Grid connection control method and device for high-voltage cascaded energy storage system based on extremely weak grid

Abstract

The application discloses a weak grid-based high-voltage cascaded energy storage system network control method and equipment, which is used to solve the problem that the high-voltage cascaded energy storage system is difficult to run stably and continuously for a long time under a weak grid, and the system power oscillation is prone to occur, and even the protection is triggered to be off-grid. The method generates a voltage angle frequency deviation of the high-voltage cascaded energy storage system according to an active loop, and determines an output voltage phase reference; generates a voltage amplitude reference of the high-voltage cascaded energy storage system according to a voltage loop; calculates a power angle of the high-voltage cascaded energy storage system relative to a grid voltage according to the voltage angle frequency deviation; determines whether the output voltage phase reference is adjusted by a damping coefficient according to a set range corresponding to the power angle; and determines an output voltage of the high-voltage cascaded energy storage system according to the voltage amplitude reference and the adjusted output voltage phase reference. The method can dynamically adjust the active output, and guarantee the continuous and stable operation of the system under the weak grid.

Description

Technical Field

[0001] This application relates to the field of power electronic energy storage technology, and in particular to a network control method and equipment for a high-voltage cascaded energy storage system based on an extremely weak power grid. Background Technology

[0002] The short-circuit ratio (SCR) is a core quantitative indicator that characterizes the strength of a power grid. The higher the SCR value, the stronger the power grid, and the smaller the disturbance to the grid voltage amplitude and system frequency caused by power and current fluctuations on the grid side. Conversely, the lower the SCR value, the worse the power grid's ability to resist power disturbances, and even small changes in grid current may cause large fluctuations in grid voltage and frequency.

[0004] New energy power generation inherently possesses intermittent and fluctuating characteristics. Traditionally, dispatch control strategies such as AGC, AVC, and primary frequency regulation are used to allocate new energy power generation and energy storage, smoothing out power output fluctuations and maintaining grid voltage and frequency stability. With the rise of grid-connected technologies, energy storage systems with external voltage source characteristics can actively provide voltage and frequency support to the grid, offering significant advantages over traditional equipment and gradually becoming a mandatory requirement for grid connection. Among these, high-voltage cascaded energy storage systems, with their outstanding advantages such as large single-unit capacity, high operating efficiency, small footprint, and low grid-connected harmonic content, are widely used in the new energy storage market.

[0005] However, when large-capacity high-voltage cascaded energy storage systems are connected to extremely weak power grids, their own power switching and significant fluctuations further exacerbate grid voltage and frequency disturbances. Existing mainstream grid control algorithms are only applicable to conventional weak power grid scenarios with a power cascade response (SCR) ≥ 1. Once the grid SCR < 1 and random dynamic fluctuations exist, traditional grid control strategies cannot guarantee the long-term stable and continuous operation of the energy storage system, easily leading to system power oscillations and ultimately triggering protection disconnection, thus restricting the large-scale application of energy storage devices in extremely weak power grid scenarios. Summary of the Invention

[0006] This application provides a method and device for controlling the network construction of a high-voltage cascaded energy storage system based on an extremely weak power grid, in order to solve the problem that high-voltage cascaded energy storage systems under extremely weak power grids are difficult to operate stably and continuously for a long time, and are prone to system power oscillations or even triggering protection disconnection.

[0007] This application provides a method for controlling the network construction of a high-voltage cascaded energy storage system based on an extremely weak power grid, comprising: The voltage angular frequency deviation of the high-voltage cascaded energy storage system is generated based on the active power loop, and the output voltage phase reference is determined. The voltage amplitude reference of the high-voltage cascaded energy storage system is generated based on the voltage loop. Based on the voltage angular frequency deviation, calculate the power angle of the high-voltage cascaded energy storage system relative to the grid voltage; Based on the set range corresponding to the power angle, determine whether to adjust the output voltage phase reference by means of the attenuation coefficient; The output voltage of the high-voltage cascaded energy storage system is determined based on the voltage amplitude reference and the adjusted output voltage phase reference.

[0008] In one example, generating the voltage angular frequency of the high-voltage cascaded energy storage system based on the active power loop includes: Determine the first difference between the given active power and the actual active power of the high-voltage cascaded energy storage system; Based on the first difference, and the set active loop control coefficient and Laplace operator, the voltage angular frequency deviation of the high-voltage cascaded energy storage system is calculated.

[0009] In one example, determining the output voltage phase reference includes: The output voltage phase reference is calculated based on the voltage angular frequency deviation, the grid rated angular frequency, and the Laplace operator.

[0010] In one example, generating a voltage amplitude reference for the high-voltage cascaded energy storage system based on the voltage loop includes: Determine the second difference between the reference voltage and the real-time voltage of the high-voltage cascaded energy storage system; Based on the second difference, and the set voltage loop control coefficient and Laplace operator, the voltage amplitude reference of the high-voltage cascaded energy storage system is calculated.

[0011] In one example, calculating the power angle of the high-voltage cascaded energy storage system relative to the grid voltage based on the voltage angular frequency includes: The power angle of the high-voltage cascaded energy storage system relative to the grid voltage is calculated based on the voltage angular frequency deviation and the Laplace operator.

[0012] In one example, determining whether to adjust the output voltage phase reference by an attenuation coefficient based on a set range corresponding to the power angle includes: When the power angle exceeds the set range, the output voltage phase reference is adjusted by the attenuation coefficient; When the power angle does not exceed the set range, the output voltage phase reference is not adjusted.

[0013] In one example, adjusting the output voltage phase reference by an attenuation coefficient includes: By multiplying the attenuation coefficient by the active input, the given active power of the high-voltage cascaded energy storage system is reduced, and the reference phase of the output voltage is further reduced.

[0014] In one example, before determining whether to adjust the output voltage phase reference by an attenuation coefficient based on a set range corresponding to the power angle, the method further includes: The attenuation coefficient of the high-voltage cascaded energy storage system is calculated based on the voltage angular frequency deviation and the PI controller.

[0015] In one example, the attenuation coefficient ranges from -1 to 1.

[0016] This application provides a grid control device for a high-voltage cascaded energy storage system based on an extremely weak power grid, comprising: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which are executed by the at least one processor to enable the at least one processor to implement the above-described high-voltage cascaded energy storage system network control method based on extremely weak power grids.

[0017] This application provides a method and device for controlling the network construction of a high-voltage cascaded energy storage system based on an extremely weak power grid, which can achieve the following beneficial effects: Based on the power perspective, this method assesses whether the energy storage system is at risk of instability. By setting an attenuation coefficient and introducing it into the active power control loop, the system abandons the hard limitation of a fixed active power upper limit. It dynamically and adaptively adjusts the active power output when the grid strength changes, smoothly reducing power without impact before the risk of instability arises. This avoids the situation where the energy storage system oscillates and then fails and disconnects from the grid due to changes in grid strength, ensuring the continuous and stable operation of the high-voltage cascaded energy storage system under extremely weak grid conditions. At the same time, it maximizes power generation under stable operating conditions, ensuring that active power is generated to the fullest extent, and balancing power utilization and system stability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The accompanying drawings described herein are used to provide a further understanding of this application and constitute a part of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the accompanying drawings: Figure 1 A flowchart of a network control method for a high-voltage cascaded energy storage system based on an extremely weak power grid, provided in an embodiment of this application; Figure 2A schematic diagram of the network control method for a high-voltage cascaded energy storage system based on an extremely weak power grid provided in this application embodiment; Figure 3 A schematic diagram of a high-voltage cascaded energy storage system provided in this application embodiment; Figure 4 A schematic diagram of the network control equipment for a high-voltage cascaded energy storage system based on an extremely weak power grid, provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In a grid-type energy storage system, the control of the energy storage converter PCS includes three closed loops, with the outer loop consisting of an active power loop (Pf loop) and a voltage loop (QU loop).

[0021] The active power loop is used to receive active power commands from the upper-level dispatcher, compare them with the actual active power output of the PCS, eliminate power steady-state error, and generate a virtual voltage angular frequency. The output voltage phase is obtained through integration, as well as the inertia and damping of the simulated synchronous machine, to support the grid frequency.

[0022] The voltage loop is used to compare the given voltage with the actual voltage feedback, provide an output voltage amplitude reference, and simulate a synchronous generator excitation regulator to adjust the output voltage level, stabilize the grid connection point voltage, and regulate reactive power output.

[0023] Figure 1 The flowchart of the grid control method for a high-voltage cascaded energy storage system based on a very weak power grid provided in this application embodiment specifically includes the following steps: S101: Generate the voltage angular frequency of the high-voltage cascaded energy storage system based on the active power loop, and determine the output voltage phase reference.

[0024] In this embodiment, the three-phase voltage and current are collected in real time, the voltage angular frequency of the high-voltage cascaded energy storage system is generated through the active power loop, and the output voltage phase reference is calculated.

[0025] Specifically, based on the real-time collected three-phase voltage and current, the actual active power is calculated. Then, based on the given active power from the upper-level dispatch center, the power deviation between the given active power and the actual active power is calculated and used as the first difference. Based on this first difference, and the set active loop control coefficient and Laplace operator, the voltage angular frequency deviation of the high-voltage cascaded energy storage system is calculated.

[0026] In one possible implementation, the voltage angular frequency deviation is calculated using the following formula: Formula 1; Among them, △ ω This refers to the voltage angular frequency deviation. P ref For a given active power, P fed This represents the actual active power of the high-voltage cascaded energy storage system. k 1. a 1 represents the active power loop control coefficient. k 1 represents the proportional gain coefficient, used to amplify or reduce active power deviation, and can determine the active power regulation capability. a 1 is the inertial time constant correlation coefficient, used for low-pass filtering of power deviation, suppressing sampling noise, smoothing out instantaneous changes in active power, and effectively adding virtual damping to the system. Together, they constitute the correction link of the active power loop, which determines the response speed, damping, and stability margin of the active power loop. s is the Laplace operator.

[0027] Under extremely weak power grid conditions k The value of 1 should not be too large, otherwise it will affect the size of the subsequent power angle, making it easy to exceed the limit and disconnect from the grid; a The value of 1 can be slightly larger to cope with the situation of more disturbances in extremely weak power grids, which is more conducive to smoothing power fluctuations and reducing the frequent over-limit of power angle.

[0028] In one embodiment, the output voltage phase reference is calculated based on the calculated voltage angular frequency deviation, the grid rated angular frequency, and the Laplace operator. The voltage phase reference is a sinusoidal phase reference of the virtual output voltage of the high-voltage cascaded energy storage PCS itself, and is the core timing reference for generating the three-phase modulation waveform.

[0029] In one possible implementation, the voltage phase reference is calculated using the following formula: Formula 2; in, θ For the output voltage reference phase of the high-voltage cascaded energy storage system, Δ ω The voltage deviation angular frequency, ω n ω is the rated angular frequency of the power grid, and s is the Laplace operator.

[0030] S102: Generate a voltage amplitude reference for the high-voltage cascaded energy storage system based on the voltage loop.

[0031] The voltage amplitude reference is the magnitude of the virtual AC voltage of the high-voltage cascaded energy storage PCS itself, which, together with the phase reference of the active loop output, can synthesize a complete three-phase sinusoidal modulated voltage.

[0032] In one embodiment, the voltage deviation between a given reference voltage of the high-voltage cascaded energy storage system and a real-time voltage amplitude acquired in real time is determined as a second difference. Based on the second difference, the set voltage loop control coefficient, and the Laplace operator, the voltage amplitude reference of the high-voltage cascaded energy storage system is calculated.

[0033] In one possible implementation, the voltage amplitude reference is calculated using the following formula three: Formula 3; in, E out This serves as a reference for the voltage amplitude output of the high-voltage cascaded energy storage system. E ref Given the reference voltage of the high-voltage cascaded energy storage system, E fed For real-time voltage feedback of high-voltage cascaded energy storage systems. k 2. a 2 represents the voltage loop control coefficient. k 2 represents the proportional gain coefficient, used to amplify error signals, quickly correct the output, and affect steady-state voltage regulation accuracy. a 2 is the inertial time constant correlation coefficient, used to filter out high-frequency noise in sampling, smooth voltage fluctuations, add damping to the voltage loop, and suppress weak network resonance oscillations. s is the Laplace operator.

[0034] Under extremely weak power grid conditions k 2. It cannot be too large. If it is too large, it will cause the voltage loop to adjust too abruptly, the output voltage amplitude reference to fluctuate frequently and significantly, the reactive power to fluctuate violently back and forth, and induce voltage oscillation and harmonic amplification. a The value of 2 can be slightly larger, prioritizing ensuring the system does not oscillate, and then considering... k 2. Compensation a 2. The larger filter lag results in a sacrificed response speed.

[0035] S103: Calculate the power angle of the high-voltage cascaded energy storage system relative to the grid voltage based on the voltage angular frequency deviation.

[0036] The power angle represents the difference between the virtual output voltage phase of the energy storage PCS and the actual voltage phase of the grid, i.e., the phase difference between the two voltage vectors. The power angle directly reflects the amount of active power delivered by the energy storage system to the grid; a larger power angle indicates more power delivery. However, the power angle has a set safety range. If the power angle exceeds this range, the system will lose synchronization, causing power oscillations and converter tripping. Therefore, a larger power angle corresponds to a lower system stability margin, making it highly susceptible to instability and oscillations under extremely weak grid conditions. Thus, the power angle can serve as a core indicator for judging whether an energy storage system will become unstable and disconnect from the grid under extremely weak grid conditions. Using the power angle as a criterion for judging system instability allows for earlier prediction of system instability risks than simple voltage and frequency monitoring.

[0037] In one embodiment, the power angle of the high-voltage cascaded energy storage system relative to the grid voltage can be calculated based on the voltage angular frequency deviation and the Laplace operator.

[0038] In one possible implementation, the power angle can be calculated using the following formula: Formula 4; in, α For power angle, Δ ω Let be the voltage angular frequency deviation, and s be the Laplace operator.

[0039] S104: Based on the set range corresponding to the power angle, determine whether to adjust the output voltage phase reference by means of the attenuation coefficient.

[0040] The set range serves as a safe range for the power angle. Within the set range, the system can operate smoothly. If it exceeds the set range, intervention is required to avoid the risk of instability and oscillation.

[0041] In one embodiment, 90° is typically used as the critical value for the power angle. When the power angle is less than 90°, the system is stable; when the power angle is greater than 90°, the system becomes unstable, oscillates, or disconnects from the grid. Setting the upper limit of the set range to 90° is considered a critical situation; for safety, the upper limit of the set range can be set to less than 90°, which allows for a safety margin and better ensures the stability of the system.

[0042] In one embodiment, an attenuation coefficient can be set. When the power angle exceeds the set range, the output voltage phase reference is adjusted by the attenuation coefficient. When the power angle does not exceed the set range, the output voltage phase reference is not adjusted, and the power is directly dispatched at full capacity according to the upper layer scheduling.

[0043] Specifically, the attenuation coefficient is set to reduce the power angle. When the power angle rapidly increases, the rotational speed significantly exceeds the grid speed, and the angular frequency deviation becomes significantly larger. Therefore, the voltage angular frequency deviation can be used as a quantitative characterization signal of power angle instability. When intervening in the system, the magnitude of the attenuation coefficient is determined based on the magnitude of the voltage angular frequency deviation.

[0044] In one embodiment, the attenuation coefficient of the high-voltage cascaded energy storage system can be calculated based on the voltage angular frequency deviation and the PI controller. The voltage angular frequency deviation is positively correlated with the magnitude of the attenuation coefficient. The greater the grid disturbance and frequency shift, the greater the angular frequency deviation, indicating a higher degree of instability. Consequently, the absolute value of the corresponding attenuation coefficient is larger, resulting in a stronger reduction effect on active power and enabling more powerful intervention in the system.

[0045] In one possible implementation, the attenuation coefficient can be calculated using the following formula: Formula 5; Where λ is the attenuation coefficient, PI is a conventional PI controller, Δω is the voltage angular frequency deviation, and the attenuation coefficient ranges from -1 to 1.

[0046] In one embodiment, in order to adjust the output voltage phase reference through the attenuation coefficient, the attenuation coefficient is multiplied by the active input. Based on the range of the attenuation coefficient from -1 to 1, the given active power of the high-voltage cascaded energy storage system can be reduced, which can further reduce the output voltage reference phase and ultimately reduce the power angle.

[0047] In one possible implementation, a given active power can be reduced using the following formula six; Formula Six; in, P ref For a given active power, P in For active input to upper-level scheduling, α For power angle, β To define the range, λ is the attenuation coefficient.

[0048] As can be seen from Formula 6, when the power angle exceeds the set range, the system stability margin is insufficient. At this time, the attenuation coefficient is introduced into the dispatch active power input to reduce the given active power of the system and reduce the transmission power, thereby reducing the power angle, improving the system stability margin, and avoiding oscillation and grid disconnection.

[0049] S105: Determine the output voltage of the high-voltage cascaded energy storage system based on the voltage amplitude reference and the adjusted output voltage phase reference.

[0050] After determining whether to adjust the output voltage phase reference based on the power angle, the final output voltage phase reference is a safe value. The output voltage of the energy storage system obtained based on the voltage amplitude reference and the adjusted output voltage phase reference is also a safe value, and there will be no system instability problem.

[0051] In one possible implementation, the output voltage of the energy storage system can be represented by the following formula: Formula 7; in, u Aref , u Bref , u Cref This represents the instantaneous three-phase output voltage of the high-voltage cascaded energy storage system. θ As the reference phase for the output voltage, E out This serves as a reference for voltage amplitude.

[0052] In this embodiment, the risk of instability in the energy storage system is determined based on the power perspective. By setting an attenuation coefficient, the attenuation coefficient is introduced into the active power control loop, abandoning the hard limit of a fixed active power upper limit. When the grid strength changes, the active power output is dynamically and adaptively adjusted. Before the risk of instability occurs, the power is smoothly reduced without impact, avoiding the situation where the energy storage system oscillates and then fails and disconnects from the grid due to changes in grid strength. This ensures the continuous and stable operation of the high-voltage cascaded energy storage system under extremely weak grid conditions, while maximizing power generation under stable operating conditions, ensuring that active power is generated to the fullest extent, and taking into account both power utilization and system stability.

[0053] Figure 2 A schematic diagram of the network control method for a high-voltage cascaded energy storage system based on an extremely weak power grid, provided in an embodiment of this application.

[0054] like Figure 2 As shown, the upper part is the active power loop and the lower part is the voltage loop. The voltage phase reference output by the active power loop and the voltage amplitude reference output by the voltage loop work together to calculate the three-phase instantaneous reference voltage output by the high-voltage cascaded energy storage system, which is then fed into the PWM modulation to drive the high-voltage cascaded energy storage power unit and complete the closed-loop control.

[0055] Specifically, in the voltage loop, the given reference voltage is calculated. E ref and real-time voltage E fed The difference between them, multiplied multiply again Add E ref The voltage amplitude reference is obtained. Eout .

[0056] In the active power loop, calculate the given active power. P ref and actual active power P fed The difference between them, multiplied The voltage angular frequency deviation Δ is obtained. ω Based on the voltage angular frequency deviation Δ ω The attenuation coefficient λ is calculated using a PI controller and multiplied by the voltage angular frequency deviation. Calculate the power angle α Based on the magnitude of the power angle, determine whether dynamic adjustment is needed; if so, schedule the active power input. P in Multiply by the attenuation coefficient to reduce the given active power value; otherwise, do not adjust the dispatched active power input. Subsequently, after obtaining a suitable voltage angular frequency deviation, adjust the voltage angular frequency deviation Δ... ω and the rated angular frequency of the power grid ω n Addition, multiplication The output voltage reference phase is obtained. θ .

[0057] Based on voltage amplitude reference and voltage phase reference, the instantaneous values ​​of the three-phase output voltage of the high-voltage cascaded energy storage system are obtained and sent to the PWM modulation to drive the high-voltage cascaded energy storage power unit to complete closed-loop control.

[0058] Figure 3 This is a schematic diagram of a high-voltage cascaded energy storage system provided in an embodiment of this application.

[0059] like Figure 3 As shown, the high-voltage cascaded energy storage system includes a battery pack, power units M_xN, and filter reactors. N power units are connected in series to form a three-phase branch (abc), with each branch connected in parallel. Each power unit consists of four power semiconductors forming a bidirectional H-bridge. A DC bus filter capacitor is connected in parallel across the DC side of the H-bridge, and then the battery pack is connected in parallel. A filter reactor is connected in series at the output end of each cascaded phase before being connected to the power grid.

[0060] It should be noted that the high-voltage cascaded energy storage system network control method based on extremely weak power grid proposed in this application is not limited to the topology of the aforementioned high-voltage cascaded energy storage system. It has universality and can be applied to any feasible cascaded network energy storage system.

[0061] The above describes the network control method for a high-voltage cascaded energy storage system based on a very weak power grid, as provided in the embodiments of this application. Based on the same inventive concept, the embodiments of this application also provide corresponding network control equipment for a high-voltage cascaded energy storage system based on a very weak power grid, such as... Figure 4As shown.

[0062] Figure 4 The schematic diagram of the grid control equipment for a high-voltage cascaded energy storage system based on a very weak power grid provided in this application embodiment specifically includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which enables the at least one processor to implement the above-described grid control method for a high-voltage cascaded energy storage system based on a very weak power grid.

[0063] In this embodiment, the risk of instability in the energy storage system is determined based on the power perspective. By setting an attenuation coefficient, the attenuation coefficient is introduced into the active power control loop, abandoning the hard limit of a fixed active power upper limit. When the grid strength changes, the active power output is dynamically and adaptively adjusted. Before the risk of instability occurs, the power is smoothly reduced without impact, avoiding the situation where the energy storage system oscillates and then fails and disconnects from the grid due to changes in grid strength. This ensures the continuous and stable operation of the high-voltage cascaded energy storage system under extremely weak grid conditions, while maximizing power generation under stable operating conditions, ensuring that active power is generated to the fullest extent, and taking into account both power utilization and system stability.

[0064] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0065] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0066] The devices and methods provided in this application are one-to-one correspondences. Therefore, the devices also have similar beneficial technical effects as their corresponding methods. Since the beneficial technical effects of the methods have been described in detail above, the beneficial technical effects of the devices will not be repeated here.

[0067] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using dedicated hardware combined with computer instructions. The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0068] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus 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 apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0069] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A grid control method for a high-voltage cascaded energy storage system based on an extremely weak power grid, characterized in that, include: The voltage angular frequency deviation of the high-voltage cascaded energy storage system is generated based on the active power loop, and the output voltage phase reference is determined. The voltage amplitude reference of the high-voltage cascaded energy storage system is generated based on the voltage loop. Based on the voltage angular frequency deviation, calculate the power angle of the high-voltage cascaded energy storage system relative to the grid voltage; Based on the set range corresponding to the power angle, determine whether to adjust the output voltage phase reference by means of the attenuation coefficient; The output voltage of the high-voltage cascaded energy storage system is determined based on the voltage amplitude reference and the adjusted output voltage phase reference.

2. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, The generation of the voltage angular frequency of the high-voltage cascaded energy storage system based on the active power loop includes: Determine the first difference between the given active power and the actual active power of the high-voltage cascaded energy storage system; Based on the first difference, and the set active loop control coefficient and Laplace operator, the voltage angular frequency deviation of the high-voltage cascaded energy storage system is calculated.

3. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, The determination of the output voltage phase reference includes: The output voltage phase reference is calculated based on the voltage angular frequency deviation, the grid rated angular frequency, and the Laplace operator.

4. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, The step of generating a voltage amplitude reference for the high-voltage cascaded energy storage system based on the voltage loop includes: Determine the second difference between the reference voltage and the real-time voltage of the high-voltage cascaded energy storage system; Based on the second difference, and the set voltage loop control coefficient and Laplace operator, the voltage amplitude reference of the high-voltage cascaded energy storage system is calculated.

5. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, The step of calculating the power angle of the high-voltage cascaded energy storage system relative to the grid voltage based on the voltage angular frequency includes: The power angle of the high-voltage cascaded energy storage system relative to the grid voltage is calculated based on the voltage angular frequency deviation and the Laplace operator.

6. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, The step of determining whether to adjust the output voltage phase reference by means of an attenuation coefficient based on the set range corresponding to the power angle includes: When the power angle exceeds the set range, the output voltage phase reference is adjusted by the attenuation coefficient; When the power angle does not exceed the set range, the output voltage phase reference is not adjusted.

7. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 6, characterized in that, The adjustment of the output voltage phase reference by the attenuation coefficient includes: By multiplying the attenuation coefficient by the active input, the given active power of the high-voltage cascaded energy storage system is reduced, and the reference phase of the output voltage is further reduced.

8. The grid control method for high-voltage cascaded energy storage systems based on extremely weak power grids according to claim 1, characterized in that, Before determining whether to adjust the output voltage phase reference by attenuation coefficient according to the set range corresponding to the power angle, the method further includes: The attenuation coefficient of the high-voltage cascaded energy storage system is calculated based on the voltage angular frequency deviation and the PI controller.

9. The grid control method for high-voltage cascaded energy storage system based on extremely weak power grids according to claim 8, characterized in that, The attenuation coefficient ranges from -1 to 1.

10. A grid control device for a high-voltage cascaded energy storage system based on an extremely weak power grid, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which are executed by the at least one processor to enable the at least one processor to implement the grid control method for a high-voltage cascaded energy storage system based on an extremely weak power grid as described in any one of claims 1 to 9.

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