Pre-charging loop DC bus current reconstruction method, storage medium and system
By utilizing the two-phase current and three-phase balance principle in a three-phase uncontrolled rectifier bridge, combined with the reverse blocking property of diodes, the DC bus current is reconstructed, solving the problem of difficult DC bus current reconstruction in existing technologies, and realizing accurate capacitor status monitoring and early fault warning.
Patent Information
- Application Number
- CN202511559768.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-29
- Publication Date
- 2026-02-06
AI Technical Summary
Existing technologies make it difficult to accurately reconstruct the DC bus current using sensors on the AC side of the pre-charge circuit, which makes it difficult to monitor capacitor status and provide early fault warnings.
By obtaining the current of two phases in the three-phase uncontrolled rectifier bridge, and using the three-phase balance principle and the reverse blocking property of diodes, the current of the third phase is derived, and the DC bus current is reconstructed based on this.
It enables accurate reconstruction of DC bus current with a limited number of sensors, reduces hardware costs, and improves capacitor health status assessment and early fault warning capabilities.
Smart Images
Figure CN121484820A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wind power generation technology, specifically relating to a method, storage medium, and system for reconstructing the DC bus current of a pre-charge circuit. Background Technology
[0002] With the rapid development of wind power generation technology, high-power wind power converters, as the core components of wind turbines, are crucial for operational reliability. The DC bus capacitors of the converter are vulnerable components, and their health directly affects the stability of the entire system. At the beginning of converter startup, the DC bus capacitors need to be pre-charged through a pre-charging circuit to prevent damage from sudden high-voltage current surges. During this process, the DC bus current is a key parameter reflecting the capacitor's health status; accurate monitoring of this current is of significant engineering value for capacitor condition assessment and fault early warning.
[0003] In existing technologies, due to cost and control cabinet space considerations, current sensors are typically not installed on the DC bus of wind power converters. The commonly used engineering approach is to install current sensors on the three-phase AC input side of the pre-charge circuit for indirect monitoring. Furthermore, to maximize cost savings, the principle of symmetry in the three-phase system is usually followed, and sensors are only placed on phases A and B.
[0004] However, the problem lies in the fact that the pre-charge circuit typically employs a three-phase uncontrolled rectifier bridge, which rectifies the AC current into DC current. However, a complex nonlinear relationship exists between AC and DC currents. In particular, due to the non-conducting and commutation processes of the diodes in the rectifier bridge, the DC bus current cannot be obtained through a simple mathematical conversion from the AC side current. Therefore, although existing technologies achieve AC side current monitoring at the optimal cost, it is difficult to accurately reconstruct the DC bus current value, which is crucial for capacitor condition monitoring, making it difficult to conduct reliability assessments for early fault warnings based on current data. Summary of the Invention
[0005] The purpose of this invention is to provide a method and system for reconstructing the DC bus current of the precharge circuit of a wind power converter, so as to overcome the shortcomings of the prior art which makes it difficult to reconstruct the DC bus current from the sensor current on the AC side of the precharge circuit.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention discloses a method for reconstructing the DC bus current of a pre-charge circuit, comprising the following steps: Obtain the first phase current and the second phase current on the AC side of the three-phase uncontrolled rectifier bridge, respectively. The third phase current is determined based on the first phase current, the second phase current, and the three-phase balance principle; Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the first phase current, the second phase current, and the third phase current.
[0007] The third phase current is determined based on the first phase current, the second phase current, and the three-phase balance principle, specifically as follows: Based on the first phase current, the second phase current, and the three-phase balance principle, the first formula is determined as follows:
[0008] In the formula, i c For the third phase current; i a i is the first phase current; b This is the second phase current; The third phase current is determined according to the first formula.
[0009] Based on the reverse blocking property of the diode, and reconstructing the DC bus current according to the first phase current, the second phase current, and the third phase current, specifically: The relationship between the directions of the first phase current, the second phase current, and the third phase current is determined based on the first formula. Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the relationship between the directions of the first phase current, the second phase current, and the third phase current.
[0010] The specific relationship between the directions of the first phase current, the second phase current, and the third phase current is as follows: The direction of the first phase current is the same as the direction of the second phase current, and the directions of the first phase current and the second phase current are both opposite to the direction of the third phase current.
[0011] Based on the reverse blocking property of diodes, and reconstructing the DC bus current according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, specifically: Based on the reverse blocking property of the diode, and according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, the second formula is determined as follows:
[0012] In the formula, i dc This refers to the DC bus current. Reconstruct the DC bus current according to the second formula.
[0013] The DC bus current is reconstructed according to the second formula, specifically as follows: The third formula is determined based on the second formula, and the third formula is:
[0014] The DC bus current is reconstructed according to the third formula.
[0015] The DC bus current is reconstructed according to the third formula, specifically as follows: The fourth formula is determined based on the third formula, and the fourth formula is: i dc
[0016] The DC bus current is reconstructed according to the fourth formula.
[0017] The first-phase current and the second-phase current on the AC side of the three-phase uncontrolled rectifier bridge are obtained respectively, specifically as follows: The first phase current and the second phase current are collected by current sensors installed on the corresponding phases of the AC side of the three-phase uncontrolled rectifier bridge.
[0018] The present invention also discloses a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the pre-charge circuit DC bus current reconfiguration method.
[0019] This invention also discloses a DC bus current reconfiguration system for a pre-charge circuit, comprising: At least one processor; The system also includes a memory communicatively connected to the at least one processor, the memory storing computer program instructions that, when executed by the at least one processor, enable the system to perform the precharge circuit DC bus current reconfiguration method.
[0020] Compared with the prior art, the present invention has the following beneficial technical effects: This invention determines the third-phase AC current information from the two-phase detection current through the three-phase balance principle, and reconstructs the DC bus current by utilizing the correspondence between the DC bus current and the three phase currents determined by the reverse blocking characteristics of the diode. This solves the problem of difficulty in accurately converting between AC side current and DC bus current due to the nonlinear working characteristics of the rectifier bridge. Furthermore, this invention accurately derives the DC bus current based on two-phase AC current signals, enabling more comprehensive system monitoring by fully exploring and utilizing the potential of existing sensors under the constraint of a limited number of sensors. Furthermore, this invention solves the problem of high hardware costs caused by having to install a dedicated current sensor on the DC bus side by using only the existing two-phase AC current sensor in the pre-charge circuit for data acquisition and algorithm reconstruction.
[0021] Furthermore, this invention does not rely on direct measurement of DC current on the DC side, but uses AC current to determine DC current, thus solving the problem of difficulty in assessing capacitor health status and insufficient early fault warning capability caused by the inability to accurately obtain DC bus current. Furthermore, this invention provides an efficient calculation expression to reconstruct DC current, solving the problem that the complex current conversion process in wind power converter controllers may cause excessive consumption of computing resources and affect the real-time performance of the main control task. Attached Figure Description
[0022] Figure 1 This is a flowchart of the method of the present invention.
[0023] Figure 2 This is a schematic diagram of the structure of the three-phase non-empty rectifier bridge in this invention. Detailed Implementation
[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only 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 should fall within the scope of protection of the present invention.
[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0026] Furthermore, it should be noted that the method of this invention mainly targets the normal operating conditions of a system during continuous operation. The situation where the instantaneous current of one or more phases is zero is attributed to a transient phenomenon inherent in diode commutation or instantaneous switching, with an extremely short duration. Given that such operating conditions are extremely short-lived and have limited impact on overall evaluation strategies based on average effects or continuous conduction states, they are typically considered secondary factors in conventional engineering analysis and calculation methods and do not require dedicated modeling consideration.
[0027] like Figure 1 As shown, this invention discloses a method for reconstructing the DC bus current of a pre-charge circuit, comprising the following steps: S1. Obtain the first phase current and the second phase current on the AC side of the three-phase uncontrolled rectifier bridge, respectively; like Figure 2 The diagram shown is a circuit diagram of a wind power converter during pre-charging. The overall topology of the pre-charging circuit is a three-phase uncontrolled rectifier bridge.
[0028] Figure 2 middle i a , i b , i c Let C be the current on the AC side of the pre-charge circuit, and let RSR be the current. Assume that only phases A and B of the three phases ABC have current sensors, and the three-phase currents are balanced. Let C be the DC bus capacitance, and RSR be the parasitic resistance of the DC bus capacitance. i dc This represents the DC bus current.
[0029] Then according to Figure 2 It can be seen that the first phase current and the second phase current on the AC side of the three-phase uncontrolled rectifier bridge are obtained respectively as follows: The first phase current and the second phase current are collected by current sensors installed on the corresponding phases of the AC side of the three-phase uncontrolled rectifier bridge.
[0030] S2. Determine the third phase current based on the first phase current, the second phase current, and the three-phase balance principle; Assuming three-phase balance, then according to the principle of three-phase current balance, we can obtain:
[0031] In the formula, i a This is the first phase current; i b This is the second phase current; i c This is the third phase current.
[0032] It should be noted that the technical solution of this invention is constructed based on an ideal three-phase balanced system model, possessing sufficient feasibility and rationality in engineering practice. Although actual power systems may have slight imbalance factors, in the mainstream operating conditions of industrial applications such as wind power converters, the system typically operates at a level highly close to ideal balance, with the imbalance controlled within allowable limits. The resulting errors have a negligible impact on the accuracy of the method described in this invention. Furthermore, mature error compensation techniques (such as filtering algorithms and adaptive correction) exist in the field, which can further eliminate deviations caused by non-ideal factors when necessary. Therefore, this invention, based on the principle of ideal three-phase balance, not only conforms to industry-standard engineering simplification practices but also significantly reduces system complexity and computational burden, providing a stable and reliable solution for core application scenarios.
[0033] The third phase current is determined based on the first phase current, the second phase current, and the three-phase balance principle, specifically as follows: S21. Based on the first phase current, the second phase current, and the three-phase balance principle, the first formula is determined as follows:
[0034] In the formula, i c For the third phase current; i a i is the first phase current; b This is the second phase current; S22. Determine the third phase current according to the first formula.
[0035] S3. Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the first phase current, the second phase current, and the third phase current.
[0036] Based on the reverse blocking property of the diode, and reconstructing the DC bus current according to the first phase current, the second phase current, and the third phase current, specifically: S31. Based on the reverse blocking property of the diode, and according to the first formula, determine the relationship between the direction of the first phase current, the direction of the second phase current, and the direction of the third phase current; The specific relationship between the directions of the first-phase current, the second-phase current, and the third-phase current is as follows: The direction of the first phase current is the same as the direction of the second phase current, and the directions of the first phase current and the second phase current are both opposite to the direction of the third phase current.
[0037] Specifically, the derivation process of the relationship between the directions of the first-phase current, the second-phase current, and the third-phase current is as follows: As can be seen from the first formula, except for the special case where all three phase currents are zero, the direction of the current in one phase is different from that in the other two phases, and the direction of the current in the other two phases is the same.
[0038] Assuming i c For the term to be solved, by the first formula It can be known that: i c and i a , i b The current flows in different directions, and i a and i b The current flows in the same direction.
[0039] The correctness of the three-phase current direction relationship established in this invention does not stem from the abstract derivation of ideal mathematical formulas, but is rooted in the working mechanism of the specific physical device, the "three-phase uncontrolled rectifier bridge," in the pre-charge circuit. In actual circuits, the unidirectional conductivity of diodes dictates that current can only flow in one direction, fundamentally constraining the current path between the AC and DC sides. Therefore, when we take the DC bus current as the quantity to be solved, it essentially corresponds to the current of the phase that the rectifier bridge conducts at a specific moment. At this time, the "positive" and "negative" current direction is not an arbitrary mathematical symbol, but a physical fact uniquely determined by the actual circuit topology and the diode conduction state. Specifically, during any conduction period, the DC bus current can only be provided by one phase (i.e., the phase to be solved), and this phase current must flow into the rectifier bridge in the positive direction; while in order to form a loop, the other two phases must jointly form a return path, and their current direction must be opposite to that of the phase to be solved, and since they are in the same loop, their directions are naturally always the same. This relationship is physically forced by the "commutation" process of the diode rectifier bridge, rather than being one of the mathematical possibilities.
[0040] S32. Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the relationship between the directions of the first phase current, the second phase current, and the third phase current.
[0041] Based on the reverse blocking property of diodes, and reconstructing the DC bus current according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, the specific steps are as follows: S321. Based on the reverse blocking property of the diode, and according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, the second formula is determined. The derivation of the second formula is as follows: According to the reverse blocking characteristic of diodes, the forward current in the three-phase current can only flow through the upper bridge arm diode, and the negative current can only flow through the lower bridge arm diode. The algebraic sum of the absolute values of the forward current is equal to the algebraic sum of the absolute values of the negative current, and is also equal to the DC current.
[0042] Assuming only phase C current is positive, then based on the aforementioned conclusion regarding the direction relationship of the three-phase currents, it can be concluded that the currents in phases A and B... i a , i b All are negative, and i a , i b If the current flows in the same direction, then the following second formula applies:
[0043] In the formula, i dc This represents the DC bus current.
[0044] When the c-phase current is negative, then according to the aforementioned conclusion regarding the direction relationship of the three-phase currents, the A and B phase currents... i a , i b All are positive, and i a , i b If the current flows in the same direction, then the following second formula applies:
[0045] In the formula, i dc This represents the DC bus current.
[0046] Since all subsequent calculations use absolute values, the third and fourth formulas will not change regardless of whether the c-phase current is positive or negative. To avoid redundancy, they will not be elaborated in detail.
[0047] S322. Reconstruct the DC bus current according to the second formula.
[0048] The DC bus current is reconstructed according to the second formula, specifically as follows: S3221. Determine the third formula based on the second formula. The third formula is:
[0049] S3222. Reconstruct the DC bus current according to the third formula.
[0050] The DC bus current is reconstructed according to the third formula, specifically: Based on the third formula, the fourth formula is determined as follows:
[0051] Reconstruct the DC bus current according to the fourth formula.
[0052] In engineering practice, current sensors are typically placed on the three-phase AC side of the converter's pre-charge circuit, such as phases A and B. Let's assume the currents in phases A and B are respectively... i a and i b Then the DC bus current can be reconstructed from the fourth formula. i dc The expression.
[0053] Furthermore, the fourth formula shows that the expression for the DC bus current can be reconstructed by measuring the two-phase current of the pre-charge circuit of the wind power converter, avoiding the need to install an additional current sensor on the DC bus side, reducing costs and improving the availability of computing resources.
[0054] This invention detects two-phase AC current signals and, combined with the three-phase balance principle, derives the directional and numerical relationships of the three-phase currents. It then utilizes the directional relationship between the three-phase AC currents and the reverse blocking property of diodes to reconstruct the mapping relationship between DC current and the three-phase currents. This solves the problem that the relationship between AC side current and DC side current is complex and difficult to accurately reconstruct through simple conversion due to the nonlinear characteristics of the three-phase uncontrolled rectifier bridge.
[0055] The present invention also discloses a computer-readable storage medium storing a computer program thereon, which implements a method for reconstructing the DC bus current of a precharge circuit when the computer program is executed by a processor.
[0056] This invention also discloses a DC bus current reconfiguration system for a pre-charge circuit, comprising: At least one processor; And a memory communicatively connected to at least one processor, the memory storing computer program instructions that, when executed by at least one processor, enable the system to execute a precharge loop DC bus current reconfiguration method.
[0057] The present invention has been described in detail above through specific embodiments. However, those skilled in the art should understand that these descriptions are exemplary and not restrictive. Within the scope of the technical principles and core concepts disclosed in the present invention, any equivalent transformations, structural modifications, or process improvements made based on the spirit of the present invention, including but not limited to reasonable adjustments to the order of method steps, equivalent replacements of logging curve combinations, or optimizations of discrimination model parameters, should be considered to fall within the protection scope of the present invention and be protected by patent law and its implementing regulations, as long as they do not depart from the essential content of the present invention.
Claims
1. A method for reconstructing the DC bus current of a pre-charge circuit, characterized in that, Includes the following steps: Obtain the first phase current and the second phase current on the AC side of the three-phase uncontrolled rectifier bridge, respectively. The third phase current is determined based on the first phase current, the second phase current, and the three-phase balance principle; Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the first phase current, the second phase current, and the third phase current.
2. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 1, characterized in that, The third phase current is determined based on the first phase current, the second phase current, and the three-phase balance principle, specifically as follows: Based on the first phase current, the second phase current, and the three-phase balance principle, the first formula is determined as follows: In the formula, i c For the third phase current; i a i is the first phase current; b This is the second phase current; The third phase current is determined according to the first formula.
3. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 2, characterized in that, Based on the reverse blocking property of the diode, and reconstructing the DC bus current according to the first phase current, the second phase current, and the third phase current, specifically: Based on the reverse blocking property of the diode, and according to the first formula, the relationship between the directions of the first phase current, the second phase current, and the third phase current is determined; Based on the reverse blocking property of the diode, the DC bus current is reconstructed according to the relationship between the directions of the first phase current, the second phase current, and the third phase current.
4. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 3, characterized in that, The specific relationship between the directions of the first phase current, the second phase current, and the third phase current is as follows: The direction of the first phase current is the same as the direction of the second phase current, and the directions of the first phase current and the second phase current are both opposite to the direction of the third phase current.
5. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 4, characterized in that, Based on the reverse blocking property of diodes, and reconstructing the DC bus current according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, specifically: Based on the reverse blocking property of the diode, and according to the relationship between the directions of the first phase current, the second phase current, and the third phase current, the second formula is determined as follows: In the formula, i dc This refers to the DC bus current. Reconstruct the DC bus current according to the second formula.
6. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 5, characterized in that, The DC bus current is reconstructed according to the second formula, specifically as follows: The third formula is determined based on the second formula, and the third formula is: The DC bus current is reconstructed according to the third formula.
7. The method for reconstructing the DC bus current of the pre-charge circuit according to claim 6, characterized in that, The DC bus current is reconstructed according to the third formula, specifically as follows: The fourth formula is determined based on the third formula, and the fourth formula is: i dc The DC bus current is reconstructed according to the fourth formula.
8. The method for reconstructing the DC bus current of the pre-charge circuit according to any one of claims 1-7, characterized in that, The first-phase current and the second-phase current on the AC side of the three-phase uncontrolled rectifier bridge are obtained respectively, specifically as follows: The first phase current and the second phase current are collected by current sensors installed on the corresponding phases of the AC side of the three-phase uncontrolled rectifier bridge.
9. A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described in any one of claims 1 to 8.
10. A DC bus current reconfiguration system for a pre-charge circuit, comprising: At least one processor; The system also includes a memory communicatively connected to the at least one processor, the memory storing computer program instructions that, when executed by the at least one processor, enable the system to perform the method as described in any one of claims 1 to 8.