Multi-harmonic-source low-voltage direct-current power supply system active filtering method and system based on local current detection

Abstract

The invention discloses a multi-harmonic-source low-voltage direct-current power supply system active filtering method and system based on local current detection, and relates to the technical field of low-voltage direct-current power supply. The current ripples at the position can comprehensively reflect the whole system ripples after multiple harmonic sources and loads at different positions are superposed, dependence on specific load access positions is not needed, the influence of load position uncertainty on ripple suppression is fundamentally overcome, it is ensured that the active filter can output compensation ripples in a targeted mode all the time, effective suppression is achieved, and meanwhile the effect that the compensation ripples are effectively suppressed is achieved. The quasi-proportional resonance controller has high-gain suppression capability on specific frequency ripples, stable control of the proportional-integral controller on a direct-current component is combined, and the accuracy of ripple elimination and the stability of system operation can be considered at the same time through double-instruction cooperation; through the real-time feedback of the inductive current and the rapid adjustment of the proportional controller, the ripple change can be dynamically responded, and the real-time cancellation of the ripple can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage direct current power supply, and in particular to an active filtering method and system for a multi-harmonic source low-voltage direct current power supply system based on local current detection. 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] Existing DC active filtering solutions often follow the same design philosophy as AC systems, suppressing voltage ripple by detecting the ripple current of the harmonic source. However, AC system research typically assumes a single idealized harmonic source on the load side. Control strategies require the APF (Active Power Filter) to generate compensating currents of equal magnitude and opposite direction when the harmonic source location is known. For example, patent publication CN112217381B proposes a "Circuit and Method for Suppressing Secondary Ripple of a Single-Phase Converter DC Bus Voltage." This method filters the double-frequency ripple on the DC bus, but the filter parameter calculation method is complex and requires knowledge of the voltage amplitude and phase of the harmonic source. Changes in the harmonic source structure or location require the addition of a new sampling structure.

[0005] In a DC system, various loads can become harmonic sources. The location where the load, i.e., the harmonic source, is connected to the DC bus is uncertain. Therefore, traditional active filtering solutions cannot detect load current and are therefore not suitable for low-voltage DC power supply systems with multiple harmonic sources. Summary of the Invention

[0006] The present invention provides a method and system for active filtering of a multi-harmonic source low-voltage DC power supply system based on local current detection, which solves the technical problem that traditional active filtering schemes cannot effectively suppress ripple in a multi-harmonic source low-voltage DC power supply system due to uncertain load access positions.

[0007] A first aspect of the present invention provides an active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection, wherein an active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, comprising:

[0008] collecting the DC bus current whose parallel point is far from the load side and the compensation voltage and inductor current of the active filter;

[0009] Determining a DC bus current ripple based on the DC bus current;

[0010] When the DC bus current ripple is not equal to zero, the DC bus current ripple is input into a quasi-proportional resonant controller to obtain a first current command value;

[0011] Determine a second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller;

[0012] Determine the duty cycle of the switch tube by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller;

[0013] Based on the duty cycle of the switch tube, the switching of the power device switch in the active filter is controlled to drive the active filter to perform ripple cancellation.

[0014] Optionally, determining the DC bus current ripple based on the DC bus current includes:

[0015] Performing a multiplication operation on the DC bus current and a preset low-pass filter transfer function to obtain a first product value;

[0016] A difference operation is performed between the first product value and the DC bus current to obtain a DC bus current ripple.

[0017] Optionally, the quasi-proportional resonant controller includes a plurality of parallel-connected bandwidth resonant links and proportional links, and the DC bus current ripple is input into the quasi-proportional resonant controller to obtain the first current command value, including:

[0018] Performing a difference calculation between the DC bus current ripple and a preset current ripple reference value to obtain a ripple current deviation value;

[0019] Using the ripple current deviation value to input each of the bandwidth resonance links to perform multi-harmonic bandwidth resonance processing to obtain multiple harmonic bandwidth resonance outputs;

[0020] Performing a sum operation on a plurality of the harmonic bandwidth resonance outputs to obtain a harmonic bandwidth resonance superposition value;

[0021] The ripple current deviation value is input into the proportional link to perform proportional operation to obtain a fundamental frequency amplitude correction value;

[0022] A sum operation is performed on the harmonic bandwidth resonance superposition value and the fundamental frequency amplitude correction amount to obtain a first current command value.

[0023] Optionally, the determining the second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller includes:

[0024] Performing a difference operation between the compensation voltage and a preset reference voltage to obtain a first difference;

[0025] The first difference is input into a proportional-integral controller for proportional-integral processing to obtain a second current command value.

[0026] Optionally, the determining the duty cycle of the switch tube by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller includes:

[0027] performing a sum operation on the first current command value and the second current command value to obtain a first sum value;

[0028] performing a difference operation on the first sum and the inductor current to obtain a second difference;

[0029] The second difference is input into the proportional controller for proportional processing to obtain the duty cycle of the switch tube.

[0030] Optionally, the power device switch includes a first insulated gate bipolar switch tube and a second insulated gate bipolar switch tube, and controlling the switching of the power device switch in the active filter based on the duty cycle of the switch tubes to drive the active filter to perform ripple cancellation includes:

[0031] Performing pulse width modulation on the duty cycle of the switch tube to obtain a modulation result;

[0032] When the modulation result is that the first insulated gate bipolar switch is turned on and the second insulated gate bipolar switch is turned off, driving the compensation capacitor in the active filter to store energy;

[0033] When the modulation result is that the first insulated gate bipolar switch is turned off and the second insulated gate bipolar switch is turned on, a compensation current opposite to the ripple is injected into the DC bus through the compensation capacitor to cancel the ripple.

[0034] A second aspect of the present invention provides an active filter system for a multi-harmonic source low-voltage DC power supply system based on local current detection, wherein the active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, comprising:

[0035] An acquisition module, configured to acquire the DC bus current whose parallel point is far from the load side, as well as the compensation voltage and inductor current of the active filter;

[0036] a ripple processing module, configured to determine a DC bus current ripple based on the DC bus current;

[0037] a first command value generating module, configured to, when the DC bus current ripple is not equal to zero, input the DC bus current ripple into a quasi-proportional resonant controller to obtain a first current command value;

[0038] A second command value generating module, configured to determine a second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller;

[0039] a switch duty cycle module, configured to determine a switch duty cycle by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller;

[0040] A driving module is used to control the switching of power device switches in the active filter based on the duty cycle of the switch tube, and drive the active filter to perform ripple cancellation.

[0041] A third aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor performs the steps of the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any one of the above items.

[0042] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any one of the above items.

[0043] A fifth aspect of the present invention provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any one of the above items.

[0044] It can be seen from the above technical solutions that the present invention has the following advantages:

[0045] The present invention collects the DC bus current at a parallel point far away from the load side. The current ripple at this position can comprehensively reflect the overall ripple of the system after the superposition of multiple harmonic sources and loads at different positions, without relying on the specific load access position. It fundamentally overcomes the influence of load position uncertainty on ripple suppression, and ensures that the active filter can always output compensation ripple in a targeted manner to achieve effective suppression. At the same time, the quasi-proportional resonant controller has a high gain suppression capability for specific frequency ripples. Combined with the proportional-integral controller's stable control of the DC component, the dual-instruction collaboration can simultaneously take into account the accuracy of ripple elimination and the stability of system operation; through real-time feedback of the inductor current and rapid adjustment of the proportional controller, it can dynamically respond to ripple changes and achieve real-time cancellation of ripples. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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.

[0047] Figure 1 A flowchart of a method for active filtering of a multi-harmonic source low-voltage DC power supply system based on local current detection provided by an embodiment of the present invention;

[0048] Figure 2 Schematic diagram of a multi-harmonic source low-voltage DC power supply system provided by an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of the parallel structure of an active filter and a DC bus provided in an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of the active filter topology provided in an embodiment of the present invention;

[0051] Figure 5 A block diagram of an active filtering control strategy based on local current detection provided by an embodiment of the present invention;

[0052] Figure 6 A schematic diagram of simulation results provided by an embodiment of the present invention;

[0053] Figure 7 A schematic diagram of the voltage control effect provided by an embodiment of the present invention;

[0054] Figure 8 A schematic diagram of the current control effect provided by an embodiment of the present invention;

[0055] Figure 9A structural block diagram of an active filtering system for a multi-harmonic source low-voltage DC power supply system based on local current detection provided by an embodiment of the present invention;

[0056] Figure 10 This is a structural block diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] Embodiments of the present invention provide a method and system for active filtering of a multi-harmonic source low-voltage DC power supply system based on local current detection, which is used to solve the technical problem that traditional active filtering solutions cannot effectively suppress ripple in a multi-harmonic source low-voltage DC power supply system due to uncertain load access positions.

[0058] 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.

[0059] On the one hand, the passive filters widely used in DC systems have significant drawbacks: First, due to their fixed resonant frequency design, they can only attenuate specific sub-ripples, resulting in poor frequency domain adaptability. Second, their filtering performance is significantly affected by grid impedance parameters and load fluctuations, resulting in insufficient robustness under operating conditions. Third, to suppress the dominant secondary low-frequency ripple in DC systems, large-capacity capacitor banks are required, which exponentially increases the size and weight of the passive filter and reduces its economic efficiency. On the other hand, existing DC active filtering solutions rely on directly detecting the ripple current of the harmonic sources in the system. However, the widespread distribution of multiple harmonic sources in low-voltage DC power supply systems makes it difficult to locate the disturbance source and achieve accurate sampling and tracking compensation of the full-domain ripple current.

[0060] The present invention proposes an active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection. A buck-boost circuit is selected as the topology of the DC active filter. By detecting the local current signal of the active filter (i.e., sampling the DC bus current on the left side (away from the load side) of the parallel connection point between the active filter and the DC bus), ripple filtering of the DC bus voltage and current in the DC system can be achieved.

[0061] See also Figure 1 , Figure 1 A flowchart of the steps of a method for active filtering of a multi-harmonic source low-voltage DC power supply system based on local current detection is provided in an embodiment of the present invention.

[0062] The present invention provides an active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection. The active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, comprising:

[0063] A multi-harmonic source low-voltage DC power supply system refers to a power supply system with multiple harmonic generating sources in a low-voltage DC environment.

[0064] The present invention mainly targets a low-voltage DC power supply system with multiple harmonic sources, and filters the DC bus of the low-voltage DC power supply system with multiple harmonic sources to improve the power supply quality and protect sensitive equipment. Figure 2 As shown in the figure, the DC bus voltage V dc Rectified by the previous AC grid, R s is the line impedance on the DC bus, i dc is the DC bus current, and the load and harmonic source are connected in parallel to the DC bus.

[0065] The active filter proposed in the present invention adopts a buck-boost circuit as a topology and is connected in parallel to the DC bus. The parallel structure is as follows: Figure 3 As shown in the figure, the APF (Active Power Filter) is connected in parallel at both ends of the DC bus and is located close to the preceding AC grid, between the load and the preceding AC grid.

[0066] The specific topology of APF is as follows Figure 4 As shown in the figure, C1 is the compensation capacitor, L1 and R1 are the filter inductor and its equivalent resistance, i L is the inductor current, S1 and S2 are two cascaded IGBTs (Insulated Gate Bipolar Transistors), where S1 is the first insulated gate bipolar switch tube and S2 is the second insulated gate bipolar switch tube.

[0067] One end of the first insulated gate bipolar switch is connected to the DC bus;

[0068] The other end of the first insulated gate bipolar switch is connected to the second insulated gate bipolar switch and one end of the filter inductor respectively;

[0069] The other end of the filter inductor is connected to one end of the equivalent resistor;

[0070] The other end of the equivalent resistor is connected to one end of the compensation capacitor;

[0071] The other end of the compensation capacitor is connected to one end of the second insulated gate bipolar switch tube;

[0072] The other end of the second insulated gate bipolar switch is connected to the DC bus.

[0073] See also Figure 5 , Figure 5 The present invention provides a block diagram of the active filtering control strategy based on local current detection. The present invention measures the local current signal (ie, the DC bus current i dc ), for the inductor current i in the APF L Control to achieve the DC bus voltage V dc , DC bus current i dc The filtering effect is shown in steps 101 to 106 below:

[0074] Step 101: Collect the DC bus current at a parallel point far from the load side, as well as the compensation voltage and inductor current of the active filter.

[0075] It should be noted that since the DC bus ripple is the result of the combined effect of all harmonic sources, and the DC bus current at the parallel point far from the load side already contains the superimposed information of the system ripple, by sampling the DC bus current to the left of the parallel point between the active filter and the DC bus (far from the load side), the comprehensive effect of the bus voltage ripple can be equivalently reflected. Therefore, it is only necessary to sample the DC bus current to the left of the parallel point (far from the load side) to complete the ripple filtering of the DC bus voltage and current. There is no need to individually locate the position of each harmonic source and the size of the ripple current generated by the harmonic source. This is suitable for low-voltage DC systems with multiple harmonic sources and uncertain harmonic source positions.

[0076] In the embodiment of the present invention, the DC bus current i is collected when the parallel point is far from the load side. dc , compensation voltage U of the compensation capacitor in the active filter c1 And the inductor current i of the filter inductor in the active filter L .

[0077] Step 102: Determine the DC bus current ripple based on the DC bus current.

[0078] Furthermore, step 102 may include the following sub-steps:

[0079] S11 , performing a multiplication operation on the DC bus current and a preset low-pass filter transfer function to obtain a first product value.

[0080] The preset low-pass filter transfer function is specifically:

[0081]

[0082] Where, represents the preset low-pass filter transfer function, Indicates the characteristic angular frequency. Low-pass filters can select filters of different orders and types according to actual accuracy requirements. represents the complex frequency, symbol It is the basic variable in the frequency domain: complex frequency; it can be compared to the basic variable in the commonly used time domain: time. In the time domain, voltage and current change with time, so they are expressed using expressions related to time. Similarly, in the frequency domain, variables such as voltage, current, or transfer function can be expressed using expressions related to complex frequency, such as the preset low-pass filter transfer function expression here , the complex frequency s = σ + jω, σ is the real part, representing the exponential decay or growth factor, j is the imaginary unit, ω is the imaginary part, representing the angular frequency (in radians per second, rad / s), and the relationship between ω and the ordinary frequency f is ω = 2πf.

[0083] In the embodiment of the present invention, a multiplication operation is performed by performing a multiplication operation on the DC bus current and a preset low-pass filter transfer function to obtain a first product value.

[0084] S12. Perform a difference operation on the first product value and the DC bus current to obtain a DC bus current ripple.

[0085] In a specific implementation, to facilitate the implementation of the method, the above process can be converted into a formula encapsulation form, where the expression of the DC bus current ripple can be as follows:

[0086]

[0087] Where, Indicates the DC bus current ripple.

[0088] In the embodiment of the present invention, a difference operation is performed between the first product value and the DC bus current to obtain the DC bus current ripple.

[0089] Step 103 : When the DC bus current ripple is not equal to zero, the DC bus current ripple is input into a quasi-proportional resonant controller to obtain a first current command value.

[0090] It is worth mentioning that in actual applications, the grid frequency is time-varying, and the fundamental wave is allowed to vary within a range of ±0.5Hz. By analogy, when the ripple frequency reaches n, the allowable fluctuation range can reach ±0.5nHz. Since the ideal resonant controller only controls the ripple of fixed frequency, once there is fluctuation in the grid, the ideal resonant controller's ability to suppress harmonics will be weakened. Therefore, based on the existing ideal PR controller, the present invention introduces a bandwidth factor , an improved Quasi-Proportional Resonant (QPR) controller is constructed by introducing bandwidth Make the controller close to each ripple frequency Ripple of any width has a control effect, which can better adapt to the actual system. Since the main ripple frequency in the low-voltage DC power supply system is ripple of 12 times or less, a quasi-proportional resonant controller of 12 times or less can be selected here. The frequency domain expression of the quasi-proportional resonant controller mentioned above uses 12 times ripple frequency as an example. Quasi-proportional resonant controllers with higher ripple frequencies can also be used. There is no limitation here.

[0091] Furthermore, the quasi-proportional resonant controller includes a plurality of parallel-connected bandwidth resonant links and proportional links, and step 103 may include the following sub-steps:

[0092] S21. Perform a difference calculation between the DC bus current ripple and a preset current ripple reference value to obtain a ripple current deviation value.

[0093] The specific ripple current deviation value is:

[0094]

[0095] Where 0 represents the preset current ripple reference value.

[0096] S22, using the ripple current deviation value to input each bandwidth resonance link to perform multi-harmonic bandwidth resonance processing, and obtain multiple harmonic bandwidth resonance outputs.

[0097] S23. Perform a sum operation on the multiple harmonic bandwidth resonance output quantities to obtain a harmonic bandwidth resonance superposition value.

[0098] In the embodiment of the present invention, when the ripple current deviation value is input to each bandwidth resonant link ( ), each bandwidth resonant link responds to the corresponding ripple frequency component in the difference signal based on its own characteristics, generating a corresponding output. Since the primary ripple frequency in low-voltage DC power supply systems is ripples of the 12th order or less, multiple bandwidth resonant links corresponding to ripples of the 2nd to 12th order are used (multiple resonant links corresponding to multiple ripples are set based on actual conditions, and this is not a limitation; only ripples of the 2nd to 12th order are used as an example here). The outputs of these bandwidth resonant links (i.e., the harmonic bandwidth resonant output) are added together to obtain the harmonic bandwidth resonant superposition value output by these multiple bandwidth resonant links.

[0099] S24, using the ripple current deviation value to input the proportional link to perform proportional operation to obtain the fundamental frequency amplitude correction amount.

[0100] In the embodiment of the present invention, the ripple current deviation value is input into the proportional link, and the proportional link performs a proportional operation on the deviation value according to its set proportional gain to obtain the fundamental frequency amplitude correction amount.

[0101] S25 , performing a sum operation on the harmonic bandwidth resonance superposition value and the fundamental frequency amplitude correction value to obtain a first current command value.

[0102] In an embodiment of the present invention, the harmonic bandwidth resonance superposition value and the fundamental frequency amplitude correction amount are summed, and the final result is the first current command value. The first current command value comprehensively considers the resonance control of different ripple components and the overall proportional control, and is used to achieve control and regulation of the system.

[0103] It is worth mentioning that compared with the traditional proportional resonant controller which only controls a specific single frequency or a few specific frequencies, there is a problem of limited compensation capability, and it is difficult to achieve comprehensive and accurate ripple suppression when facing ripple interference of multiple frequencies and complex working conditions. The quasi-proportional resonant controller of the present invention takes into account the control of multiple ripples. By introducing the bandwidth factor, it can independently and accurately adjust the ripples of multiple frequencies and the ripples of width near each ripple frequency at the same time. In a low-voltage distribution network containing complex ripple components, by setting the appropriate resonator gain for each ripple respectively, the total ripple content in the system can be more effectively reduced, the ripple control accuracy is greatly improved, and the power quality of the system is improved.

[0104] In a specific implementation, to facilitate the implementation of the method, the above-mentioned steps 102 and 103 may be converted into a formula encapsulation form, wherein the expression of the first current command value may be as follows:

[0105]

[0106] Where, It is expressed as the frequency domain expression of a first-order RC low-pass filter (Resistor-Capacitor First-orderLow-pass Filter, resistor-capacitor first-order low-pass filter), is the frequency domain expression of the quasi-proportional resonant controller, is the proportional gain; is the resonator gain, for sub-ripple frequency, Indicates the bandwidth of the controller.

[0107] Step 104 : Determine a second current command value by using the compensation voltage and the preset reference voltage in combination with a proportional-integral controller.

[0108] Furthermore, step 104 may include the following sub-steps:

[0109] S31 . Perform a difference operation on the compensation voltage and the preset reference voltage to obtain a first difference.

[0110] S32: Input the first difference into a proportional-integral controller for proportional-integral processing to obtain a second current command value.

[0111] In a specific implementation, to facilitate the implementation of the method, the above step 104 process can be converted into a formula encapsulation form, wherein the expression of the second current command value can be as follows:

[0112]

[0113] Where, represents the second current command value, Indicates the preset reference voltage, represents the compensation voltage, represents the proportionality coefficient, represents the integral coefficient, is the frequency domain expression of the proportional-integral controller.

[0114] In the embodiment of the present invention, the compensation voltage U of the compensation capacitor C1 in the APF is sampled. c1 , and the preset reference voltage U c1ref After making the difference, the second current command value i is obtained through the proportional-integral (PI) controller. ref2 The purpose of this step is to control the compensation voltage in the APF to be stable at a given reference value U c1ref .

[0115] 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.

[0116] Step 105 : Determine the duty cycle of the switch tube by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller.

[0117] Furthermore, step 105 may include the following sub-steps:

[0118] S41 . Perform a sum operation on the first current command value and the second current command value to obtain a first sum.

[0119] S42 . Perform a difference operation on the first sum and the inductor current to obtain a second difference.

[0120] S43: Use the second difference to input the proportional controller to perform proportional processing to obtain the duty cycle of the switch tube.

[0121] In a specific implementation, to facilitate the implementation of the method, the above step 105 process can be converted into a formula encapsulation form, wherein the expression of the switch tube duty cycle can be as follows:

[0122]

[0123] Where, represents the duty cycle signal of the first insulated gate bipolar switch S1, is the size of the proportional coefficient, represents the inductor current.

[0124] In the embodiment of the present invention, the second difference input proportional controller is used for proportional processing. The purpose of this step is to make the inductor current follow the current command value (i.e., the first sum value i ref = i ref1 +i ref2 ) changes, and the switch tube duty cycle signal d is obtained.

[0125] Step 106: Based on the duty cycle of the switch tube, control the switching of the power device switch in the active filter to drive the active filter to perform ripple cancellation.

[0126] Furthermore, the power device switch includes a first insulated gate bipolar switch tube and a second insulated gate bipolar switch tube, and step 106 may include the following sub-steps:

[0127] S51. Perform pulse width modulation on the duty cycle of the switch tube to obtain a modulation result.

[0128] In an embodiment of the present invention, the on / off relationship of the two IGBTs in the active filter is as follows: d represents the duty cycle of the first IGBT S1, and the second IGBT S2 is turned on in a complementary manner to the first IGBT S1. Once the duty cycle d of the first IGBT S1 is determined, two modulation waves for controlling the on / off of the two IGBTs can be generated through PWM modulation.

[0129] 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 of the switch tube is pulse-width modulated, using a PWM modulation process of carrier phase shift control:

[0130] The first switch tube S1 and the second switch tube S2 are disconnected:

[0131] The duty cycle signal d of the first IGBT S1 is compared with the periodic triangular carrier 1 (the period is the switching frequency). If the duty cycle signal d of the first IGBT S1 is greater than the triangular carrier 1, the first IGBT S1 is turned on. Because the second IGBT S2 is complementary to the first IGBT S1, at the same time, if the first IGBT S1 is turned on, the second IGBT S2 is turned off.

[0132] S52: When the modulation result shows that the first insulated gate bipolar switch is turned on and the second insulated gate bipolar switch is turned off, driving the compensation capacitor in the active filter to store energy.

[0133] S53, and when the modulation result is that the first insulated gate bipolar switch tube is turned off and the second insulated gate bipolar switch tube is turned on, a compensation current opposite to the ripple is injected into the DC bus through the compensation capacitor to cancel the ripple. A compensation current opposite to the ripple is injected into the DC bus through the compensation capacitor to cancel the ripple.

[0134] In an embodiment of the present invention, when the first insulated gate bipolar switch is turned on, the compensation capacitor acts as an energy storage element, storing energy obtained from the DC bus in the form of magnetic energy. When the first insulated gate bipolar switch is turned off and the second insulated gate bipolar switch is turned on, the compensation capacitor releases the stored energy, providing an energy source for generating the compensation current. Specifically, when the system detects the presence of a ripple current of a certain frequency on the DC bus, by controlling the on and off timing of the first and second insulated gate bipolar switches, the compensation capacitor stores and releases energy according to a specific pattern, thereby generating a compensation current capable of offsetting the ripple.

[0135] It should be noted that during the conduction period of the second IGBT, the energy released by the compensation capacitor is injected into the DC bus through the filter inductor as a compensation current. The compensation capacitor has different capacitive reactance characteristics for signals of different frequencies, and can output a suitable compensation current waveform as needed to achieve the purpose of ripple suppression.

[0136] In an embodiment of the present invention, the generated compensation current is injected into the multi-harmonic source low-voltage DC power supply system to offset the ripples of the DC bus voltage and DC bus current, thereby achieving the active filtering purpose of filtering out the ripples.

[0137] It should be noted that, through the control of the above process, the DC bus current i dcThe ripple control effect is 0, so that the ripple current of the load-side harmonic source does not flow to the DC bus but directly enters the APF. In other words, the active filtering control strategy proposed in the present invention enables the APF to absorb the ripple current of the load-side harmonic sources 1 and 2, and can filter all harmonic sources on the load side in a multi-harmonic source DC system. It is worth mentioning that the ripple in the DC bus voltage is essentially due to the influence of the ripple current of the load-side harmonic source (ripple current flows through the load or line impedance to generate ripple voltage). Therefore, the active filtering control strategy proposed in the present invention can simultaneously filter out the ripple of the DC bus voltage and current.

[0138] In the present invention, by collecting the DC bus current at a parallel point far away from the load side, the current ripple at this position can comprehensively reflect the overall ripple of the system after the superposition of multiple harmonic sources and loads at different positions, without relying on the specific load access position. It fundamentally overcomes the influence of load position uncertainty on ripple suppression, ensures that the active filter can always output compensation ripple in a targeted manner, and achieves effective suppression. At the same time, the quasi-proportional resonant controller has a high gain suppression capability for specific frequency ripples. Combined with the proportional-integral controller's stable control of the DC component, the dual-instruction collaboration can simultaneously take into account the accuracy of ripple elimination and the stability of system operation; through real-time feedback of the inductor current and rapid adjustment of the proportional controller, it can dynamically respond to ripple changes and achieve real-time cancellation of ripples.

[0139] The following is a simulation test example:

[0140] Build a simulation model of a low-voltage DC power supply system and APF. In the simulation model, harmonic source 1 generates a second-order ripple current at 0.5s, and harmonic source 2 generates a fifth-order ripple current. APF is added at 1s. The simulation results are as follows: Figure 6 As shown, it can be seen that after the harmonic source generates ripple current, the DC bus voltage and current both generate large ripple current fluctuations. However, after the DC active filter device designed by the present invention is added, the ripple fluctuations of the DC bus voltage and current are basically filtered out.

[0141] It is worth mentioning that the core innovation of the present invention lies in current control. In the context of a multi-harmonic source low-voltage DC power supply system, the ripple current generated by the harmonic source on the load side is the main source of ripple in the system. The ripple current flows through the impedance to generate ripple voltage, so the ripple current is the fundamental disturbance. Compared with the existing voltage control, which can only eliminate voltage ripple but cannot completely eliminate current harmonics, the current control of the present invention can eliminate the voltage ripple in the DC bus by eliminating the fundamental disturbance ripple current.

[0142] The following is a verification example of the high-order ripple filtering effect:

[0143] In multi-harmonic low-voltage DC power supply systems, traditional voltage control schemes are limited in their ability to suppress high-frequency ripple due to the characteristics of bus voltage ripple. This demonstration compares the ripple filtering performance of the current control and voltage control methods of the present invention through theoretical derivation and characteristic analysis, verifying the advantages of current sampling.

[0144] Assume that there are capacitors on the DC bus to maintain bus stability, i c (t) is the capacitor current, u dc is the bus voltage (i.e., capacitor voltage), I is the ripple current amplitude, n is the ripple frequency, and ω is the angular frequency.

[0145] According to the current-voltage differential equation of the capacitor:

[0146]

[0147] Points can be obtained:

[0148]

[0149] The above formula shows that when the system has the same ripple current, the bus voltage amplitude is related to the ripple frequency n. The larger n, the smaller the bus voltage fluctuation. When the bus voltage fluctuation is small, the ripple component extracted by sampling the bus voltage for control is small. With limited sampling accuracy, the filtering effect of voltage control will deteriorate. In other words, voltage control cannot effectively filter out high-frequency ripple current in the system. However, bus current sampling control does not have this problem. The ripple frequency does not affect the ripple current amplitude. Bus current sampling control can effectively filter out high-frequency ripple in the system. In other words, under the same device accuracy conditions, the current control effect is better and the applicability is wider.

[0150] The following is a verification example of response speed:

[0151] In a multi-harmonic source low-voltage DC power supply system, a dynamic ripple disturbance environment consistent with actual operating conditions was constructed. Ripple disturbances of the same amplitude and mutation characteristics were simultaneously injected into two control schemes (i.e., the current control scheme of the present invention and the existing voltage control scheme). The system's recovery from the disturbance was observed 1 second after the control was started. The response speed and control effect were compared using the DC bus current waveform (reflecting the ripple suppression dynamics) and voltage waveform (reflecting the system's steady-state quality).

[0152] See also Figure 7 , when the voltage control scheme is adopted:

[0153] DC bus current: After the voltage control is added at 1s, the current curve still fluctuates with high frequency and large amplitude between 1s and 1.2s, indicating that the voltage control is slow to suppress the current ripple, and the system is still affected by the ripple disturbance.

[0154] DC bus voltage: Although the voltage tends to be stable at 1.2s, the curve is not completely flat, indicating that voltage control requires a longer time to offset disturbances, resulting in a slow response and limited steady-state accuracy.

[0155] See also Figure 8 , when the current control scheme is adopted:

[0156] DC bus current: After control is added at 1s, the current curve converges quickly from 1s to 1.2s, indicating that current control directly and precisely intervenes in current ripple, quickly suppressing high-frequency disturbances.

[0157] DC bus voltage: The voltage curve is basically stable at 1.2s, reflecting that the current control quickly stabilizes the current, indirectly allowing the voltage to recover faster, with a fast response speed and higher steady-state quality.

[0158] It can be seen that by comparing the "convergence speed" of the DC bus current and the "stability accuracy" of the DC bus voltage under the two types of control schemes, the current control scheme of the present invention can be clearly verified. Compared with the traditional voltage control scheme, it can respond to ripple disturbances more quickly, and achieve "current stabilization first, then voltage stabilization" by directly regulating the current, which is better in response speed and control effect.

[0159] In summary, the DC active filtering method proposed in the present invention does not require knowing the location of the harmonic source in the DC system, nor does it require detecting the ripple current generated by the harmonic source. It only needs to measure the DC bus current at the active filter device's grid connection point far away from the load side to filter the DC bus voltage and current, and the filtering effect is good. At the same time, the response speed is better than the existing voltage control speed.

[0160] See also Figure 9 , Figure 9 A structural block diagram of an active filtering system for a multi-harmonic source low-voltage DC power supply system based on local current detection provided by an embodiment of the present invention.

[0161] The present invention provides an active filter system for a multi-harmonic source low-voltage DC power supply system based on local current detection. The active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, comprising:

[0162] The acquisition module 901 is used to collect the DC bus current whose parallel point is far away from the load side, as well as the compensation voltage and inductor current of the active filter;

[0163] The ripple processing module 902 is configured to determine a DC bus current ripple based on the DC bus current;

[0164] A first command value generating module 903 is configured to, when the DC bus current ripple is not equal to zero, input the DC bus current ripple into a quasi-proportional resonant controller to obtain a first current command value;

[0165] A second command value generating module 904 is configured to determine a second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller;

[0166] The switch duty cycle module 905 is configured to determine the switch duty cycle by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller;

[0167] The driving module 906 is used to control the on / off of the power device switches in the active filter based on the duty cycle of the switch tube, and drive the active filter to perform ripple cancellation.

[0168] Furthermore, the ripple processing module 902 includes:

[0169] A first multiplication submodule is configured to perform a multiplication operation using the DC bus current and a preset low-pass filter transfer function to obtain a first product value;

[0170] The DC bus current ripple submodule is used to perform a difference operation on the first product value and the DC bus current to obtain the DC bus current ripple.

[0171] Furthermore, the quasi-proportional resonant controller includes a plurality of parallel-connected bandwidth resonant links and proportional links, and the first instruction value generating module 903 includes:

[0172] The ripple current deviation value submodule is used to perform a difference operation between the DC bus current ripple and a preset current ripple reference value to obtain a ripple current deviation value;

[0173] The harmonic bandwidth resonance output quantum module is used to use the ripple current deviation value to input each bandwidth resonance link to perform multi-harmonic bandwidth resonance processing and obtain multiple harmonic bandwidth resonance output quantities;

[0174] A harmonic bandwidth resonance superposition value submodule is used to perform a sum operation using multiple harmonic bandwidth resonance output quantities to obtain a harmonic bandwidth resonance superposition value;

[0175] The fundamental frequency amplitude correction quantum module is used to use the ripple current deviation value to input the proportional link for proportional calculation to obtain the fundamental frequency amplitude correction value;

[0176] The first current command value submodule is used to perform a sum operation on the harmonic bandwidth resonance superposition value and the fundamental frequency amplitude correction amount to obtain a first current command value.

[0177] Furthermore, the second instruction value generating module 904 includes:

[0178] A first difference submodule, configured to perform a difference operation between the compensation voltage and a preset reference voltage to obtain a first difference;

[0179] The second current command value submodule is used to use the first difference value to input the proportional-integral controller to perform proportional-integral processing to obtain a second current command value.

[0180] Furthermore, the switch duty cycle module 905 includes:

[0181] 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;

[0182] A second difference submodule is configured to perform a difference operation on the first sum and the inductor current to obtain a second difference;

[0183] The proportional processing submodule is used to use the second difference to input the proportional controller to perform proportional processing to obtain the duty cycle of the switch tube.

[0184] Furthermore, the power device switch includes a first insulated gate bipolar switch tube and a second insulated gate bipolar switch tube, and the driving module 906 includes:

[0185] The modulation result submodule is used to perform pulse width modulation on the duty cycle of the switch tube to obtain the modulation result;

[0186] An energy storage submodule, configured to drive the compensation capacitor in the active filter to store energy when the modulation result indicates that the first insulated gate bipolar switch is turned on and the second insulated gate bipolar switch is turned off;

[0187] The injection submodule is used to inject a compensation current opposite to the ripple into the DC bus through the compensation capacitor to cancel the ripple when the modulation result is that the first insulated gate bipolar switch tube is turned off and the second insulated gate bipolar switch tube is turned on.

[0188] The present invention collects the DC bus current at a parallel point far away from the load side. The current ripple at this position can comprehensively reflect the overall ripple of the system after the superposition of multiple harmonic sources and loads at different positions, without relying on the specific load connection position. It fundamentally overcomes the influence of load position uncertainty on ripple suppression, and ensures that the active filter can always output compensation ripple in a targeted manner to achieve effective suppression. At the same time, the quasi-proportional resonant controller has a high gain suppression capability for specific frequency ripples. Combined with the proportional-integral controller's stable control of the DC component, the dual-instruction collaboration can simultaneously take into account the accuracy of ripple elimination and the stability of system operation; through real-time feedback of the inductor current and rapid adjustment of the proportional controller, it can dynamically respond to ripple changes and achieve real-time cancellation of ripples.

[0189] See also Figure 10 , Figure 10 This is a structural block diagram of an electronic device provided by an embodiment of the present invention.

[0190] An electronic device according to an embodiment of the present invention includes: a memory 1001 and a processor 1002, wherein the memory 1001 stores a computer program; when the computer program is executed by the processor 1002, the processor 1002 executes the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any of the above embodiments.

[0191] Memory 1001 may be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Memory 1001 has storage space 1003 for program code 1013 for executing any of the method steps described above. For example, storage space 1003 for program code may include individual program codes 1013 for implementing various steps in the method described above. These program codes may be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact disks (CDs), memory cards, or floppy disks. The program codes may be compressed, for example, in a suitable format. When executed by a processing device, these codes cause the processing device to execute the various steps in the method described above. These program codes may be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact disks (CDs), memory cards, or floppy disks. The program codes may be compressed, for example, in a suitable format. When these codes are executed by a computing and processing device, they cause the computing and processing device to execute the various steps of the above-described method for active filtering of a multi-harmonic source low-voltage direct current power supply system based on local current detection.

[0192] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the active filtering method of a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any of the above embodiments is implemented.

[0193] An embodiment of the present invention further provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection as described in any of the above embodiments.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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 multi-harmonic source low voltage DC power supply system active filtering method based on local current detection, characterized in that: The active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, including: collecting the DC bus current whose parallel point is far from the load side and the compensation voltage and inductor current of the active filter; Determining a DC bus current ripple based on the DC bus current; When the DC bus current ripple is not equal to zero, the DC bus current ripple is input into a quasi-proportional resonant controller to obtain a first current command value; Determine a second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller; Determine the duty cycle of the switch tube by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller; Based on the duty cycle of the switch tube, the switching of the power device switch in the active filter is controlled to drive the active filter to perform ripple cancellation.

2. The active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to claim 1 is characterized in that: The determining of the DC bus current ripple based on the DC bus current includes: Performing a multiplication operation on the DC bus current and a preset low-pass filter transfer function to obtain a first product value; A difference operation is performed between the first product value and the DC bus current to obtain a DC bus current ripple.

3. The active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to claim 1 is characterized in that: The quasi-proportional resonant controller includes a plurality of parallel-connected bandwidth resonant links and proportional links. The DC bus current ripple is input into the quasi-proportional resonant controller to obtain a first current command value, including: Performing a difference operation between the DC bus current ripple and a preset current ripple reference value to obtain a ripple current deviation value; Using the ripple current deviation value to input each of the bandwidth resonance links to perform multi-harmonic bandwidth resonance processing to obtain multiple harmonic bandwidth resonance outputs; Performing a sum operation on a plurality of the harmonic bandwidth resonance outputs to obtain a harmonic bandwidth resonance superposition value; The ripple current deviation value is input into the proportional link to perform proportional operation to obtain a fundamental frequency amplitude correction value; A sum operation is performed on the harmonic bandwidth resonance superposition value and the fundamental frequency amplitude correction amount to obtain a first current command value.

4. The active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to claim 1, characterized in that: The method of using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller to determine the second current command value includes: Performing a difference operation between the compensation voltage and a preset reference voltage to obtain a first difference; The first difference is input into a proportional-integral controller for proportional-integral processing to obtain a second current command value.

5. The active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to claim 1, characterized in that: The method of using the first current command value, the second current command value, and the inductor current in combination with a proportional controller to determine the duty cycle of the switch tube 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 second difference; The second difference is input into the proportional controller for proportional processing to obtain the duty cycle of the switch tube.

6. The active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to any one of claims 1 to 5, characterized in that: The power device switch includes a first insulated gate bipolar switch tube and a second insulated gate bipolar switch tube. Based on the duty cycle of the switch tubes, the power device switch in the active filter is controlled to be turned on and off, and the active filter is driven to perform ripple cancellation, including: Performing pulse width modulation on the duty cycle of the switch tube to obtain a modulation result; When the modulation result is that the first insulated gate bipolar switch is turned on and the second insulated gate bipolar switch is turned off, driving the compensation capacitor in the active filter to store energy; When the modulation result is that the first insulated gate bipolar switch is turned off and the second insulated gate bipolar switch is turned on, a compensation current opposite to the ripple is injected into the DC bus through the compensation capacitor to cancel the ripple.

7. An active filter system for a multi-harmonic source low-voltage DC power supply system based on local current detection, characterized in that: The active filter is connected in parallel with the multi-harmonic source low-voltage DC power supply system, including: An acquisition module, configured to acquire the DC bus current whose parallel point is far from the load side, as well as the compensation voltage and inductor current of the active filter; a ripple processing module, configured to determine a DC bus current ripple based on the DC bus current; a first command value generating module, configured to, when the DC bus current ripple is not equal to zero, input the DC bus current ripple into a quasi-proportional resonant controller to obtain a first current command value; A second command value generating module, configured to determine a second current command value by using the compensation voltage and a preset reference voltage in combination with a proportional-integral controller; a switch duty cycle module, configured to determine a switch duty cycle by using the first current command value, the second current command value, and the inductor current in combination with a proportional controller; A driving module is used to control the switching of power device switches in the active filter based on the duty cycle of the switch tube, and drive the active filter to perform ripple cancellation.

8. An electronic device, characterized in that: The method comprises a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor performs the steps of the active filtering method of a multi-harmonic source low-voltage DC power supply system based on local current detection according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the active filtering method for a multi-harmonic source low-voltage direct current power supply system based on local current detection according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions. When the program instructions are executed by a computer, the computer is caused to perform the active filtering method for a multi-harmonic source low-voltage DC power supply system based on local current detection according to any one of claims 1 to 6.

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