Bus capacitor ripple current estimation method and device, equipment and storage medium

Abstract

The embodiment of the invention provides a bus capacitor ripple current estimation method and device, equipment and a storage medium. The method comprises the following steps: acquiring power unit bus parameters of the medium-voltage frequency converter, wherein the power unit bus parameters comprise an output current effective value, a modulation wave frequency, a bus voltage fluctuation coefficient and a modulation ratio; estimating bus capacitor capacity according to the output current effective value, the modulation wave frequency and the bus voltage fluctuation coefficient; and estimating the ripple current of the bus capacitor according to the power unit bus parameter and the bus capacitor capacity. The method is used for replacing simulation software to estimate the ripple current, can accurately estimate the ripple current of the bus capacitor, and is convenient for practical engineering application.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a method, apparatus, device and storage medium for estimating bus capacitor ripple current. Background Technology

[0002] Medium-voltage frequency converters enable more precise and effective control of high-voltage motors, fans, pumps, and other equipment, helping users improve process efficiency and reduce operating costs. They are widely used in various fields such as power, metallurgy, petroleum, chemical, mining, and water supply. Currently, most manufacturers in the medium-voltage frequency converter industry adopt a multi-level cascaded structure, with the power unit being a major component. The bus capacitor, as one of the core components of the power unit, has significant implications for product quality and cost due to its capacity configuration and lifespan assessment. Capacitance configuration affects the magnitude of the bus ripple voltage, thus affecting the harmonic content of the power unit's output voltage; ripple current affects the core temperature rise of the capacitor during operation, thus affecting the capacitor's lifespan. Therefore, accurate calculation of the ripple current is crucial, as the capacitor's impact is significant.

[0003] In related technologies, the calculation of bus ripple current, especially the calculation of ripple current in the H-bridge inverter circuit of the power unit of medium-voltage frequency converter, mainly relies on simulation software. There is no accurate bus capacitor ripple current estimation method that conforms to actual engineering applications. Summary of the Invention

[0004] This application provides a method, apparatus, device, and storage medium for estimating bus capacitor ripple current, which can replace simulation software and accurately estimate the bus capacitor ripple current.

[0005] In a first aspect, embodiments of this application provide a method for estimating bus capacitor ripple current, including:

[0006] Obtain the power unit bus parameters of the medium-voltage frequency converter, including the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio;

[0007] Estimate the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient.

[0008] Estimate the ripple current of the bus capacitor based on the bus parameters and the bus capacitor capacity.

[0009] In one possible implementation, estimating the ripple current of the bus capacitor based on the bus parameters and the bus capacitor capacity includes:

[0010] Estimate the ripple current of the bus capacitor using the following formula:

[0011]

[0012] Where M is the modulation ratio, I o.rms C is the effective value of the output current. bus U is the bus capacitor capacitance. bus,max Here, α is the peak voltage of the bus, and f is the bus voltage fluctuation coefficient. m For the modulation wave frequency, t c For charging time, t d This refers to the discharge time.

[0013] In one possible implementation, estimating the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient includes:

[0014] Estimate the bus capacitor capacity using the following formula:

[0015]

[0016] Among them, C bus For the bus capacitor capacity, t d R is the discharge time. load Let α be the equivalent resistance of the load, and α be the bus voltage fluctuation coefficient.

[0017] In one possible implementation, the method further includes:

[0018] Estimate the charging time of the bus capacitor based on the bus voltage fluctuation coefficient and the angular frequency of the input voltage;

[0019] Based on the charging time and modulation wave frequency, estimate the discharge time of the bus capacitor;

[0020] The charging time of the bus capacitor is estimated using the following formula:

[0021]

[0022] The discharge time of the bus capacitor can be estimated using the following formula:

[0023]

[0024] Among them, t c For charging time, t d Where is the discharge time, α is the bus voltage fluctuation coefficient, and f m The frequency of the modulation wave.

[0025] Secondly, embodiments of this application provide a method for estimating bus capacitor ripple current, including:

[0026] Obtain the power unit bus parameters of the medium-voltage frequency converter, including the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio;

[0027] Estimate the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient.

[0028] The rectifier-side ripple current component of the bus capacitor is determined based on the bus capacitor capacity, and the inverter-side ripple current component of the bus capacitor is determined based on the modulation ratio and the effective value of the output current.

[0029] The ripple current of the bus capacitor is estimated based on the rectifier-side ripple current component and the inverter-side ripple current component.

[0030] In one possible implementation, determining the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacitance includes:

[0031] The rectifier-side ripple current component of the bus capacitor is determined based on the bus capacitor capacitance, bus voltage peak value, modulation wave frequency, and the charging and discharging time of the bus capacitor.

[0032] In one possible implementation, determining the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacitance, the peak bus voltage, the modulation wave frequency, and the charging and discharging times of the bus capacitor includes:

[0033] The peak charging current of the bus capacitor is determined based on the bus capacitor capacity, the modulation wave frequency, and the charging time of the bus capacitor; and the peak discharging current of the bus capacitor is determined based on the bus capacitor capacity, the modulation wave frequency, and the discharging time.

[0034] The effective charging value of the bus capacitor is determined based on the peak charging current, the charging time, and the modulation wave frequency; and the effective discharging value of the bus capacitor is determined based on the peak discharging current, the discharging time, and the modulation wave frequency.

[0035] The rectifier-side ripple current component of the bus capacitor is determined based on the effective charging value and the effective discharging value.

[0036] In one possible implementation, determining the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current includes:

[0037] The inverter-side ripple current component is estimated based on the RMS value of the output current and the modulation ratio.

[0038] In one possible implementation, the step of estimating the inverter-side ripple current component based on the RMS value of the output current and the modulation ratio includes:

[0039] The H-bridge input current of the medium-voltage frequency converter power unit is determined based on the effective value of the output current.

[0040] The inverter-side ripple current component is determined based on the H-bridge input current and the modulation ratio, or the inverter-side ripple current component is determined based on the average value and effective value of the H-bridge input current, wherein the average value is the average value of the H-bridge input current within a period.

[0041] Thirdly, embodiments of this application also provide a device for estimating bus capacitor ripple current, comprising:

[0042] The acquisition module is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0043] The processing module is used to process the power unit bus parameters of the medium-voltage frequency converter to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency and the bus voltage fluctuation coefficient.

[0044] The processing module is further configured to process the bus parameters and the bus capacitance to estimate the ripple current of the bus capacitor based on the bus parameters and the bus capacitance.

[0045] Fourthly, embodiments of this application also provide a device for estimating bus capacitor ripple current, comprising:

[0046] The acquisition module is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0047] The capacitance estimation module is used to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency, and the bus voltage fluctuation coefficient.

[0048] The rectifier-side component estimation module is used to determine the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacity.

[0049] The inverter-side component estimation module is used to determine the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current.

[0050] The ripple current estimation module is used to estimate the ripple current of the bus capacitor based on the ripple current components on the rectifier side and the ripple current components on the inverter side.

[0051] Fifthly, embodiments of this application provide an electronic device, including: a memory and a processor;

[0052] The memory stores computer-executed instructions;

[0053] The processor executes computer execution instructions stored in the memory, causing the processor to perform various possible implementations of the first and / or second aspects described above.

[0054] In a sixth aspect, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the first aspect and / or various possible implementations of the first aspect.

[0055] In a seventh aspect, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.

[0056] The bus capacitor ripple current estimation method, apparatus, device, and storage medium provided in this application embodiment consider the composition of the ripple current, the influence of the rectifier side and inverter side of the H-bridge inverter circuit on the ripple current, and other influencing factors to form an estimation relationship. Furthermore, before calculating the ripple current, the bus capacitor capacity configuration is estimated, and the ripple current of the bus capacitor is estimated by combining the estimated capacitor capacity, thus improving the accuracy of ripple current estimation. Moreover, the bus ripple current estimation method in this embodiment only requires obtaining the capacitor parameters and then estimating the ripple current through the calculated capacitor capacity, simplifying the ripple current calculation process and making it suitable for engineering applications. Attached Figure Description

[0057] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0058] Figure 1 A flowchart illustrating the method for estimating bus capacitor ripple current provided in this application. Figure 1 ;

[0059] Figure 2 This is a schematic diagram of the main circuit topology of the power unit of the medium-voltage frequency converter provided in this application;

[0060] Figure 3 A flowchart illustrating the method for estimating bus capacitor ripple current provided in this application. Figure 2 ;

[0061] Figure 4A comparison of the bus voltage waveforms after three-phase uncontrolled rectification with and without an inverter circuit;

[0062] Figure 5 for Figure 3 Detailed process diagram of S303;

[0063] Figure 6 This is a schematic diagram of the SPWM sampling process of an H-bridge inverter;

[0064] Figure 7 This is a schematic diagram of the power unit simulation model provided in the embodiments of this application;

[0065] Figure 8 This is a schematic diagram of the voltage waveform output based on simulation software testing.

[0066] Figure 9 This is a schematic diagram of the ripple current waveform output based on simulation software testing.

[0067] Figure 10 This is a schematic diagram of the voltage waveform tested based on the test platform;

[0068] Figure 11 This is a schematic diagram of the ripple current waveform tested based on the test platform;

[0069] Figure 12 A schematic diagram of an embodiment of the bus capacitor ripple current estimation device provided in this application;

[0070] Figure 13 A schematic diagram of another embodiment of the bus capacitor ripple current estimation device provided in this application;

[0071] Figure 14 A schematic diagram of the structure of the electronic device provided in this application.

[0072] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0073] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0074] Medium-voltage frequency converters enable more precise and effective control of high-voltage motors, fans, pumps, and other equipment, helping users improve process efficiency and reduce operating costs. They are widely used in various fields such as power, metallurgy, petroleum, chemical, mining, and water supply.

[0075] In the medium-voltage frequency converter industry, most manufacturers adopt a multi-level cascaded structure, such as the GH180 series, MVG2 series, MegaVert series, and HD9X series. The power unit is the main component of this structure, and the bus capacitor, as one of the core components of the power unit, has significant implications for product quality and cost due to its capacity configuration and lifespan assessment. The capacity configuration affects the magnitude of the bus ripple voltage, thereby affecting the harmonic content of the power unit's output voltage; the ripple current affects the core temperature rise of the capacitor during operation, thus affecting the capacitor's lifespan.

[0076] Therefore, accurately calculating the ripple current has a significant impact on the capacitor.

[0077] In related technologies, the calculation of bus ripple current, especially the calculation of ripple current in the H-bridge inverter circuit of the power unit of medium-voltage frequency converter, mainly relies on simulation software. There is no accurate bus capacitor ripple current estimation method that conforms to actual engineering applications.

[0078] Based on this, the bus capacitor ripple current estimation method provided in this application addresses the problem that related design methods either rely on simulation software or are overly complex and difficult to provide practical engineering operation guidance. It proposes an estimation method suitable for the power unit topology of medium-voltage frequency converters and easy for practical engineering applications. By first configuring the capacitor capacity, and then combining the capacitor capacity with the effective value of the output current, modulation frequency, bus voltage fluctuation coefficient, modulation ratio, etc., the ripple current of the bus capacitor is estimated. This method considers the influence of various factors on the accuracy of ripple current calculation, thus improving the accuracy of ripple current calculation.

[0079] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0080] Figure 1 A flowchart illustrating the bus capacitor ripple current estimation method provided in this application. Figure 1 ,like Figure 1 As shown, the method includes:

[0081] S101. Obtain the power unit bus parameters of the medium-voltage frequency converter;

[0082] Optionally, the power unit bus parameters of the medium-voltage frequency converter include, but are not limited to, the effective value of the output current, the modulation frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0083] The bus capacitor ripple current estimation method provided in this application is applicable to the power unit topology of medium-voltage frequency converters. For example... Figure 2 As shown, the main circuit topology of the power unit includes a three-phase uncontrolled rectifier circuit, a DC bus energy storage circuit, and an H-bridge inverter circuit. The bus capacitor is the core unit of the energy storage circuit. The ripple current based on the bus capacitor has a significant impact on the operation of the medium-voltage frequency converter. Therefore, accurate ripple current estimation plays a crucial role in capacitor selection and system stability.

[0084] The bus capacitor ripple current estimation method provided in this application can be applied to electronic equipment for bus capacitor selection. By estimating the bus capacitor ripple current, the correct selection of bus capacitors can be ensured according to requirements. Alternatively, it can also be applied to electronic equipment that uses a medium-voltage frequency converter to control motor speed. Estimating the bus capacitor ripple current facilitates ripple current control, maintains the operational stability and reliability of the electronic equipment, and can also extend the service life of the bus capacitor.

[0085] In the example of electronic equipment used for selecting bus capacitors, the power unit bus parameters of the medium-voltage frequency converter in this step are obtained through the input terminal of the electronic equipment. That is, the user inputs the power unit bus parameters of the medium-voltage frequency converter into the electronic equipment, and the electronic equipment can then obtain the relevant power unit bus parameters of the medium-voltage frequency converter.

[0086] In the example of electronic equipment using a medium-voltage frequency converter to control motor speed, the power unit bus parameters of the medium-voltage frequency converter in this step can be obtained by collecting data from the operation of the electronic equipment to obtain the actual modulation wave frequency and the actual effective value of the output current.

[0087] Optionally, the power unit bus parameters of the medium-voltage frequency converter include the effective value of the output current, the modulation frequency, the bus voltage fluctuation coefficient, and the modulation ratio. The effective value of the output current refers to the effective value of the current output by the bus capacitor as desired by the user, and is determined according to user requirements. The modulation frequency and modulation ratio are set according to user requirements. The bus voltage fluctuation coefficient is controlled within 10%, therefore, the bus voltage fluctuation coefficient is 0% to 10%.

[0088] S102. Estimate the bus capacitor capacity based on the effective value of the output current, the modulation wave frequency, and the bus voltage fluctuation coefficient.

[0089] As an example, the bus capacitance can be estimated using the following formula:

[0090]

[0091] Among them, C bus For the bus capacitor capacity, t d R is the discharge time. load Let α be the equivalent resistance of the load, and α be the bus voltage fluctuation coefficient.

[0092] Alternatively, the equivalent resistance of the load can be calculated using the following formula:

[0093]

[0094] Among them, U bus.max P is the peak voltage of the bus. load This represents the load power.

[0095] As an example, according to the standard for medium-voltage frequency converters, the peak bus voltage is selected according to the standard, and the load power is calculated based on the peak bus voltage and the effective value of the output current.

[0096] Optionally, the sum of the charging and discharging times of the bus capacitor is the charging and discharging cycle of the bus capacitor (which can also be expressed as the charging and discharging frequency). Since the charging and discharging frequency of the bus capacitor is affected by the modulation wave frequency of the H-bridge inverter, this embodiment of the application combines the influence of the modulation wave frequency of the H-bridge inverter on the charging and discharging time, and calculates the charging and discharging time of the bus capacitor based on the bus voltage fluctuation coefficient, the angular frequency of the input voltage, and the modulation wave frequency.

[0097] Therefore, by inputting the effective value of the output current of the bus capacitor into the electronic device, the load power can be calculated based on the effective value of the output current and the peak voltage of the bus, and then the load equivalent resistance of the bus capacitor can be calculated based on the peak voltage of the bus and the load power.

[0098] Furthermore, by inputting the bus voltage fluctuation coefficient and the modulation wave frequency into the electronic device, the discharge and charging times of the bus capacitor can be calculated based on the angular frequency of the input voltage, the bus voltage fluctuation coefficient, and the modulation wave frequency. Then, the bus capacitor capacity can be estimated based on the discharge time, the equivalent load resistance, and the bus voltage fluctuation coefficient (using the aforementioned formula).

[0099] As an example, the charging time of the bus capacitor can be estimated using the following formula:

[0100]

[0101] As an example, the discharge time of the bus capacitor can be estimated using the following formula:

[0102]

[0103] Among them, t c For charging time, t dWhere is the discharge time, α is the bus voltage fluctuation coefficient, and f m ω is the frequency of the modulated wave. g ω is the angular frequency of the input voltage.

[0104] S103. Estimate the ripple current of the bus capacitor based on the bus parameters and the bus capacitor capacity.

[0105] As an example, the ripple current of the bus capacitor can be estimated using the following formula:

[0106]

[0107] Where M is the modulation ratio, I o.rms C is the effective value of the output current. bus U is the bus capacitor capacitance. bus,max Where α is the peak ripple voltage, f is the bus voltage fluctuation coefficient, and f is the peak ripple voltage. m For the modulation wave frequency, t c For charging time, t d This refers to the discharge time.

[0108] The above formula is the output formula for the ripple current of the bus capacitor. In practical applications, the obtained inverter bus parameters include the effective value of the output current I. o.rms Modulation wave frequency f m The bus voltage fluctuation coefficient α and modulation ratio M are used. The bus capacitor capacity is estimated using S102. Before estimating the bus capacitor capacity, the charging and discharging times of the bus capacitor also need to be calculated. Therefore, the estimation of the bus capacitor ripple current in this embodiment, in addition to using the above formula, also includes a ripple current estimation process. This estimation process includes estimating the charging time, discharging time, and equivalent load resistance of the bus capacitor based on the input power unit bus parameters of the medium-voltage inverter. Then, based on the discharging time, equivalent load resistance, and the power unit bus parameters of the medium-voltage inverter, the bus capacitor capacity is estimated. Finally, the ripple current is estimated based on the bus capacitor capacity, charging time, discharging time, and the power unit bus parameters of the medium-voltage inverter.

[0109] It should be noted that the above ripple current output formula and ripple current estimation process take into account the composition of the ripple current, the influence of the rectifier side and inverter side of the H-bridge inverter circuit on the ripple current, and so on. It is formed after comprehensively considering various influencing factors.

[0110] The bus capacitor ripple current estimation method provided in this embodiment is based on considering the composition of the ripple current, the influence of the rectifier side and inverter side of the H-bridge inverter circuit on the ripple current, and other influencing factors. Furthermore, before calculating the ripple current, the bus capacitor capacity configuration is estimated, and the ripple current of the bus capacitor is estimated by combining the estimated capacitor capacity, thus improving the accuracy of the ripple current estimation. Moreover, this bus ripple current estimation method only requires obtaining the capacitor parameters and then estimating the ripple current through the calculated capacitor capacity, simplifying the ripple current calculation process and making it suitable for engineering applications.

[0111] Figure 3 A flowchart illustrating the bus capacitor ripple current estimation method provided in this application. Figure 2 ,like Figure 3 As shown, in this embodiment... Figure 1 and Figure 2 Based on the embodiments, the principle process of estimating bus capacitor ripple current in the above embodiments will be described in detail. The method includes:

[0112] S301. Obtain the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0113] Optionally, in this step, the acquisition of the power unit bus parameters of the medium-voltage frequency converter is the same as described above. Figure 1 The embodiments shown are the same; please refer to the above for details. Figure 1 The embodiments shown will not be described again here.

[0114] S302. Estimate the bus capacitor capacity based on the effective value of the output current, the modulation wave frequency, and the bus voltage fluctuation coefficient.

[0115] Optionally, in this step, the method for estimating the bus capacitor capacity is the same as described above. Figure 1 The bus capacitor capacity estimation method is the same in the illustrated embodiments. The bus capacitor capacity is estimated using the following formula:

[0116]

[0117] Among them, C bus For the bus capacitor capacity, t d R is the discharge time. load Let α be the equivalent resistance of the load, and α be the bus voltage fluctuation coefficient.

[0118] Alternatively, the equivalent resistance of the load can be calculated using the following formula:

[0119]

[0120] Among them, U bus.maxP is the peak voltage of the bus. load This represents the load power.

[0121] As an example, according to the standard for medium-voltage frequency converters, the peak bus voltage is selected according to the standard, and the load power is calculated based on the peak bus voltage and the effective value of the output current.

[0122] Therefore, in this embodiment, the bus capacitor capacity is determined based on the capacitor discharge time, the load equivalent resistance, and the bus voltage fluctuation coefficient.

[0123] Optionally, the presence of the H-bridge inverter in the medium-voltage frequency converter will affect the charging and discharging cycle of the capacitor. For example, the charging and discharging cycle of the capacitor including the inverter circuit is three times that of the capacitor without the inverter circuit. See reference for details. Figure 4 .

[0124] The bus voltage waveform equation excluding the inverter circuit is as follows:

[0125] U bus (t)=U bus.max cos(ω g (t p -t));

[0126] Among them, U bus.max ω is the peak voltage of the capacitor bus. g Let t be the angular frequency of the input voltage. p U is the time corresponding to the peak value of the bus voltage. bus Let be the capacitor bus voltage at time t.

[0127] like Figure 4 As shown, when t = t p At that time, U bus The maximum value U bus.max The starting time of bus capacitor charging at t = t0, U bus The initial value for charging the bus capacitor.

[0128] Based on this, t is calculated respectively. p The bus voltage at time t0 and t0, t p The difference between the bus voltage at time t0 and time t0 is the voltage difference during the charging cycle.

[0129] U bus (t p )-U bus (t0)=U bus.max cos(ω g (t p -t p )-U bus.max cos(ω g (t p -t0));

[0130] Since the charging and discharging cycle of the capacitor including the inverter circuit is three times that of the charging and discharging cycle without the inverter circuit, the corresponding equation for the bus voltage waveform including the inverter circuit is:

[0131]

[0132] Wherein, α is the bus voltage fluctuation coefficient. Since the bus voltage fluctuation coefficient affects the ripple current calculation, the charging and discharging time of the bus capacitor is calculated in combination with the bus voltage fluctuation coefficient in this embodiment.

[0133] By further simplifying the above bus voltage waveform equation, the charging time of the bus capacitor can be obtained:

[0134]

[0135] Optionally, the sum of the charging and discharging times of the bus capacitor is the charging and discharging cycle of the bus capacitor (which can also be expressed as the charging and discharging frequency). Since the charging and discharging frequency of the bus capacitor is affected by the modulation wave frequency of the H-bridge inverter, this embodiment considers the influence of the modulation wave frequency of the H-bridge inverter on the charging and discharging time, and calculates the charging and discharging time of the bus capacitor based on the bus voltage fluctuation coefficient, the angular frequency of the input voltage, and the modulation wave frequency.

[0136] As an example, the discharge time of the bus capacitor can be estimated using the following formula:

[0137]

[0138] Among them, t c For charging time, t d Where is the discharge time, α is the bus voltage fluctuation coefficient, and f m ω is the frequency of the modulated wave. g ω is the angular frequency of the input voltage.

[0139] Based on the above principle, by inputting the effective value of the output current of the bus capacitor into the electronic device, the load power can be calculated based on the effective value of the output current and the peak voltage of the bus. Then, the load equivalent resistance of the bus capacitor can be calculated based on the peak voltage of the bus and the load power.

[0140] Furthermore, by inputting the bus voltage fluctuation coefficient and the modulation wave frequency into the electronic device, the discharge and charging times of the bus capacitor can be calculated based on the angular frequency of the input voltage, the bus voltage fluctuation coefficient, and the modulation wave frequency. Then, the bus capacitor capacity can be estimated based on the discharge time, the equivalent load resistance, and the bus voltage fluctuation coefficient (using the aforementioned formula).

[0141] Taking a power unit with a rated input voltage of 690V, a peak bus voltage of 975V, a product design ripple voltage coefficient of 10%, a modulation frequency of 50Hz, and an output power of 144kVA (200A current, 720V voltage) as an example, the bus capacitor capacity can be calculated to be 8193uF using the above parameters and the formula for calculating bus capacitor capacity. Considering the actual capacitor type and product design cost, a 400V / 12000uF aluminum electrolytic capacitor is ultimately selected, arranged in a 3-series-2-parallel configuration, with a capacitance of 8000uF.

[0142] Therefore, in the electronic equipment to which the bus capacitor ripple current estimation method of this application is applied, the bus capacitor is estimated through the above-mentioned logical operation.

[0143] In this step, when analyzing the capacitor charging and discharging time, the influence of the inverter circuit on the charging and discharging time was considered, and the charging and discharging time was corrected to improve the effectiveness of the capacitor capacity calculation.

[0144] S303. Determine the rectifier side ripple current component of the bus capacitor based on the bus capacitor capacity.

[0145] Optionally, the rectifier-side ripple current component is the ripple current output from the rectifier side, which is one of the components of the capacitor ripple current. Calculating the rectifier-side ripple current component separately, and then combining them based on the influence of the rectifier-side ripple current component on the capacitor ripple current, can improve the final calculation result of the capacitor ripple current.

[0146] As an example, the rectifier-side ripple current component needs to consider the ripple current generated during charging and discharging. Therefore, the rectifier-side ripple current component needs to be calculated by combining the effective current values ​​generated during charging and discharging. The rectifier-side ripple current component can be estimated in the following way:

[0147] Figure 5 A schematic diagram illustrating the estimation process of the ripple current component on the rectifier side of the bus capacitor provided in this application is shown below. Figure 5 As shown, it includes:

[0148] S501, determine the peak charging current of the bus capacitor based on the bus capacitor capacity, modulation wave frequency and bus capacitor charging time;

[0149] S502, determine the effective charging value of the bus capacitor based on the peak charging current, charging time, and modulation wave frequency;

[0150] To improve the accuracy of the rectifier-side ripple current component calculation, the effective value of the bus capacitor during the charging process is used to calculate the rectifier-side ripple current component.

[0151] In this embodiment, the effective charging value of the bus capacitor is calculated using the charging peak value of the bus capacitor.

[0152] As an example, the peak charging current is calculated using the following formula:

[0153]

[0154] Among them, I c.peak C is the peak charging current. bus U is the bus capacitor capacitance. bus.max t is the peak voltage of the capacitor bus. c This refers to the charging time.

[0155] As an example, the effective charging value is calculated using the following formula:

[0156]

[0157] Among them, I c.peak I represents the peak charging current. c.rms f is the effective charging value. m For the modulation wave frequency, t c This refers to the charging time.

[0158] S503, determine the peak discharge current of the bus capacitor based on the bus capacitor capacitance, modulation wave frequency and discharge time;

[0159] S504. Determine the effective discharge value of the bus capacitor based on the peak discharge current, discharge time, and modulation wave frequency.

[0160] To improve the accuracy of the rectifier-side ripple current component calculation, the effective value of the bus capacitor during the discharge process is used to calculate the rectifier-side ripple current component.

[0161] In this embodiment, the effective discharge value of the bus capacitor is calculated using the discharge peak value of the bus capacitor.

[0162] As an example, the peak discharge current is calculated using the following formula:

[0163]

[0164] Among them, I d.peak C is the peak discharge current. bus C is the bus capacitor capacitance. bus.max t is the peak voltage of the capacitor bus. d This refers to the discharge time.

[0165] As an example, the effective value of discharge is calculated using the following formula:

[0166]

[0167] Among them, I d.peak I is the peak discharge current. d.rms t is the effective value of discharge. d f is the discharge time. m The frequency of the modulation wave.

[0168] S505 determines the rectifier side ripple current component of the bus capacitor based on the effective charging value and the effective discharging value.

[0169] As an example, the rectifier-side ripple current component of the bus capacitor is estimated by the sum of the effective charging value and the effective discharging value.

[0170] As an example, the rectifier-side ripple current component is estimated using the following formula:

[0171]

[0172] Based on the above I c.rms The calculation formula and I d.rms Substituting the formula for calculating the rectifier side ripple current component into the formula for calculating the rectifier side ripple current, we obtain the formula for calculating the rectifier side ripple current as follows:

[0173]

[0174] Among them, I rectifier.rms C represents the rectifier-side ripple current component. bus C is the bus capacitor capacitance. bus.max t is the peak voltage of the capacitor bus. c For charging time, t d f is the discharge time. m The frequency of the modulation wave.

[0175] Therefore, in this embodiment, the rectifier-side ripple current component of the bus capacitor is determined by the bus capacitor capacitance, peak bus voltage, modulation frequency, and charging and discharging times of the bus capacitor. In practical applications, the bus capacitor capacitance, charging and discharging times are calculated based on the capacitor parameters, and then the rectifier-side ripple current component of the bus capacitor is calculated separately using these parameters.

[0176] In this step, the influence of the rectifier-side output ripple current is fully considered. The bus capacitor ripple current is subdivided into rectifier-side components and inverter-side components for estimation, making the bus capacitor ripple current more accurate and suitable for the topology of medium-voltage inverter power units.

[0177] S304. Determine the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current.

[0178] In this step, the influence of the inverter on the ripple current is calculated separately. For example, a portion of the bus capacitor ripple current originates from the inverter-side ripple current component. This embodiment considers the influence of the inverter on the ripple current, calculates the inverter-side ripple current component to correct the bus capacitor ripple current, resulting in higher accuracy of the output ripple current.

[0179] As an example, the inverter-side ripple current component is estimated based on the RMS value of the output current and the modulation ratio, and is calculated using the following formula:

[0180]

[0181] Among them, I inverter.rms The inverter-side ripple current component is M, where M is the modulation ratio and I is the modulation ratio. o.rms This is the effective value of the output current.

[0182] In this step, the inverter-side ripple current component is calculated using the fundamental equivalent analysis method, assuming that most of the current ripple on the bus is absorbed by the capacitor and ignoring the influence of high-frequency harmonic components.

[0183] The output current of the power unit of a medium-voltage frequency converter is obtained using the following formula:

[0184]

[0185] Where, ω o Let ω be the angular frequency of the input voltage, and t be the moment of the output current.

[0186] Correspondingly, the input current of the H-bridge inverter is obtained through the following formula:

[0187] i in (t)=(S U -S V )i o (t) (2);

[0188] Among them, S u S is the switching function of the U-phase bridge. v This is the switching function for the V-phase bridge.

[0189] Medium-voltage frequency converters typically employ SPWM modulation in their power units. Taking the upper IGBTs of the U-phase bridge and V-phase bridge as an example, in one carrier cycle T... s Internally, the relationship between the modulated wave and the carrier wave is as follows: Figure 6 As shown; according to the principle of similar triangles, we can obtain:

[0190]

[0191] Where t1 and t2 are the times when the modulated wave intersects with the carrier wave, respectively; Um U s These are the amplitudes of the modulating wave and the carrier wave, respectively; ω m ω is the angular frequency of the modulated wave.

[0192] Further results were obtained:

[0193]

[0194] Where t2-t1 is the off-time of the upper IGBT within one carrier cycle, denoted as t. o f f ;U m / U s Let M be the modulation ratio.

[0195] Within one carrier cycle, the amplitude of the modulated wave changes very little, therefore sin(ω) m t1) and sin(ω m t2) are all approximately sin(ω) m Therefore, the above formula simplifies to: t),

[0196]

[0197] Furthermore, the switching function under SPWM modulation is:

[0198]

[0199] Based on this, the switching functions of the U-phase bridge and V-phase bridge of the H-bridge inverter are:

[0200]

[0201] If the phase of the power unit's output current is taken as the reference point, the modulated wave phase leads. For the power factor angle, the switching functions of the U-phase bridge and V-phase bridge of the H-bridge inverter are simplified as follows:

[0202]

[0203] Combining (1), (2), and (8) above, the input current function of the H-bridge inverter is obtained as follows:

[0204]

[0205] Based on the input current function of the H-bridge inverter, the inverter-side ripple current can be obtained through the following two examples.

[0206] As an example, the H-bridge input current of the medium-voltage inverter power unit is determined based on the effective value of the output current; then, the inverter-side ripple current component is determined based on the H-bridge input current and the modulation ratio.

[0207] By performing trigonometric decomposition on the H-bridge input current function (9), the following formula is obtained:

[0208]

[0209] in, This refers to the AC component provided by the bus capacitor, which is the ripple current on the inverter side.

[0210] The output current of the power unit exhibits a symmetrical positive and negative half-wave. Analyzing the output current waveform over half a cycle, the effective value of the ripple current over the entire cycle is obtained by calculating the root mean square (RMS). The effective value of the ripple current is obtained using the following formula:

[0211]

[0212] Where T0 is the period of the output current.

[0213] Based on the definite integral operation, the inverter-side ripple current component is calculated:

[0214]

[0215] As an example, the inverter-side ripple current component is determined based on the average and RMS values ​​of the H-bridge input current. The average value is the average value of the H-bridge input current over the cycle.

[0216] Alternatively, the average value of the H-bridge input current can be obtained using the following formula:

[0217]

[0218] After simplification, we get:

[0219]

[0220] Alternatively, the effective value of the H-bridge input current can be obtained using the following formula:

[0221]

[0222] After simplification, we get:

[0223]

[0224] Optionally, in this embodiment, the inverter-side ripple current component is obtained using the following formula:

[0225]

[0226] After substituting and simplifying the above formula, the inverter-side ripple current component can be estimated using the following formula:

[0227]

[0228] In this step, the influence of the inverter side on the ripple current is fully considered. The bus capacitor ripple current is subdivided into rectifier side components and inverter side components for estimation, making the bus capacitor ripple current more accurate and suitable for the topology of medium voltage inverter power unit.

[0229] S305. Estimate the ripple current of the bus capacitor based on the ripple current components on the rectifier side and the inverter side.

[0230] Optionally, the inverter-side ripple current component is the ripple current input to the inverter side, which is one of the components of the capacitor ripple current. Calculating the inverter-side and rectifier-side ripple current components separately, and then combining their effects on the capacitor according to Parseval's theorem, can improve the final calculation result for the capacitor.

[0231] As an example, in this step, the rectifier-side ripple current component is estimated using the following formula:

[0232]

[0233] The inverter-side ripple current is estimated using the following formula:

[0234]

[0235] Therefore, the bus capacitor ripple current is:

[0236]

[0237] In this embodiment, based on the influence of power unit topology on capacitor charging and discharging time, the charging and discharging time of the capacitor is first calculated, and then the capacitor capacity configuration is calculated based on the charging and discharging time. Next, based on this capacity selection, the ripple current output from the rectifier side and the ripple current input from the inverter side are calculated respectively. To facilitate practical engineering applications, the fundamental equivalent analysis method is used to simplify the calculation of the inverter side ripple current. Finally, according to Parseval's theorem, an estimation formula for the bus capacitor ripple current is obtained. This estimation formula for the bus capacitor ripple current is applied to capacitor selection and ripple current calculation equipment, or to equipment equipped with a medium-voltage frequency converter, to accurately calculate the capacitor capacity and bus capacitor ripple current, replacing simulation software for calculating the bus ripple current.

[0238] The bus capacitor ripple current estimation method provided in this embodiment of the application estimates the bus capacitor ripple current by separately calculating the capacitor capacitance, the rectifier-side ripple current component, and the inverter-side ripple current component, and then combining the rectifier-side and inverter-side ripple current components. This method comprehensively considers the influence of rectifier-side and inverter-side ripple currents on the bus capacitor ripple current, resulting in high accuracy of the estimated ripple current. It simplifies the ripple current calculation process and is suitable for engineering applications.

[0239] The following estimates the capacitor ripple current of the same type of medium-voltage frequency converter power unit using the same capacitor parameters. Different estimation methods are used, and the estimation results are compared to verify the accuracy and effectiveness of the bus capacitor ripple current estimation method in the embodiments of this application.

[0240] As an example, such as Figures 7 to 9 A simulation model was used to calculate the ripple current in order to verify the accuracy and feasibility of the bus capacitor ripple current estimation method provided in the embodiments of this application.

[0241] In practical engineering design, simulation models of power units are generally built using Matlab / Simlink, such as... Figure 7 As shown, a resistive-inductive load is used to simulate the characteristics of a motor.

[0242] The power simulation parameters are shown in Table 1:

[0243] Table 1:

[0244]

[0245]

[0246] like Figure 8 and Figure 9 As shown, after inputting the parameters from Table 1 above into the simulation software, the simulation results of the bus voltage and ripple current are output. When the capacitor capacity is configured to 8000uF, the bus ripple voltage is 90V, the ripple voltage coefficient is 9.6%, and the effective value of the ripple current is 150.5A. Correspondingly, the ripple current and bus voltage estimated using the estimation method of this application embodiment are in high agreement with the simulation results, verifying the correctness of the capacitor capacity configuration and ripple current calculation formula in this application embodiment.

[0247] As an example, an experimental platform was built using a power unit prototype with a rated power of 144kVA. This platform consists of a voltage-regulating UPS, a step-up transformer, contactors, power units, and an inductive load. The voltage-regulating UPS has a capacity of 200kVA, and the step-up transformer (380V:720V) has a capacity of 250kVA. The inductive load has a resistance of 3Ω and an inductance of 4.27mH. Under a rated input voltage of 690V, the bus voltage waveform of the power unit is as follows: Figure 10 As shown, the ripple current waveform is as follows: Figure 11 As shown, the ripple voltage coefficient is 10.6%, and the effective value of the ripple current of a single capacitor is 74.9A.

[0248] The results of calculation, simulation, and testing were compiled to obtain the comparison results in Table 2:

[0249] Table 2:

[0250] category Ripple voltage coefficient / % Single capacitor ripple current / A Calculated value 10 75 Simulation values 9.6 75.25 Test value 10.6 74.9

[0251] For ripple voltage, the calculation and simulation error accuracy is controlled within 0.4%, and the test error accuracy is controlled within 0.6%; for ripple current, the calculation and simulation error accuracy is controlled within 0.33%, and the test error accuracy is controlled within 0.33%.

[0252] Within 0.13%, the main reasons for the error are: in the embodiments of this application, the influence of high-frequency harmonics on ripple current is ignored for ease of calculation. At the same time, it is assumed that all ripple is absorbed by the bus capacitor, but in reality, some low-frequency harmonics still pass directly through the secondary winding of the phase-shifting transformer; in addition, there will be a deviation between the nominal capacity and the actual capacity of the bus capacitor, generally around 10%; and the theoretical analysis uses mathematical and simulation models under ideal conditions, while the experimental platform and prototype main circuit will have parasitic parameters that affect the test results.

[0253] The above-mentioned errors have little impact on the calculation results of ripple current, which meets the design requirements of products in engineering applications and verifies the effectiveness of capacity configuration and ripple current calculation formula. In other words, the embodiments of this application can be applied to engineering.

[0254] Furthermore, simulation software can only build simulations based on input voltage. It requires configuring corresponding simulation parameters (such as input voltage, equivalent resistance, bus capacitance, inductance, etc.) according to the user's required output effective current value, and then estimating the ripple current corresponding to the bus capacitance through the simulation platform. In contrast, in this embodiment, the ripple current can be directly estimated based on the user's required output effective current value, without the need to convert output parameters into simulation parameters such as input voltage, reducing the parameter conversion (parameter building) process and avoiding conversion errors.

[0255] Figure 12 A schematic diagram of the structure of the bus capacitor ripple current estimation device provided in this application is shown below. Figure 12 As shown, the estimation device 120 provided in this embodiment includes:

[0256] The acquisition module 1201 is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The power unit bus parameters of the medium-voltage frequency converter include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0257] The processing module 1202 is used to process the power unit bus parameters of the medium-voltage frequency converter in order to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency and the bus voltage fluctuation coefficient.

[0258] The processing module 1202 is also used to process the power unit bus parameters and bus capacitor capacity of the medium-voltage frequency converter in order to estimate the ripple current of the bus capacitor based on the bus parameters and bus capacitor capacity.

[0259] The bus capacitor ripple current estimation device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0260] Figure 13 A schematic diagram of the structure of the bus capacitor ripple current estimation device provided in this application is shown below. Figure 13 As shown, the estimation device 130 provided in this embodiment includes:

[0261] The acquisition module 1301 is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio.

[0262] The capacitance estimation module 1302 is used to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency, and the bus voltage fluctuation coefficient.

[0263] The rectifier-side component estimation module 1303 is used to determine the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacity.

[0264] Inverter-side component estimation module 1304 is used to determine the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current.

[0265] The ripple current estimation module 1305 is used to estimate the ripple current of the bus capacitor based on the ripple current components on the rectifier side and the inverter side.

[0266] The bus capacitor ripple current estimation device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0267] Figure 14 A schematic diagram of the structure of the electronic device provided in this application. Figure 14As shown, the electronic device 140 provided in this embodiment includes at least one processor 1401 and a memory 1402. Optionally, the device 140 also includes a communication component 1403. The processor 1401, memory 1402, and communication component 1403 are connected via a bus 1404.

[0268] In a specific implementation, at least one processor 1401 executes computer execution instructions stored in memory 1402, causing at least one processor 1401 to perform the above-described method.

[0269] The specific implementation process of processor 1401 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0270] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0271] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0272] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0273] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0274] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0275] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0276] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0277] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0278] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0279] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0280] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0281] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0282] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for estimating bus capacitor ripple current, characterized in that, include: Obtain the power unit bus parameters of the medium-voltage frequency converter, including the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio; Estimate the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient. Estimate the ripple current of the bus capacitor based on the bus parameters and the bus capacitor capacity.

2. The method according to claim 1, characterized in that, The step of estimating the ripple current of the bus capacitor based on the bus parameters and the bus capacitor capacity includes: Estimate the ripple current of the bus capacitor using the following formula: Where M is the modulation ratio, I o.rms C is the effective value of the output current. bus U is the bus capacitor capacitance. bus,max Here, α is the peak voltage of the bus, and f is the bus voltage fluctuation coefficient. m For the modulation wave frequency, t c For charging time, t d This refers to the discharge time.

3. The method according to claim 1, characterized in that, The step of estimating the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient includes: Estimate the bus capacitor capacity using the following formula: Among them, C bus For the bus capacitor capacity, t d R is the discharge time. load Let α be the equivalent resistance of the load, and α be the bus voltage fluctuation coefficient.

4. The method according to any one of claims 1 to 3, characterized in that, The method further includes: Estimate the charging time of the bus capacitor based on the bus voltage fluctuation coefficient and the angular frequency of the input voltage; Based on the charging time and modulation wave frequency, estimate the discharge time of the bus capacitor; The charging time of the bus capacitor is estimated using the following formula: The discharge time of the bus capacitor can be estimated using the following formula: Among them, t c For charging time, t d Where is the discharge time, α is the bus voltage fluctuation coefficient, and f m The frequency of the modulation wave.

5. A method for estimating bus capacitor ripple current, characterized in that, include: Obtain the power unit bus parameters of the medium-voltage frequency converter, including the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio; Estimate the bus capacitance based on the effective value of the output current, the modulation frequency, and the bus voltage fluctuation coefficient. The rectifier-side ripple current component of the bus capacitor is determined based on the bus capacitor capacity, and the inverter-side ripple current component of the bus capacitor is determined based on the modulation ratio and the effective value of the output current. The ripple current of the bus capacitor is estimated based on the rectifier-side ripple current component and the inverter-side ripple current component.

6. The method according to claim 5, characterized in that, The step of determining the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacity includes: The rectifier-side ripple current component of the bus capacitor is determined based on the bus capacitor capacitance, bus voltage peak value, modulation wave frequency, and the charging and discharging time of the bus capacitor.

7. The method according to claim 6, characterized in that, The step of determining the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacitance, bus voltage peak value, modulation wave frequency, and charging and discharging time of the bus capacitor includes: The peak charging current of the bus capacitor is determined based on the bus capacitor capacity, the modulation wave frequency, and the charging time of the bus capacitor; and the peak discharging current of the bus capacitor is determined based on the bus capacitor capacity, the modulation wave frequency, and the discharging time. The effective charging value of the bus capacitor is determined based on the peak charging current, the charging time, and the modulation wave frequency; and the effective discharging value of the bus capacitor is determined based on the peak discharging current, the discharging time, and the modulation wave frequency. The rectifier-side ripple current component of the bus capacitor is determined based on the effective charging value and the effective discharging value.

8. The method according to claim 5, characterized in that, The step of determining the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current includes: The inverter-side ripple current component is estimated based on the RMS value of the output current and the modulation ratio.

9. The method as described in claim 8, characterized in that, The step of estimating the inverter-side ripple current component based on the effective value of the output current and the modulation ratio includes: The H-bridge input current of the medium-voltage frequency converter power unit is determined based on the effective value of the output current. The inverter-side ripple current component is determined based on the H-bridge input current and the modulation ratio, or the inverter-side ripple current component is determined based on the average value and effective value of the H-bridge input current, wherein the average value is the average value of the H-bridge input current within a period.

10. A device for estimating bus capacitor ripple current, characterized in that, include: The acquisition module is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio. The processing module is used to process the power unit bus parameters of the medium-voltage frequency converter to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency and the bus voltage fluctuation coefficient. The processing module is further configured to process the bus parameters and the bus capacitance to estimate the ripple current of the bus capacitor based on the bus parameters and the bus capacitance.

11. A device for estimating bus capacitor ripple current, characterized in that, include: The acquisition module is used to acquire the power unit bus parameters of the medium-voltage frequency converter. The bus parameters include the effective value of the output current, the modulation wave frequency, the bus voltage fluctuation coefficient, and the modulation ratio. The capacitance estimation module is used to estimate the bus capacitance based on the effective value of the output current, the modulation wave frequency, and the bus voltage fluctuation coefficient. The rectifier-side component estimation module is used to determine the rectifier-side ripple current component of the bus capacitor based on the bus capacitor capacity. The inverter-side component estimation module is used to determine the inverter-side ripple current component of the bus capacitor based on the modulation ratio and the effective value of the output current. The ripple current estimation module is used to estimate the ripple current of the bus capacitor based on the ripple current components on the rectifier side and the ripple current components on the inverter side.

12. An electronic device, characterized in that, include: Memory, processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory, causing the processor to perform the method as described in any one of claims 1-9.

13. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-9.

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