Active filtering method and system for low-voltage direct-current power supply system based on proportional repetitive control

Abstract

The invention relates to the technical field of low-voltage direct-current power supply, and discloses a low-voltage direct-current power supply system active filtering method and system based on proportional repetitive control. A cooperative control framework of a proportional repetitive controller and gain scheduling proportional control is introduced, and periodic ripple signals are repeatedly learned and compensated; accurate tracking and suppression of ripple alternating quantities of different frequencies are achieved, the dynamic response speed and the steady-state control precision of ripple compensation are greatly improved, and meanwhile, compared with the defect that complex control parameters need to be designed for the alternating quantities of different frequencies through proportional resonance control, the control method has the advantage that the control precision is improved. According to the proportional repetitive controller, ripple alternating current quantities of different frequencies can be controlled only through one set of control parameters, a parameter calculation method is simple, in addition, gain scheduling proportional control is applied to a current inner loop, a proportionality coefficient can be adjusted according to the magnitude of the direct current bus voltage, and the control precision is improved. The system is kept stable and not easy to oscillate at low pressure, and the response speed of the system is improved at high pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage direct current (DC) power supply, and in particular to an active filtering method and system for a low-voltage DC power supply system based on proportional repetitive control. Background Art

[0002] "Solar-storage-direct-flexible" buildings are a key path to achieving zero-carbon operation. Low-voltage DC power supply systems, with their advantages of fewer power conversion steps, low line losses, and high power quality, have become the core infrastructure for such buildings. However, in residential buildings, sensitive electronic equipment (such as data center servers) and emergency power systems place extremely high demands on DC bus voltage quality. Single-phase / three-phase AC loads and nonlinear loads connected to the system introduce ripple on the DC bus, leading to voltage distortion and deteriorating power quality. Therefore, this ripple problem urgently needs to be addressed.

[0003] Existing ripple control solutions are primarily categorized as passive filtering and active filtering. Passive filters utilize a combination of inductors, capacitors, and resistors to create a low-impedance shunt path for specific sub-ripples. While they offer advantages such as simple structure and low cost, they suffer from significant drawbacks: First, they can only filter out ripple within a preset frequency band and cannot dynamically adapt to spectrum changes; second, the filtering effect is easily affected by grid impedance and load characteristics; and third, the size and weight of the components required for low-frequency ripple increase significantly. In contrast, active filters utilize power electronics circuits and control algorithms to generate dynamic compensation signals, suppressing ripples with varying frequency and amplitude. Their performance is unaffected by system impedance, making them more suitable for low-voltage DC power supply scenarios with uncertain disturbance sources.

[0004] Currently, existing DC active filter solutions often use proportional-integral control or proportional resonant control strategies to track ripple. However, PI control strategies are ineffective at tracking AC quantities. PR control strategies require designing specific control parameters for each AC quantity of varying frequencies, and for mid- and high-frequency ripple control, additional parameters such as damping and phase compensation are added to maintain system stability. This makes the control parameter settings for PR controllers extremely complex. Summary of the Invention

[0005] The present invention provides a method and system for active filtering of a low-voltage DC power supply system based on proportional repetitive control, which solves the technical problem that the proportional-integral control strategy adopted in existing DC active filtering schemes has poor tracking effect on AC quantities, while the proportional resonant control strategy requires designing corresponding control parameters for each AC quantity of different frequencies, which leads to extremely complex control parameter settings.

[0006] A first aspect of the present invention provides an active filtering method for a low-voltage DC power supply system based on proportional repetitive control, which is applied to a three-level parallel DC power supply system, comprising:

[0007] Obtaining a DC bus voltage, a compensation voltage, and an inductor current corresponding to the three-level parallel DC power supply system;

[0008] Determining a DC bus voltage ripple based on the DC bus voltage;

[0009] When the DC bus voltage ripple is not equal to the preset ripple value, determining a first current command value based on a proportional repetitive controller by using the DC bus voltage ripple and a preset ripple standard value;

[0010] Using the compensation voltage and a preset reference voltage to control the compensation capacitor voltage to obtain a second current command value;

[0011] Performing gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a switch duty cycle;

[0012] Based on the duty cycle of the switch tube, a target compensation current is generated by modulating the power device switch module of the three-level parallel DC power supply system, and ripple cancellation is performed.

[0013] Optionally, determining a DC bus voltage ripple based on the DC bus voltage includes:

[0014] Performing a multiplication operation on the DC bus voltage and a preset low-pass filter transfer function to obtain a filtered voltage;

[0015] A difference operation is performed between the DC bus voltage and the filtered voltage to obtain a DC bus voltage ripple.

[0016] Optionally, when the DC bus voltage ripple is not equal to a preset ripple value, determining the first current command value based on a proportional repetitive controller by using the DC bus voltage ripple and a preset ripple standard value includes:

[0017] When the DC bus voltage ripple is not equal to the preset ripple value, performing a difference operation between the DC bus voltage ripple and the preset ripple standard value to obtain a first voltage;

[0018] The first voltage input proportional repetitive controller is used to perform ripple suppression to obtain a first current command value.

[0019] Optionally, the control parameters of the proportional repetitive controller include a stability coefficient, a gain coefficient, a periodic phase delay coefficient, and a proportional coefficient. The step of using the first voltage input proportional repetitive controller to perform ripple suppression to obtain a first current command value includes:

[0020] Performing a difference operation on the first voltage and a preset phase advance coefficient to obtain a first difference;

[0021] performing a multiplication operation on the first difference and the stability coefficient to obtain a first product value;

[0022] Performing a multiplication operation on the first multiplication value and the periodic phase delay coefficient to obtain a new preset phase advance coefficient;

[0023] Performing a multiplication operation on the new preset phase advance coefficient and the gain coefficient to obtain a second product value;

[0024] Performing a multiplication operation on the second product value and the preset low-pass filter transfer function to obtain a third product value;

[0025] Performing a multiplication operation on the third product value and the proportional coefficient to obtain a fourth product value;

[0026] A multiplication operation is performed on the fourth product value and the first voltage to obtain a first current command value.

[0027] Optionally, the using the compensation voltage and a preset reference voltage to perform compensation capacitor voltage control to obtain a second current command value includes:

[0028] Performing a difference operation between the compensation voltage and the preset reference voltage to obtain a second difference;

[0029] The second difference is multiplied by a preset proportional-integral controller transfer function to obtain a second current command value.

[0030] Optionally, performing gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a switch duty cycle includes:

[0031] performing a sum operation on the first current command value and the second current command value to obtain a first sum value;

[0032] performing a difference operation on the first sum and the inductor current to obtain a third difference;

[0033] Adopting the DC bus voltage input gain scheduling proportional controller to perform adaptive proportional adjustment to obtain a dynamic proportional coefficient;

[0034] The dynamic proportional coefficient and the third difference are multiplied to obtain the duty cycle of the switch tube.

[0035] Optionally, the DC bus voltage input gain scheduling proportional controller is used to perform adaptive proportional adjustment to obtain a dynamic proportional coefficient, including:

[0036] Performing a ratio operation on the DC bus voltage and a preset bus regulated peak voltage to obtain a first ratio;

[0037] Performing a difference operation using a preset maximum value of the proportional coefficient and a preset minimum value of the proportional coefficient to obtain a fourth difference;

[0038] performing a multiplication operation on the first ratio and the fourth difference to obtain a fifth product;

[0039] A sum operation is performed on the fifth multiplication value and the preset minimum value of the proportional coefficient to obtain a dynamic proportional coefficient.

[0040] Optionally, the three-level parallel DC power supply system includes a three-level topology active filter device and a low-voltage DC power supply system;

[0041] The three-level topology active filter device is connected in parallel with the low-voltage DC power supply system.

[0042] Optionally, the three-level topology active filter device includes a power device switch module and a filter branch, the power device switch module is connected in series with the filter branch, the filter branch includes a filter inductor, a compensation capacitor, and a compensation inductor connected in series in sequence, the power device switch module includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first high-voltage side voltage divider capacitor, and a second high-voltage side voltage divider capacitor connected in series, and based on the switch tube duty cycle, the target compensation current is modulated by the power device switch module of the three-level parallel DC power supply system, and ripple cancellation is performed, including:

[0043] Performing pulse width modulation on the switch tube duty cycle signal to obtain a modulation result;

[0044] When the modulation result indicates that the first switch tube and the fourth switch tube are turned on, and the second switch tube and the third switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor via the first high-side voltage-dividing capacitor, the second high-side voltage-dividing capacitor, and the compensation voltage to generate a target compensation current;

[0045] When the modulation result is that the first switch tube and the fourth switch tube are turned off, and the second switch tube and the third switch tube are turned on, applying a voltage to the filter inductor or the compensation inductor through the compensation voltage to generate a target compensation current;

[0046] When the modulation result shows that the first switch tube and the third switch tube are turned on, and the second switch tube and the fourth switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor through the first high-side voltage divider capacitor and the compensation voltage until a current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as a target compensation current;

[0047] When the modulation result shows that the first switch tube and the third switch tube are turned off, and the second switch tube and the fourth switch tube are turned on, a voltage is applied to the filter inductor or the compensation inductor through the second high-voltage side voltage divider capacitor and the compensation voltage until a current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as a target compensation current;

[0048] The target compensation current is injected into the low-voltage direct current power supply system to cancel ripples.

[0049] A second aspect of the present invention provides an active filter system for a low-voltage DC power supply system based on proportional repetitive control, which is applied to a three-level parallel DC power supply system, comprising:

[0050] An acquisition module, configured to acquire a DC bus voltage, a compensation voltage, and an inductor current corresponding to the three-level parallel DC power supply system;

[0051] a processing module, configured to determine a DC bus voltage ripple based on the DC bus voltage;

[0052] a DC bus ripple voltage control module, configured to, when the DC bus voltage ripple is not equal to a preset ripple value, perform DC bus ripple voltage control using the DC bus voltage ripple to obtain a first current command value;

[0053] a compensation capacitor voltage control module, configured to perform compensation capacitor voltage control using the compensation voltage and a preset reference voltage to obtain a second current command value;

[0054] a gain scheduling proportional control module, configured to perform gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a duty cycle of the switch tube;

[0055] The ripple cancellation module is used to generate a target compensation current and perform ripple cancellation based on the duty cycle of the switch tube by modulating the power device switch module of the three-level parallel DC power supply system.

[0056] It can be seen from the above technical solutions that the present invention has the following advantages:

[0057] In the present invention, by introducing a collaborative control architecture of a proportional repetitive controller and gain-scheduled proportional control, accurate tracking and suppression of ripple AC quantities of different frequencies are achieved through repeated learning and compensation of periodic ripple signals, which greatly improves the dynamic response speed and steady-state control accuracy of ripple compensation. At the same time, compared with the defect of proportional resonant control that requires designing complex control parameters for AC quantities of different frequencies, the proportional repetitive controller of the present invention only requires a set of control parameters to control ripple AC quantities of different frequencies, and the parameter calculation method is simple. In addition, gain-scheduled proportional control is used in the current inner loop, which can adjust the proportional coefficient according to the size of the DC bus voltage, keeping the system stable and not prone to oscillation at low voltage, and improving the response speed of the system at high voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] Figure 1 A flowchart of a method for active filtering of a low-voltage DC power supply system based on proportional repetitive control provided by an embodiment of the present invention;

[0060] Figure 2 A block diagram of the active filtering control strategy provided by an embodiment of the present invention;

[0061] Figure 3 A schematic diagram of the topology of a low-voltage DC power supply system provided in an embodiment of the present invention;

[0062] Figure 4 A schematic structural diagram of a three-level topology active filter device provided in an embodiment of the present invention connected in parallel with the low-voltage DC power supply system;

[0063] Figure 5 A calculation block diagram of a proportional repetitive controller provided by an embodiment of the present invention;

[0064] Figure 6 A schematic diagram showing the DC bus voltage waveform of the active filter device simulation effect provided by an embodiment of the present invention;

[0065] Figure 7 A structural block diagram of an active filter system for a low-voltage DC power supply system based on proportional repetitive control provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The embodiments of the present invention provide a method and system for active filtering of a low-voltage DC power supply system based on proportional repetitive control, which is used to solve the technical problem that the proportional-integral control strategy adopted in existing DC active filtering solutions has poor tracking effect on AC quantities, and the proportional resonant control strategy requires designing corresponding control parameters for each AC quantity of different frequencies, which leads to extremely complex control parameter settings.

[0067] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0068] In DC systems, AC quantities of varying frequencies exist. PI controllers require parameter readjustment for each frequency to achieve optimal control. However, due to the complexity and interdependencies of parameter adjustment, it is difficult to accurately track multiple frequencies simultaneously.

[0069] A PR controller requires designing appropriate control parameters for each AC variable with different frequencies. For example, in a low-voltage DC power supply system, there may be ripple AC variables with frequencies of 50Hz, 100Hz, or even higher. The PR controller must determine the appropriate proportional (P) and resonant (R) parameters for each frequency to achieve optimal control. This means that when the system has a wide variety of AC variable frequencies, parameter design becomes extremely complex, requiring extensive calculations and debugging to determine the optimal values ​​for each set of parameters.

[0070] For mid- and high-frequency ripple control, conventional proportional and repetitive control parameters alone cannot maintain system stability. Therefore, additional parameters such as damping and phase compensation are necessary. For example, when the system is exposed to high-frequency ripple interference (e.g., several hundred hertz or even higher), damping parameters are needed to suppress oscillations and prevent instability. Furthermore, phase compensation parameters are required to correct phase shifts that may occur during high-frequency signal transmission and control. The addition of these additional parameters not only increases the number of parameters, but also requires complex analysis and debugging to determine their respective value ranges and their interplay, further complicating parameter setup.

[0071] Because PR controllers are designed for specific AC frequency and system characteristics, when operating conditions change (such as power supply voltage fluctuations or load variations that alter AC characteristics) or when they are applied to a different system, the original parameters may no longer apply, requiring a complex redesign and adjustment process. This makes PR controllers lack versatility and flexibility when used in different operating conditions and systems, making it difficult to quickly adapt to new application scenarios.

[0072] The existing control strategies for active filtering solutions for DC systems generally use PI control or PR control. Both control schemes have defects: PI control has poor tracking effect on AC quantities, and the parameter calculation of the PR controller is extremely complex.

[0073] This paper proposes a method and system for active filtering in a low-voltage DC power supply system based on proportional repetitive control. A non-isolated three-level bidirectional DC-DC converter (DC-DC) is used as the topology for the DC active filter. A proportional repetitive controller (PRE) control strategy is employed to suppress DC bus voltage ripple. Proportional repetitive control requires only one set of parameters to effectively track AC ripples of varying frequencies in a low-voltage DC power supply system, and parameter calculation is simple.

[0074] See also Figure 1-Figure 2 , Figure 1 A flowchart of a method for active filtering of a low-voltage DC power supply system based on proportional repetitive control is provided in an embodiment of the present invention.

[0075] Figure 2 A block diagram of the active filtering control strategy provided by an embodiment of the present invention;

[0076] The present invention provides an active filtering method for a low-voltage DC power supply system based on proportional repetitive control, which is applied to a three-level parallel DC power supply system, comprising:

[0077] See also Figure 3 , DC bus voltage V dc The DC load and harmonic source load are connected in parallel to the DC bus.

[0078] See also Figure 4 , a three-level parallel DC power supply system includes a three-level topology active filter device and a low-voltage DC power supply system;

[0079] The three-level topology active filter device is connected in parallel with the low-voltage DC power supply system.

[0080] The three-level topology active filter device of the present invention adopts a non-isolated three-level bidirectional DC / DC circuit as the topology and is connected in parallel to a DC bus.

[0081] Figure 4 The DC-APF (Direct Current Active Power Filter) in the DC bus is connected in parallel at both ends of the DC bus. The DC bus voltage is V dc The specific topology of the DC-APF non-isolated three-level bidirectional DC / DC circuit is as follows: Figure 4 As shown in the box: the left end of the DC-APF is connected in parallel to the DC bus, C2 is the first high-voltage side voltage-dividing capacitor, C3 is the second high-voltage side voltage-dividing capacitor, S1, S2, S3, and S4 are four IGBTs (Insulated Gate Bipolar Transistors) with anti-parallel diodes, specifically referring to the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube, L1 is the filter inductor, C1 is the compensation capacitor, L2 is the compensation inductor, and i apf is the inductor current.

[0082] The three-level topology active filter device includes a power device switch module and a filter branch. The power device switch module is connected in series with the filter branch. The filter branch includes a filter inductor, a compensation capacitor, and a compensation inductor connected in series in sequence. The power device switch module includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first high-voltage side voltage divider capacitor, and a second high-voltage side voltage divider capacitor connected in series. The circuit connection relationship of the three-level topology active filter device is as follows:

[0083] The first high-voltage side voltage-dividing capacitor C2 is connected in series with the second high-voltage side voltage-dividing capacitor C3;

[0084] One end of the first high-voltage side voltage-dividing capacitor C2 away from the second high-voltage side voltage-dividing capacitor C3 is respectively connected to the high-potential output end and the first switch tube S1;

[0085] One end of the first switch tube S1 away from the first high-voltage side voltage-dividing capacitor C2 is respectively connected to the second switch tube S2 and the filter inductor L1;

[0086] The filter inductor L1, the compensation capacitor C1 and the compensation inductor L2 are connected in series in sequence;

[0087] The second switch tube S2 and the third switch tube S3 are connected in series;

[0088] One end of the second high-voltage side voltage-dividing capacitor C3 away from the first high-voltage side voltage-dividing capacitor C2 is respectively connected to the low-potential output end and the fourth switch tube S4;

[0089] One end of the fourth switch tube S4 away from the second high-side voltage-dividing capacitor C3 is respectively connected to the third switch tube S3 and the compensation inductor L2.

[0090] It is worth mentioning that the symmetrical arrangement of the filter inductor and the compensation inductor makes the overall structure of the three-level topology active filter device more symmetrical, which can suppress common-mode interference.

[0091] Taking the first switch S1 as an example, when the system is operating normally, the maximum voltage across the first switch S1 is the potential difference from the potential at which it is connected to the connection point between the first high-voltage side voltage divider capacitor C2 and the second high-voltage side voltage divider capacitor C3. dc The maximum voltage that the first switch tube S1 can withstand is 2V. dc The same applies to the other switch tubes (the second switch tube S2, the third switch tube S3 and the fourth switch tube S4). This is different from the traditional two-level topology where the switch tube bears the entire DC bus voltage V dc Compared to conventional MOSFETs, voltage stress is reduced to half. In low-voltage systems, lower voltage stress allows for the selection of switching devices with relatively low withstand voltage ratings, thus simplifying the selection process. Furthermore, lower voltage stress reduces losses during the switching device turn-on and turn-off processes.

[0092] Because the three-level topology reduces the voltage stress on the switching devices, it also reduces losses during the turn-on and turn-off phases. In traditional two-level topologies, higher voltage stress results in higher switching losses. The reduced switching losses in the three-level topology mean the system can operate at a higher switching frequency without excessive losses, thereby improving system efficiency. With equivalent switching losses, a higher switching frequency can increase the ripple suppression bandwidth. For example, in PWM modulation with carrier phase-shift control, a higher switching frequency allows the inductor current to more quickly track the preset command current, resulting in better ripple suppression. This further enhances the power quality improvement effect of the three-level active filter device on low-voltage DC power supply systems.

[0093] Therefore, the present invention connects a three-level topology active filter device in parallel with a low-voltage DC power supply system. In the three-level topology, the voltage borne by the switch tube is only half of the DC bus voltage. Compared with the two-level topology in which the switch tube bears the entire DC bus voltage, this greatly reduces the voltage stress of the switch tube, allowing the switch tube to select a device with a lower voltage resistance level, thereby improving the reliability of the system and reducing the cost and difficulty of heat dissipation design.

[0094] Step 101: Obtain a DC bus voltage, a compensation voltage, and an inductor current corresponding to a three-level parallel DC power supply system.

[0095] In an embodiment of the present invention, a DC bus voltage of a low-voltage DC power supply system is obtained, a compensation voltage of a compensation capacitor in a three-level topology active filter device is obtained, and an inductor current of a filter inductor in the three-level topology active filter device is obtained.

[0096] Please note that Figure 2 The filtering method proposed in the present invention detects the DC bus voltage V dc , compensation capacitor voltage U c1 , inductor current i apf Then, the power device switch module of the three-level topology active filter device is generated through the filtering control strategy, and the target compensation inductance is injected into the low-voltage DC power supply system through the filter inductor L1 to cancel the ripple to achieve the DC bus voltage V dc filtering effect.

[0097] Step 102: Determine the DC bus voltage ripple based on the DC bus voltage.

[0098] Furthermore, step 102 may include the following sub-steps:

[0099] S11. Perform multiplication operation on the DC bus voltage and a preset low-pass filter transfer function to obtain a filtered voltage.

[0100] In a specific implementation, to facilitate the implementation of the method, the above-mentioned process of step 102 to step 103 can be converted into a formula encapsulation form, wherein the expression of the preset low-pass filter transfer function can be as follows:

[0101]

[0102] Where, Represents the low-pass filter transfer function, specifically the discrete domain expression of a first-order RC low-pass filter (Resistor-Capacitor First-order Low-pass Filter). Low-pass filters can select filters of different orders and types according to actual accuracy requirements. represents the characteristic angular frequency, represents the sampling period, Represents a unit delay link, which means delaying the signal by one sampling period.

[0103] It's important to note that z in the discrete domain is similar to s in the frequency domain and t (seconds, minutes, hours, etc.) in the time domain. It represents the "complex frequency" of discrete-time signals and systems and serves as the mathematical foundation for analyzing dynamic behavior in the digital world. In digital systems, signals do not change continuously but are sampled at discrete time points nT. T is the sampling interval, and n is an integer (..., -2, -1, 0, 1, 2, ...). Therefore, systems must be analyzed under discrete conditions, whereas time in the natural world is continuous. Converting continuous variables into discrete quantities requires a series of transformations, including the z-transform, which establishes the connection between the discrete and time domains.

[0104] In discrete domain Indicates what happened at the previous time point, z -2 Indicates what happened at the previous two time points; 0 Indicates what is happening at the current time point; 1 Indicates what will happen at the next point in time, and so on

[0105] It is worth mentioning that the present invention proposes a transfer function of a first-order RC low-pass filter, which can effectively attenuate the high-frequency ripple components in the DC bus voltage. From the structure of the transfer function, it can be seen that when there is a ripple higher than the cut-off frequency in the DC bus voltage, due to Due to the presence of and the characteristics of the denominator, the gain corresponding to high-frequency ripple is significantly reduced. Specifically, in the DC bus voltage ripple detection scenario, the bus voltage may contain ripple components of various frequencies. The low-pass filter can filter out high-frequency noise and unnecessary high-frequency ripple, providing a relatively pure low-frequency ripple signal for subsequent active filtering control, thereby achieving more accurate ripple compensation and ripple analysis.

[0106] S12. Perform a difference operation on the DC bus voltage and the filtered voltage to obtain a DC bus voltage ripple.

[0107] In the embodiment of the present invention, the DC bus voltage and the filter voltage are used to perform a difference operation to obtain the DC bus voltage ripple Δu dc .

[0108] In a specific implementation, to facilitate the implementation of the method, the process of step 101 above can be converted into a formula encapsulation form, wherein the expression of the DC bus voltage ripple can be as follows:

[0109]

[0110] It should be noted that the DC bus voltage is detected to obtain voltage ripple information. The voltage ripple is determined by filtering the DC bus voltage and comparing the filtered result with the original DC bus voltage.

[0111] Step 103 : When the DC bus voltage ripple is not equal to the preset ripple value, a first current command value is determined based on a proportional repetitive controller using the DC bus voltage ripple and the preset ripple standard value.

[0112] Further, see Figure 5 , step 103 may include the following sub-steps:

[0113] S21 . When the DC bus voltage ripple is not equal to the preset ripple value, perform a difference operation between the DC bus voltage ripple and the preset ripple standard value to obtain a first voltage.

[0114] In an embodiment of the present invention, when the DC bus voltage ripple is not equal to zero, it means that there is a ripple component in the DC bus voltage and the ripple needs to be eliminated. The preset ripple standard value is preferably 0, and the DC bus voltage ripple and the preset ripple standard value are used to perform a difference operation to obtain the first voltage.

[0115] S22: Use a first voltage input proportional repetitive controller to perform ripple suppression to obtain a first current command value.

[0116] In the embodiment of the present invention, a first voltage input proportional resonant (PR) controller is used to suppress ripples to obtain a first current command value i ref1 The purpose of this process is to convert the DC bus voltage V dc The ripple is controlled to 0.

[0117] In a specific implementation, to facilitate the implementation of the method, the above-mentioned process of step 102 to step 103 can be converted into a formula encapsulation form, wherein the expression of the first current command value can be as follows:

[0118]

[0119] Where, represents the first current command value, Discrete-domain expression representing a proportional repetitive controller.

[0120] Furthermore, the control parameters of the proportional repetitive controller include a stability coefficient, a gain coefficient, a periodic phase delay coefficient, and a proportional coefficient. S22 may include the following sub-steps:

[0121] S221 . Perform a difference operation on the first voltage and a preset phase advance coefficient to obtain a first difference.

[0122] S222: Perform a multiplication operation on the first difference and the stability coefficient to obtain a first product value.

[0123] S223 , performing a multiplication operation on the first product value and the periodic phase delay coefficient to obtain a new preset phase advance coefficient.

[0124] S224: Perform a multiplication operation on the new preset phase advance coefficient and the gain coefficient to obtain a second product value.

[0125] S225 , performing a multiplication operation on the second product value and a preset low-pass filter transfer function to obtain a third product value.

[0126] S226. Perform a multiplication operation using the third product value and the proportional coefficient to obtain a fourth product value.

[0127] S227 . Perform a multiplication operation on the first voltage using the fourth product value to obtain a first current command value.

[0128] Furthermore, in a specific implementation, to facilitate the implementation of the method, the process of step 103 can be converted into a formula encapsulation form, wherein the expression of the proportional repetitive controller transfer function can be as follows:

[0129]

[0130] Where, represents the first voltage, Indicates the preset phase advance coefficient, specifically the phase advance link, the appropriate Helps the repetitive controller to achieve faster convergence speed, The value of It is related to factors such as the order and type of Indicates the number of sampling cycles of delay, It represents the stability coefficient, which is usually a constant close to 1 but less than 1. represents the periodic phase delay coefficient, Indicates the number of samples per unit fundamental frequency period, that is, N=T0 / T s , T0 is the fundamental frequency period, Represents the gain coefficient. Its value can affect the stability and convergence speed of the controller. The actual value can be adjusted according to the actual situation. Represents a low-pass filter. The expression is the same as the preset low-pass filter transfer function. The same preset low-pass filter transfer function can select filters of different orders and types according to actual accuracy requirements. Therefore, the second product value is multiplied by the preset low-pass filter transfer function to obtain the third product value. Represents the proportional coefficient, specifically referring to the proportional control part of proportional repetitive control.

[0131] It should be noted that the preset phase lead coefficient is a parameter pre-set in the design of a proportional repetitive controller. Its main purpose is to adjust the phase of the signal in the system. By appropriately setting the number of delayed sampling cycles to obtain the preset phase lead coefficient, the phase of the controller's output signal can be adjusted to achieve better phase synchronization with the ripple signal, thereby improving the controller's ability to suppress ripple. The new preset phase lead coefficient is an updated parameter obtained through a series of operations based on the preset phase lead coefficient. This generation process is actually based on the current operating state of the system (represented by the first voltage) and other controller parameters (stability coefficient, periodic phase delay coefficient, etc.), dynamically adjusting the preset phase lead coefficient to adapt to system changes. Its function is to enable the controller to automatically adjust the phase lead amount according to the real-time operating conditions of the system, thereby improving the controller's adaptability and control performance.

[0132] In the specific implementation, for different frequencies of ripple AC, the control part is repeated It can periodically compensate for the ripple of a specific frequency according to the periodic phase delay and phase advance link, and the proportional control part This allows for a rapid response to deviation signals. Due to the use of a fixed set of parameters, ripple AC quantities of varying frequencies are processed within this unified control framework. For example, for a 50Hz ripple AC quantity, the repetitive control component compensates for the ripple of this frequency based on its periodic characteristics, delaying it by N sampling cycles and advancing its phase by m sampling cycles. A 100Hz ripple AC quantity is also processed according to this mechanism, but due to its shorter period, it undergoes more control cycles within a single base frequency cycle, thereby achieving tracking control of ripples of varying frequencies.

[0133] It is worth mentioning that the proportional repetitive controller proposed in this invention requires only a set of fixed parameters to effectively track ripple AC quantities of varying frequencies. Parameter settings are primarily based on the system's fundamental frequency characteristics (base frequency, primary ripple frequency), sampling period, and empirical values. Among the control parameters of the proportional repetitive controller, the stability factor and gain factor can be selected empirically within a certain range. The periodic phase delay factor and the preset phase advance factor are calculated using a simple frequency-phase relationship. The proportional coefficient is initially set based on the system's load and response speed requirements. These parameters remain constant throughout system operation, addressing ripple AC quantities of varying frequencies without increasing the number of parameters due to frequency variations. Compared to PR control strategies, which require specific control parameters for each AC quantity of varying frequencies, the present invention eliminates the need for complex parameter design for each AC quantity of varying frequencies, significantly simplifying the parameter design process. Furthermore, by employing a fixed set of parameters, the present invention eliminates the need for frequent parameter adjustments during system operation. Even with changes in the system's operating state, this set of parameters maintains relatively stable control performance, reducing the risk of system instability due to improper parameter adjustments.

[0134] Step 104 : Using the compensation voltage and the preset reference voltage to control the compensation capacitor voltage, to obtain a second current command value.

[0135] Furthermore, step 104 may include the following sub-steps:

[0136] S31 , performing a difference operation between the compensation voltage and the preset reference voltage to obtain a second difference.

[0137] S32 , performing a multiplication operation on the second difference and a preset proportional-integral controller transfer function to obtain a second current command value.

[0138] In the embodiment of the present invention, the second difference is input into a preset proportional-integral (PI) controller for proportional-integral processing to obtain a second current command value i ref2 The purpose of this step is to control the voltage of the compensation capacitor in the three-level topology active filter device to be stable at a given reference voltage U c1ref .

[0139] In a specific implementation, to facilitate the implementation of the method, the process of step 104 can be converted into a formula encapsulation form, wherein the expression of the second current command value can be as follows:

[0140]

[0141] Where, represents the second current command value, Indicates the preset reference voltage, represents the compensation voltage, represents the preset proportional-integral controller transfer function, specifically the discrete domain expression of the proportional-integral controller, represents the proportionality coefficient, Represents the integral coefficient.

[0142] It is worth noting that the proportional-integral (PI) controller provided by the present invention has a proportional coefficient that can quickly adjust the output of the controller according to the current deviation of the system, and the integral part is used to accumulate past deviations. and The value of can adjust the stability of the system. Due to its simple structure and good control performance, it is suitable for the low-voltage DC power supply system of the present invention.

[0143] Step 105 : Perform gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a duty cycle of the switch tube.

[0144] Furthermore, step 105 may include the following sub-steps:

[0145] S41 . Perform a sum operation on the first current command value and the second current command value to obtain a first sum.

[0146] S42 . Perform a difference operation on the first sum and the inductor current to obtain a third difference.

[0147] S43, using the DC bus voltage input gain scheduling proportional controller to perform adaptive proportional adjustment to obtain a dynamic proportional coefficient.

[0148] A Gain-Scheduling Proportional Controller (GSC) is a special type of proportional controller in which the gain (proportional coefficient) is not fixed but is adjusted according to the DC bus voltage.

[0149] Adaptive proportional regulation means that the gain-scheduled proportional controller can automatically adjust its proportional control parameters (proportional coefficient) according to the DC bus voltage to achieve better control effect.

[0150] The dynamic proportional coefficient refers to the proportional coefficient in the gain-scheduled proportional controller that changes dynamically with the DC bus voltage.

[0151] S44. Perform a multiplication operation on the dynamic proportional coefficient and the third difference to obtain a duty cycle of the switch tube.

[0152] In the embodiment of the present invention, the purpose of this step is to use the gain scheduling proportional controller to make the inductor current follow the current command value (ie the first sum value i ref = i ref1 +i ref2 ) changes, and the duty cycle d of the switching tube is obtained.

[0153] In a specific implementation, to facilitate the implementation of the method, the process of step 104 can be converted into a formula encapsulation form, wherein the expression of the switch tube duty cycle can be as follows:

[0154]

[0155] Where, Indicates the duty cycle of the switch tube, Indicates the dynamic scale factor.

[0156] The DC bus voltage input gain scheduling proportional controller is used to perform adaptive proportional adjustment to obtain the dynamic proportional coefficient.

[0157] Furthermore, S43 may include the following sub-steps:

[0158] S431. Perform a ratio operation on the DC bus voltage and the preset bus peak regulated voltage to obtain a first ratio.

[0159] S432: Perform a difference operation using the preset maximum value of the proportional coefficient and the preset minimum value of the proportional coefficient to obtain a fourth difference.

[0160] S433: Perform a multiplication operation on the first ratio and the fourth difference to obtain a fifth product.

[0161] S434: Perform a sum operation on the fifth multiplication value and the preset minimum value of the proportional coefficient to obtain a dynamic proportional coefficient.

[0162] In a specific implementation, to facilitate the implementation of the method, the process of step 104 can be converted into a formula encapsulation form, wherein the expression of the dynamic proportional coefficient can be as follows:

[0163]

[0164] Where, Indicates the maximum value of the preset proportional coefficient. Indicates the preset minimum value of the proportional coefficient. Indicates the preset bus steady peak voltage, specifically representing the maximum voltage of the specified bus voltage for stable operation. At low voltage, the proportional coefficient is relatively small, keeping the system stable and not prone to oscillation. At high voltage, the proportional coefficient is large, improving the response speed of the system.

[0165] It should be noted that the size of the dynamic proportional coefficient varies with the change of the DC bus voltage, and the present invention adopts a simple linear change.

[0166] It is worth mentioning that the system characteristics may vary at different DC bus voltage levels. By dynamically adjusting the proportional coefficient, a smaller proportional gain can be used at high voltage to avoid excessive system response, and a larger proportional gain can be used at low voltage to speed up the system response, thereby optimizing the system's control performance over the entire voltage variation range and improving the system's stability and response speed. Compared to traditional fixed proportional coefficient controllers that require manual adjustment of proportional parameters according to different operating conditions, the present invention proposes a dynamic proportional coefficient expression. If the load changes and causes the DC bus voltage to fluctuate, the dynamic proportional coefficient will change accordingly, allowing the proportional controller to better adapt to such voltage changes, more effectively control the system, and improve the system's adaptability to different operating conditions.

[0167] Step 106 : Based on the duty cycle of the switch tube, the target compensation current is generated by modulating the power device switch module of the three-level parallel DC power supply system, and ripple cancellation is performed.

[0168] Ripple cancellation refers to the process of injecting a target compensation current into a low-voltage DC power supply system to offset the ripple component with the voltage ripple.

[0169] Furthermore, step 106 may include the following sub-steps:

[0170] S51. Perform pulse width modulation on the switch tube duty cycle signal to obtain a modulation result.

[0171] It should be noted that in a three-level active filter device, the on-off relationship of the four switches is as follows: d represents the duty cycle of the first switch S1, 1-d represents the duty cycle of the fourth switch S4, the second switch S2 and the first switch S1 are turned on in a complementary manner, and the third switch S3 and the fourth switch S4 are turned on in a complementary manner. After obtaining the duty cycle d of the first switch S1, the four modulation waves for controlling the on-off of the four switches can be generated through PWM modulation.

[0172] In the embodiment of the present invention, d is obtained after the gain scheduling proportional controller of the inner current loop, and the duty cycle signal of the switch tube is pulse-width modulated, using a PWM modulation process of carrier phase shift control:

[0173] The first switch tube S1 and the second switch tube S2 are disconnected

[0174] The duty cycle signal d of the first switch S1 is compared with the periodic triangular carrier 1 (the period is the switching frequency). If the duty cycle signal d of the first switch S1 is greater than the triangular carrier 1, the first switch S1 is turned on. Because the second switch S2 is complementary to the first switch S1, when the first switch S1 is turned on, the second switch S2 is turned off.

[0175] The third switch tube S3 and the fourth switch tube S4 are disconnected

[0176] The aforementioned 1-d represents the duty cycle of the fourth switch S4. This control can be achieved through carrier phase-shift control. Similarly, the duty cycle signal d of the first switch S1 is compared with the periodic triangular carrier 2, but here the phase of triangular carrier 2 is opposite to that of triangular carrier 1. If the duty cycle signal d of the first switch S1 is greater than the phase of triangular carrier 2, the fourth switch S4 is turned on. Because the third and fourth switches S3 and S4 are complementary, when the fourth switch S4 is turned on, the third switch S3 is turned off.

[0177] It should be noted that the inductance values ​​of the filter inductor and the compensation inductor are set to be the same. Since the filter inductor and the compensation inductor are connected in series, the current flowing through the filter inductor or the compensation inductor is also the same. In the following steps S52-S55, the change characteristics of the filter inductor and the compensation inductor are the same.

[0178] S52. When the modulation result is that the first switch tube and the fourth switch tube are turned on and the second switch tube and the third switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor through the first high-voltage side voltage divider capacitor, the second high-voltage side voltage divider capacitor and the compensation voltage to generate a target compensation current.

[0179] In an embodiment of the present invention, a PWM modulated signal is input into a three-level topology active filter device to drive the first switch tube and the fourth switch tube to turn on, and the second switch tube and the third switch tube to turn off. In the Buck working state, a voltage is applied to both ends of the filter inductor or the compensation inductor through the high-potential output end of the first high-voltage side voltage divider capacitor, the second high-voltage side voltage divider capacitor and the compensation capacitor, thereby causing the current flowing through the filter inductor or the compensation inductor to change, thereby generating a target compensation current. In the Boost working state, a voltage is also applied to both ends of the filter inductor or the compensation inductor through the first high-voltage side voltage divider capacitor, the second high-voltage side voltage divider capacitor and the compensation voltage, thereby causing the current flowing through the filter inductor or the compensation inductor to change, thereby generating a target compensation current. However, at this time, the target compensation current is freewheeled through the anti-parallel diode of the first switch tube and the fourth switch tube.

[0180] S53: When the modulation result shows that the first switch tube and the fourth switch tube are turned off and the second switch tube and the third switch tube are turned on, apply a voltage to the filter inductor or the compensation inductor through the compensation voltage to generate a target compensation current.

[0181] In an embodiment of the present invention, a PWM modulated signal is input into a three-level topology active filter device to drive the first switch tube and the fourth switch tube to be turned off, and the second switch tube and the third switch tube to be turned on. In the Boost working state, a voltage is applied to both ends of the filter inductor or the compensation inductor through the low-potential output end where the compensation voltage is located, thereby causing the current flowing through the filter inductor or the compensation inductor to change, thereby generating a target compensation current. In the Buck working state, a voltage is also applied to both ends of the filter inductor or the compensation inductor through the compensation capacitor, thereby causing the current flowing through the filter inductor or the compensation inductor to change, but at this time, the target compensation current is freewheeling through the anti-parallel diodes of the second switch tube and the third switch tube.

[0182] A voltage is applied to the filter inductor or compensation inductor through the compensation capacitor in the three-level topology active filter device, thereby causing the current flowing through the filter inductor or compensation inductor to change, thereby generating a target compensation current. At this time, the change trend of the target compensation current is an increase in negative current or a decrease in positive current.

[0183] S54. When the modulation result is that the first switch tube and the third switch tube are turned on and the second switch tube and the fourth switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor through the first high-voltage side voltage divider capacitor and the compensation voltage until the current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as the target compensation current.

[0184] In an embodiment of the present invention, a PWM modulated signal is input into a three-level topology active filter device, driving the first and third switches to conduct, and the second and fourth switches to shut down. In the Boost operating state, the first and third switches form a path for freewheeling through the anti-parallel diodes. At this time, the second switch is turned off, so the current can only pass through the anti-parallel diode of the first switch, then through the first high-voltage side voltage divider capacitor, the compensation capacitor, and the anti-parallel diode of the third switch to complete a freewheeling loop until the current flowing through the filter inductor or compensation inductor reaches a preset command current, at which point the current flowing through the filter inductor or compensation inductor is used as the target compensation current. In the Buck operating state, the current is initially in the forward direction, and the first switch is turned on, so the current flows from the first switch. However, the fourth switch is turned off, and the current flows to the anti-parallel diode of the third switch, then through the first high-voltage side voltage divider capacitor to the left end of the first switch, completing a freewheeling loop until the current flowing through the filter inductor or compensation inductor reaches the preset command current, at which point the current is used as the target compensation current.

[0185] S55. When the modulation result is that the first switch tube and the third switch tube are turned off, and the second switch tube and the fourth switch tube are turned on, a voltage is applied to the filter inductor or the compensation inductor through the second high-voltage side voltage divider capacitor and the compensation voltage until the current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as the target compensation current.

[0186] In an embodiment of the present invention, a PWM modulated signal is input into a three-level topology active filter device to drive the first switch tube and the third switch tube to be turned off, and the second switch tube and the fourth switch tube to be turned on. In the Buck working state, the fourth switch tube, the second high-voltage side voltage-dividing capacitor and the anti-parallel diode of the second switch tube form a freewheeling path. At this time, the fourth switch tube is turned on, and the current flows into the anti-parallel diode of the fourth switch tube. Since the first switch tube is turned off, the current can only pass through the second high-voltage side voltage-dividing capacitor, pass through the compensation capacitor, and then pass through the anti-parallel diode of the second switch tube to complete a freewheeling loop until it flows through the filter inductor or the compensation capacitor. When the current of the inductor reaches the preset command current, the current flowing through the filter inductor or the compensation inductor is used as the target compensation current; in the Boost working state, the second switch tube, the second high-voltage side voltage-dividing capacitor, and the anti-parallel diode of the fourth switch tube form a freewheeling path. At this time, the second switch tube is turned on, and the current flows from the second switch tube. Since the third switch tube is turned off, the current flows in through the anti-parallel diode of the fourth switch tube. After passing through the second high-voltage side voltage-dividing capacitor, the current passes through the anti-parallel diode of the second switch tube to complete a freewheeling loop. Until the current flowing through the filter inductor or the compensation inductor reaches the preset command current, the current is used as the target compensation current.

[0187] S56. Inject the target compensation current into the low-voltage DC power supply system to cancel the ripple.

[0188] In an embodiment of the present invention, a target compensation current opposite to the ripple is injected into a DC bus in a low-voltage DC power supply system.

[0189] It should be noted that by adjusting the on / off states of switches S1-S4 in real time, the three-level active filter device can output a target compensation current that is opposite to the ripple. When this target compensation current is injected into the low-voltage DC power supply system, it offsets the voltage ripple, thereby achieving the active filtering purpose of filtering out the ripple.

[0190] It is worth mentioning that, based on the scenario where the three-level topology active filter is connected to a low-voltage DC power supply system, the three-level topology active filter of the present invention can drive the switching of the switch tube according to different modulation results, flexibly control the filter inductor to generate the target compensation current, and ultimately enable the target compensation current injected into the low-voltage DC power supply system to more effectively filter the ripple, significantly improving the ability to suppress the ripple in the system. In addition, the three-level topology active filter device of the present invention also involves a freewheeling control, which can ensure that the inductor current stably and efficiently tracks the preset command current, reduce current fluctuations and energy loss during the transition process, and improve the working efficiency of the three-level topology active filter device.

[0191] It should be noted that, through the control of the above process, the DC bus voltage V dc The effect of controlling the ripple to 0 is essentially to transfer the ripple fluctuation of the DC bus voltage to the APF.

[0192] The present invention provides a simulation test example

[0193] Build a simulation model of a low-voltage DC power supply system and DC-APF. In the simulation model, the load-side harmonic source generates 5th and 8th order ripples. When DC-APF is added at 2s, the simulation waveform of the DC bus voltage is as follows: Figure 6 As shown, it can be seen that the ripple current generated by the harmonic source load will cause large ripple fluctuations on the DC bus voltage. After adding the DC active filter device designed by the present invention, most of the ripple fluctuations of the DC bus voltage are filtered out.

[0194] The present invention adopts a proportional repetitive control strategy and gain-scheduled proportional control to filter out DC bus ripples of different frequencies in a low-voltage DC power supply system.

[0195] In the present invention, by introducing a collaborative control architecture of a proportional repetitive controller and gain-scheduled proportional control, accurate tracking and suppression of ripple AC quantities of different frequencies are achieved through repeated learning and compensation of periodic ripple signals, which greatly improves the dynamic response speed and steady-state control accuracy of ripple compensation. At the same time, compared with the defect of proportional resonant control that requires designing complex control parameters for AC quantities of different frequencies, the proportional repetitive controller of the present invention only requires a set of control parameters to control ripple AC quantities of different frequencies, and the parameter calculation method is simple. In addition, gain-scheduled proportional control is used in the current inner loop, which can adjust the proportional coefficient according to the size of the DC bus voltage, keeping the system stable and not prone to oscillation at low voltage, and improving the response speed of the system at high voltage.

[0196] See also Figure 7 , Figure 7A structural block diagram of an active filter system for a low-voltage DC power supply system based on proportional repetitive control provided by an embodiment of the present invention.

[0197] The present invention provides a low-voltage DC power supply system active filter system based on proportional repetitive control, which is applied to a three-level parallel DC power supply system, comprising:

[0198] An acquisition module 701 is configured to acquire a DC bus voltage, a compensation voltage, and an inductor current corresponding to a three-level parallel DC power supply system;

[0199] The processing module 702 is configured to determine a DC bus voltage ripple based on the DC bus voltage.

[0200] a DC bus ripple voltage control module 703 for performing DC bus ripple voltage control using the DC bus voltage ripple to obtain a first current command value when the DC bus voltage ripple is not equal to a preset ripple value;

[0201] The compensation capacitor voltage control module 704 is configured to control the compensation capacitor voltage using the compensation voltage and a preset reference voltage to obtain a second current command value;

[0202] The gain scheduling proportional control module 705 is used to perform gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value and the second current command value to obtain the duty cycle of the switch tube;

[0203] The ripple cancellation module 706 is configured to generate a target compensation current and perform ripple cancellation based on the duty cycle of the switch tube by modulating the power device switch module of the three-level parallel DC power supply system.

[0204] Furthermore, the processing module 702 includes:

[0205] A filter voltage submodule is used to perform a multiplication operation on the DC bus voltage and a preset low-pass filter transfer function to obtain a filter voltage;

[0206] The DC bus voltage ripple submodule is used to perform a difference operation between the DC bus voltage and the filtered voltage to obtain the DC bus voltage ripple.

[0207] Furthermore, the DC bus ripple voltage control module 703 includes:

[0208] A first voltage submodule is configured to, when the DC bus voltage ripple is not equal to a preset ripple value, perform a difference operation between the DC bus voltage ripple and a preset ripple standard value to obtain a first voltage;

[0209] The first current command value submodule is used to perform ripple suppression using a first voltage input proportional repetitive controller to obtain a first current command value.

[0210] Furthermore, the control parameters of the proportional repetitive controller include a stability coefficient, a gain coefficient, a periodic phase delay coefficient, and a proportional coefficient. The first current command value submodule includes:

[0211] A first difference unit is configured to perform a difference operation between the first voltage and a preset phase advance coefficient to obtain a first difference;

[0212] A first multiplication unit is used to perform a multiplication operation using the first difference and the stability coefficient to obtain a first product value;

[0213] A new preset phase advance coefficient unit is used to perform a multiplication operation using the first product value and the periodic phase delay coefficient to obtain a new preset phase advance coefficient;

[0214] A second multiplication unit is used to perform a multiplication operation using a new preset phase advance coefficient and a gain coefficient to obtain a second product value;

[0215] a third multiplication unit, configured to perform a multiplication operation on the second product value and a preset low-pass filter transfer function to obtain a third product value;

[0216] a fourth multiplication unit, configured to perform a multiplication operation using the third multiplication value and a proportional coefficient to obtain a fourth multiplication value;

[0217] The first current command value output unit is configured to perform a multiplication operation on the first voltage using the fourth product value to obtain a first current command value.

[0218] Furthermore, the compensation capacitor voltage control module 704 includes:

[0219] A second difference submodule, configured to perform a difference operation between the compensation voltage and a preset reference voltage to obtain a second difference;

[0220] The second current command value submodule is configured to perform a multiplication operation on the second difference and a preset proportional-integral controller transfer function to obtain a second current command value.

[0221] Furthermore, the gain scheduling ratio control module 705 includes:

[0222] A first sum submodule, configured to perform a sum operation using the first current command value and the second current command value to obtain a first sum;

[0223] a third difference submodule, configured to perform a difference operation on the first sum and the inductor current to obtain a third difference;

[0224] A dynamic proportional coefficient submodule is used to perform adaptive proportional adjustment using a DC bus voltage input gain scheduling proportional controller to obtain a dynamic proportional coefficient;

[0225] The switch tube duty cycle submodule is used to perform a multiplication operation on the dynamic proportional coefficient and the third difference to obtain the switch tube duty cycle.

[0226] Furthermore, the dynamic scale factor submodule includes:

[0227] A first ratio unit is configured to perform a ratio operation on the DC bus voltage and the preset bus peak regulated voltage to obtain a first ratio;

[0228] a fourth difference unit, configured to perform a difference operation using a preset maximum value of the proportional coefficient and a preset minimum value of the proportional coefficient to obtain a fourth difference;

[0229] a fifth multiplication unit, configured to perform a multiplication operation on the first ratio and the fourth difference to obtain a fifth product;

[0230] The dynamic proportional coefficient output unit is used to perform a sum operation on the fifth multiplication value and the preset minimum proportional coefficient value to obtain the dynamic proportional coefficient.

[0231] Furthermore, the three-level topology active filter device includes a power device switch module and a filter branch, the power device switch module and the filter branch are connected in series, the filter branch includes a filter inductor, a compensation capacitor, and a compensation inductor connected in series in sequence, the power device switch module includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first high-side voltage-dividing capacitor, and a second high-side voltage-dividing capacitor connected in series, and the ripple cancellation module 706 includes:

[0232] The modulation result submodule is used to perform pulse width modulation on the switch tube duty cycle signal to obtain a modulation result;

[0233] a first control submodule, configured to apply a voltage to the filter inductor or the compensation inductor via the first high-side voltage-dividing capacitor, the second high-side voltage-dividing capacitor, and the compensation voltage to generate a target compensation current when the modulation result indicates that the first and fourth switching tubes are turned on and the second and third switching tubes are turned off;

[0234] a second control submodule, configured to apply a voltage to the filter inductor or the compensation inductor via a compensation voltage to generate a target compensation current when the modulation result shows that the first switch tube and the fourth switch tube are turned off and the second switch tube and the third switch tube are turned on;

[0235] a third control submodule, configured to, when the modulation result shows that the first and third switching tubes are turned on and the second and fourth switching tubes are turned off, apply a voltage to the filter inductor or the compensation inductor through the first high-voltage side voltage divider capacitor and the compensation voltage until the current flowing through the filter inductor or the compensation inductor reaches a preset command current, and then use the current as the target compensation current;

[0236] a fourth control submodule, configured to, when the modulation result indicates that the first and third switching tubes are turned off and the second and fourth switching tubes are turned on, apply a voltage to the filter inductor or the compensation inductor through the second high-voltage side voltage divider capacitor and the compensation voltage until the current flowing through the filter inductor or the compensation inductor reaches a preset command current, and then use the current as the target compensation current;

[0237] The injection submodule is used to inject the target compensation current into the low-voltage DC power supply system to cancel the ripple.

[0238] In the present invention, by introducing a collaborative control architecture of a proportional repetitive controller and gain-scheduled proportional control, accurate tracking and suppression of ripple AC quantities of different frequencies are achieved through repeated learning and compensation of periodic ripple signals, which greatly improves the dynamic response speed and steady-state control accuracy of ripple compensation. At the same time, compared with the defect of proportional resonant control that requires designing complex control parameters for AC quantities of different frequencies, the proportional repetitive controller of the present invention only requires a set of control parameters to control ripple AC quantities of different frequencies, and the parameter calculation method is simple. In addition, gain-scheduled proportional control is used in the current inner loop, which can adjust the proportional coefficient according to the size of the DC bus voltage, keeping the system stable and not prone to oscillation at low voltage, and improving the response speed of the system at high voltage.

[0239] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0240] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0241] Units described as separate components may or may not be physically separate, and 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 these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0242] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0243] If the integrated unit 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 the present invention, or the portion that contributes to the prior art, or all or 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 for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the method of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

[0244] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A low voltage DC power supply system active filtering method based on proportional repetitive control, characterized in that: Applicable to three-level parallel DC power supply system, including: Obtaining a DC bus voltage, a compensation voltage, and an inductor current corresponding to the three-level parallel DC power supply system; Determining a DC bus voltage ripple based on the DC bus voltage; When the DC bus voltage ripple is not equal to the preset ripple value, determining a first current command value based on a proportional repetitive controller by using the DC bus voltage ripple and a preset ripple standard value; Using the compensation voltage and a preset reference voltage to control the compensation capacitor voltage to obtain a second current command value; Performing gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a switch duty cycle; Based on the duty cycle of the switch tube, a target compensation current is generated by modulating the power device switch module of the three-level parallel DC power supply system, and ripple cancellation is performed.

2. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 1, characterized in that: The determining of the DC bus voltage ripple based on the DC bus voltage includes: Performing a multiplication operation on the DC bus voltage and a preset low-pass filter transfer function to obtain a filtered voltage; A difference operation is performed between the DC bus voltage and the filtered voltage to obtain a DC bus voltage ripple.

3. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 2, characterized in that: When the DC bus voltage ripple is not equal to the preset ripple value, determining the first current command value based on the proportional repetitive controller by using the DC bus voltage ripple and the preset ripple standard value includes: When the DC bus voltage ripple is not equal to the preset ripple value, performing a difference operation between the DC bus voltage ripple and the preset ripple standard value to obtain a first voltage; The first voltage input proportional repetitive controller is used to perform ripple suppression to obtain a first current command value.

4. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 3 is characterized in that: The control parameters of the proportional repetitive controller include a stability coefficient, a gain coefficient, a periodic phase delay coefficient, and a proportional coefficient. The first voltage input proportional repetitive controller is used to perform ripple suppression to obtain a first current command value, including: Performing a difference operation on the first voltage and a preset phase advance coefficient to obtain a first difference; performing a multiplication operation on the first difference and the stability coefficient to obtain a first product value; Performing a multiplication operation on the first multiplication value and the periodic phase delay coefficient to obtain a new preset phase advance coefficient; Performing a multiplication operation on the new preset phase advance coefficient and the gain coefficient to obtain a second product value; Performing a multiplication operation on the second product value and the preset low-pass filter transfer function to obtain a third product value; Performing a multiplication operation on the third product value and the proportional coefficient to obtain a fourth product value; A multiplication operation is performed on the fourth product value and the first voltage to obtain a first current command value.

5. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 1, characterized in that: The method of using the compensation voltage and a preset reference voltage to perform compensation capacitor voltage control to obtain a second current command value includes: Performing a difference operation between the compensation voltage and the preset reference voltage to obtain a second difference; The second difference is multiplied by a preset proportional-integral controller transfer function to obtain a second current command value.

6. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 1, characterized in that: The step of performing gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a switch duty cycle includes: performing a sum operation on the first current command value and the second current command value to obtain a first sum value; performing a difference operation on the first sum and the inductor current to obtain a third difference; Adopting the DC bus voltage input gain scheduling proportional controller to perform adaptive proportional adjustment to obtain a dynamic proportional coefficient; The dynamic proportional coefficient and the third difference are multiplied to obtain the duty cycle of the switch tube.

7. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 6, characterized in that: The DC bus voltage input gain scheduling proportional controller is used to perform adaptive proportional adjustment to obtain a dynamic proportional coefficient, including: Performing a ratio operation on the DC bus voltage and a preset bus regulated peak voltage to obtain a first ratio; Performing a difference operation using a preset maximum value of the proportional coefficient and a preset minimum value of the proportional coefficient to obtain a fourth difference; performing a multiplication operation on the first ratio and the fourth difference to obtain a fifth product; A sum operation is performed on the fifth multiplication value and the preset minimum value of the proportional coefficient to obtain a dynamic proportional coefficient.

8. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to any one of claims 1 to 7, characterized in that: The three-level parallel DC power supply system includes a three-level topology active filter device and a low-voltage DC power supply system; The three-level topology active filter device is connected in parallel with the low-voltage DC power supply system.

9. The active filtering method for a low-voltage DC power supply system based on proportional repetitive control according to claim 8, characterized in that: The three-level topology active filter device includes a power device switch module and a filter branch, wherein the power device switch module is connected in series with the filter branch, and the filter branch includes a filter inductor, a compensation capacitor, and a compensation inductor connected in series in sequence. The power device switch module includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first high-voltage side voltage divider capacitor, and a second high-voltage side voltage divider capacitor connected in series. Based on the duty cycle of the switch tube, the target compensation current is modulated by the power device switch module of the three-level parallel DC power supply system, and ripple cancellation is performed, including: Performing pulse width modulation on the switch tube duty cycle signal to obtain a modulation result; When the modulation result indicates that the first switch tube and the fourth switch tube are turned on, and the second switch tube and the third switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor via the first high-side voltage-dividing capacitor, the second high-side voltage-dividing capacitor, and the compensation voltage to generate a target compensation current; When the modulation result is that the first switch tube and the fourth switch tube are turned off, and the second switch tube and the third switch tube are turned on, applying a voltage to the filter inductor or the compensation inductor through the compensation voltage to generate a target compensation current; When the modulation result shows that the first switch tube and the third switch tube are turned on, and the second switch tube and the fourth switch tube are turned off, a voltage is applied to the filter inductor or the compensation inductor through the first high-side voltage divider capacitor and the compensation voltage until a current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as a target compensation current; When the modulation result shows that the first switch tube and the third switch tube are turned off, and the second switch tube and the fourth switch tube are turned on, a voltage is applied to the filter inductor or the compensation inductor through the second high-voltage side voltage divider capacitor and the compensation voltage until a current flowing through the filter inductor or the compensation inductor reaches a preset command current, and the current is used as a target compensation current; The target compensation current is injected into the low-voltage direct current power supply system to cancel ripples.

10. A low voltage DC power supply system active filter system based on proportional repetitive control, characterized in that: Applicable to three-level parallel DC power supply system, including: An acquisition module, configured to acquire a DC bus voltage, a compensation voltage, and an inductor current corresponding to the three-level parallel DC power supply system; a processing module, configured to determine a DC bus voltage ripple based on the DC bus voltage; a DC bus ripple voltage control module, configured to, when the DC bus voltage ripple is not equal to a preset ripple value, perform DC bus ripple voltage control using the DC bus voltage ripple to obtain a first current command value; a compensation capacitor voltage control module, configured to perform compensation capacitor voltage control using the compensation voltage and a preset reference voltage to obtain a second current command value; a gain scheduling proportional control module, configured to perform gain scheduling proportional control using the inductor current, the DC bus voltage, the first current command value, and the second current command value to obtain a duty cycle of the switch tube; The ripple cancellation module is used to generate a target compensation current and perform ripple cancellation based on the duty cycle of the switch tube by modulating the power device switch module of the three-level parallel DC power supply system.

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