Method and device for determining direct current ripple current, electronic equipment and storage medium

Abstract

The application relates to a direct current ripple current determination method and device, electronic equipment and a storage medium. The method comprises the following steps: firstly, determining a current time step direct current ripple voltage of a converter according to a previous time step direct current ripple current of the converter, current three-phase commutation inductance, current three-phase fundamental wave voltage and fundamental wave angular velocity; then, determining a current time step direct current ripple current according to the previous time step direct current ripple current, the current time step direct current ripple voltage, average impedance of a converter valve and equivalent impedance of a direct current line and a direct current filter in the converter; and if the current time step direct current ripple current and the previous time step direct current ripple current meet a convergence iteration condition, the current time step direct current ripple current is taken as a target direct current ripple current flowing through the converter. Obviously, the method can accurately determine the target direct current ripple current flowing through the converter, and improves the accuracy of target direct current ripple current determination.

Description

Technical Field

[0001] This application relates to the field of digital simulation technology for high-voltage AC / DC power transmission, and in particular to a method, apparatus, electronic device, and storage medium for determining DC ripple current. Background Technology

[0002] Currently, high-voltage direct current (HVDC) transmission is widely used in power transmission projects due to its unique advantages. However, converters in AC / DC transmission systems generate a significant amount of harmonics. To eliminate the impact of harmonics, harmonic filters of a certain capacity are typically installed on the AC bus of the converter. In practical applications, the results of harmonic current calculations directly affect the design scheme of the AC filters; therefore, accurate calculation of the harmonic currents generated by AC / DC transmission systems is particularly important.

[0003] However, in calculating harmonic currents, it is necessary to determine the DC ripple current flowing through the converter, and the accuracy of the determined DC ripple current directly affects the accuracy of the harmonic current calculation. Therefore,

[0004] Improving the accuracy of DC ripple current determination is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] Therefore, it is necessary to provide a method, apparatus, electronic device, computer-readable storage medium, and computer program product for determining DC ripple current that can improve the accuracy of DC ripple current determination, in order to address the above-mentioned technical problems.

[0006] Firstly, this application provides a method for determining DC ripple current. The method includes:

[0007] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0008] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0009] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0010] In one embodiment, the current DC ripple voltage of the converter is determined based on the previous time-step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity, including:

[0011] Based on the target cycle time domain segment corresponding to the current time step in the cycle, determine the three-phase equivalent inductance corresponding to the current three-phase commutation inductance in the target cycle time domain segment, and the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment;

[0012] The DC ripple voltage at the current time step is determined based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage; where the time period type includes the commutation time domain segment and the non-commutation time domain segment.

[0013] In one embodiment, the current DC ripple current is determined based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC lines and DC filters in the converter, including:

[0014] Perform frequency domain decomposition on the current time step DC ripple voltage to obtain the AC decomposed voltage of the DC ripple voltage at at least two harmonics.

[0015] Based on the AC decomposition voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter, determine the sinusoidal AC decomposition current at at least two harmonics.

[0016] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step and the sinusoidal AC decomposition current at at least two harmonics.

[0017] In one embodiment, the method further includes:

[0018] Construct a phase angle remainder function based on the initial phase and fundamental angular velocity of any one of the three phases;

[0019] The cycle is segmented in the time domain based on the phase angle remainder function, commutation trigger angle and commutation overlap angle to obtain at least two candidate cycle time domain segments, and the time period type, inductance equivalence relation and voltage equivalence relation corresponding to each candidate cycle time domain segment are determined.

[0020] Accordingly, based on the target cycle time domain segment corresponding to the current time step, the three-phase equivalent inductance corresponding to the current three-phase commutation inductance in the target cycle time domain segment, and the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment are determined, including:

[0021] Determine the current phase angle remainder value based on the phase angle remainder function;

[0022] Based on the remainder of the current phase angle, determine the target cycle time domain segment corresponding to the current time step in the cycle from at least two candidate cycle time domain segments;

[0023] Based on the current three-phase commutation inductance and the inductance equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent inductance of the current three-phase commutation inductance in the target cycle time domain segment.

[0024] Based on the current three-phase fundamental voltage and the voltage equivalence relationship of the target cycle time domain, determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain.

[0025] In one embodiment, the method further includes:

[0026] If the current DC ripple current at the current time step does not meet the convergence iteration condition with the DC ripple current at the previous time step, then update the DC ripple current at the previous time step based on the current DC ripple current at the current time step, and based on the updated DC ripple current at the previous time step, return to execute the operation of determining the DC ripple voltage at the current time step of the converter based on the DC ripple current at the previous time step of the converter, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0027] In one embodiment, the DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, including:

[0028] If the current difference between the current DC ripple current at the current time step and the DC ripple current at the previous time step is less than or equal to a preset current threshold, then it is determined that the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition.

[0029] Secondly, this application also provides a device for determining DC ripple current. The device includes:

[0030] The voltage determination module is used to determine the current DC ripple voltage of the converter based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage and the fundamental angular velocity.

[0031] The current determination module is used to determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0032] The convergence iteration module is used to take the current DC ripple current as the target DC ripple current flowing through the converter when the current DC ripple current and the previous DC ripple current satisfy the convergence iteration condition.

[0033] Thirdly, this application also provides an electronic device. The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the following steps:

[0034] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0035] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0036] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0037] Fourthly, this application also provides a computer-readable storage medium. This computer-readable storage medium stores a computer program thereon, which, when executed by a processor, performs the following steps:

[0038] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0039] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0040] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0041] Fifthly, this application also provides a computer program product. This computer program product includes a computer program that, when executed by a processor, performs the following steps:

[0042] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0043] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0044] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0045] The aforementioned method, apparatus, electronic device, storage medium, and computer program product for determining DC ripple current firstly determines the current DC ripple voltage of the converter based on the previous time-step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity. Then, based on the previous time-step DC ripple current, the current time-step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC lines and DC filters in the converter, the current time-step DC ripple current is determined. If the current time-step DC ripple current and the previous time-step DC ripple current satisfy the convergence iteration condition, then the current time-step DC ripple current is taken as the target DC ripple current flowing through the converter. Clearly, this application considers the influence of the previous time-step DC ripple current in determining the current time-step DC ripple current, and based on the continuous iteration between the previous and current time-step DC ripple currents, obtains an accurate target DC ripple current flowing through the converter, improving the accuracy of the target DC ripple current determination. Attached Figure Description

[0046] Figure 1 This is an application environment diagram of a method for determining DC ripple current in one embodiment;

[0047] Figure 2 This is a flowchart illustrating a method for determining DC ripple current in one embodiment.

[0048] Figure 3 This is a flowchart illustrating a method for determining DC ripple current in another embodiment;

[0049] Figure 4 This is a flowchart illustrating a method for determining DC ripple current in yet another embodiment;

[0050] Figure 5 This is a flowchart illustrating a method for determining DC ripple current in yet another embodiment;

[0051] Figure 6 This is a structural block diagram of a device for determining DC ripple current in one embodiment;

[0052] Figure 7 This is a structural block diagram of a voltage determination module in one embodiment;

[0053] Figure 8 This is a structural block diagram of a current determination module in one embodiment;

[0054] Figure 9 This is a structural block diagram of a device for determining DC ripple current in another embodiment;

[0055] Figure 10This is a structural block diagram of a device for determining DC ripple current in yet another embodiment;

[0056] Figure 11 This is a diagram of the internal structure of an electronic device in one embodiment. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0058] The method for determining DC ripple current provided in this application embodiment can be applied to, for example, Figure 1 In the application environment shown, in one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows. Figure 1 As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The database stores data for determining DC ripple current. The network interface communicates with external terminals via a network connection. When executed by the processor, the computer program implements a method for determining DC ripple current.

[0059] This application provides a method for determining DC ripple current, such as... Figure 2 As shown, a method for determining DC ripple current is provided, which includes the following steps:

[0060] S202, determine the current DC ripple voltage of the converter based on the previous time step DC ripple current of the converter, the current three-phase commutation inductance, the current three-phase fundamental voltage and fundamental angular velocity.

[0061] In this context, a converter refers to a device that performs AC-DC conversion, consisting of one or more converter bridges. DC ripple current is the ripple current within the DC current, and DC ripple voltage is the ripple voltage within the DC voltage. The DC ripple current of the previous time step refers to the DC ripple current corresponding to the previous time step in the context of the current time step.

[0062] Commutation refers to the process by which current flowing through a converter is transferred from one current path to another during operation, using the opening and closing of converter valves. Commutation inductance refers to the inductance of each of the three phases connected to the converter transformer during operation. The three phases are A, B, and C, and the commutation inductance for each phase is L. A L B L C .

[0063] The current three-phase commutation inductance refers to the commutation inductance corresponding to the current time step, that is, the commutation inductance L corresponding to the current time step A. A B corresponds to the commutation inductance L B C corresponds to the commutation inductance L C .

[0064] The fundamental wave refers to the sinusoidal wave component in a complex periodic oscillation that has the longest period of the oscillation. The frequency corresponding to the longest period is called the fundamental wave frequency, and the angular velocity of this period is called the fundamental wave angular velocity. In this embodiment, a 50Hz sine wave can be used as the fundamental wave, and the corresponding fundamental wave angular velocity can be set as ω.

[0065] The current three-phase fundamental voltage refers to the fundamental voltage value corresponding to each of the three phases at the current time step, where the fundamental voltages corresponding to phases A, B, and C are respectively U. A (t), U B (t), U C (t).

[0066] Optionally, one possible approach is to substitute the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity into a pre-set formula for calculating the current time step DC ripple voltage, and then calculate the current time step DC ripple voltage.

[0067] Another approach is to pre-train a model that performs the task of calculating the DC ripple voltage at the current time step. Input the DC ripple current of the previous time step, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity into the model, and the model can output the DC ripple voltage at the current time step.

[0068] S204. Determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0069] In this embodiment, the average impedance of the converter valve and the equivalent impedance of the DC line and DC filter can be preset. The specific process for setting the average impedance of the converter valve and the equivalent impedance of the DC line and DC filter can be found in existing technology and will not be described in detail here. Assume that the average impedance of the converter valve is preset to X. N The equivalent impedance of a DC line and a DC filter is X. E Considering that during converter operation, the DC ripple current corresponding to the previous time step and the DC ripple voltage corresponding to the current time step will affect the DC ripple current corresponding to the current time step, in this embodiment, the DC ripple current corresponding to the previous time step and the DC ripple voltage corresponding to the current time step can be introduced during the calculation of the DC ripple current corresponding to the current time step, and the calculation can be based on the DC ripple current corresponding to the previous time step, the DC ripple voltage corresponding to the current time step, and the average impedance X of the converter valve. N And the equivalent impedance X of the DC lines and DC filters in the converter. E Determine the DC ripple current at the current time step, which can improve the accuracy of calculating the DC ripple current at the current time step.

[0070] In one optional implementation, firstly, the DC ripple voltage at the current time step is decomposed in the frequency domain to obtain the AC decomposed voltage at at least two harmonics; secondly, based on the AC decomposed voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter, the sinusoidal AC decomposed current at at least two harmonics is determined; then, based on the DC ripple current at the previous time step and the sinusoidal AC decomposed current at at least two harmonics, the DC ripple current at the current time step is determined.

[0071] In practical applications, firstly, the DC ripple voltage U at the current time step can be considered. d (t) Perform frequency domain decomposition, such as Fourier decomposition, to obtain the current time-step DC ripple voltage U. d The AC decomposition voltage of (t) at frequency m, where m is a positive integer not less than 2, and the AC decomposition voltage refers to the DC ripple voltage U. d The voltage amplitude U of the m-th harmonic of (t) d(m) This allows us to use frequency domain decomposition to decompose irregular waveforms into a superposition of regular sinusoidal voltage waveforms with m-fold frequencies, which facilitates the subsequent determination of the DC ripple current at the current time step.

[0072] For example, the current time-step DC ripple voltage U is calculated using the following formula (1). d (t) Perform Fourier decomposition to decompose the irregular waveform into a superposition of regular sinusoidal voltage waveforms with frequencies ranging from 1 to 50 times, thereby obtaining the current time-step DC ripple voltage U. d AC decomposition voltage U of frequency 1-50 harmonics of (t) d(m) .

[0073]

[0074] Among them, U d(0) DC ripple voltage U d DC component of (t), U d(m) DC ripple voltage U d The voltage amplitude at the m-th harmonic of (t) can also be called the DC ripple voltage U. d The AC decomposition voltage of the m-th harmonic of (t), where m is an integer between 1 and 50, ω is the fundamental angular velocity, and θ is the fundamental frequency. d(m) DC ripple voltage U d The initial phase of the voltage at a frequency of m times (t).

[0075] Determine the AC decomposition voltage U at frequency m. d(m) Then, the voltage U can be decomposed based on the m-fold frequency AC decomposition. d(m) The pre-set average impedance X of the converter valve N Equivalent impedance X of DC lines and DC filters E Determine the sinusoidal AC decomposition current at at least two harmonics.

[0076] In practical applications, the sinusoidal AC decomposition current at the m-th harmonic can be obtained using the following formula (2).

[0077]

[0078] Among them, U d(m) The current DC ripple voltage U is d The AC decomposition voltage of the m-th harmonic of (t), θ d(m) DC ripple voltage U d The initial phase of the voltage at its m-th harmonic (t), where j represents the imaginary unit, X N X is the average impedance of the converter valve. E The equivalent impedance of the DC line and DC filter, where m is an integer between 1 and 50, and I d(m) Let θ be the amplitude of the m-fold frequency DC ripple current. id(m) The initial phase of the m-fold frequency DC ripple current is given. The current is the sinusoidal alternating current at frequency m.

[0079] In this embodiment, based on the m-fold frequency DC ripple current amplitude corresponding to the previous time step DC ripple current, the m-fold frequency AC decomposition voltage corresponding to the current time step DC ripple voltage, and the average impedance X of the converter valve... N And the equivalent impedance X of the DC lines and DC filters in the converter. EThis allows for precise determination of the DC ripple current at the current time step, thereby improving the accuracy of calculating the DC ripple current at the current time step.

[0080] Obtain the sinusoidal alternating current at the m-th harmonic frequency. Then, the DC ripple current corresponding to the current time step can be determined based on the DC ripple current corresponding to the previous time step and the sinusoidal AC decomposition current at at least two harmonics.

[0081] For example, the m-fold frequency DC ripple current amplitude I can be calculated based on the DC ripple current corresponding to the previous time step. d(m) The initial phase θ of the m-fold frequency-multiplied DC ripple current id(m) The DC ripple current I corresponding to the current time step is obtained using the following formula (3). d (t).

[0082]

[0083] Among them, I d The DC ripple current corresponding to the previous time step, I d(m) Let θ be the amplitude of the m-fold frequency DC ripple current. id(m) ω is the initial phase of the m-fold frequency DC ripple current, ω is the fundamental angular velocity, and m is an integer between 1 and 50.

[0084] S206 If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0085] In this embodiment, a preset current threshold can be set in advance, and the current difference between the current step DC ripple current and the previous step DC ripple current can be compared with the preset current threshold. If the current difference between the current step DC ripple current and the previous step DC ripple current is less than or equal to the preset current threshold, it is determined that the current step DC ripple current and the previous step DC ripple current meet the convergence iteration condition, and then the current step DC ripple current is taken as the target DC ripple current flowing through the converter.

[0086] For example, assuming a preset current threshold of δ, after multiple iterations to converge the calculation of the current time step DC ripple voltage and current time step DC ripple current, the corresponding DC ripple current I at the current time step... d (t) and the DC ripple current I corresponding to the previous time step d Satisfying the convergence iteration condition |I d (t)-I d If |≤δ, then the iteration convergence is determined to be over. The DC ripple current calculated at the current time step is taken as the target DC ripple current flowing through the converter. This allows for accurate determination of the target DC ripple current.

[0087] In one embodiment, if the current DC ripple current at the current time step does not meet the convergence iteration condition with the DC ripple current at the previous time step, that is, the current difference between the current DC ripple current at the current time step and the DC ripple current at the previous time step is greater than a preset current threshold, then the DC ripple current at the previous time step is updated according to the current DC ripple current, and the DC ripple current at the current time step is updated according to the next DC ripple current. Then, based on the updated DC ripple current at the previous time step and the DC ripple current at the current time step, the operation of determining the DC ripple voltage at the current time step of the converter based on the DC ripple current at the previous time step of the converter, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity is returned.

[0088] In other words, assuming the DC ripple current I corresponding to the current time step d (t) and the DC ripple current I corresponding to the previous time step d The convergence iteration condition is not met, i.e., |I d (t)-I d If |>δ, then the DC ripple current I corresponding to the current time step will be... d The value of (t) is assigned to the DC ripple current I corresponding to the previous time step. d , that is I d 0 (t)=I d Then, the next iteration of convergence calculation is performed. Based on the updated DC ripple current corresponding to the previous time step, the process can return to continue executing the operation of determining the DC ripple voltage corresponding to the current time step of the converter based on the DC ripple current of the converter in the previous time step, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity. This process is repeated multiple times to convergence calculate the current time step DC ripple voltage and current time step until it is determined that the current time step DC ripple current and the previous time step DC ripple current satisfy the convergence iteration condition. Only then is the current time step DC ripple current used as the target DC ripple current flowing through the converter. This allows for precise determination of the target DC ripple current flowing through the converter, improving the accuracy of the target DC ripple current determination.

[0089] Obviously, in the method for determining the DC ripple current described above in this application, considering the instantaneous coupling characteristics of DC ripple voltage and DC ripple current, firstly, since the DC ripple current corresponding to the previous time step will affect the DC ripple voltage corresponding to the current time step, the DC ripple voltage corresponding to the current time step can be determined based on the DC ripple current corresponding to the previous time step; then, since the DC ripple current corresponding to the previous time step and the DC ripple voltage corresponding to the current time step will affect the DC ripple current corresponding to the current time step, the DC ripple current corresponding to the current time step can be determined based on the DC ripple current corresponding to the previous time step and the DC ripple voltage corresponding to the current time step. Furthermore, after multiple iterative convergence calculations of the DC ripple voltage and current time step, until it is determined that the DC ripple current of the current time step and the DC ripple current of the previous time step satisfy the convergence iteration condition, the DC ripple current of the current time step is taken as the target DC ripple current flowing through the converter. This allows for accurate determination of the target DC ripple current flowing through the converter, improving the accuracy of the target DC ripple current determination.

[0090] Based on the above embodiments, such as Figure 3 As shown, this application also provides another method for determining DC ripple current, which can accurately determine the DC ripple voltage corresponding to the current time step. This method includes the following steps:

[0091] S302, based on the target cycle time domain segment corresponding to the current time step in the cycle, determine the three-phase equivalent inductance corresponding to the current three-phase commutation inductance in the target cycle time domain segment, and the three-phase equivalent voltage corresponding to the current three-phase fundamental voltage in the target cycle time domain segment.

[0092] In this embodiment, considering the influence of non-ideal factors such as commutation inductance imbalance and unequal commutation trigger angles, the cycle can be segmented in the time domain into multiple regions. Each region has a corresponding cycle time domain segment. The target cycle time domain segment can be any one of multiple cycle time domain segments. Each cycle time domain segment has a corresponding commutation correspondence, which includes a one-to-one correspondence between phases A, B, and C and phases P (about to enter commutation), Q (about to exit commutation), and R (not participating in commutation). Assuming the current time step corresponds to a switch from phase C to phase B, then phase P corresponds to phase B, phase Q corresponds to phase C, and phase R corresponds to phase A. Correspondingly, L... P With L B Corresponding, L Q With L C Corresponding, L R With L A Corresponding to, i.e., L P The corresponding value is L B L Q The corresponding value is L C L RThe corresponding value is L A U P (t) and U B (t) corresponds to, U Q (t) and U C (t) corresponds to, U R (t) and U A (t) corresponds to, i.e., U P The value corresponding to (t) is U. B (t), U Q The value corresponding to (t) is U. C (t), U R The value corresponding to (t) is U. A (t).

[0093] In practical applications, firstly, the target cycle time domain segment corresponding to the current time step can be determined. Then, based on this target cycle time domain segment, the corresponding commutation relationship can be determined. Finally, based on the commutation relationship corresponding to the target cycle time domain segment, the current three-phase commutation inductance L can be used to determine the commutation relationship. A L B L C The corresponding commutation relationship with the target frequency time domain segment is used to determine the three-phase equivalent inductance L corresponding to the target frequency time domain segment. Ri(t) (t), L Pi(t) (t), L Qi(t) (t), or can be based on the current three-phase fundamental voltage U A (t), U B (t), U C (t) and the corresponding relationship with the target cycle time domain segment are used to determine the three-phase equivalent voltage U corresponding to the target cycle time domain segment. Ri(t) (t), U Pi(t) (t), U Qi(t) (t).

[0094] S304. Determine the DC ripple voltage of the current time step based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage; wherein, the time period type includes the commutation time domain segment and the non-commutation time domain segment.

[0095] Determine the three-phase equivalent inductance L corresponding to the target frequency time domain segment. Ri(t) (t), L Pi(t) (t), L Qi(t) (t) and the three-phase equivalent voltage U Ri(t) (t), U Pi(t) (t), U Qi(t)After (t), the DC ripple voltage of the current time step can be determined based on the time period type of the target cycle time domain segment, the three-phase equivalent inductance, the three-phase equivalent voltage, and the DC ripple current of the previous time step. The time period type includes commutation time domain segment and non-commutation time domain segment. Different time period types correspond to different ways of determining the DC ripple voltage of the current time step.

[0096] In practical applications, it can be determined whether the target cycle time domain segment i(t) corresponding to the current time step belongs to the commutation time domain segment. If i(t) belongs to the commutation time domain segment, the DC ripple voltage U corresponding to the current time step is determined by the following formula (4). d (t).

[0097]

[0098] Where i(t) is the cycle time domain segment, L Ri(t) (t), L Pi(t) (t), L Qi(t) (t) represents the current three-phase commutation inductance L. A L B L C The corresponding three-phase equivalent inductance, U Ri(t) (t), U Pi(t) (t), U Qi(t) (t) represents the current three-phase fundamental voltage U. A (t), U B (t), U C (t) represents the three-phase equivalent voltage, where ω is the fundamental angular velocity. This is the DC ripple current corresponding to the previous time step, where,

[0099] If the target cycle time domain segment i(t) corresponding to the current time step belongs to the non-commutation time domain segment, then the DC ripple voltage U corresponding to the current time step is determined by the following formula (5). d (t).

[0100]

[0101] Where i(t) is the cycle time domain segment, U Pi(t) (t), U Qi(t) (t) represents the current three-phase fundamental voltage U A (t), U B (t), U C The two voltages in (t) correspond to the equivalent voltages, and ω is the fundamental angular velocity. U is the DC ripple current corresponding to the previous time step. d (t) represents the DC ripple voltage corresponding to the current time step.

[0102] S306. Determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0103] S308 If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0104] The descriptions of S306-S308 can be understood by referring to S204-S206 above, and will not be repeated here.

[0105] In this embodiment, considering the influence of non-ideal factors such as commutation inductance imbalance and unequal commutation trigger angles, the cycle can be segmented in the time domain, and the three-phase equivalent inductance and three-phase equivalent voltage corresponding to the target cycle time domain segment can be determined. Considering the influence of the DC ripple current of the previous time step on the DC ripple voltage of the current time step, the DC ripple voltage corresponding to the current time step can be accurately determined based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage, thus improving the accuracy of determining the DC ripple voltage of the current time step.

[0106] Based on the above embodiments, in order to understand the process of accurately determining the DC ripple voltage at the current time step, such as... Figure 4 As shown, this application also provides another method for determining DC ripple current, which includes the following steps:

[0107] S402, construct the phase angle remainder function based on the initial phase and fundamental angular velocity of any one of the three phases.

[0108] Assume that the initial phase θ corresponding to A in the three phases A Then the initial phase corresponding to B is θ B =θ A -2π / 3, the initial phase corresponding to C is θ C =θ A +2π / 3. In this embodiment, the phase angle remainder function can be constructed based on any one of phases A, B, and C. Assuming the phase angle remainder function is determined by phase A, it can be calculated based on ωt+θ. A The phase angle remainder function is obtained by taking the remainder of 2π, and the expression of the phase angle remainder function is shown in formula (6) below.

[0109] y w =rem((ωt+θ) A ) / (2π)) (6)

[0110] Where rem(·) is the remainder sign, ω is the fundamental angular velocity, and θA This is the initial phase corresponding to A.

[0111] In practical applications, the method of determining the phase angle remainder function through phase B or phase C is similar to the method of determining the phase angle remainder function through phase A, and will not be elaborated further here.

[0112] S404 divides the cycle into time domain segments based on the phase angle remainder function, commutation trigger angle and commutation overlap angle to obtain at least two candidate cycle time domain segments, and determines the time period type, inductance equivalence relation and voltage equivalence relation corresponding to each candidate cycle time domain segment.

[0113] In one optional implementation, considering the influence of non-ideal factors such as commutation inductance imbalance and unequal commutation trigger angles, after determining the phase angle remainder function, the cycle can be segmented in the time domain according to the phase angle remainder function, the commutation trigger angle, and the commutation overlap angle to obtain at least two candidate cycle time domain segments. Each candidate cycle time domain segment can correspond to a commutation time domain segment or a non-commutation time domain segment, and each candidate cycle time domain segment has a corresponding commutation correspondence. Based on the candidate cycle time domain segments and the commutation correspondence, the inductance equivalence relationship and voltage equivalence relationship corresponding to each candidate cycle time domain segment can be determined. The inductance equivalence relationship refers to the three-phase commutation inductance L... A L B L C The three-phase equivalent inductance L corresponding to each cycle time domain segment P L Q L R The correspondence between them, the voltage equivalence relationship refers to the three-phase fundamental voltage U A (t), U B (t), U C (t) and the three-phase equivalent voltage U corresponding to each cycle time domain segment P (t), U Q (t), U R The correspondence between (t).

[0114] For example, assuming the commutation trigger angles are set to α1, α2, α3, α4, α5, α6, and the commutation overlap angles are set to μ1, μ2, μ3, μ4, μ5, μ6, the cycle can be segmented in the time domain based on the phase angle remainder function, the commutation trigger angles, and the commutation overlap angles, resulting in a time-domain segmentation table, as shown in Table 1. Table 1 shows 12 regions, each corresponding to a specific cycle time domain segment, and the corresponding commutation relationship. The 12 regions include: π / 6 + α1 + μ1 > y w ≥π / 6+α1、π / 2+α2>y w ≥π / 6+α1+μ1、...y w≥11π / 6+α6+μ6, where these 12 regions correspond to 6 pulse sequences, which correspond to 12 cycle time domain segments i(t), where i(t) can be either commutated or non-commutated time domain segments. Table 1 also shows P i(t) Phase, R i(t) Phase, Q i(t) The phase-to-phase correspondence between phase A, phase B, and phase C.

[0115] Table 1 shows the time-domain segmentation table.

[0116]

[0117] In practical applications, the cycle time domain segment i(t) shown in Table 1, and the corresponding P of the cycle time domain segment can be used as a reference. i(t) Phase, R i(t) Phase, Q i(t) The commutation correspondence between phases A, B, and C is used to determine the three-phase commutation inductance L corresponding to each cycle time domain segment. A L B L C The three-phase equivalent inductance L corresponding to each candidate cycle time domain segment P L Q L R The correspondence between them, and the three-phase fundamental voltage U corresponding to the cycle time domain segment. A (t), U B (t), U C (t) and the three-phase equivalent voltage U corresponding to the candidate cycle time domain segment P (t), U Q (t), U R The correspondence between (t).

[0118] S406, determine the current phase angle remainder value based on the phase angle remainder function.

[0119] S408, based on the remainder of the current phase angle, determine the target cycle time domain segment corresponding to the current time step in the cycle from at least two candidate cycle time domain segments.

[0120] In determining the DC ripple voltage at the current time step, the current phase angle remainder value can be determined first based on the phase angle remainder function mentioned above. Then, based on the current phase angle remainder value, the target cycle time domain segment corresponding to the current time step can be determined from the 12 candidate cycle time domain segments in Table 1 above.

[0121] S410, based on the current three-phase commutation inductance and the inductance equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent inductance corresponding to the current three-phase commutation inductance in the target cycle time domain segment.

[0122] S412, based on the current three-phase fundamental voltage and the voltage equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment.

[0123] Optionally, the commutation correspondence of the target cycle time domain segment can be determined based on the target cycle time domain segment corresponding to the current time step. Based on the target cycle time domain segment i(t) corresponding to the current time step, and the commutation correspondence between phases P, Q, and R and phases A, B, and C at the current time step, the three-phase equivalent inductance L corresponding to the target cycle time domain segment can be determined. Ri(t) (t), L Pi(t) (t), L Qi(t) (t) and the current three-phase commutation inductance L A L B L C The inductance equivalence relation, and the three-phase equivalent voltage U of the target cycle time domain. Ri(t) (t), U Pi(t) (t), U Qi(t) (t) and the current three-phase fundamental voltage U A (t), U B (t), U C The voltage equivalence relation of (t) is used to determine the three-phase equivalent inductance L corresponding to the target cycle time domain segment. Ri(t) (t), L Pi(t) (t), L Qi(t) (t), and based on the voltage equivalence relation, determine the three-phase equivalent voltage U of the target cycle time domain segment. Ri(t) (t), U Pi(t) (t), U Qi(t) (t).

[0124] As shown in Table 1, assuming the target cycle time domain segment corresponding to the current time step is i(t) = 3, then phase P corresponds to B, phase Q corresponds to C, phase R corresponds to A, and correspondingly, L... P With L B Corresponding, L Q With L C Corresponding, L R With L A Corresponding to, i.e., L P The corresponding value is L B L Q The corresponding value is L C L R The corresponding value is L A U P (t) and U B (t) corresponds to, U Q (t) and U C (t) corresponds to, U R (t) and UA (t) corresponds to, i.e., U P The value corresponding to (t) is U. B (t), U Q The value corresponding to (t) is U. C (t), U R The value corresponding to (t) is U. A (t).

[0125] S414. Determine the DC ripple voltage of the current time step based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage; wherein, the time period type includes the commutation time domain segment and the non-commutation time domain segment.

[0126] S416: Determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0127] S418 If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0128] The descriptions of S414-S418 can be understood by referring to S304-S308 above, and will not be repeated here.

[0129] In this embodiment, considering the influence of non-ideal factors such as commutation inductance imbalance and unequal commutation trigger angles, the cycle can be segmented in the time domain, and the three-phase equivalent inductance and three-phase equivalent voltage corresponding to the target cycle time domain segment can be determined. Considering the influence of the DC ripple current of the previous time step on the DC ripple voltage of the current time step, the DC ripple voltage of the current time step can be accurately determined based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage, thus improving the accuracy of determining the DC ripple voltage of the current time step.

[0130] Based on the above embodiments, this application also provides another method for determining DC ripple current, which can accurately determine the DC ripple voltage at the current time step, and accurately determine the DC ripple current corresponding to the current time step based on the DC ripple voltage at the current time step. For example... Figure 5 As shown, the method includes the following steps:

[0131] S502, construct the phase angle remainder function based on the initial phase and fundamental angular velocity of any one of the three phases.

[0132] S504 divides the cycle into time domain segments based on the phase angle remainder function, commutation trigger angle and commutation overlap angle to obtain at least two candidate cycle time domain segments, and determines the time period type, inductance equivalence relation and voltage equivalence relation corresponding to each candidate cycle time domain segment.

[0133] S506, determine the current phase angle remainder value based on the phase angle remainder function.

[0134] S508, based on the remainder of the current phase angle, determine the target cycle time domain segment corresponding to the current time step in the cycle from at least two candidate cycle time domain segments.

[0135] S510, based on the current three-phase commutation inductance and the inductance equivalence relationship of the target cycle time domain segment, determines the three-phase equivalent inductance corresponding to the current three-phase commutation inductance in the target cycle time domain segment.

[0136] S512, based on the current three-phase fundamental voltage and the voltage equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment.

[0137] S514 determines the current DC ripple voltage of the converter based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0138] S516 performs frequency domain decomposition on the current time step DC ripple voltage to obtain the AC decomposed voltage of the DC ripple voltage at at least two harmonics.

[0139] S518, based on the AC decomposition voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter, determine the sinusoidal AC decomposition current at at least two harmonics.

[0140] S520 determines the current DC ripple current based on the previous time step DC ripple current and the sinusoidal AC decomposition current at at least two harmonics.

[0141] S522, determine whether the DC ripple current of the current time step and the DC ripple current of the previous time step meet the convergence iteration condition. If not, execute S524; if yes, execute S526.

[0142] The convergence iteration condition is that the current difference between the DC ripple current of the current step and the DC ripple current of the previous step is less than or equal to a preset current threshold.

[0143] S524, if not, update the DC ripple current of the previous time step based on the current time step DC ripple current, update the current time step DC ripple current based on the next DC ripple current, and return to execute the operation of determining the current time step DC ripple voltage of the converter based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage and the fundamental angular velocity, based on the updated previous time step DC ripple current and the current time step DC ripple current.

[0144] S526, if so, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0145] The DC ripple current determination method provided in this application can accurately determine the target DC ripple current flowing through the converter. Furthermore, based on the target DC ripple current, harmonic currents under various factors in the HVDC transmission system can be calculated, improving the accuracy of harmonic current calculations in HVDC transmission systems. This provides important technical support for harmonic current calculations in HVDC transmission systems and, consequently, important basis for the design of AC filters in HVDC transmission systems. In addition, this application effectively solves the problems of low margin and easy damage of AC filters in actual power transmission processes, ensuring the safe operation of HVDC transmission systems while minimizing filter investment costs, and has excellent application prospects.

[0146] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0147] Based on the same inventive concept, this application also provides a DC ripple current determination device for implementing the DC ripple current determination method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more embodiments of the DC ripple current determination device provided below can be found in the limitations of the DC ripple current determination method described above, and will not be repeated here.

[0148] In one embodiment, such as Figure 6As shown, a device 1 for determining DC ripple current is provided, comprising: a voltage determination module 10, a current determination module 20, and a convergence iteration module 30, wherein:

[0149] The voltage determination module 10 is used to determine the current DC ripple voltage of the converter based on the previous time step DC ripple current of the converter, the current three-phase commutation inductance, the current three-phase fundamental voltage and the fundamental angular velocity.

[0150] The current determination module 20 is used to determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0151] The convergence iteration module 30 is used to take the current DC ripple current as the target DC ripple current flowing through the converter when the current DC ripple current and the previous DC ripple current satisfy the convergence iteration condition.

[0152] In one embodiment, such as Figure 7 As shown, above Figure 6 The voltage determination module 10 includes:

[0153] The first determining unit 101 is used to determine the three-phase equivalent inductance of the current three-phase commutation inductance in the target cycle time domain segment, and the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment, based on the target cycle time domain segment corresponding to the current time step in the cycle.

[0154] The second determining unit 102 is used to determine the current DC ripple voltage based on the DC ripple current of the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage; wherein, the time period type includes the commutation time domain segment and the non-commutation time domain segment.

[0155] In one embodiment, such as Figure 8 As shown, above Figure 6 The current determination module 20 includes:

[0156] AC decomposition voltage unit 201 is used to perform frequency domain decomposition on the current time step DC ripple voltage to obtain the AC decomposition voltage of the DC ripple voltage at at least two harmonics.

[0157] The sinusoidal AC decomposition current unit 202 is used to determine the sinusoidal AC decomposition current at at least two harmonics based on the AC decomposition voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0158] The third determining unit 203 is used to determine the current DC ripple current based on the DC ripple current of the previous time step and the sinusoidal AC decomposition current at at least two harmonics.

[0159] In one embodiment, in the above Figure 6 or Figure 7 Based on at least one of them, such as Figure 9 As shown, the device also includes:

[0160] The function module 40 is used to construct the phase angle remainder function based on the initial phase and fundamental angular velocity of any one of the three phases.

[0161] The time-domain segmentation module 50 is used to segment the cycle in the time domain according to the phase angle remainder function, commutation trigger angle and commutation overlap angle, to obtain at least two candidate cycle time domain segments, and to determine the time period type, inductance equivalence relationship and voltage equivalence relationship corresponding to each candidate cycle time domain segment;

[0162] Accordingly, the first determining unit 101 includes:

[0163] The remainder subunit 1011 is used to determine the current phase angle remainder value based on the phase angle remainder function;

[0164] Time-domain subunit 1012 is used to determine the target cycle time-domain segment corresponding to the current time step in the cycle from at least two candidate cycle time-domain segments based on the remainder of the current phase angle.

[0165] The inductor subunit 1013 is used to determine the three-phase equivalent inductance of the current three-phase commutation inductance in the target frequency time domain segment based on the current three-phase commutation inductance and the inductance equivalence relationship of the target frequency time domain segment.

[0166] The voltage subunit 1014 is used to determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain based on the current three-phase fundamental voltage and the voltage equivalence relationship of the target cycle time domain segment.

[0167] In one embodiment, in the above Figures 6 to 9 Based on any one of them, such as Figure 10 As shown, the device also includes:

[0168] The current update module 60 is used to update the DC ripple current of the previous time step according to the current time step DC ripple current when the current time step DC ripple current and the previous time step DC ripple current do not meet the convergence iteration condition, update the current time step DC ripple current according to the next DC ripple current, and return to execute the operation of determining the current time step DC ripple voltage of the converter according to the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage and the fundamental angular velocity.

[0169] It should be noted that, Figure 10 The structure shown is in Figure 6 This is an illustration based on [the previous sentence], but it can also be based on [the previous sentence]. Figure 7 , Figure 8 or Figure 9 This is an illustration based on the above, and this embodiment does not limit the scope of the example.

[0170] In one embodiment, the convergence iteration module 30 is specifically used to: determine that the current ripple current of the current time step and the DC ripple current of the previous time step satisfy the convergence iteration condition when the current difference between the current ripple current of the current time step and the DC ripple current of the previous time step is less than or equal to a preset current threshold.

[0171] Each module in the aforementioned DC ripple current determination device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of the electronic device in hardware form or independent of it, or stored in the memory of the electronic device in software form, so that the processor can call and execute the operations corresponding to each module.

[0172] In one embodiment, an electronic device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 11 As shown, the electronic device includes a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a method for determining DC ripple current.

[0173] Those skilled in the art will understand that Figure 11The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the electronic device to which the present application is applied. The specific electronic device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0174] In one embodiment, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0175] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0176] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0177] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0178] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0179] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0180] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0181] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0182] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, performs the following steps:

[0183] The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity.

[0184] The DC ripple current at the current time step is determined based on the DC ripple current at the previous time step, the DC ripple voltage at the current time step, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter.

[0185] If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

[0186] It should be noted that the data involved in this application (including but not limited to data used for analysis, stored data, and displayed data) are all information and data authorized by the user or fully authorized by all parties.

[0187] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0188] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0189] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for determining DC ripple current, characterized in that, The method includes: Construct a phase angle remainder function based on the initial phase and fundamental angular velocity of any one of the three phases of the converter. The cycle is segmented in the time domain according to the phase angle remainder function, commutation trigger angle and commutation overlap angle to obtain at least two candidate cycle time domain segments, and the time period type, inductance equivalence relation and voltage equivalence relation corresponding to each candidate cycle time domain segment are determined. The current phase angle remainder value is determined based on the phase angle remainder function. Based on the remainder value of the current phase angle, determine the target cycle time domain segment corresponding to the current time step of the converter in the cycle from the at least two candidate cycle time domain segments; Based on the current three-phase commutation inductance of the converter and the inductance equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent inductance of the current three-phase commutation inductance in the target cycle time domain segment; Based on the current three-phase fundamental voltage of the converter and the voltage equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment; The current DC ripple voltage of the converter is determined based on the previous time step DC ripple current of the converter, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage; wherein, the time period type includes commutation time domain segment and non-commutation time domain segment; The current DC ripple current is determined based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter. If the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition, then the current DC ripple current at the current time step is taken as the target DC ripple current flowing through the converter.

2. The method according to claim 1, characterized in that, The step of determining the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC lines and DC filters in the converter includes: The DC ripple voltage at the current time step is decomposed in the frequency domain to obtain the AC decomposed voltage of the DC ripple voltage at at least two harmonics. The sinusoidal AC decomposition current at at least two harmonics is determined based on the AC decomposition voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter. The current DC ripple current is determined based on the previous time step DC ripple current and the sinusoidal AC decomposition current at at least two harmonics.

3. The method according to claim 2, characterized in that, The step of performing frequency domain decomposition on the current time-step DC ripple voltage to obtain the AC decomposed voltage of the DC ripple voltage at at least two harmonics includes: Perform Fourier decomposition on the current time step DC ripple voltage to obtain the AC decomposed voltage of the DC ripple voltage at at least two harmonics.

4. The method according to claim 1, characterized in that, The method further includes: If the current DC ripple current at the current time step does not meet the convergence iteration condition with the previous DC ripple current at the previous time step, then the previous DC ripple current at the current time step is updated according to the current DC ripple current at the previous time step, and the operation of determining the current DC ripple voltage of the converter based on the previous DC ripple current of the converter, the current three-phase commutation inductance, the current three-phase fundamental voltage, and the fundamental angular velocity is returned to be executed according to the updated previous DC ripple current of the converter.

5. The method according to claim 1, characterized in that, The current DC ripple current at the current time step and the previous DC ripple current at the previous time step satisfy the convergence iteration condition, including: If the current difference between the current DC ripple current at the current time step and the DC ripple current at the previous time step is less than or equal to a preset current threshold, then it is determined that the current DC ripple current at the current time step and the DC ripple current at the previous time step satisfy the convergence iteration condition.

6. A device for determining DC ripple current, characterized in that, The device includes: The voltage determination module is used to construct a phase angle remainder function based on the initial phase and fundamental angular velocity of any corresponding phase of the three phases of the converter; to perform time-domain segmentation of the cycle based on the phase angle remainder function, commutation trigger angle, and commutation overlap angle to obtain at least two candidate cycle time-domain segments, and to determine the time period type, inductance equivalence relation, and voltage equivalence relation corresponding to each candidate cycle time-domain segment; to determine the current phase angle remainder value based on the phase angle remainder function; to determine the target cycle time-domain segment corresponding to the current time step of the converter in the cycle from the at least two candidate cycle time-domain segments based on the current phase angle remainder value; and to determine the target cycle time-domain segment corresponding to the current time step of the converter in the cycle based on the current three-phase commutation current of the converter. Based on the inductance and the inductance equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent inductance of the current three-phase commutation inductance in the target cycle time domain segment; based on the current three-phase fundamental voltage of the converter and the voltage equivalence relationship of the target cycle time domain segment, determine the three-phase equivalent voltage of the current three-phase fundamental voltage in the target cycle time domain segment; based on the DC ripple current of the converter in the previous time step, the time period type of the target cycle time domain segment, the three-phase equivalent inductance, and the three-phase equivalent voltage, determine the DC ripple voltage of the converter in the current time step; wherein, the time period type includes commutation time domain segment and non-commutation time domain segment; The current determination module is used to determine the current DC ripple current based on the previous time step DC ripple current, the current time step DC ripple voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter. The convergence iteration module is used to take the current DC ripple current as the target DC ripple current flowing through the converter when the current DC ripple current and the previous DC ripple current satisfy the convergence iteration condition.

7. The apparatus according to claim 6, characterized in that, The current determination module includes: An AC decomposition voltage unit is used to perform frequency domain decomposition on the current time step DC ripple voltage to obtain the AC decomposition voltage of the DC ripple voltage at at least two harmonics. A sinusoidal AC decomposition current unit is used to determine the sinusoidal AC decomposition current at at least two harmonics based on the AC decomposition voltage, the average impedance of the converter valve, and the equivalent impedance of the DC line and DC filter in the converter. The third determining unit is used to determine the current time step DC ripple current based on the previous time step DC ripple current and the sinusoidal AC decomposition current at at least two harmonics.

8. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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