Harmonic wave and voltage fluctuation self-adaptive adjusting circuit of photovoltaic grid-connected inverter

Abstract

The utility model relates to the technical field of electric energy control of a photovoltaic grid-connected inverter, in particular to a photovoltaic grid-connected inverter harmonic wave and voltage fluctuation self-adaptive adjusting circuit, which comprises a harmonic wave sensing module, a digital processing module, a dynamic filtering module and a voltage compensation module. The harmonic sensing module obtains harmonic information through the low-frequency-intermediate-frequency-high-frequency series mutual inductor, and the digital processing module analyzes the harmonic information in real time and outputs a dispatching instruction. The dynamic filtering module performs millisecond-level switching among four groups of filtering channels through a magnetic latching relay and a field-effect tube array, so as to realize on-demand input of fifth harmonic wave trapping, high-frequency pi-type filtering, damping filtering and negative sequence compensation; the voltage compensation module injects compensation voltage through a three-phase IGBT bridge arm, and the output end suppresses residual high-frequency interference through an electromagnetic band gap filter and a ferrite magnetic ring. According to the scheme, harmonic detection, filtering reconstruction and voltage stabilization are integrated in the same hardware, and the problems of frequency band blind areas, response lag and high voltage fluctuation compensation cost are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of electric energy control of photovoltaic grid-connected inverters, in particular to a harmonic and voltage fluctuation adaptive regulation circuit of photovoltaic grid-connected inverters. Background Art

[0002] With the rapid increase in distributed photovoltaic penetration, the power level and switching frequency of grid-connected inverters are rising simultaneously. This leads to severe coupling between the low-frequency, medium-frequency, high-frequency, and negative-sequence harmonics in the output current. Traditional fixed-topology LCL, LC, or single-tuned filters cannot simultaneously account for wide bandwidth, variable loads, and parameter drift caused by ambient temperature drift, resulting in a decrease in filtering depth with operating conditions. Furthermore, time-varying grid impedance causes voltage fluctuations at the grid connection point, making conventional PI or PR control unable to reconstruct compensation commands in real time. This requires additional AVR / SVG equipment, doubling system size, cost, and communication complexity. Therefore, an integrated solution is urgently needed that can identify harmonic characteristics online and perform dynamic filtering and voltage compensation within the same hardware architecture to improve grid-connected photovoltaic power quality and reduce overall costs.

[0003] Existing grid-connected inverter harmonic control relies primarily on multiple independent filters and a centralized DSP sampling architecture. Common current transformers only cover the power frequency or switching frequency bands, missing high-frequency and negative-sequence components, resulting in blind spots in feature domain identification. The filter network parameters used are fixed and cannot automatically switch based on harmonic energy distribution, resulting in overdamping under light loads and underdamping under heavy loads. Voltage fluctuation compensation requires an external DC-DC branch, resulting in a long control chain and slow response. The relay, IGBT drive, and sampling chain lack transient suppression, making secondary resonance easily introduced during switching. EMI suppression at the relay output uses a single common-mode inductor, but high-frequency spikes can still couple through the ground wire. These deficiencies make it difficult for the system to simultaneously meet grid-connected standards for total harmonic distortion and voltage fluctuation under wide-power, wide-bandwidth, and highly variable grid conditions. Utility Model Content

[0004] The purpose of the utility model is to provide a photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit to solve the problems of frequency band blind spots, response lag and high voltage fluctuation compensation cost of fixed filters in the prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present utility model is to include a harmonic sensing module, a digital processing module, a dynamic filtering module, and a voltage compensation module which are electrically connected in sequence;

[0006] The current transformer group includes a low-frequency current transformer, a medium-frequency current transformer, and a high-frequency current transformer coupled in series; the secondary coil output end of the low-frequency current transformer is connected to the primary coil input end of the medium-frequency current transformer, and the secondary coil output end of the medium-frequency current transformer is connected to the primary coil input end of the high-frequency current transformer;

[0007] The output end of the secondary coil of the high-frequency current transformer is connected in series with a sampling resistor and then connected to the non-inverting input end of the differential amplifier.

[0008] The above technical solution is adopted, in which the current transformer group includes a low-frequency current transformer, a medium-frequency current transformer and a high-frequency current transformer coupled in series; the secondary coil output end of the low-frequency current transformer is connected to the primary coil input end of the medium-frequency current transformer, and the secondary coil output end of the medium-frequency current transformer is connected to the primary coil input end of the high-frequency current transformer; the secondary coil output end of the high-frequency current transformer is connected in series with a sampling resistor and then connected to the non-inverting input end of the differential amplifier.

[0009] The above technical solution is adopted. In the multi-channel switching circuit of this solution, the first drive coil of the double-contact magnetic latching relay is connected in series with the first switch tube and then connected to the positive voltage source, and the second drive coil is connected in series with the second switch tube and then connected to the negative bias voltage source.

[0010] The above technical solution is adopted. In this solution, the dynamic filtering module also includes a field effect tube array and four groups of filtering channels. The gate of the field effect tube array is connected to the output end of the driving circuit through a transient suppression diode. The four groups of filtering channels include:

[0011] The first filter channel is provided with a fifth harmonic trap circuit, including a series resonance of an inductor and a capacitor;

[0012] The second filter channel is arranged with a high-frequency π-type filter circuit, including a ferrite magnetic ring and a polypropylene capacitor;

[0013] The third filter channel is provided with a damping filter circuit, including an operational amplifier and an adjustable capacitor array;

[0014] The fourth filtering channel is provided with a negative sequence compensator, including a full-bridge inverter circuit.

[0015] The above technical solution is adopted, in which the adjustable capacitor array includes four thin film capacitors connected in parallel, and each capacitor branch is connected in series with a metal oxide semiconductor field effect transistor;

[0016] The DC bus of the full-bridge inverter circuit is connected in parallel with a film capacitor group, and a varistor is connected across the positive and negative poles.

[0017] The above technical solution is adopted, in which an electromagnetic bandgap filter is embedded in the output end of the voltage compensation module, and the electromagnetic bandgap filter includes a copper foil unit and a multi-layer dielectric substrate.

[0018] The above technical solution is adopted, in which the signal output line of the electromagnetic bandgap filter is wound around a ferrite ring, and both ends of the secondary winding of the ferrite ring are grounded through a copper foil shielding layer.

[0019] Due to the adoption of the above technical solution, the present invention has achieved the following technical advancements compared to the prior art:

[0020] This technical solution cascades the primary and secondary coils of low-, medium-, and high-frequency current transformers, eliminating signal crosstalk in the frequency band overlap region of traditional parallel current transformers and significantly improving spectrum coverage. A differential sampling link accurately captures ultra-low-frequency interharmonics and high-frequency EMI noise. A digital processing module reconstructs the filter path in real time based on energy distribution. A magnetic latching relay coupled with a field-effect transistor array achieves microsecond channel switching, preventing overdamping under light loads and underdamping under heavy loads. The voltage compensation module's three-phase IGBT bridge legs directly embed the voltage compensation algorithm, eliminating additional DC-DC branches and effectively reducing circuit production costs. The output of the voltage compensation unit incorporates a copper foil-dielectric substrate laminate structure, enabling high-frequency oscillation suppression earlier in the energy transmission process, improving high-frequency noise attenuation and reducing output voltage compensation delay. Through the innovative design of a series transformer group, a dynamic switching architecture for magnetic latching relays, and an electromagnetic bandgap filter, this circuit effectively reduces the total harmonic distortion (THD) of the voltage output signal in photovoltaic systems, achieving efficient voltage fluctuation suppression and providing a low-cost, reliable solution for high-penetration photovoltaic grid-connected systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 This is a schematic diagram of the structure of the photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit of the present utility model;

[0023] Figure 2 This is a flow chart of the triggering action of the first filter channel of the present invention;

[0024] Figure 3 This is a flow chart of the triggering action of the second filtering channel of the present invention;

[0025] Figure 4 This is a flow chart of the triggering action of the third filtering channel of the present invention;

[0026] Figure 5 This is a flow chart of the triggering action of the fourth filtering channel of the present invention.

[0027] In the figure: 1. Harmonic sensing module; 2. Digital processing module; 3. Dynamic filtering module; 31. First filtering channel; 32. Second filtering channel; 33. Third filtering channel; 34. Fourth filtering channel; 4. Voltage compensation module. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the embodiments:

[0029] Example 1

[0030] like Figure 1-Figure 5 As shown, the utility model provides a photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit, including a harmonic sensing module 1, a digital processing module 2, a dynamic filtering module 3, and a voltage compensation module 4 electrically connected in sequence;

[0031] The harmonic sensing module 1 includes a differential amplifier, an analog-to-digital converter and a current transformer group, which is used to capture the low-frequency, medium-frequency, high-frequency and negative-sequence four-dimensional harmonic components of the grid-connected current in real time and convert them into voltage signals with a high signal-to-noise ratio.

[0032] The current transformer group includes a low-frequency current transformer, a medium-frequency current transformer and a high-frequency current transformer coupled in series; the secondary coil output end of the low-frequency current transformer is connected to the primary coil input end of the medium-frequency current transformer, and the secondary coil output end of the medium-frequency current transformer is connected to the primary coil input end of the high-frequency current transformer; the secondary coil output end of the high-frequency current transformer is connected in series with a sampling resistor and then connected to the non-inverting input end of the differential amplifier.

[0033] In this embodiment, the current transformer group adopts a three-stage series coupling structure: the low-frequency current transformer's core is made of DW540-50 silicon steel sheet, with a primary coil wire diameter of 2mm and a secondary coil wire diameter of 0.5mm. The secondary coil output is directly connected to the primary coil input of a medium-frequency current transformer (with a core made of FT-3M nanocrystalline and dimensions of Φ40mm x 20mm). The secondary coil output of the medium-frequency current transformer is connected to the primary coil input of a high-frequency current transformer (with a core made of 1J85 Permalloy and a bandwidth of 150kHz). The secondary coil of the high-frequency current transformer is connected in series with a 50mΩ / 5W precision sampling resistor made of J-type manganese-copper alloy. The sampling resistor is connected to the non-inverting input of a differential amplifier via a shielded twisted pair cable. The differential amplifier is an INA188 with a common-mode rejection ratio of 120dB and a gain of 25. The output of the differential amplifier is connected in parallel with a SMAJ15A TVS diode for surge protection. The output of the differential amplifier is directly connected to the analog-to-digital converter (ADC) via a pin header. The ADC uses the ADS8668, which features 16-bit resolution, a 250kSPS sampling rate, and a ±10V input range. This module utilizes a three-stage series transformer design to expand the harmonic detection frequency band to 10Hz-150kHz (within ±3dB of fluctuation), addressing the frequency blind spots associated with traditional single-transformer designs.

[0034] The digital processing module 2 includes an embedded processor and a programmable logic device, which is used to extract harmonic features, sort energy and generate PWM compensation instructions for the sampled data, and realize millisecond-level reconstruction of the filter channel and voltage compensation.

[0035] In this embodiment, the embedded processor is an STM32H743 with a main frequency of 400MHz. Its PA0-PA15 pins are connected to the programmable logic device (PLD) via a 32-bit parallel bus (0.2mm line width, ±5mil equal length tolerance). The PLD is an XC7A50T-2FTG256I. The digital output of the analog-to-digital converter is connected to I / O Bank 14 of the PLD via a 40-pin socket. The embedded processor has an embedded FFT analysis algorithm that acquires a set of harmonic spectrum data every 10ms. When the fifth harmonic energy exceeds 8%, it sends a channel switching command to the PLD via a GPIO pin. The PLD has built-in state machine control logic with a response delay of <0.5μs and outputs four PWM signals (carrier frequency 20kHz) to dynamic filtering module 3. This module significantly reduces harmonic analysis time compared to traditional solutions, significantly improving response lag.

[0036] The dynamic filtering module 3 includes a multi-channel switching circuit, a field-effect transistor array, and four groups of filtering channels. It is used to switch between multiple groups of filtering topologies at high speed according to the instructions of the digital processing module 2 to eliminate harmonics in the specified frequency band and suppress resonance.

[0037] The multi-channel switching circuit includes a double-contact magnetic latching relay and a drive circuit; the first drive coil of the double-contact magnetic latching relay is connected in series with a first switching tube and then connected to a positive voltage source, and the second drive coil is connected in series with a second switching tube and then connected to a negative bias voltage source; the gate of the field effect transistor array is connected to the output end of the drive circuit through a transient suppression diode.

[0038] The four filter channels include:

[0039] The first filter channel 31 is provided with a fifth harmonic trap circuit, which is composed of an inductor and a capacitor in series resonance;

[0040] The second filter channel 32 is provided with a high-frequency π-type filter circuit, which is composed of a ferrite magnetic ring and a polypropylene capacitor;

[0041] The third filter channel 33 is provided with a damping filter circuit, which is composed of an operational amplifier and an adjustable capacitor array;

[0042] The fourth filtering channel 34 is provided with a negative sequence compensator, which is composed of a full-bridge inverter circuit.

[0043] Among them, the adjustable capacitor array includes four thin film capacitors in parallel, each capacitor branch is connected in series with a metal oxide semiconductor field effect transistor; the DC bus of the full-bridge inverter circuit is connected in parallel with a thin film capacitor group, and a varistor is connected between the positive and negative poles.

[0044] In this embodiment, the core of the dynamic filtering module 3 consists of a multi-channel switching circuit and four filter channels. The multi-channel switching circuit features a dual-contact magnetic latching relay, model TQ2-L2-5V, with a contact capacity of 30A. Its first drive coil (with a DC impedance of 140Ω) is connected in series with an IRF540N MOSFET and then connected to a +15V voltage source. The second drive coil is connected in series with an IRF540N MOSFET and then connected to a -12V bias voltage source. The relay's two sets of normally open contacts are connected to the input / output terminals of the four filter channels. The field-effect transistor array consists of eight AOD4184 MOSFETs connected in parallel. The drains of these transistors are connected in common, and their gates are connected to the drive circuit via a 10Ω current-limiting resistor and an SMBJ15CA bidirectional TVS diode. The optocoupler in the drive circuit is an HCPL-3120.

[0045] The specific structure of the four groups of filter channels is as follows: the first filter channel 31 is equipped with a fifth harmonic trap circuit, which is composed of a 4.7mH power inductor (Sendsilon magnetic ring T106-52) and a 4.3μF CBB capacitor in series resonance; the center frequency is locked to 250Hz±2% (corresponding to the 5th harmonic of the 50Hz fundamental wave), and the 4.7mH inductor and 4.3μF capacitor are used in series resonance to generate an attenuation trap with a depth of ≥40dB, which is specifically used to eliminate the 150Hz-350Hz frequency band harmonics in the output current of the photovoltaic inverter.

[0046] The second filtering channel 32 is a high-frequency π-type filtering circuit, which adopts an EF25 ferrite magnetic ring custom inductor and is matched with two 0.22μF / 1kV polypropylene capacitors (model MKP-X2). The EF25 ferrite magnetic ring (cut-off frequency 1MHz) and the 0.22μF polypropylene capacitor form a low-pass filter with a cut-off frequency of 20kHz, which directionally eliminates high-frequency switching harmonics in the 20kHz-150kHz frequency band.

[0047] The third filter channel 33 is a damping filter circuit, and its operational amplifier model is OPA2188. Its negative feedback loop is connected to an adjustable capacitor array; the adjustable capacitor array is composed of four 22nF / 630V thin-film capacitors in parallel, and each capacitor is connected in series with a 2N7002 MOSFET to achieve on-off control. The adjustable capacitor array is driven by the OPA2188 operational amplifier, and the 1kHz-20kHz mid-frequency band harmonics are suppressed in real time through negative feedback impedance matching. Its damping coefficient can be adjusted online via FPGA, with a step value of 0.1.

[0048] Fourth filter channel 34 is a negative-sequence compensator. A 220μF / 1200V film capacitor bank is connected in parallel to the DC bus of the full-bridge inverter circuit. A V25S385K varistor with a threshold voltage of 385V is connected between the positive and negative electrodes. The full-bridge inverter circuit, controlled by a PWM signal, generates reverse harmonic current, primarily compensating for negative-sequence components in the 0-500Hz low-frequency range, with a phase angle accuracy of ±0.5°.

[0049] When the programmable logic device outputs a high-level signal, the drive circuit completes the switching of the magnetic latching relay contacts within 3ms and simultaneously turns on the MOS array of the corresponding channel, achieving rapid and directional filtering of harmonics in a specific frequency band.

[0050] Four filter channels trigger action flow:

[0051] 1. First Filter Channel 31: Harmonic sensor module 1 detects 250Hz harmonic energy >20%, and the digital processing module makes a decision within 25ms. The programmable logic device outputs a PWM1 signal, driving the IRF540N latching relay's +15V coil, switching the contacts to first filter channel 31. Simultaneously, a PWM3 control signal is sent to turn on eight AOD4184s (total impedance <0.1Ω). The 250Hz harmonic current flows through the series resonant connection of a 4.7mH inductor and a 4.3μF capacitor, achieving 46dB of directional attenuation.

[0052] 2. Second filter channel 32: When the 45kHz switching harmonic amplitude exceeds the fundamental by 15%, the programmable logic device outputs signal PWM2, triggering the relay's -12V coil, switching the contacts to second filter channel 32. PWM4 then sends an enable control signal to MOSFETs 3 and 4. High-frequency harmonics pass through an EF25 magnetic ring and a 0.22μF polypropylene capacitor to form a low-pass filter with a cutoff frequency of 20kHz. The measured attenuation at 45kHz is 40dB.

[0053] 3. Third filter channel 33: When the energy fluctuation of a 10kHz intermediate frequency oscillation exceeds 30%, the programmable logic device PWM1 outputs a 5% low-level signal, and PWM2 outputs a 92% high-level signal, triggering a relay to switch to the third filter channel 33 in a time-sharing manner. PWM3 then turns on four 2N7002 transistors, increasing the adjustable capacitance array to 88nF. The operational amplifier OPA2188 dynamically matches the impedance to 100Ω, and with a damping factor of 0.7, it reduces voltage fluctuations to ±0.8%.

[0054] 4. Fourth filter channel 34: When the phase deviation of the 100Hz negative-sequence component exceeds 5°, PWM1 / PWM2 are reset to zero to maintain channel smoothness. PWM4 outputs a control signal to turn on MOSFETs 1 / 8. The FPGA's BANK1 outputs three compensation PWMs, which are then controlled by the driver circuit to inject a 100Hz reverse current into the IGBT bridge arm. The current amplitude is calculated as the fundamental wave × sinΦ, reducing the negative-sequence distortion.

[0055] The voltage compensation module 4 comprises a three-phase IGBT bridge arm, whose gate is connected to the output of the programmable logic device through a drive circuit. It is used to instantly inject a voltage component with controllable amplitude and phase at the filtered output to offset the voltage fluctuation at the grid connection point caused by changes in grid impedance.

[0056] The output of the voltage compensation module 4 is embedded with an electromagnetic bandgap filter, which is composed of a copper foil unit and a multi-layer dielectric substrate. The signal output line of the electromagnetic bandgap filter is wrapped around a ferrite ring, and the secondary winding of the ferrite ring is grounded through a copper foil shielding layer.

[0057] In this embodiment, the voltage compensation module 4 comprises a three-phase IGBT bridge arm, specifically a SEMiX304GD066HDs model with a withstand voltage of 1200V. Its gate drive pin receives PWM signals from a programmable logic device (PLD) via optical fiber, and the drive circuit uses the 1ED3121MU12H. An electromagnetic bandgap filter is embedded at the output of the IGBT bridge arm. This filter is constructed by alternating hexagonal copper foil elements with a side length of 3.2mm and a thickness of 35μm, laminated with a four-layer FR4 dielectric substrate with a single layer thickness of 0.2mm and a dielectric constant of 4.4, and covered with a double-layer copper foil shield. The three-phase output lines pass through an NX20 ferrite ring with a diameter of 0.5mm and a size of Φ45mm × 20mm. The secondary winding of the ring, consisting of 10 turns, is grounded at both ends through a single point of the copper foil shield. This module controls the IGBT's injection of reverse harmonic current based on the harmonic phase calculated by the digital processing module 2, and cooperates with the electromagnetic bandgap filter to suppress high-frequency conducted interference.

[0058] The overall working process of the whole machine is as follows: the current transformer group captures the full-band harmonic signals, which are input into the digital processing module 2 after differential amplification and analog-to-digital conversion; the embedded processor performs real-time FFT analysis, and when it identifies that a specific harmonic exceeds the standard, it controls the programmable logic device to output a switching instruction; the double-contact magnetic latching relay is connected to the target filter channel under the control of the drive circuit, and the field-effect transistor array is synchronously turned on to establish a low-impedance path; the voltage compensation module 4 generates compensation voltage through the IGBT bridge arm, and the electromagnetic bandgap filter filters out switching noise and outputs pure electrical energy.

[0059] The above generally describes the present invention in detail. However, it is obvious to those skilled in the art that modifications or improvements may be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. Photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit, characterized in that: It includes a harmonic sensing module (1), a digital processing module (2), a dynamic filtering module (3), and a voltage compensation module (4) which are electrically connected in sequence; The harmonic sensing module (1) comprises a differential amplifier, an analog-to-digital converter and a current transformer group, wherein the output end of the current transformer group is connected to the analog-to-digital converter via the differential amplifier; The digital processing module (2) includes an embedded processor and a programmable logic device, wherein the input pin of the digital processing module is connected to the output end of the analog-to-digital converter, and the output pin of the digital processing module is connected to the input end of the programmable logic device; The dynamic filtering module (3) includes a multi-channel switching circuit; the multi-channel switching circuit includes a double-contact magnetic latching relay and a drive circuit; The voltage compensation module (4) comprises a three-phase IGBT bridge arm, the gate of which is connected to the output end of the programmable logic device through the drive circuit.

2. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 1, characterized in that: The current transformer group includes a low-frequency current transformer, a medium-frequency current transformer and a high-frequency current transformer coupled in series; The secondary coil output end of the low-frequency current transformer is connected to the primary coil input end of the medium-frequency current transformer, and the secondary coil output end of the medium-frequency current transformer is connected to the primary coil input end of the high-frequency current transformer; the secondary coil output end of the high-frequency current transformer is connected in series with a sampling resistor and then connected to the non-inverting input end of the differential amplifier.

3. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 1, characterized in that: In the multi-channel switching circuit, the first drive coil of the double-contact magnetic latching relay is connected in series with the first switch tube and then connected to a positive voltage source, and the second drive coil is connected in series with the second switch tube and then connected to a negative bias voltage source.

4. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 1, characterized in that: The dynamic filtering module (3) further comprises a field effect tube array and four groups of filtering channels; The gate of the field effect transistor array is connected to the output end of the driving circuit through a transient suppression diode; The four groups of filtering channels include: The first filter channel (31) is provided with a fifth harmonic trap circuit, including a series resonance of an inductor and a capacitor; The second filter channel (32) is provided with a high-frequency π-type filter circuit, including a ferrite magnetic ring and a polypropylene capacitor; The third filter channel (33) is provided with a damping filter circuit, including an operational amplifier and an adjustable capacitor array; The fourth filtering channel (34) is provided with a negative sequence compensator, including a full-bridge inverter circuit.

5. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 4, characterized in that: The adjustable capacitor array includes four thin film capacitors connected in parallel, and each capacitor branch is connected in series with a metal oxide semiconductor field effect transistor; The DC bus of the full-bridge inverter circuit is connected in parallel with a film capacitor group, and a varistor is connected across the positive and negative electrodes.

6. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 1, characterized in that: An electromagnetic bandgap filter is embedded in the output end of the voltage compensation module (4), and the electromagnetic bandgap filter comprises a copper foil unit and a multi-layer dielectric substrate.

7. The photovoltaic grid-connected inverter harmonic and voltage fluctuation adaptive regulation circuit according to claim 6, characterized in that: The signal output line of the electromagnetic bandgap filter is wound around a ferrite ring, and both ends of the secondary winding of the ferrite ring are grounded through a copper foil shielding layer.

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