Method and device for determining frequency response of power grid, medium and equipment

Abstract

The invention discloses a power grid frequency response determination method and device, a medium and equipment, and the method comprises the steps: obtaining the original active power, initial voltage and preset load disturbance of a load node, and obtaining the initial total active power and initial total reactive power of the load node after the load disturbance is added to a transmission line where the load node is located; based on the initial voltage and the initial total active power and the initial total reactive power of the load node after the load disturbance is increased, voltage forward-backward substitution processing of the load node is carried out, and the actual voltage of the load node after the load disturbance is increased is obtained; obtaining the actual disturbance of the load node based on the actual voltage of the load node; and inputting the actual disturbance of the load node into a preset frequency response model to obtain a frequency change value of the load node. The actual voltage of the load node is obtained through load flow calculation, the coupling relation between the active power and the voltage fluctuation is considered, the influence of the voltage fluctuation on the frequency change is increased, and the obtained frequency variation is accurate.

Description

Technical Field

[0001] The present invention relates to the field of power grid technology, and in particular to a method, device, medium and equipment for determining power grid frequency response. Background Art

[0002] The frequency response model can intuitively depict the impact of power system disturbances or control strategies on system frequency, and is an important tool for dynamic analysis of power systems. The existing frequency response model is based on the concept of inertial center frequency and uses a single equivalent generator to describe the frequency fluctuation of the entire power system. The classic single-machine equivalent models mainly include the average system frequency (ASF) model and the system frequency response (SFR) model.

[0003] The existing frequency response model uses a single generator to equivalently simulate the frequency response of the entire system. However, the single generator equivalent simulation ignores the coupling relationship between active power and voltage fluctuations. During the analysis process, only the active power and frequency characteristics of the system are considered, and the impact of voltage characteristics on frequency is not taken into account. In fact, voltage fluctuations will have a great impact on the frequency changes of power loads. Therefore, the frequency changes predicted by the existing frequency response model are relatively low in accuracy. Summary of the invention

[0004] In view of this, the present invention provides a method, device, medium and equipment for determining power grid frequency response, the main purpose of which is to solve the problem of low accuracy of frequency change predicted by existing frequency response models.

[0005] According to one aspect of the present application, a method for determining a power grid frequency response is provided, the method comprising:

[0006] Obtaining the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and obtaining the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located;

[0007] Calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added;

[0008] Based on the initial voltage, the initial total active power and the initial total reactive power of the load node after the load disturbance is added, the voltage of the load node is forward-backward processed to obtain the actual voltage of the load node after the load disturbance is added;

[0009] Calculating based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node;

[0010] The actual disturbance of the load node is input into a preset frequency response model to obtain the frequency change value of the load node.

[0011] Optionally, the performing forward and backward processing of the voltage of the load node based on the initial total active power and the initial total reactive power of the load node after the load disturbance is added to obtain the actual voltage of the load node after the load disturbance is added, comprises:

[0012] Calculate the initial apparent power based on the initial total active power and the initial total reactive power of the load node, and calculate the apparent power difference based on the equivalent impedance of the AC line where the load node is located, the initial total active power and the initial total reactive power of the load node;

[0013] Calculating based on the initial apparent power and the apparent power difference to obtain intermediate apparent power, and decomposing the intermediate apparent power to obtain intermediate total active power and intermediate total reactive power;

[0014] Calculating based on the intermediate total active power, the intermediate total reactive power and the equivalent voltage of the AC line where the load node is located, to obtain the back substitution voltage of the load node;

[0015] Calculate based on the back substitution voltage of the load node and the commutation active power to obtain a new total active power of the load node, calculate based on the back substitution voltage of the load node and the commutation reactive power to obtain a new total reactive power of the load node, and judge whether the new total active power and the new total reactive power of the load node meet the convergence condition;

[0016] When the new total active power and the new total reactive power of the load node meet the convergence condition, the back-substitution voltage of the load node is set as the actual voltage of the load node.

[0017] Optionally, after obtaining the new total active power and the new total reactive power of the load node, the method for determining the power grid frequency response further includes:

[0018] When the new total active power and the new total reactive power of the load node do not meet the convergence condition, the new total reactive power of the load node is used as the initial total reactive power of the load node, the new total active power of the load node is used as the initial total active power of the load node, and the back-substitution voltage of the load node is used as the initial voltage of the load node;

[0019] Based on the initial total reactive power, initial total active power and initial voltage of the load node, the new total reactive power and new total active power of the load node are recalculated until the new total active power and new total reactive power of the load node meet the convergence conditions.

[0020] Optionally, the convergence conditions satisfied by the new total active power and the new total reactive power of the load node are: the difference between the new total reactive power of the load node and the initial total reactive power of the load node is less than a power difference threshold and the difference between the new total active power of the load node and the initial total active power of the load node is less than a power difference threshold.

[0021] Optionally, the calculating the actual disturbance of the load node based on the actual voltage, the original active power and the preset disturbance load of the load node includes:

[0022] Based on the actual voltage, original active power and preset disturbance load of the load node, the actual active power of the load node after adding the load disturbance is calculated;

[0023] The difference between the actual active power of the load node after the load disturbance is added and the original active power is taken as the actual disturbance of the load node.

[0024] Optionally, the following method is used to calculate the initial total reactive power of the load node after the load disturbance is added:

[0025]

[0026] Where Q0 is the initial total reactive power of the load node after adding the load disturbance, U0 is the initial voltage, Bc is the equivalent admittance, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station.

[0027] Optionally, when the load disturbance is added on the rectifier side of the converter station, the commutation reactive power is calculated by the following method:

[0028]

[0029] When the load disturbance increases on the inverter side of the converter station, the commutation active power is calculated using the following method:

[0030]

[0031] The commutation active power is calculated using the following method:

[0032]

[0033] Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station, Q I is the reactive power on the inverter side of the converter station, S I is the apparent power on the inverter side of the converter station, P I is the active power on the inverter side of the converter station, U acI is the voltage on the inverter side of the converter station, I d is the current on the inverter side of the converter station, X BI is the leakage reactance of the transformer.

[0034] According to another aspect of the present application, a device for determining a power grid frequency response is provided, comprising:

[0035] A basic data acquisition module is used to obtain the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and to obtain the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the transmission line where the load node is located is added with load disturbance;

[0036] An initial power calculation module, configured to calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and to calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added;

[0037] An actual voltage acquisition module is used to perform forward and backward processing of the voltage of the load node based on a preset voltage, an initial total active power and an initial total reactive power of the load node after adding a load disturbance, so as to obtain an actual voltage of the load node after adding a load disturbance;

[0038] An actual disturbance acquisition module, used to calculate based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node;

[0039] The frequency change value acquisition module is used to input the actual disturbance of the load node into a preset frequency response model to obtain the frequency change value of the load node.

[0040] Optionally, the actual voltage acquisition module is further used for:

[0041] Calculate the initial apparent power based on the initial total active power and the initial total reactive power of the load node, and calculate the apparent power difference based on the equivalent impedance of the AC line where the load node is located, the initial total active power and the initial total reactive power of the load node;

[0042] Calculating based on the initial apparent power and the apparent power difference to obtain intermediate apparent power, and decomposing the intermediate apparent power to obtain intermediate total active power and intermediate total reactive power;

[0043] Calculating based on the intermediate total active power, the intermediate total reactive power and the equivalent voltage of the AC line where the load node is located, to obtain the back substitution voltage of the load node;

[0044] Calculate based on the back substitution voltage of the load node and the commutation active power to obtain a new total active power of the load node, calculate based on the back substitution voltage of the load node and the commutation reactive power to obtain a new total reactive power of the load node, and judge whether the new total active power and the new total reactive power of the load node meet the convergence condition;

[0045] When the new total active power and the new total reactive power of the load node meet the convergence condition, the back-substitution voltage of the load node is set as the actual voltage of the load node.

[0046] Optionally, the actual voltage acquisition module is further used for:

[0047] When the new total active power and the new total reactive power of the load node do not meet the convergence condition, the new total reactive power of the load node is used as the initial total reactive power of the load node, the new total active power of the load node is used as the initial total active power of the load node, and the back-substitution voltage of the load node is used as the initial voltage of the load node;

[0048] Based on the initial total reactive power, initial total active power and initial voltage of the load node, the new total reactive power and new total active power of the load node are recalculated until the new total active power and new total reactive power of the load node meet the convergence conditions.

[0049] Optionally, the convergence conditions satisfied by the new total active power and the new total reactive power of the load node are: the difference between the new total reactive power of the load node and the initial total reactive power of the load node is less than a power difference threshold and the difference between the new total active power of the load node and the initial total active power of the load node is less than a power difference threshold.

[0050] Optionally, the actual disturbance acquisition module is further used for:

[0051] Based on the actual voltage, original active power and preset disturbance load of the load node, the actual active power of the load node after adding the load disturbance is calculated;

[0052] The difference between the actual active power of the load node after the load disturbance is added and the original active power is taken as the actual disturbance of the load node.

[0053] Optionally, the following method is used to calculate the initial total reactive power of the load node after the load disturbance is added:

[0054]

[0055] Where Q0 is the initial total reactive power of the load node after adding the load disturbance, U0 is the initial voltage, Bc is the equivalent admittance, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station.

[0056] Optionally, when the load disturbance is added on the rectifier side of the converter station, the commutation reactive power is calculated by the following method:

[0057]

[0058] When the load disturbance increases on the inverter side of the converter station, the commutation active power is calculated using the following method:

[0059]

[0060] The commutation active power is calculated using the following method:

[0061]

[0062] Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station, Q I is the reactive power on the inverter side of the converter station, S I is the apparent power on the inverter side of the converter station, P I is the active power on the inverter side of the converter station, U acIis the voltage on the inverter side of the converter station, I d is the current on the inverter side of the converter station, X BI is the leakage reactance of the transformer.

[0063] According to another aspect of the present application, a storage medium is provided, wherein at least one executable instruction is stored in the storage medium, and the executable instruction enables a processor to execute operations corresponding to the above-mentioned method for determining the power grid frequency response.

[0064] According to another aspect of the present application, a computer device is provided, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus;

[0065] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned method for determining the power grid frequency response.

[0066] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0067] The present application provides a method, device, equipment and medium for determining the frequency response of a power grid, which obtains the original active power, initial voltage and preset load disturbance of a load node, obtains the commutation active power and commutation reactive power transmitted by the commutation station in the transmission line after the load disturbance is added to the transmission line where the load node is located, calculates the initial total reactive power of the load node after the load disturbance is added based on the original active power, initial voltage and preset load disturbance commutation active power and commutation reactive power of the load node, and performs voltage forward calculation of the load node based on the initial total active power, initial total reactive power and initial voltage of the load node after the load disturbance is added. Through back substitution, the actual voltage of the load node after adding the load disturbance is obtained. The actual disturbance of the load node is calculated based on the actual voltage of the load node, the original active power and the preset disturbance load. The actual disturbance of the load node is input into the preset frequency response model to obtain the frequency change value of the load node. The actual voltage of the load node is obtained through power flow calculation. The actual disturbance is obtained based on the actual voltage. The actual disturbance is input into the preset frequency response model. The coupling relationship between active power and voltage fluctuation is considered, and the influence of voltage fluctuation on frequency change is increased, so that the obtained frequency change is more accurate, thereby improving the prediction accuracy of frequency response.

[0068] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0070] Figure 1 A flow chart of a method for determining a power grid frequency response provided by an embodiment of the present application is shown;

[0071] Figure 2 A diagram showing the relationship between a generator and a load in a method for determining a power grid frequency response provided by an embodiment of the present application;

[0072] Figure 3 A mathematical model diagram of a prime mover of a method for determining a power grid frequency response provided by an embodiment of the present application is shown;

[0073] Figure 4 A model diagram of a speed regulator of a method for determining a power grid frequency response provided by an embodiment of the present application is shown;

[0074] Figure 5 A frequency response model diagram of an AC system on the rectifier / inverter side of a method for determining a power grid frequency response provided in an embodiment of the present application is shown;

[0075] Figure 6 A schematic diagram of an AC system on the rectifier side or inverter side showing a method for determining a power grid frequency response provided by an embodiment of the present application;

[0076] Figure 7 A simple power system diagram equivalent to the rectifier side or the inverter side of a method for determining a power grid frequency response provided by an embodiment of the present application is shown;

[0077] Figure 8 A schematic diagram showing a frequency response model of a method for determining a power grid frequency response provided in an embodiment of the present application is shown;

[0078] Fig. 9 A structural block diagram of a device for determining a power grid frequency response provided by an embodiment of the present application is shown;

[0079] Fig.10 A schematic structural diagram of a computer device provided by an embodiment of the present invention is shown.

[0080] in,

[0081] Fig. 9Middle: 902-basic data acquisition module; 904-initial power calculation module; 906-actual voltage acquisition module; 908-actual disturbance acquisition module; 910-frequency change value acquisition module;

[0082] Fig.10 In it: 1002 - processor; 1004 - communication interface; 1006 - memory; 1008 - communication bus; 1010 - program. DETAILED DESCRIPTION

[0083] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0084] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0085] In order to solve the problem that the frequency change amount predicted by the existing frequency response model is relatively low in accuracy, the embodiment of the present application provides a method for determining the frequency response of a power grid, such as Figure 1 As shown, the method includes:

[0086] 102: obtaining the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and obtaining the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located;

[0087] 104: Calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added;

[0088] 106: Based on the initial voltage, the initial total active power and the initial total reactive power of the load node after the load disturbance is added, the voltage of the load node is forward-backward processed to obtain the actual voltage of the load node after the load disturbance is added;

[0089] 108: Calculate based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node;

[0090] 110: Input the actual disturbance of the load node into a preset frequency response model to obtain a frequency change value of the load node.

[0091] Specifically, the voltage fluctuation process under large power shortage has a significant impact on the entire process of frequency dynamic response, such as RoCoF (frequency change rate), minimum frequency, and steady-state frequency. The impact of voltage characteristics on frequency cannot be ignored in frequency response modeling and quantitative evaluation. Since the voltage distribution of each node in the network and the fluctuation characteristics under large power shortage are different, that is, the voltage is dispersed, it is more difficult to characterize the impact of voltage characteristics in the low-order equivalent frequency response model. Therefore, the existing frequency response equivalent modeling only considers the active-frequency characteristics of the system during the analysis process, and has not yet taken into account the impact of voltage characteristics.

[0092] The initial frequency response model assumes that the load model is insensitive to frequency changes, that is, the frequency damping coefficient D = 0, then the relationship between the generator and the load is expressed as Figure 2 Block diagram representation of . Figure 2 When the generator model in does not consider the influence of time and space distribution on frequency response, the multi-machine system can be simplified to an equivalent generator, that is, the system inertia can be equivalent according to the following formula: Among them, H i , S i are the inertia constant and capacity of the i-th generator respectively.

[0093] The prime mover in the frequency response model uses a tandem-compound single-reheat steam turbine model (Tandem-Compound Single-Reheat Steam System), and its mathematical model is as follows: Figure 3 The speed regulator in the frequency response model uses the DEH speed regulator model (Digital Electro-Hydraulic controls of Westinghouse) of Westinghouse Electric Company, and its mathematical model is as follows Figure 4 As shown. Since the system uses LCC-HVDC (line converter-based high-voltage direct current transmission technology) as the inter-regional interconnection line, it can be considered that the inter-regional frequency is decoupled, and the frequency response models of the rectifier and inverter AC systems can be built separately. The preset frequency response model obtained based on the above content is as follows Figure 5 As shown, ΔP is the load change of the load node and Δf is the frequency change.

[0094] When the load on the rectifier side is disturbed, the active power transmitted by LCC-HVDC will basically not change because the inverter side is not disturbed, but the reactive power absorbed by the rectifier station will also change because the AC voltage will change. When the load disturbance occurs on the rectifier side, LCC-HVDC can be equivalent to a load with unchanged active power and reactive power that meets the first preset rule. After the load disturbance occurs on the inverter side, the DC power of the inverter station will change, which is related to the AC voltage and the trigger angle of the inverter side. When the load on the inverter side is disturbed, since the DC current will not change, the active power of LCC-HVDC is regarded as a load that has a linear function relationship with the voltage and the reactive power meets the second preset rule.

[0095] Obtain the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node when no load disturbance is added. Add a load node to the transmission line where the load node is located. The load node can be added on the rectifier side or the inverter side. According to the above rules, the commutation reactive power and commutation active power corresponding to the converter station of the transmission line where the load node is located are calculated. The sum of the original active power of the load node, the preset load disturbance and the commutation active power is taken as the initial total active power of the load node after adding the load disturbance; calculate the reactive power (U0) of the load node based on the initial voltage and equivalent admittance. 2 *B C , U0 is the initial voltage, B C is the equivalent admittance), and then the sum of the reactive power of the load node and the commutation reactive power is taken as the initial total reactive power of the load node after the load disturbance is added.

[0096] After the preset frequency response model load is disturbed, the node voltage of the system will change. When the load disturbance occurs on the inverter side, the DC power of LCC-HVDC will also change, further increasing the error of the initial frequency response model. In order to reduce the error of the frequency response model, it is necessary to incorporate the changes in voltage and LCC-HVDC (high-voltage direct current transmission mode) into the model. The frequency change of the power system involves the change in the motion state of the generator rotor, and the change process is relatively long. It is an electromechanical process that lasts for several seconds. In contrast, the voltage change is an electromagnetic process, and its change time is much smaller than that of the frequency change. In order to simplify the problem, if the voltage change is to be included in the frequency response model of the system, the voltage change is more suitable to be presented as a static process rather than a dynamic process. The reason for the error in the initial frequency response model is that the voltage fluctuation causes the load change to be unequal to the preset change value. Power flow calculation is an important tool for voltage stability analysis. After the load disturbance is preset, the accurate actual voltage value of the system can be obtained according to the transmission line information of the power grid, and then the actual load change of the system can be further calculated. Assume that in an asynchronous interconnected system, the AC network on the rectifier and inverter side is as follows Figure 6As shown, where L1 / L2 is the load on the rectifier or inverter side, C1 / C2 is the parallel capacitor, and SLCC is the power absorbed by the converter station, the system power flow calculation can be achieved by forward-backward substitution. To simplify the calculation, Figure 6 The AC system can be further simplified as Figure 7 In the simple power system shown, generators G1 (or G3) and G2 (G4) are equivalent to a voltage source Eeq, the impedance of the line and transformer is equivalent to an impedance Zeq, and the power of the load, reactive compensation device, and LCC-HVDC are all equivalent to an equivalent load SL.

[0097] Assume that the total power of the load node is the power emitted by the equivalent power source Eeq of the transmission line. According to the power loss formula, calculate the power loss of the equivalent impedance Zeq in the transmission line, calculate the power emitted by the equivalent power source Eeq, calculate the voltage value of the load node according to the voltage drop calculation formula, and then judge whether the convergence condition is met according to the voltage value of the load node. If the convergence condition is met, the voltage value of the load node is the actual voltage of the load node. Calculate according to the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node, input the actual disturbance of the load node into the preset frequency response model, and obtain the frequency change value of the load node, such as Figure 8 shown.

[0098] The present application provides a method for determining the frequency response of a power grid. Compared with the prior art, the original active power, initial voltage, and preset load disturbance of the load node are obtained, and the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located are obtained. Based on the original active power, initial voltage, preset load disturbance commutation active power and commutation reactive power of the load node, the initial total reactive power of the load node after the load disturbance is added is calculated, and based on the initial total active power, initial total reactive power and initial voltage of the load node after the load disturbance is added, the voltage of the load node is forwarded. Through back substitution, the actual voltage of the load node after adding the load disturbance is obtained. The actual disturbance of the load node is calculated based on the actual voltage of the load node, the original active power and the preset disturbance load. The actual disturbance of the load node is input into the preset frequency response model to obtain the frequency change value of the load node. The actual voltage of the load node is obtained through power flow calculation. The actual disturbance is obtained based on the actual voltage. The actual disturbance is input into the preset frequency response model. The coupling relationship between active power and voltage fluctuation is considered, and the influence of voltage fluctuation on frequency change is increased, so that the obtained frequency change is more accurate, thereby improving the prediction accuracy of frequency response.

[0099] In one embodiment, based on the initial total active power and the initial total reactive power of the load node after the load disturbance is added, the voltage of the load node is forwarded and backward processed to obtain the actual voltage of the load node after the load disturbance is added, including:

[0100] The initial apparent power is calculated based on the initial total active power and the initial total reactive power of the load node, and the apparent power difference is calculated based on the equivalent impedance of the AC line where the load node is located, the initial total active power and the initial total reactive power of the load node;

[0101] Calculate based on the initial apparent power and the apparent power difference to obtain the intermediate apparent power, decompose the intermediate apparent power to obtain the intermediate total active power and the intermediate total reactive power;

[0102] The back-substitution voltage of the load node is obtained by calculating based on the intermediate total active power, the intermediate total reactive power and the equivalent voltage of the AC line where the load node is located;

[0103] Based on the back substitution voltage and commutation active power of the load node, the new total active power of the load node is calculated. Based on the back substitution voltage and commutation reactive power of the load node, the new total reactive power of the load node is calculated. It is judged whether the new total active power and the new total reactive power of the load node meet the convergence conditions.

[0104] When the new total active power and the new total reactive power of the load node meet the convergence condition, the back-substitution voltage of the load node is set as the actual voltage of the load node.

[0105] Specifically, the initial total active power is taken as the real part of the initial apparent power, and the initial total reactive power is taken as the imaginary part of the initial apparent power to obtain the initial apparent power. The apparent power difference is calculated by the following formula: ΔS = (P 20 2 +Q 20 2 )*Zeq / U 20 2 , where P 20 is the initial total active power of the load node, Q 20 is the initial total reactive power of the load node, U 20 is the initial voltage of the load node, and Zeq is the equivalent impedance of the AC line where the load node is located.

[0106] The sum of the initial apparent power and the apparent power difference is taken as the intermediate apparent power, the intermediate apparent power is decomposed, the real part of the intermediate apparent power is taken as the intermediate total active power, and the imaginary part of the intermediate apparent power is taken as the intermediate total reactive power.

[0107] The longitudinal component of the voltage drop is calculated using the following formula:

[0108] zongU1=(P1*real(Z eq )+Q1*imag(Z eq )) / E1

[0109] Among them, zongU1 is the longitudinal component of voltage drop, P1 is the total active power in the middle, real(Z eq ) is the real part of the equivalent impedance, Q1 is the total intermediate reactive power, imag(Z eq ) is the imaginary part of the equivalent impedance, and E1 is the equivalent voltage.

[0110] The transverse component of the voltage drop is calculated using the following formula:

[0111] hengU1=(P1*imag(Z eq )-Q1*real(Z eq )) / E1

[0112] Among them, hengU1 is the transverse component of voltage drop.

[0113] Calculate the back-substitution constant voltage of the load node based on the horizontal and vertical components of the voltage drop:

[0114] U 21 =sqrt((E1-zongU1) 2 +(hengU1) 2 ).

[0115] The new total active power of the load node is calculated using the following formula:

[0116] P 21 =sqrt(3)*U 21 2 / R+P R

[0117] Where R = sqrt(3)*U0 2 / (P L +ΔP), P L is the original active power, ΔP is the preset load disturbance, P R is the commutation active power.

[0118] The new total reactive power of the load node is calculated using the following formula:

[0119]

[0120] If the new total active power and new total reactive power of the load node do not meet the convergence conditions, the new total reactive power of the load node is used as the initial total reactive power of the load node, the new total active power of the load node is used as the initial total active power of the load node, and the back-substitution voltage of the load node is used as the initial voltage of the load node;

[0121] Based on the initial total reactive power, initial total active power and initial voltage of the load node, the new total reactive power and new total active power of the load node are recalculated until the new total active power and new total reactive power of the load node meet the convergence conditions.

[0122] If the new total active power and the new total reactive power of the load node meet the convergence conditions, the back-substitution voltage of the load node is the actual voltage of the load node.

[0123] In one embodiment of the present invention, the convergence conditions satisfied by the new total active power and the new total reactive power of the load node are: the difference between the new total reactive power of the load node and the initial total reactive power of the load node is less than the power difference threshold and the difference between the new total active power of the load node and the initial total active power of the load node is less than the power difference threshold.

[0124] In one embodiment, the actual disturbance of the load node is calculated based on the actual voltage of the load node, the original active power and the preset disturbance load, including:

[0125] Based on the actual voltage of the load node, the original active power and the preset disturbance load, the actual active power of the load node after the load disturbance is added is calculated;

[0126] The difference between the actual active power of the load node after adding the load disturbance and the original active power is taken as the actual disturbance of the load node.

[0127] Specifically, the following formula is used to calculate the actual active power of the load node after adding the load disturbance:

[0128] P L '=(P0+ΔP)*f(U2)

[0129] Among them, P L ' is the actual active power of the load node after adding the load disturbance, P0 is the original active power, ΔP is the preset load disturbance, and U2 is the actual voltage of the load node after adding the load disturbance.

[0130] Specifically, the following method is used to calculate the initial total reactive power of the load node after the load disturbance is added:

[0131]

[0132] Among them, Q0 is the initial total reactive power of the load node after adding the load disturbance, U0 is the initial voltage, Bc is the equivalent admittance, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station.

[0133] In one embodiment, when the load on the rectifier side is disturbed, the active power transmitted by the LCC-HVDC will basically not change because the inverter side is not disturbed, but the reactive power absorbed by the rectifier station will also change because the AC voltage will change. Therefore, when the load disturbance occurs on the rectifier side, the LCC-HVDC can be equivalent to a load with unchanged active power and reactive power that satisfies the following formula.

[0134]

[0135] Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station.

[0136] After a load disturbance occurs on the inverter side, the DC power of the inverter station will change, which is related to the AC voltage and the trigger angle on the inverter side. The DC voltage on the inverter side satisfies the following formula: Since the inverter side adopts fixed γ control and the thyristor trigger angle satisfies β=μ+γ, if γ is considered unchanged, then Δβ=Δμ, where μ and γ are the commutation overlap angle and arc extinction angle of the inverter station respectively. According to relevant regulations, the absolute value of the positive and negative deviations of the power supply voltage of 220kV and above shall not exceed 10% of the rated voltage. In the multiple simulations in this paper, the load node voltage has never dropped by 5%, so it can be assumed that the AC voltage does not change by more than 5%. When the AC voltage is ±5%, substitute the variables into It can be obtained that the range of μ is 6.0917°-6.6875°. Since cosβ=cos(μ+γ), we finally get Δ(cosβ)=-0.0036~0.0031; since the DC current will not change, according to And Δ(cosβ)=-0.0036~0.0031, the change of β causes less than 0.4% change in AC voltage, which can be ignored. Therefore, the active power of LCC-HVDC can be regarded as a linear function of voltage, and we can get Accordingly, the reactive power absorbed by the inverter station can be obtained as

[0137] When the load disturbance is added to the inverter side of the converter station, the following method is used to calculate the commutation active power:

[0138]

[0139] The commutation active power is calculated using the following method:

[0140]

[0141] Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station, Q I is the reactive power on the inverter side of the converter station, S I is the apparent power on the inverter side of the converter station, P I is the active power on the inverter side of the converter station, U acI is the voltage on the inverter side of the converter station, I d is the current on the inverter side of the converter station, X BI is the leakage reactance of the transformer.

[0142] Furthermore, as a response to the above Figure 1 In order to realize the method shown in the figure, an embodiment of the present invention provides a device for determining the frequency response of a power grid, such as Fig. 9 As shown, the device comprises:

[0143] The basic data acquisition module 902 is used to obtain the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and obtain the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located;

[0144] The initial power calculation module 904 is used to calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and to calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added;

[0145] The actual voltage acquisition module 906 is used to perform forward and backward processing of the voltage of the load node based on the initial voltage, the initial total active power and the initial total reactive power of the load node after the load disturbance is added, so as to obtain the actual voltage of the load node after the load disturbance is added;

[0146] The actual disturbance acquisition module 908 is used to calculate based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node;

[0147] The frequency change value acquisition module 910 is used to input the actual disturbance of the load node into a preset frequency response model to obtain the frequency change value of the load node.

[0148] The present application provides a device for determining the frequency response of a power grid. Compared with the prior art, the device obtains the original active power, initial voltage, and preset load disturbance of the load node, obtains the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located, calculates the initial total reactive power of the load node after the load disturbance is added based on the original active power, initial voltage, preset load disturbance commutation active power and commutation reactive power of the load node, and performs voltage forward calculation of the load node based on the initial total active power, initial total reactive power and initial voltage of the load node after the load disturbance is added. Through back substitution, the actual voltage of the load node after adding the load disturbance is obtained. The actual disturbance of the load node is calculated based on the actual voltage of the load node, the original active power and the preset disturbance load. The actual disturbance of the load node is input into the preset frequency response model to obtain the frequency change value of the load node. The actual voltage of the load node is obtained through power flow calculation. The actual disturbance is obtained based on the actual voltage. The actual disturbance is input into the preset frequency response model. The coupling relationship between active power and voltage fluctuation is considered, and the influence of voltage fluctuation on frequency change is increased, so that the obtained frequency change is more accurate, thereby improving the prediction accuracy of frequency response.

[0149] In one embodiment, the actual voltage acquisition module is further used for:

[0150] The initial apparent power is calculated based on the initial total active power and the initial total reactive power of the load node, and the apparent power difference is calculated based on the equivalent impedance of the AC line where the load node is located, the initial total active power and the initial total reactive power of the load node;

[0151] Calculate based on the initial apparent power and the apparent power difference to obtain the intermediate apparent power, decompose the intermediate apparent power to obtain the intermediate total active power and the intermediate total reactive power;

[0152] The back-substitution voltage of the load node is obtained by calculating based on the intermediate total active power, the intermediate total reactive power and the equivalent voltage of the AC line where the load node is located;

[0153] Based on the back substitution voltage and commutation active power of the load node, the new total active power of the load node is calculated. Based on the back substitution voltage and commutation reactive power of the load node, the new total reactive power of the load node is calculated. It is judged whether the new total active power and the new total reactive power of the load node meet the convergence conditions.

[0154] When the new total active power and the new total reactive power of the load node meet the convergence condition, the back-substitution voltage of the load node is set as the actual voltage of the load node.

[0155] In one embodiment, the actual voltage acquisition module is further used for:

[0156] When the new total active power and the new total reactive power of the load node do not meet the convergence conditions, the new total reactive power of the load node is used as the initial total reactive power of the load node, the new total active power of the load node is used as the initial total active power of the load node, and the back-substitution voltage of the load node is used as the initial voltage of the load node;

[0157] Based on the initial total reactive power, initial total active power and initial voltage of the load node, the new total reactive power and new total active power of the load node are recalculated until the new total active power and new total reactive power of the load node meet the convergence conditions.

[0158] In one embodiment, the convergence conditions satisfied by the new total active power and the new total reactive power of the load node are: the difference between the new total reactive power of the load node and the initial total reactive power of the load node is less than the power difference threshold and the difference between the new total active power of the load node and the initial total active power of the load node is less than the power difference threshold.

[0159] In one embodiment, the actual disturbance acquisition module is further used to:

[0160] Based on the actual voltage of the load node, the original active power and the preset disturbance load, the actual active power of the load node after the load disturbance is added is calculated;

[0161] The difference between the actual active power of the load node after adding the load disturbance and the original active power is taken as the actual disturbance of the load node.

[0162] In one embodiment, the following method is used to calculate the initial total reactive power of the load node after the load disturbance is added:

[0163]

[0164] Among them, Q0 is the initial total reactive power of the load node after adding the load disturbance, U0 is the initial voltage, Bc is the equivalent admittance, S R is the apparent power on the rectifier side of the converter station, PdR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station.

[0165] In one embodiment, when the load disturbance is added on the rectifier side of the converter station, the following method is used to calculate the commutation reactive power:

[0166]

[0167] When the load disturbance is added to the inverter side of the converter station, the following method is used to calculate the commutation active power:

[0168]

[0169] The commutation active power is calculated using the following method:

[0170]

[0171] Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station, Q I is the reactive power on the inverter side of the converter station, S I is the apparent power on the inverter side of the converter station, P I is the active power on the inverter side of the converter station, U acI is the voltage on the inverter side of the converter station, I d is the current on the inverter side of the converter station, X BI is the leakage reactance of the transformer.

[0172] According to an embodiment of the present invention, a storage medium is provided, wherein the storage medium stores at least one executable instruction, and the computer executable instruction can execute the method for determining the power grid frequency response in any of the above method embodiments.

[0173] Fig.10 A schematic diagram of the structure of a computer device provided according to an embodiment of the present invention is shown. The specific embodiment of the present invention does not limit the specific implementation of the computer device.

[0174] like Fig.10As shown, the computer device may include: a processor (processor) 1002 , a communication interface (Communications Interface) 1004 , a memory (memory) 1006 , and a communication bus 1008 .

[0175] The processor 1002 , the communication interface 1004 , and the memory 1006 communicate with each other via a communication bus 1008 .

[0176] The communication interface 1004 is used to communicate with other devices such as clients or other servers.

[0177] The processor 1002 is used to execute the program 1010, and specifically can execute the relevant steps in the above-mentioned embodiment of the method for determining the frequency response of the power grid.

[0178] Specifically, the program 1010 may include program codes, which include computer operation instructions.

[0179] The processor 1002 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention. The one or more processors included in the computer device may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0180] The memory 1006 is used to store the program 1010. The memory 1006 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0181] The program 1010 may be specifically used to enable the processor 1002 to perform the following operations:

[0182] The original active power, initial voltage, equivalent admittance and preset load disturbance of the load node are obtained, and the commutation active power and commutation reactive power transmitted by the converter station in the transmission line are obtained after the load disturbance is added to the transmission line where the load node is located;

[0183] Based on the original active power, the preset load disturbance and the commutation active power, the initial total active power of the load node after the load disturbance is added is calculated; based on the initial voltage, the equivalent admittance and the commutation reactive power, the initial total reactive power of the load node after the load disturbance is added is calculated;

[0184] Based on the initial total active power and initial total reactive power of the load node after the load disturbance is added, the voltage of the load node is forward-backward processed to obtain the actual voltage of the load node after the load disturbance is added;

[0185] The actual disturbance of the load node is obtained by calculating based on the actual voltage of the load node, the original active power and the preset disturbance load;

[0186] The actual disturbance of the load node is input into the preset frequency response model to obtain the frequency change value of the load node.

[0187] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices. In one embodiment, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0188] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A method for determining a power grid frequency response, characterized in that: include: Obtaining the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and obtaining the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the load disturbance is added to the transmission line where the load node is located; Calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added; Based on the initial voltage, the initial total active power and the initial total reactive power of the load node after the load disturbance is added, the voltage of the load node is forward-backward processed to obtain the actual voltage of the load node after the load disturbance is added; Calculating based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node; The actual disturbance of the load node is input into a preset frequency response model to obtain the frequency change value of the load node.

2. The method for determining the power grid frequency response according to claim 1, characterized in that: The step of performing forward and backward processing of the voltage of the load node based on the initial total active power and the initial total reactive power of the load node after the load disturbance is added to obtain the actual voltage of the load node after the load disturbance is added includes: Calculate the initial apparent power based on the initial total active power and the initial total reactive power of the load node, and calculate the apparent power difference based on the equivalent impedance of the AC line where the load node is located, the initial total active power and the initial total reactive power of the load node; Calculating based on the initial apparent power and the apparent power difference to obtain intermediate apparent power, and decomposing the intermediate apparent power to obtain intermediate total active power and intermediate total reactive power; Calculating based on the intermediate total active power, the intermediate total reactive power and the equivalent voltage of the AC line where the load node is located, to obtain the back substitution voltage of the load node; Calculate based on the back substitution voltage of the load node and the commutation active power to obtain a new total active power of the load node, calculate based on the back substitution voltage of the load node and the commutation reactive power to obtain a new total reactive power of the load node, and judge whether the new total active power and the new total reactive power of the load node meet the convergence condition; When the new total active power and the new total reactive power of the load node meet the convergence condition, the back-substitution voltage of the load node is set as the actual voltage of the load node.

3. The method for determining the power grid frequency response according to claim 2, characterized in that: After obtaining the new total active power and the new total reactive power of the load node, the method for determining the power grid frequency response further includes: When the new total active power and the new total reactive power of the load node do not meet the convergence condition, the new total reactive power of the load node is used as the initial total reactive power of the load node, the new total active power of the load node is used as the initial total active power of the load node, and the back-substitution voltage of the load node is used as the initial voltage of the load node; Based on the initial total reactive power, initial total active power and initial voltage of the load node, the new total reactive power and new total active power of the load node are recalculated until the new total active power and new total reactive power of the load node meet the convergence condition.

4. The method for determining the power grid frequency response according to claim 2 or 3, characterized in that: The convergence conditions satisfied by the new total active power and the new total reactive power of the load node are: the difference between the new total reactive power of the load node and the initial total reactive power of the load node is less than the power difference threshold and the difference between the new total active power of the load node and the initial total active power of the load node is less than the power difference threshold.

5. The method for determining the power grid frequency response according to claim 1, characterized in that: The calculating the actual disturbance of the load node based on the actual voltage, the original active power and the preset disturbance load of the load node includes: Based on the actual voltage, original active power and preset disturbance load of the load node, the actual active power of the load node after adding the load disturbance is calculated; The difference between the actual active power of the load node after the load disturbance is added and the original active power is taken as the actual disturbance of the load node.

6. The method for determining the power grid frequency response according to any one of claims 1 to 5, characterized in that: The initial total reactive power of the load node after adding the load disturbance is calculated using the following method: Where Q0 is the initial total reactive power of the load node after adding the load disturbance, U0 is the initial voltage, Bc is the equivalent admittance, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station.

7. The method for determining the power grid frequency response according to any one of claims 1 to 5, characterized in that: When the load disturbance is added to the rectifier side of the converter station, the commutation reactive power is calculated by the following method: When the load disturbance increases on the inverter side of the converter station, the commutation active power is calculated using the following method: The commutation active power is calculated using the following method: Among them, Q dR is the reactive power on the rectifier side of the converter station, S R is the apparent power on the rectifier side of the converter station, P dR is the active power on the rectifier side of the converter station, U acR is the voltage on the rectifier side of the converter station, I dR is the current on the rectifier side of the converter station, Q I is the reactive power on the inverter side of the converter station, S I is the apparent power on the inverter side of the converter station, P I is the active power on the inverter side of the converter station, U acI is the voltage on the inverter side of the converter station, I d is the current on the inverter side of the converter station, X BI is the leakage reactance of the transformer.

8. A device for determining a power grid frequency response, characterized in that: include: A basic data acquisition module is used to obtain the original active power, initial voltage, equivalent admittance and preset load disturbance of the load node, and to obtain the commutation active power and commutation reactive power transmitted by the converter station in the transmission line after the transmission line where the load node is located is added with load disturbance; An initial power calculation module, configured to calculate based on the original active power, the preset load disturbance and the commutation active power to obtain the initial total active power of the load node after the load disturbance is added, and to calculate based on the initial voltage, the equivalent admittance and the commutation reactive power to obtain the initial total reactive power of the load node after the load disturbance is added; An actual voltage acquisition module, used to perform forward and backward processing of the voltage of the load node based on the initial voltage, the initial total active power and the initial total reactive power of the load node after the load disturbance is added, so as to obtain the actual voltage of the load node after the load disturbance is added; An actual disturbance acquisition module, used to calculate based on the actual voltage of the load node, the original active power and the preset disturbance load to obtain the actual disturbance of the load node; The frequency change value acquisition module is used to input the actual disturbance of the load node into a preset frequency response model to obtain the frequency change value of the load node.

9. A storage medium, wherein at least one executable instruction is stored in the storage medium, and the executable instruction enables a processor to perform operations corresponding to the method for determining a power grid frequency response according to any one of claims 1 to 7.

10. A computer device comprising: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the method for determining the power grid frequency response according to any one of claims 1-7.

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