Method, device and equipment for monitoring series capacitor on direct current link, medium and program product

Abstract

The invention discloses a method, a device, equipment, a medium and a program product for monitoring a series capacitor on a direct current link, and the method comprises the steps: carrying out the state control of a power switch, so as to control the charging and discharging states of an electrolytic capacitor, collecting the capacitor voltage data of the electrolytic capacitor in the charging and discharging process, the charging and discharging states comprise the charging state and the discharging state of the electrolytic capacitor, performing linear analysis based on the capacitor voltage data, determining the linear relation between the capacitance value of the electrolytic capacitor and the discharging time, and monitoring the electrolytic capacitor of a direct current link in the power converter according to the linear relation; due to the fact that the capacitor on the direct-current link is monitored on the basis of the linear relation by conducting linear analysis on the capacitance value and the discharge time of the electrolytic capacitor, monitoring complexity is effectively reduced, complex sampling and calculation are not needed, meanwhile, the state of the capacitor is accurately monitored, monitoring cost is effectively reduced, and monitoring efficiency is improved. And the capacitance monitoring efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a method, device, equipment, medium and program product for monitoring series capacitors on a DC link. Background Art

[0002] Capacitors are one of the most vulnerable components in power converters. Aluminum electrolytic capacitors have a shorter service life compared to other types of capacitors. Due to their low voltage rating, they are often connected in series, especially in high voltage DC links. To meet the total capacitance requirement, more capacitors are required, resulting in poor reliability.

[0003] At present, the main capacitor status monitoring schemes can be divided into three categories, including offline, quasi-online and real online schemes. All three schemes have problems and defects. The offline scheme requires stopping the operation of the converter. This method requires a lot of manual intervention and cannot be completed automatically; the quasi-online scheme cannot achieve continuous estimation during normal operation; the real-time online scheme needs to process a large amount of ripple data, which requires some complex algorithms, resulting in a significant increase in monitoring costs and complexity. In addition, due to the large amount of data processing, the real-time online scheme has calculation errors. Therefore, it is currently impossible to effectively monitor capacitors, and there are problems such as low efficiency, high cost, and large monitoring errors. Summary of the invention

[0004] The main purpose of the present invention is to provide a method, device, equipment, medium and program product for monitoring series capacitors on a DC link, aiming to solve the technical problems that the existing technology cannot effectively monitor capacitors, has low efficiency, high cost and large monitoring errors.

[0005] To achieve the above object, the present invention provides a method for monitoring a series capacitor on a DC link, which is applied to a power converter, wherein the power converter includes a power switch, a balancing resistor and an electrolytic capacitor, wherein the balancing resistor is connected in parallel with the electrolytic capacitor, and the method includes the following steps: Controlling the state of the power switch to control the charge and discharge state of the electrolytic capacitor, and collecting capacitance voltage data during the charge and discharge process of the electrolytic capacitor, wherein the charge and discharge state includes the charge state and the discharge state of the electrolytic capacitor; Performing a linear analysis based on the capacitance-voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; An electrolytic capacitor of a DC link in the power converter is monitored according to the linear relationship.

[0006] Optionally, the electrolytic capacitor includes a first capacitor and a second capacitor; the capacitor voltage data includes first capacitor voltage data, second capacitor voltage data and third capacitor voltage data; the state control of the power switch to control the charge and discharge state of the electrolytic capacitor and collect the capacitor voltage data during the charge and discharge process of the electrolytic capacitor includes: When the power switch is in an off state, collecting first capacitance voltage data of the first capacitor and the second capacitor; Controlling the power switch to turn on, and collecting second capacitor voltage data when the first capacitor is in a charging state and the second capacitor is in a discharging state; The power switch is controlled to be turned off, and third capacitor voltage data is collected when the first capacitor is in a discharging state and the second capacitor is in a charging state.

[0007] Optionally, the first capacitor voltage data includes: ; in, and is the capacitance voltage value of the first capacitor and the second capacitor, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, the DC link being a DC bus between the machine-side power module and the grid-side power module in the power converter; The second capacitor voltage data includes: ; in, is the capacitance voltage value of the first capacitor in the charging state, is the capacitance voltage value of the second capacitor in the discharge state, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, is the capacitance value of the first capacitor, is the capacitance value of the second capacitor, is the time constant, is the voltage division coefficient after the power switch is turned on, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; The third capacitor voltage data includes: ; in, is the voltage difference between the first capacitor and the second capacitor, is the capacitance voltage value of the first capacitor in the discharge state, is the capacitance voltage value of the second capacitor in a charging state.

[0008] Optionally, performing a linear analysis based on the capacitance-voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor includes: determining voltage difference information between the first capacitor and the second capacitor based on the capacitor voltage data; Obtaining the discharge time of the electrolytic capacitor during the charging and discharging process; A linear analysis is performed based on the voltage difference information and the discharge time to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time.

[0009] Optionally, performing a linear analysis based on the voltage difference information and the discharge time to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time includes: The total capacitance formula of the first capacitor and the second capacitor is determined based on the voltage difference information and the discharge time: ; in, is the total capacitance of the first capacitor and the second capacitor, is the voltage difference between the first capacitor and the second capacitor, is the DC link steady-state voltage value, is the voltage division coefficient after the power switch is turned on, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; Based on the total capacitance formula, a linear analysis is performed to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor: ; in, is the total capacitance of the first capacitor and the second capacitor, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance, is the voltage division coefficient after the power switch is turned on, is the instantaneous DC link voltage value.

[0010] Optionally, performing a linear analysis based on the capacitance-voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor includes: Obtaining test capacitance values ​​of the electrolytic capacitor collected under multiple temperature conditions; Performing linear analysis based on the capacitance-voltage data to obtain an initial relationship between the capacitance value and the discharge time of the electrolytic capacitor; The initial relationship is corrected according to the test capacitance value to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

[0011] In addition, to achieve the above-mentioned purpose, the present invention further proposes a monitoring device for capacitors connected in series on a DC link, the monitoring device for capacitors connected in series on a DC link comprising: A control module, used to control the state of the power switch to control the charge and discharge state of the electrolytic capacitor, and collect capacitor voltage data during the charge and discharge process of the electrolytic capacitor, wherein the charge and discharge state includes the charge state and discharge state of the electrolytic capacitor; An analysis module, configured to perform a linear analysis based on the capacitance voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; The monitoring module is used to monitor the electrolytic capacitor of the DC link in the power converter according to the linear relationship.

[0012] In addition, to achieve the above-mentioned purpose, the present application also proposes a device for monitoring capacitors in series on a DC link, the device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the method for monitoring capacitors in series on a DC link as described above.

[0013] In addition, to achieve the above objectives, the present application also proposes a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for monitoring series capacitors on a DC link as described above are implemented.

[0014] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the method for monitoring series capacitors on a DC link as described above are implemented.

[0015] The present invention is applied to a power converter, which includes a power switch, a balancing resistor and an electrolytic capacitor, wherein the balancing resistor is connected in parallel with the electrolytic capacitor. The present invention controls the charging and discharging state of the electrolytic capacitor by controlling the state of the power switch, and collects capacitor voltage data during the charging and discharging process of the electrolytic capacitor, wherein the charging and discharging state includes the charging state and the discharging state of the electrolytic capacitor; performs linear analysis based on the capacitor voltage data to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; monitors the electrolytic capacitor of the DC link in the power converter according to the linear relationship; and monitors the capacitor on the DC link based on the linear relationship by performing linear analysis on the capacitance value and the discharge time of the electrolytic capacitor, thereby effectively reducing the complexity of monitoring, achieving accurate monitoring of the capacitor state without the need for complex sampling and calculation, effectively reducing the monitoring cost, and improving the capacitor monitoring efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the description, are used to explain the principles of the present application.

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 It is a structural schematic diagram of a device for monitoring capacitors in series on a DC link in a hardware operating environment involved in an embodiment of the present invention; Figure 2 A schematic diagram of a flow chart of a first embodiment of a method for monitoring capacitors in series on a DC link according to the present invention; Figure 3 A circuit structure diagram of a power converter in an embodiment of a method for monitoring a series capacitor on a DC link of the present invention; Figure 4 A schematic diagram of a voltage curve of an electrolytic capacitor during a process of controlling a power switch to adjust a switch state in a method for monitoring a series capacitor on a DC link according to an embodiment of the present invention; Figure 5 It is an equivalent schematic diagram of multiple capacitors connected in series on a DC link in one embodiment of a method for monitoring capacitors connected in series on a DC link of the present invention; Figure 6 It is a structural block diagram of the first embodiment of the series capacitor monitoring device on the DC link of the present invention.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0021] Reference Figure 1 , Figure 1 The schematic diagram of the structure of the series capacitor monitoring device on the DC link in the hardware operating environment involved in the embodiment of the present invention.

[0022] like Figure 1 As shown, the DC link series capacitor monitoring device may include: a processor 1001, such as a central processing unit (CPU), a communication bus 1002, a user interface 1003, a network interface 1004, and a memory 1005. Among them, the communication bus 1002 is used to realize the connection and communication between these components. The user interface 1003 may include a display screen (Display), an input unit such as a keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface and a wireless interface. The network interface 1004 may optionally include a standard wired interface and a wireless interface (such as a wireless fidelity (Wireless-Fidelity, WI-FI) interface). The memory 1005 may be a high-speed random access memory (Random Access Memory, RAM), or a stable non-volatile memory (Non-Volatile Memory, NVM), such as a disk memory. The memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0023] Those skilled in the art will understand that Figure 1 The structure shown in the figure does not constitute a limitation on the series capacitor monitoring device on the DC link, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0024] like Figure 1 As shown, the memory 1005 as a computer-readable storage medium may include an operating system, a network communication module, a user interface module, and a monitoring program for series capacitors on a DC link.

[0025] exist Figure 1In the DC link series capacitor monitoring device shown, the network interface 1004 is mainly used for data communication with the network server; the user interface 1003 is mainly used for data interaction with the user; the processor 1001 and the memory 1005 in the DC link series capacitor monitoring device of the present invention can be set in the DC link series capacitor monitoring device, and the DC link series capacitor monitoring device calls the DC link series capacitor monitoring program stored in the memory 1005 through the processor 1001, and executes the DC link series capacitor monitoring method provided in the embodiment of the present invention.

[0026] The embodiment of the present invention provides a method for monitoring a series capacitor on a DC link, referring to Figure 2 , Figure 2 FIG. 1 is a flow chart of a first embodiment of a method for monitoring a series capacitor on a DC link according to the present invention.

[0027] In this embodiment, the method is applied to a power converter, the power converter includes a power switch, a balancing resistor and an electrolytic capacitor, the balancing resistor is connected in parallel with the electrolytic capacitor, and the DC link series capacitor monitoring method includes the following steps: Step S10: Control the state of the power switch to control the charge and discharge state of the electrolytic capacitor, and collect capacitor voltage data during the charge and discharge process of the electrolytic capacitor.

[0028] It should be noted that the execution subject of this embodiment may be a computing service device with data processing, network communication and program running functions, such as a control device of a power converter, a microcontroller, etc., or a terminal electronic device capable of realizing the above functions, etc. The following takes a monitoring device for series capacitors on a DC link (hereinafter referred to as monitoring device) as an example to illustrate this embodiment and the following embodiments.

[0029] It should be noted that the above-mentioned charging and discharging state includes the charging state and the discharging state of the electrolytic capacitor.

[0030] It can be understood that this embodiment is applied to a power converter (such as a wind power converter, etc.), and the power converter includes a power switch, a balancing resistor and an electrolytic capacitor, and the balancing resistor is connected in parallel with the electrolytic capacitor.

[0031] In some embodiments, reference Figure 3 , Figure 3: is a circuit structure diagram of a power converter, wherein the power converter includes a machine-side power module, a grid-side power module, and a DC bus connected between the machine-side power module and the grid-side power module, wherein the DC bus is a DC link, wherein the DC link includes an auxiliary discharge network and a grid-side capacitor, wherein the auxiliary discharge network includes a power switch and an auxiliary discharge resistor, wherein the grid-side capacitor includes an electrolytic capacitor and a balancing resistor, wherein C1 and C2 are electrolytic capacitors, and R b1 and R b2 is the balancing resistor, S is the power switch, and Ra is the auxiliary discharge resistor.

[0032] In some embodiments, in a wind power back-to-back power converter, two electrolytic capacitors are usually connected in series to share the DC voltage. To ensure voltage sharing, refer to Figure 3 , equal balancing resistance R b1 and R b2 Can be connected in parallel with each electrolytic capacitor.

[0033] It should be understood that the monitoring device may charge and discharge the electrolytic capacitor by controlling the power switch to open and close, and estimate the capacitance of the electrolytic capacitor by measuring the voltage response of the electrolytic capacitor and the instantaneous DC link voltage.

[0034] Further, in order to accurately collect capacitor voltage data to accurately analyze the linear relationship, the electrolytic capacitor includes a first capacitor and a second capacitor; the capacitor voltage data includes first capacitor voltage data, second capacitor voltage data and third capacitor voltage data; The above step S10 may include: Step S101: when the power switch is in an off state, collecting first capacitance voltage data of the first capacitor and the second capacitor; Step S102: controlling the power switch to turn on, and collecting second capacitor voltage data when the first capacitor is in a charging state and the second capacitor is in a discharging state; Step S103: controlling the power switch to be turned off, and collecting third capacitor voltage data when the first capacitor is in a discharging state and the second capacitor is in a charging state.

[0035] It can be understood that the monitoring device controlling the power switch may include three stages. The first stage includes: the power switch is in the off state. At this time, due to the existence of the balancing resistor, the voltage values ​​between the electrolytic capacitors are the same. In this stage, the first capacitor voltage data is collected; The second stage includes: controlling the power switch to turn on. At this time, due to the different analysis coefficients of the electrolytic capacitors, the first capacitor starts to charge and the second capacitor starts to discharge. The electrolytic capacitor on the DC link and the auxiliary discharge network (including the power switch and the auxiliary discharge resistor) form a first-order RC circuit. In this stage, the voltage data of the second capacitor is collected; The third stage includes: controlling the power switch to turn off, the first capacitor starts to discharge, and the second capacitor starts to charge. In this stage, the voltage data of the third capacitor is collected.

[0036] It should be noted that the first capacitor voltage data includes: ; in, and is the capacitance voltage value of the first capacitor and the second capacitor, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, the DC link being a DC bus between the machine-side power module and the grid-side power module in the power converter; The second capacitor voltage data includes: ; in, is the capacitance voltage value of the first capacitor in the charging state, is the capacitance voltage value of the second capacitor in the discharge state, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, is the capacitance value of the first capacitor, is the capacitance value of the second capacitor, is the time constant, is the voltage division coefficient after the power switch is turned on, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; The third capacitor voltage data includes: ; in, is the voltage difference between the first capacitor and the second capacitor, is the capacitance voltage value of the first capacitor in the discharge state, is the capacitance voltage value of the second capacitor in a charging state.

[0037] In some embodiments, the monitoring device can control the three phases of the power switch based on the time interval, for example, referring to Figure 4 , Figure 4 The schematic diagram of the voltage curve of the electrolytic capacitor in the process of controlling the power switch to adjust the switch state is shown in the figure. t0-t1 is the first stage, the power switch is turned off, and the voltage of the first capacitor and the second capacitor is the same; t1-t2 is the second stage, at this time, the power switch is turned on, and the second capacitor begins to discharge due to the different voltage division coefficients. At the same time, the first capacitor begins to charge, and the electrolytic capacitor and the auxiliary discharge network are connected in series to form a first-order RC circuit; t2-t3 is the third stage, from t2 to t3, the voltage value returns to the initial voltage, at this time the power switch is turned off, the second capacitor begins to charge, and the first capacitor begins to discharge. The time interval of t2-t3 should be long enough to restore the voltage of the first capacitor and the second capacitor to the initial voltage value. (i.e. the voltage value of the first stage), since the life of the electrolytic capacitor lasts for thousands of hours, the capacitance changes slowly, reducing the power loss and voltage stress on C1 during the charging and discharging process. The measurement process only lasts a few seconds every few hours.

[0038] In some embodiments, t0 depends on the time when the capacitor monitoring program is started, and t1 depends on the time when the local controller samples the capacitor voltage and calculates When a preset value, such as 50V, is reached, t2 only represents the moment when the converter returns to its initial state and does not involve control.

[0039] It should be noted that the method of monitoring the electrolytic capacitor of the DC link based on the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor of the present invention is applicable to different average DC link voltages. The auxiliary discharge resistor value affects the final voltage, and its resistance should be designed according to the charge and discharge time. In practical applications, electrolytic capacitors of the same type and batch number should have similar initial capacitance. At the same time, they have the same working conditions throughout their life cycle. Therefore, the first capacitor and the second capacitor should have similar degradation and capacitance. The total capacitance can also be measured by measuring u at a fixed discharge time. C2 (t) to estimate. But in this way, C1 + C2 becomes u C2 (t), which results in a higher computational burden on the controller. Since this method measures capacitance only through the charge and discharge characteristics of the capacitor, it is applicable not only to electrolytic capacitors but also to metallized polypropylene film capacitors.

[0040] In some embodiments, the DC link of the power converter may include a plurality of capacitors connected in series. Figure 5 , Figure 5 It is an equivalent schematic diagram of n capacitors connected in series on the DC link, where C1...C nis an electrolytic capacitor, S is a power switch R b1 ...R bn To balance the resistance, assume that the capacitance of all electrolytic capacitors is equal to C. Similar to two capacitors in series, the analysis process consists of three stages: Phase 1: The power switch S is turned off. Because of the existence of the balancing resistor, C1...C n The voltage between them is the same, at this time C n The voltage value can be expressed as: ; in, C n The voltage value, is the instantaneous DC link voltage value.

[0041] Phase 2: Power switch S is turned on, C n Discharge starts due to different voltage division coefficients, and at the same time, C1-C n-1 Start charging, the charging and discharging process can be expressed as: ; in, is the capacitance voltage value of the first capacitor in the charging state, is the capacitance voltage value of the second capacitor in the discharge state, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, is the capacitance value of the first capacitor, is the capacitance value of the second capacitor, is the time constant, is the voltage division coefficient after the power switch is turned on, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; Phase 3: The power switch S is turned off, and the voltage values ​​of all electrolytic capacitors gradually return to the steady-state value. The capacitance value C can be calculated based on the following formula: ;

[0042] Wherein, C is the total capacitance of the first capacitor and the second capacitor, is the voltage difference between the first capacitor and the second capacitor, is the DC link steady-state voltage value, is the voltage division coefficient after the power switch is turned on, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistor.

[0043] Step S20: performing a linear analysis based on the capacitance-voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

[0044] It should be noted that the capacitor voltage data may include the voltage value, charging time, discharging time, voltage division coefficient, instantaneous DC link voltage value, steady-state DC link voltage value and instantaneous DC link ripple voltage value of each electrolytic capacitor at different stages. The monitoring equipment can collect and measure the capacitor voltage data through a voltage sensor.

[0045] It can be understood that the monitoring device can construct an expression formula for the electrolytic capacitor based on the capacitance and voltage data, analyze the linear relationship between the capacitance value and the discharge time based on the expression formula, and construct a linear formula between the capacitance value and the discharge time based on the analysis result.

[0046] Furthermore, in order to accurately analyze the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor, the above step S20 may include: Step S201: determining voltage difference information between the first capacitor and the second capacitor based on the capacitance voltage data; Step S202: obtaining the discharge time of the electrolytic capacitor during the charge and discharge process; Step S203: performing a linear analysis based on the voltage difference information and the discharge time to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time.

[0047] It should be noted that, since the first capacitor and the second capacitor have similar initial capacitances and they have the same operating conditions throughout their life cycle, the first capacitor and the second capacitor should have similar degradation degrees and capacitances. Therefore, this embodiment can measure the capacitance by the charge and discharge characteristics of the capacitor, and is therefore applicable not only to electrolytic capacitors but also to metallized polypropylene film capacitors.

[0048] Furthermore, in order to effectively reduce the computational burden and ensure that the monitoring cost is reduced while improving the monitoring accuracy, the above step S203 may include: Step S2031: Determine a total capacitance formula of the first capacitor and the second capacitor based on the voltage difference information and the discharge time.

[0049] It should be noted that the above total capacitance formula may include: ; in, is the total capacitance of the first capacitor and the second capacitor, is the voltage difference between the first capacitor and the second capacitor, is the DC link steady-state voltage value, is the voltage division coefficient after the power switch is turned on, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; Step S2032: performing a linear analysis based on the total capacitance formula to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time.

[0050] It should be noted that the above linear relationship may be a linear formula between the capacitance value and the discharge time, which may include: ; in, is the total capacitance of the first capacitor and the second capacitor, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance, is the voltage division coefficient after the power switch is turned on, is the instantaneous DC link voltage value.

[0051] Further, in order to decouple the influence of temperature on the capacitor, the above step S20 may include: Step S21: obtaining the test capacitance values ​​of the electrolytic capacitor collected under multiple temperature conditions; Step S22: performing linear analysis based on the capacitance-voltage data to obtain an initial relationship between the capacitance value and the discharge time of the electrolytic capacitor; Step S23: Correcting the initial relationship according to the test capacitance value to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

[0052] It should be noted that in order to decouple the effect of temperature on the capacitance value of the electrolytic capacitor, the monitoring equipment can place the electrolytic capacitor in a hot temperature chamber for measurement and analysis at different temperatures. Record the capacitance results estimated by the proposed scheme and the capacitance results measured by the LCR meter. For example, the capacitor can be placed under different temperature conditions, and the power switch can be controlled separately to control the charge and discharge of the electrolytic capacitor, and the capacitor voltage data can be collected to obtain the capacitor voltage data under different temperature conditions.

[0053] In some embodiments, in order to improve the accuracy of state monitoring, a temperature sensor can be used. The capacitance measured by the LCR meter at different temperatures is stored in the microcontroller unit (MCU) in advance. A lookup table can be used to perform temperature correction during the estimation process.

[0054] Step S30: monitoring the electrolytic capacitor of the DC link in the power converter according to the linear relationship.

[0055] In some embodiments, the monitoring device samples and monitors the DC bus voltage U under steady-state operation conditions in response to the detection instruction during the steady-state operation of the power converter. DC and the voltage U across the series-connected electrolytic capacitors C1 and C2 on the DC link C1 and U C2 , turn on the auxiliary discharge switch S, C2 starts to discharge due to the different voltage division coefficients. At the same time, C1 starts to charge. The DC link capacitor C2 connected in series with the auxiliary discharge network forms a first-order RC circuit. The voltage values ​​of C1 and C2 that change with time during the charging and discharging process are sampled. The auxiliary discharge switch S is turned off, C2 starts to charge, and C1 starts to discharge. The voltage values ​​of C1 and C2 that change with time during the recovery process are sampled to obtain the capacitance voltage data. The capacitance value of the electrolytic capacitor is calculated based on the following calculation model: ; in, is the total capacitance of the electrolytic capacitor, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance, is the instantaneous DC link voltage value, is the voltage difference between the electrolytic capacitors, is the voltage division coefficient after the power switch is turned on.

[0056] The capacitance value is calculated based on the calculation model, and the health status of the electrolytic capacitor is determined based on the capacitance value of the electrolytic capacitor. When the capacitance value decreases and exceeds a preset threshold, it is determined to be a capacitor failure, thereby realizing the status monitoring of the capacitor.

[0057] This embodiment controls the charging and discharging state of the electrolytic capacitor by controlling the state of the power switch, and collects capacitor voltage data during the charging and discharging process of the electrolytic capacitor, wherein the charging and discharging state includes the charging state and the discharging state of the electrolytic capacitor; performs linear analysis based on the capacitor voltage data to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; monitors the electrolytic capacitor of the DC link in the power converter according to the linear relationship; because this embodiment performs linear analysis on the capacitance value and the discharge time of the electrolytic capacitor, and monitors the capacitor on the DC link based on the linear relationship, the monitoring complexity is effectively reduced, and accurate monitoring of the capacitor state is achieved without the need for complex sampling and calculation, thereby effectively reducing the monitoring cost and improving the capacitor monitoring efficiency.

[0058] In addition, an embodiment of the present invention further proposes a computer-readable storage medium, on which a series capacitor monitoring program for a DC link is stored. When the series capacitor monitoring program for a DC link is executed by a processor, the steps of the series capacitor monitoring method for a DC link as described above are implemented.

[0059] The computer-readable storage medium provided in the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM: Random Access Memory), a read-only memory (ROM: Read Only Memory), an erasable programmable read-only memory (EPROM: Erasable Programmable Read Only Memory or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM: CD-Read Only Memory), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, system or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency: Radio Frequency), etc., or any suitable combination of the above.

[0060] The computer-readable storage medium may be included in the device for monitoring the series capacitors on the DC link; or may exist independently without being assembled into the device for monitoring the series capacitors on the DC link.

[0061] In addition, an embodiment of the present invention further provides a computer program product, including a DC link series capacitor monitoring program, which implements the steps of the DC link series capacitor monitoring method as described above when executed by a processor.

[0062] The specific implementation of the computer program product of the present invention is basically the same as the embodiments of the above-mentioned method for monitoring capacitors in series on a DC link, and will not be repeated here.

[0063] Reference Figure 6 , Figure 6 It is a structural block diagram of the first embodiment of the series capacitor monitoring device on the DC link of the present invention.

[0064] like Figure 6As shown, the DC link series capacitor monitoring device proposed in the embodiment of the present invention includes: The control module 10 is used to control the state of the power switch to control the charge and discharge state of the electrolytic capacitor and collect the capacitance voltage data during the charge and discharge process of the electrolytic capacitor, wherein the charge and discharge state includes the charge state and discharge state of the electrolytic capacitor; An analysis module 20, configured to perform a linear analysis based on the capacitance voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; The monitoring module 30 is used to monitor the electrolytic capacitor of the DC link in the power converter according to the linear relationship.

[0065] Furthermore, the electrolytic capacitor includes a first capacitor and a second capacitor; the capacitor voltage data includes first capacitor voltage data, second capacitor voltage data and third capacitor voltage data; the control module 10 is also used to collect first capacitor voltage data of the first capacitor and the second capacitor when the power switch is in an off state, control the power switch to turn on, and collect second capacitor voltage data when the first capacitor is in a charging state and the second capacitor is in a discharging state; control the power switch to turn off, and collect third capacitor voltage data when the first capacitor is in a discharging state and the second capacitor is in a charging state.

[0066] Further, the first capacitor voltage data includes: ; in, and is the capacitance voltage value of the first capacitor and the second capacitor, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, the DC link being a DC bus between the machine-side power module and the grid-side power module in the power converter; The second capacitor voltage data includes: ; in, is the capacitance voltage value of the first capacitor in the charging state, is the capacitance voltage value of the second capacitor in the discharge state, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, is the capacitance value of the first capacitor, is the capacitance value of the second capacitor, is the time constant, is the voltage division coefficient after the power switch is turned on, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; The third capacitor voltage data includes: ; in, is the voltage difference between the first capacitor and the second capacitor, is the capacitance voltage value of the first capacitor in the discharge state, is the capacitance voltage value of the second capacitor in a charging state.

[0067] Furthermore, the analysis module 20 is also used to determine the voltage difference information between the first capacitor and the second capacitor based on the capacitor voltage data; obtain the discharge time of the electrolytic capacitor during the charging and discharging process; and perform linear analysis based on the voltage difference information and the discharge time to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

[0068] Further, the analysis module 20 is further configured to determine a total capacitance formula of the first capacitor and the second capacitor based on the voltage difference information and the discharge time: ; in, is the total capacitance of the first capacitor and the second capacitor, is the voltage difference between the first capacitor and the second capacitor, is the DC link steady-state voltage value, is the voltage division coefficient after the power switch is turned on, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; Based on the total capacitance formula, a linear analysis is performed to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor: ; in, is the total capacitance of the first capacitor and the second capacitor, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance, is the voltage division coefficient after the power switch is turned on, is the instantaneous DC link voltage value.

[0069] Furthermore, the analysis module 20 is also used to obtain the test capacitance value of the electrolytic capacitor collected under multiple temperature conditions; perform linear analysis based on the capacitance voltage data to obtain the initial relationship between the capacitance value and the discharge time of the electrolytic capacitor; and correct the initial relationship according to the test capacitance value to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

[0070] This embodiment controls the charging and discharging state of the electrolytic capacitor by controlling the state of the power switch, and collects capacitor voltage data during the charging and discharging process of the electrolytic capacitor, wherein the charging and discharging state includes the charging state and the discharging state of the electrolytic capacitor; performs linear analysis based on the capacitor voltage data to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; monitors the electrolytic capacitor of the DC link in the power converter according to the linear relationship; because this embodiment performs linear analysis on the capacitance value and the discharge time of the electrolytic capacitor, and monitors the capacitor on the DC link based on the linear relationship, the monitoring complexity is effectively reduced, and accurate monitoring of the capacitor state is achieved without the need for complex sampling and calculation, thereby effectively reducing the monitoring cost and improving the capacitor monitoring efficiency.

[0071] The device for monitoring capacitors in series on a DC link provided by the present application adopts the method for monitoring capacitors in series on a DC link in the above embodiment, and can solve the technical problem of monitoring capacitors in series on a DC link. Compared with the prior art, the beneficial effects of the device for monitoring capacitors in series on a DC link provided by the present application are the same as the beneficial effects of the method for monitoring capacitors in series on a DC link provided by the above embodiment, and other technical features of the device for monitoring capacitors in series on a DC link are the same as the features disclosed in the above embodiment method, which will not be described in detail here.

[0072] It should be understood that the above is only an example and does not constitute any limitation on the technical solution of the present invention. In specific applications, technicians in this field can make settings as needed, and the present invention does not limit this.

[0073] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of the present invention. In practical applications, technicians in this field can select part or all of them according to actual needs to achieve the purpose of the present embodiment, and no limitation is made here.

[0074] In addition, for technical details not fully described in this embodiment, reference may be made to the method for monitoring capacitors in series on a DC link provided in any embodiment of the present invention, and will not be repeated here.

[0075] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0076] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0077] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as a read-only memory / random access memory, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0078] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for monitoring capacitors in series on a DC link, characterized in that: The method is applied to a power converter, the power converter comprising a power switch, a balancing resistor and an electrolytic capacitor, the balancing resistor being connected in parallel with the electrolytic capacitor, and the method comprising: Controlling the state of the power switch to control the charge and discharge state of the electrolytic capacitor, and collecting capacitance voltage data during the charge and discharge process of the electrolytic capacitor, wherein the charge and discharge state includes the charge state and the discharge state of the electrolytic capacitor; Performing a linear analysis based on the capacitance-voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; An electrolytic capacitor of a DC link in the power converter is monitored according to the linear relationship.

2. The method for monitoring capacitors in series on a DC link according to claim 1, characterized in that: The electrolytic capacitor includes a first capacitor and a second capacitor; the capacitor voltage data includes first capacitor voltage data, second capacitor voltage data and third capacitor voltage data; the state control of the power switch to control the charge and discharge state of the electrolytic capacitor and collect the capacitor voltage data during the charge and discharge process of the electrolytic capacitor includes: When the power switch is in an off state, collecting first capacitance voltage data of the first capacitor and the second capacitor; Controlling the power switch to turn on, and collecting second capacitor voltage data when the first capacitor is in a charging state and the second capacitor is in a discharging state; The power switch is controlled to be turned off, and third capacitor voltage data is collected when the first capacitor is in a discharging state and the second capacitor is in a charging state.

3. The method for monitoring capacitors in series on a DC link according to claim 2, characterized in that: The first capacitor voltage data includes: ； in, and is the capacitance voltage value of the first capacitor and the second capacitor, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, the DC link being a DC bus between the machine-side power module and the grid-side power module in the power converter; The second capacitor voltage data includes: ； in, is the capacitance voltage value of the first capacitor in the charging state, is the capacitance voltage value of the second capacitor in the discharge state, is the instantaneous DC link voltage value, is the DC link steady-state voltage value, is the instantaneous DC link ripple voltage value, is the capacitance value of the first capacitor, is the capacitance value of the second capacitor, is the time constant, is the voltage division coefficient after the power switch is turned on, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; The third capacitor voltage data includes: ； in, is the voltage difference between the first capacitor and the second capacitor, is the capacitance voltage value of the first capacitor in the discharge state, is the capacitance voltage value of the second capacitor in a charging state.

4. The method for monitoring capacitors in series on a DC link according to any one of claims 1 to 3, characterized in that: The performing linear analysis based on the capacitance voltage data to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor includes: determining voltage difference information between the first capacitor and the second capacitor based on the capacitor voltage data; Obtaining the discharge time of the electrolytic capacitor during the charging and discharging process; A linear analysis is performed based on the voltage difference information and the discharge time to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time.

5. The method for monitoring capacitors in series on a DC link according to claim 4, characterized in that: The performing a linear analysis based on the voltage difference information and the discharge time to determine a linear relationship between the capacitance value of the electrolytic capacitor and the discharge time includes: The total capacitance formula of the first capacitor and the second capacitor is determined based on the voltage difference information and the discharge time: ； in, is the total capacitance of the first capacitor and the second capacitor, is the voltage difference between the first capacitor and the second capacitor, is the DC link steady-state voltage value, is the voltage division coefficient after the power switch is turned on, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance; Based on the total capacitance formula, a linear analysis is performed to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor: ； in, is the total capacitance of the first capacitor and the second capacitor, is the discharge time, Auxiliary discharge resistor connected in series with the power switch, is the balancing resistance, is the voltage division coefficient after the power switch is turned on, is the instantaneous DC link voltage value.

6. The method for monitoring capacitors in series on a DC link according to any one of claims 1 to 3, characterized in that: The performing linear analysis based on the capacitance voltage data to determine the linear relationship between the capacitance value and the discharge time of the electrolytic capacitor includes: Obtaining test capacitance values ​​of the electrolytic capacitor collected under multiple temperature conditions; Performing linear analysis based on the capacitance-voltage data to obtain an initial relationship between the capacitance value and the discharge time of the electrolytic capacitor; The initial relationship is corrected according to the test capacitance value to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor.

7. A monitoring device for series capacitors on a DC link, characterized in that: The DC link series capacitor monitoring device comprises: A control module, used to control the state of the power switch to control the charge and discharge state of the electrolytic capacitor, and collect capacitor voltage data during the charge and discharge process of the electrolytic capacitor, wherein the charge and discharge state includes the charge state and discharge state of the electrolytic capacitor; An analysis module, configured to perform a linear analysis based on the capacitance voltage data to determine a linear relationship between the capacitance value and the discharge time of the electrolytic capacitor; The monitoring module is used to monitor the electrolytic capacitor of the DC link in the power converter according to the linear relationship.

8. A monitoring device for series capacitors on a DC link, characterized in that: The DC link series capacitor monitoring device includes: a memory, a processor, and a DC link series capacitor monitoring program stored in the memory and executable on the processor, wherein the DC link series capacitor monitoring program is configured to implement a DC link series capacitor monitoring method as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a monitoring program for capacitors in series on a DC link, and when the monitoring program for capacitors in series on a DC link is executed by a processor, the method for monitoring capacitors in series on a DC link according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product comprises a monitoring program for series capacitors on a DC link, and when the monitoring program for series capacitors on a DC link is executed by a processor, the steps of the method for monitoring series capacitors on a DC link according to any one of claims 1 to 6 are implemented.

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