStatic constant impedance reactive load, static constant current reactive load and static constant power reactive load.

10. A load model system that accounts for photovoltaic generator fault ride-through characteristics, comprising:

the acquisition device is used for acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment characteristic data;

the first computing device is used for computing equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation; calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic; according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride-through characteristic, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride-through characteristic; calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station; calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

the equivalent device is used for equivalent all motors in the power distribution and supply area of the transformer substation into a single-machine equivalent model according to the physical mechanism characteristics of the induction motor and calculating the electrical parameters of the single-machine equivalent model;

and the second calculating device is used for calculating the reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance.

Technical Field

The invention relates to the technical field of power system simulation modeling, in particular to a load model construction method considering the fault ride-through characteristic of a photovoltaic generator.

Background

Along with the spread of global warming and energy crisis, the proportion of distributed power supplies in a power grid is increasingly emphasized by the advantages of less pollution, high reliability, high energy utilization rate, flexible installation places and the like, and along with the gradual increase of the capacity of the distributed power supplies accessed into a system, the influence of the distributed power supplies on the dynamic and steady-state characteristics of the power system is more obvious. The photovoltaic cell has the characteristics of light weight, no rotating parts, low cost, no pollution, wide application range, safe use and the like, so that the photovoltaic cell is widely applied to small and large power generation systems.

According to statistics, the photovoltaic installation of the power grid in Jiangsu in 2021 reaches 8GW, the photovoltaic installation of the power grid in Anhui reaches 11GW, with the continuous increase of photovoltaic output and the continuous improvement of photovoltaic permeability, the safety and stability operation of the power grid are greatly influenced, especially when the power grid fails, the sudden grid disconnection of a photovoltaic power station further deteriorates the operation state of the power grid, and more serious consequences are brought, and the problem frequently occurs in the large-scale development of photovoltaic power generation.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a load model construction method considering the fault ride-through characteristic of a photovoltaic generator, which can be provided in a power system with a high proportion of distributed photovoltaic generators and still obtain high reliability of simulation calculation.

The invention further provides a load model construction method of the load model construction method for distinguishing the fault ride-through characteristics of the distributed photovoltaic generator.

According to the embodiment of the first aspect of the invention, the load model construction method considering the fault ride-through characteristic of the photovoltaic generator is characterized by comprising the following steps:

acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment physical mechanism characteristic data;

calculating equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation;

calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic;

according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride-through characteristic, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride-through characteristic;

calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

according to the physical mechanism characteristics of the induction motor, all motors in the power distribution and supply area of the transformer substation are equivalent to a single-machine equivalent model, and the electrical parameters of the motors are calculated;

and calculating reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance.

The load model construction method considering the fault ride-through characteristic of the photovoltaic generator provided by the embodiment of the invention at least has the following beneficial effects: the method comprises the steps of adding a photovoltaic generator with a fault ride-through characteristic considered and a photovoltaic generator without a fault ride-through characteristic considered in a traditional comprehensive load model to simulate the influence of all photovoltaic power stations in a power distribution and supply area of a transformer substation on a power grid, and according to the characteristics of the model, calculating the equivalent impedance of a power distribution network of a load station with a distributed photovoltaic power generation system, the system model parameters of the distributed photovoltaic generator with the fault ride-through characteristic considered and the system model parameters of the distributed photovoltaic generator without the fault ride-through characteristic considered by utilizing network topology data, distributed photovoltaic power generation system data and power load data of the transformer substation. By the aid of the method, simulation results with high accuracy can be obtained in power supply areas with high occupation of distributed photovoltaic generators.

According to some embodiments of the invention, the load model is implemented by adding an equivalent photovoltaic generator considering the fault ride-through characteristics and an equivalent photovoltaic generator not considering the fault ride-through characteristics to a virtual bus of an integrated load model (SLM) considering the distribution network.

According to some embodiments of the present invention, the step of calculating the static load equivalent parameter of the power supply and distribution area of the load site based on the power load data of the power supply and distribution area of the load site further includes:

establishing a polynomial load model;

calculating the total stator winding copper loss sigma Pcu1, the rated slip Sn of the equivalent motor and the equivalent inertia time constant H;

calculating a stator resistance RS, a stator leakage reactance XS, a rotor resistance Rr, a rotor leakage reactance Xr and an excitation reactance Xm of the equivalent motor model; .

According to some embodiments of the present invention, the step of calculating reactive compensation of the substation distribution and supply area according to the reactive power balance specifically includes:

acquiring the reactive power output of the photovoltaic motor considering the fault ride-through characteristic;

obtaining the reactive power output of the photovoltaic motor without considering the fault ride-through characteristic;

and calculating reactive compensation of the distribution and power supply area of the high-voltage transformer substation. .

According to some embodiments of the present invention, the step of calculating the equivalent impedance of the distribution network including the load sites of the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data, and the power load data of the substation specifically includes:

wherein Z is_DRepresenting the equivalent impedance of the distribution network; p_hRepresenting the active power, Q, of the distribution line or of the transformer's feeder terminal_hIndicating reactive power, U, of distribution line or transformer h-terminal_hIndicating the bus voltage, Z, of the feeder terminal of the line or transformer_hRepresenting the impedance of the distribution line or transformer h, I_L,kRepresenting the kth load branch current, I_PV1,iRepresenting the output current of a photovoltaic generator I taking into account the low voltage ride through characteristic, I_PV2,jThe output current of the photovoltaic generator j without considering the low voltage ride through characteristic is shown, f is the number of distribution lines or transformer buses, l is the number of load branches, m is the number of distributed photovoltaic generators considering the low voltage ride through characteristic, and n is the number of distributed photovoltaic generators not considering the low voltage ride through characteristic.

According to some embodiments of the present invention, the step of calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic specifically includes:

obtaining and summing the active power output of each photovoltaic generator:

m is the number of the photovoltaic generators which are contained under the high-voltage load nodes and take the fault ride-through characteristic into considerationNumber, P_PV1,iFor the active power output, P, of the respective photovoltaic generator i (i ═ 1, … …, m)_PV1The sum of the actual active power output of all the photovoltaic generators considering the fault ride-through characteristic;

calculating the percentage N of the active output of each photovoltaic generator considering the fault ride-through characteristics to the active output of all photovoltaic generators considering the fault ride-through characteristics under the power supply and distribution area where the voltage load nodes are located_1,i：

N_1，i＝P_PV1，i/P_PV1 i＝1,...,m；

Calculating control parameters of the equivalent distributed photovoltaic generator considering the fault ride-through characteristic, and adopting the active power output PPV1 of each distributed photovoltaic generator considering the fault ride-through characteristic, wherein i accounts for the percentage N1 of the sum PPV1 of the active power outputs of the distributed photovoltaic generators considering the fault ride-through characteristic, and i is a weighting factor to be synthesized:

in the formula, K_PV1，iFor preset control parameters, K, of the distributed photovoltaic generator i taking into account the fault-ride-through behaviour_PV1The parameter values are aggregated for a model of an equivalent distributed photovoltaic generator that takes into account fault ride-through characteristics.

According to some embodiments of the present invention, the step of calculating equivalent distributed photovoltaic power generation system model parameters not considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system not considering the fault ride-through characteristic specifically includes:

and taking n as the number of the photovoltaic generators which are contained under the high-voltage load node and do not consider the fault ride-through characteristic, and obtaining the active power P of each photovoltaic generator j (i is 1, … …, n)_PV2,jAnd the actual active output P of all photovoltaic generators without considering the fault ride-through characteristic below the high-voltage load node_PV2The sum of the active power output of n photovoltaic generators without considering the fault ride-through characteristic is as follows:

an active power P of each photovoltaic generator j (j ═ 1.. multidot.n) without consideration of fault ride-through characteristics_PV2,jPercentage N of active output of all photovoltaic generators without considering fault ride-through characteristics under power distribution area where high-voltage load nodes are located_2,jComprises the following steps:

N_2，j＝P_PV2,j/P_PV2 j＝1,...,n

the control parameters of the equivalent distributed photovoltaic generator without considering the fault ride-through characteristic adopt the active output P of each distributed photovoltaic generator without considering the fault ride-through characteristic_PV2,jThe sum P of the active power output of the distributed photovoltaic generator without considering the fault ride-through characteristic_PV2Percentage of (N)_2,jFor the integration of the weighting factors, the calculation formula is as follows:

in the formula, K_PV2，jFor preset control parameters, K, of the distributed photovoltaic generator j without taking into account the fault-ride-through characteristics_PV2And aggregating parameter values for the equivalent distributed photovoltaic generator model without considering the fault ride-through characteristic.

According to some embodiments of the present invention, the step of calculating the dynamic load equivalent parameter of the power supply and distribution area of the load site based on the power load data of the power supply and distribution area of the load site specifically includes:

calculating the total stator winding copper loss Σ Pcu 1:

∑P_cu1＝∑P_n-∑P_emn；

calculating the rated slip Sn of the equivalent motor:

S_n＝∑P_cu2/∑P_emn；

calculating an equivalent inertia time constant H:

H＝∑E_energy/(∑P_emn-∑P_cu2)

wherein, P_emnFor rated electromagnetic power, T, of the motor_emnIs rated torque, S_nIs the rated slip, P, of the rotor_nIs rated active power, P_cu2For rotor winding copper loss, E_energyIs kinetic energy; sigma P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged.

According to some embodiments of the present invention, the step of calculating reactive compensation of the substation distribution and supply area according to the reactive power balance specifically includes:

and setting m as the number of photovoltaic generators considering fault ride-through characteristics and contained below the high-voltage load node, and acquiring the reactive output Q of each photovoltaic generator i (i is 1.. eta., m)_PV1,iAnd then considering the actual reactive output Q of the equivalent photovoltaic generator with the fault ride-through characteristic_PV1For the sum of m photovoltaic generators considering the fault ride-through characteristic, the calculation formula is as follows:

and setting n as the number of photovoltaic generators which are contained under the high-voltage load node and do not consider fault ride-through characteristics, and acquiring the reactive output Q of each photovoltaic generator j (i is 1.. multidot.n)_PV2，jAnd the actual reactive output Q of the equivalent photovoltaic generator without considering the fault ride-through characteristic_PV2For the sum of the reactive power output of n photovoltaic generators without considering the fault ride-through characteristic, the calculation formula is as follows:

reactive compensation Q of high-voltage transformer substation power distribution and supply area is calculated according to reactive power balance_SC：

-Q_SC＝Q-Q_D-(Q_IM+Q_Z+Q_I+Q_P-Q_PV1-Q_PV2)

Wherein Q is equalReactive power of a branch sending end; q_DThe reactive loss is equivalent impedance of the power distribution network; q_IMReactive power absorbed for the induction motor; q_Z、Q_IAnd Q_PStatic constant impedance reactive load, static constant current reactive load and static constant power reactive load.

According to a second aspect of the invention, the load model system considering the fault ride-through characteristic of the photovoltaic generator is characterized by comprising:

the acquisition device is used for acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment characteristic data;

the first computing device is used for computing equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation; calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic; according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride-through characteristic, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride-through characteristic; calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station; calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

the equivalent device is used for equivalent all motors in the power distribution and supply area of the transformer substation into a single-machine equivalent model according to the physical mechanism characteristics of the induction motor and calculating the electrical parameters of the single-machine equivalent model;

and the second calculating device is used for calculating the reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic structural diagram of a load model considering the fault ride-through characteristics of a photovoltaic generator according to an embodiment of the present invention;

fig. 2 is a schematic step diagram of a method for constructing a load model considering a fault ride-through characteristic of a photovoltaic generator according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the existing power system simulation operation, since the occupation ratio of the distributed photovoltaic generators is not high, in the simulation process, all the photovoltaic generators are generally considered to have fault ride-through characteristics or not to have the fault ride-through characteristics, so that a large error is not caused.

However, as the duty ratio of distributed photovoltaic generators increases year by year, the error of the existing power simulation system is often insufficient to meet the demand. In order to solve such a problem, a load model capable of considering whether the distributed photovoltaic generator has a fault ride-through characteristic or not, and a data operation method based on the model are provided.

Referring to fig. 1, the load model described in the present application is based on an integrated load model (SLM) modification that considers the distribution network, i.e. adding a first equivalent photovoltaic generator and a second equivalent photovoltaic generator to the virtual bus of the integrated load model.

Wherein the first equivalence photovoltaic generators represent all photovoltaic generators considering fault ride-through characteristics; the second equivalent photovoltaic generator represents all photovoltaic generators that do not consider fault ride-through characteristics.

Referring to fig. 2, an embodiment of the present invention provides a method of outputting power simulation data based on the load model described above. The method comprises the following steps:

s100, acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment characteristic data;

in the simulation process of the power system, some data used as a basis are needed for calculating a simulation result, and in the load model described in the application, the needed data comprise network topology data, distributed photovoltaic power generation system data, substation load equipment composition data and load equipment characteristic data.

And S200, calculating equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation.

With reference to equation (1):

wherein Z is_DRepresenting the equivalent impedance of the distribution network; p_hRepresenting the active power, Q, of the distribution line or of the transformer's feeder terminal_hIndicating reactive power, U, of distribution line or transformer h-terminal_hIndicating the bus voltage, Z, of the feeder terminal of the line or transformer_hRepresenting the impedance of the distribution line or transformer h, I_L,kRepresenting the kth load branch current, I_PV1,iRepresenting the output current of a photovoltaic generator I taking into account the low voltage ride through characteristic, I_PV2,jShow not taking into accountThe photovoltaic generators j with the low voltage ride through characteristic output current, f is the number of distribution lines or transformer buses, l is the number of load branches, m is the number of distributed photovoltaic generators considering the low voltage ride through characteristic, and n is the number of distributed photovoltaic generators not considering the low voltage ride through characteristic.

And S300, calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic.

And setting m as the number of photovoltaic generators considering fault ride-through characteristics and included below the high-voltage load node, and acquiring the active output P of each photovoltaic generator i (i is 1.. eta., m)_PV1,iAnd the actual active output P of all photovoltaic generators considering the fault ride-through characteristic under the high-voltage load node_PV1For the sum of m active outputs of the photovoltaic generators considering the fault ride-through characteristic, referring to formula (2):

calculating an active power P of each photovoltaic generator i (i ═ 1.. multidot.m) considering fault ride-through characteristics_PV1，iPercentage N of active output of all photovoltaic generators considering fault ride-through characteristics under power distribution area where high-voltage load nodes are located_1,iComprises the following steps:

control parameters of equivalent distributed photovoltaic generators considering fault ride-through characteristics adopt active power output P of each distributed photovoltaic generator considering fault ride-through characteristics_PV1,iThe sum P of active power output of the distributed photovoltaic generator considering the fault ride-through characteristic_PV1Percentage of (N)_1,iFor the integration of the weighting factors, the calculation formula is as follows formula (4):

in the formula, K_PV1，iFor preset control parameters, K, of the distributed photovoltaic generator i taking into account the fault-ride-through behaviour_PV1The parameter values are aggregated for a model of an equivalent distributed photovoltaic generator that takes into account fault ride-through characteristics.

And S400, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride through characteristic.

And taking n as the number of photovoltaic generators which are contained under the high-voltage load node and do not consider fault ride-through characteristics, and acquiring the active output P of each photovoltaic generator j (i ═ 1.. multidot.n)_PV2，jAnd the actual active output P of all photovoltaic generators without considering the fault ride-through characteristic below the high-voltage load node_PV2For the sum of the active outputs of n photovoltaic generators without considering the fault ride-through characteristic, refer to formula (5):

an active power P of each photovoltaic generator j (j ═ 1.. multidot.n) without consideration of fault ride-through characteristics_PV2，jPercentage N of active output of all photovoltaic generators without considering fault ride-through characteristics under power distribution area where high-voltage load nodes are located_2，jComprises the following steps:

the control parameters of the equivalent distributed photovoltaic generator without considering the fault ride-through characteristic adopt the active output P of each distributed photovoltaic generator without considering the fault ride-through characteristic_PV2,jThe sum P of the active power output of the distributed photovoltaic generator without considering the fault ride-through characteristic_PV2Percentage of (N)_2,jFor the integration of the weighting factors, the calculation formula is as follows:

in the formula, K_PV2，jFor preset control parameters, K, of the distributed photovoltaic generator j without taking into account the fault-ride-through characteristics_PV2And aggregating parameter values for the equivalent distributed photovoltaic generator model without considering the fault ride-through characteristic.

And S500, calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station.

Establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c] (8)

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ] (9)

the active power coefficients of the polynomial load model are a, b and c, and the reactive power coefficients are alpha, beta, gamma and V_oIndicating the rated voltage, P, of the load_oAnd Q_oRespectively expressed at rated voltage V_oRated active power and reactive power of the lower load.

Equivalence to static load is mainly to coefficient P_oA, b, c and Q_oThe equivalence of alpha, beta, gamma, to polynomial load models is based on the sensitivity of the load power to the load terminal voltage, i.e.

P₁，P₂…，P_lAnd Q₁，Q₂…，Q_lFor the active power and the reactive power of each static load, the corresponding polynomial load model coefficients are respectively P_o1…P_ol、a₁…a_l、b₁…b_l、c₁…c_lAnd Q_o1…Q_ol、α₁…α_l、β₁…β₁、γ₁…γ_l. When V is equal to V_oSometimes:

and S600, calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station.

The total stator winding copper loss Σ Pcu1 is calculated, referring to equation (15):

∑P_cu1＝∑P_n-∑P_emn (15)

the rated slip Sn of the equivalent motor is calculated, referring to equation (16):

S_n＝∑P_cu2/∑P_emn (16)

calculating the equivalent inertia time constant H, with reference to equation (17):

H＝∑E_energy/(∑P_emn-∑P_cu2) (17)

wherein, P_emnFor rated electromagnetic power, T, of the motor_emnIs rated torque, S_nIs the rated slip, P, of the rotor_nIs rated active power, P_cu2For rotor winding copper loss, E_energyIs kinetic energy, Sigma P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged.

And S700, equating all motors in the power distribution and supply area of the transformer substation to a single-machine equivalent model according to the physical mechanism characteristics of the induction motors, and calculating the electrical parameters of the motors.

The electrical parameter comprises stator resistance R_sStator leakage reactance X_sRotor resistance R_rRotor leakage reactance X_rAnd an excitation reactance X_m. Setting the rated phase voltage as Un, and the calculation flow of the electrical parameters is as follows:

step S701, order P_{emt_max}＝∑P_{em_max}；P_{ent_max}For the total maximum electromagnetic power, P_{em_max}Is the maximum electromagnetic power;

step S702, setting the total stator phase current as

Wherein Pn is rated active power, Qn is rated reactive power, and Un is rated phase voltage;

wherein, P_culFor stator winding copper loss, In is the total stator phase current;

step S703 of calculating equivalent impedance Z of equivalent motor_deq

Wherein R is_depIs the equivalent resistance, X, of an equivalent motor_depJ is the equivalent reactance of an equivalent motor and is the imaginary unit of the complex number.

Step S704, calculating X_r＝X_s

Step S705, calculating stator resistance R_sStator leakage reactance X_sRotor leakage reactance X_rAnd equivalent impedance Z_deq＝R_deq+jX_deqCalculating the rotor resistance R_rAnd an excitation reactance X_mSo that P is_em＝∑P_emThis is true.

Wherein, K_rIs the difference between the equivalent resistance and the stator resistance of an equivalent motor, K_xIs the difference between the equivalent reactance of the equivalent motor and the stator reactance.

Step S706, according to the obtained R_s，X_s，R_r，X_rAnd X_mThe maximum electromagnetic power is recalculated according to the simplified formula:

and step S707, calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit.

Thevenin equivalent impedance is:

wherein R is_dpIs a Thevenin equivalent resistance, X_dpIs a Thevenin equivalent reactance, Z_dpIs thevenin equivalent impedance.

The conditions for generating the maximum electromagnetic power are:

wherein S is_mIs critical slip, R_pmIs the Thevenin equivalent impedance value corresponding to the maximum electromagnetic power;

the open circuit voltage of the Thevenin equivalent circuit is as follows:

the actual maximum electromagnetic torque corresponding to the new parameter is recalculated according to the following formula:

step S708, calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}

Step S709, compare P_{em_maxi}And P_{em_max}The difference of (a).

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}| (30)

If Err_{Pem_max}≥1.0e^-5Then, the process returns to step S704, otherwise, the calculation is ended.

It is understood that the judgment in the step S709 is based on e^-5The method is an artificially set error value, and can be realized by replacing the error with other numerical values, the calculation precision can be increased by selecting a smaller number, the iteration times can be reduced by selecting a larger value, and the calculation speed can be increased. This example takes a preferred choice as demonstration.

And step S800, calculating reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance. The method specifically comprises the following steps:

step S801,And setting m as the number of photovoltaic generators considering fault ride-through characteristics and contained below the high-voltage load node, and acquiring the reactive output Q of each photovoltaic generator i (i is 1.. eta., m)_PV1,iAnd then considering the actual reactive output Q of the equivalent photovoltaic generator with the fault ride-through characteristic_PV1For the sum of the reactive power outputs of m photovoltaic generators considering the fault ride-through characteristic:

step S802, setting n as the number of photovoltaic generators included under the high-voltage load node without considering the fault ride-through characteristic, and obtaining the reactive power Q of each photovoltaic generator j (i ═ 1..,.., n)_PV2，jAnd the actual reactive output Q of the equivalent photovoltaic generator without considering the fault ride-through characteristic_PV2The sum of the reactive power output of n photovoltaic generators without considering the fault ride-through characteristic is as follows:

step S803, calculating reactive compensation Q of the distribution and power supply area of the high-voltage transformer substation according to reactive power balance_SC：

Wherein Q is the reactive power of the sending end of the equivalent branch; q_DThe reactive loss is equivalent impedance of the power distribution network; q_IMReactive power absorbed for the induction motor; q_Z、Q_IAnd Q_PStatic constant impedance reactive load, static constant current reactive load and static constant power reactive load.

It can be understood that, the above steps S200 to S800 all describe a method for calculating parameters in a model, and even if the sequence of the replacement parts is such that the sequence of the replacement steps is within the scope that a practitioner skilled in the art of the present application can understand as long as the required values for calculation belong to known values. The steps are described herein for clarity of illustration only and are not to be construed as limitations of the method.

The application describes a method for outputting power simulation data based on a load model, which aims to obtain simulation data of a power system. And when the data obtained by simulation reaches the required precision, outputting the simulation data in a preset format. The preset format may be that the data is listed directly by using a table, the same type of data may be integrated and then presented, or power grids in different regions may be separated, and all data of each part of the power grid may be visually presented without departing from the spirit of the present application.

There is also provided, in accordance with an embodiment of the second aspect of the present invention, a system, including:

the acquisition device is used for acquiring network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment characteristic data;

the first computing device is used for computing equivalent impedance of a power distribution network of a load station containing the distributed photovoltaic power generation system according to the network topology data, the distributed photovoltaic power generation system data and the power load data of the transformer substation; calculating equivalent distributed photovoltaic power generation system model parameters considering the fault ride-through characteristic according to the physical mechanism characteristic of the distributed photovoltaic power generation system considering the fault ride-through characteristic; according to the physical mechanism characteristic of the distributed photovoltaic power generation system without considering the fault ride-through characteristic, calculating equivalent distributed photovoltaic power generation system model parameters without considering the fault ride-through characteristic; calculating static load equivalent parameters of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station; calculating a dynamic load equivalent parameter of the power supply and distribution area of the load station according to the power load data of the power supply and distribution area of the load station;

the equivalent device is used for equivalent all motors in the power distribution and supply area of the transformer substation into a single-machine equivalent model according to the physical mechanism characteristics of the induction motor and calculating the electrical parameters of the single-machine equivalent model;

and the second calculating device is used for calculating the reactive compensation of the power distribution and supply area of the transformer substation according to the reactive power balance.

The system can simulate the load model described in the embodiment in a code form, and simulate the operation state of the power grid according to network topology data, distributed photovoltaic power generation system data, transformer substation load equipment composition data and load equipment characteristic data, so that the operation state of the power grid is obtained.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.