A continuous inverse time-limited current limiting method and device for network-forming type converters
Patent Information
- Application Number
- CN202610963077.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-30
- Publication Date
- 2026-10-16
AI Technical Summary
电网发生电压跌落、电压骤升及短路故障时，变流器将产生数倍额定故障电流，极易造成IGBT芯片损耗激增、结温快速抬升，引发热击穿和设备永久损坏
本发明提供了一种构网型变流器连续反时限限流方法及装置，包括：基于构网型变流器的IGBT瞬时通态损耗在线估算IGBT实时热安全裕度；引入结温修正系数对所述IGBT实时热安全裕度进行修正，并基于修正后的IGBT实时热安全裕度确定IGBT动态安全限流电流；基于所述IGBT动态安全限流电流调节送入IGBT调制的内电势幅值指令和功角指令。本发明提供的技术方案，可在严格约束IGBT结温处于安全范围的前提下，充分挖掘短时过流能力，提升电网故障暂态电压支撑水平，适用于构网型储能及新能源并网变流器故障穿越控制场景，具体的：
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Figure CN122932387A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronic converter technology, specifically to a continuous inverse-time current limiting method and device for grid-type converters. Background Technology The new power system exhibits characteristics of high proportion of new energy sources, low inertia, and weak short-circuit ratio. Grid-type converters can simulate the characteristics of synchronous machine voltage sources and are core equipment supporting the transient stability of the power grid and providing fault voltage support. When the power grid experiences voltage dips, voltage surges, or short-circuit faults, the converter will generate several times its rated fault current, which can easily cause a surge in IGBT chip losses and a rapid rise in junction temperature, leading to thermal breakdown and permanent equipment damage.
[0002] Existing fault current limiting methods mainly employ fixed virtual impedance current limiting and constant current hard limiting, which have obvious drawbacks: 1) Current current limiting methods do not incorporate real-time sensing of device junction temperature and rely solely on fixed timing thresholds, which cannot adapt to changes in ambient temperature, initial load, and heat dissipation conditions. They can only conservatively leave margins, wasting the short-term overload potential of devices; 2) Conventional control relies on a voltage-current dual-loop structure, which has strong parameter coupling and complex tuning; 3) Single current limiting without phase coordination makes it difficult to simultaneously achieve the dual goals of device thermal safety and grid reactive voltage support.
[0003] Therefore, there is an urgent need for a current limiting method that integrates junction temperature observation, continuous inverse time-limited modeling, and amplitude-phase coordinated adjustment to address issues such as fitting error, oscillation control, conservative current limiting, and insufficient support capacity from a mechanistic perspective. Summary of the Invention
[0004] To overcome the above-mentioned defects, this invention proposes a continuous inverse-time current limiting method and device for grid-type converters.
[0005] Firstly, a continuous inverse-time current limiting method for a grid-type converter is provided, the method comprising: Online estimation of IGBT real-time thermal safety margin based on IGBT instantaneous on-state loss of grid-type converter; A junction temperature correction factor is introduced to correct the real-time thermal safety margin of the IGBT, and the dynamic safety current limiting current of the IGBT is determined based on the corrected real-time thermal safety margin of the IGBT. The internal potential amplitude command and power angle command are sent to the IGBT based on the IGBT dynamic safety current limiting current adjustment.
[0006] Preferably, the instantaneous on-state loss of the IGBT is as follows:
[0007] In the above formula, P loss For the instantaneous conduction loss of the IGBT,i c This is the collector instantaneous current. u ce This is the collector-emitter conduction voltage drop.
[0008] Preferably, the real-time thermal safety margin of the IGBT is as follows:
[0009] In the above formula, For IGBT real-time thermal safety margin, This is the maximum allowable junction temperature of the IGBT. For the first k Estimated junction temperature of IGBT at any time.
[0010] Furthermore, the first k The estimated junction temperature of the IGBT at that time is as follows:
[0011] In the above formula, For the first k-1 IGBT junction temperature estimation at any time t To control the sampling step size, For the junction-shell heat capacity, For the first k-1 Instantaneous conduction loss of IGBT at any given moment. For junction-shell thermal resistance, This refers to the device case temperature.
[0012] Furthermore, the corrected IGBT real-time thermal safety margin is as follows:
[0013] In the above formula, For the corrected real-time thermal safety margin of IGBTs, This is the margin adjustment ratio coefficient.
[0014] Furthermore, the dynamic safety current limiting current of the IGBT is as follows:
[0015] In the above formula, For IGBT dynamic safety current limiting current, t Fault duration / Overload duration C This is the inverse time-delay tuning constant corresponding to the thermal time constant of the device. n It is an inverse time-limited characteristic index. I N This is the rated output current of the converter.
[0016] Furthermore, the inverse time-delay tuning constant corresponding to the thermal time constant of the device is as follows: .
[0017] Furthermore, the internal potential amplitude command sent to the IGBT modulation based on the IGBT dynamic safety current limiting current adjustment includes: After replacing the current magnitude in the equivalent impedance phasor relationship of the grid converter with the dynamic safety current limiting current of the IGBT, the equivalent impedance phasor relationship of the grid converter is solved to obtain the internal potential magnitude. Square the magnitude of the internal potential and then take the square root to obtain the maximum allowable internal potential amplitude considering overload constraints. Based on the maximum permissible internal potential amplitude considering overload constraints, determine the maximum internal potential amplitude that will not trigger device overcurrent under the current operating condition; The maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is used as the internal potential amplitude command sent to the IGBT for modulation.
[0018] Furthermore, the equivalent impedance phasor relationship of the grid converter is as follows: E=U+jX*I In the above formula, E is the magnitude of the internal potential, U is the magnitude of the voltage, j is the imaginary part in unit, X is the magnitude of the impedance, and I is the magnitude of the current.
[0019] Furthermore, the maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is as follows:
[0020] In the above formula, This represents the maximum internal potential amplitude that will not trigger overcurrent in the device under the current operating conditions. This represents the reference internal potential amplitude output by the power outer loop droop strategy. The maximum permissible internal potential amplitude considering overload constraints.
[0021] Furthermore, the power angle command sent to the IGBT modulation is as follows:
[0022] In the above formula, δ The deviation between the dynamic safety current limiting current and the rated current of the IGBT. To send the power angle command for IGBT modulation, This is the reference power angle output by the power outer loop droop strategy.
[0023] Secondly, a continuous inverse-time current limiting device for a grid-type converter is provided, the continuous inverse-time current limiting device for the grid-type converter comprising: The first analysis module is used for online estimation of the real-time thermal safety margin of IGBTs based on the instantaneous on-state losses of IGBTs in grid-type converters. The second analysis module is used to introduce a junction temperature correction coefficient to correct the real-time thermal safety margin of the IGBT, and to determine the dynamic safety current limiting current of the IGBT based on the corrected real-time thermal safety margin of the IGBT. The adjustment module is used to adjust the internal potential amplitude command and power angle command sent to the IGBT based on the IGBT dynamic safety current limiting current.
[0024] Thirdly, a computer device is provided, comprising: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the continuous inverse time current limiting method for the grid-type converter is implemented.
[0025] Fourthly, a computer-readable storage medium is provided, on which a computer program is stored, wherein when the computer program is executed, the continuous inverse-time current limiting method for the grid-type converter is implemented.
[0026] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects: This invention provides a continuous inverse-time current limiting method and apparatus for grid-connected converters, comprising: online estimation of the real-time thermal safety margin of the IGBT based on the instantaneous on-state loss of the IGBT in the grid-connected converter; correction of the real-time thermal safety margin of the IGBT by introducing a junction temperature correction coefficient, and determination of the dynamic safety current limiting current of the IGBT based on the corrected real-time thermal safety margin; and adjustment of the internal potential amplitude command and power angle command sent to the IGBT modulation based on the dynamic safety current limiting current of the IGBT. The technical solution provided by this invention can fully exploit the short-time overcurrent capability under the premise of strictly constraining the IGBT junction temperature within a safe range, and improve the support level of transient voltage during grid faults. It is applicable to fault ride-through control scenarios for grid-connected energy storage and new energy grid-connected converters. Specifically: 1) This invention adopts a continuous inverse-time overload characterization model. The mathematical model conforms to the real thermoelectric inverse-time evolution law of IGBT, and eliminates the voltage and power transient oscillations caused by segmented switching from the mechanism perspective.
[0027] 2) Sensorless online junction temperature observation is adopted, and the junction temperature is estimated only by electrical quantities and thermal network parameters, without the need for additional temperature measuring elements; the current limiting threshold adapts to the real-time thermal margin, avoiding the conservative current limiting of traditional fixed thresholds, and significantly improving the short-time overcurrent utilization of the device.
[0028] 3) Introduce amplitude-phase coordinated regulation, and achieve optimal coordination between current limiting and voltage support under a current-free inner loop architecture by constraining current and optimizing reactive power support through amplitude constraint and phase optimization. Attached Figure Description
[0029] Figure 1 This is a schematic flowchart of the main steps of the continuous inverse-time current limiting method for grid-type converters according to an embodiment of the present invention; Figure 2 This is the fault ride-through waveform in an embodiment of the present invention when no current limiting strategy is used; Figure 3 This is the fault ride-through waveform when using a virtual impedance current limiting strategy in an embodiment of the present invention; Figure 4 This is the fault ride-through waveform when the inverse time-limited current limiting strategy is adopted in an embodiment of the present invention; Figure 5 This is a schematic diagram comparing the overload safety boundaries of three current limiting strategies according to embodiments of the present invention. Detailed Implementation
[0030] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] Example 1 See appendix Figure 1 , Figure 1 This is a schematic flowchart illustrating the main steps of a continuous inverse-time current limiting method for a grid-type converter according to an embodiment of the present invention. Figure 1 As shown, the continuous inverse-time current limiting method for grid-type converters in this embodiment of the invention mainly includes the following steps: Step S101: Online estimation of IGBT real-time thermal safety margin based on IGBT instantaneous on-state losses of grid-type converter; Step S102: Introduce a junction temperature correction coefficient to correct the real-time thermal safety margin of the IGBT, and determine the dynamic safety current limiting current of the IGBT based on the corrected real-time thermal safety margin of the IGBT. Step S103: Based on the IGBT dynamic safety current limiting current adjustment, the internal potential amplitude command and power angle command are sent to the IGBT for modulation.
[0033] In this embodiment, the instantaneous conduction loss of the IGBT is as follows:
[0034] In the above formula, P loss For the instantaneous conduction loss of the IGBT, i c This is the collector instantaneous current. u ce This is the collector-emitter conduction voltage drop.
[0035] In this embodiment, the real-time thermal safety margin of the IGBT is as follows:
[0036] In the above formula, For IGBT real-time thermal safety margin, This is the maximum allowable junction temperature of the IGBT. For the first k Estimated junction temperature of IGBT at any time.
[0037] In one implementation, the first k The estimated junction temperature of the IGBT at that time is as follows:
[0038] In the above formula, For the first k-1 IGBT junction temperature estimation at any time t To control the sampling step size, For the junction-shell heat capacity, For the first k-1 Instantaneous conduction loss of IGBT at any given moment. For junction-shell thermal resistance, This refers to the device case temperature.
[0039] In one implementation, the modified IGBT real-time thermal safety margin is as follows:
[0040] In the above formula, For the corrected real-time thermal safety margin of IGBTs, This is the margin adjustment ratio coefficient.
[0041] In one implementation, the IGBT dynamic safety current limiting current is as follows:
[0042] In the above formula, For IGBT dynamic safety current limiting current, tFault duration / Overload duration C This is the inverse time-delay tuning constant corresponding to the thermal time constant of the device. n It is an inverse time-limited characteristic index. I N This is the rated output current of the converter.
[0043] In one embodiment, the inverse time-delay tuning constant corresponding to the thermal time constant of the device is as follows: .
[0044] In one embodiment, the command for adjusting the internal potential amplitude of the IGBT based on the IGBT dynamic safety current limiting current adjustment includes: After replacing the current magnitude in the equivalent impedance phasor relationship of the grid converter with the dynamic safety current limiting current of the IGBT, the equivalent impedance phasor relationship of the grid converter is solved to obtain the internal potential magnitude. Square the magnitude of the internal potential and then take the square root to obtain the maximum allowable internal potential amplitude considering overload constraints. Based on the maximum permissible internal potential amplitude considering overload constraints, determine the maximum internal potential amplitude that will not trigger device overcurrent under the current operating condition; The maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is used as the internal potential amplitude command sent to the IGBT for modulation.
[0045] In one embodiment, the equivalent impedance phasor relationship of the grid converter is as follows: E=U+jX*I In the above formula, E is the magnitude of the internal potential, U is the magnitude of the voltage, j is the imaginary part in unit, X is the magnitude of the impedance, and I is the magnitude of the current.
[0046] In one implementation, the maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is as follows:
[0047] In the above formula, This represents the maximum internal potential amplitude that will not trigger overcurrent in the device under the current operating conditions. This represents the reference internal potential amplitude output by the power outer loop droop strategy. The maximum permissible internal potential amplitude considering overload constraints.
[0048] In one embodiment, the power angle command sent to the IGBT modulation is as follows:
[0049] In the above formula, δThe deviation between the dynamic safety current limiting current and the rated current of the IGBT. To send the power angle command for IGBT modulation, This is the reference power angle output by the power outer loop droop strategy.
[0050] In one specific implementation, taking a 500kW high-voltage direct-connected energy storage system as an example, the implementation of this patent is illustrated. The system has a rated voltage of 380V, a rated capacity of 500kW, a filter inductance of 0.1mH, a filter capacitor of 80uF, and a virtual moment of inertia of 0.2kW / m. 2 Damping coefficient 500, switching frequency 8000Hz.
[0051] Figure 2 The waveform shows the fault ride-through waveform without current limiting. When a symmetrical short-circuit fault occurs in the grid, the converter output current rapidly rises to 5 times the rated current, at which point the converter enters a deep overload state. Due to the lack of active current limiting measures, this overload current lasts for 15 μs (exceeding the 10 μs threshold of the converter software overcurrent protection), triggering the hardware protection circuit. After the protection action, the converter pulse is blocked, and the output current instantly drops to 0, causing the grid connection voltage to lose support, continuously dropping from 1.0 pu (rated voltage) before the fault to below 0.2 pu. The waveform shows an undamped growth trend in the current waveform, with a peak value reaching 5.2 times the rated current; the voltage waveform shows no signs of recovery within 30 ms after the fault, ultimately leading to voltage collapse due to the converter disconnecting from the grid. This result indicates that without a current limiting strategy, the converter cannot balance its own safety and grid support under severe faults, resulting in a fault ride-through success rate of 0% and exacerbating grid transient instability.
[0052] Figure 3 The waveform shown is the fault ride-through waveform when using a virtual impedance current limiting strategy. After a fault occurs, the converter introduces a virtual impedance (equivalent impedance value of 0.5 pu) into the control loop, suppressing the peak output current to 2.5 pu and keeping the duration within 30 seconds, thus preventing overcurrent protection from being triggered. However, the limitations of this strategy are clearly reflected in the voltage waveform: because the virtual impedance consumes reactive power, the reactive current output by the converter drops to 40% of its rated support capacity, resulting in the grid connection point voltage only recovering to a maximum of 0.7 pu, failing to meet the rated voltage requirement of 1.0 pu. A waveform comparison shows that although the current waveform has no obvious overshoot, the rising edge slope is relatively slow, and the voltage waveform still exhibits a steady-state deviation of 0.3 pu. This indicates that while the virtual impedance strategy can ensure equipment safety, it comes at the cost of sacrificing voltage support capacity, failing to meet the voltage support requirements of a high proportion of renewable energy grids.
[0053] Figure 4The waveforms show the fault ride-through waveforms when using the inverse-time current limiting strategy. In the initial stage of the fault, the strategy prioritizes suppressing the current peak, rapidly limiting active power to keep the peak current below 3 p.u. In the middle stage, reactive power support is gradually released, increasing the reactive current from 1.2 p.u. to 2.8 p.u., driving the grid connection voltage from 0.3 p.u. to 0.9 p.u. In the later stage, the power command is dynamically adjusted based on the inverse-time characteristic, reducing the current to 3 p.u. as the withstand time increases, while the voltage remains stable at the rated value of 1.0 p.u. The waveforms show a steady-state current overload factor of 3 p.u. (within the safe threshold), a voltage recovery time 75% shorter than the virtual impedance strategy, and no voltage fluctuations throughout the fault ride-through process. These results verify the core advantage of the inverse-time current limiting strategy: by dynamically balancing current suppression and reactive power output, it ensures the converter operates within a safe overload range while achieving full grid connection voltage support.
[0054] Figure 5 This diagram illustrates the comparison of overload safety boundaries for three current-limiting strategies. Analysis of the diagram shows that: under the no-current-limit strategy, the fault inrush current far exceeds the device's safety tolerance boundary, failing to guarantee the power device's operational safety and also compromising the grid's transient voltage support capability; while the virtual impedance current-limiting strategy can constrain the fault current within the device's safe range and meet the equipment's thermal protection requirements, it suffers from excessive current limiting, resulting in insufficient grid voltage support during fault periods; the inverse-time current-limiting strategy proposed in this invention can precisely control the transient current within the IGBT's safe overload range, strictly ensuring device operational safety while fully releasing the converter's reactive power support potential, achieving a dual-objective synergistic optimization of equipment thermal safety and grid voltage support.
[0055] Example 2 Based on the same inventive concept, the present invention also provides a continuous inverse-time current limiting device for a grid-type converter, the continuous inverse-time current limiting device for the grid-type converter comprising: The first analysis module is used for online estimation of the real-time thermal safety margin of IGBTs based on the instantaneous on-state losses of IGBTs in grid-type converters. The second analysis module is used to introduce a junction temperature correction coefficient to correct the real-time thermal safety margin of the IGBT, and to determine the dynamic safety current limiting current of the IGBT based on the corrected real-time thermal safety margin of the IGBT. The adjustment module is used to adjust the internal potential amplitude command and power angle command sent to the IGBT based on the IGBT dynamic safety current limiting current.
[0056] Preferably, the instantaneous on-state loss of the IGBT is as follows:
[0057] In the above formula,P loss For the instantaneous conduction loss of the IGBT, i c This is the collector instantaneous current. u ce This is the collector-emitter conduction voltage drop.
[0058] Preferably, the real-time thermal safety margin of the IGBT is as follows:
[0059] In the above formula, For IGBT real-time thermal safety margin, This is the maximum allowable junction temperature of the IGBT. For the first k Estimated junction temperature of IGBT at any time.
[0060] Furthermore, the first k The estimated junction temperature of the IGBT at that time is as follows:
[0061] In the above formula, For the first k-1 IGBT junction temperature estimation at any time t To control the sampling step size, For the junction-shell heat capacity, For the first k-1 Instantaneous conduction loss of IGBT at any given moment. For junction-shell thermal resistance, This refers to the device case temperature.
[0062] Furthermore, the corrected IGBT real-time thermal safety margin is as follows:
[0063] In the above formula, For the corrected real-time thermal safety margin of IGBTs, This is the margin adjustment ratio coefficient.
[0064] Furthermore, the dynamic safety current limiting current of the IGBT is as follows:
[0065] In the above formula, For IGBT dynamic safety current limiting current, t Fault duration / Overload duration C This is the inverse time-delay tuning constant corresponding to the thermal time constant of the device. n It is an inverse time-limited characteristic index. I N This is the rated output current of the converter.
[0066] Furthermore, the inverse time-delay tuning constant corresponding to the thermal time constant of the device is as follows: .
[0067] Furthermore, the internal potential amplitude command sent to the IGBT modulation based on the IGBT dynamic safety current limiting current adjustment includes: After replacing the current magnitude in the equivalent impedance phasor relationship of the grid converter with the dynamic safety current limiting current of the IGBT, the equivalent impedance phasor relationship of the grid converter is solved to obtain the internal potential magnitude. Square the magnitude of the internal potential and then take the square root to obtain the maximum allowable internal potential amplitude considering overload constraints. Based on the maximum permissible internal potential amplitude considering overload constraints, determine the maximum internal potential amplitude that will not trigger device overcurrent under the current operating condition; The maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is used as the internal potential amplitude command sent to the IGBT for modulation.
[0068] Furthermore, the equivalent impedance phasor relationship of the grid converter is as follows: E=U+jX*I In the above formula, E is the magnitude of the internal potential, U is the magnitude of the voltage, j is the imaginary part in unit, X is the magnitude of the impedance, and I is the magnitude of the current.
[0069] Furthermore, the maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is as follows:
[0070] In the above formula, This represents the maximum internal potential amplitude that will not trigger overcurrent in the device under the current operating conditions. This represents the reference internal potential amplitude output by the power outer loop droop strategy. The maximum permissible internal potential amplitude considering overload constraints.
[0071] Furthermore, the power angle command sent to the IGBT modulation is as follows:
[0072] In the above formula, δ The deviation between the dynamic safety current limiting current and the rated current of the IGBT. To send the power angle command for IGBT modulation, This is the reference power angle output by the power outer loop droop strategy.
[0073] Example 3 Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the continuous inverse-time current limiting method for a grid-type converter in the above embodiments.
[0074] Example 4 Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the continuous inverse-time current limiting method for a grid-type converter in the above embodiments.
[0075] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0076] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. 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 illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0077] 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.
[0078] These computer program instructions may 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.
[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A continuous inverse-time current limiting method for a grid-type converter, characterized in that, The method includes: Online estimation of IGBT real-time thermal safety margin based on IGBT instantaneous on-state loss of grid-type converter; A junction temperature correction factor is introduced to correct the real-time thermal safety margin of the IGBT, and the dynamic safety current limiting current of the IGBT is determined based on the corrected real-time thermal safety margin of the IGBT. The internal potential amplitude command and power angle command are fed into the IGBT based on the IGBT dynamic safety current limiting current adjustment.
2. The method as described in claim 1, characterized in that, The instantaneous conduction loss of the IGBT is as follows: In the above formula, P loss For the instantaneous conduction loss of the IGBT, i c This is the collector instantaneous current. u ce This is the collector-emitter conduction voltage drop.
3. The method as described in claim 1, characterized in that, The real-time thermal safety margin of the IGBT is as follows: In the above formula, For IGBT real-time thermal safety margin, This is the maximum allowable junction temperature of the IGBT. For the first k Estimated junction temperature of IGBT at any time.
4. The method as described in claim 3, characterized in that, The first k The estimated junction temperature of the IGBT at that time is as follows: In the above formula, For the first k-1 IGBT junction temperature estimation at any time t To control the sampling step size, For the junction-shell heat capacity, For the first k-1 Instantaneous conduction loss of IGBT at any given moment. For junction-shell thermal resistance, This refers to the device case temperature.
5. The method as described in claim 4, characterized in that, The corrected IGBT real-time thermal safety margin is as follows: In the above formula, For the corrected real-time thermal safety margin of IGBTs, This is the margin adjustment ratio coefficient.
6. The method as described in claim 5, characterized in that, The dynamic safety current limiting current of the IGBT is as follows: In the above formula, For IGBT dynamic safety current limiting current, t Fault duration / Overload duration C This is the inverse time-delay tuning constant corresponding to the thermal time constant of the device. n It is an inverse time-limited characteristic index. I N This is the rated output current of the converter.
7. The method as described in claim 6, characterized in that, The inverse time-delay tuning constant corresponding to the thermal time constant of the device is as follows: 。 8. The method as described in claim 6, characterized in that, The internal potential amplitude command sent to the IGBT modulation based on the IGBT dynamic safety current limiting current adjustment includes: After replacing the current magnitude in the equivalent impedance phasor relationship of the grid converter with the dynamic safety current limiting current of the IGBT, the equivalent impedance phasor relationship of the grid converter is solved to obtain the internal potential magnitude. Square the magnitude of the internal potential and then take the square root to obtain the maximum allowable internal potential amplitude considering overload constraints. Based on the maximum permissible internal potential amplitude considering overload constraints, determine the maximum internal potential amplitude that will not trigger device overcurrent under the current operating condition; The maximum internal potential amplitude that does not trigger device overcurrent under the current operating condition is used as the internal potential amplitude command sent to the IGBT for modulation.
9. The method as described in claim 8, characterized in that, The equivalent impedance phasor relationship of the grid converter is as follows: E=U+jX*I In the above formula, E is the magnitude of the internal potential, U is the magnitude of the voltage, j is the imaginary part in unit, X is the magnitude of the impedance, and I is the magnitude of the current.
10. The method as described in claim 8, characterized in that, The maximum internal potential amplitude that will not trigger overcurrent in the device under the current operating conditions is as follows: In the above formula, This represents the maximum internal potential amplitude that will not trigger overcurrent in the device under the current operating conditions. This represents the reference internal potential amplitude output by the power outer loop droop strategy. The maximum permissible internal potential amplitude considering overload constraints.
11. The method as described in claim 6, characterized in that, The power angle command sent to the IGBT modulation is as follows: In the above formula, δ The deviation between the dynamic safety current limiting current and the rated current of the IGBT. To send the power angle command for IGBT modulation, This is the reference power angle output by the power outer loop droop strategy.
12. An apparatus based on the continuous inverse-time current limiting method for a grid-type converter according to any one of claims 1-11, characterized in that, The device includes: The first analysis module is used for online estimation of the real-time thermal safety margin of IGBTs based on the instantaneous on-state losses of IGBTs in grid-type converters. The second analysis module is used to introduce a junction temperature correction coefficient to correct the real-time thermal safety margin of the IGBT, and to determine the dynamic safety current limiting current of the IGBT based on the corrected real-time thermal safety margin of the IGBT. The adjustment module is used to adjust the internal potential amplitude command and power angle command sent to the IGBT based on the IGBT dynamic safety current limiting current.
13. A computer device, characterized in that, include: One or more processors; The processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the continuous inverse time current limiting method for grid-type converters as described in any one of claims 1 to 11 is implemented.
14. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the continuous inverse-time current limiting method for grid-type converters as described in any one of claims 1 to 11.