阅读说明：本技术 一种逆变器输出滤波电感电流振荡抑制方法和抑制装置 (Inverter output filter inductive current oscillation suppression method and suppression device ) 是由 孙帅 郑群 张涛 耿后来 程林 伍永富 于 2019-09-24 设计创作，主要内容包括：本申请公开了一种逆变器输出滤波电感电流振荡抑制方法和抑制装置,以抑制当逆变器脉宽调制过程中注入的共模分量和/或差模分量的谐波频率与逆变器输出滤波器的截止频率接近或重叠时,所引起的逆变器输出滤波电感电流振荡。该方法包括：实时跟踪在逆变器输出滤波器的截止频率变化范围内,逆变器输出滤波电感电流的能量最大时所对应的截止频率点；随所述截止频率点的变化动态调整滤波环节的参数,以抑制逆变器输出滤波电感电流的振荡；其中,所述滤波环节设置在逆变器脉宽调制过程中注入的共模分量和/或差模分量的输出上。(The application discloses an inverter output filter inductive current oscillation suppression method and a suppression device, which are used for suppressing inverter output filter inductive current oscillation caused when the harmonic frequency of a common mode component and/or a differential mode component injected in the inverter pulse width modulation process is close to or overlapped with the cut-off frequency of an inverter output filter. The method comprises the following steps: tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time; dynamically adjusting parameters of a filtering link along with the change of the cut-off frequency point so as to inhibit oscillation of filtering inductance current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.)

1. An inverter output filter inductor current oscillation suppression method is characterized by comprising the following steps:

tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time;

dynamically adjusting parameters of a filtering link along with the change of the cut-off frequency point so as to inhibit oscillation of filtering inductance current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

2. The inverter output filter inductor current oscillation suppression method according to claim 1, wherein the real-time tracking is performed on a cut-off frequency point corresponding to a maximum energy of the inverter output filter inductor current within a cut-off frequency variation range of the inverter output filter, and specifically includes:

discrete Fourier Transform (DFT) analysis is carried out on the inverter output filter inductive current to obtain the distribution characteristic of the energy of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter, and the cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current is determined based on the distribution characteristic.

3. The inverter output filter inductor current oscillation suppression method according to claim 1, wherein the filtering element is a wave trap, a band-pass filter, a low-pass filter or a high-pass filter.

4. The method for suppressing oscillation of an inverter output filter inductor current according to claim 3, wherein when the filter element employs a trap filter, the dynamically adjusting parameters of the filter element with the variation of the cut-off frequency point to suppress oscillation of the inverter output filter inductor current comprises:

in the current control period, taking any cut-off frequency of the mth subinterval as the center point frequency of the wave trap; the method comprises the following steps that a cut-off frequency interval of an output filter of an inverter is divided into n subintervals in advance, the mth subinterval is a subinterval with the largest energy of the output filter inductive current of the inverter, n is larger than or equal to 3, and m is larger than or equal to 1 and smaller than or equal to n; then calculating the energy average value P of the inverter output filter inductive current in the cut-off frequency variation range_m；

In the next control period, the cut-off frequency of the (m + 1) th subinterval is takenThe frequency is taken as the center point frequency of the trap filter, and then the energy average value P 'of the inverter output filter inductance current in the cut-off frequency variation range is calculated'_m；

Will P_m-P′_mComparing the size with +/-B, wherein B is more than 0;

if (P)_m-P′_m) If the frequency of the central point of the wave trap is larger than B, the central point frequency of the wave trap is disturbed towards the direction of reducing the frequency until the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after disturbance is within-B, B]Stopping disturbance when the range is within;

if (P)_m-P′_m) And B, the central point frequency of the wave trap is kept to be disturbed towards the direction of increasing frequency until the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after disturbance falls into B, B]Stopping disturbance when the range is within;

if-B is less than or equal to (P)_m-P′_m) B is less than or equal to B, and the center point frequency of the wave trap is not changed.

5. The inverter output filter inductor current oscillation suppression method of claim 4, wherein each subinterval is of equal length, and each perturbation step is one subinterval in length.

6. The inverter output filter inductor current oscillation suppression method according to claim 1, wherein the real-time tracking is performed before a cut-off frequency point corresponding to a time when the energy of the inverter output filter inductor current is maximum within a cut-off frequency variation range of the inverter output filter, and further comprising:

calculating the energy average value of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter;

and judging that the energy average value is larger than a preset value.

7. The method of claim 1, wherein the energy level of the inverter output filter inductor current is measured by the energy level of the common mode current when the inverter output filter capacitor is brought back to the bus midpoint.

8. An inverter output filter inductor current oscillation suppression device, comprising:

the frequency tracking unit is used for tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time;

the parameter adjusting unit is used for dynamically adjusting the parameters of the filtering link along with the change of the cut-off frequency point so as to inhibit the oscillation of the filtering inductive current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

9. The inverter output filter inductor current oscillation suppression device according to claim 8, wherein the frequency tracking unit is specifically configured to perform DFT analysis on the inverter output filter inductor current to obtain a distribution characteristic of energy of the inverter output filter inductor current in a cut-off frequency variation range of an inverter output filter, and determine a cut-off frequency point corresponding to a maximum energy of the inverter output filter inductor current based on the distribution characteristic.

10. The inverter output filter inductor current oscillation suppression device of claim 8, further comprising:

the trigger condition judgment unit is used for calculating the energy average value of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter; and judging whether the energy average value is larger than a preset value or not, and if so, triggering the frequency tracking unit.

Technical Field

The invention relates to the technical field of power electronics, in particular to a method and a device for suppressing oscillation of an output filter inductive current of an inverter.

Background

When the harmonic frequency of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process is close to or overlapped with the cut-off frequency of an inverter output filter, resonance can occur, so that the oscillation of the inverter output filter inductive current is caused, and the problems of system instability, even inverter off-line and the like are caused. Therefore, it is necessary to effectively suppress the inverter output filter inductor current oscillation.

Disclosure of Invention

In view of the above, the present invention provides a method and a device for suppressing oscillation of inverter output filter inductor current, so as to suppress oscillation of inverter output filter inductor current caused when a harmonic frequency of a common mode component and/or a differential mode component injected during inverter pulse width modulation approaches or overlaps a cutoff frequency of an inverter output filter.

An inverter output filter inductor current oscillation suppression method comprises the following steps:

tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time;

dynamically adjusting parameters of a filtering link along with the change of the cut-off frequency point so as to inhibit oscillation of filtering inductance current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

Optionally, the real-time tracking is performed on a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductor current within a cut-off frequency variation range of the inverter output filter, and specifically includes:

discrete Fourier Transform (DFT) analysis is carried out on the inverter output filter inductive current to obtain the distribution characteristic of the energy of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter, and the cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current is determined based on the distribution characteristic.

Optionally, the filtering step uses a wave trap, a band-pass filter, a low-pass filter or a high-pass filter.

Optionally, when the filter element adopts a wave trap, the parameters of the filter element are dynamically adjusted along with the change of the cut-off frequency point to suppress oscillation of the inverter output filter inductor current, which specifically includes:

in the current control period, taking any cut-off frequency of the mth subinterval as the center point frequency of the wave trap; the method comprises the following steps that a cut-off frequency interval of an output filter of an inverter is divided into n subintervals in advance, the mth subinterval is a subinterval with the largest energy of the output filter inductive current of the inverter, n is larger than or equal to 3, and m is larger than or equal to 1 and smaller than or equal to n; then calculating the energy average value P of the inverter output filter inductive current in the cut-off frequency variation range_m；

In the next control period, taking the cut-off frequency of the (m + 1) th subinterval as the center point frequency of the wave trap, and then calculating the energy average value P 'of the inverter output filter inductance current in the cut-off frequency variation range'_m；

Will P_m-P′_mComparing the size with +/-B, wherein B is more than 0;

if (P)_m-P′_m) If the frequency of the central point of the wave trap is larger than B, the central point frequency of the wave trap is disturbed towards the direction of reducing the frequency until the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after disturbance is within-B, B]Stopping disturbance when the range is within;

if (P)_m-P′_m) And B, the central point frequency of the wave trap is kept to be disturbed towards the direction of increasing frequency until the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after disturbance falls into B, B]Stopping disturbance when the range is within;

if-B is less than or equal to (P)_m-P′_m) B is less than or equal to B, and the center point frequency of the wave trap is not changed.

Optionally, the length of each subinterval is equal, and each perturbation step is the length of one subinterval.

Optionally, the real-time tracking further includes, in a cut-off frequency variation range of an inverter output filter, before a cut-off frequency point corresponding to a time when the energy of the inverter output filter inductor current is maximum:

calculating the energy average value of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter;

and judging that the energy average value is larger than a preset value.

Optionally, when the output filter capacitor of the inverter is led back to the midpoint of the bus, the energy of the output filter inductor current of the inverter is measured by using the energy of the common-mode current.

An inverter output filter inductor current oscillation suppression device, comprising:

the frequency tracking unit is used for tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time;

the parameter adjusting unit is used for dynamically adjusting the parameters of the filtering link along with the change of the cut-off frequency point so as to inhibit the oscillation of the filtering inductive current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

Optionally, the frequency tracking unit is specifically configured to perform DFT analysis on the inverter output filtered inductor current to obtain a distribution characteristic of energy of the inverter output filtered inductor current in a cut-off frequency variation range of an inverter output filter, and determine a cut-off frequency point corresponding to a time when the energy of the inverter output filtered inductor current is maximum based on the distribution characteristic.

Optionally, the inverter output filter inductor current oscillation suppression device further includes:

the trigger condition judgment unit is used for calculating the energy average value of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter; and judging whether the energy average value is larger than a preset value or not, and if so, triggering the frequency tracking unit.

According to the technical scheme, the filtering link is added to the output of the common-mode component and/or the differential-mode component injected in the inverter pulse width modulation process, and because the cut-off frequency point corresponding to the maximum oscillation amplitude of the inverter output filtering inductance current changes in real time, the filtering link tracks the cut-off frequency point in real time and dynamically adjusts the parameters of the filtering link along with the change of the cut-off frequency point, so that the self-adaptability of the filtering link in the process of inhibiting the inverter output filtering inductance current from oscillating is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a method for suppressing oscillation of an inverter output filter inductor current according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a topology structure of an output LC filter of a single-phase inverter disclosed in the prior art;

FIG. 3 is a flowchart illustrating a method for implementing step S02 in FIG. 1;

fig. 4 is a flowchart of another inverter output filter inductor current oscillation suppression method disclosed in the embodiment of the present invention;

fig. 5 is a schematic structural diagram of an inverter output filter inductor current oscillation suppression device according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of another inverter output filter inductor current oscillation suppression device disclosed in the embodiment of the present invention.

Detailed Description

For reference and clarity, the terms, abbreviations or abbreviations used hereinafter are summarized as follows:

SVPWM: space Vector Pulse Width Modulation;

DPWM: discontinuous Pulse Width Modulation;

DFT: discrete Fourier Transform, Discrete Fourier Transform;

DFT analysis: DFT analysis is the most basic method for signal analysis, and the DFT analysis transforms a signal from a time domain to a frequency domain, thereby researching the frequency spectrum structure and the change rule of the signal.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, an embodiment of the present invention discloses a method for suppressing oscillation of inverter output filter inductor current, which is used to suppress oscillation of inverter output filter inductor current caused when a harmonic frequency of a common mode voltage and/or a differential mode voltage injected in an inverter pulse width modulation process is close to or overlaps with a cut-off frequency of an inverter output filter. The inverter output filter inductive current oscillation suppression method specifically comprises the following steps:

step S01: and tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time.

Specifically, common types of inverter output filters are an output LC filter, an output LCL filter, and the like, and a filter inductor L (i.e., an inverter output filter inductor) and a filter capacitor C are important components in the inverter output filter.

In terms of topology, the filter capacitor C may or may not be led back to the bus midpoint, the inverter may be a single-phase inverter or a three-phase inverter, and fig. 2 only takes the example that the filter capacitor C in the single-phase inverter output LC filter is led back to the bus midpoint.

When the harmonic frequency of the common mode voltage and/or the differential mode voltage injected in the inverter pulse width modulation (such as SVPWM or DPWM modulation) process is close to or overlapped with the cut-off frequency of the inverter output filter, resonance occurs, which causes the current (hereinafter referred to as the inductor current I) flowing through the filter inductor L to oscillate, the inductance of the filter inductor L is not fixed but varies with the variation of the inductor current I, and the cut-off frequency variation range [ f1, f2] of the inverter output filter can be obtained according to the variation curve of the inductance of the filter inductor L with the inductor current I. Within the cut-off frequency variation range [ f1, f2] of the inverter output filter, the cut-off frequency point corresponding to the maximum oscillation amplitude of the inductive current I (i.e. the maximum energy of the inductive current I) is also varied in real time.

The embodiment of the invention can track the cut-off frequency point corresponding to the maximum energy of the inductive current I in the cut-off frequency variation range of the output filter of the inverter in real time by adopting the following method: DFT analysis is carried out on the inductive current I, distribution characteristics of the energy of the inductive current I in a cutoff frequency variation range [ f1, f2] of an inverter output filter are obtained, and a cutoff frequency point corresponding to the maximum energy of the inductive current I can be directly obtained on the basis of the distribution characteristics.

Step S02: dynamically adjusting parameters of a filtering link along with the change of the cut-off frequency point so as to inhibit oscillation of filtering inductance current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

Specifically, since the cut-off frequency point when the oscillation amplitude of the inductor current I is maximum is changed in real time, if the filtering link is a filtering link with fixed parameters, the adaptability of the filtering link for suppressing the oscillation of the inductor current I is poor, and the embodiment of the invention dynamically adjusts the parameters of the filtering link along with the change of the cut-off frequency point, the adaptability is strong, and the energy in the upper and lower preset ranges of the cut-off frequency point can be always filtered to the maximum extent.

The filtering unit can adopt a wave trap, a band-pass filter, a low-pass filter or a high-pass filter, and is not limited. The filtering element may be implemented in electronic hardware, computer software, or a combination of both.

A specific implementation manner of the step S02 is given below only by taking a wave trap as an example of the filtering element, as shown in fig. 3, where the step S02 includes:

step S021: in the current control period, taking any cut-off frequency of the mth subinterval as the center point frequency of the wave trap; the cutoff frequency interval of the output filter of the inverter is divided into n subintervals in advance, the mth subinterval is the subinterval with the largest energy of the output filter inductive current of the inverter, n is larger than or equal to 3, and m is larger than or equal to 1 and smaller than or equal to n.

Specifically, the length of each subinterval may be equal or different. For convenience of control and calculation, the embodiment of the present invention recommends setting the length of each subinterval to be equal.

Step S022: calculating the energy average value P of the inverter output filter inductive current in the cut-off frequency variation range_m；

Step S023: in the next control period, the cut-off frequency of the (m + 1) th subinterval is taken as the center point frequency of the wave trap, namely, the disturbance is firstly carried out towards the direction of increasing the center point frequency of the wave trap.

Step S024: calculating the energy average value P 'of the inverter output filter inductance current in the variation range of the cut-off frequency'_m；

Step S025: will P_m-P′_mComparing the size with +/-B, wherein B is more than 0; if (P)_m-P′_m) If yes, go to step S026; if (P)_m-P′_m) < -B, go to step S027; if-B is less than or equal to (P)_m-P′_m) And (B), determining that the center point frequency of the wave trap reaches the cut-off frequency point when the oscillation amplitude of the inductive current I is maximum, and entering the step S028.

Step S026: and (3) the central point frequency of the wave trap is disturbed towards the direction of reducing the frequency until the disturbance is stopped when the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after the disturbance falls in the range of [ -B, B ]. The disturbance step length of each disturbance needs to ensure that the currently selected cut-off frequency can fall to the next subinterval, and when the length of each subinterval is equal, the disturbance step length is set as the length of one subinterval.

Step S027: and (3) the central point frequency of the wave trap is disturbed towards the direction of increasing the frequency until the disturbance is stopped when the difference of the energy average values of the inverter output filter inductance current in the cut-off frequency variation range before and after the disturbance falls in the range of [ -B, B ]. The disturbance step length of each disturbance needs to ensure that the currently selected cut-off frequency can fall into the next subinterval.

Step S028: the disturbance is stopped, i.e. the center point frequency of the trap is not changed.

In summary, in the embodiments of the present invention, a filtering link is added to the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process, and since the cut-off frequency point corresponding to the maximum oscillation amplitude of the inverter output filtering inductor current changes in real time, the embodiments of the present invention track the cut-off frequency point in real time and dynamically adjust the parameter of the filtering link along with the change of the cut-off frequency point, thereby realizing the adaptivity of the filtering link in the process of suppressing the oscillation of the inverter output filtering inductor current, and avoiding the problems of system instability, even the inverter off-line, and the like.

In addition, when the filter capacitor C is led back to the bus midpoint, if the harmonic frequency of the injected common-mode voltage is close to or overlapped with the cut-off frequency of the inverter output filter, the oscillation of the inverter output filter inductive current can also cause the oscillation of the common-mode current flowing into the bus midpoint, so that the bus ripple is increased, and the service life and reliability of the bus capacitor are reduced.

Optionally, when the filter capacitor C is led back to the midpoint of the bus, the energy of the filter inductor current output by the inverter may be measured by using the energy of the common mode current, and the common mode current may be acquired by additionally adding a common mode loop sensor.

Optionally, as shown in fig. 4, an embodiment of the present invention further discloses another inverter output filter inductor current oscillation suppression method, including:

step S401: calculating the energy average value P of the inverter output filter inductive current in the cut-off frequency variation range of the inverter output filter;

step S402: judging whether the energy average value P is larger than a preset value A or not, if P is larger than A, indicating that the oscillation amplitude of the inductive current I is large and needs to be inhibited, and then entering step S403; if P is less than or equal to a, it indicates that the oscillation amplitude of the inductor current I is very small and can be ignored without being suppressed, and then the process returns to step S401.

Step S403: and tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time.

Step S404: dynamically adjusting parameters of a filtering link along with the change of the cut-off frequency point so as to inhibit oscillation of filtering inductance current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

Corresponding to the above method embodiment, the embodiment of the present invention further discloses an inverter output filter inductor current oscillation suppression apparatus, as shown in fig. 5, including:

the frequency tracking unit 100 is used for tracking a cut-off frequency point corresponding to the maximum energy of the inverter output filter inductive current within the cut-off frequency variation range of the inverter output filter in real time;

the parameter adjusting unit 200 is configured to dynamically adjust parameters of a filtering link along with changes of the cut-off frequency point, so as to suppress oscillation of a filtering inductor current output by the inverter; the filtering link is arranged on the output of the common mode component and/or the differential mode component injected in the inverter pulse width modulation process.

Optionally, the frequency tracking unit 100 is specifically configured to perform DFT analysis on the inverter output filtered inductor current, obtain a distribution characteristic of energy of the inverter output filtered inductor current in a cut-off frequency variation range of the inverter output filter, and determine, based on the distribution characteristic, a cut-off frequency point corresponding to a time when the energy of the inverter output filtered inductor current is maximum.

Optionally, the filtering step uses a wave trap, a band-pass filter, a low-pass filter or a high-pass filter.

Optionally, as shown in fig. 6, the inverter output filter inductor current oscillation suppression device further includes:

a trigger condition determining unit 300, configured to calculate an energy average value of the inverter output filter inductor current within a cut-off frequency variation range of the inverter output filter; and judging whether the energy average value is larger than a preset value or not, and if so, triggering the frequency tracking unit 100.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.