A method for calculating safe operation boundary of high-inertia energy storage type phase modifier under fault

Abstract

The application relates to the technical field of safe operation of power systems and electric machines, and particularly discloses a safe operation boundary calculation method for a high-inertia energy storage type phase modifier under fault, which comprises the following steps: establishing an electromagnetic field calculation model of a two-dimensional straight part and a three-dimensional end area according to an electromagnetic design scheme of the high-inertia energy storage type phase modifier; establishing a frequency and voltage support excitation control system of the high-inertia energy storage type phase modifier, and bidirectionally dynamically coupling the excitation control system with the electromagnetic field calculation model to obtain power grid frequency and voltage through a phase-locked loop; determining loss values of each structural member in a fault process through the electromagnetic field calculation model; establishing a fluid and heat coupling calculation model according to a ventilation system structure of the high-inertia energy storage type phase modifier, and importing the loss values of each structural member into the fluid and heat coupling calculation model as heat sources; and determining safe operation limit time of the high-inertia energy storage type phase modifier under system frequency or voltage fault according to maximum temperature rises allowed by each structural member.

Description

Technical Field

[0001] This invention relates to the field of power system and motor safe operation technology, specifically to a method for calculating the safe operation boundary of a high-inertia energy storage synchronous condenser under fault conditions. Background Technology

[0002] Building a new power system dominated by new energy sources is an inevitable trend in energy development. However, the high proportion of new energy connected to the grid significantly weakens the inertia and stability of the power system, leading to more frequent and severe fluctuations in grid frequency and voltage. High-inertia energy storage synchronous condensers, due to their superior power regulation capabilities, are widely used in wind power, variable-speed pumped storage, and other fields, and are considered one of the key pieces of equipment for providing rapid inertia and voltage support to the future power grid. When frequency or voltage faults occur in the grid, high-inertia energy storage synchronous condensers need to respond quickly through their excitation control system, either releasing / absorbing active power to support the frequency or generating / absorbing reactive power to stabilize the voltage.

[0003] However, during such faults, the motor's internal components will be subjected to severe electromagnetic and thermal stress shocks. When frequency is supported, the motor needs to operate at significant speed changes, causing iron losses, copper losses, and additional losses to fluctuate drastically and potentially concentrate locally in the stator and rotor cores, windings, and end metal structural components. When voltage is supported, significant adjustments to the excitation current also alter the loss distribution. These transient losses are converted into heat. If the cooling system cannot remove this heat in time, it will cause a sharp rise in localized motor temperatures, potentially burning out insulation, causing thermal deformation or even melting of structural components, resulting in permanent motor damage. Currently, research on control strategies for high-inertia energy storage synchronous condensers focuses primarily on their support effect on the external power grid, while lacking sophisticated assessment methods for their internal electromagnetic and thermal safety status.

[0004] Traditional motor thermal models are typically based on lumped parameters or simplified thermal networks, making it impossible to accurately calculate the transient temperature rise of complex structural components during faults. Furthermore, the electromagnetic response of a motor and the regulation of the control system are a dynamically coupled process; existing methods often separate these two aspects, failing to establish a fully dynamic coupled model of "electromagnetic field-circuit-control-fluid-heat," resulting in the inability to accurately predict the motor's true thermal state and safe operating limit under extreme fault conditions. This has become a technical bottleneck restricting high-inertia energy storage synchronous condensers from fully realizing their grid support potential.

[0005] Therefore, there is an urgent need for a method that can accurately calculate the internal transient temperature rise of high-inertia energy storage synchronous condensers under frequency / voltage faults and determine their safe operating boundaries accordingly, so as to provide a key basis for the safe control of motors and the stable operation of the power grid. Summary of the Invention

[0006] To address the aforementioned shortcomings and gaps in existing technologies, the present invention aims to provide a method for calculating the safe operating boundary of high-inertia energy storage synchronous condensers under fault conditions. This method solves the problem that existing technologies cannot accurately assess the internal thermal safety status of the condenser under grid support tasks. Specifically, the present invention aims to establish a high-precision numerical model of electromagnetic field-circuit-control-fluid-thermal dynamic coupling to achieve a detailed simulation of the internal electromagnetic-thermal behavior of high-inertia energy storage synchronous condensers during fault transients. This allows for the scientific definition of their safe operating boundary, providing a theoretical basis and technical support for the active protection and optimized control of the condenser during grid support.

[0007] To achieve the objective of this invention, this application provides a method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions, comprising: Step S1: Based on the electromagnetic design scheme of the high-inertia energy storage type synchronous condenser, establish electromagnetic field calculation models for the two-dimensional straight section and the three-dimensional end region; Step S2: Establish a frequency and voltage support excitation control system for a high-inertia energy storage type synchronous condenser, and dynamically couple the excitation control system with the electromagnetic field calculation model in both directions. Obtain the grid frequency and voltage through a phase-locked loop. When the system frequency or voltage deviates, the excitation control system calculates the excitation voltage based on the deviation value. Step S3: Based on the stator and rotor voltages during the frequency or voltage fault process, determine the loss values ​​of each structural component during the fault process using the electromagnetic field calculation model. Step S4: Based on the ventilation system structure of the high-inertia energy storage type synchronous condenser, establish a fluid and heat coupling calculation model, and import the loss values ​​of each structural component as a heat source into the fluid and heat coupling calculation model to determine the transient temperature rise of each structural component. Step S5: Determine the safe operating limit time of the high-inertia energy storage synchronous condenser under system frequency or voltage faults based on the maximum allowable temperature rise of each structural component.

[0008] In some specific embodiments, in step S1, the two-dimensional straight section includes the stator core, the rotor core, the straight segment of the stator winding, and the straight segment of the rotor winding; the three-dimensional end region includes the stator end winding, the rotor end winding, the stator tooth pressure plate, the stator pressure ring, the rotor pressure ring, and the rotor retaining ring.

[0009] In some specific embodiments, step S2 includes: The excitation voltage output by the excitation control system is used as the excitation input to the electromagnetic field calculation model. At the same time, the stator current, rotor current, flux linkage and speed parameters of the motor calculated by the electromagnetic field calculation model are fed back to the excitation control system for real-time correction of the excitation voltage.

[0010] In some specific embodiments, in step S2, when the absolute value of the grid frequency deviation exceeds the preset frequency dead zone threshold, the excitation control system calculates the q-axis excitation voltage based on the frequency deviation and controls the motor to enter the deceleration generation mode or the acceleration motor mode; when the absolute value of the grid voltage deviation exceeds the preset voltage dead zone threshold, the excitation control system calculates the d-axis excitation voltage based on the voltage deviation and controls the motor to enter the phase adjustment mode.

[0011] In some specific embodiments, in step S2, the operating speed of the high-inertia energy storage type synchronous condenser is limited to a preset safe operating speed range. If the speed reaches the boundary of the range, the motor is controlled to switch to no-load operation.

[0012] In some specific embodiments, in step S3, the stator voltage and rotor voltage of the high-inertia energy storage synchronous condenser during the fault process are used as excitation, and the loss distribution of each structural component is obtained through the electromagnetic field calculation model of the two-dimensional linear part and the three-dimensional end region.

[0013] In some specific embodiments, in step S4, the fluid and heat coupling calculation model is based on three-dimensional flow and heat transfer control equations to simulate the flow and heat exchange process of the cooling medium inside the motor and obtain the transient temperature distribution of each structural component.

[0014] In some specific embodiments, in step S5, the safe operating limit time is determined based on the transient temperature rise and maximum allowable temperature of each structural component during the fault process, and the earliest time when the allowable temperature is reached among all structural components is taken as the safe operating limit time.

[0015] In some specific embodiments, the excitation control system uses a proportional-integral regulator combined with a droop control algorithm to dynamically calculate the excitation voltage commands for the d-axis and q-axis.

[0016] In some specific embodiments, the fluid and heat coupling calculation model adopts the k-ε turbulence model and is combined with the wall function method to simulate the turbulent flow and convective heat transfer process of the cooling medium in the internal air duct of the motor.

[0017] The beneficial effects of the above technical solution are as follows: (1) This invention is the first to dynamically couple and simulate “electromagnetic field-circuit-control-fluid-heat”. By bidirectionally coupling the control system and the electromagnetic field model, the true electromagnetic response of the motor under fault is accurately reproduced; by using independent 3D end electromagnetic model and 3D flow-heat model, the accurate calculation of loss and temperature rise in complex areas such as the motor end during transient processes is realized for the first time, avoiding the huge errors brought about by traditional simplification methods.

[0018] (2) This method uses the temperature of the most vulnerable point inside the motor as the criterion, which can fundamentally evaluate the motor's safe operation capability. The resulting safe operation boundary is no longer a conservative estimate based on experience, but a precise calculation result based on specific motor design and specific fault conditions, providing the most critical data support for achieving precise control of the motor to "power up when it should, and power up safely".

[0019] (3) This invention can not only be used to assess safety boundaries, but also clearly show the distribution and variation of losses and temperature rise during the fault process, which can be used to guide the electromagnetic design of motors and the improvement of ventilation and cooling systems. At the same time, it can also be used to verify and optimize excitation control strategies, while ensuring the grid support effect and actively avoiding operating ranges that may cause thermal damage to motors.

[0020] (4) By ensuring the safety of the high-inertia energy storage synchronous condenser that serves as the grid support, the present invention can effectively prevent the grid support capability from dropping again due to motor overheating or even damage, and greatly enhance the recovery capability and operational reliability of the new power system under fault conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating a method for calculating the safe operation boundary of a high-inertia energy storage synchronous condenser under fault conditions, provided as an embodiment of the present invention; Figure 2 An electrical wiring diagram provided for one embodiment of the present invention; Figure 3 A high-inertia energy storage synchronous condenser frequency / voltage support control topology diagram provided for one embodiment of the present invention; Figure 4 The temperature rise curve of the rotor core of a high-inertia energy storage synchronous condenser under a three-phase short-circuit fault is provided as an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0025] Example 1 One embodiment of the present invention provides a method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions, referring to... Figure 1 As shown, it includes: Step S1: Based on the electromagnetic design scheme of the high-inertia energy storage type synchronous condenser, establish electromagnetic field calculation models for the two-dimensional straight section and the three-dimensional end region; Furthermore, let the set of key structural components of the motor be {1, 2, ..., N}, where N is the total number of components. For any component i, its transient temperature rise after the onset of a fault is T. i (t), the maximum allowable temperature of the component is T. max,i The safe operating limit time t of a high-inertia energy storage synchronous condenser under this fault condition is then determined. limit Determined by the following formula: This limit time can serve as the core basis for setting the protection action delay in the upper-level control system.

[0026] Furthermore, in step S1, the two-dimensional straight section model accurately characterizes the electromagnetic characteristics of the stator core, rotor core, stator winding straight section, and rotor winding straight section; the three-dimensional end region is used to accurately calculate the losses and magnetic field distribution of the stator winding end, rotor winding end, stator tooth pressure plate, stator and rotor pressure ring, rotor retaining ring, and inner support ring.

[0027] Step S2: Establish a frequency and voltage support excitation control system for a high-inertia energy storage type synchronous condenser, and dynamically couple the excitation control system with the electromagnetic field calculation model in both directions. Obtain the grid frequency and voltage through a phase-locked loop. When the system frequency or voltage deviates, the excitation control system calculates the excitation voltage based on the deviation value. In one specific embodiment of the present invention, step S2 includes: The excitation voltage output by the excitation control system is used as the excitation input to the electromagnetic field calculation model. At the same time, the stator current, rotor current, flux linkage and speed parameters of the motor calculated by the electromagnetic field calculation model are fed back to the excitation control system for real-time correction of the excitation voltage.

[0028] In a specific embodiment of the present invention, in step S2, when the absolute value of the grid frequency deviation exceeds the preset frequency dead zone threshold, the excitation control system calculates the q-axis excitation voltage based on the frequency deviation and controls the motor to enter the deceleration generation mode or the acceleration motor mode; when the absolute value of the grid voltage deviation exceeds the preset voltage dead zone threshold, the excitation control system calculates the d-axis excitation voltage based on the voltage deviation and controls the motor to enter the phase adjustment mode.

[0029] In a specific embodiment of the present invention, in step S2, the operating speed of the high-inertia energy storage type synchronous condenser is limited to a preset safe operating speed range. If the speed reaches the boundary of the range, the motor is controlled to switch to no-load operation.

[0030] Furthermore, in step S2, the bidirectional dynamic coupling is specifically manifested as follows: the excitation voltage output by the excitation control system is applied to the rotor winding of the electromagnetic field model in real time as an excitation source; at the same time, the real-time response parameters of the motor calculated by the electromagnetic field model at each electrical time step, including stator and rotor current, flux linkage, and rotor speed, are fed back to the excitation control system through the data interface as input for its calculation in the next time step, thereby realistically reproducing the dynamic interaction between the control system and the complex electromagnetic response of the motor under fault conditions, and avoiding the error accumulation caused by traditional one-way simulation.

[0031] Furthermore, in step S2, the operating condition control decision for the high-inertia energy storage synchronous condenser under frequency support is based on the following: f = ff N Function definition: Define the operating state S∈{-1, 0, 1}, where S=-1 corresponds to the deceleration power generation condition; S=0 corresponds to the no-load condition; and S=1 corresponds to the acceleration electric motor condition. The operating condition decision function is: in, f d To control the dead zone threshold for frequency, f The actual frequency of the power grid. f N This is the rated frequency.

[0032] When the power grid frequency deviates, and the absolute value of the deviation exceeds the preset frequency dead zone threshold. f d At that time, the excitation control system calculates the q-axis excitation voltage based on the frequency deviation value, and then adjusts the amplitude, frequency, and phase of the excitation current: if the frequency deviation is less than - f d If the frequency deviation is greater than 100%, the motor will operate in a reduced-speed power generation mode; fd Then the motor is controlled to operate in a speed-up motor mode, thereby achieving active support and stability of the power grid frequency.

[0033] When the grid voltage deviates, and this deviation Δ U = UU N The absolute value exceeds the preset voltage control dead zone threshold U. d At that time, the excitation control system calculates the d-axis excitation voltage based on the voltage deviation value, and then adjusts the magnitude of the excitation current: by controlling the strength of the excitation current, the reactive power absorbed or generated by the motor to the grid is changed, so that the high inertia energy storage type synchronous condenser works in the phase adjustment condition, thereby ensuring the stability of the grid voltage.

[0034] Furthermore, to ensure equipment safety, the control strategy incorporates built-in safety constraints: the motor's speed range should not exceed the safe operating speed range [n]. min ,n max The system's final execution instruction M final Determined by the following formula: If the speed reaches the critical value during the speed change, it will switch to no-load operation and maintain the current speed.

[0035] Step S3: Based on the stator and rotor voltages during the frequency or voltage fault process, determine the loss values ​​of each structural component during the fault process using the electromagnetic field calculation model. In a specific embodiment of the present invention, in step S3, the stator voltage and rotor voltage of the high-inertia energy storage type synchronous condenser during the fault process are used as excitation, and the loss distribution of each structural component is obtained through the electromagnetic field calculation model of the two-dimensional straight section and the three-dimensional end region.

[0036] Based on the stator and rotor currents and core magnetic field distribution obtained from the above simulation throughout the entire fault process, the loss variation law of stator and rotor cores, windings, and end structural components is calculated throughout the entire process from the occurrence to the end of the fault.

[0037] Step S4: Based on the ventilation system structure of the high-inertia energy storage type synchronous condenser, establish a fluid and heat coupling calculation model, and import the loss values ​​of each structural component as a heat source into the fluid and heat coupling calculation model to determine the transient temperature rise of each structural component. In a specific embodiment of the present invention, in step S4, the fluid and heat coupling calculation model is based on the three-dimensional flow and heat transfer control equations to simulate the flow and heat exchange process of the cooling medium inside the motor and obtain the transient temperature distribution of each structural component.

[0038] The fluid-heat coupling calculation model is based on computational fluid dynamics. By solving the complete Navier-Stokes equations and energy equations, and using the wall function method to handle near-wall flow, it simulates the turbulent flow and convective heat transfer process of the cooling medium in the complex internal air duct of the motor, thereby obtaining an accurate global temperature distribution.

[0039] Step S5: Determine the safe operating limit time of the high-inertia energy storage synchronous condenser under system frequency or voltage faults based on the maximum allowable temperature rise of each structural component.

[0040] In a specific embodiment of the present invention, in step S5, the safe operating limit time is determined based on the transient temperature rise and maximum allowable temperature of each structural component during the fault process, and the earliest time when the allowable temperature is reached among all structural components is taken as the safe operating limit time.

[0041] In one specific embodiment of the present invention, the excitation control system adopts a proportional-integral regulator combined with a droop control algorithm to dynamically calculate the excitation voltage commands for the d-axis and q-axis.

[0042] In a specific embodiment of the present invention, the fluid and heat coupling calculation model adopts the k-ε turbulence model and is combined with the wall function method to simulate the turbulent flow and convective heat transfer process of the cooling medium in the internal air duct of the motor.

[0043] Example 2 The present invention will now be described in further detail with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0044] like Figure 1 As shown, the core of this invention lies in establishing a high-precision numerical model of fully dynamic coupling of multiple physics fields (electromagnetism, circuitry, control, fluid dynamics, and heat) to achieve precise simulation of the internal electromagnetic and thermal behavior of high-inertia energy storage synchronous condensers during grid support transient processes and accurate definition of safety boundaries. The specific implementation process of the method is as follows: In step S1, a high-precision finite element electromagnetic field calculation model is constructed based on the detailed engineering drawings and electromagnetic parameters of the target high-inertia energy storage synchronous condenser. This model consists of two organically integrated parts: first, a two-dimensional transient electromagnetic field model for the straight section of the motor, accurately considering the material nonlinearity and eddy current effects of the straight section; and second, an independently established three-dimensional electromagnetic field model for the end region, accurately taking into account the end leakage magnetic field and its eddy current effects. The two models are coupled through an external circuit to jointly constitute an electromagnetic field solver for calculating transient losses.

[0045] Step S2 achieves closed-loop interaction between the control system and the electromagnetic field model. An excitation control system based on rotor field-oriented vector control is constructed, with its dual-closed-loop controller parameters tuned according to the specific motor characteristics. This system uses a phase-locked loop (PLL) to monitor the amplitude, frequency, and phase of the grid voltage in real time. Once a frequency or voltage deviation exceeds a threshold, the controller immediately calculates and outputs d-axis and q-axis excitation voltage commands based on preset droop characteristics and a PI adjustment algorithm. This process achieves strict bidirectional dynamic coupling: the controller's voltage commands are applied to the rotor windings of the electromagnetic field model in real time; simultaneously, the three-phase stator and rotor currents, flux linkages, electromagnetic torque, and real-time speed, calculated by the electromagnetic field model within each simulation step, are fed back to the controller via a data interface as input for its next calculation, thus realistically reproducing the dynamic interaction process of "control command - electromagnetic response" under fault conditions. To ensure equipment safety, the control system incorporates a speed control strategy: the motor's operating speed is strictly limited to within its mechanical strength limits. If the speed approaches its limit during support, the system automatically switches to no-load operation mode and maintains the current speed, prioritizing mechanical safety.

[0046] In step S3, the stator and rotor currents and core magnetic field distributions obtained from the above simulation during the entire fault process are used to calculate the loss variation law of the stator and rotor core, windings, and end structural components throughout the entire process from the occurrence to the end of the fault.

[0047] Step S4: Based on the ventilation system design and heat transfer coupling model of the motor, the loss data of various structural components calculated in Step S3 are accurately mapped as volumetric heat sources and loaded onto the corresponding solid domains in the flow-heat coupling model. By solving the three-dimensional, transient, incompressible Navier-Stokes equations and the solid thermal conductivity equation, and selecting the k-ε model and appropriate wall functions, the flow and heat transfer process of the cooling medium in the complex internal air duct of the motor is simulated. Finally, the temperature distribution law of each structural component inside the motor during the fault is calculated, and the temperature rise curves of key hot spots are extracted.

[0048] Step S5 involves determining the safety boundary. Let the set of critical structural components of the motor be {1, 2, ..., N}, where N is the total number of components. For any component i, its transient temperature rise after the fault begins is Ti(t), and the maximum allowable temperature of the component is Tmax,i. Then, the safe operating limit time tlimit of the high-inertia energy storage synchronous condenser under this fault is determined by the following formula: Figure 2The system topology diagram provided in this embodiment of the invention is shown below. The system mainly includes a high-inertia energy storage synchronous condenser, a flywheel coaxially connected to the motor rotor, a rotor-side converter (RSC), a grid-side converter (GSC), a DC bus capacitor, an excitation transformer, a step-up transformer, and a core excitation control system. The main parameters of the high-inertia energy storage synchronous condenser are shown in Table 1. The stator winding of the high-inertia energy storage synchronous condenser is connected to the grid via the step-up transformer, and its rotor winding is connected to the AC output terminal of the rotor-side converter. The flywheel is mechanically coaxially connected to the motor rotor, significantly increasing the rotational inertia and energy storage of the entire unit. The rotor-side converter and the grid-side converter are connected back-to-back via a DC bus, jointly realizing bidirectional power flow between the rotor circuit and the grid. The excitation transformer draws power from the low-voltage side of the step-up transformer to provide operating power to the rotor-side converter. A fault generation device can be installed in the line to simulate various grid fault conditions such as voltage dips and frequency fluctuations.

[0049] Table 1 Figure 3 This invention presents the frequency / voltage support control strategy employed by the rotor-side converter. The control process is as follows: The grid voltage frequency and amplitude are detected, and their deviations from reference values ​​are calculated. The frequency and voltage deviations are processed by corresponding PI regulators to generate active power reference values ​​P* and reactive power reference values ​​Q*, respectively. Through coordinate transformation, the control of AC quantities is decoupled into DC quantity control. The d-axis rotor current component reference value ird* is mainly used to adjust reactive power to support the grid voltage; the q-axis current component reference value irq* is mainly used to adjust active power to support the grid frequency. ird* and irq* are compared with the detected actual rotor current feedback value. The error signals are processed by the PI regulator and decoupled via feedforward to generate the required rotor voltage control signals urd* and urq*. Finally, a space vector pulse width modulation module generates a pulse signal to drive the rotor-side converter, thereby producing the required excitation voltage and achieving precise control of the high-inertia energy storage synchronous condenser.

[0050] By simulating a voltage fault in a three-phase short-circuit fault system at the line location and varying the fault resistance, the transient characteristics of the motor under different fault levels can be simulated. In this case, the simulated voltage drops to 0.8 pu, 0.6 pu, and 0.4 pu. Table 2 shows the maximum temperature of different structural components 10 seconds after the fault occurs. It can be seen that the rotor winding and rotor core experience the greatest temperature rise after the fault occurs. Figure 4The temperature rise curve of the rotor core of the high-inertia energy storage synchronous condenser provided in this embodiment of the invention under a three-phase short-circuit fault is shown. With 120℃ as the maximum allowable temperature of the rotor core, the maximum operating time of the high-inertia energy storage synchronous condenser is 6.42s when the voltage drops to 0.4pu, and it can continue to operate for more than 10s when the voltage drops to 0.8pu and 0.6pu.

[0051] Table 2 The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1The steps of the functions specified in one or more boxes. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the invention. Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0053] The methods and apparatus provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0054] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "a specific embodiment" or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions 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 this application.

Claims

1. A method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions, characterized in that, include: Step S1: Based on the electromagnetic design scheme of the high-inertia energy storage type synchronous condenser, establish electromagnetic field calculation models for the two-dimensional straight section and the three-dimensional end region; Step S2: Establish a frequency and voltage support excitation control system for a high-inertia energy storage type synchronous condenser, and dynamically couple the excitation control system with the electromagnetic field calculation model in both directions. Obtain the grid frequency and voltage through a phase-locked loop. When the system frequency or voltage deviates, the excitation control system calculates the excitation voltage based on the deviation value. Step S3: Based on the stator and rotor voltages during the frequency or voltage fault process, determine the loss values ​​of each structural component during the fault process using the electromagnetic field calculation model. Step S4: Based on the ventilation system structure of the high-inertia energy storage type synchronous condenser, establish a fluid and heat coupling calculation model, and import the loss values ​​of each structural component as a heat source into the fluid and heat coupling calculation model to determine the transient temperature rise of each structural component. Step S5: Determine the safe operating limit time of the high-inertia energy storage synchronous condenser under system frequency or voltage faults based on the maximum allowable temperature rise of each structural component. The bidirectional dynamic coupling is manifested as follows: the excitation voltage output by the excitation control system is applied to the rotor winding of the electromagnetic field model in real time as an excitation source; at the same time, the real-time response parameters of the motor calculated by the electromagnetic field model at each electrical time step, including stator and rotor current, flux linkage, and rotor speed, are fed back to the excitation control system through the data interface as input for its calculation in the next time step, thereby realistically reproducing the dynamic interaction between the control system and the complex electromagnetic response of the motor under fault conditions. In step S3, the stator voltage and rotor voltage of the high-inertia energy storage synchronous condenser during the fault process are used as excitation, and the loss distribution of each structural component is obtained through the electromagnetic field calculation model of the two-dimensional linear part and the three-dimensional end region.

2. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, In step S1, the two-dimensional straight section includes the stator core, the rotor core, the straight segment of the stator winding, and the straight segment of the rotor winding; the three-dimensional end region includes the stator end winding, the rotor end winding, the stator tooth pressure plate, the stator pressure ring, the rotor pressure ring, and the rotor retaining ring.

3. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, Step S2 includes: The excitation voltage output by the excitation control system is used as the excitation input to the electromagnetic field calculation model. At the same time, the stator current, rotor current, flux linkage and speed parameters of the motor calculated by the electromagnetic field calculation model are fed back to the excitation control system for real-time correction of the excitation voltage.

4. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, In step S2, when the absolute value of the grid frequency deviation exceeds the preset frequency dead zone threshold, the excitation control system calculates the q-axis excitation voltage based on the frequency deviation and controls the motor to enter either the deceleration generation mode or the acceleration motor mode; when the absolute value of the grid voltage deviation exceeds the preset voltage dead zone threshold, the excitation control system calculates the d-axis excitation voltage based on the voltage deviation and controls the motor to enter the phase adjustment mode.

5. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, In step S2, the operating speed of the high-inertia energy storage type synchronous condenser is limited to a preset safe operating speed range. If the speed reaches the boundary of the range, the control motor is switched to no-load operation.

6. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, In step S4, the fluid and heat coupling calculation model is based on the three-dimensional flow and heat transfer control equations to simulate the flow and heat exchange process of the cooling medium inside the motor and obtain the transient temperature distribution of each structural component.

7. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 1, characterized in that, In step S5, the safe operating limit time is determined based on the transient temperature rise and maximum allowable temperature of each structural component during the fault process, and the earliest time when the allowable temperature is reached among all structural components is taken as the safe operating limit time.

8. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 4, characterized in that, The excitation control system uses a proportional-integral regulator combined with a droop control algorithm to dynamically calculate the excitation voltage commands for the d-axis and q-axis.

9. The method for calculating the safe operating boundary of a high-inertia energy storage synchronous condenser under fault conditions according to claim 6, characterized in that, The fluid-thermal coupling calculation model adopts the k-ε turbulence model and the wall function method to simulate the turbulent flow and convective heat transfer process of the cooling medium in the internal air duct of the motor.

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