CN117526674A

CN117526674A - Power converter and resonance suppression method

Info

Publication number: CN117526674A
Application number: CN202311279850.5A
Authority: CN
Inventors: 陈剑波; 荣先亮; 顾桂磊; 戚鑫; 彭忠; 辛凯
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2024-02-06

Abstract

The embodiment of the application provides a power converter and a resonance suppression method, wherein the output end of the power converter is used for being connected with the input ends of other power converters, and the power converter comprises a controller and a power conversion circuit; the controller is used for adjusting the pulse width modulation signal output to the power conversion circuit based on the alternating current component with the largest amplitude in the electric quantity output by the power conversion circuit; the frequency of the pulse width modulation signal after adjustment comprises a resonance frequency, wherein the resonance frequency is the frequency of an alternating current component with the largest amplitude in the electric quantity output by the power conversion circuit, and the output impedance corresponding to the resonance frequency is increased in an active damping mode, so that resonance energy is consumed, the amplitude of resonance current is reduced, and the output stability of the power converter is further ensured.

Description

Power converter and resonance suppression method

Technical Field

The application relates to the technical field of energy, in particular to a power converter and a resonance suppression method.

Background

In the operation process of the cascade system of the photovoltaic optimizers, the actual working point of the photovoltaic optimizers is greatly influenced by weather change, and the output impedance change is obvious. When the inverter output power is small, high frequency resonant currents often occur in the photovoltaic optimizer and inverter connection cable. When the peak-to-peak value of the high-frequency resonance current is larger than a threshold value, communication interruption of a programmable logic controller (programmable logic controller, PLC) is caused, and when the duration is larger than a set value, the inverter is also caused to be shut down, so that power generation capacity loss is caused.

Therefore, how to suppress the resonant current on the output line of the power converter is a technical problem to be solved.

Disclosure of Invention

The power converter and the resonance suppression method are used for solving the problem that resonance current on an output line of the power converter is overlarge in the prior art.

In a first aspect, embodiments of the present application provide a power converter, an output of the power converter being configured to be connected to an input of another power converter, the power converter including a controller and a power conversion circuit;

the controller is used for adjusting the pulse width modulation signal of the power conversion circuit based on the alternating current component with the largest amplitude in the electric quantity output by the power conversion circuit, wherein the frequency of the pulse width modulation signal after adjustment comprises a resonance frequency, and the resonance frequency is the frequency of the alternating current component with the largest amplitude in the electric quantity output by the power conversion circuit.

It should be noted that the power converter in the embodiments of the present application may be a photovoltaic optimizer, a direct current-direct current (DC-DC) converter, a direct current-alternating current (alternating current, DC-AC) converter (such as an inverter), and other devices for power conversion.

The electric quantity output by the power conversion circuit may be the electric quantity on the cable at the output end of the power converter, and in addition, the electric quantity on the cable may be directly sampled by using the sampler, or constituent devices of the power conversion circuit may be sampled by using the sampler, so as to calculate the electric quantity output by the power conversion circuit.

During operation of the power converters, the noise frequency coincides with or is close to the resonance frequency, resulting in the resonance energy not being consumed, and thus in the presence of resonance currents on the cables between the cascaded power converters.

Based on the technical scheme of the embodiment of the application, the controller outputs the pulse width modulation signal with the resonant frequency in the frequency component, so that the power conversion circuit increases the output impedance aiming at the alternating current component corresponding to the resonant frequency.

In addition, the technical scheme of the embodiment of the application increases the output impedance aiming at the resonant frequency, does not influence other frequencies, and ensures the output stability of the power converter.

Furthermore, the output impedance of the power conversion circuit is adjusted by adopting an active damping method, so that the technical scheme does not need extra hardware cost and has no extra loss.

In one possible design, the adjusted pulse width modulated signal includes a target duty cycle, the target duty cycle being based on a product of the virtual current and the virtual resistance;

the virtual current is derived from the resonant frequency.

Since the present design requires suppression of the resonance frequency and does not affect other frequencies, the virtual current used for calculating the duty ratio is obtained based on the resonance frequency.

The virtual resistance is obtained according to the alternating current component with the largest amplitude in the electric quantity.

Since the output impedance of the power conversion circuit needs to be increased to suppress the amplitude of the electric quantity, the magnitude of the output impedance needs to be increased in relation to the amplitude of the electric quantity, and thus the virtual resistance value used for calculating the duty ratio is obtained based on the alternating current component with the largest amplitude in the electric quantity.

Based on the technical scheme of the design, the controller can obtain a corresponding voltage value based on the product of the virtual resistance value and the virtual current, and then the voltage value is converted into a target duty ratio to adjust a pulse width modulation signal, so that the output of the power conversion circuit is controlled.

In one possible design, if the product of the virtual current and the virtual resistance is greater than or equal to a preset first voltage threshold, the target duty cycle is obtained based on the first voltage threshold; or alternatively

If the product of the virtual current and the virtual resistance is smaller than or equal to a preset second voltage threshold, the target duty ratio is obtained based on the second voltage threshold; or alternatively

If the product of the virtual current and the virtual resistance is greater than the second voltage threshold and less than the first voltage threshold, the target duty cycle is obtained based on the product of the virtual current and the virtual resistance.

It can be understood that the virtual resistance value and the virtual current are multiplied to obtain a corresponding voltage value and then converted into a duty ratio, but the excessive or insufficient duty ratio can affect the balance of the system, so that other devices such as a limiter and the like can be configured to limit the size of the duty ratio by combining the actual application scene and the working parameters of the power conversion circuit in the design.

In one possible design, the electrical quantity is the output current;

the virtual resistance value is obtained based on the alternating current component with the largest amplitude value in the output current and the preset virtual resistance value-maximum alternating current component correspondence;

the virtual current is obtained by bandpass filtering the output current based on the resonance frequency or the sum of the resonance frequency and a first margin threshold, wherein the first margin threshold is larger than zero.

It should be noted that, considering that the band-pass filtering process is a slow high-precision process in practical application, the data delay is long and cannot be used for dynamic response, so that the resonance frequency can be corrected by setting the frequency margin, so that the corrected frequency is more suitable for the requirements of dynamic response on data precision and response speed;

in addition, the peak value of the resonance frequency on the cable in actual engineering may deviate, if the resonance frequency is directly used for resonance suppression, the suppression effect is poor, so that the influence of the phase deviation of the resonance peak can be avoided by adding a bit margin according to the resonance frequency;

for example, in the practical application process, the lower phase of the output current of the power conversion circuit affects the suppression effect, so that the resonant frequency can be adjusted to be slightly larger.

Based on the technical scheme of the design, firstly, the controller carries out band-pass filtering on the output current based on the resonance frequency or the sum of the resonance frequency and a first margin threshold value, so that the influence of other frequencies is avoided; in addition, the energy of the resonant current is determined according to the virtual current, the resistance value of the virtual resistor is reasonably adjusted, and the output impedance of the power conversion circuit is equivalently increased, so that the harmonic current is restrained in a reasonable range; furthermore, the design mode of active damping reduces the influence on the output steady state of the power conversion circuit and reduces the hardware cost.

In one possible design, the electrical quantity is the output voltage;

the virtual resistance value is obtained based on the alternating current component with the largest amplitude value in the output voltage and the preset virtual resistance value-maximum alternating current component correspondence;

the virtual current is the product of the target voltage and the capacitance value of the output capacitor of the power conversion circuit;

the target voltage is obtained by bandpass filtering the output voltage based on the resonance frequency or the sum of the resonance frequency and a second margin threshold value and a second filtering bandwidth; wherein the second margin threshold is greater than zero.

Based on the technical scheme of the design, firstly, the controller carries out band-pass filtering on the output voltage based on the resonance frequency or the sum of the resonance frequency and the second margin threshold value, so that the influence of other frequencies is avoided; in addition, the design calculates virtual current according to voltage, so as to further determine the energy of the resonant current, reasonably adjust the resistance of the virtual resistor, equivalently increase the output impedance of the power conversion circuit, and inhibit the harmonic current in a reasonable range; furthermore, the design mode of active damping reduces the influence on the output steady state of the power conversion circuit and reduces the hardware cost.

In one possible design, the controller is further configured to:

respectively carrying out band-pass filtering on the electric quantity based on a plurality of filtering parameters to obtain at least one alternating current component; wherein, the center frequencies of the filtering parameters are different from each other and the bandwidths are the same;

The resonant frequency is the center frequency of the filter parameter corresponding to the alternating current component with the largest amplitude in the at least one alternating current component.

It can be understood that the electrical quantity output by the power conversion circuit may include a direct current component and an alternating current component, and the design only needs to increase virtual impedance to the alternating current component, so as to consume energy corresponding to the resonant frequency to suppress the resonant current, thus needing to filter out components which do not need to be suppressed;

in addition, in practical application, a plurality of filtering parameters can be set through a plurality of band-pass filters to carry out band-pass filtering.

Based on the technical scheme of the design, components of frequencies except the center frequency are attenuated through a plurality of filtering parameters, and amplitude calculation and identification are performed on filtering electric quantities of a plurality of different frequencies through a controller, so that the maximum value of the alternating-current electric quantity and the resonant frequency are obtained, the virtual resistance is conveniently increased further for the resonant frequency, and the peak-to-peak value of the resonant current is reduced.

In one possible design, the controller is further configured to:

performing fast Fourier transform on the alternating current component of the electric quantity output by the power conversion circuit to obtain at least one alternating current component;

the resonant frequency is a frequency corresponding to an alternating current component having a largest amplitude among the amplitudes of the at least one alternating current component.

It will be appreciated that the electrical output from the power conversion circuit may include a dc component and an ac component, and the present design only requires adding a virtual impedance to the ac component, thereby consuming energy corresponding to the resonant frequency to suppress the resonant current, and thus requires filtering out components that do not need to be suppressed.

Based on the technical scheme of the design, the controller performs fast Fourier transform on the alternating-current electric quantity to obtain the maximum value of the alternating-current electric quantity and the resonance frequency of the alternating-current electric quantity, so that the virtual resistance value is increased according to the resonance frequency, and the amplitude of the resonance current is reduced.

In a second aspect, embodiments of the present application provide a resonance suppression method, including:

and adjusting the pulse width modulation signal of the power conversion circuit based on the alternating current component with the largest amplitude in the electrical quantity output to the other power converter by the power conversion circuit, wherein the frequency of the pulse width modulation signal after adjustment comprises a resonance frequency, and the resonance frequency is the frequency of the alternating current component with the largest amplitude in the electrical quantity output by the power conversion circuit.

The electric quantity output by the power conversion circuit may be the electric quantity on the cable at the output end of the power converter, and in addition, the electric quantity on the cable may be directly sampled by using a sampler, or constituent devices of the power conversion circuit may be sampled by using the sampler, so as to calculate the electric quantity output by the power conversion circuit.

In addition, the technical scheme of the embodiment of the application increases the output impedance aiming at the alternating current component corresponding to the resonant frequency, does not influence other frequencies, and ensures the output stability of the power converter.

The virtual current is obtained according to the resonant frequency;

In one possible design, the target duty cycle is based on a product of the virtual current and the virtual resistance, comprising:

if the product of the virtual current and the virtual resistance is greater than or equal to a first voltage threshold, generating a target duty cycle based on the first voltage threshold;

if the product of the virtual current and the virtual resistance is smaller than or equal to a second voltage threshold, generating a target duty cycle based on the second voltage threshold;

and if the product of the virtual current and the virtual resistance is larger than the second voltage threshold and smaller than the first voltage threshold, generating a target duty ratio based on the product of the virtual current and the virtual resistance.

It can be understood that the virtual resistance value is multiplied by the virtual current to obtain a corresponding voltage value and then converted into a duty ratio, but the excessive or insufficient duty ratio can affect the balance of the system, so that other devices such as a limiter and the like can be configured to limit the size of the duty ratio by combining the actual application scene and the working parameters of the power conversion circuit in the design.

In one possible design, the electrical quantity is the output current;

In one possible design, the electrical quantity is the output voltage;

the virtual resistance value is obtained based on the alternating current component with the largest amplitude value in the output voltage and the corresponding relation between the virtual resistance value and the largest alternating current component;

the target voltage is obtained by bandpass filtering the output voltage based on the resonance frequency or the sum of the resonance frequency and a second margin threshold, and the second filter bandwidth, wherein the second margin threshold is larger than zero.

In one possible design, before adjusting the pulse width modulated signal of the power conversion circuit based on the alternating current component with the largest amplitude in the electrical quantity output by the power conversion circuit, the method further includes:

identifying the alternating current component with the largest amplitude as the largest alternating current component based on the amplitude of at least one alternating current component;

the resonance frequency is the center frequency of the filtering parameter corresponding to the alternating current component with the largest amplitude in at least one alternating current quantity.

the resonant frequency is a frequency corresponding to an alternating current component having a largest amplitude among the at least one alternating current component.

Drawings

FIG. 1a is a schematic diagram of a power converter cascade system;

FIG. 1b is a schematic diagram of yet another power converter cascade system;

FIG. 1c is a schematic diagram of yet another power converter cascade system;

fig. 2 is a schematic application diagram of a power converter according to an embodiment of the present application;

fig. 3 is a schematic structural diagram of a power conversion circuit according to an embodiment of the present application;

fig. 4 is a schematic diagram of a current signal spectrum according to an embodiment of the present application;

FIG. 5a is a schematic diagram of a correspondence relationship between virtual resistance values and maximum AC component values according to an embodiment of the present disclosure;

FIG. 5b is a schematic diagram of another virtual resistance-maximum AC component correspondence provided in an embodiment of the present application;

fig. 6 is a schematic flow chart of a resonance suppression method according to an embodiment of the present application;

FIG. 7 is a logic diagram of another resonance suppression algorithm provided in an embodiment of the present application;

fig. 8 is a schematic flow chart of a target duty cycle obtaining method according to an embodiment of the present application;

fig. 9a is a schematic flow chart of a virtual resistance identification method according to an embodiment of the present application;

fig. 9b is a schematic flow chart of a virtual current obtaining method according to an embodiment of the present application;

FIG. 10a is a flowchart illustrating another virtual resistance identification method according to an embodiment of the present disclosure;

fig. 10b is a flowchart of another virtual current obtaining method according to an embodiment of the present application;

Fig. 11a is a schematic flow chart of a method for identifying a resonant frequency according to an embodiment of the present application;

fig. 11b is a flowchart of another method for identifying a resonant frequency according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, a photovoltaic optimizer cascade system will be taken as an example, and the application scenario and the technical problems to be solved of the present application will be described below.

In the field of new energy power generation, a power converter cascading mode is generally adopted to realize the functions of direct current conversion and alternating current-direct current conversion of different voltage levels.

For example, in a photovoltaic power generation scene, the photovoltaic optimizer cascade system comprises a photovoltaic array, a plurality of photovoltaic optimizers, inverters and loads, wherein a first end of a direct current conversion circuit of each photovoltaic optimizer is used for being connected with the photovoltaic array, a second end of the direct current conversion circuit of each photovoltaic optimizer is connected in series and then connected with the inverter, the inverter is used for being connected with the loads, and a control end of the direct current conversion circuit of each photovoltaic optimizer is connected with the corresponding controller.

In the running process, the actual working point of the photovoltaic optimizer is greatly influenced by weather change, so that the output impedance change of the cascade system of the photovoltaic optimizer is obvious, the noise frequency and the resonance frequency of the current in the transmission process tend to be consistent, the resonance energy is not consumed, and the resonance current on a circuit between the photovoltaic optimizer and the inverter is overlarge.

In some scenes, because the control parameters of the photovoltaic optimizer are unreasonably designed, the resonant frequency of a circuit between the photovoltaic power optimizer and the inverter approaches or reaches the switching frequency of the direct current conversion circuit, and the high-frequency resonant current of the circuit between the photovoltaic power optimizer and the inverter is also caused, so that the problems of circuit and device loss, hardware cost increase, photovoltaic system operation stability reduction and the like are easily caused by the larger resonant current.

For example, due to factors such as unreasonable configuration of line parameters, change of running state of the converter, etc., peak-to-peak value of high-frequency resonance current on a line between the photovoltaic optimizer and the inverter is larger than a threshold value, thereby causing interruption of communication of the programmable control logic controller. Furthermore, if the duration of the overlarge high-frequency resonant current is longer than the set value, the inverter is also shut down due to a system protection mechanism, so that the generated energy is lost.

Therefore, for the scenario of power converter cascading, it is necessary to suppress the resonant current on the power converter output line.

It should be understood that the application scenario of the present application is not limited to a photovoltaic power generation scenario, but may be other scenarios;

for example, as shown in fig. 1a, in the structure diagram of a power converter cascade system in the energy storage application scenario, a first end of a DC-DC converter 102 is connected to an energy storage battery 101, a second end of the DC-DC converter 102 is connected to a first end of a DC-AC converter 103, and a second end of the DC-AC converter 103 is connected to an AC load 104; it should be noted that, the DC-DC converter 102 may be integrated with the energy storage battery 101 in an energy storage system, and the DC-AC converter 103 may be an inverter.

The power converter of the present application may be the DC-DC converter 102 and the DC-AC converter 103 in this application scenario, and a large resonant current may exist on the cable L between the DC-DC converter 102 and the DC-AC converter 103.

For another example, as shown in fig. 1b, in the structure diagram of the power converter cascade system in the light and storage integrated scene, the photovoltaic array 105 is connected to the first end of the photovoltaic optimizer 106, the second end of the photovoltaic optimizer 106 is connected to the DC-AC converter 103, the DC-AC converter 103 is connected to the AC load 104, the first end of the DC-DC converter 102 is connected to the energy storage battery 101, and the second end of the DC-DC converter 102 is connected to the DC-AC converter 103; it should be noted that, the DC-DC converter 102 may be integrated with the energy storage battery 101 in an energy storage system, and the DC-AC converter 103 may also be an inverter.

The power converter of the present application may be the photovoltaic optimizer 106, the DC-DC converter 102, and the DC-AC converter 103 in this application scenario, where a larger resonant current may occur on the cable L1 between the photovoltaic optimizer 106 and the DC-AC converter 103, and a larger resonant current may exist on the cable L2 between the DC-DC converter 102 and the DC-AC converter 103.

For another example, as shown in the power converter cascade system architecture diagram of fig. 1c, a photovoltaic optimizer 106 is connected between a photovoltaic array 105 and a DC-AC converter 103, the DC-AC converter 103 being connected to an AC load 104; the DC-AC converter 103 may be an inverter.

The power converter of the present application may be the photovoltaic optimizer 106 and the DC-AC converter 103 in this application scenario, and a large resonant current may exist on the cable L between the photovoltaic optimizer 106 and the DC-AC converter 103.

It will be appreciated that various modifications and variations to the present application may be made by those skilled in the art without departing from the spirit and scope of the present application, so as to solve the problem of excessive resonant current on the converter cascade cable of fig. 1 a-1 c, and it is intended to include such modifications and variations.

Based on the above-mentioned problems, embodiments of the present application provide a power converter and a resonance suppression method, which are used for solving the problem that the peak-to-peak value of the resonance current on the output line of the power converter is too large.

The uninterruptible power supply system provided by the exemplary embodiments of the present application will be described below with reference to the accompanying drawings in conjunction with the above-described application scenario, and it should be noted that the above-described application scenario is only shown for the convenience of understanding the principles of the present application, and embodiments of the present application are not limited in this respect.

In addition, in the description of the present application, "at least one" means one or more, wherein a plurality means two or more. In view of this, the term "plurality" may also be understood as "at least two" in the embodiments of the present application.

The embodiment of the present application provides a power conversion circuit, as shown in fig. 2, an output terminal of a power converter a is used for being connected with an input terminal of another power converter (shown as a power converter B in fig. 2, and a larger harmonic current may exist on a cable L between the power converter a and the power converter B), where the power converter a includes a controller 201 and a power conversion circuit 202;

the power converters a and B may be photovoltaic optimizers, DC-DC converters, and DC-AC converters as shown in fig. 1a to 1c, or may be other devices for power conversion.

It should be noted that, the power conversion circuit 202 may be a DC-DC conversion circuit or a DC-AC conversion circuit; in addition, besides the scenario of cascading between a single power converter and a single power converter, the embodiments of the present application are also applicable to the scenario of cascading multiple power converters, which will not be described in detail below.

The controller 201 is configured to adjust the pulse width modulation signal output to the power conversion circuit 202 based on the ac component with the largest amplitude among the electric quantities output from the power conversion circuit 202.

The frequency of the pulse width modulated signal after adjustment includes a resonant frequency, which is the frequency of the ac component with the largest amplitude among the amounts of electricity output from the power conversion circuit 202.

In fig. 2, the dashed line with an arrow indicates that the controller 201 obtains the amount of electric power output from the power conversion circuit 202 on the cable L, and the dashed line with an arrow indicates that the controller 201 outputs a pulse width modulation signal to the power conversion circuit 202.

Since the pulse width modulation signal does not need to be adjusted according to the dc component in the electrical quantity, a high-pass filter may be disposed in the power converter a, and the high-pass filter may filter out low-frequency components such as the dc component in the electrical quantity output by the power conversion circuit 202, so as to avoid the dc component from affecting the accuracy of resonance suppression.

Based on the technical solution of the embodiment of the present application, the controller 201 outputs a pulse width modulation signal whose frequency component includes a resonant frequency, so as to achieve the technical effect of increasing the output impedance of the power conversion circuit for the resonant frequency, where the effect is equivalent to connecting a physical resistor in series to the cable L between the power converter a and the power converter B, where the physical resistor can consume resonant energy, so that the noise frequency on the cable L of the power converter a is inconsistent with the resonant frequency, thereby suppressing the resonant current;

Furthermore, the technical scheme of the embodiment of the application increases the output impedance aiming at the specific resonant frequency, does not influence other frequencies, and ensures the output stability of the power converter;

for example, as shown in fig. 2, the original frequency of the pulse width modulation signal before adjustment is 15kHz, and the resonance frequency of the output cable L current of the power conversion circuit 202 is 10kHz, then the frequency components of the pulse width modulation signal after adjustment include the original frequency 15kHz and the resonance frequency 10kHz; if the frequency component of the pulse width modulated signal after adjustment includes a frequency component of 8kHz in addition to 15kHz, the resonant current cannot be reduced, but increases.

Finally, since the present embodiment adjusts the output impedance of the power conversion circuit by using an active damping method, no additional hardware cost is required and no additional loss is required.

For ease of understanding, several methods of obtaining electrical quantities of the present application are illustrated with the power conversion circuit 202 being a DC-DC conversion circuit:

firstly, it should be noted that the type of electrical quantity required by the controller for resonance suppression may be an output voltage or an output current;

further, as shown in fig. 3, an input terminal AA 'of the DC-DC conversion circuit 202 is connected to the power supply device 301, and an output terminal BB' of the DC-DC conversion circuit 202 is connected to the power conversion device 302 through a cable L; wherein the power conversion device 302 may be a DC-AC converter or a DC-DC converter.

The first capacitor C1 and the resistor R in the DC-DC conversion circuit 202 are connected in series to the power supply device 301, the first switching tube Q1 is respectively connected with the resistor R, the first end of the inductor L1 and the first end of the second switching tube Q2, the second end of the first inductor L1 is respectively connected with the negative electrode of the diode D and the positive electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 and the positive electrode of the diode D are connected with the negative electrode of the first capacitor.

In one possible implementation, the sampler collects the current and voltage on the cable L between the DC-DC conversion circuit 202 and the power conversion device 302, resulting in an output current and an output voltage of the DC-DC conversion circuit 202.

In another possible implementation manner, the sampler collects the voltage of the second capacitor C2, and since the second capacitor C2 is an output capacitor, the output voltage of the DC-DC conversion circuit 202 can be obtained, and further, the capacitance current can be calculated according to the differential amount of the output voltage and the capacitance value of the second capacitor C2; the sampler collects the current of the first inductor L1 to obtain an inductor current; therefore, the sum of the capacitance current and the inductance current can be used as the output current of the DC-DC conversion circuit 202.

Those skilled in the art will appreciate that the amount of electricity output by the power conversion circuit 202 may be obtained by other methods commonly used in the art, and will not be described in detail herein.

The following expands on how the power converter shown in fig. 2 suppresses the resonance current:

since the frequency of the adjusted pulse width modulated signal includes the resonant frequency, the power converter a needs to obtain the resonant frequency:

in a possible embodiment, the controller 201 is configured to bandpass filter the electrical quantities based on a plurality of filter parameters, respectively, to obtain at least one ac component.

The center frequencies of the respective filter parameters are different from each other and the bandwidths are the same.

It can be understood that the electrical quantity output by the power conversion circuit may include a direct current component and an alternating current component, and the application only needs to increase virtual impedance to the alternating current component, so as to consume energy corresponding to the resonant frequency to suppress the resonant current, so that components which do not need to be suppressed need to be filtered;

In practical applications, a band-pass filter, which is a device that allows waves of a specific frequency band to pass while shielding other frequency bands, may be used for band-pass filtering.

For example, if the current output by the power conversion circuit 202 passes through a plurality of band-pass filters with different center frequencies and the same preset bandwidth, the ac component corresponding to the center frequency is left, the ac component with the non-center frequency is filtered, and the controller 201 can further identify the magnitude of the left ac component, so as to obtain the center frequency corresponding to the ac component with the largest magnitude, that is, the resonant frequency.

For example, four bandpass filters 1-4 are provided in the controller 201, assuming a bandwidth of 1kHz for each bandpass filter, a center frequency of 15kHz for bandpass filter 1, a center frequency of 16kHz for bandpass filter 2, a center frequency of 17kHz for bandpass filter 3, and a center frequency of 18kHz for bandpass filter 4. The four band-pass filters respectively carry out band-pass filtering on the electric quantity output by the power conversion circuit to obtain a plurality of alternating current components with different frequencies;

further, the controller 201 calculates the effective value of the filtered electric quantity at each frequency in a period of time as the amplitude of the alternating current component, and obtains 400mA for the effective value of current corresponding to 15kHz, 50mA for the effective value of current corresponding to 16kHz, 40mA for the effective value of current corresponding to 17kHz, and 40mA for the effective value of current corresponding to 18kHz. Thus, the maximum alternating current component is 400mA and the resonant frequency is 15kHz;

It should be understood that the controller 201 may also calculate the sum of squares of the electric quantities output by the power conversion circuit 202 over a period of time, and take the largest sum of squares as the amplitude of the ac component, which is not described herein.

Based on the embodiment, components of frequencies other than the center frequency are attenuated through a plurality of filtering parameters, and amplitude calculation and identification are performed on the filtering electric quantity of a plurality of different frequencies through a controller, so that the maximum value of the alternating electric quantity and the resonant frequency are obtained, the virtual resistance value is further increased for the resonant frequency, and the peak-to-peak value of the resonant current is reduced.

In a possible implementation, the controller 201 is configured to perform a fast fourier transform (fast fourier transform, FFT) on the ac component of the electrical quantity output by the power conversion circuit, to obtain at least one ac component;

It can be appreciated that the amount of electricity output by the power conversion circuit 202 may include a dc component and an ac component, and this embodiment only needs to add a virtual impedance to the ac component, so as to consume energy corresponding to the resonant frequency to suppress the resonant current, and thus needs to filter out components that do not need to be suppressed.

Taking the electrical quantity output by the power conversion circuit 202 as an output current as an example, the controller 201 performs fast fourier transform on the output current, and displays a component with a frequency amplitude of zero, that is, a direct current component of the output current, a component with a frequency amplitude of non-zero, that is, an alternating current component of the output current, and a frequency corresponding to the alternating current component with the largest amplitude of the output current, that is, a resonant frequency.

Illustratively, the controller 201 is provided with a frequency analysis circuit, which performs a fast fourier transform on waveform data of the output current of the power conversion circuit, resulting in the current signal spectrum shown in fig. 4.

By observing the correspondence between the frequency indicated by the frequency spectrum and the amplitude of the alternating current component, the alternating current component with the largest amplitude is 400mA, and the corresponding frequency is 15kHz, so that the maximum alternating current component is 400mA and the resonance frequency is 15kHz.

Based on the present embodiment, the controller 201 performs fast fourier transform on the electrical quantity to obtain the maximum ac component of the electrical quantity and the resonant frequency corresponding to the maximum ac component, so as to further increase the virtual resistance for the resonant frequency, thereby reducing the peak-to-peak value of the resonant current and avoiding the influence on the ac components of other frequencies.

In one possible embodiment, the adjusted pulse width modulated signal includes a target duty cycle in addition to the resonant frequency, the target duty cycle being derived based on the product of the virtual current and the virtual resistance value;

the virtual current is obtained according to the resonant frequency;

In one embodiment, the electrical quantity is an output current, and the virtual resistance value and the virtual current may be obtained by:

it will be appreciated that the greater the amplitude of the maximum ac component of the amount of power on the output cable of the power conversion circuit, the greater the virtual resistance that needs to be increased to dissipate the resonant energy and thereby suppress the resonant current.

It should be noted that, the preset correspondence between the virtual resistance value and the maximum ac component may be a linear positive correlation or a nonlinear positive correlation, so as to ensure that the increased virtual resistance value is sufficient to reduce the amplitude of the resonant current.

Exemplary, the correspondence between the virtual resistance and the maximum ac component obtained through the simulation experiment is shown in fig. 5a, and the virtual resistance and the maximum value of the ac electric quantity are in a linear relationship. Since the resistance of the virtual resistor which can be increased by the active damping method is limited by the system hardware architecture, the maximum resistance Rmax and the corresponding first maximum value Sup, and the minimum resistance Rmin and the corresponding second maximum value Sdn are set. In addition, the correspondence between the virtual resistance value and the maximum ac component may be a nonlinear relationship as shown in fig. 5b, which is not described herein.

for example, in the practical application process, the lower phase of the output current of the power conversion circuit can affect the suppression effect, so that the resonant frequency can be adjusted to be slightly larger;

for example, the controller 201 obtains a resonant frequency of 14kHz, the preset first margin threshold is 1kHz, the controller 201 includes a band-pass filter, the center frequency of the band-pass filter should be set to 15kHz, and the band-pass filter band-pass filters the output current based on the center frequency of 15kHz and the first filtering bandwidth of 2kHz, so as to obtain the virtual current.

Based on the embodiment, the controller carries out band-pass filtering on the output current based on the resonance frequency or the sum of the resonance frequency and the first margin threshold value, so that the influence of other frequencies is avoided; in addition, the energy of the resonant current is determined according to the virtual current, the resistance value of the virtual resistor is reasonably adjusted, and the output impedance of the power conversion circuit is equivalently increased, so that the harmonic current is restrained within a reasonable range; furthermore, the design mode of active damping reduces the influence on the output steady state of the power conversion circuit and reduces the hardware cost.

In another embodiment, the electrical quantity is an output voltage, and the virtual resistance value and the virtual current may be obtained by:

the method for obtaining the virtual resistance refers to the related content of the virtual resistance, which is not described herein.

The virtual current is the product of the target voltage and the output capacitance of the power conversion circuit.

It should be appreciated that the capacitance-based current calculation formula shows that the capacitance current is equal to the product of the voltage differential and the capacitance value, and thus the virtual current can be calculated based on the product of the target voltage and the output capacitance value of the power conversion circuit.

It should be noted that, the target voltage is obtained by bandpass filtering the output voltage based on the resonant frequency or the sum of the resonant frequency and the second margin threshold, and the second filter bandwidth; wherein the second margin threshold is greater than zero.

The principle and implementation of the second margin threshold may refer to the related description of the first margin threshold, which is not repeated here.

Based on the embodiment, the controller carries out band-pass filtering on the output voltage based on the resonance frequency or the sum of the resonance frequency and the second margin threshold value, so that the influence of other frequencies is avoided; in addition, the virtual current is calculated according to the voltage, so that the energy of the resonant current is determined, the resistance value of the virtual resistor is reasonably adjusted, the output impedance of the power conversion circuit is equivalently increased, and the harmonic current is restrained within a reasonable range; furthermore, the design mode of active damping reduces the influence on the output steady state of the power conversion circuit and reduces the hardware cost.

Based on the above embodiments, the virtual resistance value and the virtual current may be multiplied to obtain a corresponding voltage value and then converted into a duty cycle, where the duty cycle is further used to adjust the pwm signal, but since the excessive or insufficient duty cycle affects the system balance, the voltage value obtained by multiplying the virtual resistance value and the virtual current also needs to be limited to obtain the target duty cycle.

In one possible embodiment, after obtaining the virtual current and the virtual resistance value, the target duty cycle may be obtained by:

if the product of the virtual current and the virtual resistance is larger than or equal to a preset first voltage threshold, the target duty ratio is obtained based on the first voltage threshold; or alternatively

In summary, the present application provides a power converter, where a controller of the power converter obtains a resonant frequency corresponding to a resonant current, and outputs a pulse width modulation signal including the resonant frequency to increase an output impedance of a power conversion circuit, which is equivalent to connecting a physical resistor in series to an output end of the power conversion circuit, and consumes excessive resonant energy, thereby suppressing the resonant current.

Based on the same technical concept, the embodiment of the application also provides a resonance suppression method, which is applied to the power converter shown in fig. 2; the implementation of the method can refer to the implementation of the power converter, and the repetition is not repeated;

As shown in fig. 6, the method includes:

in step 601, the controller adjusts the pulse width modulation signal of the power conversion circuit based on the ac component with the largest amplitude among the electrical quantities output from the power conversion circuit to the other power converter.

The frequency of the pulse width modulation signal after adjustment includes a resonant frequency, which is the frequency of the ac component with the largest amplitude in the electrical quantity output by the power conversion circuit.

It should also be noted that the electrical quantity output by the power conversion circuit includes, but is not limited to, an output voltage or an output current.

In step 602, the power conversion circuit outputs a voltage based on the adjusted pulse width modulated signal.

In the cascade system of power converters, the noise frequency is identical to or close to the resonance frequency, so that the resonance energy is not consumed, and thus, a resonance current exists, and therefore, the impedance on the connecting cable of the cascade power converter needs to be increased to consume the resonance energy, so that the resonance current is suppressed.

Based on the technical scheme of the embodiment, the controller of the power converter can use voltage or current to carry out resonance control, and the application range is wider.

For ease of understanding, the following describes the algorithm logic of resonance suppression of the controller in conjunction with the resonance suppression method shown in fig. 6:

as shown in a control logic schematic diagram of a resonance suppression algorithm in fig. 7, firstly, a controller performs direct current filtering on an electric quantity output by an input power conversion circuit, filters a direct current component and a low frequency component in the electric quantity, retains an alternating current component, and secondly, the controller performs resonance frequency self-adaptive identification on the alternating current component, and outputs a resonance frequency and a maximum alternating current component; further, the controller adjusts the center frequency of the band-pass filtering according to the resonance frequency or the sum of the resonance frequency and a preset margin thereof, virtual current is obtained in a band-pass filtering mode, and in addition, the controller identifies a virtual resistance according to the maximum alternating current component and the corresponding relation between the maximum alternating current component and the virtual resistance; and finally, the virtual current and the virtual resistance value pass through a multiplier and a limiter to output a target duty ratio.

The following description of the resonance suppression method with respect to fig. 6 and 7 will be explained:

in one possible embodiment, the adjusted pulse width modulated signal includes a target duty cycle in addition to the resonant frequency, the target duty cycle being based on a product of the virtual current and the virtual resistance value;

the virtual current is obtained according to the resonant frequency;

It can be appreciated that the controller can obtain a corresponding voltage value based on the product of the virtual resistance value and the virtual current to be converted into a target duty cycle to adjust the pulse width modulation signal, thereby controlling the output of the power conversion circuit.

However, it should be noted that, although the virtual resistance value is multiplied by the virtual current to obtain a corresponding voltage value and then convert the voltage value into the duty ratio, the system balance is affected by too large or too small duty ratio, so that other devices such as a limiter and the like can be configured to limit the size of the duty ratio in combination with the actual application scenario and the working parameters of the power conversion circuit.

In one possible implementation, the target duty cycle may be obtained by the method shown in fig. 8:

in step 801, the controller obtains a virtual current and a virtual resistance. If the product of the virtual current and the virtual resistance is greater than or equal to the first voltage threshold, step 802 is performed; if the product of the virtual current and the virtual resistance is less than or equal to the second voltage threshold, step 803 is performed; if the product of the virtual current and the virtual resistance is greater than the second voltage threshold and less than the first voltage threshold, step 804 is performed.

At step 802, the controller generates a target duty cycle based on a first voltage threshold.

In step 803, the controller generates a target duty cycle based on the second voltage threshold.

In step 804, the controller generates a target duty cycle based on the product of the virtual current and the virtual resistance.

Since the target duty ratio needs to be generated based on the product of the virtual current and the virtual resistance, how to obtain the virtual current and the virtual resistance is described as follows:

in one possible implementation, where the electrical quantity is the output current, the virtual resistance value may be identified as shown in fig. 9 a:

in step 9011, the controller obtains the ac component of the output current having the greatest amplitude.

In step 9012, the virtual resistance is obtained based on the ac component with the largest amplitude in the output current and the preset virtual resistance-maximum ac component correspondence.

In one possible implementation, where the electrical quantity is the output current, the virtual current may be obtained as shown in fig. 9 b:

in step 9021, the controller acquires the resonant frequency.

In step 9022, the virtual current is obtained by bandpass filtering the output current based on the resonant frequency or a sum of the resonant frequency and the first margin threshold, and the first filter bandwidth.

It should be noted that the first margin threshold is greater than zero.

In one possible implementation, the electrical quantity is the output voltage, and the virtual resistance value can be identified as shown in fig. 10 a:

in step 10011, the controller obtains the ac component with the largest amplitude in the output voltage.

In step 10012, the virtual resistance is obtained based on the ac component with the largest amplitude in the output voltage and the correspondence between the virtual resistance and the largest ac component.

In one possible implementation, where the electrical quantity is the output voltage, the virtual current may be obtained as shown in fig. 10 b:

in step 10021, the controller acquires a resonant frequency.

In step 10022, the target voltage is obtained by bandpass filtering the output voltage based on the resonance frequency or the sum of the resonance frequency and the second margin threshold, and the second filter bandwidth.

It should be noted that the second margin threshold is greater than zero.

In step 10023, the virtual current is the product of the target voltage and the output capacitance of the power conversion circuit.

In one possible implementation, before adjusting the pulse width modulation signal of the power conversion circuit based on the ac component with the largest amplitude in the electrical quantity output by the power conversion circuit, the controller may further identify the resonant frequency by the method shown in fig. 11 a:

in step 11011, the controller performs band-pass filtering on the electrical quantities based on the plurality of filtering parameters, respectively, to obtain at least one ac component.

In step 11012, the controller identifies the ac component having the greatest magnitude as the largest ac component based on the magnitude of the at least one ac component.

In step 11013, the resonant frequency is the center frequency of the filtering parameter corresponding to the ac component with the largest amplitude in the at least one ac quantity.

It should be appreciated that the controller may calculate the sum of squares or the effective value of the output electrical quantities of the power conversion circuit over a period of time, taking the maximum sum of squares or the maximum effective value thereof as the magnitude of the ac component.

In one possible implementation, before adjusting the pulse width modulation signal of the power conversion circuit based on the ac component with the largest amplitude in the electrical quantity output by the power conversion circuit, the controller may further identify the resonant frequency by the method shown in fig. 11 b:

in step 11021, the ac component of the electric quantity output from the power conversion circuit is subjected to fast fourier transform to obtain at least one ac component.

For example, the electric quantity output by the power conversion circuit is an output current, the controller performs fast fourier transform on the output current, and displays a component with a frequency amplitude of zero, namely a direct current component of the output current, a component with a frequency amplitude of non-zero, namely an alternating current component of the output current, and a frequency corresponding to an alternating current component with a maximum amplitude of the output current, namely a resonant frequency.

In step 11022, the resonant frequency is a frequency corresponding to an ac component having a largest amplitude among the at least one ac component.

Based on the embodiment, the controller performs fast Fourier transform on the electric quantity to obtain the maximum alternating current component of the electric quantity and the resonant frequency corresponding to the maximum alternating current component, so that the virtual resistance is further increased for the resonant frequency, the peak-to-peak value of the resonant current is reduced, and the influence on other frequency alternating current components is avoided.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.

Claims

1. A power converter, wherein an output of the power converter is configured to be coupled to an input of another power converter, the power converter comprising a controller and a power conversion circuit;

2. The power converter of claim 1 wherein the pulse width modulated signal after adjustment includes a target duty cycle, the target duty cycle being based on a product of a virtual current and a virtual resistance value;

the virtual current is obtained according to the resonant frequency;

the virtual resistance value is obtained according to the alternating current component with the largest amplitude value in the electric quantity.

3. The power converter of claim 2, wherein the target duty cycle is derived based on a preset first voltage threshold if a product of the virtual current and the virtual resistance is greater than or equal to the first voltage threshold; or alternatively

And if the product of the virtual current and the virtual resistance is larger than the second voltage threshold and smaller than the first voltage threshold, the target duty ratio is obtained based on the product of the virtual current and the virtual resistance.

4. A power converter as claimed in claim 2 or 3, wherein the electrical quantity is an output current;

the virtual resistance value is obtained based on the alternating current component with the largest amplitude value in the output current and a preset virtual resistance value-largest alternating current component corresponding relation;

the virtual current is obtained by bandpass filtering the output current based on the resonant frequency or the sum of the resonant frequency and a first margin threshold, and a first filtering bandwidth, wherein the first margin threshold is larger than zero.

5. A power converter as claimed in claim 2 or 3, wherein the electrical quantity is an output voltage;

the virtual resistance value is obtained based on the alternating current component with the largest amplitude value in the output voltage and a preset virtual resistance value-largest alternating current component corresponding relation;

the target voltage is obtained by carrying out band-pass filtering on the output voltage based on the resonance frequency or the sum of the resonance frequency and a second margin threshold value and a second filtering bandwidth; wherein the second margin threshold is greater than zero.

6. The power converter of any of claims 1-5, wherein the controller is further to:

the resonant frequency is the center frequency of the filtering parameter corresponding to the alternating current component with the largest amplitude in the at least one alternating current component.

7. The power converter of any of claims 1-5, wherein the controller is further to:

the resonant frequency is the frequency corresponding to the alternating current component with the largest amplitude in the amplitude of the at least one alternating current component.

8. A method of resonance suppression, the method comprising:

and adjusting a pulse width modulation signal of the power conversion circuit based on the alternating current component with the largest amplitude in the electric quantity output to the other power converter by the power conversion circuit, wherein the frequency of the pulse width modulation signal after adjustment comprises a resonance frequency, and the resonance frequency is the frequency of the alternating current component with the largest amplitude in the electric quantity output by the power conversion circuit.

9. The resonance suppression method as recited in claim 8, wherein the adjusted pulse width modulated signal includes a target duty cycle, the target duty cycle being a product of a virtual current and a virtual resistance value;

the virtual current is obtained according to the resonant frequency;

10. The resonance suppression method as set forth in claim 9, wherein the target duty cycle is based on a product of a virtual current and a virtual resistance value, comprising:

generating the target duty cycle based on a first voltage threshold if the product of the virtual current and the virtual resistance is greater than or equal to the first voltage threshold;

generating the target duty cycle based on a second voltage threshold if the product of the virtual current and the virtual resistance is less than or equal to the second voltage threshold;

and if the product of the virtual current and the virtual resistance is larger than the second voltage threshold and smaller than the first voltage threshold, generating the target duty ratio based on the product of the virtual current and the virtual resistance.

11. The resonance suppression method as claimed in claim 9 or 10, wherein the electrical quantity is the output current;

12. The resonance suppression method as claimed in claim 9 or 10, wherein the electrical quantity is the output voltage;

the target voltage is obtained by bandpass filtering the output voltage based on the resonance frequency or the sum of the resonance frequency and a second margin threshold, and a second filtering bandwidth, wherein the second margin threshold is larger than zero.

13. The resonance suppression method as recited in any one of claims 8-12, wherein the method further comprises, prior to adjusting the pulse width modulated signal of the power conversion circuit based on the alternating current component of the greatest magnitude of the electrical quantity output by the power conversion circuit:

identifying the alternating current component with the largest amplitude as the largest alternating current component based on the amplitude of the at least one alternating current component;

the resonance frequency is the center frequency of the filtering parameter corresponding to the alternating current component with the largest amplitude in the at least one alternating current quantity.

14. The resonance suppression method as recited in any one of claims 8-12, wherein the method further comprises, prior to adjusting the pulse width modulated signal of the power conversion circuit based on the alternating current component of the greatest magnitude of the electrical quantity output by the power conversion circuit:

the resonant frequency is the frequency corresponding to the alternating current component with the largest amplitude in the at least one alternating current component.