Simulation modeling system, method and device, electronic equipment and storage medium

Abstract

The embodiment of the invention provides a simulation modeling system, method and device, electronic equipment and a storage medium, and the simulation modeling system is applied to a large-scale photovoltaic power station, and comprises a photovoltaic array, a photovoltaic array for equivalent processing, an AC bus, an MG system, a step-up transformer and a sending-out line. Wherein the photovoltaic array and the equivalent photovoltaic array are connected in parallel and then are sequentially connected with an alternating current bus, an MG system, a step-up transformer and a sending-out circuit, the photovoltaic array comprises a photovoltaic unit, a direct current step-up unit, an inversion unit, a box transformer substation, a collection circuit and a power grid which are sequentially connected, and array-level equivalent processing is carried out on the photovoltaic unit. The method is suitable for topology and electromagnetic transient modeling simulation of a large-scale photovoltaic power station containing MG system access, and the method is suitable for simulation of the large-scale photovoltaic power station containing MG system access.

Description

Technical Field

[0001] The present application relates to the field of power simulation technology, and in particular to a simulation modeling system, method, device, electronic equipment and storage medium. Background Art

[0002] The large-scale access of new energy sources has gradually reduced the stability of the power system. In order to cope with the stability of the new energy power grid, the industry has proposed corresponding solutions, such as virtual synchronous machines, droop control, virtual inertia, etc. These technical solutions have also improved the stability of the power grid, but the widespread access of power electronics has inevitably caused oscillations, or when dealing with serious faults, the converter may be disconnected from the grid due to large fault currents, etc. The above problems show that the converter cannot provide support for the power grid similar to that of the synchronous machine.

[0003] In order to overcome the shortcomings of power electronic converters and improve the operational stability of new energy power grids more effectively and directly, the industry has proposed a grid-connected technology based on series synchronous machines, referred to as MG grid-connected in this application. This grid-connected technology can enable new energy units to have real rotational inertia, damping and reactive support capabilities. Therefore, if this technology is applied to photovoltaic stations, it is expected to improve the stability of new energy stations.

[0004] Before applying this technology, it is essential to conduct system simulation experiments, especially electromagnetic transient simulation plays an important role in transient stability analysis of power electronic power systems. However, the current MG grid-connected technology is mostly focused on the simulation analysis of single-machine systems, and no systematic research has been conducted on the simulation analysis of large-scale photovoltaic power stations. Summary of the invention

[0005] In view of the above problems, the present application provides a simulation modeling system, method, device, electronic device and storage medium, which are suitable for topological and electromagnetic transient modeling and simulation of large-scale photovoltaic power stations with MG system access, and proposes array-level and site-level model simplification methods to facilitate and accelerate the electromagnetic transient simulation of MG systems in large power grids.

[0006] In a first aspect, an embodiment of the present application provides a simulation modeling system, which is applied to a large-scale photovoltaic power station, and is characterized in that it includes: a photovoltaic array, an equivalently processed photovoltaic array, an AC bus, an MG system, a step-up transformer, and a transmission line; wherein,

[0007] The photovoltaic array and the photovoltaic array after being connected in parallel are connected in sequence to the AC bus, the MG system, the step-up transformer and the transmission line;

[0008] The photovoltaic array includes a photovoltaic unit, a DC boost unit, an inverter unit, a box transformer, a collection line and a power grid connected in sequence;

[0009] The photovoltaic unit is processed at the array level, and the photovoltaic array is processed at the station level to perform simulation.

[0010] In a second aspect, an embodiment of the present application provides a simulation modeling method, which is applied to the simulation modeling system, and the method includes:

[0011] Obtaining a terminal voltage frequency difference between a synchronous generator and a synchronous motor in the MG system;

[0012] Calculating the power angle of the MG system based on the generator-end voltage-frequency difference;

[0013] Modeling a photovoltaic array with equivalent processing based on the array-level equivalent processing and the station-level equivalent processing, and calculating a target power angle corresponding to the total output power of the photovoltaic array and the photovoltaic array after equivalent processing;

[0014] The operations of the synchronous generator and the synchronous motor are adjusted based on the target power angle and the power angle.

[0015] In a third aspect, an embodiment of the present application provides a simulation modeling device, which is applied to the simulation modeling system, and the device includes:

[0016] An acquisition module, used for acquiring a terminal voltage frequency difference between a synchronous generator and a synchronous motor in the MG system;

[0017] A calculation module, used for calculating the power angle of the MG system based on the machine-end voltage-frequency difference;

[0018] A modeling and calculation module, for modeling a photovoltaic array with equivalent processing based on the array-level equivalent processing and the station-level equivalent processing, and calculating a target power angle corresponding to the total output power of the photovoltaic array and the photovoltaic array after equivalent processing;

[0019] An adjustment module is used to adjust the operation of the synchronous generator and the synchronous motor based on the target power angle and the power angle.

[0020] In a fourth aspect, an embodiment of the present application provides an electronic device, comprising: at least one processor and a memory; the processor is used to execute a computer program stored in the memory to implement the simulation modeling method introduced in any implementation manner of the second aspect.

[0021] In the fifth aspect, an embodiment of the present application provides a computer storage medium, which stores one or more programs, and the one or more programs can be executed by the electronic device as introduced in the fourth aspect to implement the simulation modeling method as introduced in any implementation method of the second aspect.

[0022] A simulation modeling system, method, device, electronic device and storage medium provided in the embodiments of the present application are applied to large-scale photovoltaic power stations, including: a photovoltaic array, an equivalently processed photovoltaic array, an AC bus, an MG system, a step-up transformer and a transmission line; wherein the photovoltaic array is connected in parallel with the equivalent photovoltaic array and then connected to the AC bus, the MG system, the step-up transformer and the transmission line in sequence; the photovoltaic array includes a photovoltaic unit, a DC step-up unit, an inverter unit, a box transformer, a collection line and a power grid connected in sequence, the photovoltaic unit adopts array-level equivalent processing, and the photovoltaic array adopts site-level equivalent processing for simulation modeling, and provides a generalized electromagnetic transient modeling method for photovoltaic power stations containing MG systems, which is convenient for stability simulation research of MG systems connected to photovoltaic power stations.

[0023] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The scope of the present disclosure may be better understood by reading the following detailed description of exemplary embodiments in conjunction with the accompanying drawings. The drawings included are:

[0025] Figure 1 A schematic diagram of a photovoltaic power station grid-connected topology diagram including an MG system proposed in an embodiment of the present application is shown;

[0026] Figure 2 A schematic diagram of a station-level photovoltaic array equivalent structure proposed in an embodiment of the present application is shown;

[0027] Figure 3 A schematic diagram of a photovoltaic array consistency assessment method proposed in an embodiment of the present application is shown;

[0028] Figure 4 A control principle diagram of a DC boost converter and an inverter proposed in an embodiment of the present application is shown;

[0029] Figure 5 A schematic diagram of a simulation modeling method proposed in an embodiment of the present application is shown;

[0030] Figure 6 A structural block diagram of a simulation modeling device proposed in an embodiment of the present application is shown;

[0031] Figure 7 A structural block diagram of an electronic device for executing a simulation modeling method according to an embodiment of the present application is shown;

[0032] Figure 8A computer-readable storage medium for storing or carrying a simulation modeling method according to an embodiment of the present application is shown.

[0033] Reference numerals:

[0034] 1-PV array; 101-PV unit; 102-DC boost unit; 103-inverter unit; 104-box transformer; 105-collector line; 106-DC bus; 2-PV array after equalization; 201-PV unit after equalization; 202-DC boost unit after equalization; 203-inverter unit after equalization; 204-box transformer after equalization; 205-collector line after equalization; 206-controlled current source; 207-input signal; 208-MPPT module; 209-first PI controller; 210-second PI controller; 3-MG system; 4-boost transformer; 5-transmission line; 6-grid; 7-AC bus. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0036] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0037] If similar descriptions of "first / second / third" appear in the application documents, the following instructions are added. In the following description, the terms "first / second / third" involved are merely to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first / second / third" can be interchanged in a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0040] In related technologies, considering that large-scale photovoltaic power stations may reach hundreds of MW, large-scale electromagnetic transient simulation will take up too many computing resources, and there is a lack of methods to simulate the connection of large-scale photovoltaic power stations to the MG system. [MG system 3 (Electric motor generator grid connected system) is a grid-connected technology based on series synchronous machines proposed in the industry, that is, a motor-generator grid-connected system].

[0041] In response to the above problems and taking into account the problems existing in the prior art, the applicant has proposed a simulation modeling system, method, device, electronic device and storage medium of the embodiments of the present application, and provided an electromagnetic transient modeling method for a photovoltaic power station containing an MG system, which is convenient for stability simulation research on the connection of the MG system to a photovoltaic power station, an equivalent simplification method for a photovoltaic power station suitable for the MG system, which accelerates large-scale electromagnetic transient simulation and ensures accuracy, and proposes a consistency evaluation method for a photovoltaic array to further ensure the accuracy of the model simplification.

[0042] Among them, the simulation modeling system, method, device, electronic device and storage medium are described in detail in subsequent embodiments.

[0043] The simulation modeling method involved in the embodiment of the present application can be applicable to Figure 1 , Figure 2 In the structural diagram, it is applied to Figure 6 The simulation modeling device 300 shown is similar to Figure 7 The electronic device 400 shown. The electronic device 400 may be one or more, and the electronic device 400 may also include: a mobile phone, a computer and other smart devices, which are not specifically limited in the embodiment of the present application.

[0044] The simulation modeling system in this application is applied to a large-scale photovoltaic power station, including: a photovoltaic array, an equivalently processed photovoltaic array, an AC bus, an MG system, a step-up transformer and a transmission line; wherein,

[0045] After the photovoltaic array is connected in parallel with the photovoltaic array after being equalized, it is connected to the AC bus, MG system, step-up transformer and transmission line in sequence. The photovoltaic array includes photovoltaic units, DC step-up units, inverter units, box transformers, collection lines and power grids connected in sequence. The photovoltaic units adopt array-level equalization processing, and the photovoltaic array adopts field-level equalization processing. The photovoltaic array also includes: a DC bus, one end of the DC bus is connected to the inverter unit, and the other end is connected to the box transformer. The photovoltaic array after equalization processing includes: an equivalent controlled current source, an equivalent box transformer and an equivalent collection line. One end of the equivalent controlled current source is connected to the DC bus and the box transformer, and the other end is connected to the equivalent box transformer and the equivalent collection line in sequence and then connected to the AC bus. The DC bus transmits the output equivalent controlled current source input signal to the equivalent controlled current source.

[0046] In the embodiment of the present application, the array-level equivalence is mainly achieved by equivalence of photovoltaic units and impedance units: the parameters are specifically determined according to the provided photovoltaic panel model. When equivalent to a photovoltaic module, the series parameters and parallel parameters in the photovoltaic module should be determined according to the total number of series and parallel photovoltaics in the current array. Finally, the parameters of the photovoltaic module are slightly adjusted according to the photovoltaic external characteristic curve to meet the needs of the project. Since the inverter models are the same, the equivalence process can be directly performed. The resistance and inductance are obtained by dividing by their parallel number, and the capacitance is obtained by multiplying by its parallel number.

[0047] The station-level equivalent includes the equivalent of the photovoltaic array, box-type transformer and collector line. When the impedance of the collection line of each inverter unit is different, the equivalent can be calculated based on the principle that the loss before and after the equivalent is unchanged. The output power and reactive power of the photovoltaic unit, the active loss and reactive loss of the box-type transformer, and the active loss and reactive loss of the collector line are calculated through the flow calculation, and the impedance after the equivalent is calculated according to the loss formula. In the same way, the impedance of the equivalent transformer and its capacity are calculated according to the equivalent capacity of the equivalent transformer.

[0048] In order to improve the simulation speed and ensure the accuracy, a controlled current source is used to collect the output current of the photovoltaic inverter outlet side in a single photovoltaic array to be equivalent to the other photovoltaic arrays. At the same time, the controlled current source representing the equivalent photovoltaic array is connected to the MG system through an equivalent transformer and an equivalent collection line, and the parameters of the equivalent transformer and the collection line are calculated according to the circuit parameters and power flow data of the equivalent photovoltaic array.

[0049] For example, see Figure 1 , Figure 1 A schematic diagram of a photovoltaic power station grid-connected topology diagram including an MG system provided in an embodiment of the present application, wherein:

[0050] A large-scale photovoltaic power station containing an MG system may be composed of a photovoltaic unit 101 or an equivalent photovoltaic unit 201, a DC boost unit 102 or an equivalent DC boost unit 202, an inverter unit 103 or an equivalent inverter unit 203, a DC bus 106, a box transformer 104 or an equivalent box transformer 204, a collection line 105 or an equivalent collection line 205, an MG system 3, a boost transformer 4, a transmission line 5, a power grid 6, and an AC bus 7. Among them, the photovoltaic unit 101 is connected to the DC boost unit 102, the DC boost unit 102 is connected to the inverter unit 103, and multiple inverter units 103 are connected to the DC bus 106 in the photovoltaic array 1. Several identical photovoltaic units 101 are connected to the box transformer 104, and the box transformer 104 is connected to the collection line 105.

[0051] The photovoltaic unit 101, the DC boost unit 102, the inverter unit 103, the box transformer 104, the collection line 105 and the DC bus 106 constitute an unequalized photovoltaic array 1, that is, the photovoltaic array 1 can be modeled using a detailed model.

[0052] In order to avoid the model being too complicated and the simulation speed being too slow, the remaining photovoltaic arrays are simplified and equalized.

[0053] Multiple photovoltaic units 101 can eventually be equivalent to an equivalent photovoltaic unit 201, multiple DC boost units 102 can eventually be equivalent to an equivalent DC boost unit 202, multiple inverter units 103 can eventually be equivalent to an equivalent inverter unit 203; multiple box transformers 104 can eventually be equivalent to an equivalent box transformer 204; multiple collection lines 105 can eventually be equivalent to an equivalent collection line 205. The equivalent photovoltaic unit 201 is connected to the equivalent DC boost unit 202, and then connected to the equivalent inverter unit 203, and further connected to the equivalent box transformer 204, and the equivalent box transformer 204 is connected to the equivalent collection line 205 to form an equivalent photovoltaic array 2. The equivalent photovoltaic array 2 is connected to the AC bus 7, and the AC bus 7 is connected to the MG system 3 matching the capacity of the station, and then the MG system 3 is connected to the boost transformer 4 matching the capacity of the MG system 3, and the boost transformer 4 is connected to the transmission line 5, and finally connected to the power grid 6.

[0054] In some embodiments, the DC boost unit in the simulation modeling system adopts constant power control to adjust the secondary side voltage of the photovoltaic unit and maintain power balance; the inverter unit adopts constant DC voltage control and transmits the photovoltaic power of the photovoltaic unit to an equivalent controlled current source and / or a box transformer.

[0055] In the MG system of a large-scale photovoltaic power station, the DC boost unit 102 adopts photovoltaic DC boost control, and the inverter unit 103 adopts DC voltage control, wherein the DC boost unit takes the photovoltaic voltage as the control target, so that the photovoltaic unit can always operate at the maximum power point. First, the MPPT module in the DC boost unit detects the voltage and current output by the photovoltaic module, calculates the output photovoltaic voltage reference value, and then the controller of the DC boost unit adjusts the duty cycle of the switching device in the boost circuit according to the photovoltaic voltage reference value. The photovoltaic inverter takes the DC side voltage as the control target, which is used to maintain the stability of the DC voltage and smoothly send out the power generated by the photovoltaic.

[0056] For the photovoltaic array in the simulation modeling system, it also includes: a DC bus, one end of the DC bus is connected to the inverter unit, and the other end is connected to the box transformer; the photovoltaic array subjected to equivalent processing includes: an equivalent controlled current source, an equivalent box transformer and an equivalent collection line, one end of the equivalent controlled current source is connected to the DC bus and the box transformer, and the other end is connected in sequence to the equivalent box transformer and the equivalent collection line and then merged into the AC bus; the DC bus transmits the output equivalent controlled current source input signal to the equivalent controlled current source.

[0057] In the implementation manner of the present application, the equivalence of the photovoltaic array can be achieved by replacing multiple photovoltaic arrays with one controlled source in the form of an equivalent current source, and the operating characteristics of the actual photovoltaic module are simulated by a photovoltaic array with a detailed model, and the photovoltaic arrays with the same topology are replaced by an equivalent controlled current source. For details, please refer to the attached Figure 2 . Among them, when equivalent photovoltaic arrays are used, an equivalent current source method is used to use one controlled source to be equivalent to multiple photovoltaic arrays. For photovoltaic arrays with similar operating conditions or the same topological structure, the same method can be used for equivalence. The current of the equivalent current source can be taken from the flow calculation results or the current on the outlet side of each photovoltaic array, and is calculated by multiplication. If the sampling point is the current on the low-voltage side of the box transformer, the equivalent current source is connected to the grid through the box transformer and the collector line; if the sampling is on the high-voltage side of the box transformer, the equivalent current source can be directly connected to the grid point without passing through the box transformer, and can be directly connected to the collector line.

[0058] In some embodiments, the photovoltaic array processed by the simulation modeling system further includes: an inverter unit after being processed by the same value, the output end of the inverter unit after being processed by the same value is connected to the DC bus or the box transformer after being processed by the same value, and the MG system includes: a synchronous motor and a synchronous generator, and the synchronous motor and the synchronous generator are coaxially connected; the inverter unit adopts a constant DC voltage control, including:

[0059] The inverter unit transmits variable voltage along the DC bus, box transformer, collection line and AC bus to regulate the operation of the MG system; the inverter unit after equalization transmits variable voltage along the box transformer after equalization, collection line after equalization and AC bus to regulate the operation of the MG system; the inverter unit transmits variable voltage along the DC bus, equivalent controlled current source, box transformer after equalization, collection line after equalization and AC bus to regulate the operation of the MG system.

[0060] The MG system includes two synchronous motors and synchronous generators with the same capacity and coaxially connected rotors, which are connected to a main transformer with matching capacity and connected to the power grid via a transmission line.

[0061] In this embodiment, since two motors are connected to the photovoltaic power station and the power grid, the response of the synchronous motor has an important influence on the transient response of the photovoltaic grid-connected. In the simulation, the synchronous machine model adopts the sixth-order standard model to take into account the sub-transient response of the damping winding. The MG system is driven by the inverter unit, so the inverter unit aims to control the transmission power of the MG system.

[0062] The inverter unit adjusts the operation of the MG system by outputting a voltage with variable frequency and amplitude. MG Or phase is used to adjust the active power transmitted by the MG system; by adjusting the output voltage amplitude, it is used to adjust the stator voltage amplitude u of the MG system MG To adjust the stator magnetic field and match it with the excitation system.

[0063] The inverter unit adjusts the frequency of the output voltage according to the following calculation formula:

[0064]

[0065] In the formula, k pac and k iac Respectively represent the proportional and integral coefficients of the voltage-frequency controller of the inverter unit; u dc * and u dc They represent the reference value and actual value of the DC voltage of the photovoltaic array respectively; f0 represents the rated frequency of the stator voltage of the MG system; f MG Represents the voltage reference value calculated by the inverter unit, which is theoretically equal to the expected stator voltage value of the actual operation of the MG system.

[0066] The inverter unit contains two control loops, which need to be switched during the startup and grid-connection stages. During the startup stage, the frequency and amplitude of the output voltage increase linearly, i.e. u MG / f MG =const, the ratio determines how fast the inverter unit starts the MG system. After being connected to the grid, the above expression is used for control, and the switching condition of the control loop is whether the MG system is connected to the grid.

[0067] In some embodiments, a variable voltage is transmitted in the simulation modeling system to regulate the operation of the MG system, including: the inverter unit adjusts the frequency or phase of the variable voltage to regulate the active power transmitted by the MG system; the inverter unit adjusts the amplitude of the variable voltage to regulate the stator voltage amplitude of the MG system.

[0068] In this embodiment, one side of the photovoltaic inverter unit is connected to the DC boost unit and the other side is connected to the box transformer. The actual deviation of the DC side voltage is converted into a frequency deviation value through a PI regulator and added to the grid frequency as the frequency command value of the motor stator voltage in the MG system.

[0069] See also Figure 2 , Figure 2 A schematic diagram of a site-level photovoltaic array equivalent structure provided in an embodiment of the present application.

[0070] The photovoltaic array 1 is simplified to an equivalent photovoltaic array 2 , and in order to better speed up the simulation, the equivalent photovoltaic unit 201 , the equivalent DC boost unit 202 and the equivalent inverter unit 203 are in the form of a controlled current source 206 .

[0071] The equalization process is mainly divided into array-level equalization and site-level equalization.

[0072] The array-level equivalent mainly includes the equivalent of photovoltaic unit 101 and impedance element. The specific equivalent process of photovoltaic components is to use fewer photovoltaic units 101 or one photovoltaic unit 101 to equalize the photovoltaic array 1, determine the photovoltaic parameters according to the number of series and parallel connections of each photovoltaic panel on site, and then determine the model and parameters of the inverter unit 103.

[0073] The equivalence principle is determined by the fact that the photovoltaic external characteristics after equivalent are basically consistent with the characteristics of multiple non-equivalent photovoltaic units 101. And according to the error between the PV or VI curves of the detailed model compared with the electromagnetic transient simulation, the photovoltaic component parameters are fine-tuned so that the error meets the requirements. The impedance element can be directly equivalent when the connected photovoltaic units 201 after equivalent are the same. Among them, the equivalence principle is calculated using the following expression:

[0074] R eq1 =R1 / n

[0075] L eq1 =L1 / n

[0076] C eq1 =nC1

[0077] Where n represents the number of photovoltaic units contained in a photovoltaic array of quasi-equivalent value; R1, L1 and C1 represent the resistance, inductance and capacitance parameters of the filter circuit in a photovoltaic unit respectively; R eq1 , L eq1 and C eq1 They respectively represent the equivalent resistance, equivalent inductance and equivalent capacitance parameters of the filter circuit in a photovoltaic array after being equalized.

[0078] See also Figure 5 , Figure 5A flowchart of a simulation modeling method provided in an embodiment of the present application is applied to a simulation modeling system. The method may include steps S110 to S140.

[0079] Step S110: Acquire the terminal voltage-frequency difference between the synchronous generator and the synchronous motor in the MG system.

[0080] Step S120: Calculate the power angle of the MG system based on the generator-end voltage-frequency difference.

[0081] Step S130: Modeling is performed based on array-level equivalent processing and station-level equivalent processing to obtain an equivalent processed photovoltaic array, and a target power angle corresponding to the total output power of the photovoltaic array and the equivalent photovoltaic array is calculated.

[0082] Step S140: adjusting the operation of the synchronous generator and the synchronous motor based on the target power angle and the power angle.

[0083] In the embodiment of the present application, the terminal voltage frequency difference and power angle calculation between the synchronous generator and the synchronous motor in the MG system can be found in Figure 4 , Figure 4 A control schematic diagram of a DC boost converter (left) and inverter (right) provided in this application.

[0084] The photovoltaic DC voltage control adopts the output voltage and output current of the photovoltaic unit 101 as the input of the MPPT module 208, and outputs the voltage corresponding to the maximum power point of the photovoltaic through the MPPT module 208, and after subtracting it from the output voltage of the photovoltaic unit 101, it is used as the input of the first PI controller 209 (controller 1) to obtain the control signal S1 of the DC boost link.

[0085] WhenU pv >U mppt When U pv Make it with U mppt Keep consistent with; when U pv <U mppt When the output signal S1 of the first PI controller 209 decreases, U pv Make it with U mppt Keep consistent to maintain the voltage of the photovoltaic unit 101 always running at the maximum power point to output maximum power.

[0086] The DC voltage control adopted by the inverter unit 103 is responsible for converting the DC voltage at the inverter unit 203 after the equalization into an AC voltage, and calculating the voltage reference value U across the DC bus capacitor through the maximum power point tracking MPPT module 208 dcref and the actual voltage U across the DC bus capacitordc The difference is used as the input of the second PI controller 210 (controller 2), which is converted into a frequency deviation value after adjustment by the second PI controller 210 and compared with the grid side frequency f g The superposition waits until the final frequency reference value f ref , as the control signal S2 to control the inverter unit 203 after equalization.

[0087] WhenU dc Greater than U dcref When Δf>0, the terminal voltage frequency of the synchronous motor in the MG system 3 increases accordingly, and the power angle of the synchronous motor increases, so that the active power output by the MG system 3 increases accordingly, and thus the charging and discharging speed of the DC bus capacitor of the DC boost unit 102 increases accordingly, U dc Reduce, under the regulation of the DC bus voltage feedback loop, U dc Gradually approaching until it is equal to U dcref .

[0088] WhenU dc Less than U ref When Δf<0, the frequency of the terminal voltage of the synchronous motor in the MG system 3 decreases accordingly, and the power angle of the synchronous motor decreases, so that the active power output by the MG system 3 decreases accordingly, and the charging and discharging speed of the DC bus capacitor of the DC boost unit 102 decreases accordingly, U dc Increase, under the regulation of the DC bus voltage feedback loop, U dc It gradually approaches until it is equal to U dcref .

[0089] Specifically, in the above embodiment, the voltage-frequency difference between the synchronous generator and the synchronous motor in the MG system 3 is controlled so that the power angle of the MG system 3 reaches a power angle that matches the output power of the entire photovoltaic station.

[0090] In some embodiments, step S130 may further include steps S132 to S134.

[0091] Step S132: Based on array-level equivalent processing, photovoltaic parameters and photovoltaic series-parallel parameters are determined through the number of photovoltaic units in series and parallel and the impedance elements corresponding to the photovoltaic units, and an equivalently processed photovoltaic array is obtained according to the photovoltaic parameters and photovoltaic series-parallel parameters.

[0092] In the embodiment of the present application, the photovoltaic array 1 is simplified to an equivalent photovoltaic array 2, and in order to better speed up the simulation, the equivalent photovoltaic unit 201, the equivalent DC boost unit 202 and the equivalent inverter unit 203 are in the form of a controlled current source 206.

[0093] The array-level equivalent mainly includes the equivalent of photovoltaic unit 101 and impedance element. The specific equivalent process of photovoltaic components is to use fewer photovoltaic units 101 or one photovoltaic unit 101 to equalize the photovoltaic array 1, determine the photovoltaic parameters according to the number of series and parallel connections of each photovoltaic panel on site, and then determine the model and parameters of the inverter unit 103.

[0094] The equivalence principle is determined by the fact that the photovoltaic external characteristics after equivalent are basically consistent with the characteristics of multiple non-equivalent photovoltaic units 101. And according to the error between the PV or VI curves of the detailed model compared with the electromagnetic transient simulation, the photovoltaic component parameters are fine-tuned so that the error meets the requirements. The impedance element can be directly equivalent when the connected inverter unit 203 after equivalent is the same.

[0095] Step S134: Calculate the active loss and reactive loss of the photovoltaic unit, box transformer and collection line based on the station-level equivalent processing, and obtain the equivalent processed photovoltaic array according to the active loss, reactive loss and the equivalent controlled current source input signal.

[0096] The equivalent value of the site level includes the equivalent value of the photovoltaic array 1, the box transformer 104 and the collection line 105. The equivalent value principle is based on the method of equalization that the loss before and after the equalization remains unchanged. The specific equivalent value process is as follows:

[0097] When the impedance (length) of the collection line 105 of each inverter unit 103 is different, the equivalent impedance after equivalent can be calculated based on the principle that the loss before and after equivalent is unchanged. The equivalent process is:

[0098] The output active power P of each photovoltaic unit 101 is obtained according to the power flow data. p(i) and reactive Q p(i) ; Active power loss P of each box transformer t(i) and reactive power loss Q t(i) , the active power loss P of each collection line 105 l(i) and reactive power loss Q l(i) ;

[0099] The power flow of the photovoltaic unit 201 after calculation is equivalent to: P eq2 =∑P p(i) -∑P t(i) , Q eq2 =∑Q p(i) -∑Q t(i) ;

[0100] The impedance of the equivalent collection line 205 of the equivalent photovoltaic unit 201 is calculated, where the expression is:

[0101]

[0102] In the formula, R eq2 and X eq2That is the total impedance of the photovoltaic unit collection line after equalization; U MG Represents the stator voltage of the motor in the MG system.

[0103] The impedance of the equivalent transformer is as follows:

[0104]

[0105] In the formula, R teq2 and X teq2 That is the equivalent resistance and reactance value of the transformer after equalization.

[0106] The capacity of the transformer is the total capacity of the equivalent transformer.

[0107] In order to improve the simulation speed, the photovoltaic array 2 composed of multiple photovoltaic units 201, DC boost units 202 and inverter units 203 is equivalent to a controlled current source 206. The controlled current source 206 measures and collects the current on the low-voltage side of the box transformer 104 in the photovoltaic array 1, which is multiplied by the input signal 207 as the current of the controlled current source 206. The controlled current source 206 is connected to the box transformer 204, and then connected to the collection line 205 after the equivalent value is connected to the AC bus 7.

[0108] In some embodiments, see Figure 3 and Figure 5 , Figure 3 This is a schematic flow chart of a photovoltaic array consistency assessment method provided in the present application. The simulation modeling method may further include steps S102 to S108.

[0109] Step S102: Obtain a target number of photovoltaic arrays.

[0110] Step S104: determining whether the photovoltaic units in the photovoltaic array meet the target requirements, wherein the target requirements include: model, topology and power generation differences.

[0111] In the embodiment of the present application, the target demand can be adaptively set according to the actual photovoltaic array evaluation demand.

[0112] Step S106: if the target demand is not met, classify the target number of photovoltaic arrays into different types, and return to step S106 to obtain the target number of photovoltaic arrays.

[0113] In an embodiment of the present application, the models and topologies of the i-1th and ith photovoltaic arrays 1 can be first judged. If the models and topologies are inconsistent, the two photovoltaic arrays are classified into the kth and k+1th categories, and i=i+1, k=k+1 is set, and the model and topology judgment step S1 is returned.

[0114] Step S108: When the target requirements are met, the photovoltaic arrays are classified into preset types, and the photovoltaic arrays are classified based on each target requirement until the classification requirements of all target number of photovoltaic arrays are completed.

[0115] In the embodiment of the present application, if they are consistent, then Figure 3 In the power generation difference evaluation step S2, the power generation difference caused by the light intensity and temperature difference or the operating life is evaluated to determine whether the power generation difference meets the requirements. If it does not meet the requirements, the two photovoltaic arrays are classified as the kth category and the k+1th category respectively, and i=i+1, k=k+1 are set, and the model and topology judgment step S1 is returned. If the requirements are met, the two photovoltaic arrays are classified as the kth category, and the classification and classification modeling step S3 is performed. If all classifications have not been completed, i=i+1, k=k+1 are set. Return to the model and topology judgment step S1 to continue the judgment. If all classifications have been completed, all k-category photovoltaic arrays are classified according to the classification situation, and each category is modeled separately or equivalently.

[0116] It should be noted that when the classification of category k is completed and the next round begins, different categories can be classified into another category while satisfying the previous round of screening. After one category k is classified, another category k can be classified. Among them, the classification of all k categories is set according to specific usage needs.

[0117] In this embodiment, it is first determined whether the models, topologies and structures of several photovoltaic units or photovoltaic arrays are consistent. If they are inconsistent, they cannot be equated in the above manner and are classified into one category separately. If they are consistent, the second step is entered; in the next step, it can be determined whether there are differences in their power generation characteristics. When the distribution of a photovoltaic site is relatively uniform and the ambient temperature difference is not large, and other factors such as life span have no obvious difference on the power generation, they can be equated in the above manner and classified into the same category. Otherwise, they are classified into one category separately. Finally, all photovoltaic arrays of the same category are equivalent in the above manner, and those of different categories are modeled separately.

[0118] See also Figure 6 , Figure 6 The structural block diagram of a simulation modeling device provided in the present application is applied to a simulation modeling system. The simulation modeling device 300 includes: an acquisition module 310, a calculation module 320, a simulation modeling module 330 and an adjustment module 340, wherein:

[0119] The acquisition module 310 is used to acquire the terminal voltage frequency difference between the synchronous generator and the synchronous motor in the MG system.

[0120] The calculation module 320 is used to calculate the power angle of the MG system based on the machine-end voltage-frequency difference.

[0121] The modeling and calculation module 330 is used to obtain a photovoltaic array with equivalent processing by modeling based on array-level equivalent processing and station-level equivalent processing, and calculate the target power angle corresponding to the total output power of the photovoltaic array and the photovoltaic array after equivalent processing.

[0122] The adjustment module 340 is used to adjust the operation of the synchronous generator and the synchronous motor based on the target power angle and the power angle.

[0123] It should be noted that the present application also includes other modules for executing the above-mentioned method, which correspond to the method part and will not be repeated here. The device embodiments in the present application correspond to the aforementioned method embodiments. The specific principles in the device embodiments can be found in the contents of the aforementioned method embodiments and will not be repeated here.

[0124] In several embodiments provided in this embodiment, the coupling between modules may be electrical, mechanical or other forms of coupling.

[0125] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of software functional modules.

[0126] See also Figure 7 , Figure 7 The present application provides a structural block diagram of an electronic device 400 that can execute the above-mentioned simulation-based modeling method. The electronic device 400 can be a smart phone, a tablet computer, a computer, a portable computer or other devices.

[0127] The electronic device 400 further includes a processor 402 and a memory 404. The memory 404 stores a program that can execute the contents of the aforementioned embodiments, and the processor 402 can execute the program stored in the memory 404.

[0128] Among them, the processor 402 may include one or more cores and message matrix units for processing data. The processor 402 uses various interfaces and lines to connect various parts of the entire electronic device 400, and executes various functions and processes data of the electronic device 400 by running or executing instructions, programs, code sets or instruction sets stored in the memory 404, and calling data stored in the memory 404. Optionally, the processor 402 can be implemented in at least one hardware form of digital signal processing (Digital Signal Processing, DSP), field programmable gate array (Field-Programmable Gate Array, FPGA), and programmable logic array (Programmable Logic Array, PLA). The processor 402 can integrate one or a combination of a central processing unit (Central Processing Unit, CPU), a graphics processing unit (Graphics Processing Unit, GPU) and a modulation decoder. Among them, the CPU mainly processes the operating system, user interface and application programs; the GPU is responsible for rendering and drawing display content; and the modem is used to process wireless communication. It can be understood that the above-mentioned modulation decoder may not be integrated into the processor, but implemented separately through a communication chip.

[0129] The memory 404 may include a random access memory (RAM) or a read-only memory (ROM). The memory 404 may be used to store instructions, programs, codes, code sets or instruction sets. The memory 404 may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for implementing at least one function (e.g., instructions for a user to obtain a random number), instructions for implementing the following various method embodiments, etc. The data storage area may also store data (e.g., random numbers) created by the terminal during use, etc.

[0130] The electronic device 400 may also include a network module and a screen. The network module is used to receive and send electromagnetic waves, realize the mutual conversion between electromagnetic waves and electrical signals, and thus communicate with a communication network or other devices, such as communicating with an audio playback device. The network module may include various existing circuit components for performing these functions, such as antennas, radio frequency transceivers, digital signal processors, encryption / decryption chips, user identity modules (SIM) cards, memories, etc. The network module may communicate with various networks such as the Internet, corporate intranets, wireless networks, or communicate with other devices via wireless networks. The above-mentioned wireless networks may include cellular telephone networks, wireless local area networks, or metropolitan area networks. The screen may display interface content and perform data interaction.

[0131] Please refer to Figure 8 , Figure 8 The structure block diagram of a computer-readable storage medium provided in an embodiment of the present application is shown. The computer-readable storage medium 500 stores a program code 510, and the program code 510 can be called by a processor to execute the method described in the above method embodiment.

[0132] The computer-readable storage medium 500 may be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read-only memory), an EPROM, a hard disk, or a ROM. Optionally, the computer-readable storage medium includes a non-transitory computer-readable storage medium. The computer-readable storage medium 500 has storage space for program code 510 for executing any method steps in the above method. These computer program codes 510 can be read from or written to one or more computer program products. The computer program code 510 can be compressed, for example, in an appropriate form.

[0133] The embodiment of the present application also provides a computer program product or a computer program, which includes computer instructions, and the computer instructions are stored in a computer-readable storage medium 500. The processor of the computer device reads the computer instructions from the computer-readable storage medium 500, and the processor 402 executes the computer instructions, so that the computer device executes the simulation-based modeling method described in the above various optional implementations.

[0134] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A simulation modeling system, applied to large-scale photovoltaic power stations, characterized in that: include: PV array, PV array with equivalent treatment, AC bus, MG system, step-up transformer and transmission line; among them, The photovoltaic array is connected in parallel with the photovoltaic array after being equalized, and then connected to the AC bus, the MG system, the step-up transformer and the transmission line in sequence; the photovoltaic array includes a photovoltaic unit, a DC step-up unit, an inverter unit, a box transformer, a collection line and a power grid connected in sequence; The photovoltaic unit is processed at the array level, and the photovoltaic array is processed at the station level to perform simulation.

2. The simulation modeling system according to claim 1, characterized in that: The photovoltaic array further comprises: a DC bus, one end of which is connected to the inverter unit, and the other end of which is connected to the box transformer; The photovoltaic array subjected to equivalent processing comprises: an equivalent controlled current source, an equivalent box transformer and an equivalent collection line, wherein one end of the equivalent controlled current source is connected to the DC bus and the box transformer, and the other end is connected in sequence to the equivalent box transformer and the equivalent collection line and then merged into the AC bus; The DC bus transmits the output equivalent controlled current source input signal to the equivalent controlled current source.

3. The simulation modeling system according to claim 2, characterized in that: The DC boost unit adopts constant power control to adjust the secondary side voltage of the photovoltaic unit and maintain power balance; the inverter unit adopts constant DC voltage control and transmits the photovoltaic power of the photovoltaic unit to the equivalent controlled current source and / or the box transformer.

4. The simulation modeling system according to claim 3, characterized in that: The photovoltaic array processed by equalization further includes: an inverter unit after equalization, the output end of the inverter unit after equalization is connected to the DC bus or the box transformer after equalization, the MG system includes: a synchronous motor and a synchronous generator, the synchronous motor is coaxially connected to the synchronous generator; the inverter unit adopts a constant DC voltage control, including: The inverter unit transmits a variable voltage along the DC bus, the box transformer, the collection line and the AC bus to adjust the operation of the MG system; The equivalent inverter unit transmits variable voltage along the equivalent box transformer, the equivalent collection line and the AC bus to adjust the operation of the MG system; The inverter unit transmits a variable voltage along the DC bus, the equivalent controlled current source, the equivalent box transformer, the equivalent collection line and the AC bus to adjust the operation of the MG system.

5. The simulation modeling system according to claim 4, characterized in that: The transmitting variable voltage to adjust the operation of the MG system comprises: The inverter unit adjusts the active power transmitted by the MG system by adjusting the frequency or phase of the variable voltage; The inverter unit adjusts the amplitude of the stator voltage of the MG system by adjusting the amplitude of the variable voltage.

6. A simulation modeling method, characterized in that: Applied to the simulation modeling system according to any one of claims 1 to 5, the method comprises: Obtaining a terminal voltage frequency difference between a synchronous generator and a synchronous motor in the MG system; Calculating the power angle of the MG system based on the generator-end voltage-frequency difference; Modeling a photovoltaic array with equivalent processing based on the array-level equivalent processing and the station-level equivalent processing, and calculating a target power angle corresponding to the total output power of the photovoltaic array and the photovoltaic array after equivalent processing; The operations of the synchronous generator and the synchronous motor are adjusted based on the target power angle and the power angle.

7. The simulation modeling method according to claim 6, characterized in that: The photovoltaic array obtained by performing modeling based on the array-level equivalent processing and the station-level equivalent processing to obtain equivalent processing includes: Determine photovoltaic parameters and photovoltaic series-parallel parameters based on array-level equivalent processing of the number of series and parallel connections of the photovoltaic units and the impedance elements corresponding to the photovoltaic units, and obtain an equivalently processed photovoltaic array based on the photovoltaic parameters and the photovoltaic series-parallel parameters; The active loss and reactive loss of the photovoltaic unit, box transformer and collection line are calculated based on the station-level equivalent processing, and the photovoltaic array with equivalent processing is obtained according to the active loss, reactive loss and the equivalent controlled current source input signal.

8. The simulation modeling method according to claim 6, characterized in that: The simulation modeling method further comprises: Acquire a target number of photovoltaic arrays; Determining whether the photovoltaic units in the photovoltaic array meet target requirements, wherein the target requirements include: model, topology and power generation differences; In the case where the target requirement is not met, the target number of photovoltaic arrays are classified into different types, and the step of returning to obtain the target number of photovoltaic arrays is performed; When the target requirements are met, the target number of photovoltaic arrays are classified into preset types, and the photovoltaic arrays are classified based on each of the target requirements until the classification requirements of all target requirements are completed.

9. A simulation modeling device, characterized in that: Applied to the simulation modeling system, the device comprises: An acquisition module, used for acquiring a terminal voltage frequency difference between a synchronous generator and a synchronous motor in the MG system; A calculation module, used for calculating the power angle of the MG system based on the machine-end voltage-frequency difference; A modeling and calculation module, for modeling a photovoltaic array with equivalent processing based on the array-level equivalent processing and the station-level equivalent processing, and calculating a target power angle corresponding to the total output power of the photovoltaic array and the photovoltaic array after equivalent processing; An adjustment module is used to adjust the operation of the synchronous generator and the synchronous motor based on the target power angle and the power angle.

10. An electronic device, characterized in that: The electronic device includes a memory, a processor and a ramp pad, the memory stores a program code that can be run on the processor, and when the program code is executed by the processor, the simulation modeling method according to any one of claims 6 to 8 is implemented.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program codes, and the program codes are called by one or more processors to execute the simulation modeling method according to any one of claims 6 to 8.

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