Frequency conversion device and harmonic suppression control method thereof

Abstract

The invention discloses a frequency conversion device and a harmonic suppression control method thereof, and the frequency conversion device comprises a commutation circuit of which the input end is used for accessing a power grid and the output end is used for accessing a load, and is used for converting the alternating current of the power grid into frequency-adjustable alternating current to be provided for the load to use; the variable inductance module is connected between the input end of the commutation circuit and a power grid and is used for generating different inductance values; the input end of the sampling control circuit is connected to a loop between the output end of the commutation circuit and the load, and the output end of the sampling control circuit is connected with the variable inductance module; and the variable inductance module is controlled to generate a corresponding inductance value according to the collected current and voltage, and the inductance value is input to a loop between the input end of the converter circuit and a power grid. The frequency conversion device can effectively restrain multiple dynamic harmonics generated by the device, and harmonic pollution of a power grid is reduced.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of frequency converters, and in particular to a frequency converter device and a harmonic suppression control method thereof. Background Art

[0002] With the widespread adoption of renewable energy generation, industrial variable-frequency equipment, and nonlinear loads, harmonic pollution in the power grid has become increasingly prominent, leading to increased equipment losses, reduced energy efficiency, and potential hazards such as malfunctioning relay protection. Traditional harmonic suppression solutions, while low-cost, include passive filters (LC circuits) that can only filter out harmonics of fixed suborders. Active power filters (APFs), while capable of dynamic compensation, rely on high-frequency IGBT switching devices, resulting in high costs and complex control algorithms. Furthermore, harmonic suppression solutions used in traditional variable-frequency equipment often assume steady-state harmonics, making them difficult to suppress dynamic harmonic fluctuations caused by time-varying loads such as variable-frequency compressors. Summary of the Invention

[0003] The present invention provides a frequency conversion device and a harmonic suppression control method thereof, aiming to solve the problem that frequency conversion equipment generates multiple dynamic harmonics that pollute the power grid, leading to equipment loss and reduced energy efficiency.

[0004] In a first aspect, an embodiment of the present invention provides a frequency conversion device, comprising:

[0005] The commutation circuit has an input end for connecting to the power grid and an output end for connecting to the load, and is used to convert the AC power of the power grid into frequency-adjustable AC power for use by the load;

[0006] a variable inductance module, connected between the input end of the commutation circuit and the power grid, for generating different inductance values;

[0007] A sampling control circuit, having an input end connected to the loop between the output end of the commutation circuit and the load, and an output end connected to the variable inductance module, is configured to collect the current and voltage at the output end of the commutation circuit, and control the variable inductance module to generate a corresponding inductance value based on the collected current and voltage, which is then input into the loop between the input end of the commutation circuit and the power grid.

[0008] Furthermore, the commutation circuit includes a rectifier module and an inverter module, the output end of the rectifier module is connected to the input end of the inverter module, the output end of the inverter module is connected to the load, the variable inductor module is connected between the input end of the rectifier module and the power grid, and the sampling control circuit is connected to the loop between the output end of the inverter module and the load, wherein the sampling control circuit collects the current and voltage at the output end of the inverter module.

[0009] Furthermore, the rectifier module includes a three-phase rectifier bridge, the variable inductor module includes a first variable inductor, a second variable inductor and a third variable inductor, the three phases of the input end of the three-phase rectifier bridge are respectively connected to the three phases of the power grid through the first variable inductor, the second variable inductor and the third variable inductor, the input end of the sampling control circuit is connected to the three phases of the output end of the inverter module, and the output end of the sampling control circuit is connected to the first variable inductor, the second variable inductor and the third variable inductor.

[0010] Furthermore, the rectifier module further includes a filter capacitor, which is connected in parallel to the output end of the three-phase rectifier bridge.

[0011] Furthermore, the sampling control circuit includes a sampling module and a control module, the sampling module input end is connected to the three phases of the inverter module output end, the control module input end is connected to the sampling module output end, and the control module output end is connected to the first variable inductor, the second variable inductor, and the third variable inductor, wherein the sampling module is used to collect the three-phase current and voltage at the inverter module output end, and the control module is used to control the first variable inductor, the second variable inductor, and the third variable inductor to generate corresponding inductance values ​​according to the three-phase current and voltage.

[0012] Furthermore, the control module includes a power supply unit and a resistance unit, and the power supply unit is connected to the first variable inductor, the second variable inductor, and the third variable inductor through the resistance unit, wherein the power supply unit is used to adjust and output the driving current according to the three-phase current and voltage at the output end of the inverter module collected by the sampling module, and the driving current cooperates with the resistance unit to drive the variable inductor module to generate a corresponding inductance value.

[0013] Furthermore, the power supply unit includes a first adjustable power supply, a second adjustable power supply, and a third adjustable power supply; the resistance unit includes a first resistor, a second resistor, and a third resistor; the first adjustable power supply is connected to the first variable inductor via the first resistor; the second adjustable power supply is connected to the second variable inductor via the second resistor; and the third adjustable power supply is connected to the third variable inductor via the third resistor.

[0014] In a second aspect, the present invention further provides a method for suppressing harmonics in a frequency conversion device, which is applied to the frequency conversion device described in the first aspect above, and the method includes: obtaining the current and voltage at the output end of the commutation circuit; calculating a target inductance value based on the current and voltage at the output end of the commutation circuit; and controlling a variable inductance module to generate the target inductance value.

[0015] The present invention provides a frequency conversion device and a method for suppressing harmonics thereof, wherein the frequency conversion device includes: a commutation circuit, whose input end is used to connect to a power grid and whose output end is used to connect to a load, and is used to convert the alternating current of the power grid into frequency-adjustable alternating current for use by the load; a variable inductance module, connected between the input end of the commutation circuit and the power grid, and used to generate different inductance values; a sampling control circuit, whose input end is connected to the loop between the output end of the commutation circuit and the load, and whose output end is connected to the variable inductance module, and is used to collect the current and voltage at the output end of the commutation circuit, and control the variable inductance module to generate a corresponding inductance value based on the collected current and voltage, and input it into the loop between the input end of the commutation circuit and the power grid. The frequency conversion device of the present application effectively suppresses multiple dynamic harmonics generated by the device and reduces power grid harmonic pollution by providing a variable inductance module on the input side of the commutation circuit, collecting the current and voltage at the output end of the commutation circuit through the sampling control circuit, and controlling the variable inductance module to generate a corresponding inductance value based on the current and voltage, and inputting it into the loop between the input end of the commutation circuit and the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 any creative work.

[0017] Figure 1 A schematic structural diagram of a frequency conversion device provided in an embodiment of the present invention;

[0018] Figure 2 A circuit diagram of a frequency conversion device provided by an embodiment of the present invention;

[0019] Figure 3 A schematic flow chart of the steps of the method provided in an embodiment of the present invention;

[0020] Figure 4 A schematic flow chart of the sub-steps of the method provided in an embodiment of the present invention;

[0021] Figure 5 A schematic flow chart of the sub-steps of the method provided in an embodiment of the present invention.

[0022] Reference numerals:

[0023] 1. Commutation circuit; 11. Rectifier module; 111. Three-phase rectifier bridge; 112. Filter capacitor; 12. Inverter module; 2. Variable inductor module; 3. Sampling control circuit; 31. Sampling module; 32. Control module; 321. Power supply unit; 322. Resistance unit. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0028] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0029] In order to facilitate understanding of the present invention, the frequency conversion device provided by the embodiment of the present invention is first described. Figure 1 and Figure 2An embodiment of the present invention provides a frequency conversion device, which includes: a commutation circuit 1, whose input end is used to connect to the power grid, and whose output end is used to connect to the load, and is used to convert the alternating current of the power grid into frequency-adjustable alternating current for use by the load; a variable inductance module 2, connected between the input end of the commutation circuit 1 and the power grid, and used to generate different inductance values; a sampling control circuit 3, whose input end is connected to the loop between the output end of the commutation circuit 1 and the load, and whose output end is connected to the variable inductance module 2, and is used to collect the current and voltage at the output end of the commutation circuit 1, and control the variable inductance module 2 to generate a corresponding inductance value based on the collected current and voltage, and input it into the loop between the input end of the commutation circuit 1 and the power grid.

[0030] In specific implementations, the frequency conversion device can be applied to scenarios such as compressor drive or any motor drive. The frequency conversion device mainly includes a commutation circuit 1, a variable inductance module 2, and a sampling control circuit 3. The input end of the commutation circuit 1 is used to connect to the power grid that provides three-phase AC power, and the output end of the commutation circuit 1 is used to connect to the load, which is mainly the permanent magnet synchronous motor of the compressor. The commutation circuit 1 is used to convert the AC power provided by the power grid into frequency-adjustable AC power for use by the load. Specifically, the commutation circuit 1 includes rectification and inversion functions, wherein the rectification function converts the AC power of the power grid into DC power, and the inversion function converts the converted DC power into AC power. The frequency of the AC power output to the load can be adjusted according to demand. The variable inductor module 2 is primarily connected to the loop between the input of the commutation circuit 1 and the power grid. The AC power provided by the power grid can only be input into the commutation circuit 1 after passing through the variable inductor module 2. The variable inductor module 2 is used to generate different inductance values, which are input into the loop between the input of the commutation circuit 1 and the power grid. Different inductance values ​​can cause the loop to produce different inductive reactances. In specific applications, the variable inductor module 2 can be designed with one or more variable inductor devices. The inductance value generated by the variable inductor module 2 is controlled by a sampling control circuit 3. The input of the sampling control circuit 3 is connected to the loop between the output of the commutation circuit 1 and the load, and the output of the sampling control circuit 3 is connected to the variable inductor module 2. In specific applications, the sampling control circuit 3 is used to collect the current and voltage at the output of the commutation circuit 1 and, based on the collected current and voltage, control the variable inductor module 2 to generate a corresponding inductance value, which is input into the loop between the input of the commutation circuit 1 and the power grid.

[0031] In actual applications, the input of the commutation circuit 1 is connected to the power grid via the variable inductor module 2, and the output of the commutation circuit 1 is connected to the AC load. When the frequency conversion device is operating normally, the sampling control circuit 3 collects the current and voltage at the output of the commutation circuit 1 in real time. Based on the collected current and voltage, the sampling control circuit 3 controls the variable inductor module 2 to generate a corresponding inductance value, which is input into the loop between the input of the commutation circuit 1 and the power grid. The process by which the variable inductor module 2 generates the inductance value will be described in detail in the method below and will not be further explained here. When the current and voltage at the output of the commutation circuit 1 change, the sampling control circuit 3 will correspondingly control the change in the inductance value generated by the variable inductor module 2, dynamically adjusting the inductive reactance of the input loop of the commutation circuit 1 and specifically removing the current spikes at the output of the commutation circuit 1, thereby effectively suppressing the interference of multiple dynamic harmonics and reducing power grid harmonic pollution.

[0032] In a further embodiment, referring to Figure 1 and Figure 2 The commutation circuit 1 includes a rectifier module 11 and an inverter module 12. The output of the rectifier module 11 is connected to the input of the inverter module 12, and the output of the inverter module 12 is connected to a load. The variable inductor module 2 is connected between the input of the rectifier module 11 and the power grid. The sampling control circuit 3 is connected to the loop between the output of the inverter module 12 and the load, wherein the sampling control circuit 3 collects the current and voltage at the output of the inverter module 12. In a specific implementation, the commutation circuit 1 includes two parts: the rectifier module 11 and the inverter module 12. The output of the rectifier module 11 is connected to the input of the inverter module 12, and the output of the inverter module 12 is connected to a load. In specific applications, the rectifier module 11 is primarily composed of multiple diodes, which perform a rectification function and convert the three-phase AC power provided by the power grid into DC power for input to the input of the inverter module 12. The inverter module 12 is primarily composed of multiple IGBT power switches, which perform an inversion function and convert the DC power output from the rectifier module 11 back into AC power for output to the load. The frequency of the output AC power is controllable. The sampling control circuit 3 is primarily connected to the loop between the output of the inverter module 12 and the load, specifically to each phase of the output of the inverter module 12. The variable inductor module 2 is connected to the loop between the input of the rectifier module 11 and the power grid, that is, the input of the rectifier module 11 is connected to the power grid through the variable inductor module 2. In actual applications, the sampling control circuit 3 collects the current and voltage at the output end of the inverter module 12, and controls the variable inductor module 2 according to the collected current and voltage to generate a corresponding inductance value input into the loop between the input end of the rectifier module 11 and the power grid, dynamically adjusting the inductive reactance of the input loop on the rectifier side, thereby suppressing the interference of multiple dynamic harmonics and reducing power grid harmonic pollution.

[0033] In a further embodiment, referring to Figure 2 The rectifier module 11 includes a three-phase rectifier bridge 111, and the variable inductor module 2 includes a first variable inductor L1, a second variable inductor L2, and a third variable inductor L3. The three phases at the input end of the three-phase rectifier bridge 111 are connected to the three phases of the power grid through the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3, respectively. The input end of the sampling control circuit 3 is connected to the three phases at the output end of the inverter module 12, and the output end of the sampling control circuit 3 is connected to the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3. In a specific implementation, the rectifier module 11 includes a three-phase rectifier bridge 111, and the variable inductor module 2 includes three variable inductors: the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3. The three-phase rectifier bridge 111 is primarily composed of six connected rectifier diodes VD1-VD6, forming a bridge rectifier circuit that achieves full-wave rectification of AC power. The three-phase rectifier bridge 111 has three input terminals, corresponding to the three phases of the power grid. The three phases at the input of the three-phase rectifier bridge 111 are connected to the three phases of the power grid via the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3, respectively. Each variable inductor corresponds to one phase. The input of the sampling control circuit 3 is connected to the three phases at the output of the inverter module 12, while the output of the sampling control circuit 3 is connected to the three variable inductors L1, L2, and L3. In actual application, the sampling control circuit 3 collects the current and voltage of each of the three phases at the output of the inverter module 12 and controls the variable inductor of the corresponding phase based on the current and voltage of each phase to output the corresponding inductance value. This dynamically adjusts the inductive reactance of the three-phase input circuit on the rectifier side, accurately suppressing the interference of multiple dynamic harmonics, and reducing harmonic pollution in the power grid.

[0034] In one embodiment, referring to Figure 2 The rectifier module 11 further includes a filter capacitor 112, which is connected in parallel to the output end of the three-phase rectifier bridge 111. In a specific implementation, the rectifier module 11 further includes a filter capacitor 112, which is connected in parallel to the output end of the three-phase rectifier bridge 111. The three-phase rectifier bridge 111 has two output ends. One end of the filter capacitor 112 is connected to one of the output ends of the three-phase rectifier bridge 111, and the other end of the filter capacitor 112 is connected to the other output end of the three-phase rectifier bridge 111. The filter capacitor 112 can filter out the AC ripple component in the rectified DC voltage and stabilize the output current waveform of the three-phase rectifier bridge 111.

[0035] In one embodiment, referring to Figure 1 and Figure 2The sampling control circuit 3 includes a sampling module 31 and a control module 32. The input end of the sampling module 31 is connected to the three-phase output end of the inverter module 12, the input end of the control module 32 is connected to the output end of the sampling module 31, and the output end of the control module 32 is connected to the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3. The sampling module 31 is used to collect the three-phase current and voltage at the output end of the inverter module 12, and the control module 32 is used to control the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 according to the three-phase current and voltage to generate corresponding inductance values. In a specific implementation, the sampling control circuit 3 includes two parts: the sampling module 31 and the control module 32. The input end of the sampling module 31 is connected to the three-phase output end of the inverter module 12, the input end of the control module 32 is connected to the output end of the sampling module 31, and the output end of the control module 32 is connected to the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3. In a specific application, the sampling module 31 can be a circuit or sensor with current / voltage sampling capabilities. The sampling module 31 is used to collect the three-phase current and voltage at the output of the inverter module 12, that is, to collect the current and voltage of each phase at the output of the inverter module 12. The control module 32 is used to control the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 based on the three-phase current and voltage collected by the sampling module 31 to generate corresponding inductance values. These inductance values ​​are input into each phase circuit at the input of the rectifier module 11, thereby dynamically adjusting the inductance of each phase input circuit on the stream side and suppressing interference from multiple dynamic harmonics.

[0036] In a further embodiment, referring to Figure 2The control module 32 includes a power supply unit 321 and a resistance unit 322. The power supply unit 321 is connected to the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 through the resistance unit 322. The power supply unit 321 is used to adjust and output a driving current based on the three-phase current and voltage at the output end of the inverter module 12 collected by the sampling module 31. The driving current cooperates with the resistance unit 322 to drive the variable inductor module 2 to generate a corresponding inductance value. In a specific implementation, the control module 32 includes a power supply unit 321 and a resistance unit 322. The power supply unit 321 is connected to the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 via the inductor unit. The first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 are all current-driven components, i.e., the inductance values ​​of the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 are all adjusted by the input current. The power supply unit 321 is primarily composed of a power supply with adjustable output current. The power supply unit 321 automatically adjusts and outputs the corresponding drive current based on the three-phase current and voltage at the output end of the inverter module 12 collected by the sampling module 31. The resistance unit 322 is primarily composed of a resistor device. The power supply unit 321 outputs a drive current that cooperates with the resistance unit 322 to drive the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 to generate an inductance value that can effectively suppress multiple harmonics. The first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 input their respective generated inductance values ​​into the three-phase circuit at the input end of the rectifier module 11, dynamically adjusting the inductive reactance of the three-phase input circuit on the rectifier side, suppressing the interference of multiple dynamic harmonics, and reducing harmonic pollution in the power grid.

[0037] In a further embodiment, referring to Figure 2The power supply unit 321 includes a first adjustable power supply V1, a second adjustable power supply V2, and a third adjustable power supply V3. The resistance unit 322 includes a first resistor R1, a second resistor R2, and a third resistor R3. The first adjustable power supply V1 is connected to the first variable inductor L1 via the first resistor R1, the second adjustable power supply V2 is connected to the second variable inductor L2 via the second resistor R2, and the third adjustable power supply V3 is connected to the third variable inductor L3 via the third resistor R3. In a specific implementation, the power supply unit 321 includes the first adjustable power supply V1, the second adjustable power supply V2, and the third adjustable power supply V3. The resistance unit 322 includes a first resistor R1, a second resistor R2, and a third resistor R3. The first resistor R1, the second resistor R2, and the third resistor R3 are all fixed resistors. The first adjustable power supply V1 is connected to the first variable inductor L1 via the first resistor R1, the second adjustable power supply V2 is connected to the second variable inductor L2 via the second resistor R2, and the third adjustable power supply V3 is connected to the third variable inductor L3 via the third resistor R3. In practical applications, the first adjustable power supply V1, the second adjustable power supply V2, and the third adjustable power supply V3 can modulate three specific drive currents for output under the control of the control signal. The three drive currents flow through the first resistor R1, the second resistor R2, and the third resistor R3 respectively to generate three different voltage signals, such as Figure 2 The three voltage signals CONTROL1, CONTROL2, and CONTROL3 shown are used to control the first variable inductor L1, the second variable inductor L2, and the third variable inductor L3, respectively, so that the three generate corresponding inductance values ​​and input them into the three-phase circuit at the input end of the rectifier module 11. This dynamically adjusts the inductive reactance of the three-phase input circuit on the rectifier side, suppresses the interference of multiple dynamic harmonics, and reduces harmonic pollution in the power grid.

[0038] The frequency conversion device provided in the embodiment of the present application provides a variable inductance module on the input side of the commutation circuit, collects the current and voltage at the output end of the commutation circuit through a sampling control circuit, and controls the variable inductance module to generate a corresponding inductance value based on the collected current and voltage, which is input into the loop between the input end of the commutation circuit and the power grid, thereby effectively suppressing multiple dynamic harmonics generated during load operation and reducing power grid harmonic pollution. At the same time, compared with traditional harmonic suppression solutions, it has lower cost and better reliability.

[0039] See also Figure 3 The embodiment of the present invention provides a method for suppressing harmonics in a frequency converter. The method is applied to the frequency converter in the above embodiment. Since the frequency converter has been described in detail in the above embodiment, it will not be described here for the sake of brevity. The method for suppressing harmonics in a frequency converter is described in detail below. Figure 3 As shown, the method includes steps: S110-S130.

[0040] S110: Acquire the current and voltage at the output end of the commutation circuit.

[0041] In specific implementation, the control system acquires the current and voltage at the output end of the commutation circuit. Specifically, the three-phase current and voltage at the output end of the commutation circuit are acquired to calculate the inductance value, and then controls the variable inductance module to generate the corresponding inductance value to input into the loop between the commutation circuit and the power grid.

[0042] S120. Calculate a target inductance value according to the current and voltage at the output end of the commutation circuit.

[0043] In a specific implementation, after obtaining the current and voltage at the output end of the commutation circuit, the system will calculate the target inductance value based on the current and voltage at the output end of the commutation circuit. Specifically, the target inductance value is the inductance value that the variable inductance module needs to generate, and is the inductance value required to suppress the interference of multiple harmonics. The target inductance value may include the inductance value of each phase of the three-phase input of the commutation circuit.

[0044] In one embodiment, if Figure 4 As shown, the step S120 includes steps: S121-S123.

[0045] S121. Perform Fourier transform on the current at the output end of the commutation circuit to obtain harmonic components.

[0046] In a specific implementation, after obtaining the current and voltage at the output of the commutation circuit, a Fourier transform (FFT) is performed on the current at the output of the commutation circuit to obtain the harmonic components. Specifically, the current and voltage at the output of the commutation circuit are analog quantities. Before performing the Fourier transform, the current and voltage at the output of the commutation circuit are first converted into digital signals through an ADC for processing. When performing the Fourier transform, the harmonic components can be calculated using the following formula:

[0047]

[0048] Among them, i (t) is the corresponding harmonic current, n is the harmonic order, I n Indicates the corresponding harmonic current amplitude, φ n is the corresponding harmonic phase.

[0049] S122. Calculate a target inductive reactance based on the harmonic component and the voltage value at the output end of the commutation circuit.

[0050] In the specific implementation, after the harmonic components are calculated, the target inductive reactance and the frequency f of the nth harmonic can be calculated according to the harmonic components and the voltage value at the output end of the commutation circuit. n=n×50Hz, the target inductive reactance can be calculated using the following formula:

[0051]

[0052] Among them, X 原 (f n ) represents the corresponding inductive reactance, V n is the corresponding harmonic voltage amplitude, I n Indicates the corresponding harmonic current amplitude, k is the suppression coefficient, usually ranging from 1 to 3, Z 原 (f n ) represents the complex form of the original impedance of the circuit, Re(Z 原 (f n )) means taking Z 原 (f n ), which is the original impedance R of the circuit, can be used to calculate the target inductive reactance that matches each circuit by combining the above formula.

[0053] S123. Calculate the target inductance value according to the target inductive reactance.

[0054] In the specific implementation, after the target inductive reactance value is calculated, the target inductance value can be calculated based on the target inductive reactance. The target inductance value is the inductance value that the variable inductance module needs to generate. The inductive reactance formula X L (f n )=2πf n L, and combined with the above formula, the calculation formula for the target inductance value can be obtained:

[0055]

[0056] Where L represents the corresponding inductance value, V n is the corresponding harmonic voltage amplitude, I n Indicates the corresponding harmonic current amplitude, k is the suppression coefficient, Z 原 (f n ) represents the complex form of the original impedance of the circuit, Re(Z 原 (f n )) means taking Z 原 (f n ), that is, the original impedance R, f n is the nth harmonic frequency. By combining the above formula, the target inductance value matching each can be calculated.

[0057] S130: Control the variable inductor module to generate the target inductance value.

[0058] In a specific implementation, after the target inductance value is calculated, the variable inductance module is controlled to generate the target inductance value. The target inductance value is associated with the output of the commutation circuit. The three phases of the input end of the commutation circuit correspond to three target inductance values. After the target inductance value is input into the loop between the input end of the commutation circuit and the power grid, it can effectively suppress the interference of multiple harmonics and reduce the harmonic pollution of the power grid.

[0059] In one embodiment, if Figure 5 As shown, the step S130 includes steps: S131-S133.

[0060] S131. Obtain a basic inductance value of the variable inductor module.

[0061] In specific implementation, the variable inductor module consists of three variable inductors, namely Figure 2 The first variable inductor L1, the second variable inductor L2, and the third variable inductor L3 shown are all current-controlled to generate corresponding inductance values. Each of the three variable inductors has a corresponding basic inductance value. To control the three variable inductors to generate corresponding target inductance values, the basic inductance value of the variable inductor module, that is, the basic inductance value of the three variable inductors, must first be obtained. Obtaining the basic inductance value of the inductor module can be achieved using a circuit with an inductance detection function.

[0062] S132: Calculate a target driving current according to the target inductance value and the basic inductance value.

[0063] In a specific implementation, after obtaining the basic inductance value of the variable inductor module, the target driving current can be calculated based on the target inductance value and the basic inductance value. Specifically, the target driving current is the current that drives the variable inductor module to generate the target inductance value. In the variable inductor module, the inductance value of each variable inductor can be calculated by the expression I n =I0+mI calculation, where I n represents the target inductance value of the variable inductor, I0 represents the basic inductance value of the variable inductor, I represents the target drive current, and m is a constant, usually between 0 and 1. Therefore, after determining the target inductance value and the basic inductance value, the target drive current required by the variable inductor of each phase of the commutation circuit can be obtained according to the above formula.

[0064] S133: Drive the variable inductor module with a target driving voltage to generate the target inductance.

[0065] In a specific implementation, the variable inductor in the variable inductor module is driven by the control module in the sampling control circuit to generate the target inductance value, such as Figure 2As shown, the control module consists of three adjustable power supplies V1 to V3 and three resistors R1 to R3. Each adjustable power supply is connected to a variable inductor in each phase through a resistor. The three adjustable power supplies V1 to V3 are connected to three variable inductors L1 to L3 through three resistors R1 to R3, respectively. After calculating the target drive current, the system adjusts the corresponding adjustable power supply to output a current equal to the target drive current based on the target drive current. The current forms a control voltage through the corresponding resistor. The control voltage V required for the variable inductor of each phase can be determined by V = IR. The control voltage controls the variable inductor of the corresponding phase to generate the corresponding target inductance value. The target inductance value is input into the loop between the input end of the commutation circuit and the power grid. The target inductance value generated by the variable inductor is dynamically adjusted according to the current harmonics on the output side of the commutation circuit, thereby effectively suppressing the interference of multiple dynamic harmonics generated by load operation and reducing power grid harmonic pollution.

[0066] In summary, the method of the present application obtains the current and voltage at the output end of the commutation circuit, calculates the target inductance value based on the current and voltage at the output end of the commutation circuit, and then controls the variable inductance module to generate the target inductance value. This can effectively suppress multiple dynamic harmonics generated during load operation, reduce pollution to the power grid, and reduce losses during device operation, thereby improving system energy efficiency.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A frequency conversion device, characterized in that: include: The commutation circuit has an input end for connecting to the power grid and an output end for connecting to the load, and is used to convert the AC power of the power grid into frequency-adjustable AC power for use by the load; a variable inductance module, connected between the input end of the commutation circuit and the power grid, for generating different inductance values; A sampling control circuit, having an input end connected to the loop between the output end of the commutation circuit and the load, and an output end connected to the variable inductance module, is configured to collect the current and voltage at the output end of the commutation circuit, and control the variable inductance module to generate a corresponding inductance value based on the collected current and voltage, which is then input into the loop between the input end of the commutation circuit and the power grid.

2. The frequency conversion device according to claim 1, characterized in that: The commutation circuit includes a rectifier module and an inverter module. The output end of the rectifier module is connected to the input end of the inverter module, and the output end of the inverter module is connected to the load. The variable inductor module is connected between the input end of the rectifier module and the power grid. The sampling control circuit is connected to the loop between the output end of the inverter module and the load, wherein the sampling control circuit collects the current and voltage at the output end of the inverter module.

3. The frequency conversion device according to claim 2, characterized in that: The rectifier module includes a three-phase rectifier bridge, and the variable inductor module includes a first variable inductor, a second variable inductor, and a third variable inductor. The three phases of the input end of the three-phase rectifier bridge are connected to the three phases of the power grid through the first variable inductor, the second variable inductor, and the third variable inductor respectively. The input end of the sampling control circuit is connected to the three phases of the output end of the inverter module, and the output end of the sampling control circuit is connected to the first variable inductor, the second variable inductor, and the third variable inductor.

4. The frequency conversion device according to claim 3, characterized in that: The rectifier module further includes a filter capacitor, which is connected in parallel to the output end of the three-phase rectifier bridge.

5. The frequency conversion device according to claim 3, characterized in that: The sampling control circuit includes a sampling module and a control module. The input end of the sampling module is connected to the three phases of the output end of the inverter module, the input end of the control module is connected to the output end of the sampling module, and the output end of the control module is connected to the first variable inductor, the second variable inductor, and the third variable inductor. The sampling module is used to collect the three-phase current and voltage at the output end of the inverter module, and the control module is used to control the first variable inductor, the second variable inductor, and the third variable inductor to generate corresponding inductance values ​​according to the three-phase current and voltage.

6. The frequency conversion device according to claim 5, characterized in that: The control module includes a power supply unit and a resistance unit. The power supply unit is connected to the first variable inductor, the second variable inductor, and the third variable inductor through the resistance unit. The power supply unit is used to adjust and output a driving current based on the three-phase current and voltage at the output end of the inverter module collected by the sampling module. The driving current cooperates with the resistance unit to drive the variable inductor module to generate a corresponding inductance value.

7. The frequency conversion device according to claim 6, characterized in that: The power supply unit includes a first adjustable power supply, a second adjustable power supply, and a third adjustable power supply. The resistance unit includes a first resistor, a second resistor, and a third resistor. The first adjustable power supply is connected to the first variable inductor via the first resistor, the second adjustable power supply is connected to the second variable inductor via the second resistor, and the third adjustable power supply is connected to the third variable inductor via the third resistor.

8. A method for suppressing harmonics in a frequency conversion device, characterized in that: Applied to the frequency conversion device according to any one of claims 1 to 7, the method comprises: obtaining the current and voltage at the output end of the commutation circuit; Calculating a target inductance value based on the current and voltage at the output end of the commutation circuit; The variable inductor module is controlled to generate the target inductance value.

9. The method according to claim 8, characterized in that The step of calculating the target inductance value based on the current and voltage at the output end of the commutation circuit includes: Performing Fourier transform on the current at the output end of the commutation circuit to obtain harmonic components; Calculating a target inductive reactance based on the harmonic component and the voltage value of the output end of the commutation circuit; The target inductance value is calculated according to the target inductive reactance.

10. The method according to claim 8, characterized in that The controlling the variable inductor module to generate the target inductance value includes: Get the basic inductance value of the variable inductor module; Calculating a target driving current according to the target inductance value and the basic inductance value; The variable inductor module is driven with a target driving voltage to generate the target inductance.

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