CN113328430A - Load model structure containing distributed photovoltaic power generation and parameter calculation method and system - Google Patents

Abstract

The invention provides a load model structure containing distributed photovoltaic power generation and a method and a system for determining parameters of the load model, which are used for establishing a comprehensive load model containing distributed photovoltaic power generation: the model comprises a distribution network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model; the method for calculating the equivalent impedance of the distribution network with the distributed photovoltaic power generation integrated load model, the method for determining the equivalent distributed photovoltaic power generation system model parameters, the method for calculating the equivalent static load model parameters, the method for calculating the equivalent motor load model parameters and the method for calculating the reactive compensation of the distribution network are provided.

Description

Load model structure containing distributed photovoltaic power generation and parameter calculation method and system

Technical Field

The invention relates to the technical field of power system simulation modeling, in particular to a method and a system for determining a load model structure and parameters of photovoltaic power generation.

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 proportion of photovoltaic power generation equipment in a load area is larger and larger, the fault ride-through characteristic of the photovoltaic power generation equipment has a great influence on the safety and stability characteristics of an alternating current power grid, for example, after the frequency drops to 49.25Hz and the delay time is 0.2s, the system frequency may drop below 49Hz after the distributed photovoltaic power grid is disconnected, and a low-frequency load shedding action is triggered, so that a load modeling method for considering photovoltaic power generation needs to be researched urgently.

In consideration of the load modeling problem of the photovoltaic power generation system, scholars at home and abroad propose photovoltaic models based on a BP neural network, three-phase unipolar photovoltaic grid-connected systems and photovoltaic array models. However, tens of thousands of distributed photovoltaic generators are arranged below many 220kV substations, and detailed modeling of each distributed photovoltaic generator is impossible in simulation calculation of a power system, which causes dimension disasters, and particularly, requirements on simulation speed and parameter setting cannot be met for large-scale power system simulation.

At present, the load modeling problem of a photovoltaic power generation system is rarely considered at home and abroad, and scholars at home and abroad propose photovoltaic models based on a BP neural network, models of a three-phase single-pole photovoltaic grid-connected system and models of a photovoltaic array. However, a large number of distributed photovoltaic generators are arranged below a plurality of 220kV substations, and each distributed photovoltaic generator cannot be modeled in detail in the simulation calculation of the power system, which causes dimension disasters, and particularly for large-scale power system simulation, the requirements on simulation speed and parameter setting cannot be met.

Therefore, a technique is needed to determine load model structures and parameters for photovoltaic power generation.

Disclosure of Invention

The technical scheme of the invention provides a load model structure containing distributed photovoltaic power generation and a method for determining parameters of the load model, wherein the method comprises the following steps:

providing a comprehensive load model structure containing distributed photovoltaic power generation, wherein the comprehensive load model structure comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model;

the method comprises the following steps of providing a method for calculating the equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation, a method for determining the model parameters of an equivalent distributed photovoltaic power generation system, a method for calculating the equivalent static load model parameters, a method for calculating the equivalent motor load model parameters, and a method for calculating the reactive compensation of the distribution network:

providing a distribution network equivalent impedance calculation method of a comprehensive load model containing distributed photovoltaic power generation based on network topology data of a power distribution and supply area of a 220kV or 330kV transformer substation, distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and calculating distribution network equivalent impedance of the comprehensive load model containing distributed photovoltaic power generation;

the method comprises the steps of determining equivalent distributed photovoltaic power generation system model parameters based on the distributed photovoltaic power generation system data of a power supply and distribution area of a 220kV or 330kV transformer substation and based on the physical mechanism characteristics of the equivalent distributed photovoltaic power generation system;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

calculating equivalent motor load model parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

and calculating the distribution network reactive compensation parameters of the distribution power supply area of the 220kV or 330kV transformer substation based on the reactive power data of the distribution power supply area of the 220kV or 330kV transformer substation.

Preferably, the method for calculating the equivalent impedance of the distribution network comprising the comprehensive load model of the distributed photovoltaic power generation is determined based on the network topology data, the equivalent distributed photovoltaic power generation system data and the power load data of the 220kV or 330kV substation in the power distribution and supply area of the 220kV or 330kV substation, and the method for calculating the equivalent impedance of the distribution network comprising the comprehensive load model of the distributed photovoltaic power generation comprises the following steps:

according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network, calculating the equivalent impedance of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkAnd the photovoltaic power generation current is represented, l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed photovoltaic generator.

Preferably, the calculating the parameters of the equivalent distributed photovoltaic power generation system based on the equivalent method of the distributed photovoltaic power generation system includes:

let n be the number of photovoltaic generators included below the high-voltage load node, obtain the active power P of each photovoltaic generator i (i ═ 1.., n)_PViAll photovoltaics below the high voltage load nodeActual active power output P of the generator_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViPercentage N of active power output of all photovoltaic generators below a power distribution area where high-voltage load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent distributed photovoltaic power generation system model is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of fixed direct-current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

alignment of equivalent distributed photovoltaic power generation system modelProportionality coefficient K of current-voltage controller_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent distributed photovoltaic power generation system model for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent distributed photovoltaic power generation system model for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent distributed photovoltaic power generation system model_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}An active current set value at the initial moment of the low-voltage ride-through ending of a photovoltaic generator i (i ═ 1., n);

current setting climbing initial value I of equivalent distributed photovoltaic power generation system model_pdR0Comprises the following steps:

wherein, I_pdR0iFor photovoltaic generatorsSetting an initial value of climbing for the current of i (i ═ 1.,. n);

proportional coefficient K for reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

Preferably, the calculating the equivalent static load parameter of the power distribution and supply area of the 220kV or 330kV substation based on the power load data of the power distribution and supply area of the 220kV or 330kV substation further includes:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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.

Preferably, the calculating equivalent motor load model parameters of the power supply area supplied by the 220kV or 330kV substation based on the power load data of the power supply area supplied by the 220kV or 330kV substation further includes:

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

∑P_cu1＝∑P_n-∑P_emn

S_n＝∑P_cu2/∑P_emn

H＝∑E_energy/(∑P_emn-∑P_cu2)

pemn is rated electromagnetic power of the motor, Temn is rated torque, Sn is rated slip of the rotor, Pn is rated active power, Pcu2 is rotor winding copper loss, Eenergy is kinetic energy;

where ∑ P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged;

calculating the equivalent impedance Z of an equivalent motor_deq：

R_deq＝real(Z_deq)

X_deq＝imag(Z_deq)

Wherein R is_depIs the equivalent resistance, X, of an equivalent motor_depIs the equivalent reactance of the equivalent motor, j is the imaginary unit of complex number;

calculating X_sAnd X_r：

X_r＝X_s

X is always assumed in this algorithm_r＝X_sAnd X is calculated from the formula_sAnd X_rIs necessarily small because of the simplified maximum electromagnetic power formulaThe maximum electromagnetic power obtained by calculation is larger than the actual maximum electromagnetic power, so that the X is required to be subjected to an iterative method_sAnd X_rCorrecting;

according to the calculated 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_emIs formed, 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:

K_r＝R_deq-R_s

K_x＝X_deq-X_s

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

calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit:

thevenin equivalent impedance is:

R_dp＝real(Z_dp)

X_dp＝imag(Z_dp)

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:

calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}：

P_{emt_max}＝k_maxiP_{em_max}

Comparison P_{em_maxi}And P_{em_max}The difference of (a):

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}|

if Err_{Pem_max}≥1.0e^-5And (4) returning to the step (4) for recalculation, otherwise, ending the calculation.

Preferably, the calculating a distribution network reactive compensation parameter of a distribution power supply area supplied by a 220kV or 330kV substation based on reactive power data of the distribution power supply area supplied by the 220kV or 330kV substation includes:

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_PV)

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_PRespectively a static constant impedance reactive load, a static constant current reactive load and a static constant power reactive load; q_PVThe reactive power generated by the equivalent photovoltaic generator.

Based on another aspect of the present invention, the present invention provides a load model structure including distributed photovoltaic power generation and a system for determining parameters of the load model, the system comprising:

the building unit is used for providing a comprehensive load model structure containing distributed photovoltaic power generation, and the comprehensive load model structure comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model;

the determining unit is used for providing a method for calculating equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation, a method for determining equivalent distributed photovoltaic power generation system model parameters, a method for calculating equivalent static load model parameters, a method for calculating equivalent motor load model parameters, and a method for calculating reactive compensation of the distribution network:

the computing unit is used for providing a distribution network equivalent impedance computing method of the comprehensive load model containing the distributed photovoltaic power generation based on network topology data of a distribution power supply area of a 220kV or 330kV transformer substation, distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and computing the distribution network equivalent impedance of the comprehensive load model containing the distributed photovoltaic power generation;

the method comprises the steps of determining equivalent distributed photovoltaic power generation system model parameters based on the distributed photovoltaic power generation system data of a power supply and distribution area of a 220kV or 330kV transformer substation and based on the physical mechanism characteristics of the equivalent distributed photovoltaic power generation system;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

calculating equivalent motor load model parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

and calculating the distribution network reactive compensation parameters of the distribution power supply area of the 220kV or 330kV transformer substation based on the reactive power data of the distribution power supply area of the 220kV or 330kV transformer substation.

Preferably, the calculating unit is configured to determine a distribution network equivalent impedance calculating method including a distributed photovoltaic power generation integrated load model based on network topology data of a distribution power supply area of a 220kV or 330kV substation, equivalent distributed photovoltaic power generation system data, and power load data of the 220kV or 330kV substation, and calculate a distribution network equivalent impedance including the distributed photovoltaic power generation integrated load model, and includes:

according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network, calculating the equivalent impedance of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkRepresenting the photovoltaic power generation current, wherein l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed lightA photovoltaic generator.

Preferably, the calculation unit is configured to calculate parameters of an equivalent distributed photovoltaic power generation system based on an equivalent method of the distributed photovoltaic power generation system, and includes:

let n be the number of photovoltaic generators included below the high-voltage load node, obtain the active power P of each photovoltaic generator i (i ═ 1.., n)_PViThe actual active power output P of all the photovoltaic generators below the high-voltage load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViPercentage N of active power output of all photovoltaic generators below a power distribution area where high-voltage load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent distributed photovoltaic power generation system model is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of fixed direct-current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant direct current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent distributed photovoltaic power generation system model for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent distributed photovoltaic power generation system model for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent distributed photovoltaic power generation system model_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}Active power for the initial moment of the end of a low voltage ride through of a photovoltaic generator i (i ═ 1.., n.)A flow set value;

current setting climbing initial value I of equivalent distributed photovoltaic power generation system model_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

Preferably, the calculating unit is configured to calculate equivalent static load parameters of a power distribution area supplied by a 220kV or 330kV substation based on power load data of the power distribution area supplied by the 220kV or 330kV substation, and further includes:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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.

The invention provides a method and a system for determining a photovoltaic power generation load model structure, wherein the model designs a link considering a distributed photovoltaic power generation system aiming at a comprehensive load model structure, and equivalently simulates the characteristics of a plurality of distributed photovoltaic power generators in a power distribution area provided by a 220kV (or 330kV or 110kV) load station by adding an equivalent distributed photovoltaic power generation system module in the comprehensive load model structure. The technical scheme of the invention provides a statistical-integration-based method for determining model parameters of a constant-value distributed photovoltaic power generation system, so that the comprehensive load characteristics of a power distribution network comprising the distributed photovoltaic power generation system can be accurately simulated, the model overcomes the defect that the traditional dynamic load model cannot describe the influence of the distributed power generation system on the characteristics of the power grid, and the reliability of simulation calculation of the power system is improved.

Drawings

A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:

FIG. 1 is a schematic diagram of an integrated load model architecture for a distributed photovoltaic power generation system in accordance with a preferred embodiment of the present invention;

FIG. 2 is a flow chart for calculation of parameters for a photovoltaic power generation load model in consideration of the present invention;

FIG. 3 is a schematic diagram of a model architecture of a photovoltaic power generation system according to a preferred embodiment of the present invention;

FIG. 4 is a schematic diagram of a photovoltaic power generation model considering fault-ride-through characteristics according to a preferred embodiment of the present invention;

FIG. 5 is a schematic wiring diagram of load area of Xinjiang 220kV transformer substation according to the preferred embodiment of the invention;

FIG. 6 is a schematic diagram of a simulation system according to a preferred embodiment of the present invention;

FIG. 7 is a schematic diagram of a 220kV bus voltage curve according to a preferred embodiment of the invention;

FIG. 8 is a schematic diagram of an active power output curve of a distributed photovoltaic generator according to a preferred embodiment of the present invention;

FIG. 9 is a schematic illustration of a reactive power output curve of a distributed photovoltaic generator according to a preferred embodiment of the present invention;

fig. 10 is a schematic diagram of load active power curve of a Xinjiang 220kV transformer substation according to the preferred embodiment of the invention;

fig. 11 is a schematic diagram of load reactive power curve of a Xinjiang 220kV transformer substation according to the preferred embodiment of the invention.

Detailed Description

The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.

Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.

The invention provides a load model structure considering photovoltaic power generation and a parameter calculation method, provides a comprehensive load model structure containing photovoltaic power generation, and provides a comprehensive load model parameter aggregation equivalent method containing photovoltaic power generation on the basis of the comprehensive load model structure, so that the comprehensive load characteristics of a power distribution network containing photovoltaic power generation are accurately simulated, and the reliability of simulation calculation of a power system is improved.

The invention provides a comprehensive load model containing distributed photovoltaic power generation, which is shown in figure 1. The comprehensive load model comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor model and an equivalent distributed photovoltaic power generation system model; further, a calculation method for determining the equivalent impedance of the distribution network with the distributed photovoltaic power generation integrated load model, a determination method for equivalent distributed photovoltaic power generation system model parameters, a calculation method for equivalent static load model parameters, a calculation method for equivalent motor load model parameters and a distribution network reactive compensation calculation method are provided.

Based on network topology data of a power supply and distribution area of a 220kV (or 330kV) transformer substation, distributed photovoltaic power generation system data and power load data of the transformer substation, a method for calculating equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation is provided, and equivalent impedance of the distribution network containing the distributed photovoltaic power generation load model is calculated.

The invention provides a distributed photovoltaic power generation system model considering fault ride-through characteristics, and the distributed photovoltaic power generation system model is shown in figure 4. Based on the data of the distributed photovoltaic power generation system in the power supply and distribution area of the 220kV (or 330kV) transformer substation, the distributed photovoltaic power generation system model overcomes the defect that the fault ride-through characteristic of the photovoltaic power generation system is not considered in the conventional distributed photovoltaic power generation system model; then, a method for determining equivalent distributed photovoltaic power generation system model parameters based on physical mechanism characteristics of the distributed photovoltaic power generation system is provided;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV (or 330kV) transformer substation based on power load data of the power supply and distribution area of the 220kV (or 330kV) transformer substation;

calculating equivalent motor parameters of a power supply and distribution area of a 220kV (or 330kV) transformer substation based on power load data of the power supply and distribution area of the 220kV (or 330kV) transformer substation;

and calculating reactive compensation parameters of the power supply and distribution area of the 220kV (or 330kV) transformer substation based on the reactive power data of the power supply and distribution area of the 220kV (or 330kV) transformer substation.

The invention provides a method for determining a photovoltaic power generation load model structure. The load model structure considering the photovoltaic power generation system is shown in fig. 1, namely, an equivalent photovoltaic power generation system model is added to a virtual bus of a comprehensive load model (SLM) considering the power distribution network, so that the influence of the distributed photovoltaic power generation system on the power distribution network dynamics is considered. On the basis, an equivalent method for parameter aggregation of the comprehensive load model of the photovoltaic power generation system is provided, and a flow chart of the method is shown in FIG. 2. The method is characterized in that the equivalent impedance of the distribution network of a comprehensive load model of the distributed photovoltaic power generation system is calculated and considered by a distribution network impedance equivalent method; then calculating parameters of the equivalent photovoltaic power generation system by using an equivalent method of the distributed photovoltaic power generation system; then, calculating static load model parameters of a comprehensive load model of the power distribution network by using a static load equivalence method; finally, calculating dynamic load model parameters of a comprehensive load model considering the power distribution network by using a dynamic load equivalence method; therefore, online load modeling of load nodes of the distributed photovoltaic power generation system is achieved. The high voltage in the present invention includes, but is not limited to, 220kV, 330kV or 110kV, and the embodiment of the present invention is described by taking 220kV as an example.

The method for determining the load model structure and parameters of photovoltaic power generation specifically comprises the following steps:

(1) calculating the equivalent impedance of the distribution network of the comprehensive load model of the distributed photovoltaic power generation system by using a distribution network impedance equivalent method;

(2) calculating parameters of an equivalent photovoltaic power generation system by using an equivalent method of the distributed photovoltaic power generation system;

(3) calculating static load model parameters of a comprehensive load model considering the power distribution network by using a static load equivalence method; calculating dynamic load model parameters of a comprehensive load model considering the power distribution network by using a dynamic load equivalence method;

(4) and calculating reactive compensation parameters of the power distribution and supply area based on the reactive compensation data of the power distribution and supply area of the high-voltage transformer substation.

The method comprises the following steps that (1) the equivalent impedance of a power distribution network of a photovoltaic power generation load model is calculated based on network topology data of a power distribution and supply area of a 220kV transformer substation, distributed photovoltaic power generation system data and power load data of the transformer substation, and the method comprises the following steps:

according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network, calculating the equivalent impedance of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkAnd the photovoltaic power generation current is represented, l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed photovoltaic generator.

The equivalent method of the distributed photovoltaic power generation system in the step (2) comprises the following steps:

a typical structure diagram of a photovoltaic grid-connected system is shown in fig. 3, and the photovoltaic grid-connected system is composed of a photovoltaic cell and an inverter, wherein the inverter includes a dc bus and a capacitor, and is connected to an ac power grid through a step-up transformer. The inverter is a core element for controlling the photovoltaic power generation system, and under the same control mode, the dynamic characteristics of the photovoltaic power generation system are influenced by the control parameter difference of the inverter. The invention adopts a photovoltaic power generation model considering the fault ride-through characteristic, and the overall model structure is shown in figure 4 corresponding to the photovoltaic topological structure. The equivalence of the photovoltaic generator is therefore the equivalence of the capacitance C of the capacitor and the control parameters of the inverter. As can be seen from fig. 4, the inverter model includes 13 parameters: determining a parameter T associated with a DC voltage controller_mu、K_ud、T_ud(ii) a Determining a parameter T related to an AC voltage controller_mP、K_us、T_us(ii) a Relevant parameter U of active current control link in LVRT and recovery process_sL、U_sH、I_pmax、I_{pd_LVRT}、I_pdR0Related parameters K of reactive current control link in LVRT and recovery process_q、U_LVRT. In summary, the total number of the parameters of the photovoltaic power generation system is 14, which are the capacitance C of the capacitor and the 13 control parameters of the inverter.

The basic principle of the equivalence method of the distributed photovoltaic power generation system provided by the invention is that the active output of a photovoltaic generator is used as a weight to calculate the model parameters of the equivalent photovoltaic power generation system, and the parameters of the equivalent photovoltaic power generation system are calculated based on the data of the distributed photovoltaic power generation system in a 220kV transformer substation power distribution and supply area, and the method comprises the following steps:

and setting n as the number of photovoltaic generators included below a 220kV load node, and acquiring the active output P of each photovoltaic generator i (i is 1.., n)_PViAnd then the actual active power output P of all the photovoltaic generators below the 220kV load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViPercentage N of active output of all photovoltaic generators below a power distribution area where 220kV load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent photovoltaic power generation system is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant direct current voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant DC voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent photovoltaic power generation system_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, T_usiConstant alternating current for a photovoltaic generator i (i ═ 1.., n)The integral link coefficient of the voltage controller;

proportionality coefficient K of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent photovoltaic power generation system for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent photovoltaic power generation system for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

the maximum alternating active output current Ipmax of the inverter of the equivalent photovoltaic power generation system is as follows:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}An active current set value at the initial moment of the low-voltage ride-through ending of a photovoltaic generator i (i ═ 1., n);

current setting climbing initial value I of equivalent photovoltaic power generation system_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent photovoltaic power generation system_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent photovoltaic power generation system_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n). .

Step 3, calculating static load equivalent parameters of the power distribution and supply area based on the power load data of the power distribution and supply area of the 220kV transformer substation, and further comprising the following steps:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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 α, β, γ, to polynomial load model is based on the sensitivity of the load power to the load terminal voltage:

P₁，P₂…P_nand Q₁，Q₂…Q_nFor the active power and the reactive power of each static load, the corresponding polynomial load model coefficients are respectively P_o1…P_on、a₁…a_n、b₁…b_n、c₁…c_nAnd Q_o1…Q_on、α₁…α_n、β₁…β_n、γ₁…γ_n(ii) a When V is equal to V_oSometimes:

regarding step 3, the calculating of the equivalent parameters of the dynamic load of the power distribution and supply area based on the power load data of the power distribution and supply area of the 220kV substation further comprises:

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

∑P_cu1＝∑P_n-∑P_emn

S_n＝∑P_cu2/∑P_emn

H＝∑E_energy/(∑P_emn-∑P_cu2)

pemn is rated electromagnetic power of the motor, Temn is rated torque, Sn is rated slip of the rotor, Pn is rated active power, Pcu2 is rotor winding copper loss, Eenergy is kinetic energy;

where ∑ P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged;

calculating electrical parameters of an equivalent motor model, said electrical parameters including stator resistance R_sStator leakage reactance X_sRotor resistance R_rRotor leakage reactance X_rAnd an excitation reactance X_mSetting the rated phase voltage as Un, and the calculation flow of the electrical parameters is as follows:

(1) let P_{emt_max}＝∑P_{em_max}(ii) a Pent _ max is the total maximum electromagnetic power, and Pem _ max is the maximum electromagnetic power;

(2) let the total stator phase current be

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;

(3) calculating the equivalent impedance Z of an equivalent motor_deq：

R_deq＝real(Z_deq)

X_deq＝imag(Z_deq)

Wherein R is_depIs the equivalent resistance, X, of an equivalent motor_depIs the equivalent reactance of the equivalent motor, j is the imaginary unit of complex number;

(4) calculating X_sAnd X_r：

X_r＝X_s

X is always assumed in this algorithm_r＝X_sAnd X is calculated from the formula_sAnd X_rIs necessarily smaller because the maximum electromagnetic power calculated according to the simplified maximum electromagnetic power formula is larger than the actual maximum electromagnetic power, so that the X is required to be iteratively processed_sAnd X_rCorrecting;

(5) according to the calculated 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_emIs formed, 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:

K_r＝R_deq-R_s

K_x＝X_deq-X_s

(6) according to the obtained R_s，X_s，R_r，X_rAnd X_mThe maximum electromagnetic power is recalculated according to the simplified formula:

(7) calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit:

thevenin equivalent impedance is:

R_dp＝real(Z_dp)

X_dp＝imag(Z_dp)

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_pmTo correspond to maximum electromagnetic powerThevenin equivalent impedance value;

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:

(8) calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}：

P_{emt_max}＝k_maxiP_{em_max}

(9) Comparison P_{em_maxi}And P_{em_max}The difference of (a):

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}|

if Err_{Pem_max}≥1.0e^-5And (4) returning to the step (4) for recalculation, otherwise, ending the calculation.

Step 4, calculating reactive compensation parameters of the power distribution and supply area based on the reactive compensation data of the power distribution and supply area of the 220kV transformer substation, wherein the method comprises the following steps:

reactive compensation Q for calculating 220kV transformer substation power distribution and supply area according to reactive power balance_SC：

-Q_SC＝Q-Q_D-(Q_IM+Q_Z+Q_I+Q_P-Q_PV)

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_PAre respectively static constantImpedance reactive load, static constant current reactive load and static constant power reactive load; q_PVThe reactive power generated by the equivalent photovoltaic generator.

The invention provides a load model construction method considering photovoltaic power generation as the proportion of photovoltaic power generation equipment in a load area is larger and larger, and the fault ride-through characteristic of the load model construction method has great influence on the safety and stability characteristics of an alternating current power grid.

The fault ride-through characteristic of the photovoltaic power generation system is considered, the defect that the fault ride-through characteristic of the photovoltaic system is not considered in the existing load modeling technology considering the photovoltaic power generation system is overcome, and the characteristic of accurately simulating the distributed photovoltaic power generation system is realized.

The method determines the parameters of the comprehensive load model containing the photovoltaic power generation through field investigation and statistics, has definite parameter physical significance, and overcomes the defects that the parameter physical significance is indefinite and the model adaptability is not strong due to the adoption of a parameter identification method in the existing load modeling technology considering the photovoltaic power generation system.

In order to verify the effectiveness of the load modeling method considering the distributed photovoltaic power generation system, which is provided by the invention, the invention uses the actual system of the Xinjiang 220kV transformer substation as an example for analysis and explanation. The active load of a Xinjiang 220kV transformer substation is 178MW, 6 parts below a region supplied by the 220kV transformer substation are connected with distributed photovoltaic, the total installed power of the photovoltaic is 190MW, and the actual active output is 102 MW.

By carrying out detailed investigation on a Xinjiang 220kV transformer substation (a wiring diagram is shown in FIG. 5) and carrying out statistical analysis and calculation on investigation data of the transformer substation, the photovoltaic power generation situation in a distributed photovoltaic large power generation mode can be determined to be shown in Table 1, and the type of equipment mainly supplied by the Xinjiang 220kV transformer substation and the ratio occupied by each equipment type are shown in Table 2.

TABLE 1 distributed photovoltaic power generation situation of Xinjiang 220kV transformer substation

TABLE 2 load device type composition of Xinjiang 220kV substation in distributed photovoltaic power generation mode

According to detailed survey data of the Xinjiang 220kV transformer substation, the distribution network equivalent resistance of the Xinjiang 220kV transformer substation is calculated to be 0.0013, and the equivalent reactance is 0.0395 by adopting the distribution network equivalent impedance calculation method provided by the invention. According to detailed statistical data of a distributed photovoltaic power generation new system of a Xinjiang 220kV transformer substation, the equivalent distributed photovoltaic power generation system model parameter calculation method provided by the invention is adopted to calculate equivalent distributed photovoltaic power generation system model parameters of the Xinjiang transformer substation as shown in table 3, and according to detailed load statistical data of the Xinjiang 220kV transformer substation, motor groups in all equipment types are comprehensively calculated to obtain motor load model parameters of the Xinjiang transformer motor groups as shown in table 4, and static loads in all equipment types are comprehensively calculated to obtain static load model parameters of the Xinjiang transformer substation as shown in table 5.

Table 3 main circuit and controller parameters of equivalent photovoltaic inverter

Tmu

Kud

Tud

TmP

Kus

Tus

UsL

0.02s

2.0

10s

0.02s

18

0.2s

0.85

UsH

Ipmax

Ipd_LVRT

IpdR0

Kq

ULVRT

C

0.9

1.2

0.1

0.2

1.5

0.9

0.0183

TABLE 4 Xinjiang motor load model parameters

Rs	Xs	Xm	Rr	Xr	Tj	Motor ratio
							0.013	0.112	3.8	0.0093	0.11	2.82	65％

Note: rs represents motor stator resistance, Xs represents motor stator reactance, Xm represents motor excitation reactance, Rr represents motor rotor resistance, Xr represents motor rotor reactance, and Tj represents motor inertia time constant.

TABLE 5 Xinjiang transition static load model parameters

ZP％	ZQ％	IP％	IQ％	PP％	PQ％
						18	18	77	77	5	5

Note: ZP% represents a constant impedance component in the static active load configuration, ZQ% represents a constant impedance component in the static reactive load configuration, IP% represents a constant current component in the static active load configuration, IQ% represents a constant current component in the static reactive load configuration, PP% represents a constant power component in the static active load configuration, and PQ% represents a constant power reactive component in the static reactive load configuration.

In order to verify the effectiveness of the load modeling method considering the distributed photovoltaic power generation, which is provided by the invention, the load model parameters generated by the method are compared with the original system (including a 110kV and 35kV distribution network, a reactive compensation system and a 110kV, 35kV and 10kV load node system in a load region of Xinjiang river as shown in figure 5) in a simulation mode, so that the effectiveness of the load modeling considering the distributed photovoltaic power generation, which is provided by the invention, is verified.

The simulation system is shown in FIG. 6: one synchronous generator supplies power to the Xinjiang river through a double-circuit line.

Simulation conditions are as follows: and a three-permanent short circuit fault occurs on the Bus2-Bus 3-one loop Bus2 side, and the fault line is cut off after 0.12 second of fault.

The system of the Xinjiang 220kV transformer substation 110kV and below and the equivalent load model containing the distributed photovoltaic power generation system shown in FIG. 5 are connected to the Bus3 Bus shown in FIG. 6 respectively for simulation, and a voltage curve of the Xinjiang 220kV Bus, an active output of the distributed photovoltaic power generator, a reactive output of the distributed photovoltaic power generator, an active power curve of the Xinjiang 220kV Bus and a reactive power curve of the Xinjiang 220kV Bus are obtained and are shown in FIGS. 7-11 respectively. As can be seen from FIG. 7, the 220kV voltage response curves under the 2 models are substantially consistent. As can be seen from fig. 8 and 9, the equivalent photovoltaic generator can better simulate the active and reactive characteristics of the photovoltaic power generation system of the original system. As can be seen from fig. 10 and 11, the equivalent load model with the distributed photovoltaic power generation system can better fit the active and reactive response characteristics of the detailed system. In conclusion, it can be seen that the equivalent load model containing the distributed photovoltaic power generation system can better simulate the voltage, active power and reactive power characteristics of the original system. The effectiveness of the load modeling method comprising the distributed photovoltaic power generation system provided by the invention is verified.

In the method for determining the structure of the photovoltaic power generation load model in the preferred embodiment of the invention, the photovoltaic power generation load model comprises a power distribution network comprehensive load model, and an equivalent photovoltaic power generation system is arranged on a virtual bus of the power distribution network comprehensive load model.

Preferably, the method further comprises the following steps: calculating the equivalent impedance of a distribution network of a photovoltaic power generation load model based on network topology data of a distribution and power supply area of a 220kV transformer substation, distributed photovoltaic power generation system data and power load data of the transformer substation;

calculating parameters of an equivalent photovoltaic power generation system based on data of a distributed photovoltaic power generation system in a power distribution and supply area of a 220kV transformer substation;

calculating static load equivalent parameters and dynamic load equivalent parameters of a power distribution and supply area based on power load data of the power distribution and supply area of the 220kV transformer substation;

and calculating reactive compensation parameters of the power distribution and supply area based on the reactive compensation data of the power distribution and supply area of the 220kV transformer substation.

Preferably, the calculating of the equivalent impedance of the distribution network of the photovoltaic power generation load model based on the network topology data of the distribution and power supply area of the 220kV substation, the data of the distributed photovoltaic power generation system and the power load data of the substation includes:

calculating the equivalent impedance of the distribution network according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkAnd the photovoltaic power generation current is represented, l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed photovoltaic generator.

Preferably, the calculating of the parameters of the equivalent photovoltaic power generation system based on the data of the distributed photovoltaic power generation system in the power distribution and supply area of the 220kV substation includes:

and setting n as the number of photovoltaic generators included below a 220kV load node, and acquiring the active output P of each photovoltaic generator i (i is 1.., n)_PViAnd then the actual active power output P of all the photovoltaic generators below the 220kV load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating individual photovoltaic power generationActive power P of machine i (i ═ 1.., n)_PViPercentage N of active output of all photovoltaic generators below a power distribution area where 220kV load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent photovoltaic power generation system is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant direct current voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant DC voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent photovoltaic power generation system_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent photovoltaic power generation system for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent photovoltaic power generation system for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent photovoltaic power generation system_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}An active current set value at the initial moment of the low-voltage ride-through ending of a photovoltaic generator i (i ═ 1., n);

current setting climbing initial value I of equivalent photovoltaic power generation system_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent photovoltaic power generation system_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent photovoltaic power generation system_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

Preferably, the method for calculating the static load equivalent parameters of the power distribution and supply area based on the power load data of the power distribution and supply area of the 220kV substation further includes:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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 α, β, γ, to polynomial load model is based on the sensitivity of the load power to the load terminal voltage:

P₁，P₂…P_nand Q₁，Q₂…Q_nFor the active power and the reactive power of each static load, the corresponding polynomial load model coefficients are respectively P_o1…P_on、a₁…a_n、b₁…b_n、c₁…c_nAnd Q_o1…Q_on、α₁…α_n、β₁…β_n、γ₁…γ_n(ii) a When V is equal to V_oSometimes:

preferably, based on the power load data of the 220kV substation distribution and power supply area, calculating the equivalent parameters of the dynamic load of the distribution and power supply area further includes:

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

∑P_cu1＝∑P_n-∑P_emn

S_n＝∑P_cu2/∑P_emn

H＝∑E_energy/(∑P_emn-∑P_cu2)

pemn is rated electromagnetic power of the motor, Temn is rated torque, Sn is rated slip of the rotor, Pn is rated active power, Pcu2 is rotor winding copper loss, Eenergy is kinetic energy;

where ∑ P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged;

calculating electrical parameters of equivalent motor model, including stator resistance R_sStator leakage reactance X_sRotor resistance R_rRotor leakage reactance X_rAnd an excitation reactance X_mSetting rated phase voltage as Un, electrical referenceThe flow of number calculation is as follows:

(1) let P_{emt_max}＝∑P_{em_max}(ii) a Pent _ max is the total maximum electromagnetic power, and Pem _ max is the maximum electromagnetic power;

(2) let the total stator phase current be

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;

(3) calculating the equivalent impedance Z of an equivalent motor_deq：

R_deq＝real(Z_deq)

X_deq＝imag(Z_deq)

Wherein R is_depIs the equivalent resistance, X, of an equivalent motor_depIs the equivalent reactance of the equivalent motor, j is the imaginary unit of complex number;

(4) calculating X_sAnd X_r：

X_r＝X_s

X is always assumed in this algorithm_r＝X_sAnd X is calculated from the formula_sAnd X_rIs necessarily smaller because the maximum electromagnetic power calculated according to the simplified maximum electromagnetic power formula is larger than the actual maximum electromagnetic power, so that the X is required to be iteratively processed_sAnd X_rCorrecting;

(5) according to the calculated 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_emIs formed, 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:

K_r＝R_deq-R_s

K_x＝X_deq-X_s

(6) according to the obtained R_s，X_s，R_r，X_rAnd X_mThe maximum electromagnetic power is recalculated according to the simplified formula:

(7) calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit:

thevenin equivalent impedance is:

R_dp＝real(Z_dp)

X_dp＝imag(Z_dp)

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:

(8) calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}：

P_{emt_max}＝k_maxiP_{em_max}

(9) Comparison P_{em_maxi}And P_{em_max}The difference of (a):

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}|

if Err_{Pem_max}≥1.0e^-5And (4) returning to the step (4) for recalculation, otherwise, ending the calculation.

Preferably, calculating reactive compensation parameters of the power distribution and supply area based on reactive compensation data of the 220kV substation power distribution and supply area, including:

reactive compensation Q for calculating 220kV transformer substation power distribution and supply area according to reactive power balance_SC：

-Q_SC＝Q-Q_D-(Q_IM+Q_Z+Q_I+Q_P-Q_PV)

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_PRespectively a static constant impedance reactive load, a static constant current reactive load and a static constant power reactive load; q_PVThe reactive power generated by the equivalent photovoltaic generator.

An embodiment of the present invention provides a system for determining a load model structure and parameters including distributed photovoltaic power generation, the system comprising:

the building unit is used for providing a comprehensive load model structure containing distributed photovoltaic power generation, and the comprehensive load model structure comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model;

the determining unit is used for providing a method for calculating equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation, a method for determining equivalent distributed photovoltaic power generation system model parameters, a method for calculating equivalent static load model parameters, a method for calculating equivalent motor load model parameters, and a method for calculating reactive compensation of the distribution network:

the computing unit is used for providing a distribution network equivalent impedance computing method of the comprehensive load model containing the distributed photovoltaic power generation based on network topology data of a distribution power supply area of a 220kV or 330kV transformer substation, distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and computing the distribution network equivalent impedance of the comprehensive load model containing the distributed photovoltaic power generation;

the method comprises the steps of determining equivalent distributed photovoltaic power generation system model parameters based on the distributed photovoltaic power generation system data of a power supply and distribution area of a 220kV or 330kV transformer substation and based on the physical mechanism characteristics of the equivalent distributed photovoltaic power generation system;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

calculating equivalent motor load model parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

and calculating the distribution network reactive compensation parameters of the distribution power supply area of the 220kV or 330kV transformer substation based on the reactive power data of the distribution power supply area of the 220kV or 330kV transformer substation.

Preferably, the calculating unit is configured to determine a distribution network equivalent impedance calculating method including a distributed photovoltaic power generation integrated load model based on network topology data of a distribution power supply area of a 220kV or 330kV substation, equivalent distributed photovoltaic power generation system data, and power load data of the 220kV or 330kV substation, and calculate a distribution network equivalent impedance including the distributed photovoltaic power generation integrated load model, and includes:

calculating the equivalent impedance of the distribution network according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiWhich is indicative of the current of the load,I_PVkand the photovoltaic power generation current is represented, l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed photovoltaic generator.

Preferably, the calculation unit is configured to calculate parameters of the equivalent distributed photovoltaic power generation system based on an equivalent method of the distributed photovoltaic power generation system, and includes:

and setting n as the number of photovoltaic generators included below a 220kV load node, and acquiring the active output P of each photovoltaic generator i (i is 1.., n)_PViAnd then the actual active power output P of all the photovoltaic generators below the 220kV load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViPercentage N of active output of all photovoltaic generators below a power distribution area where 220kV load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent photovoltaic power generation system is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiOf a constant-dc voltage controller for a photovoltaic generator i (i ═ 1.., n)Measuring a time constant;

integral link coefficient T of constant direct current voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant DC voltage controller of equivalent photovoltaic power generation system_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent photovoltaic power generation system_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent photovoltaic power generation system_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent photovoltaic power generation system for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent photovoltaic power generation system for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent photovoltaic power generation system_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}Is a photovoltaic generator i (i ═ 1.N) setting the active current at the initial moment of finishing the low-voltage ride through;

current setting climbing initial value I of equivalent photovoltaic power generation system_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent photovoltaic power generation system_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent photovoltaic power generation system_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

Preferably, the calculating unit is configured to calculate equivalent static load parameters of the power distribution and supply area of the 220kV or 330kV substation based on the power load data of the power distribution and supply area of the 220kV or 330kV substation, and further includes:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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 α, β, γ, to polynomial load model is based on the sensitivity of the load power to the load terminal voltage:

P₁，P₂…P_nand Q₁，Q₂…Q_nFor the active power and the reactive power of each static load, the corresponding polynomial load model coefficients are respectively P_o1…P_on、a₁…a_n、b₁…b_n、c₁…c_nAnd Q_o1…Q_on、α₁…α_n、β₁…β_n、γ₁…γ_n(ii) a When V is equal to V_oSometimes:

preferably, calculating equivalent motor load model parameters of the power supply area supplied by the 220kV or 330kV substation based on the power load data of the power supply area supplied by the 220kV or 330kV substation, further includes:

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

∑P_cu1＝∑P_n-∑P_emn

S_n＝∑P_cu2/∑P_emn

H＝∑E_energy/(∑P_emn-∑P_cu2)

pemn is rated electromagnetic power of the motor, Temn is rated torque, Sn is rated slip of the rotor, Pn is rated active power, Pcu2 is rotor winding copper loss, Eenergy is kinetic energy;

where ∑ P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged;

calculating electrical parameters of equivalent motor model, including stator resistance R_sStator leakage reactance X_sRotor resistance R_rRotor leakage reactance X_rAnd an excitation reactance X_mSetting the rated phase voltage as Un, and the calculation flow of the electrical parameters is as follows:

(1) let P_{emt_max}＝∑P_{em_max}(ii) a Pent _ max is the total maximum electromagnetic power, and Pem _ max is the maximum electromagnetic power;

(2) let the total stator phase current be

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;

(3) calculating the equivalent impedance Z of an equivalent motor_deq：

R_deq＝real(Z_deq)

X_deq＝imag(Z_deq)

Wherein R is_depIs the equivalent resistance, X, of an equivalent motor_depIs the equivalent reactance of the equivalent motor, j is the imaginary unit of complex number;

(4) calculating X_sAnd X_r：

X_r＝X_s

X is always assumed in this algorithm_r＝X_sAnd X is calculated from the formula_sAnd X_rIs necessarily smaller because the maximum electromagnetic power calculated according to the simplified maximum electromagnetic power formula is larger than the actual maximum electromagnetic power, so that the X is required to be iteratively processed_sAnd X_rCorrecting;

(5) according to the calculated 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_emIs formed, 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:

K_r＝R_deq-R_s

K_x＝X_deq-X_s

(6) according to the obtained R_s，X_s，R_r，X_rAnd X_mThe maximum electromagnetic power is recalculated according to the simplified formula:

(7) calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit:

thevenin equivalent impedance is:

R_dp＝real(Z_dp)

X_dp＝imag(Z_dp)

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:

(8) calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}：

P_{emt_max}＝k_maxiP_{em_max}

(9) Comparison P_{em_maxi}And P_{em_max}The difference of (a):

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}|

if Err_{Pem_max}≥1.0e^-5And (4) returning to the step (4) for recalculation, otherwise, ending the calculation.

Preferably, calculating the distribution network reactive compensation parameters of the distribution and power supply area supplied by the 220kV or 330kV substation based on the reactive power data of the distribution and power supply area supplied by the 220kV or 330kV substation, includes:

reactive compensation Q for calculating 220kV transformer substation power distribution and supply area according to reactive power balance_SC：

-Q_SC＝Q-Q_D-(Q_IM+Q_Z+Q_I+Q_P-Q_PV)

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_PRespectively a static constant impedance reactive load, a static constant current reactive load and a static constant power reactive load; q_PVGenerated for equivalent photovoltaic generatorsReactive power.

The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Claims (10)

1. A load model structure including distributed photovoltaic power generation and a method of determining parameters of the load model, the method comprising:

providing a comprehensive load model structure containing distributed photovoltaic power generation, wherein the comprehensive load model structure comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model;

the method comprises the following steps of providing a method for calculating the equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation, a method for determining the model parameters of an equivalent distributed photovoltaic power generation system, a method for calculating the equivalent static load model parameters, a method for calculating the equivalent motor load model parameters, and a method for calculating the reactive compensation of the distribution network:

providing a distribution network equivalent impedance calculation method of a comprehensive load model containing distributed photovoltaic power generation based on network topology data of a power distribution and supply area of a 220kV or 330kV transformer substation, distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and calculating distribution network equivalent impedance of the comprehensive load model containing distributed photovoltaic power generation;

the method comprises the steps of determining equivalent distributed photovoltaic power generation system model parameters based on the distributed photovoltaic power generation system data of a power supply and distribution area of a 220kV or 330kV transformer substation and based on the physical mechanism characteristics of the equivalent distributed photovoltaic power generation system;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

calculating equivalent motor load model parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

and calculating the distribution network reactive compensation parameters of the distribution power supply area of the 220kV or 330kV transformer substation based on the reactive power data of the distribution power supply area of the 220kV or 330kV transformer substation.

2. The method of claim 1, wherein a distribution network equivalent impedance calculation method comprising a distributed photovoltaic power generation integrated load model is determined based on network topology data of a distribution and power supply area provided by a 220kV or 330kV transformer substation, equivalent distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and the distribution network equivalent impedance comprising the distributed photovoltaic power generation integrated load model is calculated, and the method comprises the following steps:

according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network, calculating the equivalent impedance of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkRepresenting the photovoltaic power generation current, wherein l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, and i is the ith loadAnd a branch, k is a kth distributed photovoltaic generator.

3. The method of claim 1, the calculating an equivalent distributed photovoltaic power generation system parameter based on an equivalent method of a distributed photovoltaic power generation system, comprising:

let n be the number of photovoltaic generators included below the high-voltage load node, obtain the active power P of each photovoltaic generator i (i ═ 1.., n)_PViThe actual active power output P of all the photovoltaic generators below the high-voltage load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViPercentage N of active power output of all photovoltaic generators below a power distribution area where high-voltage load nodes are located_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent distributed photovoltaic power generation system model is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of fixed direct-current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant direct current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, K_udiA scaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent distributed photovoltaic power generation system model for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

voltage value U of equivalent distributed photovoltaic power generation system model for judging exit from low voltage ride through state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent distributed photovoltaic power generation system model_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}An active current set value at the initial moment of the low-voltage ride-through ending of a photovoltaic generator i (i ═ 1., n);

current setting climbing initial value I of equivalent distributed photovoltaic power generation system model_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

4. The method of claim 1, wherein calculating equivalent static load parameters of the power supply area supplied by the 220kV or 330kV substation based on the power load data of the power supply area supplied by the 220kV or 330kV substation, further comprises:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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.

5. The method of claim 1, wherein calculating equivalent motor load model parameters for a 220kV or 330kV substation supplied and distributed power supply area based on power load data for the 220kV or 330kV substation supplied and distributed power supply area, further comprises:

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

∑P_cu1＝∑P_n-∑P_emn

S_n＝∑P_cu2/∑P_emn

H＝∑E_energy/(∑P_emn-∑P_cu2)

pemn is rated electromagnetic power of the motor, Temn is rated torque, Sn is rated slip of the rotor, Pn is rated active power, Pcu2 is rotor winding copper loss, Eenergy is kinetic energy;

where ∑ P_emn-∑P_cu2The rated mechanical power output by the equivalent motor is kept unchanged;

calculating the equivalent impedance Z of an equivalent motor_deq：

R_deq＝real(Z_deq)

X_deq＝imag(Z_deq)

Wherein R is_depIs of equal valueEquivalent resistance of the engine, X_depIs the equivalent reactance of the equivalent motor, j is the imaginary unit of complex number;

calculating X_sAnd X_r：

X_r＝X_s

X is always assumed in this algorithm_r＝X_sAnd X is calculated from the formula_sAnd X_rIs necessarily smaller because the maximum electromagnetic power calculated according to the simplified maximum electromagnetic power formula is larger than the actual maximum electromagnetic power, so that the X is required to be iteratively processed_sAnd X_rCorrecting;

according to the calculated 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_emIs formed, 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:

K_r＝R_deq-R_s

K_x＝X_deq-X_s

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

calculating the actual maximum electromagnetic power under the new parameters according to the Thevenin equivalent circuit:

thevenin equivalent impedance is:

R_dp＝real(Z_dp)

X_dp＝imag(Z_dp)

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:

calculating P_{emt_maxi}And P_{em_maxi}Is corrected for P_{emt_max}：

P_{emt_max}＝k_maxiP_{em_max}

Comparison P_{em_maxi}And P_{em_max}The difference of (a):

Err_{Pem_max}＝|P_{em_max}-P_{em_maxi}|

if Err_{Pem_max}≥1.0e^-5And (4) returning to the step (4) for recalculation, otherwise, ending the calculation.

6. The method of claim 1, wherein calculating distribution network reactive compensation parameters of the distribution and supply area supplied by the 220kV or 330kV substation based on the reactive power data of the distribution and supply area supplied by the 220kV or 330kV substation comprises:

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_PV)

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_PRespectively a static constant impedance reactive load, a static constant current reactive load and a static constant power reactive load; q_PVThe reactive power generated by the equivalent photovoltaic generator.

7. A load model structure including distributed photovoltaic power generation and a system for determining parameters of the load model, the system comprising:

the building unit is used for providing a comprehensive load model structure containing distributed photovoltaic power generation, and the comprehensive load model structure comprises: the method comprises the following steps of (1) distributing network equivalent impedance, a distribution network reactive compensation model, an equivalent static load model, an equivalent motor load model and an equivalent distributed photovoltaic power generation system model;

the determining unit is used for providing a method for calculating equivalent impedance of a distribution network of a comprehensive load model containing distributed photovoltaic power generation, a method for determining equivalent distributed photovoltaic power generation system model parameters, a method for calculating equivalent static load model parameters, a method for calculating equivalent motor load model parameters, and a method for calculating reactive compensation of the distribution network:

the computing unit is used for providing a distribution network equivalent impedance computing method of the comprehensive load model containing the distributed photovoltaic power generation based on network topology data of a power distribution and supply area of a 220kV or 330kV transformer substation, distributed photovoltaic power generation system data and power load data of the 220kV or 330kV transformer substation, and computing the distribution network equivalent impedance of the comprehensive load model containing the distributed photovoltaic power generation;

the method comprises the steps of determining equivalent distributed photovoltaic power generation system model parameters based on the distributed photovoltaic power generation system data of a power supply and distribution area of a 220kV or 330kV transformer substation and based on the physical mechanism characteristics of the equivalent distributed photovoltaic power generation system;

calculating equivalent static load parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

calculating equivalent motor load model parameters of a power supply and distribution area of a 220kV or 330kV transformer substation based on power load data of the power supply and distribution area of the 220kV or 330kV transformer substation;

and calculating the distribution network reactive compensation parameters of the distribution power supply area of the 220kV or 330kV transformer substation based on the reactive power data of the distribution power supply area of the 220kV or 330kV transformer substation.

8. The system of claim 7, wherein the computing unit is configured to determine a distribution network equivalent impedance computing method including a comprehensive load model of distributed photovoltaic power generation based on network topology data of a distribution and power supply area of a 220kV or 330kV substation, equivalent distributed photovoltaic power generation system data, and power load data of the 220kV or 330kV substation, and to compute the distribution network equivalent impedance of the comprehensive load model including distributed photovoltaic power generation, and includes:

according to the fact that the power consumption of the impedance of the distribution network is equal to the sum of the power consumption of each transformer and each distribution line of the distribution network, calculating the equivalent impedance of the distribution network:

Z_Drepresenting the equivalent impedance of the distribution network; p_jRepresenting the active power, Q, of the delivery side of the line or transformer_jIndicating reactive power, U, of distribution line or transformer j delivery terminal_jIndicating the bus voltage, Z, of the delivery side of the line or transformer_jRepresenting transformer and distribution line impedance, I_LiRepresents the load current, I_PVkAnd the photovoltaic power generation current is represented, l is the number of distribution lines or transformer buses, m is the number of load branches, n is the number of distributed photovoltaic generators, i is the ith load branch, and k is the kth distributed photovoltaic generator.

9. The system of claim 7, the computing unit to compute an equivalent distributed photovoltaic power generation system parameter based on an equivalent method of the distributed photovoltaic power generation system, comprising:

let n be the number of photovoltaic generators included below the high-voltage load node, obtain the active power P of each photovoltaic generator i (i ═ 1.., n)_PViThe actual active power output P of all the photovoltaic generators below the high-voltage load node_PVThe sum of the active power outputs of the n photovoltaic generators:

calculating an active power P of each photovoltaic generator i (i ═ 1.., n)_PViOccupying the power supply and distribution area of a high-voltage load nodePercentage of active output N of all photovoltaic generators below_iAs weighting factors for the individual photovoltaic generators;

N_i＝P_PVi/P_PV i＝1,...,n

the capacitor value C of the equivalent distributed photovoltaic power generation system model is as follows:

wherein, C_iA capacitor value for a photovoltaic generator i (i ═ 1.., n);

measurement time constant T of constant direct current voltage controller of equivalent photovoltaic power generation system_muComprises the following steps:

wherein, T_muiA measurement time constant of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of fixed direct-current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, T_udiAn integral link coefficient of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant direct current voltage controller of equivalent distributed photovoltaic power generation system model_udComprises the following steps:

wherein, K_udiScaling factor of a constant dc voltage controller for a photovoltaic generator i (i ═ 1.., n)；

Measurement time constant T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_mPComprises the following steps:

wherein, T_mPiA measurement time constant of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

integral link coefficient T of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, T_usiAn integral link coefficient of a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

proportionality coefficient K of constant alternating voltage controller of equivalent distributed photovoltaic power generation system model_usComprises the following steps:

wherein, K_usiA scaling factor for a constant ac voltage controller for a photovoltaic generator i (i ═ 1.., n);

voltage value U of equivalent distributed photovoltaic power generation system model for judging low voltage ride through state_SLComprises the following steps:

wherein, U_SLiA voltage for the photovoltaic generator i (i ═ 1.., n) to enter a low voltage ride through state;

judging exit low voltage ride through state of equivalent distributed photovoltaic power generation system modelVoltage value U of state_SHComprises the following steps:

wherein, U_SHiA voltage value for the photovoltaic generator i (i ═ 1.., n) that determines to exit the low voltage ride through state;

inverter maximum alternating active output current I of equivalent distributed photovoltaic power generation system model_pmaxComprises the following steps:

wherein, I_pmaxiAn inverter maximum ac active output current for a photovoltaic generator i (i ═ 1.., n);

active current set value I at initial low-voltage ride-through finishing moment of equivalent photovoltaic power generation system_{pd_LVRT}Comprises the following steps:

wherein, I_{pd_LVRTi}An active current set value at the initial moment of the low-voltage ride-through ending of a photovoltaic generator i (i ═ 1., n);

current setting climbing initial value I of equivalent distributed photovoltaic power generation system model_pdR0Comprises the following steps:

wherein, I_pdR0iSetting a climbing initial value for the current of a photovoltaic generator i (i ═ 1.., n);

proportional coefficient K for reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_qComprises the following steps:

wherein, K_qiA scaling factor for the linear adjustment of the reactive current of the photovoltaic generator i (i ═ 1.., n);

action threshold value U of reactive current linear adjustment of equivalent distributed photovoltaic power generation system model_LVRTComprises the following steps:

wherein, U_LVRTiAn action threshold value for the reactive current linear adjustment of the photovoltaic generator i (i ═ 1.., n).

10. The system of claim 7, the computing unit configured to compute equivalent static load parameters for a 220kV or 330kV substation supplied and distributed power supply area based on power load data of the 220kV or 330kV substation supplied and distributed power supply area, further comprising:

establishing a polynomial load model:

P＝P_o[a×(V/V_o)²+b×(V/V_o)+c]

Q＝Q_o[α×(V/V_o)²+β×(V/V_o)+γ]

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.

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