An active power filter with electromagnetic shielding

Abstract

This invention discloses an active power filter with electromagnetic shielding, belonging to the field of power filter technology. It includes: an active power filter circuit module; and an integrated electromagnetic shielding housing for housing and shielding the active power filter circuit module. At least one structural part of the integrated electromagnetic shielding housing is integrated with the circuitry of the active power filter circuit module to form a functional filtering electrical component. The integrated electromagnetic shielding housing, in conjunction with the active power filter circuit module, forms a comprehensive electromagnetic shielding system that integrates source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding. This invention solves the problems of electromagnetic leakage, large size, high cost, and limited high-frequency shielding effect of traditional split-type shielding, achieving integrated electromagnetic shielding and active filter in terms of structure, electrical system, and thermal management, significantly improving the electromagnetic compatibility, power density, filtering performance, and long-term operational reliability of the equipment.

Description

Technical Field

[0001] This invention belongs to the field of power filter technology, and particularly relates to an active power filter with electromagnetic shielding. Background Technology

[0002] Active power filters (APFs) are a new type of power electronic device used for dynamic harmonic suppression. They are widely used in industrial, civil, communications, and new energy fields. APFs contain high-frequency switching devices (such as IGBTs) and high-speed DSP signals, which generate broadband electromagnetic interference (EMI) during operation. Current technologies typically employ shielding solutions to address APF EMI, specifically: 1. Split shielding: The standard APF is housed in a separate metal shielded cabinet. This method results in bulky equipment, high cost, and difficulty in completely suppressing electromagnetic leakage at cable entry and exit points, leading to discontinuous shielding effectiveness. 2. Integrated external shielding: A conductive coating or a metal shielding cover is applied to the APF casing. This method offers some shielding effectiveness, but it often lacks coordination with the internal circuit design of the APF, resulting in limited high-frequency shielding and potentially affecting heat dissipation. The common drawback of these existing solutions is that the electromagnetic shielding structure and the active filter circuit are physically and electrically separated. While interference signals are prevented from leaking out through interference methods, the electromagnetic interference is not effectively addressed at its source, resulting in certain defects in shielding effectiveness and equipment reliability design.

[0003] The core common defects of the existing solutions are: the electromagnetic shielding structure and the active filter circuit are physically and electrically separated, and only passive protection measures are used to prevent the leakage of interference signals. They fail to suppress electromagnetic interference from all aspects, including the interference source, the propagation path, and port leakage. Furthermore, the shielding and heat dissipation designs are contradictory, which ultimately leads to poor shielding effect, large equipment size, low reliability, and high cost. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an active power filter with electromagnetic shielding. Breaking away from the traditional design approach of "making the filter first and then adding shielding," this invention incorporates electromagnetic shielding as a core component of the active power filter circuit design. Through the deep integration of structure, electrical, and thermal management, a comprehensive electromagnetic shielding system is constructed, encompassing source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding coordination, thus solving the problems in the background technology.

[0005] This invention provides the following technical solution: An active power filter with electromagnetic shielding includes: an active power filter circuit module; and an integrated electromagnetic shielding housing for housing and shielding the active power filter circuit module. At least one structural part of the integrated electromagnetic shielding housing is combined with the circuitry of the active power filter circuit module to form a functional filtering electrical component. The integrated electromagnetic shielding housing, in conjunction with the circuitry, forms a comprehensive electromagnetic shielding system that includes source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding.

[0006] Preferably, the functional filtering electrical component is a capacitor, which is composed of the conductive part of the inner wall of the integrated electromagnetic shielding housing, the insulating dielectric layer, and the conductive pattern on the printed circuit board of the active power filtering circuit module; the capacitor is a flat DC bus support capacitor, which has the characteristics of large capacity and low equivalent series inductance.

[0007] Preferably, an integrated filter suppression network component is provided at all AC power inlets / outlets, signal interfaces, and grounding interfaces of the integrated electromagnetic shielding housing to block the leakage and intrusion of conducted electromagnetic interference from the physical ports.

[0008] Preferably, the filtering suppression network component includes three-phase differential-mode and common-mode filtering inductors. The inductors, together with the bridge arm inductors and filtering capacitors of the subsequent stage, form a complete three-stage LCL filtering network. The metal shell of the filtering suppression network component maintains a 360° seamless conductive connection with the integrated electromagnetic shielding shell to ensure shielding continuity. All high-voltage input and output lines and signal lines pass through the filtering suppression network component.

[0009] Preferably, the inner surface of the integrated electromagnetic shielding shell is provided with a frequency-selective electromagnetic wave processing structure. The structure is a frequency-selective surface or an electromagnetic wave absorbing material layer, which directionally absorbs / reflects interference in a specific frequency band generated by the switching frequency of the active power filter at 20KHz and its harmonics, and maintains high transmittance for the thermal radiation frequency band required for heat dissipation.

[0010] Preferably, the IGBT heat dissipation module and substrate of the active power filter circuit module are reliably electrically and thermally connected to the integrated electromagnetic shielding shell, so that the shell can also serve as a heat dissipation channel, thereby achieving synergistic optimization of electromagnetic shielding and thermal management; the integrated electromagnetic shielding shell is made of aluminum alloy with high conductivity and high thermal conductivity, or is made of metal-nonmetal composite material.

[0011] Preferably, the splicing joints of the integrated electromagnetic shielding shell adopt a dual connection structure of conductive adhesive sealing and metal buckle pressing, and a conductive gasket is set between the door and the main body of the shell to eliminate electromagnetic leakage points at the splicing gaps.

[0012] Preferably, the inner wall of the integrated electromagnetic shielding shell is further provided with a grounding copper busbar. The grounding copper busbar is equipotentially connected with the grounding terminal of the filter circuit module and the conductive part of the shell, suppressing electromagnetic reflection and crosstalk inside the shell and forming an internal electromagnetic shielding grounding system.

[0013] Preferably, the electromagnetic shielding method of the electromagnetic shielding system that combines source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding includes the following steps: S1. Interference Source Suppression: The structural part of the integrated electromagnetic shielding shell is integrated with the active power filter circuit module and designed as a functional filter electrical component, so that the shielding shell actively participates in the filtering function, weakening the strength of the interference signal from the source of electromagnetic interference. S2. Propagation path blocking: A closed electromagnetic shielding space is formed by the high conductivity structure of the integrated electromagnetic shielding shell. The shell splicing adopts a double conductive sealing structure, and the inner wall is equipped with an equipotential grounded copper busbar to block the crosstalk of interference signals inside the shell and the radiation propagation to the outside. S3. Specific frequency band absorption: A frequency-selective electromagnetic wave processing structure is set on the inner surface of the shielding shell to directionally absorb / reflect high-frequency interference signals of the APF switching frequency and its harmonics, without affecting the heat radiation heat dissipation of the equipment. S4. Full-port sealed suppression: The filter suppression network components are integrated into all power, signal and ground ports of the housing to suppress conducted interference at the source and prevent electromagnetic leakage and external interference from entering the ports. S5. Thermal Screen Collaborative Optimization: The heat-generating components of the filter circuit module are reliably thermally connected to the shielding housing, utilizing the large heat dissipation area of ​​the housing to achieve efficient heat dissipation. At the same time, the conductive structure of the housing maintains the integrity of the shielding, avoiding damage to the shielding effect by the heat dissipation design.

[0014] Preferably, the functional filtering electrical component in step S1 is a flat DC bus support capacitor or a filtering inductor. The capacitor is composed of a conductive part on the inner wall of the shielding housing, an insulating dielectric layer, and a conductive pattern on the circuit board. The inductor is composed of a specific structure of the shielding housing and an internal filtering inductor to form a distributed parameter LCL filtering circuit.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses an active power filter with electromagnetic shielding, which significantly improves the shielding effect: the constructed five-layer all-dimensional electromagnetic shielding system suppresses interference from the source, propagation path, radiation frequency band, and port leakage, completely eliminating the structural discontinuities and electromagnetic leakage points of traditional solutions. It improves the shielding effectiveness by ≥30dB against high-frequency interference of 20KHz switching frequency and its harmonics, and the electromagnetic compatibility of the equipment meets the highest level standard of GB / T17626-2018.

[0016] Significantly optimized size and cost: The external shielding structure has been removed, and the shielding shell is integrated with the filter circuit and heat dissipation structure. The size of the equipment is reduced by more than 40% compared with the traditional split shielding solution. At the same time, the materials such as shielding cabinets and additional heat dissipation components have been reduced, the assembly process has been reduced, and the overall material and manufacturing costs have been reduced.

[0017] Significantly enhanced thermal management and reliability: The shielded housing also serves as a heat dissipation channel, directly guiding the heat from heat-generating components such as inductors and IGBTs to the large heat dissipation area of ​​the housing. This reduces the internal temperature rise of the equipment by 15-20°C, effectively preventing device aging and performance degradation caused by excessive temperature rise. The mean time between failures (MTBF) of the equipment is increased to over 100,000 hours.

[0018] Deep optimization of filtering performance: The shielded housing actively participates in the formation of filtering elements (planar capacitor, distributed parameter LCL circuit). Its large capacity and low ESL characteristics significantly improve the high-frequency filtering characteristics of the filter, which can extend the filtering frequency band to above 1MHz and improve the suppression rate of high-frequency harmonics by 20%.

[0019] Improved ease of installation and maintenance: The integrated design makes the equipment structure compact, eliminating the need for additional shielded cabinets and simplifying on-site wiring and maintenance. The equipotential grounding copper busbar design of the casing reduces the difficulty of on-site grounding construction and improves the standardization of equipment installation.

[0020] High versatility and scalability: This electromagnetic shielding system method can flexibly adjust the frequency band of the electromagnetic wave absorbing material and the parameters of the filtering and suppression network according to the electromagnetic compatibility requirements of different application scenarios (industrial, new energy, communication). It is applicable to active power filters of different power levels (10kVA-1000kVA) and has broad application prospects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the method of the present invention.

[0023] Figure 2 This is a flowchart of the electromagnetic shielding method of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] Example 1: Active power filter integrating shielding housing and planar capacitor The electromagnetically shielded active power filter of this embodiment includes an integrated electromagnetic shielding housing 1 and an active power filter circuit module encapsulated therein; the circuit module includes an IGBT power board, a control board 2, a power supply board, a display board, a driver board, a terminal board, and an IGBT heat sink module.

[0027] Integrated electromagnetic shielding housing design: Made of 6061 aluminum alloy with high conductivity (≥60% IACS) and high thermal conductivity (≥180W / (m・K)). The housing is an integrally bent and formed structure. The joints adopt a double connection structure of conductive adhesive sealing + stainless steel metal buckle pressing. A beryllium copper conductive gasket is set between the door and the main body to eliminate all gaps and leakage points. The inner wall of the housing is equipped with a copper grounding grid, which is equipotentially welded to the grounding terminal of the filter circuit module and the inner wall of the housing. The grounding resistance is ≤0.01Ω.

[0028] The shielding and capacitor integration design: The inner surface of the housing base plate is precision milled to form an electrode pattern. The IGBT power board is directly fixed to this base plate. Between the large copper layer on the power board and the electrode pattern on the inner surface of the base plate, a 0.2mm thick polyimide insulating dielectric layer 4 is placed. Together, these three elements form a planar DC bus support capacitor with a capacitance of 2000μF and an equivalent series inductance (ESL) ≤5nH. This design enables the base plate of the shielding housing to simultaneously perform four functions: mechanical support, electromagnetic shielding, heat dissipation channel, and DC bus support capacitor, thereby reducing high-frequency interference generated by IGBT switching at the source of interference.

[0029] Thermal shielding collaborative design: The IGBT heat sink module is directly bonded to the housing base plate through thermally conductive silicone, with a thermal conductivity of ≥5W / (m・K). The heat generated by the IGBT is quickly dissipated through the heat sink and base plate. Heat dissipation fins 5 are set on the outer surface of the housing to further improve heat dissipation efficiency. When the equipment is working at full load, the IGBT junction temperature is ≤85℃.

[0030] Port processing: An embedded filter assembly consisting of a rod filter and a common-mode choke is installed at the AC power input / output port of the housing. The metal casing of the assembly achieves a 360° seamless conductive connection with the housing, and all high-voltage input and output lines pass through this assembly.

[0031] The core advantage of this embodiment is that it achieves deep integration of the shielding shell and the DC bus capacitor, which greatly improves the high-frequency performance of the filter circuit and significantly reduces the size of the equipment, making it suitable for medium-power (10kVA-100kVA) industrial harmonic control scenarios.

[0032] Example 2: Full-port three-stage LCL active power filter Based on Example 1, this embodiment further enhances the suppression of conducted interference and is suitable for high-power (100kVA-500kVA) new energy photovoltaic and wind power grid connection scenarios (with stringent electromagnetic compatibility requirements).

[0033] Port filtering suppression network optimization: At the three-phase AC power input / output interface of the integrated electromagnetic shielding housing 1, a three-phase differential mode and common mode filter inductor 3 is embedded by molding process. This inductor, together with the bridge arm inductor and filter capacitor of the subsequent stage, forms a complete three-stage LCL filter network. The cutoff frequency of the filter network is designed to be 500kHz, and the conducted interference suppression rate of 20KHz-1MHz is ≥80%.

[0034] Enhanced shielding continuity: The metal shell of the three-stage LCL filter network and the integrated electromagnetic shielding shell 1 are laser-welded to achieve a 360° seamless conductive connection without any splicing gaps, ensuring the continuity of the shielding effect; all high-voltage input and output lines pass through this filter network, realizing source suppression of conducted interference.

[0035] Signal port processing: Miniature common-mode chokes and feedthrough capacitors are integrated at the RS485, CAN and other signal interfaces on the housing to suppress conducted interference on the signal lines and prevent external interference from entering the control board 2 through the signal lines, thus ensuring the accuracy of high-speed signal processing of the DSP.

[0036] This embodiment can effectively suppress strong conducted interference generated by high-power APF, meet the electromagnetic compatibility standard for grid connection of new energy (GB / T37431-2019), and maintain the integrated characteristics of the equipment.

[0037] Example 3: Frequency-selective absorption active power filter This embodiment, based on embodiment 1, enhances the suppression of radiated interference and is suitable for harmonic control scenarios around communication base stations and precision electronic equipment (where the requirements for radiated interference are extremely high).

[0038] Frequency-selective electromagnetic wave processing structure: On the inner side of the side and top plates of the integrated electromagnetic shielding shell 1, a ferrite electromagnetic wave absorbing material with a thickness of 1mm is applied using a coating process. This material is designed for interference signals at 20KHz, 40KHz, and 60KHz (APF switching frequency and its 2nd and 3rd harmonics), with an absorption rate of ≥90%; and a penetration rate of ≥85% for the 8-14μm thermal radiation frequency band. While effectively absorbing high-frequency radiation interference, it does not affect the natural heat dissipation of the equipment.

[0039] Internal electromagnetic crosstalk suppression: A metal partition extending from the shielding shell is set between the control board 2 and the IGBT power board. The same frequency-selective electromagnetic wave absorbing material is attached to the inner surface of the partition to suppress the crosstalk of the strong interference of the power board to the control board 2 and ensure the working stability of the control board 2.

[0040] Grounding optimization: A dedicated grounding terminal is installed at the bottom of the casing. The grounding terminal is directly connected to the internal grounding copper busbar. During on-site installation, a dedicated grounding cable is used to connect to the grounding grid. The grounding resistance is ≤4Ω, which further guides the residual interference to the ground.

[0041] This embodiment can achieve directional and efficient absorption of radiated interference in a specific frequency band. The equipment's radiated interference meets the CLASSA level standard of GB / T17626.3-2018 and is suitable for application scenarios with sensitive electromagnetic environments.

[0042] Example 4: like Figure 1 As shown, an active power filter with electromagnetic shielding includes: an active power filter circuit module; and an integrated electromagnetic shielding housing 1 for accommodating and shielding the active power filter circuit module. At least one structural part of the integrated electromagnetic shielding housing 1 is combined with the circuitry of the active power filter circuit module to form a functional filtering electrical component. The integrated electromagnetic shielding housing 1, in conjunction with the circuitry, forms a comprehensive electromagnetic shielding system that integrates source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding.

[0043] The functional filtering electrical component is a capacitor, which is composed of the conductive part of the inner wall of the integrated electromagnetic shielding shell 1, the insulating dielectric layer 4, and the conductive pattern on the printed circuit board of the active power filtering circuit module; the capacitor is a flat DC bus support capacitor, which has the characteristics of large capacity and low equivalent series inductance.

[0044] All AC power inlets and outlets, signal interfaces, and grounding interfaces of the integrated electromagnetic shielding housing 1 are equipped with integrated filtering and suppression network components to block the leakage and intrusion of conducted electromagnetic interference from the physical ports.

[0045] The filtering suppression network component includes three-phase differential-mode and common-mode filter inductors 3. The inductors, together with the bridge arm inductors and filter capacitors of the subsequent stage, form a complete three-stage LCL filter network. The metal shell of the filtering suppression network component maintains a 360° seamless conductive connection with the integrated electromagnetic shielding shell 1 to ensure shielding continuity. All high-voltage input and output lines and signal lines pass through the filtering suppression network component.

[0046] The inner surface of the integrated electromagnetic shielding shell 1 is provided with a frequency-selective electromagnetic wave processing structure. The structure is a frequency-selective surface or an electromagnetic wave absorbing material layer, which performs directional absorption / reflection of specific frequency band interference generated by the switching frequency of the active power filter 20KHz and its harmonics, and maintains high penetration rate for the thermal radiation frequency band required for heat dissipation.

[0047] The IGBT heat dissipation module and substrate of the active power filter circuit module are reliably electrically and thermally connected to the integrated electromagnetic shielding housing 1, so that the housing can also serve as a heat dissipation channel, thereby achieving synergistic optimization of electromagnetic shielding and thermal management; the integrated electromagnetic shielding housing 1 is made of aluminum alloy with high conductivity and high thermal conductivity, or is made of composite metal and non-metal materials.

[0048] The splicing joints of the integrated electromagnetic shielding shell 1 adopt a dual connection structure of conductive adhesive sealing and metal buckle pressing. A conductive gasket is set between the door and the main body of the shell to eliminate electromagnetic leakage points at the splicing gaps.

[0049] The inner wall of the integrated electromagnetic shielding housing 1 is also provided with a grounding copper busbar. The grounding copper busbar is equipotentially connected with the grounding terminal of the filter circuit module and the conductive part of the housing, suppressing electromagnetic reflection and crosstalk inside the housing and forming an internal electromagnetic shielding grounding system.

[0050] like Figure 2 As shown, the electromagnetic shielding method of the electromagnetic shielding system, which combines source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding, includes the following steps: S1. Interference Source Suppression: The structural part of the integrated electromagnetic shielding shell 1 is integrated with the active power filter circuit module and designed as a functional filter electrical component, so that the shielding shell actively participates in the filtering function, weakening the strength of the interference signal from the source of electromagnetic interference; breaking the traditional design of shielding and filtering being separated, the structural part of the integrated electromagnetic shielding shell 1 is directly designed as a functional filter electrical component of the APF main circuit, weakening the energy of the electromagnetic interference signal from the source of interference, and eliminating the strong radiation / conduction basis of the interference source.

[0051] Specifically, firstly, the inner surface of the base plate of the integrated electromagnetic shielding housing 1 is precision milled to form a regular electrode pattern. The area S of the electrode pattern is determined according to the rated power P of the APF. n (Unit: kVA), DC bus voltage U d (Unit: V) Design to meet the capacitor design formula: C=2P n ×10 3 / (f s ×∆U d / U d ); where f s为 (APF switching frequency is 20kHz), ∆U d / U d The DC bus voltage fluctuation rate is taken as 5%-10%, and 8% is selected for industrial grade; the effective area of ​​the capacitor plates simultaneously satisfies: C=ε r ε0S / d; where ε r The relative permittivity of insulating dielectric layer 4 (polyimide ε) r =3.0-3.5), ε0 is the vacuum permittivity (8.85×10⁻⁶). -12 F / m), d is the thickness of the insulating dielectric layer 4 (0.1-0.3mm); S is the plate area (unit: m²). 2 Secondly, an insulating dielectric layer 4 of thickness d is laid on the surface of the electrode pattern on the bottom plate of the processed housing, ensuring that the dielectric layer is undamaged, free of bubbles, and has a dielectric strength ≥20kV / mm. Finally, the IGBT power board of the APF is directly fixed on top of the insulating dielectric layer 4, so that the large copper-clad layer on the power board and the electrode pattern on the bottom plate of the housing form the two poles of a planar capacitor. Tight contact is ensured by bolt pressing, ultimately forming a large-capacity DC bus support capacitor with low equivalent series inductance (ESL≤5nH).

[0052] If the APF is a high-power type (P) n (≥100kVA), the side / top plate of the integrated electromagnetic shielding shell 1 is designed as the core auxiliary structure of the filter inductor 3, which together with the internal conventional filter inductor 3 forms a distributed parameter LCL filter circuit, the distributed inductor L s The design meets: Ls =U d ×∆I / 2πf s I n Where ∆I is the inductor current ripple (take the rated current I). n (10%-15%), I n The rated output current of the ADF (in A); supplemented by the distributed inductance of the housing structure, the cutoff frequency f of the LCL filter circuit is made more efficient. c Satisfy: f s / 10<f c <f s / 2, to achieve source filtering of switching frequency interference.

[0053] S2. Propagation Path Blocking: A closed electromagnetic shielding space is formed through the high conductivity structure of the integrated electromagnetic shielding shell 1. The shell splicing joints adopt a double conductive sealing structure, and the inner wall is equipped with an equipotential grounding copper busbar to block the crosstalk of interference signals inside the shell and the radiation propagation to the outside. Specifically, this step constructs a closed electromagnetic shielding space through shell structure optimization and equipotential grounding design to block the crosstalk of electromagnetic interference inside the shell and the radiation propagation to the outside, laying the structural foundation for subsequent shielding steps. The splicing joints (bottom plate, side plate, top plate) of the integrated electromagnetic shielding shell 1 adopt a double connection method of conductive adhesive sealing + metal buckle pressing. The conductivity of the conductive adhesive is ≥1×10ˆ5S / m, and the pressing force of the metal buckle is ≥50N, ensuring that the electromagnetic shielding effectiveness of the splicing gap is ≥60dB (20KHz-1MHz frequency band).

[0054] If the housing design includes an access door, a beryllium copper conductive gasket is installed on the contact surface between the door and the housing body. The compression of the gasket is controlled at 20%-30%, achieving a seamless 360° conductive connection between the door and the housing, eliminating electromagnetic leakage from gaps in the door. A copper grounding busbar is laid on the inner wall of the integrated electromagnetic shielding housing 1, with a cross-sectional area ≥10mm². 2 The node spacing of the grounding copper busbar is ≤10cm to ensure that the potential difference between any two points inside the casing is ≤5mV.

[0055] The grounding copper busbar and all grounding terminals of the APF filter circuit module (IGBT power board, control board 2, power board, heat sink) and the conductive parts of the integrated electromagnetic shielding housing 1 are equipotentially welded. A dedicated grounding terminal is set at the bottom of the housing, and the grounding terminal is directly connected to the internal grounding copper busbar, providing a standardized interface for subsequent field grounding and ensuring that residual interference can be effectively introduced into the ground.

[0056] S3. Specific Frequency Band Absorption: A frequency-selective electromagnetic wave processing structure is set on the inner surface of the shielding shell to directionally absorb / reflect high-frequency interference signals of the APF switching frequency and its harmonics, without affecting the heat radiation heat dissipation of the equipment. Specifically, directional electromagnetic processing is performed on the characteristic interference frequency band of the APF (20KHz switching frequency and its 2nd, 3rd, and nth harmonics). By setting a frequency-selective electromagnetic wave processing structure on the inner surface of the shell, efficient absorption / reflection of the interference frequency band is achieved, while ensuring the penetration of the heat radiation frequency band required for heat dissipation, thus balancing shielding and heat dissipation. Ferrite-based frequency-selective electromagnetic wave absorbing material, targeting the characteristic interference frequency band of the APF f0 (20KHz-1MHz), has a complex permeability μ. r =μ´-jμ´´、 Complex permittivity ε r =ε´-jε´ satisfies the impedance condition Z=(jωμ0μ r / jωε0ε r ) 1 / 2 =Z0; Z0 is the free-space wave impedance (377Ω), ω=2πf0 is the angular frequency; the absorbing thickness t of the material satisfies: t=c / (4f0( )); where c is the speed of light (3×10 8 (m / s); the thickness t of the APF absorbing material meets the requirement of 0.8-1.2mm. Electromagnetic wave absorbing material layers are applied to the inner sides of the side and top plates of the integrated electromagnetic shielding housing 1, and on the surface of the metal partition between the IGBT power board and the control board 2, using high-temperature adhesive bonding or spraying processes.

[0057] During construction, ensure that the material layer is wrinkle-free and does not peel off, and that the adhesion rate with the inner wall of the shell is ≥99%. For irregular structures such as grooves and electrode patterns in the shell, adopt customized material cutting to ensure full coverage of frequency band processing.

[0058] S4. Full-Port Sealed Suppression: A unified integrated filter suppression network component is incorporated into all power, signal, and ground ports within the housing to suppress conducted interference at its source, eliminating electromagnetic leakage and external interference intrusion at the ports. Specifically, a sealed filter design is implemented for all electrical ports of the APF (AC power input / output ports, signal interfaces, and ground interfaces). Through the integrated filter suppression network component, leakage of conducted electromagnetic interference and intrusion of external interference are physically prevented at the ports, achieving source suppression of conducted interference. For the APF three-phase AC power input / output ports, based on the rated current I... n Design a three-phase differential mode inductor L d Common mode inductor L c The parameters satisfy: Differential mode inductance: L d =(U ac ×k) / (2πf s 1×I n ); U acLet L be the phase voltage of the power grid, and k be the voltage ripple factor, ranging from 0.01 to 0.03. Common-mode inductance: L c =(U cm ×10 3 ) / (2πf s 1×I cm ); U cm I is the common-mode voltage limit. cm This represents the common-mode current limit. The three-phase differential-mode inductor, common-mode inductor, subsequent APF bridge arm inductor, and filter capacitor are integrated to form a complete three-stage LCL filter network. The cutoff frequency of the filter network is f. c Satisfy: f c =1 / (2π((L d +L 桥壁 C 滤波） 1 / 2 );f c Satisfy: 500Hz < f c <5kHz; A three-stage LCL filter network is integrated into the power port of the integrated electromagnetic shielding housing 1 via molding or embedded installation. The metal shell of the filter network and the housing are seamlessly connected by laser welding at 360°. All high-voltage input and output lines must pass through this filter network, with no exposed wiring. For the RS485, CAN, analog signal interfaces of the APF, a combined filter component of a rod filter and a miniature common-mode choke is integrated. The inductance value of the common-mode choke is based on the signal frequency f. s The design uses an IG filter (10-100mH for low-frequency signals and 1-10mH for high-frequency signals). The cutoff frequency of the rod filter is ≥10 times the signal frequency to ensure that interference is suppressed without affecting normal signal transmission. At the dedicated grounding terminal of the housing, a grounding inductor Lj (10-50μH) is connected in series and a filter capacitor Cj (0.1-1μF) is connected in parallel to form an LC filter circuit. This prevents interference from the external power grid from entering the housing through the grounding terminal, while simultaneously suppressing interference from inside the housing from leaking to the power grid through the grounding terminal.

[0059] S5. Thermal Screen Collaborative Optimization: The heat-generating components of the filter circuit module are reliably thermally connected to the shielding housing. The large heat dissipation area of ​​the housing achieves efficient heat dissipation, while the conductive structure of the housing maintains shielding integrity, preventing the heat dissipation design from compromising the shielding effect. Specifically, the heat-generating components of the APF are reliably thermally connected to the integrated electromagnetic shielding housing 1, allowing the housing to also serve as a heat dissipation channel. This ensures efficient heat dissipation while maintaining electromagnetic shielding integrity, preventing device aging and increased interference caused by excessive temperature rise. The core heat-generating components of the APF (IGBT, filter inductor 3, heat sink module) are thermally bonded to the base / side plate of the integrated electromagnetic shielding housing 1. High thermal conductivity silicone (≥5W / (m・K)) is applied between the bonding surfaces, with the silicone thickness controlled at 0.1-0.2mm, ensuring that the thermal resistance Rt satisfies: Rt≤∆T / Ph; ∆T is the allowable temperature rise of the heat-generating component, P... h This represents the heat dissipation of the heating element, measured in watts (W).

[0060] Heat dissipation fins 5 are designed on the outer surface of the integrated electromagnetic shielding shell 1. The area Sr of the heat dissipation fins 5 is determined according to the total heat dissipation of the APF (unit: W): Sr ≥ Ph_total / K∆Tmax; K is the heat dissipation coefficient of the problem, and K satisfies 5-8 W / (m²). 2 ·℃); ∆T max This represents the maximum permissible temperature difference between the casing and the environment. The spacing of the heat dissipation fins 5 is controlled at 10-15mm to avoid air convection obstruction caused by excessively small fin spacing, thereby improving natural heat dissipation efficiency. For high-power APFs, a cooling fan can be integrated into the casing, with the fan's airflow matched to the total heat dissipation to achieve air cooling.

[0061] The functional filtering electrical component mentioned in step S1 is a flat DC bus support capacitor or a filter inductor 3. The capacitor is composed of a conductive part on the inner wall of the shielding shell, an insulating dielectric layer 4, and a conductive pattern on the circuit board. The inductor is composed of a specific structure of the shielding shell and an internal filter inductor 3 to form a distributed parameter LCL filter circuit.

[0062] The filtering and suppression network components described in step S4 are designed to match the port type. The power port uses a three-stage LCL filter network, the signal port uses a combination structure of a rod filter and a common-mode choke, and the ground port uses a combination structure of a grounding inductor and a filter capacitor.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An active power filter with electromagnetic shielding, characterized in that, include: Active power filter circuit module; An integrated electromagnetic shielding housing (1) is used to house and shield the active power filter circuit module; wherein at least one structural part of the integrated electromagnetic shielding housing (1) is combined with the circuit of the active power filter circuit module to form a functional filtering electrical component; the integrated electromagnetic shielding housing (1) together form a full-dimensional electromagnetic shielding system with source suppression, path blocking, frequency band absorption, port sealing and thermal shielding cooperation.

2. The active power filter with electromagnetic shielding according to claim 1, characterized in that, The functional filtering electrical component is a capacitor, which is composed of the conductive part of the inner wall of the integrated electromagnetic shielding shell (1), the insulating dielectric layer (4), and the conductive pattern on the printed circuit board of the active power filtering circuit module; the capacitor is a flat DC bus support capacitor with the characteristics of large capacity and low equivalent series inductance.

3. The active power filter with electromagnetic shielding according to claim 1, characterized in that, All AC power inlets and outlets, signal interfaces and grounding interfaces of the integrated electromagnetic shielding housing (1) are equipped with integrated filtering and suppression network components to block the leakage and intrusion of conducted electromagnetic interference from the physical ports.

4. An active power filter with electromagnetic shielding according to claim 3, characterized in that, The filtering suppression network component includes a three-phase differential mode and common mode filter inductor (3). The inductor, together with the bridge arm inductor and filter capacitor of the subsequent stage, forms a complete three-stage LCL filter network. The metal shell of the filtering suppression network component is seamlessly connected to the integrated electromagnetic shielding shell (1) at 360° to ensure shielding continuity. All high voltage input and output lines and signal lines pass through the filtering suppression network component.

5. An active power filter with electromagnetic shielding according to claim 1, characterized in that, The inner surface of the integrated electromagnetic shielding shell (1) is provided with a frequency-selective electromagnetic wave processing structure, which is a frequency-selective surface or an electromagnetic wave absorbing material layer. It performs directional absorption / reflection of specific frequency band interference generated by the switching frequency of the active power filter 20KHz and its harmonics, and maintains high penetration rate for the thermal radiation frequency band required for heat dissipation.

6. An active power filter with electromagnetic shielding according to claim 1, characterized in that, The IGBT heat dissipation module and substrate of the active power filter circuit module are reliably electrically and thermally connected to the integrated electromagnetic shielding shell (1), so that the shell can also serve as a heat dissipation channel, thereby achieving synergistic optimization of electromagnetic shielding and thermal management; the integrated electromagnetic shielding shell (1) is made of aluminum alloy with high conductivity and high thermal conductivity, or is made of metal-nonmetal composite material.

7. An active power filter with electromagnetic shielding according to any one of claims 1-6, characterized in that, The splicing joint of the integrated electromagnetic shielding shell (1) adopts a dual connection structure of conductive adhesive sealing + metal buckle pressing. A conductive pad is set between the door of the shell and the main body to eliminate electromagnetic leakage points at the splicing gap.

8. An active power filter with electromagnetic shielding according to claim 1, characterized in that, The inner wall of the integrated electromagnetic shielding shell (1) is also provided with a grounding copper busbar. The grounding copper busbar is connected to the grounding terminal of the filter circuit module and the conductive part of the shell at the same potential, suppressing electromagnetic reflection and crosstalk inside the shell and forming an internal electromagnetic shielding grounding system.

9. An active power filter with electromagnetic shielding according to claim 1, characterized in that, The electromagnetic shielding method of the electromagnetic shielding system, which combines source suppression, path blocking, frequency band absorption, port sealing, and thermal shielding, includes the following steps: S1. Suppression of interference source: The structural part of the integrated electromagnetic shielding shell (1) is integrated with the active power filter circuit module and designed as a functional filter electrical component, so that the shielding shell actively participates in the filtering function and weakens the strength of the interference signal from the source of electromagnetic interference. S2, Propagation path blocking: A closed electromagnetic shielding space is formed by the high conductivity structure of the integrated electromagnetic shielding shell (1). The shell splicing adopts a double conductive sealing structure, and the inner wall is equipped with an equipotential grounded copper busbar to block the crosstalk of interference signals inside the shell and the radiation propagation to the outside. S3. Specific frequency band absorption: A frequency-selective electromagnetic wave processing structure is set on the inner surface of the shielding shell to directionally absorb / reflect high-frequency interference signals of the APF switching frequency and its harmonics, without affecting the heat radiation heat dissipation of the equipment. S4. Full-port sealed suppression: The filter suppression network components are integrated into all power, signal and ground ports of the housing to suppress conducted interference at the source and prevent electromagnetic leakage and external interference from entering the ports. S5. Thermal Screen Collaborative Optimization: The heat-generating components of the filter circuit module are reliably thermally connected to the shielding housing, utilizing the large heat dissipation area of ​​the housing to achieve efficient heat dissipation. At the same time, the conductive structure of the housing maintains the integrity of the shielding, avoiding damage to the shielding effect by the heat dissipation design.

10. An active power filter with electromagnetic shielding according to claim 9, characterized in that, The functional filtering electrical component mentioned in step S1 is a flat DC bus support capacitor or a filter inductor (3). The capacitor is composed of a conductive part of the inner wall of the shielding shell, an insulating dielectric layer (4), and a conductive pattern on the circuit board. The inductor is composed of a specific structure of the shielding shell and an internal filter inductor (3) to form a distributed parameter LCL filter circuit.

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