High-power filter based on fractional order positive and negative inductor parallel connection and control method

Abstract

The invention provides a high-power filter based on fractional order positive and negative inductor parallel connection and a control method, and the filter comprises a fractional order negative inductor # imgabs0 # and a positive inductor # imgabs1 # which are connected in parallel. The fractional order negative inductor # imgabs2 comprises a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, filter inductors L1 and L2, a filter capacitor Cf, a filter damper Rf, a grounding capacitor Cg, a sampling resistor R, a DC-DC conversion circuit, a self-powered module, an MCU controller, a digital-to-analog converter AD and a sine pulse width modulation module SPWM. According to the scheme, the inductance value and the order of the fractional-order inductor can be changed at will by changing the parameters of the MCU controller, so that the inductance value of the high-power filter with the fractional-order positive and negative inductors connected in parallel is changed, and low cost, small size, high power density and flexible and adjustable order and inductance value of the filter inductor are realized; and the method can be applied to a high-power scene with relatively high harmonic content, and a better filtering effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic converter control and current harmonic suppression, and in particular to a high-power filter based on fractional-order positive and negative inductors in parallel and a control method. Background Art

[0002] In recent years, fractional calculus has been successfully applied in control systems, model identification, circuit systems and other fields due to its inherent flexibility of differentiation and integration. Existing research results show that many physical phenomena in nature have fractional-order characteristics in nature, such as inductance and capacitance are actually fractional-order components. The model obtained by modeling the inductor using fractional-order calculus theory is not only more accurate but also more complete than the integer-order model. In addition, after modeling the inductor using fractional-order calculus, any order can be set, thereby realizing more functions with more degrees of freedom and being applicable to a wider range of application scenarios.

[0003] Fractional-order inductors are the most basic units of fractional-order circuit systems. The construction of their topological structures and the realization of their control methods are the basis for studying fractional-order circuit systems. Currently, there are two main construction methods for fractional-order inductors: single-component construction method and multi-component construction method.

[0004] The single-component construction method, that is, manufacturing fractional-order inductors through process methods, mainly uses electrode surface areas with different fractal structures, high-conductivity materials with different electrolytes, etc. In this implementation method, once the device is packaged, the order and inductance value of the single-component fractional-order inductor are fixed. When the order and inductance of the inductor need to be changed, it needs to be redesigned and manufactured. In addition, this method can only realize fractional-order inductors with an order less than 1, and the application scenarios are very limited.

[0005] The multi-component construction method is composed of passive devices such as resistors and capacitors and active devices such as operational amplifiers and power electronic switching elements. It is mainly divided into three categories: multi-component fractional-order components based on passive devices, multi-component fractional-order components based on operational amplifiers, and multi-component fractional-order components based on power electronic converters. The multi-component fractional-order components based on passive devices and the multi-component fractional-order components based on operational amplifiers use a large number of components and have a very complex circuit structure. The order and inductance of the fractional-order inductor are fixed. When the order and inductance need to be changed, the entire circuit structure needs to be replaced, which is inefficient and costly. At the same time, the use of analog devices such as operational amplifiers makes the circuit model limited to low-power occasions at the milliwatt level, limiting its application in the electrical field. The essence of the multi-component fractional-order component based on power electronic converters is to realize fractional-order inductance by control. Therefore, this method can flexibly change the order and inductance characteristics of the fractional-order inductor by changing the parameters of the controller. At the same time, it can be applied to various power occasions and has broad application prospects. However, the current mature solutions based on power electronic converters mostly show the characteristics of fractional-order inductance for specific frequencies and cannot be applied to filter circuits.

[0006] Inductors are widely used in power systems. However, the current application of traditional inductors has the problems of bulky size, low power density and high cost. In addition, during use, as traditional inductors age and degrade, their device parameters change. Once put into use, they cannot be adjusted in real time, and have poor applicability to load and frequency fluctuations, which reduces the filtering quality. Summary of the invention

[0007] In view of the above problems, the present invention proposes a high-power filter based on fractional-order positive and negative inductors in parallel and a control method. By connecting positive and negative inductors in parallel, the overall inductance value is increased, thereby achieving a better filtering effect. The filter can achieve adjustable order and inductance value of the inductor under different frequencies, solving the problems of increased volume, complex design, inability to arbitrarily adjust order and inductance value, and limited application power level caused by the method of constructing fractional-order inductors using passive components. At the same time, the control method exhibits the inductive reactance characteristics of the inductor in the full frequency band, so it can be applied to the filter circuit.

[0008] On the one hand, the present invention proposes a high-power filter based on fractional-order positive and negative inductors in parallel, including a fractional-order negative inductor and positive inductance The two are in parallel relationship. The positive inductance is the conventional physical inductance. The fractional-order negative inductance is equivalent to a circuit composed of power components, which can show the properties of the fractional-order negative inductance.

[0009] Fractional Negative Inductance Specifically include: a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, filter inductors L1 and L2, and a filter capacitor C f , filter damping R f , grounding capacitance C g , sampling resistor R, DC-DC conversion circuit, self-power supply module, Microcontroller Unit (MCU) controller, digital-to-analog converter AD and sinusoidal pulse width modulation module SPWM, all switching tubes are insulated gate bipolar transistors IGBT.

[0010] The two output ends of the DC-DC conversion circuit, i.e., the DC chopper circuit, are respectively connected to the collector of the first switch tube V1 and the emitter of the third switch tube V3. The first switch tube V1 and the third switch tube V3 are connected in series, and the second switch tube V2 and the fourth switch tube V4 are connected in series. The collector of the second switch tube V2 is connected to one output end of the DC-DC conversion circuit, and the emitter of the fourth switch tube V4 is connected to the other output end of the DC-DC conversion circuit. The emitter of the first switch tube V1 is connected to the collector of the third switch tube V3, the collector of the first switch tube V1 is connected to the collector of the second switch tube V2, the emitter of the second switch tube V2 is connected to the collector of the fourth switch tube V4, and the emitter of the third switch tube V3 is connected to the emitter of the fourth switch tube V4. The gates of the four switch tubes are connected to the gate drive control signal. Both ends of the four switch tubes are connected in parallel with power diodes. The collector of each switch tube is connected to the negative electrode of the diode, and the emitter of each switch tube is connected to the positive electrode of the diode.

[0011] Four switching tubes form a single-phase inverter. In normal operation, the control signal controls the first state that the switch tubes V1 and V4 are turned on at the same time, and the switch tubes V2 and V3 are turned off. The second state is that the switch tubes V1 and V4 are turned off, and the switch tubes V2 and V3 are turned on at the same time. The two states alternate in a cycle, so that the excitation voltage and port current at both ends of ports A and B meet the characteristics of fractional-order negative inductance.

[0012] Filter inductors L1 and L2, filter capacitors C f and filter damping R f Constitute LLC filter circuit, filter damping R f The LLC filter circuit is connected in series with the filter capacitor, and is regarded as a whole, which is responsible for filtering the harmonics introduced by the switch tube. One end of the filter inductor L1 is connected to the emitter of the second switch tube V2, and the other end of the filter inductor L1 is connected to the filter inductor L2 and the filter capacitor C f The other end of the filter inductor L2 is connected to one end of the sampling resistor R, and the other end of the sampling resistor R is connected to an AD digital-to-analog converter, which is used to convert the current between the A and B ports Converted into digital signal, another AD digital-to-analog converter converts the analog voltage signal between A and B ports into digital signal, which is convenient for the MCU controller to process later. f The other end of the filter damping R f Connected, filter damping R f The other end is connected to the collector of the third switch tube V3 and the grounding capacitor C g One end of the filter damping R f The other end of the capacitor C is connected to ground g The other end of the sampling resistor R is grounded, port A is the other end of the sampling resistor R, and port B is the filter damping R in the LLC filter circuit. f At the other end, the output voltage of the single-phase inverter contains more harmonics. The LLC filter circuit is used to filter out these harmonic signals and improve the output power quality.

[0013] The self-powered module obtains power directly from the drain-source end of the switch tube element, charges the capacitor in the self-powered module to store energy, and supplies power to the gate drive circuit of the switch element and the MCU controller. The DC-DC conversion circuit takes power from the DC side bus to obtain the DC voltage U required by the single-phase full-controlled bridge. DC .

[0014] The MCU controller applies the excitation voltage u to the ports A and B of the fractional-order negative inductor. g (t) and the port current i L (t) is sampled to generate a control signal wave of the switch tube in the fractional-order negative inductance circuit.

[0015] The sinusoidal pulse width modulation module SPWM uses a triangular carrier to modulate the control signal wave output by the MCU controller to generate a control signal for controlling the switch tube.

[0016] On the other hand, the present invention provides a control method for a high-power filter based on the above-mentioned fractional-order positive and negative inductors in parallel, the method comprising the following steps:

[0017] Step S1: Determine the filter inductance value according to the power quality requirements of the grid The fractional negative inductance is then calculated and positive inductance The inductance value;

[0018] Step S2: Calculate the order of the fractional-order positive inductor according to the voltage and current in the fractional-order positive inductor, and set the order of the negative inductor to be equal to the order of the positive inductor to obtain the control parameters of the MCU;

[0019] Step S3: Obtain the voltage of the external excitation at both ends of the fractional-order negative inductor ports A and B and port current , and set the fractional negative inductance Internal parameters of auxiliary resistor and the output voltage of the DC-DC converter circuit , generating a gate drive control signal according to a control strategy;

[0020] Step S4: Check whether the filtering result of the positive and negative inductance parallel filter meets the power quality requirements, and further adjust the positive and negative inductance parameters.

[0021] Furthermore, the step S1 specifically includes:

[0022] Determine the filter inductance value according to the grid-connected power quality requirements The fractional negative inductance is then calculated and positive inductance Inductance value, equivalent filter inductance value when inductors are connected in parallel and fractional negative inductance , positive inductance The relationship is: ,in, is the inductance of the fractional negative inductor, is the inductance of the fractional positive inductor. Approaching size When the equivalent inductance after parallel connection is This is equivalent to a huge inductor in the full frequency band. It can replace the traditional large inductor for filtering, and the inductance values ​​of the negative inductor and the positive inductor can be determined according to actual needs.

[0023] Furthermore, the step S2 specifically includes:

[0024] According to the value of fractional negative inductance And the inductance of fractional positive inductance Calculate the inductive reactance of positive and negative inductors in parallel for:

[0025]

[0026] in, is the order of the fractional positive inductance, is the order of the fractional negative inductance, , is the fundamental angular frequency of the excitation voltage across the parallel structure, is the fundamental frequency;

[0027] The voltage-current relationship for a positive inductor is as follows: ,in, is the voltage applied to the positive inductor, is the current in the positive inductor;

[0028] Performing Fourier transform on the voltage-current relationship of positive inductance yields the following relationship:

[0029]

[0030] Taking the logarithm of both sides of the equation, we get the following expression:

[0031]

[0032] According to the above formula, the order of positive inductance is obtained , and set the order of the negative inductance to be equal to the order of the positive inductance, and finally adjust the equivalent inductance of the fractional-order negative inductance so that the overall inductance after parallel connection meets the required inductance.

[0033] Furthermore, the step S3 specifically includes:

[0034] Step S31: Auxiliary resistance in fractional-order negative inductance and the output voltage of the DC-DC converter circuit Satisfies the following relationship:

[0035]

[0036] in, The triangle carrier amplitude used by the sine pulse width modulation module SPWM, , is the amplitude of the external excitation voltage, is the fundamental angular frequency of the external excitation voltage signal, and the voltage proportional coefficient ;

[0037] Step S32: In each sampling period, the voltage of the external excitation at both ends of the fractional-order negative inductance port is measured by the sensor. and port current Perform sampling and input the sampling results into the MCU controller;

[0038] Step S33: Generate a bipolar modulated signal wave in a fractional-order negative inductance topology structure. Without considering the influence of the LLC filter circuit, the mathematical model of the fractional-order negative inductance is expressed as follows:

[0039]

[0040] Where β is the order of the fractional negative inductance, is the inductance of the fractional negative inductor, is the excitation voltage across the fractional-order negative inductor port The frequency domain representation of is the port current Frequency domain representation of ;

[0041] The following relationship exists between the external excitation voltage and port current of the fractional-order negative inductor and the two sides of the sampling resistor:

[0042]

[0043] in, is the filtered voltage signal, R is the sampling resistor, is a fractional differential operator;

[0044] After simplification, we get:

[0045]

[0046] Since the inverter output and the modulation signal have the same phase and proportional amplitude, the signal wave of the MCU controller is:

[0047]

[0048] Among them, the voltage proportionality coefficient , is the amplitude of the triangular carrier, is the output DC voltage of the DC-DC converter circuit, is a fractional-order integral operator, and They are reciprocals of each other.

[0049] The filter inductor in the LLC filter circuit and And filter capacitor Taking this into consideration, the parameters of the components in the fractional-order negative inductance circuit have the following relationship:

[0050]

[0051] in, is the voltage of the filter capacitor branch, is the current in the filter capacitor branch, is the current flowing through the filter inductor The current, is the output voltage of the single-phase inverter, that is, the voltage between the emitter of the second switch tube V2 and the collector of the third switch tube V3;

[0052] Therefore, the signal wave of the MCU controller considering the influence of the LLC filter circuit is obtained. for:

[0053]

[0054] in:

[0055]

[0056] The generation methods of these two signal waves can be determined according to the actual application situation.

[0057] Step S34: the sinusoidal pulse width modulation module SPWM performs sinusoidal pulse width modulation on the signal wave and the local triangular carrier, thereby generating control signals for the four switch devices.

[0058] The present invention has the following beneficial technical effects:

[0059] The present invention proposes a high-power filter and control method based on fractional-order positive and negative inductors in parallel, by changing the parameters of the MCU controller, that is, the inductance value of the fractional-order negative inductor and order , the inductance value and order of fractional-order inductors can be changed arbitrarily, overcoming the shortcomings of traditional fractional-order inductor design methods, such as complex circuit structure, high cost, and fixed order and inductance value that cannot be changed;

[0060] The scheme of the present invention has a large adjustment flexibility in filter inductance and order, and can be adjusted according to the requirements of grid-connected power quality, changes in load and frequency, and changes in equipment parameters, ensuring consistent filtering suppression performance under different working conditions and improving the robustness of the system;

[0061] The solution of the present invention connects the positive inductor and the negative inductor in parallel, and the overall inductive reactance is significantly increased, thereby achieving a better filtering effect. Under the premise of achieving the same filtering effect, the volume of the physical inductor can be reduced, thereby improving the power density and saving costs;

[0062] The power level of the filter of the present invention can be determined according to the actual application occasion, so it can be applied to high-power transmission networks;

[0063] Since the high-power filter of the present invention is a parallel structure, it is convenient to improve the inductor that has been put into use. On the basis of the inductor that has been put into use, an H-bridge equivalent structure with full-band fractional-order negative inductance is connected in parallel to increase the inductance value, thereby achieving a larger inductive reactance and achieving a better filtering effect.

[0064] The solution of the present invention approximates the fractional-order integral operator through the Oustaloup filter, and the user can select the frequency band according to actual needs to achieve response to the full frequency band, so that the fractional-order negative inductor in the present invention exhibits the inductive reactance characteristics of the fractional-order negative inductor in the full frequency band, which is suitable for scenes with high harmonic content. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0066] Figure 1 It is a schematic diagram of the overall structure of a high-power filter based on fractional-order positive and negative inductors in parallel provided by an embodiment of the present invention;

[0067] Figure 2 is a schematic diagram of a specific structure of a fractional-order negative inductor provided by an embodiment of the present invention;

[0068] Figure 3 It is a flow chart of a high-power filter control method based on fractional-order positive and negative inductors in parallel provided by an embodiment of the present invention;

[0069] Figure 4 is a system block diagram of a method for controlling a fractional-order negative inductance ignoring the influence of a filter circuit provided by an embodiment of the present invention;

[0070] Figure 5 is a schematic diagram of a piecewise broken line approximation of an Oustaloup filter provided by an embodiment of the present invention;

[0071] Figure 6 is a system block diagram of a method for controlling a fractional-order negative inductance taking into account the influence of a filter circuit provided in an embodiment of the present invention;

[0072] Figure 7 It is a schematic diagram of extracting and eliminating the DC component of the Oustaloup filter provided by an embodiment of the present invention;

[0073] Figure 8 This is the simulation verification result of the first-order fractional-order negative inductance provided by the embodiment of the present invention under 50Hz excitation;

[0074] Fig. 9 This is a simulation verification result of the first-order fractional-order negative inductance provided by an embodiment of the present invention under 100 Hz excitation;

[0075] Fig.10 This is a simulation verification result of the first-order fractional-order negative inductance provided by an embodiment of the present invention under 300Hz excitation;

[0076] Fig.11 This is a simulation verification result of a 0.9-order fractional-order negative inductor provided by an embodiment of the present invention under 100 Hz excitation;

[0077] Fig.12It is the simulation verification result of the 1.1-order fractional-order negative inductance provided by the embodiment of the present invention under 100 Hz excitation;

[0078] Fig.13 This is a diagram showing the filtering effect of the full-band fractional-order negative inductor provided by an embodiment of the present invention in a multi-harmonic scenario;

[0079] Fig.14 is the measurement result of the harmonic content before filtering provided by the embodiment of the present invention;

[0080] Fig.15 is the measurement result of harmonic content after filtering provided by an embodiment of the present invention;

[0081] Fig.16 This is a diagram showing the effect of increasing the inductive reactance of a high-power filter with a 0.4mH positive inductance and a 0.5mH negative inductance connected in parallel provided by an embodiment of the present invention;

[0082] Fig.17 This is a diagram showing the effect of increasing the inductive reactance of a high-power filter with a 0.4 mH positive inductance and a 0.4 mH negative inductance connected in parallel provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0083] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0084] The present invention provides a high-power filter based on fractional-order positive and negative inductors in parallel and a control method. The overall structure of the high-power filter is as follows: Figure 1 As shown, between port A0 and port B0 is a high-power filter based on fractional-order positive and negative inductors in parallel proposed by the present invention, including fractional-order negative inductors and positive inductance The two are connected in parallel, which can realize high-power full-band filtering function and increase inductive reactance.

[0085] Figure 2 is the fractional negative inductance Structural diagram of fractional negative inductance The H-bridge equivalent topology structure includes: a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, filter inductors L1 and L2, and a filter capacitor C f , filter damping R f , grounding capacitance C g, sampling resistor R, DC-DC conversion circuit, self-power supply module, Microcontroller Unit (MCU) controller, digital-to-analog converter AD and sinusoidal pulse width modulation module SPWM, all switching tubes are insulated gate bipolar transistors IGBT.

[0086] The two output ends of the DC-DC conversion circuit, i.e., the DC chopper circuit, are respectively connected to the collector of the first switch tube V1 and the emitter of the third switch tube V3. The first switch tube V1 and the third switch tube V3 are connected in series, and the second switch tube V2 and the fourth switch tube V4 are connected in series. The collector of the second switch tube V2 is connected to one output end of the DC-DC conversion circuit, and the emitter of the fourth switch tube V4 is connected to the other output end of the DC-DC conversion circuit. The emitter of the first switch tube V1 is connected to the collector of the third switch tube V3, the collector of the first switch tube V1 is connected to the collector of the second switch tube V2, the emitter of the second switch tube V2 is connected to the collector of the fourth switch tube V4, and the emitter of the third switch tube V3 is connected to the emitter of the fourth switch tube V4. The gates of the four switch tubes are connected to the gate drive control signal. Both ends of the four switch tubes are connected in parallel with power diodes. The collector of each switch tube is connected to the negative electrode of the diode, and the emitter of each switch tube is connected to the positive electrode of the diode.

[0087] Four switching tubes form a single-phase inverter. In normal operation, the control signal controls the first state that the switch tubes V1 and V4 are turned on at the same time, and the switch tubes V2 and V3 are turned off. The second state is that the switch tubes V1 and V4 are turned off, and the switch tubes V2 and V3 are turned on at the same time. The two states alternate in a cycle, so that the excitation voltage and port current at both ends of ports A and B meet the characteristics of fractional-order negative inductance.

[0088] Filter inductors L1 and L2, filter capacitors C f and filter damping R f Constitute LLC filter circuit, filter damping R f The LLC filter circuit is connected in series with the filter capacitor, and is regarded as a whole, which is responsible for filtering the harmonics introduced by the switch tube. One end of the filter inductor L1 is connected to the emitter of the second switch tube V2, and the other end of the filter inductor L1 is connected to the filter inductor L2 and the filter capacitor C f The other end of the filter inductor L2 is connected to one end of the sampling resistor R, and the other end of the sampling resistor R is connected to an AD digital-to-analog converter, which is used to convert the current between the A and B ports Converted into digital signal, another AD digital-to-analog converter converts the analog voltage signal between A and B ports into digital signal, which is convenient for the MCU controller to process later. f The other end of the filter damping R f Connected, filter damping R fThe other end is connected to the collector of the third switch tube V3 and the grounding capacitor C g One end of the filter damping R f The other end of the capacitor C is connected to ground g The other end of the sampling resistor R is grounded, port A is the other end of the sampling resistor R, and port B is the filter damping R in the LLC filter circuit. f At the other end, the output voltage of the single-phase inverter contains more harmonics. The LLC filter circuit is used to filter out these harmonic signals and improve the output power quality.

[0089] The self-powered module obtains power directly from the drain-source end of the switch tube element, charges the capacitor in the self-powered module to store energy, and supplies power to the gate drive circuit of the switch element and the MCU controller. The DC-DC conversion circuit takes power from the DC side bus to obtain the DC voltage U required by the single-phase full-controlled bridge. DC .

[0090] The MCU controller applies the excitation voltage u to the ports A and B of the fractional-order negative inductor. g (t) and the port current i L (t) is sampled to generate a control signal wave of the switch tube in the fractional-order negative inductance circuit.

[0091] The sinusoidal pulse width modulation module SPWM uses a triangular carrier to modulate the control signal wave output by the MCU controller to generate a control signal for controlling the switch tube.

[0092] The AC properties of fractional-order negative inductance: it blocks AC and passes DC, so it can still be used for filtering; the phase of the voltage lags behind the current by 90°, similar to an ideal positive capacitor, and the DC properties of the negative inductance are consistent with those of a conventional positive inductance.

[0093] The control method of a high-power filter based on fractional-order positive and negative inductors in parallel is proposed in the present invention. Figure 3 As shown, the method includes:

[0094] Step S1: Determine the filter inductance according to the grid-connected power quality requirements The size of the fractional negative inductance is then calculated. and positive inductance The inductance value;

[0095] The current phase characteristics of fractional-order positive inductance and negative inductance are opposite. When the two are connected in parallel, the current phase is opposite. According to the power quality requirements of the grid, the filter inductance value is determined. The fractional negative inductance is then calculated and positive inductance Inductance value, equivalent filter inductance value when inductors are connected in parallel and fractional negative inductance , positive inductance The relationship is as follows:

[0096]

[0097] in, is the inductance of the fractional negative inductor, is the inductance of the fractional positive inductor. Approaching size When the equivalent inductance after parallel connection is This is equivalent to a huge inductor in the full frequency band. It can replace the traditional large inductor for filtering. The inductance values ​​of the negative inductance and the positive inductance can be determined according to actual needs. The positive inductance is a physical inductance, and the inductance value is generally fixed and inconvenient to adjust. However, the inductance value of the fractional-order negative inductor is its control parameter and can be flexibly adjusted, so that the overall inductance value of the parallel connection can be flexibly adjusted to meet actual needs.

[0098] For example, when a 20mH inductor is required, a 4mH positive inductor and a 5mH negative inductor can be connected in parallel. The inductance values ​​of the negative inductor and the positive inductor can be determined based on actual needs.

[0099] Step S2: Calculate the order of the fractional-order positive inductor according to the voltage and current in the fractional-order positive inductor, and set the order of the negative inductor to be equal to the order of the positive inductor to obtain the control parameters of the MCU;

[0100] The essence of many physical phenomena in nature has fractional-order characteristics, and inductance is also a fractional-order device. And the inductance of fractional positive inductance Calculate the inductive reactance of positive and negative inductors in parallel for:

[0101]

[0102] in, is the order of the fractional positive inductance, is the order of the fractional negative inductance, , is the fundamental angular frequency of the excitation voltage across the parallel structure, is the fundamental frequency;

[0103] The essential idea of ​​this method is to set the inductance value and order of the negative inductor so that the output current of the negative inductor and the current amplitude of the branch where the positive inductor is located are close and the phase is opposite, so the current on the main line decreases. Under the premise of unchanged voltage, the overall inductive reactance increases. Approaching size When the currents of the two branches are closer, the more obvious the negative inductance branch current is in canceling the positive inductance branch current. Through the above calculation of inductive reactance, it can be found that when hour, Therefore, in the method of achieving a higher inductance by connecting positive and negative inductors in parallel, the order of the negative inductor should be set equal to the order of the positive inductor. If the orders of the two are different, the current phases of the two branches will deviate, which may make the increase in inductance after parallel connection not obvious.

[0104] The voltage-current relationship for a positive inductor is: ;in, is the voltage applied to the positive inductor, is the current in the positive inductor.

[0105] In order to adjust the order of the negative inductance to match the order of the positive inductance, the voltage-current relationship of the positive inductance is Fourier transformed to obtain the following relationship:

[0106] ;

[0107] Taking the logarithm of both sides of the equation, we get the following expression:

[0108] ;

[0109] According to the above formula, the order of positive inductance is obtained , use a function signal generator to apply voltage to the positive inductor, and change the voltage frequency multiple times (generally in a lower frequency band, between 50Hz and 200Hz, and the experiment can also be flexibly designed for measurement according to the actual application).

[0110] Then adjust the order of the fractional-order negative inductor to keep it consistent with the order of the positive inductor, so as to ensure that the current phase difference in the two branches is 180°. Finally, adjust the equivalent inductance of the fractional-order negative inductor so that the overall inductance after parallel connection meets the required inductance.

[0111] Step S3: Obtain the voltage of the external excitation at both ends of the fractional-order negative inductor ports A and B and port current , and set the fractional negative inductance Internal parameters of auxiliary resistor and the output voltage of the DC-DC converter circuit , generating a gate drive control signal according to a control strategy;

[0112] Step S31: Auxiliary resistance in fractional-order negative inductance and the output voltage of the DC-DC converter circuit The equivalent inductance of the fractional negative inductor is and order After setting, the triangular carrier amplitude used by the sine pulse width modulation module SPWM Set to 1, by adjusting and At the same time, the following relationship is satisfied so that the signal wave generated by the MCU controller The amplitude range is , the single-phase inverter for equivalent fractional-order negative inductance can work normally:

[0113]

[0114] in, , is the amplitude of the external excitation voltage, is the fundamental angular frequency of the external excitation voltage signal, and the voltage proportional coefficient ;

[0115] Step S32: In each sampling period, the voltage of the external excitation at both ends of the fractional-order negative inductance port is measured by the sensor. and port current Perform sampling and input the sampling results into the MCU controller:

[0116] Step S33: Generate a bipolar modulated signal wave in a fractional-order negative inductance topology structure. The mathematical model of the fractional-order negative inductance is expressed as follows:

[0117]

[0118] Where β is the order of the fractional negative inductance, is the inductance of the fractional negative inductor, is the excitation voltage across the fractional-order negative inductor port The frequency domain representation of is the port current Frequency domain representation of .

[0119] The angle at which the voltage phase of the fractional-order negative inductor leads the current is: ;

[0120] Therefore, for the first-order fractional negative inductor, the current leads the voltage by 90°.

[0121] The following relationship exists between the external excitation voltage and port current of the fractional-order negative inductor and the two sides of the sampling resistor:

[0122]

[0123] in, is the filtered voltage signal, R is the sampling resistor, is a fractional differential operator.

[0124] After simplification, we get:

[0125]

[0126] Since the inverter output and the modulation signal have the same phase and proportional amplitude, the signal wave of the MCU controller is:

[0127]

[0128] Among them, the voltage proportionality coefficient , is the amplitude of the triangular carrier, is the output DC voltage of the DC-DC converter circuit, is a fractional-order integral operator, and They are reciprocals of each other.

[0129] Ignoring the influence of the filter circuit, the control block diagram of the fractional-order negative inductor is as follows: Figure 4 shown.

[0130] For the fractional integral operator , using the Oustaloup filter approximation calculation, the frequency band of interest can be generally selected as (10e-5, 10e+5) Hz, and the straight line characteristics of the fractional-order integral operator are approximated using broken lines. All these broken lines are generated by integer-order zeros and poles, so that the asymptote slope of the amplitude-frequency characteristic curve alternates between 0dB / dec and -20dB / dec. Such a frequency domain response characteristic itself will well approximate a slant line, such as Figure 5 shown.

[0131] Using Oustaloup filter to approximate fractional integral operator The method is:

[0132]

[0133] Among them, the zero point of the Oustaloup filter and pole The calculation is as follows:

[0134]

[0135] in, is the order of the filter, and are the lower and upper frequency limits of the selected frequency band respectively. Fractional integral operators of any order can be viewed as The product of a fractional-order integral operator and an integer-order integral operator.

[0136] For example, the selected frequency band is (10e-5, 10e+5), the filter order is 5, and the orders are 0.5 and 1.2 respectively. The filter form equivalent to the fractional-order integral operator is as follows:

[0137] Fractional-order integral operator for sinusoidal signals The response is as follows:

[0138]

[0139] It can be found that there are two DC components and , are caused by the initial value of the integral and the filter response, respectively. In order to obtain the AC component, a low-pass filter is used to extract the DC component to obtain the AC component. A sinusoidal signal with an amplitude of 150 and a frequency of 2000Hz is input into a 1.2-order fractional-order integral operator for operation, and the DC offset is further eliminated, as shown in Figure 7 shown.

[0140] The above derivation does not take into account the influence of LLC filter circuit. and And filter capacitor Taking this into consideration, the obtained fractional-order negative inductance model can be made more accurate. During normal operation, the phase deviation caused by the filter circuit is smaller, and the phase fitting effect is better.

[0141] The parameters of the components in the fractional-order negative inductance circuit have the following relationship:

[0142]

[0143] in, is the voltage of the filter capacitor branch, is the current in the filter capacitor branch, is the current flowing through the filter inductor The current, It is the output voltage of the single-phase inverter, that is, the voltage between the emitter of the second switch tube V2 and the collector of the third switch tube V3.

[0144] Therefore, the signal wave of the MCU controller considering the influence of the LLC filter circuit is obtained. for:

[0145]

[0146] in:

[0147]

[0148] The control block diagram of the fractional-order negative inductor considering the influence of the filter circuit is as follows: Figure 6 As shown, the generation methods of these two signal waves can be determined according to actual application conditions.

[0149] Step S34: the sinusoidal pulse width modulation module SPWM performs sinusoidal pulse width modulation on the signal wave and the local triangular carrier, thereby generating control signals for the four switch devices.

[0150] The H-bridge equivalent structure and control method of the full-band fractional-order negative inductor of the present invention can show the inductive reactance characteristics of the fractional-order negative inductor in the full-band, that is, there is no need to modify the control parameters of the fractional-order negative inductor according to the frequency of the excitation at both ends of the port. The fractional-order negative inductor in the present invention is suitable for the full-band, and can therefore be used in application scenarios with a high harmonic content to achieve a filtering function.

[0151] For the control method of the H-bridge equivalent structure of the full-band fractional-order negative inductor of the present invention, it is assumed that there is only a sinusoidal voltage signal of a specific frequency at both ends of the fractional-order negative inductor port. , substitute the signal wave The calculation formula of and Laplace inverse transformation can be obtained:

[0152]

[0153] According to the above formula, it can be found that when the frequency is higher, the second term gradually tends to zero, so there is ,Right now

[0154] When the frequency is infinite, the auxiliary resistor The voltage signals at both ends have a smaller phase difference, the phases tend to be the same, the amplitude difference becomes smaller, and the output current of the port It tends to zero, therefore, the fractional-order negative inductor exhibits high inductive reactance under high-frequency excitation and low inductive reactance under low-frequency excitation. According to the superposition theorem, the fractional-order negative inductor has a strong ability to block high-frequency signals in a line containing multiple harmonics, so filtering can be achieved.

[0155] Step S4: Check whether the filtering result of the positive and negative inductance parallel filter meets the power quality requirements, and further adjust the positive and negative inductance parameters.

[0156] In order to verify the feasibility of high-power filter based on fractional-order positive and negative inductors in parallel, according to Figure 1 , Figure 3 and Figure 5 Build a simulation module in MATLAB, set the predetermined control parameters according to Table 1, start the simulation, and get the following simulation results:

[0157] Table 1 Internal circuit device parameters, control parameters and external excitation parameters of fractional-order negative inductors

[0158]

[0159] According to the simulation data of the second, third and fourth groups in Table 1, the simulation results are as follows: Figure 8 , Fig. 9 , Fig.10 As shown, the current leads the voltage by 90° in phase, and the current decreases continuously with increasing frequency, indicating that the port inductive reactance of the full-band fractional-order negative inductor described in the present invention increases with increasing frequency.

[0160] According to the simulation data of the first, third and fifth groups in Table 1, the simulation results are as follows: Fig.11 , Fig. 9 , Fig.12 As shown, by ensuring that the external excitation remains unchanged and changing the order of the fractional-order negative inductor, it can be found that as the order increases, the port inductance increases and the port current decreases, indicating that the port inductance of the full-band fractional-order negative inductor described in the present invention increases with the increase of the order.

[0161] Add the higher harmonics to the fundamental frequency signal of 50Hz and apply it to both ends of the full-band fractional-order negative inductor. The simulation results are as follows: Fig.13 As shown, the harmonic analysis of the two signals is as follows Fig.14 and Fig.15 As shown in the figure, the Total Harmonic Distortion (THD) content of the voltage signal is 17%, and the Total Harmonic Distortion (THD) content of the inductor current is 4.08%. It can be seen that the full-band fractional-order negative inductance has a very obvious inhibitory effect on high-frequency signals, and can show the inductive reactance characteristics of the negative inductance in the full frequency band.

[0162] When positive inductance and negative inductance are connected in parallel, the overall inductive reactance will increase significantly. Fig.16 As shown in the figure, a positive inductor of 0.4H and a negative inductor of 0.5H are connected in parallel, and the overall inductance is 2H. At t=0.06s, a negative inductor of 0.5H is added, and the current decreases from 0.844A to 0.1821A. When the inductance values ​​of the positive inductor and the negative inductor are equal, the inductive reactance tends to infinity, as shown in the figure below. Fig.17 As shown in the figure, a positive inductor of 0.4H and a negative inductor of 0.4H are connected in parallel. At t=0.06s, a negative inductor of 0.4H is added, and the current decreases from 0.844A to 0.0720A. It can be seen that the inductive reactance increases significantly when the positive and negative inductors are connected in parallel.

[0163] Through simulation verification, it can be concluded that the port characteristics of the equivalent fractional-order negative inductor in normal operation of the present invention meet the properties of the fractional-order negative inductor and can respond in the full frequency band, and can be applied to filter circuits with complex harmonic content. Through the control method of the high-power filter proposed in the present invention, the structure of fractional-order positive and negative inductors in parallel can use small inductors to show the performance of large inductors, which further illustrates that the present invention can reduce the volume of the filter, improve power density and reduce costs.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power filter based on fractional-order positive and negative inductors in parallel, characterized in that: The filter includes a fractional order negative inductor and positive inductance , the two are in parallel relationship; Fractional Negative Inductance It includes: a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, filter inductors L1 and L2, and a filter capacitor C f , filter damping R f , grounding capacitance C g , sampling resistor R, DC-DC conversion circuit, self-power supply module, MCU controller, digital-to-analog converter AD and sinusoidal pulse width modulation module SPWM, all switching tubes are insulated gate bipolar transistors IGBT.

2. The high power filter according to claim 1, characterized in that: The two output ends of the DC-DC conversion circuit, i.e., the DC chopper circuit, are respectively connected to the collector of the first switch tube V1 and the emitter of the third switch tube V3. The first switch tube V1 and the third switch tube V3 are connected in series, and the second switch tube V2 and the fourth switch tube V4 are connected in series. The collector of the second switch tube V2 is connected to one output end of the DC-DC conversion circuit, and the emitter of the fourth switch tube V4 is connected to the other output end of the DC-DC conversion circuit. The emitter of the first switch tube V1 is connected to the collector of the third switch tube V3, the collector of the first switch tube V1 is connected to the collector of the second switch tube V2, the emitter of the second switch tube V2 is connected to the collector of the fourth switch tube V4, and the emitter of the third switch tube V3 is connected to the emitter of the fourth switch tube V4. The gates of the four switch tubes are connected to the gate drive control signal. Both ends of the four switch tubes are connected in parallel with power diodes. The collector of each switch tube is connected to the negative electrode of the diode, and the emitter of each switch tube is connected to the positive electrode of the diode.

3. The high power filter according to claim 2, characterized in that: Four switching tubes form a single-phase inverter. In normal operation, the control signal controls the first state that the switching tubes V1 and V4 are turned on at the same time, and the switching tubes V2 and V3 are turned off. The second state is that the switching tubes V1 and V4 are turned off, and the switching tubes V2 and V3 are turned on at the same time.

4. The high-power filter according to claim 1, characterized in that: Filter inductors L1 and L2, filter capacitors C f and filter damping R f The LLC filter circuit is responsible for filtering out the harmonics introduced by the switch tube. The filter damping R f With filter capacitor C f One end of the filter inductor L1 is connected in series with the emitter of the second switch tube V2, and the other end of the filter inductor L1 is connected to the filter inductor L2 and the filter capacitor C f The other end of the filter inductor L2 is connected to one end of the sampling resistor R, and the other end of the sampling resistor R is connected to an AD digital-to-analog converter, which is used to convert the current between the A and B ports Converted into digital signal, another AD converter converts the analog voltage signal between A and B ports into digital signal, and the filter capacitor C f The other end of the filter damping R f Connected, filter damping R f The other end is connected to the collector of the third switch tube V3 and the grounding capacitor C g One end of the filter damping R f The other end of the capacitor C is connected to ground g The other end of the sampling resistor R is grounded, port A is the other end of the sampling resistor R, and port B is the filter damping R in the LLC filter circuit. f the other end.

5. The high power filter according to claim 1, characterized in that: The self-powered module directly obtains power from the drain-source end of the switch tube element, charges the capacitor therein and stores energy. The self-powered module supplies power to the gate drive circuit of the switch element and the MCU controller. The DC-DC conversion circuit takes power from the DC side bus to obtain the DC voltage U required by the single-phase full-controlled bridge. DC ; The MCU controller applies the excitation voltage u to the ports A and B of the fractional-order negative inductor. g (t) and the port current i L (t) performing sampling to generate a control signal wave of a switch tube in a fractional-order negative inductance circuit; The sinusoidal pulse width modulation module SPWM uses a triangular carrier to modulate the control signal wave output by the MCU controller to generate a control signal for controlling the switch tube.

6. A control method for a high-power filter with fractional-order positive and negative inductors in parallel based on any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step S1: Determine the filter inductance value according to the power quality requirements of the grid The fractional negative inductance is then calculated and positive inductance The inductance value; Step S2: Calculate the order of the fractional-order positive inductor according to the voltage and current in the fractional-order positive inductor, and set the order of the negative inductor to be equal to the order of the positive inductor to obtain the control parameters of the MCU; Step S3: Obtain the voltage of the external excitation at both ends of the fractional-order negative inductor ports A and B and port current , and set the fractional negative inductance Internal parameters of auxiliary resistor and the output voltage of the DC-DC converter circuit , generating a gate drive control signal according to a control strategy; Step S4: Check whether the filtering result of the positive and negative inductance parallel filter meets the power quality requirements, and further adjust the positive and negative inductance parameters.

7. The control method according to claim 6, characterized in that: The step S1 further comprises: determining the equivalent filter inductance value when the inductors are connected in parallel Then, according to the expression Calculate the value of fractional negative inductance And the inductance of fractional positive inductance .

8. The control method according to claim 6, characterized in that: The step S2 further includes: setting the voltage-current relationship of the positive inductor to: ,in, is the voltage applied to the positive inductor, is the current in the positive inductor, and according to Calculate the order of positive inductance , set the order of the negative inductance to be equal to the order of the positive inductance, and finally adjust the equivalent inductance of the fractional-order negative inductance so that the overall inductance after parallel connection meets the required inductance.

9. The control method according to claim 6, characterized in that: The step S3 further comprises: Step S31: Auxiliary resistance in fractional-order negative inductance and the output voltage of the DC-DC converter circuit Satisfies the following relationship: ； in, The triangle carrier amplitude used by the sine pulse width modulation module SPWM, , is the amplitude of the external excitation voltage, is the fundamental angular frequency of the external excitation voltage signal, and the voltage proportional coefficient ; Step S32: In each sampling period, the voltage of the external excitation at both ends of the fractional-order negative inductance port is measured by the sensor. and port current Perform sampling and input the sampling results into the MCU controller; Step S33: Generate a bipolar modulated signal wave in the fractional-order negative inductor topology structure. Without considering the influence of the LLC filter circuit, the following relationship exists between the external excitation voltage and the port current of the fractional-order negative inductor and the two sides of the sampling resistor: ； in, is the inductance of the fractional negative inductor, is the excitation voltage across the fractional-order negative inductor port The frequency domain representation of is the port current The frequency domain representation of is the filtered voltage signal, R is the sampling resistor, is a fractional differential operator; The signal wave of the MCU controller is: , where the voltage proportionality factor , is the amplitude of the triangular carrier, is the output DC voltage of the DC-DC converter circuit, is a fractional-order integral operator, and The two are reciprocal; Step S34: the sinusoidal pulse width modulation module SPWM performs sinusoidal pulse width modulation on the signal wave and the local triangular carrier, thereby generating control signals for the four switch devices.

10. The control method according to claim 9, characterized in that: In step S33, the filter inductance in the LLC filter circuit is considered and And filter capacitor In this case, the signal wave calculation method of the MCU controller is as follows: The parameters of the components in the fractional-order negative inductance circuit have the following relationship: ； in, is the voltage of the filter capacitor branch, is the current in the filter capacitor branch, is the current flowing through the filter inductor The current, is the output voltage of the single-phase inverter, that is, the voltage between the emitter of the second switch tube V2 and the collector of the third switch tube V3; At this time, the signal wave of the MCU controller for: ； in: 。

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