New energy and grid-connected unit hysteresis switching method and system based on short-circuit ratio and operating short-circuit ratio
Patent Information
- Application Number
- CN202610997400.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-06
- Publication Date
- 2026-09-29
AI Technical Summary
但实际运行场景中，除电网阻抗可能发生变化外，机组的功率变化更为常见，仅基于SCR的切换策略无法适配功率波动带来的系统工况变化，难以保证全工况下的系统稳定性
[0022]与现有方法相比，本申请的有益效果是：针对不同类型的变流器机组采用差异化的切换指标，跟网型机组采用可适配功率波动的OSCR作为判据，构网型机组采用SCR作为判据，兼顾了工况适应性与构网型机组的主动支撑能力，充分发挥了两类控制模式的互补优势，解决了传统统一切换策略的适配性不足问题。在模式切换过程中引入积分重置器，有效减小了切换瞬间的冲击电流，避免了切换过程中的电气冲击，提升了模式切换过程的平稳性。本申请通过差异化的阈值设计，有效拓宽了滞环切换的环宽范围，提升了系统的稳定运行区间，避免了不同工况下的系统振荡问题，保证了全工况下并网系统的稳定运行。
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Abstract
Description
Technical Field
[0001] This application belongs to the field of new energy grid control technology, and relates to a hysteresis switching method and system for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio. Background Technology
[0002] With the large-scale integration of new energy sources, the proportion of power electronic converters in the distribution network is increasing. There are two types of converters in the grid-connected system: grid-connected and grid-building. The two types of converters have complementary characteristics in small-signal stability and can improve the overall damping level of the system through flexible control mode switching.
[0003] Traditional hysteresis switching control primarily targets scenarios involving changes in grid impedance. It optimizes stability based on the performance characteristics of grid-aligned and grid-connected converters under strong and weak grid conditions, switching to grid-aligned control when the short-circuit ratio (SCR) is high (strong grid) and grid-connected control when the SCR is low (weak grid). However, in actual operation, in addition to potential changes in grid impedance, unit power fluctuations are more common. Switching strategies based solely on SCR cannot adapt to the system operating condition changes caused by power fluctuations, making it difficult to guarantee system stability under all operating conditions.
[0004] Meanwhile, during the traditional mode switching process, a large inrush current is easily generated at the moment of switching, which affects the stable operation of the system; and the existing technology uses a unified switching index for the two types of converters, which cannot take into account the active support capability of grid-connected units and makes it difficult to give full play to the complementary advantages of the two control modes.
[0005] In summary, the adaptive mode switching strategy of the converter is very important for the safe and stable operation of the grid-connected system. However, the existing control strategies have problems such as being unable to adapt to power fluctuation conditions, having large switching impacts, and being unable to take into account the characteristics of different types of units. Therefore, there is an urgent need for a more adaptable hysteresis switching strategy. Summary of the Invention
[0006] The purpose of this application is to provide a hysteresis switching method and system for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio, and to adopt appropriate switching indicators for different types of converter units in order to achieve stable system operation under all operating conditions.
[0007] To achieve the above objectives, this application adopts the following technical solution: Firstly, this application provides a hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio, including: Obtain the system operating parameters of the generating units in the grid-connected system; The control type of the unit is identified as either a grid-connected unit or a grid-connected unit. In response to the fact that the generating unit is a grid-connected generating unit, a first type of switching index is calculated based on the system operating parameters, wherein the first type of switching index characterizes the comprehensive information of the actual output of the generating unit and the grid strength; In response to the fact that the unit is a grid-connected unit, a second type of switching index is calculated based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; Based on the type of the unit, the calculated first-type or second-type switching index is compared with the corresponding hysteresis switching threshold to determine whether to trigger a control mode switch. Based on the comparison results, the control unit is switched to either a grid-following control mode or a grid-connected control mode.
[0008] As a further improvement to this application, the step of identifying the control type of the unit as a grid-connected unit or a network-structured unit includes: Based on the equipment identification or preset control parameters of the unit, the units are classified into grid-connected units and grid-connected units.
[0009] As a further improvement to this application, in response to the unit being a grid-connected unit, the calculation of a first type of switching index based on the system operating parameters includes: In response to the fact that the unit is a grid-connected unit, the system short-circuit capacity and the actual output of the unit are obtained; Based on the system short-circuit capacity and the actual output of the unit, the Operating Short-Circuit Ratio (OSCR) is calculated, and the OSCR is used as the first type of switching indicator.
[0010] As a further improvement to this application, in response to the unit being a grid-connected unit, the calculation of a second type of switching index based on the system operating parameters includes: In response to the fact that the unit is a grid-type unit, the grid impedance parameters are obtained; Based on the grid impedance parameters, the short-circuit ratio (SCR) is calculated, and the SCR is used as the second type of switching index.
[0011] As a further improvement to this application, the step of comparing the first type of switching indicator or the second type of switching indicator with the corresponding hysteresis switching threshold to determine whether to trigger a control mode switch includes: Set a first hysteresis upper limit threshold and a first hysteresis lower limit threshold for the grid-connected unit; A second hysteresis upper limit threshold and a second hysteresis lower limit threshold are set for the grid-type generator unit; When the unit is a grid-connected unit, the operating short-circuit ratio (OSCR) is compared with the first hysteresis upper limit threshold and the first hysteresis lower limit threshold. When the unit is a grid-type unit, the short-circuit ratio (SCR) is compared with the second hysteresis upper limit threshold and the second hysteresis lower limit threshold.
[0012] As a further improvement to this application, the step of switching to a network-following control mode or a network-building control mode based on the comparison results includes: When the unit is a grid-connected unit and the Operating Short-Circuit Ratio (OSCR) is greater than the first hysteresis upper limit threshold, the unit is controlled to switch to or remain in the grid-connected control mode. When the unit is a grid-connected unit and the operating short-circuit ratio (OSCR) is less than the first hysteresis lower limit threshold, the unit is controlled to switch to the grid-connected control mode. When the unit is a grid-connected unit and the short-circuit ratio (SCR) is greater than the second hysteresis upper limit threshold, the unit is controlled to switch to the grid-connected control mode. When the unit is a grid-type unit and the short-circuit ratio (SCR) is less than the second hysteresis lower limit threshold, the unit is controlled to switch to or remain in the grid-type control mode.
[0013] As a further improvement to this application, the process of switching to the network-following control mode or the network-building control mode further includes: Trigger an integral reset operation to suppress the impact caused by the instantaneous switching of control modes.
[0014] As a further improvement to this application, the triggering of the points reset operation includes: At the instant the mode switching trigger signal is detected, all control reference values remain unchanged.
[0015] As a further improvement to this application, the actual output of the unit is the active power P currently output by the unit.
[0016] As a further improvement to this application, the power grid impedance parameters include the power grid equivalent inductance and equivalent resistance.
[0017] As a further improvement to this application, the upper limit threshold of the hysteresis loop is 20, and the lower limit threshold of the hysteresis loop is 2.5.
[0018] Secondly, this application provides a hysteresis switching system for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio, comprising: The acquisition module is used to acquire the system operating parameters of the generator units in the grid-connected system; The identification module is used to identify whether the control type of the unit is a grid-connected unit or a grid-connected unit; The first response module is used to respond to the fact that the unit is a grid-connected unit and calculate the first type of switching index according to the system operating parameters, wherein the first type of switching index represents the comprehensive information of the unit's actual output and the grid strength. The second response module is used to respond to the fact that the unit is a grid-connected unit and calculate a second type of switching index based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; The trigger control module is used to compare the calculated first type of switching index or second type of switching index with the corresponding type of hysteresis switching threshold based on the type of the unit, so as to determine whether to trigger the control mode switching. The result switching module is used to control the unit to switch to either the grid-following control mode or the grid-building control mode based on the comparison results.
[0019] Thirdly, this application provides a controller configured to execute the aforementioned hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio.
[0020] Fourthly, this application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the program to implement the aforementioned hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio.
[0021] Fifthly, this application provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, it implements the aforementioned hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio.
[0022] Compared with existing methods, the advantages of this application are as follows: Different switching indices are adopted for different types of converter units. For grid-connected units, an OSCR adaptable to power fluctuations is used as the criterion, while for grid-connected units, an SCR is used as the criterion. This balances operating condition adaptability with the active support capability of grid-connected units, fully leveraging the complementary advantages of the two control modes and solving the problem of insufficient adaptability in traditional unified switching strategies. The introduction of an integral resetter during mode switching effectively reduces the inrush current during switching, avoids electrical shocks during switching, and improves the smoothness of the mode switching process. Through differentiated threshold design, this application effectively widens the hysteresis switching loop width range, improves the stable operating range of the system, avoids system oscillation problems under different operating conditions, and ensures the stable operation of the grid-connected system under all operating conditions. Attached Figure Description
[0023] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this application in any way. Furthermore, the shapes and scales of the components in the drawings are merely illustrative to aid in understanding this application and do not specifically limit the shapes and scales of the components. In the drawings: Figure 1 This is a schematic diagram of a control switching strategy based on the short-circuit ratio (SCR). Figure 2 This is a schematic diagram of a control switching strategy based on the Operating Short-Circuit Ratio (OSCR). Figure 3 The waveform diagram of the grid switching current before and after adding the integral resetter; Figure 4 Impedance curves of grid-connected units under different operating conditions; Figure 5 Impedance curves of grid-type generator units under different operating conditions; Figure 6 The graph shows the grid impedance versus grid-connected unit impedance curves when the OSCR is changed from 3 to 2.5. Figure 7 The output current and frequency waveforms are shown when the OSCR value is changed from 3 to 2.5. Figure 8 The output current analysis diagram is shown when the OSCR is 2.5. Figure 9 The graph shows the grid impedance versus grid-connected unit impedance curves when the OSCR is changed from 15 to 25. Figure 10 The output current waveform when the OSCR is changed from 15 to 25; Figure 11 Output current analysis diagram when OSCR is 25; Figure 12 The diagram shows the verification of the hysteresis switching control strategy based on SCR and OSCR. Detailed Implementation
[0024] To make the objectives and technical solutions of this application clearer and easier to understand, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.
[0025] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more. In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0026] The purpose of this application is to provide a hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio, and to adopt appropriate switching indicators for different types of converter units in order to achieve stable system operation under all operating conditions.
[0027] The technical solutions adopted in this application include: Obtain the system operating parameters of the generating units in the grid-connected system; The control type of the unit is identified as either a grid-connected unit or a grid-connected unit. In response to the fact that the generating unit is a grid-connected generating unit, a first type of switching index is calculated based on the system operating parameters, wherein the first type of switching index characterizes the comprehensive information of the actual output of the generating unit and the grid strength; In response to the fact that the unit is a grid-connected unit, a second type of switching index is calculated based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; Based on the type of the unit, the calculated first-type or second-type switching index is compared with the corresponding hysteresis switching threshold to determine whether to trigger a control mode switch. Based on the comparison results, the control unit is switched to either a grid-following control mode or a grid-connected control mode.
[0028] The target scenario of this method is a new energy grid-connected system that includes two types of converters: grid-connected and grid-connected. Different switching indicators are adopted for grid-connected and grid-connected units respectively. The operating short-circuit ratio (OSCR) is used as the switching criterion for grid-connected units, while the short-circuit ratio (SCR) is used as the switching criterion for grid-connected units. At the same time, an integral resetter is introduced during the mode switching process to reduce the inrush current at the moment of switching, which significantly improves the system's operating condition adaptability and switching smoothness, and effectively widens the stable operating range of the system.
[0029] Based on the aforementioned differentiated hysteresis switching strategy, the specific implementation steps are as follows: The first step is to obtain the system operating parameters and calculate the corresponding switching indicators.
[0030] For converter units in grid-connected systems, the control type of the unit is distinguished. For grid-connected units, the system short-circuit capacity and the actual output of the unit are collected to calculate the operating short-circuit ratio (OSCR). For grid-connected units, the grid impedance parameters are collected to calculate the short-circuit ratio (SCR).
[0031] For grid-connected generating units, the system short-circuit capacity and actual unit output are collected to calculate the Operating Short-Circuit Ratio (OSCR). The calculation formula is as follows:
[0032] in For system short-circuit capacity, P This indicator reflects the actual output of the generating unit and can simultaneously reflect changes in grid impedance and generating unit output. For grid-connected generating units, grid impedance parameters are collected, and the short-circuit ratio (SCR) is calculated.
[0033] The second step is to match the corresponding hysteresis switching threshold according to the unit type to complete the adaptive switching of the control mode.
[0034] For grid-connected units, a hysteresis switching threshold is set: when OSCR is greater than 20, the control unit operates in grid-connected mode; when OSCR is less than 2.5, the control unit switches to grid-connected mode.
[0035] For grid-connected units, a hysteresis switching threshold is set: when the SCR is greater than 20, the unit is controlled to operate in grid-connected mode; when the SCR is less than 2.5, the unit is controlled to switch to grid-connected mode.
[0036] The third step is to maintain the control reference value unchanged through the integral resetter at the moment of mode switching, thereby suppressing the switching shock.
[0037] During the switching of control modes between the two types of units, an integral reset operation is triggered to keep the control reference values unchanged at the moment of switching, reduce the inrush current during the switching process, and ensure the smoothness of the switching process.
[0038] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0039] This application discloses a hysteresis switching strategy based on short-circuit ratio / operating short-circuit ratio. For new energy grid-connected systems that include both grid-connected and grid-connected converters, the strategy utilizes the complementary small-signal stability characteristics of the two control modes to achieve stable system operation under all operating conditions through differentiated switching strategies.
[0040] Traditional hysteresis switching control strategies, such as Figure 1 As shown, this strategy only uses the short-circuit ratio (SCR) as a unified switching criterion, which can only adapt to scenarios with changes in grid impedance and cannot cope with the more common unit power fluctuation conditions in actual operation, making it difficult to guarantee system stability under all operating conditions. To address this issue, this application proposes a switching index based on the operating short-circuit ratio (OSCR), defined as follows:
[0041] in, For system short-circuit capacity, P This indicator reflects the actual output of the generating unit and can simultaneously reflect changes in grid impedance and generating unit output, thus better adapting to fluctuations in operating conditions during actual operation. The corresponding control block diagram is shown below. Figure 2 As shown.
[0042] Impedance identification is a crucial prerequisite for adaptive control in grid-connected system stability assessment. Existing research has developed mature impedance identification techniques, including passive and active detection methods. Passive detection methods utilize the system's inherent voltage and current information to solve for impedance, requiring no additional disturbances but necessitating the suppression of background harmonics. Active detection methods achieve rapid measurement by injecting harmonic signals, but this can negatively impact power quality. Since these techniques are relatively mature, this application will not delve into the specific implementation of impedance identification; detailed analyses can be found in existing literature.
[0043] In traditional mode switching between grid-following and grid-connecting systems, a large inrush current can easily be generated during the switching instant, affecting the stable operation of the system. To address this issue, this application incorporates an integral resetter in the switching stage, ensuring that all control reference values remain unchanged during the switching instant, effectively reducing the inrush current. The switching waveforms before and after incorporating the integral resetter are shown below. Figure 3 As shown, the current surge during the switching process is significantly suppressed after the integration resetter is added.
[0044] To determine the adaptability switching indicators for different types of generating units, this application analyzes the operating condition adaptability of the two types of units. The switching control strategy based on the short-circuit ratio, when power variation is not considered, has similar characteristics to the strategy based on the operating short-circuit ratio. Its oscillation behavior and analysis process will not be elaborated here. The analysis mainly focuses on the dual-mode switching based on the operating short-circuit ratio, obtaining the impedance curves of grid-connected and grid-connected units under different operating conditions, as shown below. Figure 4 , Figure 5 As shown, it is not difficult to see that the impedance of the grid-connected unit changes more significantly with operating conditions, while the impedance of the network-connected unit changes less significantly with operating conditions.
[0045] For grid-connected generating units, their impedance expressions are shown in equations (1) and (2). When the OSCR changes from 3 to 2.5, the grid impedance and grid-connected generating unit impedance curves are as follows: Figure 6 As shown in the figure, analysis reveals that the system oscillates when the OSCR is 2.5. Simulations were performed, and the OSCR was changed from 3 to 2.5 at 1.0s; the output waveform is as follows. Figure 7 As shown, the system clearly oscillates. An FFT analysis of this system is as follows: Figure 8 As shown, the dominant oscillation frequencies of the system are 20 and 80 Hz, which are close to the oscillation frequencies obtained from impedance analysis. This indicates that the stability of grid-connected units is significantly affected by OSCR changes caused by power fluctuations. Therefore, for grid-connected units, using OSCR as a switching indicator can better adapt to operating condition fluctuations.
[0046] (1) (2) In the formula,
[0047] In the formula, L f 、C f 、R lf 、R cf These are the filter inductor, capacitor, inductor parasitic resistance, and capacitor parasitic resistance. f 1 represents the fundamental frequency. V 1 represents the voltage amplitude. H PLL (s)= ( k p_pll + k i_pll / s ) / s , k p_pll and k i_pll These are the proportional gain and integral gain of the phase-locked loop, respectively. Gi ( s () is a current loop PI controller. G i ( s )= k p_c + k i_c / s , k p_c and k i_c These are the proportional coefficient and integral coefficient of the current loop, respectively. K d is the decoupling coefficient. I dref , I dref for dq Shaft current reference value.
[0048] For grid-connected generating units, their impedance expressions are shown in equations (3) and (4). When the OSCR changes from 15 to 25, the grid impedance and grid-connected generating unit impedance curves are as follows: Figure 9 As shown in the figure, analysis reveals that the system oscillates when the OSCR is 15. Simulations were performed, and the OSCR was changed from 15 to 25 at 1.0s; the output waveform is as follows. Figure 10 As shown, the system clearly oscillates. An FFT analysis of this system is as follows: Figure 11 As shown, the system oscillation frequencies are 42 and 58 Hz, which are close to the oscillation frequencies obtained from impedance analysis. However, it is worth noting that since the impedance of the grid-connected unit changes little with operating conditions, and if OSCR is used for switching, the active support capability of the grid-connected unit will be affected to some extent, failing to highlight the advantages of grid control. Therefore, for grid-connected units, using SCR as the switching indicator is more appropriate. Furthermore, the small-signal stability of the grid-connected unit under different operating conditions can be maintained by adjusting the inductance value of the virtual inductor.
[0049] (3) (4) In the formula, G f ( s )= ω f / ( s + ω f It is used for low-pass filtering of power. ω f For filtering frequency, M ( s )=1 / s ( J GFM s+ D GFM ), D ( s )= D q / Ks , E ( s )=1 / / Ks , G v ( s () is a voltage loop PI controller. G v ( s )= k p_v + k i_v / s . J GFM , D GFM , D q , K These are the inertia coefficient, damping coefficient, droop coefficient, and excitation coefficient, respectively.
[0050] Based on the above analysis, this application adopts differentiated hysteresis switching strategies for the two types of units. In addition, combined with the optimization results of a single unit, the hysteresis loop width range is widened: for the grid-following type using the OSCR-based hysteresis switching control strategy, the system switches to grid-following type when OSCR is greater than 20 and to network-building type when OSCR is less than 2.5; for the network-building type using the SCR-based hysteresis switching control strategy, the system switches to grid-following type when SCR is greater than 20 and to network-building type when SCR is less than 2.5.
[0051] To verify the effectiveness of the strategy proposed in this application, simulation verification was performed on the hysteresis switching control strategy based on SCR and OSCR. The results are as follows: Figure 12 As shown in the diagram, the unit initially operates in grid-following control mode. At 0.8s, the output power is increased to an OSCR of 2.5, causing system oscillation. This triggers a switchover, changing the grid-following unit to a grid-connecting control strategy. The system quickly stabilizes and the oscillation stops. Subsequently, at 2.0s, the SCR is set to 30. Again, system oscillation occurs, triggering a switchover that changes the grid-connecting unit back to grid-following control, and the system stabilizes again. Simulation results demonstrate that the differentiated hysteresis switching strategy proposed in this application can effectively adapt to different operating conditions and ensure stable system operation.
[0052] The hysteresis switching strategy for grid-connected units based on short-circuit ratio and operating short-circuit ratio provided in this application targets new energy grid-connected systems that include both grid-connected and grid-connected converters. Different switching indices are adopted for different types of units: the operating short-circuit ratio (OSCR) adaptable to power fluctuations is used as the switching criterion for grid-connected units, while the short-circuit ratio (SCR) is used as the switching criterion for grid-connected units. Simultaneously, an integral resetter is introduced during mode switching to reduce switching impact. This application is adaptable to all operating conditions involving power fluctuations and grid impedance changes, effectively expanding the system's stable operating range and solving the problem of insufficient adaptability of traditional unified switching strategies. The problem of large switching impact has been addressed, thus improving the operational stability of the grid-connected system.
[0053] Secondly, this embodiment provides a hysteresis switching system for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio, including: The acquisition module is used to acquire the system operating parameters of the generator units in the grid-connected system; The identification module is used to identify whether the control type of the unit is a grid-connected unit or a grid-connected unit; The first response module is used to respond to the fact that the unit is a grid-connected unit and calculate the first type of switching index according to the system operating parameters, wherein the first type of switching index represents the comprehensive information of the unit's actual output and the grid strength. The second response module is used to respond to the fact that the unit is a grid-connected unit and calculate a second type of switching index based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; The trigger control module is used to compare the calculated first type of switching index or second type of switching index with the corresponding type of hysteresis switching threshold based on the type of the unit, so as to determine whether to trigger the control mode switching. The result switching module is used to control the unit to switch to either the grid-following control mode or the grid-building control mode based on the comparison results.
[0054] Thirdly, this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the aforementioned hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio. It also includes a communication interface and a bus.
[0055] Fourthly, this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio.
[0056] Fifthly, this application provides a computer program product, which includes computer instructions that instruct a computer to execute the above-mentioned hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio.
[0057] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0058] These computer program instructions can also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0059] This application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, readable storage media, optical storage, etc.) containing computer-usable program code.
[0060] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0061] The above are merely preferred embodiments of this application and do not constitute any limitation on this application. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of this application shall still fall within the protection scope of the technical solution of this application.
[0062] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above embodiments, those skilled in the art can still modify or make equivalent substitutions to the specific implementation schemes of this application. Such modifications or equivalent substitutions do not depart from the spirit and scope of this application and are all within the protection scope of the claims of this application.
[0063] The above content provides a further detailed description of this application and should not be construed as limiting the specific implementation methods of this application to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this application, and all such deductions or substitutions should be considered as falling within the scope of protection defined by the submitted claims.
Claims
1. A hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio, characterized in that, include: Obtain the system operating parameters of the generating units in the grid-connected system; The control type of the unit is identified as either a grid-connected unit or a grid-connected unit. In response to the fact that the generating unit is a grid-connected generating unit, a first type of switching index is calculated based on the system operating parameters, wherein the first type of switching index characterizes the comprehensive information of the actual output of the generating unit and the grid strength; In response to the fact that the unit is a grid-connected unit, a second type of switching index is calculated based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; Based on the type of the unit, the calculated first-type or second-type switching index is compared with the corresponding hysteresis switching threshold to determine whether to trigger a control mode switch. Based on the comparison results, the control unit is switched to either a grid-connected control mode or a grid-connected control mode.
2. The hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio according to claim 1, characterized in that, The identification of the control type of the unit as either a grid-connected unit or a network-building unit includes: Based on the equipment identification or preset control parameters of the unit, the units are classified into grid-connected units and grid-connected units.
3. The hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio according to claim 2, characterized in that, In response to the unit being a grid-connected unit, the first type of switching index is calculated based on the system operating parameters, including: In response to the fact that the unit is a grid-connected unit, the system short-circuit capacity and the actual output of the unit are obtained; Based on the system short-circuit capacity and the actual output of the unit, the Operating Short-Circuit Ratio (OSCR) is calculated, and the OSCR is used as the first type of switching indicator.
4. The hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio according to claim 2, characterized in that, In response to the unit being a network-type unit, the second type of switching index is calculated based on the system operating parameters, including: In response to the fact that the unit is a grid-type unit, the grid impedance parameters are obtained; Based on the grid impedance parameters, the short-circuit ratio (SCR) is calculated, and the SCR is used as the second type of switching index.
5. The hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio according to claim 3, characterized in that, The step of comparing the first type of switching indicator or the second type of switching indicator with the corresponding hysteresis switching threshold to determine whether to trigger a control mode switch includes: Set a first hysteresis upper limit threshold and a first hysteresis lower limit threshold for the grid-connected unit; A second hysteresis upper limit threshold and a second hysteresis lower limit threshold are set for the grid-type generator unit; When the unit is a grid-connected unit, the operating short-circuit ratio (OSCR) is compared with the first hysteresis upper limit threshold and the first hysteresis lower limit threshold. When the unit is a grid-type unit, the short-circuit ratio (SCR) is compared with the second hysteresis upper limit threshold and the second hysteresis lower limit threshold.
6. The hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio according to claim 4, characterized in that, The step of switching between network-following control mode and network-building control mode based on the comparison results includes: When the unit is a grid-connected unit and the Operating Short-Circuit Ratio (OSCR) is greater than the first hysteresis upper limit threshold, the unit is controlled to switch to or remain in the grid-connected control mode. When the unit is a grid-connected unit and the operating short-circuit ratio (OSCR) is less than the first hysteresis lower limit threshold, the unit is controlled to switch to the grid-connected control mode. When the unit is a grid-connected unit and the short-circuit ratio (SCR) is greater than the second hysteresis upper limit threshold, the unit is controlled to switch to the grid-connected control mode. When the unit is a grid-type unit and the short-circuit ratio (SCR) is less than the second hysteresis lower limit threshold, the unit is controlled to switch to or remain in the grid-type control mode.
7. The hysteresis switching method for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio according to any one of claims 1 to 6, characterized in that, The process of switching to either the network-following control mode or the network-building control mode also includes: Trigger an integral reset operation to suppress the impact caused by the instantaneous switching of control modes.
8. The hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio according to claim 7, characterized in that, The triggering of the points reset operation includes: At the instant the mode switching trigger signal is detected, all control reference values remain unchanged.
9. The hysteresis switching method for new energy grid-connected units based on short-circuit ratio and operating short-circuit ratio according to claim 3, characterized in that, The actual output of the unit is the active power P currently output by the unit; the grid impedance parameters include the grid equivalent inductance and equivalent resistance.
10. A hysteresis switching system for new energy grid-connected generating units based on short-circuit ratio and operating short-circuit ratio, characterized in that, include: The acquisition module is used to acquire the system operating parameters of the generator units in the grid-connected system; The identification module is used to identify whether the control type of the unit is a grid-connected unit or a grid-connected unit; The first response module is used to respond to the fact that the unit is a grid-connected unit and calculate the first type of switching index according to the system operating parameters, wherein the first type of switching index represents the comprehensive information of the unit's actual output and the grid strength. The second response module is used to respond to the fact that the unit is a grid-connected unit and calculate a second type of switching index based on the system operating parameters, wherein the second type of switching index characterizes grid strength information; The trigger control module is used to compare the calculated first type of switching index or second type of switching index with the corresponding type of hysteresis switching threshold based on the type of the unit, so as to determine whether to trigger the control mode switching. The result switching module is used to control the unit to switch to either the grid-following control mode or the grid-building control mode based on the comparison results.