Method and device for measuring ripple current of direct-current bus capacitor of wind power converter

Abstract

The invention relates to the technical field of wind power converter monitoring, in particular to a wind power converter direct current bus capacitor ripple current measurement method, device and equipment and a computer storage medium. According to the method for measuring the ripple current of the direct current bus capacitor of the wind power converter, the ripple current in the direct current bus capacitor can be accurately predicted, which is crucial to type selection of the capacitor and system design; by means of accurate ripple current calculation, the capacitor more suitable for specific application requirements can be designed, the risk that the capacitor is damaged due to overheating or overload can be reduced, and system instability or shutdown caused by capacitor faults is reduced. The thermal stress and the electric stress of the capacitor can be reduced through accurate ripple current calculation, so that the service life of the capacitor is prolonged.

Description

Technical Field

[0001] This invention relates to the field of wind power converter monitoring technology, and in particular to a method, device, equipment, and computer storage medium for measuring the ripple current of the DC bus capacitor of a wind power converter. Background Technology

[0002] The DC bus capacitor, as a key component connecting the machine-side converter and the grid-side converter, plays a crucial role in the reliable operation of wind power converters. Ripple current not only affects the capacitor's temperature range but also significantly impacts its electrical characteristics. Therefore, accurately calculating the ripple current of the DC bus capacitor is of significant reference value for component selection. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the ripple current of the DC bus capacitor cannot be accurately calculated in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for measuring the ripple current of the DC bus capacitor in a wind power converter, comprising:

[0005] Kirchhoff's current law is used to determine the relationship between the DC bus capacitor ripple current, the machine-side converter output current, and the grid-side converter input current.

[0006] The DC and AC components between the output current of the generator-side converter and the input current of the grid-side converter are separated, and a measurement model for the DC bus capacitor ripple current is constructed based on the AC component between the output current of the generator-side converter and the input current of the grid-side converter.

[0007] Preferably, determining the relationship between the DC bus capacitor ripple current, the generator-side converter output current, and the grid-side converter input current using Kirchhoff's current law includes:

[0008] Kirchhoff's Current Law is used to determine that the DC bus capacitor ripple current value is equal to the difference between the output current value of the machine-side converter and the input current value of the grid-side converter.

[0009] Preferably, the method of separating the DC and AC components between the output current of the generator-side converter and the input current of the grid-side converter, and constructing a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the generator-side converter and the input current of the grid-side converter includes:

[0010] Based on the fact that both the output current of the machine-side converter and the input current of the grid-side converter include DC and AC components, and that the DC components of the two are equal, the DC bus capacitor ripple current is determined to be equal to the difference between the AC component value of the output current of the machine-side converter and the AC component value of the input current of the grid-side converter, and a measurement model for the DC bus capacitor ripple current is constructed.

[0011] Preferably, the method for measuring the DC bus capacitor ripple current of the wind power converter further includes:

[0012] The relationship between the effective values ​​of DC bus capacitor ripple current, machine-side converter ripple current, and grid-side converter ripple current is determined based on the vector superposition principle of AC current components.

[0013] A measurement model for the effective value of the ripple current of the machine-side converter is constructed based on the DC voltage ripple rate, capacitance value, maximum DC voltage, switching frequency of the machine-side converter, and charging and discharging time of the capacitor.

[0014] A measurement model for the effective value of the grid-side converter ripple current is constructed based on the effective value of the grid-side converter output current, the modulation ratio based on the dual PWM control strategy, and the system power factor.

[0015] By combining the measurement models of the RMS value of the ripple current of the generator-side converter and the grid-side converter, a measurement model for the ripple current of the DC link capacitor is constructed.

[0016] Preferably, the determination of the relationship between the effective value of the DC bus capacitor ripple current, the effective value of the machine-side converter ripple current, and the effective value of the grid-side converter ripple current based on the vector superposition principle of AC current components includes:

[0017] Based on the principle of vector superposition of AC current components, the square of the effective value of the DC bus capacitor ripple current is determined to be equal to the sum of the square of the effective value of the machine-side converter ripple current and the square of the effective value of the grid-side converter ripple current.

[0018] Preferably, the specific formula for the measurement model of the effective value of the ripple current of the machine-side converter is as follows:

[0019]

[0020] Where λ is the DC voltage ripple rate, C is the capacitance value, and U max It is the maximum DC voltage, f s It is the switching frequency of the machine-side converter, t c and t f These are the charging and discharging times of the capacitor, respectively.

[0021] Preferably, the specific formula for the measurement model of the effective value of the grid-side converter ripple current is as follows:

[0022]

[0023] Among them, I out,rms It is the effective value of the grid-side converter output current, and M is the modulation ratio based on the dual PWM control strategy. It is the system power factor.

[0024] The present invention also provides a device for measuring the ripple current of the DC bus capacitor of a wind power converter, comprising:

[0025] The first relationship judgment module uses Kirchhoff's current law to determine the relationship between the DC bus capacitor ripple current, the machine-side converter output current, and the grid-side converter input current.

[0026] The first measurement model construction module is used to separate the DC and AC components between the output current of the machine-side converter and the input current of the grid-side converter, and to construct a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the machine-side converter and the input current of the grid-side converter.

[0027] This invention also provides a device for measuring the ripple current of the DC bus capacitor in a wind power converter, comprising:

[0028] Memory, used to store computer programs;

[0029] A processor is used to execute the computer program to implement the steps of the above-described method for measuring the ripple current of a DC bus capacitor in a wind power converter.

[0030] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described method for measuring the ripple current of a DC bus capacitor in a wind power converter.

[0031] The technical solution of the present invention has the following advantages compared with the prior art:

[0032] The ripple current measurement method for DC bus capacitors in wind power converters described in this invention can accurately predict the ripple current in DC bus capacitors, which is crucial for capacitor selection and system design. Through accurate ripple current calculation, capacitors more suitable for specific application requirements can be designed, helping to reduce the risk of capacitor damage due to overheating or overload, and reducing system instability or downtime caused by capacitor failure. Accurate ripple current calculation can reduce the thermal and electrical stress of capacitors, thereby extending their service life. Attached Figure Description

[0033] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0034] Figure 1 This is a schematic diagram of the structure of a wind power converter;

[0035] Figure 2This is a flowchart illustrating the implementation of a method for measuring the ripple current of a DC bus capacitor in a wind power converter, as provided by this invention. Detailed Implementation

[0036] The core of this invention is to provide a method, device, equipment, and computer storage medium for measuring the ripple current of the DC bus capacitor in a wind power converter, which effectively improves the accuracy of ripple current measurement in the DC bus capacitor.

[0037] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and 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.

[0038] Please refer to Figure 1 The wind power converter includes a machine-side converter (101), a DC bus capacitor (102), a grid-side converter (103), and i1, i2, i... c These are the output current of the generator-side converter, the input current of the grid-side converter, and the ripple current of the DC bus capacitor, respectively.

[0039] Based on the power loss model of a capacitor, the ripple voltage (U), ripple frequency (f), dielectric loss tangent (tanδ), and ripple current (I) are... c The relationship between the two can be determined by the following formula:

[0040] P loss =U 2 ·2πfC·tanδ=(U·2πfC) 2 ·ESR=I C ESR

[0041] in:

[0042] P loss This refers to the power loss of the capacitor.

[0043] U represents the ripple voltage, which refers to the periodic fluctuations in the voltage across a capacitor. In wind power converters, this is typically caused by the switching action of the converter. The magnitude of the ripple voltage directly affects the capacitor's power loss and thermal stress.

[0044] I c Ripple current is the fluctuation in current flowing through a capacitor. It is the alternating current component that passes through the capacitor, and its magnitude directly affects the capacitor's thermal load and lifespan. Accurate calculation of ripple current is crucial for ensuring reliable operation of the capacitor within its expected lifespan.

[0045] f is the ripple frequency, which is related to the switching frequency of the converter and is usually relatively high. High-frequency ripple can increase the dielectric loss of the capacitor, affecting its long-term reliability.

[0046] tanδ is the dielectric loss tangent, which characterizes the loss properties of the capacitor dielectric material; it is a material property that describes the loss of the capacitor dielectric material under AC voltage. A lower tanσ value generally means lower power loss and better thermal stability.

[0047] This formula illustrates that the power loss of a capacitor is determined by the ripple voltage, ripple current, ripple frequency, and the dielectric loss tangent. In wind power converters, ripple current has a significant impact on capacitor lifespan and thermal management; therefore, accurate calculation of ripple current is crucial for capacitor selection and system design.

[0048] Please refer to Figure 2 , Figure 2 The flowchart illustrates the implementation of a method for measuring the ripple current of a DC bus capacitor in a wind power converter, as provided by this invention. The specific operation steps are as follows:

[0049] S101: Use Kirchhoff's current law to determine the relationship between DC bus capacitor ripple current, machine-side converter output current and grid-side converter input current.

[0050] S102: Separate the DC and AC components between the output current of the generator-side converter and the input current of the grid-side converter, and construct a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the generator-side converter and the input current of the grid-side converter.

[0051] Based on the above embodiments, the method for measuring the DC bus capacitor ripple current of the wind power converter further includes:

[0052] S103: Determine the relationship between the effective values ​​of DC bus capacitor ripple current, machine-side converter ripple current, and grid-side converter ripple current based on the vector superposition principle of AC current components.

[0053] S104: A measurement model for the effective value of the ripple current of the machine-side converter is constructed based on the DC voltage ripple rate, capacitance value, maximum DC voltage, switching frequency of the machine-side converter, and charging and discharging time of the capacitor.

[0054] S105: A measurement model for the effective value of the grid-side converter ripple current is constructed based on the effective value of the grid-side converter output current, the modulation ratio based on the dual PWM control strategy, and the system power factor.

[0055] S106: Combining the measurement models of the effective values ​​of the ripple current of the generator-side converter and the grid-side converter, a measurement model for the ripple current of the DC link capacitor is constructed.

[0056] Based on the above embodiments, this embodiment will provide a detailed description of step S101:

[0057] Kirchhoff's Current Law (KCL): This law states that the sum of the currents entering a node is equal to the sum of the currents leaving that node. In the DC bus capacitor of a wind power converter, the ripple current i... c The difference between the output current i1 of the generator-side converter and the input current i2 of the grid-side converter can be used to calculate:

[0058] i c =i1-i2

[0059] Here, i c i1 is the DC bus capacitor ripple current, i2 is the machine-side converter output current, and i3 is the grid-side converter input current.

[0060] Based on the above embodiments, this embodiment will provide a detailed description of step S102:

[0061] Both i1 and i2 contain DC and AC components. The DC component does not pass through the capacitor, while the AC component (i.e., ripple current) does, affecting its thermal management and lifespan.

[0062]

[0063] DC component: This is the average value of the current, which does not cause the capacitor to charge or discharge, and therefore does not contribute to the ripple current.

[0064] Alternating current component: This is the fluctuating part of the current, directly related to the ripple current of the capacitor. The alternating current component can be separated from the total current using Fourier analysis or other signal processing techniques.

[0065] Among them, i dc1 and i dc2 It is the DC component, i ac1 and i ac2 It is the AC component. Since the DC component does not pass through the capacitor, we can conclude that: i c =i ac1 -i ac2

[0066] Based on the fact that both the output current of the machine-side converter and the input current of the grid-side converter include DC and AC components, and that the DC components of the two are equal, the DC bus capacitor ripple current is determined to be equal to the difference between the AC component value of the output current of the machine-side converter and the AC component value of the input current of the grid-side converter, and a measurement model for the DC bus capacitor ripple current is constructed.

[0067] Based on the above embodiments, this embodiment will provide a detailed description of step S103:

[0068] In an AC circuit, if there are two or more current components, their vector sum can be calculated using the Pythagorean theorem. Specifically, if there are two orthogonal (mutually perpendicular) AC current components, their effective sum (RMS) can be calculated as follows:

[0069]

[0070] Squaring both sides, we get:

[0071] I 2 C,rms =I 2 ac,rms +I 2 ac2,rms

[0072] This formula assumes that the two AC components are orthogonal, meaning there is no phase difference between them. In wind power converters, the ripple currents generated by the machine-side converter and the grid-side converter may not be perfectly orthogonal, but to simplify the calculation, they can be assumed to be approximately orthogonal, thus using the above formula to approximate the effective value of the ripple current.

[0073] Based on the above embodiments, this embodiment will provide a detailed description of step S104:

[0074] Considering the DC voltage ripple rate, capacitance value, maximum DC voltage, switching frequency, and capacitor charging and discharging time, these parameters collectively determine the magnitude of the ripple current generated by the machine-side converter. The specific formula for the measurement model of the effective value of the ripple current of the machine-side converter is as follows:

[0075]

[0076] Where λ is the DC voltage ripple rate, C is the capacitance value, and U max It is the maximum DC voltage, f s It is the switching frequency of the machine-side converter, t c and t f These are the charging and discharging times of the capacitor, respectively.

[0077] Based on the above embodiments, this embodiment will provide a detailed description of step S105:

[0078] Consider the effective value of the grid-side converter output current, the modulation ratio, and the system power factor. These parameters reflect the contribution of the grid-side converter to the ripple current. The specific formula for the measurement model of the effective value of the grid-side converter ripple current is as follows:

[0079]

[0080] Among them, I out,rms It is the effective value of the grid-side converter output current, and M is the modulation ratio based on the dual PWM control strategy. It is the system power factor.

[0081] Based on the above embodiments, this embodiment provides a detailed description of step S106:

[0082] By combining the ripple currents from the generator-side and grid-side converters, we can obtain the total RMS value of the DC bus capacitor ripple current. This total RMS value is the result of the vector sum of the two component currents, providing a comprehensive assessment of the ripple current.

[0083] In summary, the expression for the DC link capacitor ripple current is:

[0084]

[0085] The DC bus capacitor ripple current not only affects the temperature range of the capacitor, but also has a significant impact on its electrical characteristics. This invention obtains an expression for the DC bus capacitor ripple current value of the wind power converter by considering parameters such as DC voltage ripple rate, machine-side converter switching frequency, and capacitor charging and discharging time. This can provide a reference for device selection by accurately calculating the DC bus capacitor ripple current.

[0086] This invention provides a device for measuring the ripple current of the DC bus capacitor in a wind power converter; the specific device may include:

[0087] The first relationship judgment module uses Kirchhoff's current law to determine the relationship between the DC bus capacitor ripple current, the machine-side converter output current, and the grid-side converter input current.

[0088] The first measurement model construction module is used to separate the DC component and AC component between the output current of the machine-side converter and the input current of the grid-side converter, and to construct a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the machine-side converter and the input current of the grid-side converter.

[0089] The second relationship judgment module is used to determine the relationship between the effective value of the DC bus capacitor ripple current, the effective value of the machine-side converter ripple current, and the effective value of the grid-side converter ripple current based on the vector superposition principle of AC current components.

[0090] The third measurement model construction module constructs a measurement model for the effective value of the ripple current of the machine-side converter based on the DC voltage ripple rate, capacitance value, maximum DC voltage, switching frequency of the machine-side converter, and charging and discharging time of the capacitor.

[0091] The fourth measurement model construction module constructs a measurement model for the effective value of the grid-side converter ripple current based on the effective value of the grid-side converter output current, the modulation ratio based on the dual PWM control strategy, and the system power factor.

[0092] The fifth measurement model construction module combines the measurement models of the effective value of the ripple current of the generator-side converter and the grid-side converter to construct a measurement model of the ripple current of the DC link capacitor.

[0093] The wind power converter DC bus capacitor ripple current measuring device of this embodiment is used to implement the aforementioned wind power converter DC bus capacitor ripple current measuring method. Therefore, the specific implementation of the wind power converter DC bus capacitor ripple current measuring device can be found in the embodiment section of the wind power converter DC bus capacitor ripple current measuring method above. So, its specific implementation can be referred to the description of the corresponding embodiment, and will not be repeated here.

[0094] A specific embodiment of the present invention also provides a wind power converter DC bus capacitor ripple current measuring device, comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the above-described wind power converter DC bus capacitor ripple current measuring method.

[0095] A specific embodiment of the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described method for measuring the ripple current of a DC bus capacitor in a wind power converter.

[0096] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for measuring the ripple current of the DC bus capacitor in a wind power converter, characterized in that, include: Kirchhoff's current law is used to determine the relationship between the DC bus capacitor ripple current, the machine-side converter output current, and the grid-side converter input current. The DC and AC components between the output current of the generator-side converter and the input current of the grid-side converter are separated, and a measurement model for the DC bus capacitor ripple current is constructed based on the AC component between the output current of the generator-side converter and the input current of the grid-side converter.

2. The method for measuring the ripple current of the DC bus capacitor of a wind power converter according to claim 1, characterized in that, The method for determining the relationship between the DC bus capacitor ripple current, the generator-side converter output current, and the grid-side converter input current using Kirchhoff's current law includes: Kirchhoff's Current Law is used to determine that the DC bus capacitor ripple current value is equal to the difference between the output current value of the machine-side converter and the input current value of the grid-side converter.

3. The method for measuring the DC bus capacitor ripple current of a wind power converter according to claim 1, characterized in that, The method separates the DC and AC components between the output current of the generator-side converter and the input current of the grid-side converter, and constructs a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the generator-side converter and the input current of the grid-side converter, including: Based on the fact that both the output current of the machine-side converter and the input current of the grid-side converter include DC and AC components, and that the DC components of the two are equal, the DC bus capacitor ripple current is determined to be equal to the difference between the AC component value of the output current of the machine-side converter and the AC component value of the input current of the grid-side converter, and a measurement model for the DC bus capacitor ripple current is constructed.

4. The method for measuring the ripple current of the DC bus capacitor of a wind power converter according to claim 1, characterized in that, The method for measuring the DC bus capacitor ripple current of the wind power converter also includes: The relationship between the effective values ​​of DC bus capacitor ripple current, machine-side converter ripple current, and grid-side converter ripple current is determined based on the vector superposition principle of AC current components. A measurement model for the effective value of the ripple current of the machine-side converter is constructed based on the DC voltage ripple rate, capacitance value, maximum DC voltage, switching frequency of the machine-side converter, and charging and discharging time of the capacitor. A measurement model for the effective value of the grid-side converter ripple current is constructed based on the effective value of the grid-side converter output current, the modulation ratio based on the dual PWM control strategy, and the system power factor. By combining the measurement models of the RMS value of the ripple current of the generator-side converter and the grid-side converter, a measurement model for the ripple current of the DC link capacitor is constructed.

5. The method for measuring the DC bus capacitor ripple current of a wind power converter according to claim 4, characterized in that, The relationship between the effective values ​​of the DC bus capacitor ripple current, the machine-side converter ripple current, and the grid-side converter ripple current, determined by the vector superposition principle of AC current components, includes: Based on the principle of vector superposition of AC current components, the square of the effective value of the DC bus capacitor ripple current is determined to be equal to the sum of the square of the effective value of the machine-side converter ripple current and the square of the effective value of the grid-side converter ripple current.

6. The method for measuring the DC bus capacitor ripple current of a wind power converter according to claim 4, characterized in that, The specific formula for the measurement model of the effective value of the ripple current of the machine-side converter is as follows: Where λ is the DC voltage ripple rate, C is the capacitance value, and U max It is the maximum DC voltage, f s It is the switching frequency of the machine-side converter, t c and t f These are the charging and discharging times of the capacitor, respectively.

7. The method for measuring the DC bus capacitor ripple current of a wind power converter according to claim 4, characterized in that, The specific formula for the measurement model of the effective value of the grid-side converter ripple current is as follows: Among them, I out,rms It is the effective value of the grid-side converter output current, and M is the modulation ratio based on the dual PWM control strategy. It is the system power factor.

8. A device for measuring the ripple current of the DC bus capacitor in a wind power converter, characterized in that, include: The first relationship judgment module uses Kirchhoff's current law to determine the relationship between the DC bus capacitor ripple current, the machine-side converter output current, and the grid-side converter input current. The first measurement model construction module is used to separate the DC and AC components between the output current of the machine-side converter and the input current of the grid-side converter, and to construct a measurement model for the DC bus capacitor ripple current based on the AC component between the output current of the machine-side converter and the input current of the grid-side converter.

9. A device for measuring the ripple current of the DC bus capacitor in a wind power converter, characterized in that, include: Memory, used to store computer programs; A processor is configured to execute the computer program to implement the steps of the method for measuring the DC bus capacitor ripple current of a wind power converter as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method for measuring the ripple current of a DC bus capacitor of a wind power converter as described in any one of claims 1 to 7.

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