Method, device and equipment for supporting comprehensive inertia of doubly-fed variable-speed pumped storage unit based on excitation capacitor

Abstract

The invention relates to a doubly-fed variable-speed pumped storage unit comprehensive inertia supporting method, device and equipment based on an excitation capacitor. The method comprises the following steps: acquiring a frequency deviation value and a frequency deviation change rate of a grid-connected point after a load connected with a power system is suddenly changed; determining whether to start a comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate; if the comprehensive inertia control strategy is started, dynamically adjusting a DC bus voltage reference value according to the frequency deviation value to determine a d-axis modulation voltage component; acquiring additional electromagnetic increment power; controlling a grid-side converter in the power system to operate according to the d-axis modulation voltage component, controlling a machine-side converter in the power system to operate according to the additional electromagnetic increment power, and providing inertial current impact support for the power system; and if the comprehensive inertia control strategy is not started, the frequency of the power system is kept stable and synchronous, and the doubly-fed variable-speed pumped storage unit of the power system is controlled to work in a constant power state.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of inertia control of power systems, and in particular to a method, device and equipment for comprehensive inertia support of a doubly-fed variable-speed pumped storage unit based on field excitation capacitance. BACKGROUND

[0002] Under the background of global energy structure transformation and climate governance coordinated development, improving the flexibility of the power system has become the core demand of the construction of the new power system. With the advent of the power system with new energy connected to the power grid, the installed capacity of wind and light-based new energy has shown explosive growth, and its inherent intermittent and fluctuating characteristics have posed unprecedented challenges to the dynamic regulation capacity of the power grid. As the most mature and optimal large-scale energy storage method, pumped storage plays a key role in grid frequency regulation, peak shaving and new energy consumption due to its rapid power response characteristics and cross-period energy transfer capability.

[0003] The current doubly-fed variable-speed pumped storage unit adopts a structure combining reversible pump-turbines and doubly-fed induction generators (DFIGs). Compared with traditional synchronous machines, it has significant technical advantages in terms of operating efficiency improvement, reactive power decoupling control and grid dynamic support. In existing engineering practice, the machine-side converter generally adopts power control or speed-reactive control strategies, and the grid-side converter maintains the stability of the DC bus voltage through voltage and current double-loop control. Although this control strategy can meet the demand of conventional load regulation, it has obvious limitations in the inertia support requirements of the new power system. Currently, the inertia support control of doubly-fed induction generators mostly adopts the introduction of traditional virtual inertia control in the machine-side converter, which can significantly improve the inertia of the power system, but does not consider that the voltage and current double-loop control of the grid-side converter will reduce the inertia support power due to traditional constant voltage control during inertia support, thereby weakening the inertia support capability of the variable-speed pumped storage unit.

[0004] Many control strategies have been proposed for the inertia support of doubly-fed wind turbines, such as: integrated inertia control, which simulates the characteristics of synchronous machines through virtual inertia; variable parameter control, which dynamically adjusts the droop coefficient based on wind speed to improve the frequency modulation margin; standby power control, which optimizes power output through an adaptive algorithm; rotor fast recovery control, which introduces pitch angle compensation and slip rate monitoring to alleviate power drop problems; in terms of collaborative control, wind turbine-synchronous machine combined with diesel generator set to quickly respond to fill the power gap, and wind turbine-energy storage system to improve response speed through fuzzy logic hierarchical control. By improving the control link (such as proportional-differential correction negative damping), constructing a power curve model, and establishing a multi-energy collaborative mechanism, the problems of steady-state frequency difference, secondary frequency drop, and multi-unit mismatch are effectively solved, significantly enhancing the grid frequency fluctuation adaptability and system dynamic stability. However, under steady-state wind speed, the output of the prime mover is restricted by mechanical inertia, resulting in relatively limited regulation margin. In contrast, variable-speed pumped storage units can actively adjust the output parameters of the prime mover through coordinated adjustment of guide vane opening and speed, thereby forming a core frequency modulation advantage that distinguishes them from wind turbines.

[0005] Existing virtual inertia control strategies for doubly-fed pumped storage units in power systems do not consider the problem of weakened frequency support response of pumped storage unit systems caused by the increase in active power of the grid-side converter due to capacitor voltage drop. SUMMARY

[0006] The present application provides a doubly-fed variable-speed pumped storage unit integrated inertia support method, device and equipment based on excitation capacitor, which is used to solve the technical problem that existing virtual inertia control strategies for doubly-fed pumped storage units do not consider capacitor voltage drop, thereby weakening the frequency support response of pumped storage unit power systems.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] On the one hand, a doubly-fed variable-speed pumped storage unit integrated inertia support method based on excitation capacitor is provided, which is applied to a power system containing a doubly-fed variable-speed pumped storage unit. The doubly-fed variable-speed pumped storage unit integrated inertia support method includes the following steps:

[0009] Obtain the frequency deviation value and the frequency deviation change rate of the grid point after the load connected to the power system changes suddenly;

[0010] According to the frequency deviation value and the frequency deviation change rate, determine whether to start the integrated inertia control strategy;

[0011] If the integrated inertia control strategy is started, a d-axis modulation voltage component is determined according to dynamic adjustment of a DC bus voltage reference value based on the frequency deviation value; an additional electromagnetic incremental power is obtained; the grid-side converter in the power system is controlled to operate according to the d-axis modulation voltage component, and the machine-side converter in the power system is controlled to operate according to the additional electromagnetic incremental power, thereby providing inertia current impact support for the power system;

[0012] If the integrated inertia control strategy is not started, the frequency of the power system remains in a steady-state synchronization, and the doubly-fed variable-speed pumped storage unit of the power system is controlled to work in a constant power state.

[0013] Preferably, determining the d-axis modulation voltage component according to dynamic adjustment of the DC bus voltage reference value based on the frequency deviation value comprises:

[0014] The DC bus voltage of the power system, the rated angular velocity of the power grid, the rated voltage of the capacitor, the linear capacitance value, the rated capacity of the unit, the capacitor voltage variation, the power grid angular velocity variation, the rated frequency of the power grid, the d-axis grid-side input current component, the grid-side d-axis voltage outer loop control parameter and the grid-side d-axis current inner loop control parameter are obtained;

[0015] The equivalent virtual inertia constant of the energy storage capacitor in the power system is calculated according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation and the power grid angular velocity variation;

[0016] The dynamically adjusted DC bus voltage reference value is calculated according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid and the rated voltage of the capacitor;

[0017] The d-axis current reference value of the grid-side converter is calculated according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value;

[0018] The d-axis modulation voltage component of the grid-side converter is calculated according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter.

[0019] Preferably, the integrated inertia support method for the doubly-fed variable-speed pumped storage unit based on the field capacitor further comprises: the equivalent virtual inertia constant of the energy storage capacitor in the power system is calculated according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation and the power grid angular velocity variation by using a virtual inertia constant formula; the virtual inertia constant formula is:

[0020]

[0021] where H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitor value, is the rated angular velocity of the power grid, U c is the linear bus capacitor voltage, is the capacitor rated voltage, is the angular velocity variation of the power grid, is the capacitor voltage variation, S N is the rated capacity of the unit, is the angular velocity of the power grid.

[0022] Preferably, the excitation capacitor-based integrated inertia support method of the doubly-fed variable-speed pumped storage unit further comprises: obtaining a dynamically adjusted DC bus voltage reference value by using a reference voltage formula according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid and the capacitor rated voltage; the reference voltage formula is:

[0023]

[0024] where H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitor value, is the capacitor rated voltage, S N is the rated capacity of the unit, f0 is the rated frequency of the power grid, is the frequency deviation value, is the DC bus voltage reference value.

[0025] Preferably, the excitation capacitor-based integrated inertia support method of the doubly-fed variable-speed pumped storage unit further comprises: obtaining a d-axis current reference value of the grid-side converter by using a current reference formula according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value; obtaining a d-axis modulation voltage component of the grid-side converter by using a modulation voltage formula according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter; the current reference formula is:

[0026]

[0027] the modulation voltage formula is:

[0028]

[0029] where, is the DC bus voltage reference value, is the DC bus voltage, and are the proportional coefficient and the integral coefficient of the grid-side d-axis voltage outer loop control parameter, respectively, s is the Laplace operator, is a d-axis current reference value of the grid-side converter; is a d-axis grid-side input current component, and are a proportional coefficient and an integral coefficient of a grid-side d-axis current inner loop control parameter, respectively, d_ref is a d-axis modulation voltage component of the grid-side converter.

[0030] In another aspect, a synthetic inertia support device based on field excitation capacitance of a doubly-fed variable-speed pumped storage unit is provided, which is applied to a power system containing a doubly-fed variable-speed pumped storage unit, and the synthetic inertia support device includes a frequency data acquisition module, a judgment module, a first execution module, and a second execution module.

[0031] The frequency data acquisition module is configured to acquire a frequency deviation value and a frequency deviation change rate of a grid connection point after a sudden change of a load connected to the power system.

[0032] The judgment module is configured to determine whether to start a synthetic inertia control strategy according to the frequency deviation value and the frequency deviation change rate.

[0033] The first execution module is configured to, according to starting the synthetic inertia control strategy, dynamically adjust a d-axis modulation voltage component according to the frequency deviation value, acquire an additional electromagnetic incremental power, control a grid-side converter in the power system to operate according to the d-axis modulation voltage component, control a machine-side converter in the power system to operate according to the additional electromagnetic incremental power, and provide an inertia current impact support for the power system.

[0034] The second execution module is configured to, according to not starting the synthetic inertia control strategy, keep the frequency of the power system in a steady-state synchronization, and control the doubly-fed variable-speed pumped storage unit in the power system to work in a constant power state.

[0035] Preferably, the first execution module includes a data acquisition submodule, an inertia data calculation submodule, a voltage calculation submodule, a current calculation submodule, and a modulation voltage calculation submodule.

[0036] The data acquisition submodule is configured to acquire a DC bus voltage of the power system, a grid rated angular velocity, a capacitance rated voltage, a linear capacitance value, a unit rated capacity, a capacitance voltage variation, a grid angular velocity variation, a grid rated frequency, a d-axis grid-side input current component, a grid-side d-axis voltage outer loop control parameter, and a grid-side d-axis current inner loop control parameter.

[0037] The inertia data calculation sub-module is configured to calculate an equivalent virtual inertia constant of the energy storage capacitor in the power system according to the grid rated angular velocity, the straight-line capacitance value, the capacitor rated voltage, the unit rated capacity, the capacitor voltage variation and the grid angular velocity variation.

[0038] The voltage calculation sub-module is configured to calculate a dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the unit rated capacity, the frequency deviation value, the grid rated frequency and the capacitor rated voltage.

[0039] The current calculation sub-module is configured to calculate a d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value.

[0040] The modulation voltage calculation sub-module is configured to calculate a d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter.

[0041] Preferably, the inertia data calculation sub-module is further configured to calculate the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the grid rated angular velocity, the straight-line capacitance value, the capacitor rated voltage, the unit rated capacity, the capacitor voltage variation and the grid angular velocity variation by using a virtual inertia constant formula; and the virtual inertia constant formula is as follows:

[0042]

[0043] wherein H is the equivalent virtual inertia constant of the energy storage capacitor, C is the straight-line capacitance value, is the grid rated angular velocity, U c is the straight-line bus capacitor voltage, is the capacitor rated voltage, is the grid angular velocity variation, is the capacitor voltage variation, S N is the unit rated capacity, is the grid angular velocity.

[0044] Preferably, the voltage calculation sub-module is further configured to calculate a dynamic adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the unit rated capacity, the frequency deviation value, the grid rated frequency and the capacitor rated voltage by using a reference voltage formula; the current calculation sub-module is further configured to calculate a d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value by using a current reference formula; the modulation voltage calculation sub-module is further configured to calculate a d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter by using a modulation voltage formula; the reference voltage formula is:

[0045]

[0046] The current reference formula is:

[0047]

[0048] The modulation voltage formula is:

[0049]

[0050] In the formula, is a DC bus voltage reference value, is a DC bus voltage, and are a proportional coefficient and an integral coefficient of a grid-side d-axis voltage outer loop control parameter respectively, and s is a Laplace operator, is a d-axis current reference value of the grid-side converter; is a d-axis grid-side input current component, and are a proportional coefficient and an integral coefficient of a grid-side d-axis current inner loop control parameter respectively, and e d_ref is a d-axis modulation voltage component of the grid-side converter; H is an equivalent virtual inertia constant of an energy storage capacitor, and C is a linear capacitance value, is a capacitor rated voltage, S N is a unit rated capacity, and f0 is a grid rated frequency, is a frequency deviation value.

[0051] In still another aspect, a terminal device is provided, comprising a processor and a memory;

[0052] The memory is configured to store program code and transmit the program code to the processor;

[0053] The processor is configured to execute the above-mentioned method for providing comprehensive inertia support for a doubly-fed variable-speed pumped storage unit based on an excitation capacitor according to instructions in the program code.

[0054] The method, device and equipment for providing comprehensive inertia support for a doubly-fed variable-speed pumped storage unit based on an excitation capacitor are applied to a power system containing a doubly-fed variable-speed pumped storage unit. The method includes obtaining a frequency deviation value and a frequency deviation change rate of a grid connection point after a sudden change of a load connected to the power system; determining whether to start a comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate; if the comprehensive inertia control strategy is started, determining a d-axis modulation voltage component according to a dynamically adjusted DC bus voltage reference value; obtaining an additional electromagnetic incremental power; controlling a grid-side converter in the power system to operate according to the d-axis modulation voltage component and controlling a machine-side converter in the power system to operate according to the additional electromagnetic incremental power, thereby providing an inertia current impact support for the power system; and if the comprehensive inertia control strategy is not started, keeping the frequency of the power system stable and synchronous and controlling the doubly-fed variable-speed pumped storage unit in the power system to work in a constant power state.

[0055] As can be seen from the above technical solutions, the method for providing comprehensive inertia support for a doubly-fed variable-speed pumped storage unit based on an excitation capacitor determines whether to start a comprehensive inertia control strategy by real-time monitoring of a frequency deviation value and a frequency deviation change rate of a power system. In the comprehensive inertia control strategy, a d-axis modulation voltage component is calculated according to a dynamically adjusted DC bus voltage reference value to control a grid-side converter to operate, and a machine-side converter is controlled to operate according to an additional electromagnetic incremental power. The capacitor energy is efficiently converted into effective grid inertia support, which improves the inertia support capability of the power system and improves the inertia support capability of the power system to the grid. The technical problem that the virtual inertia control strategy of the existing doubly-fed pumped storage unit does not consider capacitor voltage drop and thus causes the frequency support response of the pumped storage unit power system to be weakened is solved.

[0056] The comprehensive inertia control strategy proposed by the device for providing comprehensive inertia support for a doubly-fed variable-speed pumped storage unit based on an excitation capacitor through a frequency data acquisition module, a judgment module, a first execution module and a second execution module significantly enhances the inertia support capability of the power system, realizes flexible control of a DC bus voltage reference value and improves the active regulation capability of an excitation system DC bus capacitor. When the grid load suddenly changes, the comprehensive inertia control strategy can effectively suppress the frequency fluctuation of the power system. BRIEF DESCRIPTION OF DRAWINGS

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0058] Figure 1 The step flow chart of the excitation capacitor-based comprehensive inertia support method for the doubly-fed variable-speed pumped storage unit in the embodiments of the present application;

[0059] Figure 2 The control block diagram of the excitation capacitor-based comprehensive inertia support method for the doubly-fed variable-speed pumped storage unit in the embodiments of the present application;

[0060] Figure 3 The topology schematic diagram of the power system containing the doubly-fed variable-speed pumped storage unit in the excitation capacitor-based comprehensive inertia support method for the doubly-fed variable-speed pumped storage unit in the embodiments of the present application;

[0061] Figure 4 The simulation comparison diagram of the power system when the grid load suddenly increases in the excitation capacitor-based comprehensive inertia support method for the doubly-fed variable-speed pumped storage unit in the embodiments of the present application;

[0062] Figure 5 The frame schematic diagram of the excitation capacitor-based comprehensive inertia support device for the doubly-fed variable-speed pumped storage unit in the embodiments of the present application;

[0063] Figure 6 The schematic diagram of the terminal device in the embodiments of the present application. DETAILED DESCRIPTION

[0064] In order to make the purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] In the description of the embodiments of the present application, the terms "first" and "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0066] In the embodiments of the present application, unless specifically defined and limited otherwise, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or it can be detachable connection, or it can be integrated; it can be mechanical connection, or it can be electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0067] The embodiments of the present application provide a double-fed variable-speed pumped storage unit comprehensive inertia support method, device and equipment based on excitation capacitor, which solves the technical problem that the existing virtual inertia control strategy of double-fed pumped storage unit does not consider capacitor voltage drop, thereby causing the power system frequency support response of pumped storage unit to be weakened.

[0068] Embodiment one:

[0069] Figure 1 The step flow chart of the double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitor described in the embodiments of the present application, Figure 2 The control block diagram of the double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitor described in the embodiments of the present application, Figure 3 The topological diagram of the power system containing the double-fed variable-speed pumped storage unit in the double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitor described in the embodiments of the present application. In Figure 2 , Indicates that the input variable is squared.

[0070] The embodiments of the present application provide a double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitor, which is applied to a power system containing a double-fed variable-speed pumped storage unit. The topological structure of the power system containing the double-fed variable-speed pumped storage unit is as shown in Figure 3 The double-fed variable-speed pumped storage unit includes an optimal speed control system, a mechanical system and an alternating current excitation system. The optimal speed control system includes an optimal speed generator, a speed regulator and a mechanical guide vane; the mechanical system includes a water pump / turbine and a large-capacity induction motor DFIG; the alternating current excitation system includes an excitation converter and an excitation control system, and the excitation converter mainly includes a machine-side converter, a direct current bus capacitor and a grid-side converter. The excitation control system includes a machine-side converter controller and a grid-side converter controller.

[0071] It should be noted that the double-fed motor controls the electromagnetic power by using stator flux linkage orientation control according to the power reference instruction; the water pump turbine controls the power according to the given reference power of the generator set and water head calculating the optimal reference speed of the generator output The speed of the generator set is controlled by adjusting the mechanical guide vane through the governor. is the opening degree of the governor output; and respectively, the stator output angular velocity deviation and the grid angular velocity deviation, which can be approximately considered to be equal; is the stator output power deviation after the traditional inertia control by the stator output angular velocity deviation, also known as adaptive electromagnetic power increment; is the reactive power reference value of the stator output; is the reactive power reference value of the grid-side converter output, which can generally be set to 0, or can be combined with the reactive droop control to realize certain grid voltage support.

[0072] As shown in Figure 1 and Figure 2 , the embodiment of the present application provides a double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitance, comprising the following steps:

[0073] S1. Obtain the frequency deviation value and the frequency deviation rate of change of the grid connection point after the load connected to the power system is suddenly changed.

[0074] It should be noted that in step S1, the data of the change of the grid frequency after the load connected to the power system is suddenly changed is obtained, which provides data for subsequent judgment of whether to start the comprehensive inertia control strategy. The data includes the frequency deviation value and the frequency deviation rate of change In the embodiment, when the load of the power system is suddenly changed (such as power shortage or surplus), the grid frequency deviates from the rated value, and is accompanied by significant frequency change dynamics, the power system monitors the frequency deviation value and the frequency deviation value of the grid connection point in real time, and obtains the frequency deviation rate of change .

[0075] S2. Determine whether to start the comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation rate of change.

[0076] It should be noted that in step S2, whether to start the comprehensive inertia control strategy is determined according to the data obtained in step S1. In the embodiment, when the absolute value of the frequency deviation value is greater than the frequency deviation starting threshold k1, and the frequency deviation rate of change the absolute value of the frequency variation rate is greater than the frequency variation rate starting threshold k2, like the criterion formula, it is determined that the power system needs emergency inertia support, and the integrated inertia control strategy is triggered immediately. The frequency deviation starting threshold k1 and the frequency variation rate starting threshold k2 are both natural numbers not equal to 0, and the specific values can be set according to actual needs.

[0077] In the embodiment of the present application, the criterion formula is:

[0078]

[0079] The criterion formula effectively distinguishes between small and slow fluctuations and severe frequency disturbances that require rapid response.

[0080] S3. If the integrated inertia control strategy is started, the d-axis modulation voltage component is determined according to the dynamic adjustment of the DC bus voltage reference value according to the frequency deviation value; the additional electromagnetic incremental power is obtained; the grid-side converter in the power system is controlled according to the d-axis modulation voltage component, and the machine-side converter in the power system is controlled according to the additional electromagnetic incremental power, to provide inertia current impact support for the power system.

[0081] It should be noted that in step S3, the data obtained in step S1 satisfies the criterion formula of step S2, and the integrated inertia control strategy is started immediately, and the machine-side converter RSC and the grid-side converter GSC cooperatively perform the following control actions. In this embodiment, in the process of controlling the machine-side converter in the power system according to the additional electromagnetic incremental power, the frequency deviation value and the frequency deviation variation rate are detected in real time, and the adaptive additional electromagnetic incremental power ΔP is dynamically injected to increase the active power output of the variable-speed pumped storage unit, to provide power support for the grid frequency fluctuation. The size of the additional electromagnetic incremental power ΔP is usually proportional to the frequency deviation value and the frequency deviation variation rate . The additional electromagnetic incremental power ΔP is derived from the rapid release of the rotor kinetic energy of the generator set (manifested as a controlled temporary drop in the allowable speed), which significantly increases the active power injected (or absorbed) by the generator set to the grid, to provide rapid power support in the first time. In the process of controlling the grid-side converter in the power system according to the d-axis modulation voltage component, the frequency deviation value and the frequency deviation variation rate are detected in real time, and the DC bus voltage reference value is dynamically reduced according to the real-time frequency deviation value This operation causes the DC bus capacitor to release its stored electrical energy in reverse to the grid, and the grid-side converter GSC outputs additional active power (or absorbs power). The DC bus capacitor energy release action has extremely fast response speed (milliseconds), providing extremely fast inertia current impact support for the grid, effectively suppressing the frequency change rate; at the same time, in order to prevent misoperation when the frequency tends to be stable, when the frequency deviation change rate is continuously zero within a set short time window (such as 0.05s), the virtual inertia control of the grid-side converter GSC is automatically locked out, and the dynamic adjustment of the DC bus voltage reference value is stopped. Otherwise, the grid-side converter GSC will continue to adjust the DC bus voltage reference value according to the frequency deviation value . .

[0082] In the embodiments of the present application, the additional electromagnetic incremental power ΔP is calculated according to the frequency deviation value and the frequency deviation change rate . The power increment formula is ΔP=K p × +K d × , where K p is the proportional coefficient of the traditional inertia control in the machine-side converter, and K d is the integral coefficient of the traditional inertia control in the machine-side converter.

[0083] In the embodiments of the present application, the double-fed variable-speed pumped storage unit comprehensive inertia support method based on the excitation capacitor further includes that when the comprehensive inertia control strategy is started, the frequency deviation value and the frequency deviation change rate are acquired in real time, and when the frequency deviation value and the frequency deviation change rate do not satisfy the criterion formula, the comprehensive inertia control strategy is controlled to stop running according to the exit mechanism. It can be understood that when the frequency of the power system is restored to a stable value in response to the comprehensive inertia control strategy, the power system stops the inertia response through the set inertia control system frequency deviation and change rate judgment interval, at this time the double-fed variable-speed pumped storage unit speed gradually recovers to a stable value, and the variable-speed pumped storage unit returns to a constant power state.

[0084] It should be noted that as the comprehensive inertia control strategy plays a supporting role, the frequency of the power system begins to recover. In order to ensure that the generator set returns to a steady state smoothly according to the exit mechanism. The content of the exit mechanism includes:

[0085] Phase one: (partial exit of the frequency deviation change rate of the grid-side converter GSC and the machine-side converter RSC): when the frequency deviation change rate When the absolute value of the frequency change rate is less than the frequency change rate trigger threshold k2 and remains so for more than a set duration (e.g., 0.05s), it indicates the end of the period of drastic frequency change in the grid. At this time, the entire virtual inertial control function of the grid-side converter GSC (including the DC bus voltage reference value) should be immediately stopped. (Adjustments were made), and the grid-side converter's GSC returned to normal control mode. Simultaneously, the frequency deviation rate of change in the RSC inertial control of the machine-side converter was adjusted. Control stops.

[0086] Phase Two: (Frequency Deviation Value of RSC of Machine-Side Converter) Partial Exit): Only when the frequency deviation of the power system further decreases and the rate of change of frequency deviation stabilizes. The frequency deviation value in the RSC of the machine-side converter is stopped only when the absolute value is less than the frequency change rate start threshold k2. The virtual inertial control loop (i.e., stopping the output of additional electromagnetic incremental power ΔP) ensures that the frequency deviation value is within acceptable limits. When the frequency deviation of the power system remains relatively large but changes gradually, the RSC converter on the generator side continues to provide the necessary power support. If the frequency deviation threshold k1 is still greater than the steady-state threshold, it indicates a persistent power imbalance in the power system. Therefore, the RSC of the generator-side converter is based on the frequency deviation value. The power support control will continue to operate, maintaining the output of the additional electromagnetic incremental power ΔP until the frequency deviation value is reached. The absolute value is less than the frequency deviation start-up threshold k1. The frequency deviation change rate of the RSC on the machine-side converter. After the control is deactivated and maintained for a period of time, the turbine governor begins to take over, gradually restoring the rotor speed to the optimal operating point by adjusting the guide vane opening or pump power. At the same time, the generator set's power output re-tracks the given reference power. It eventually and smoothly switched back to constant power operation mode.

[0087] In this embodiment, the process of stopping the inertial response is as follows: when the frequency deviation rate of the power system decreases to 0 and remains so for a period of time (e.g., 0.05s), the virtual inertial controller for the frequency deviation rate of the generator-side converter stops, and the entire virtual inertial controller for the grid-side converter stops. The virtual inertial control of the frequency deviation of the generator-side converter only stops operating when the frequency deviation rate of the power system is less than the frequency deviation rate activation threshold k2. When the steady-state frequency deviation value of the power system is greater than the frequency deviation activation threshold k1, the frequency deviation inertial support control of the generator-side converter continues to operate, adding an additional electromagnetic incremental power ΔP to the generator-side converter.

[0088] S4. If the integrated inertia control strategy is not started, the frequency of the power system remains stable synchronization, and the doubly-fed variable speed pumped storage unit of the power system is controlled to work in a constant power state.

[0089] It should be noted that in step S4, the data obtained in step S1 does not satisfy the criterion formula of step S2, the integrated inertia control strategy is not started, and the power system containing the doubly-fed variable speed pumped storage unit is operated in a stable operation mode. The stable operation mode can be understood as when the grid frequency is stable at the rated frequency (such as 50Hz), the integrated inertia control strategy is in standby state, and the doubly-fed variable speed pumped storage unit outputs power to track the given reference power , the water turbine governor controls the rotor speed to work at the optimal speed, and the doubly-fed variable speed pumped storage unit works in a constant power output mode.

[0090] In the embodiment of the present application, the integrated inertia support method of the doubly-fed variable speed pumped storage unit based on the excitation capacitor determines to start the integrated inertia control strategy by monitoring the frequency deviation value and the frequency deviation change rate of the power system in real time. In the integrated inertia control strategy, the dynamic adjustment of the DC bus voltage is performed to make the power electronic converter exhibit inertia dynamic response characteristics similar to synchronous machines, thereby efficiently converting capacitor energy into effective grid inertia support, and effectively improving the inertia support capability of the power system.

[0091] It should be noted that the integrated inertia support method of the doubly-fed variable speed pumped storage unit based on the excitation capacitor can introduce the capacitor of the grid-side converter DC bus into the inertia support control, so that the inertia support of the doubly-fed pumped storage unit is further improved on the basis of the original traditional control, and the inertia support capability of the power grid is greatly improved.

[0092] The application provides a double-fed variable-speed pumped storage unit comprehensive inertia support method based on field excitation capacitance, which is applied to a power system containing a double-fed variable-speed pumped storage unit. The double-fed variable-speed pumped storage unit comprehensive inertia support method comprises the following steps: obtaining a frequency deviation value and a frequency deviation change rate of a grid connection point after a sudden change of a load connected to the power system; determining whether to start a comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate; if the comprehensive inertia control strategy is started, determining a d-axis modulation voltage component according to a dynamically adjusted DC bus voltage reference value; obtaining an additional electromagnetic incremental power; controlling the operation of a grid-side converter in the power system according to the d-axis modulation voltage component and controlling the operation of a machine-side converter in the power system according to the additional electromagnetic incremental power, thereby providing inertia current impact support for the power system; and if the comprehensive inertia control strategy is not started, keeping the frequency of the power system stable and synchronous and controlling the double-fed variable-speed pumped storage unit of the power system to work in a constant power state. The double-fed variable-speed pumped storage unit comprehensive inertia support method based on field excitation capacitance determines whether to start the comprehensive inertia control strategy by monitoring the frequency deviation value and the frequency deviation change rate of the power system in real time, calculates the d-axis modulation voltage component to control the operation of the grid-side converter according to the dynamically adjusted DC bus voltage reference value in the comprehensive inertia control strategy, controls the operation of the machine-side converter according to the additional electromagnetic incremental power, and efficiently converts the capacitor energy storage into effective power grid inertia support, thereby effectively improving the inertia support capability of the power system, improving the inertia support capability of the power system for the power grid, and solving the technical problem that the existing virtual inertia control strategy of the double-fed pumped storage unit does not consider the capacitor voltage drop, thereby weakening the frequency support response of the pumped storage unit power system.

[0093] In an embodiment of the application, dynamically adjusting the DC bus voltage reference value according to the frequency deviation value to determine the d-axis modulation voltage component comprises the following steps:

[0094] obtaining the DC bus voltage of the power system, the rated angular velocity of the power grid, the rated voltage of the capacitor, the linear capacitance value, the rated capacity of the unit, the capacitor voltage variation, the angular velocity variation of the power grid, the rated frequency of the power grid, the d-axis grid-side input current component, the grid-side d-axis voltage outer loop control parameter and the grid-side d-axis current inner loop control parameter;

[0095] calculating the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation and the angular velocity variation of the power grid;

[0096] calculating the dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid and the rated voltage of the capacitor;

[0097] According to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value, a d-axis current reference value of the grid-side converter is obtained;

[0098] According to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter, a d-axis modulation voltage component of the grid-side converter is obtained.

[0099] It should be noted that the introduction of the equivalent virtual inertia constant H in the voltage and current double closed loop control of the grid-side converter not only can reasonably utilize the DC bus capacitor of the grid-side converter to realize the power balance of the excitation system of the generator-side converter, but also can improve the inertia of the power system when the grid frequency fluctuates, reduce the positive deterioration of the grid-side converter control on the power system frequency fluctuation, cause secondary drop and improve the dynamic response of the power system to the frequency. If the grid load changes, the virtual inertia control of the grid-side converter is started, the above-mentioned virtual inertia control is added to the original d-axis capacitor voltage control of the grid-side converter to form a comprehensive inertia control strategy, so that the voltage reference value of the DC bus capacitor is no longer a fixed value, but a new DC bus voltage reference value dynamically adjusted according to the frequency deviation value, so as to determine a new d-axis modulation voltage component. The comprehensive inertia control strategy can continuously adjust the DC bus voltage reference value according to the change of the power system frequency by simulating the inertia link of the synchronous generator, and at the same time provides certain inertia support for the power system as the transmission intermediate of the power balance between the generator-side converter and the grid-side converter of the excitation system. The specific control block diagram is shown in Figure 2

[0100] In an embodiment of the present application, the excitation capacitor-based comprehensive inertia support method of the doubly-fed variable-speed pumped storage unit further comprises: obtaining an equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the grid, the linear capacitor value, the capacitor rated voltage, the rated capacity of the unit, the capacitor voltage variation and the angular velocity variation of the grid by using a virtual inertia constant formula for calculation; the virtual inertia constant formula is:

[0101]

[0102] In the formula, H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitor value, is the rated angular velocity of the grid, generally set to 100π; c is the linear bus capacitor voltage, is the capacitor rated voltage, is the angular velocity variation of the grid, is the capacitor voltage variation, S N is the rated capacity of the unit, is the angular velocity of the grid.

[0103] ​It should be noted that the comprehensive inertia support method for the doubly-fed variable-speed pumped storage unit based on the excitation capacitor first calculates the equivalent virtual inertia constant of the energy storage capacitor according to the virtual inertia constant formula, providing data for the subsequent calculation of the dynamically adjusted DC bus voltage reference value. According to the virtual inertia constant formula, the equivalent rotational inertia time constant of the energy storage capacitor (such as the DC bus capacitor) is determined by factors such as the system frequency, capacitor value, and voltage across the capacitor. The value of the virtual inertia time constant of the energy storage capacitor can be set by changing the capacitor value. In this embodiment, according to the virtual inertia constant formula, the terminal voltage of the DC capacitor of the grid-side converter can be expressed as the dynamic change of related parameters such as system frequency deviation and virtual inertia constant. Therefore, the virtual inertia control strategy of the grid-side converter can be designed using the virtual inertia constant formula. According to the virtual inertia constant formula, when the frequency of the power system is less than the rated frequency, the DC bus voltage reference value of the grid-side converter is also less than the nominal voltage value. The grid-side converter will reduce the forward active power transmission. When the frequency deviation value... At higher frequencies, the grid-side converter may even reverse power flow to provide active power support for the power system in response to frequency changes. When the power system frequency is higher than the rated frequency, the reference value of the DC bus voltage of the grid-side converter will be higher than the nominal power value. At this time, the DC bus capacitor is in a charging state, absorbing excess active power from the grid and maintaining the stability of the power system frequency. The rated frequency and nominal voltage values ​​can be set according to actual needs.

[0104] In the embodiments of this application, most current virtual inertia control is based on the motion equations and electromagnetic transient equations of synchronous generators, and all of them control the simulated inertial support characteristics of synchronous machines. The rotor swing equation of a traditional synchronous generator is:

[0105]

[0106] In the formula, Let be the moment of inertia of the synchronous generator. The electric angular velocity of the synchronous generator rotor. and These represent the mechanical torque and electromagnetic torque of the synchronous generator, respectively. and respectively. The inertia of the synchronous generator is an inherent property of its physical characteristics, which represents the mechanical inertia capability of the rotor system to resist the change of the rotational speed. The value of the inertia is determined by the structural design of the generator and remains constant. In power system analysis, the inertia time constant H is a key parameter to measure the energy reserve of the generator, which is defined as the ratio between the kinetic energy stored in the rotor system and its rated capacity under the rated speed condition. The physical meaning of the inertia time constant H can be interpreted as: when the generator continuously releases kinetic energy to the load at the rated capacity, the mechanical energy stored in the rotor can support the system operation for a certain duration. The conventional mathematical expression of the inertia time constant H can be expressed as:

[0107]

[0108] wherein, is the rated capacity of the synchronous generator in the power system, is the rated angular speed of the synchronous generator. Substituting the inertia time constant H into the rotor motion equation of the synchronous generator, the first formula can be obtained, and the expression of the first formula is:

[0109]

[0110] It can be seen from the inertia time constant H that the synchronous generator can realize active power regulation through the kinetic energy stored in the rotor. Similarly, it can be considered that the large-capacity capacitor can realize rapid charging and discharging of active power regulation through voltage change, and the two are similar in principle. Therefore, the DC capacitor of the pumped storage excitation converter can be regarded as a virtual inertia energy storage component. In normal operation, the charging and discharging modes of the energy storage capacitor mainly include constant voltage and current limiting charging and constant current and voltage limiting charging. Constant voltage and current limiting charging refers to that the voltage across the capacitor remains almost unchanged during charging and discharging, and the charging and discharging current determines the charging and discharging power. This charging and discharging mode is mainly used when the capacity of the energy storage capacitor is large. During constant current charging and discharging, the charging and discharging current of the capacitor remains unchanged, and the capacitor voltage changes continuously with the charging and discharging process. The current size affects the charging and discharging power, and the current can be limited to achieve rapid power support when the load suddenly changes. When using constant current charging and discharging, the terminal voltage of the energy storage capacitor will change continuously with the charging and discharging process, and the power change equation of the energy storage capacitor can be approximately written as:

[0111]

[0112] wherein, is the terminal voltage of the energy storage capacitor, is the power change of the energy storage capacitor at the charging and discharging moment, c is the bus capacitor voltage, so the charging and discharging power of the energy storage capacitor can be expressed as a function of the terminal voltage The second formula can be obtained by combining the first formula of the swing equation of the rotor with the power variation equation, and the expression of the second formula is:

[0113]

[0114] Therefore, the energy storage capacitor energy storage characteristic can be equivalent to the rotor energy storage characteristic of the synchronous generator, and the virtual inertia constant formula of the equivalent virtual inertia constant of the energy storage capacitor in the power system can be obtained by integrating and simplifying the expression of the second formula on both sides.

[0115] In an embodiment of the present application, the excitation capacitor-based integrated inertia support method of the double-fed variable-speed pumped storage unit further comprises: obtaining a dynamically adjusted DC bus voltage reference value by using a reference voltage formula to calculate the equivalent virtual inertia constant, the unit rated capacity, the frequency deviation value, the grid rated frequency and the capacitor rated voltage; the reference voltage formula is:

[0116]

[0117] In the formula, H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitance value, is the capacitor rated voltage, S N is the unit rated capacity, f0 is the grid rated frequency, and is generally set to 50 Hz; is the frequency deviation value, is the DC bus voltage reference value.

[0118] It should be noted that the excitation capacitor-based integrated inertia support method of the double-fed variable-speed pumped storage unit uses the reference voltage formula to calculate the dynamically adjusted DC bus voltage reference value. In this embodiment, the size of the linear capacitance value of the DC bus capacitor reflects the size of the virtual rotor inertia, so when the energy storage capacitor of the grid-side converter is used to provide virtual rotor inertia, a suitable capacitor capacity of the grid-side converter needs to be selected. Within the allowable range of the frequency deviation value of the power system and the capacitor voltage of the grid-side converter, the corresponding relationship between the capacitor voltage of the grid-side converter and the equivalent virtual inertia constant can be obtained, and the capacitor formula is:

[0119]

[0120] The reference voltage formula of the capacitor at both ends of the grid-side converter containing the equivalent virtual inertia constant can be obtained by combining the capacitor formula with the virtual inertia constant formula.

[0121] In an embodiment of the present application, the excitation capacitor-based comprehensive inertia support method of the doubly-fed variable-speed pumped storage unit further comprises: obtaining a d-axis current reference value of the grid-side converter by using a current reference formula to calculate according to the DC bus voltage, a grid-side d-axis voltage outer loop control parameter, and a DC bus voltage reference value; and obtaining a d-axis modulation voltage component of the grid-side converter by using a modulation voltage formula to calculate according to a d-axis grid-side input current component, the d-axis current reference value, and a grid-side d-axis current inner loop control parameter.

[0122]

[0123] The modulation voltage formula is:

[0124]

[0125] In the formula, is a DC bus voltage reference value, is a DC bus voltage, and are a proportional coefficient and an integral coefficient of the grid-side d-axis voltage outer loop control parameter, respectively, and s is a Laplace operator, is a d-axis current reference value of the grid-side converter; is a d-axis grid-side input current component, and are a proportional coefficient and an integral coefficient of the grid-side d-axis current inner loop control parameter, respectively, and e d_ref is a d-axis modulation voltage component of the grid-side converter.

[0126] Figure 4 is a simulation comparison diagram of the power system in the excitation capacitor-based comprehensive inertia support method of the doubly-fed variable-speed pumped storage unit according to an embodiment of the present application when the grid load suddenly increases.

[0127] In an embodiment of the present application, a variable-speed pumped storage unit grid-connected simulation model as shown in Figure 3 is built by using a simulation software platform of a power system, wherein the pumped storage capacity is 333.4 MW, the pumped storage unit stator and the excitation converter are connected to the grid through a main transformer with a voltage of 230 kV, the initial output of the pumped storage unit stator side is 240 MW, the system rated load is 300 MW, and a 130 MW load is connected at 6s. At t=6s, the system load suddenly increases from 300 MW to 430 MW, the system frequency drops, and the simulation result is shown in Figure 4 As can be seen from (a) of Figure 4 , when the system load suddenly increases by 130 MW, only the traditional comprehensive inertia control is used, the lowest value of the system frequency drop is 49.750 Hz, and after the virtual inertia control is added to the grid-side converter, the lowest value of the system frequency drop is improved to 49.836 Hz, and the lowest value of the system frequency drop is improved by 34.4%. As can be seen from (b) ofFigure 4 (b) can be known that after the grid-side converter adds virtual inertia, the active power output of the pumped storage unit increases from 240MW to 253MW, an increase of 13MW, which is due to the virtual inertia control of the grid-side converter, which reduces the reference voltage of the grid-side converter to 17.1kV, which reduces the input active power of the grid-side converter, thereby increasing the active power output of the variable-speed pumped storage unit and supporting the frequency drop of the system. According to Figure 4 The simulation results of (b) further verify that the comprehensive inertia control strategy proposed by the comprehensive inertia support device based on the excitation capacitor of the double-fed variable-speed pumped storage unit significantly enhances the inertia support capability of the power system, realizes the flexible control of the DC bus voltage reference value, and improves the active regulation capability of the DC bus capacitor of the excitation system. When the load of the power grid changes suddenly, the comprehensive inertia control strategy can effectively suppress the frequency fluctuation of the power system.

[0128] Embodiment two:

[0129] Figure 5 The framework schematic diagram of the comprehensive inertia support device based on the excitation capacitor of the double-fed variable-speed pumped storage unit described in the embodiments of the present application.

[0130] As shown in Figure 3 and Figure 5 , the embodiments of the present application provide a comprehensive inertia support device based on the excitation capacitor of the double-fed variable-speed pumped storage unit, which is applied to a power system containing a double-fed variable-speed pumped storage unit. The comprehensive inertia support device based on the excitation capacitor of the double-fed variable-speed pumped storage unit comprises a frequency data acquisition module 10, a judgment module 20, a first execution module 30 and a second execution module 40;

[0131] The frequency data acquisition module 10 is used to acquire the frequency deviation value and the frequency deviation change rate of the grid connection point after the load connected to the power system changes suddenly;

[0132] The judgment module 20 is used to determine whether to start the comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate;

[0133] The first execution module 30 is used to dynamically adjust the DC bus voltage reference value to determine the d-axis modulation voltage component according to the frequency deviation value, acquire the additional electromagnetic incremental power, control the operation of the grid-side converter in the power system according to the d-axis modulation voltage component, control the operation of the machine-side converter in the power system according to the additional electromagnetic incremental power, and provide inertia current impact support for the power system according to the starting of the comprehensive inertia control strategy;

[0134] The second execution module 40 is used to control the double-fed variable-speed pumped storage unit of the power system to work in a constant power state according to the frequency of the power system remaining in a steady state synchronization according to the non-starting of the comprehensive inertia control strategy.

[0135] It should be noted that the content of the modules in the second embodiment device has been described in the content of the steps in the first embodiment method, and the content of the modules in the second embodiment device will not be repeated in this embodiment. In this embodiment, the comprehensive inertia support device based on the excitation capacitor of the doubly-fed variable-speed pumped storage unit significantly enhances the inertia support capability of the power system, realizes the flexible control of the DC bus voltage reference value, and improves the active regulation capability of the DC bus capacitor of the excitation system. The comprehensive inertia control strategy can effectively suppress the frequency fluctuation of the power system when the load of the power grid suddenly changes.

[0136] In the embodiments of the present application, the first execution module 30 includes a data acquisition sub-module, an inertia data calculation sub-module, a voltage calculation sub-module, a current calculation sub-module, and a modulation voltage calculation sub-module;

[0137] The data acquisition sub-module is configured to acquire the DC bus voltage of the power system, the rated angular velocity of the power grid, the rated voltage of the capacitor, the linear capacitance value, the rated capacity of the unit, the capacitor voltage variation, the power grid angular velocity variation, the rated frequency of the power grid, the d-axis grid-side input current component, the grid-side d-axis voltage outer loop control parameter, and the grid-side d-axis current inner loop control parameter.

[0138] The inertia data calculation sub-module is configured to calculate the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation, and the power grid angular velocity variation.

[0139] The voltage calculation sub-module is configured to calculate the dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid, and the rated voltage of the capacitor.

[0140] The current calculation sub-module is configured to calculate the d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter, and the DC bus voltage reference value.

[0141] The modulation voltage calculation sub-module is configured to calculate the d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value, and the grid-side d-axis current inner loop control parameter.

[0142] In the embodiments of the present application, the inertia data calculation sub-module is further configured to calculate the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation, and the power grid angular velocity variation using a virtual inertia constant formula; the virtual inertia constant formula is:

[0143]

[0144] wherein H is an equivalent virtual inertia constant of the energy storage capacitor, C is a linear capacitance value, is a rated angular velocity of the power grid, U c is a linear busbar capacitance voltage, is a rated voltage of the capacitor, is an angular velocity variation of the power grid, is a capacitance voltage variation, S N is a rated capacity of the unit, is an angular velocity of the power grid.

[0145] In the embodiment of the present application, the voltage calculation submodule is further configured to calculate a DC busbar voltage reference value after dynamic adjustment by using a reference voltage formula according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid and the rated voltage of the capacitor; the current calculation submodule is further configured to calculate a d-axis current reference value of the grid-side converter by using a current reference formula according to the DC busbar voltage, grid-side d-axis voltage outer loop control parameters and the DC busbar voltage reference value; and the modulation voltage calculation submodule is further configured to calculate a d-axis modulation voltage component of the grid-side converter by using a modulation voltage formula according to a d-axis grid-side input current component, the d-axis current reference value and grid-side d-axis current inner loop control parameters; and the reference voltage formula is:

[0146]

[0147] the current reference formula is:

[0148]

[0149] the modulation voltage formula is:

[0150]

[0151] wherein, is a DC busbar voltage reference value, is a DC busbar voltage, and are a proportional coefficient and an integral coefficient of the grid-side d-axis voltage outer loop control parameters respectively, and s is a Laplace operator, is a d-axis current reference value of the grid-side converter; is a d-axis grid-side input current component, and are a proportional coefficient and an integral coefficient of the grid-side d-axis current inner loop control parameters respectively, and e d_ref is a d-axis modulation voltage component of the grid-side converter; H is an equivalent virtual inertia constant of the energy storage capacitor, C is a linear capacitance value, is a rated voltage of the capacitor, SN f0 is the rated capacity of the unit, f0 is the rated frequency of the power grid, is the frequency deviation value.

[0152] Embodiment three:

[0153] Figure 6 is a schematic diagram of the terminal device described in the embodiments of the present application.

[0154] As Figure 6 shown, the embodiments of the present application provide a terminal device, comprising a processor and a memory;

[0155] The memory is used to store program code and transmit the program code to the processor;

[0156] The processor is used to execute the above-mentioned double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitance according to the instructions in the program code.

[0157] It should be noted that the processor is used to execute the steps in the above-mentioned one embodiment of the double-fed variable-speed pumped storage unit comprehensive inertia support method based on excitation capacitance according to the instructions in the program code. Alternatively, the processor executes the computer program to realize the functions of each module / unit in the above-mentioned system / device embodiments.

[0158] For example, the computer program can be divided into one or more modules / units, one or more modules / units are stored in the memory and executed by the processor to complete the present application. One or more modules / units can be a series of computer program instruction segments that can complete a specific function, which is used to describe the execution process of the computer program in the terminal device.

[0159] The terminal device can be a desktop computer, a notebook, a palm computer and a cloud server, etc. The terminal device can include, but is not limited to, a processor, a memory. Those skilled in the art can understand that it does not constitute a limitation on the terminal device, and can include more or less components than the illustration, or combine certain components, or different components, for example, the terminal device can also include input / output devices, network access devices, buses, etc.

[0160] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic components, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0161] The memory can be an internal storage unit of the terminal device, such as a hard disk or a memory of the terminal device. The memory can also be an external storage device of the terminal device, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal device. Further, the memory can include both the internal storage unit and the external storage device of the terminal device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or will be output.

[0162] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0163] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0164] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. According to actual needs, part or all of the units can be selected to achieve the purpose of the embodiment scheme.

[0165] In addition, each function unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software function unit.

[0166] The integrated unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application, essentially or the part that contributes to the prior art, or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0167] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for integrated inertia support of doubly-fed variable-speed pumped storage units based on field excitation capacitance, applied to a power system containing doubly-fed variable-speed pumped storage units, characterized in that, The method comprises the following steps. Obtain the frequency deviation value and the frequency deviation change rate of the grid connection point after the sudden change of the load connected to the power system; Determine whether to start the comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate; If the comprehensive inertia control strategy is started, dynamically adjust the DC bus voltage reference value according to the frequency deviation value to determine the d-axis modulation voltage component; obtain the additional electromagnetic incremental power; control the operation of the grid-side converter in the power system according to the d-axis modulation voltage component, and control the operation of the machine-side converter in the power system according to the additional electromagnetic incremental power, to provide inertia current impact support for the power system; If the comprehensive inertia control strategy is not started, the frequency of the power system remains stable and synchronous, and the doubly-fed variable-speed pumped storage unit of the power system is controlled to work in a constant power state.

2. The excitation capacitor based integrated inertia support method for doubly fed variable speed pumped storage units as claimed in claim 1 wherein, Dynamically adjusting the DC bus voltage reference value according to the frequency deviation value to determine the d-axis modulation voltage component comprises: Obtain the DC bus voltage of the power system, the rated angular velocity of the power grid, the rated voltage of the capacitor, the linear capacitance value, the rated capacity of the unit, the capacitor voltage variation, the grid angular velocity variation, the rated frequency of the power grid, the d-axis grid-side input current component, the grid-side d-axis voltage outer loop control parameter, and the grid-side d-axis current inner loop control parameter; Calculate the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation, and the grid angular velocity variation; Calculate the dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid, and the rated voltage of the capacitor; Calculate the d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter, and the DC bus voltage reference value; Calculate the d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value, and the grid-side d-axis current inner loop control parameter.

3. The method of claim 2, wherein the method is characterized by, Further comprising: Calculate the equivalent virtual inertia constant of the energy storage capacitor in the power system according to the rated angular velocity of the power grid, the linear capacitance value, the rated voltage of the capacitor, the rated capacity of the unit, the capacitor voltage variation, and the grid angular velocity variation by using a virtual inertia constant formula; the virtual inertia constant formula is: where H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitance value, is the rated angular velocity of the power grid, U c is the linear busbar capacitor voltage, is the rated voltage of the capacitor, is the angular velocity variation of the power grid, is the capacitor voltage variation, S N is the rated capacity of the unit, is the angular velocity of the power grid.

4. The method of claim 2, wherein, Further comprising: Calculate the dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the rated capacity of the unit, the frequency deviation value, the rated frequency of the power grid, and the rated voltage of the capacitor by using a reference voltage formula; the reference voltage formula is: In the formula, H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitance value, is the capacitor rated voltage, S N is the unit rated capacity, f0 is the rated frequency of the power grid, is the frequency deviation value, is the DC bus voltage reference value.

5. The method of claim 2, wherein, Further comprising: Calculate the d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter, and the DC bus voltage reference value by using a current reference formula; The d-axis modulation voltage component of the grid-side converter is obtained by using a modulation voltage formula according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter; the current reference formula is: The modulation voltage formula is: wherein, is a DC bus voltage reference value, is a DC bus voltage, and are a proportional coefficient and an integral coefficient of the grid-side d-axis voltage outer loop control parameter, respectively, s is a Laplace operator, is a d-axis current reference value of the grid-side converter; is a d-axis grid-side input current component, and are a proportional coefficient and an integral coefficient of the grid-side d-axis current inner loop control parameter, respectively, e d_ref is a d-axis modulation voltage component of the grid-side converter.

6. A synthetic inertia support device based on the field excitation capacitance of a doubly-fed variable-speed pumped storage unit, applied to a power system containing a doubly-fed variable-speed pumped storage unit, characterized in that, The double-fed variable-speed pumped storage unit comprehensive inertia support device comprises a frequency data acquisition module, a judgment module, a first execution module and a second execution module; The frequency data acquisition module is configured to acquire a frequency deviation value and a frequency deviation change rate of a grid connection point after a load connected to the power system experiences a sudden change; The judgment module is configured to determine whether to start a comprehensive inertia control strategy according to the frequency deviation value and the frequency deviation change rate; The first execution module is configured to, according to starting the comprehensive inertia control strategy, dynamically adjust a d-axis modulation voltage component according to the frequency deviation value, acquire an additional electromagnetic incremental power, control the grid-side converter in the power system to operate according to the d-axis modulation voltage component, control the machine-side converter in the power system to operate according to the additional electromagnetic incremental power, and provide inertia current impact support for the power system; The second execution module is configured to, according to not starting the comprehensive inertia control strategy, keep the frequency of the power system in a steady state synchronization, and control the double-fed variable-speed pumped storage unit of the power system to work in a constant power state.

7. The excitation capacitor based doubly-fed variable speed pumped storage unit integrated inertia support device according to claim 6, characterized in that, The first execution module comprises a data acquisition submodule, an inertia data calculation submodule, a voltage calculation submodule, a current calculation submodule and a modulation voltage calculation submodule; The data acquisition submodule is configured to acquire a DC bus voltage of the power system, a grid rated angular velocity, a capacitor rated voltage, a straight-line capacitance value, a unit rated capacity, a capacitor voltage variation, a grid angular velocity variation, a grid rated frequency, a d-axis grid-side input current component, a grid-side d-axis voltage outer loop control parameter and a grid-side d-axis current inner loop control parameter; The inertia data calculation submodule is configured to calculate an equivalent virtual inertia constant of an energy storage capacitor in the power system according to the grid rated angular velocity, the straight-line capacitance value, the capacitor rated voltage, the unit rated capacity, the capacitor voltage variation and the grid angular velocity variation; The voltage calculation submodule is configured to calculate a dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the unit rated capacity, the frequency deviation value, the grid rated frequency and the capacitor rated voltage; The current calculation submodule is configured to calculate a d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value; The modulation voltage calculation submodule is configured to calculate a d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter.

8. The excitation capacitor based doubly-fed variable speed pumped storage unit integrated inertia support device according to claim 7, characterized in that, The inertia data calculation sub-module is further configured to calculate an equivalent virtual inertia constant of the energy storage capacitor in the power system according to the grid rated angular velocity, the linear capacitance value, the capacitor rated voltage, the unit rated capacity, the capacitor voltage variation and the grid angular velocity variation by using a virtual inertia constant formula, and the virtual inertia constant formula is: where H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitance value, is the rated angular velocity of the power grid, U c is the linear bus capacitance voltage, is the rated voltage of the capacitor, is the angular velocity variation of the power grid, is the capacitor voltage variation, S N is the rated capacity of the unit, is the angular velocity of the power grid.

9. The excitation capacitor based integrated inertia support for doubly-fed variable speed pumped storage units of claim 7, wherein, The voltage calculation sub-module is further configured to calculate a dynamically adjusted DC bus voltage reference value according to the equivalent virtual inertia constant, the unit rated capacity, the frequency deviation value, the grid rated frequency and the capacitor rated voltage by using a reference voltage formula, and the reference voltage formula is: The current calculation sub-module is further configured to calculate a d-axis current reference value of the grid-side converter according to the DC bus voltage, the grid-side d-axis voltage outer loop control parameter and the DC bus voltage reference value by using a current reference formula, and the current reference formula is: The modulation voltage calculation sub-module is further configured to calculate a d-axis modulation voltage component of the grid-side converter according to the d-axis grid-side input current component, the d-axis current reference value and the grid-side d-axis current inner loop control parameter by using a modulation voltage formula, and the modulation voltage formula is: The current reference formula is: The modulation voltage formula is: In the formula, is the DC bus voltage reference value, is the DC bus voltage, and respectively are the proportional coefficient and integral coefficient of the grid-side d-axis voltage outer loop control parameter, s is the Laplace operator, is the d-axis current reference value of the grid-side converter; is the d-axis grid-side input current component, and respectively are the proportional coefficient and integral coefficient of the grid-side d-axis current inner loop control parameter, e d_ref is the d-axis modulation voltage component of the grid-side converter; H is the equivalent virtual inertia constant of the energy storage capacitor, C is the linear capacitance value, is the capacitor rated voltage, S N is the unit rated capacity, f0 is the rated frequency of the power grid, is the frequency deviation value.

10. A terminal device, comprising: The device comprises a processor and a memory. The memory is configured to store program code and transmit the program code to the processor. The processor is configured to execute the method according to any one of claims 1-5 based on the excitation capacitor of the double-fed variable-speed pumped storage unit comprehensive inertia support method according to instructions in the program code.

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