CN108667378B - Single-resistor phase-shift current sampling method and device - Google Patents

Abstract

The invention discloses a single-resistor phase-shift current sampling method and a single-resistor phase-shift current sampling device, wherein the method judges whether all non-zero vector action time is greater than minimum current sampling time according to a three-phase PWM duty ratio; if yes, collecting bus currents of 4 non-zero vector action time middle points in each period, and calculating a two-phase current value; if not, a PWM phase shifting method for ensuring the starting state of the non-zero vector is not changed is adopted to carry out phase shifting, the bus current is acquired by adopting a bus current unstability time phase current calculation method for the non-zero vector with the increased non-zero vector action time, the bus current at the midpoint of the non-zero vector with the original non-zero vector action time larger than the minimum current sampling time is acquired, a two-phase current value is calculated, and a three-phase current value is determined according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value. The invention can effectively collect phase current in the current sampling blind area and avoid current collection errors caused by abnormal current transformation due to unstable bus current and phase shift.

Description

Single-resistor phase-shift current sampling method and device

Technical Field

The invention relates to the technical field of single-resistor phase-shift current sampling, in particular to a single-resistor phase-shift current sampling method and a single-resistor phase-shift current sampling device.

Background

The single-resistor current sampling principle is that the sampling resistor installed on the DC bus is used for collecting the DC bus current, and then the three-phase current value is determined according to the corresponding relation between the DC bus current and the motor phase current under different switch states.

However, the single resistance current sampling technique has a sampling dead zone where the base vector action time is less than the minimum current sampling time Tmin, which affects current sampling, and although the problem of current sampling in the sampling dead zone can be solved by using a PWM (Pulse Width Modulation) phase shift method, the method needs to move the PWM of one or two phases to ensure that the base voltage vector action time is greater than Tmin, as shown in fig. 1, the action times of V2 and V3 after phase shifting are both greater than Tmin, and the sampled current values at V2 and V3 are the current values of the corresponding two phases. Even if the starting state of the non-zero vector before and after phase shifting is ensured to be the same, the average value of the phase current is still difficult to acquire, as shown in fig. 3, when the phase current I before the phase shifting is smaller, as shown in fig. 2, because the phase current before the phase shifting is < Ts 0.5 x T, the bus current is not stable, and the phase current after the phase shifting is increased, but only the phase current at the time before the phase shifting is 0.5 x T, the average phase current in the acting time of the non-zero vector before the phase shifting can be represented, and at this time, the bus current is not stable and cannot be acquired.

However, the phase shift algorithm has current sampling errors, because each phase current changes according to the change of the switching state of the bridge arm in the whole PWM period, the phase shift can cause the change of the waveform of the three-phase current in the PWM period, and particularly when a new vector is inserted, the abnormal change of the current can be caused, and the current sampling precision is seriously influenced. As shown in FIG. 1, the phase shift causes different non-zero voltage vector action time of the first half period of PWM, so that the three-phase current in the process of V3 after the phase shift has an error with the three-phase current in the process of V3 before the phase shift.

Disclosure of Invention

The invention aims to provide a single-resistor phase-shifting current sampling method and a single-resistor phase-shifting current sampling device, which can effectively acquire phase current in a current sampling blind area and avoid current acquisition errors caused by abnormal current transformation due to unstable bus current and phase shifting.

In order to achieve the purpose, the invention provides the following technical scheme:

a single-resistor phase-shift current sampling method comprises the following steps:

judging whether all non-zero vector action time is greater than the minimum current sampling time according to the three-phase PWM duty ratio;

if yes, collecting bus current of 4 non-zero vector action time middle points in each period, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value;

if not, a PWM phase shifting method for ensuring the starting state of the non-zero vector is adopted to shift the phase, a bus current is acquired by adopting a bus current unstability time phase current calculation method for the non-zero vector with increased non-zero vector acting time, the bus current at the midpoint of the non-zero vector with the original non-zero vector acting time larger than the minimum current sampling time is acquired, a two-phase current value is calculated, and a three-phase current value is determined according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value.

Specifically, the step of collecting bus currents at 4 non-zero vector action time midpoints in each period, calculating a two-phase current value, and determining a three-phase current value according to a corresponding relationship between a three-phase PWM duty ratio and the two-phase current value includes:

setting 4 sections of non-zero vector action time, namely two ends V2 and two ends V3, in a PWM period, acquiring bus current in a V2 action period as phase A current, and acquiring bus current in a V3 action period as a negative value of phase C current;

the bus current is sampled at the middle moment of the two ends V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

The bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., the phase current of C, i.e., Ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

Specifically, the step of shifting the phase by using a PWM phase shift method that ensures that the starting state of the non-zero vector is not changed, collecting the bus current of the non-zero vector with increased acting time of the non-zero vector by using a bus current unstability time phase current calculation method, collecting the bus current with the acting time of the original non-zero vector being greater than the midpoint of the minimum current sampling time, calculating a two-phase current value, and determining the three-phase current value according to the corresponding relationship between the three-phase PWM duty ratio and the two-phase current value includes:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

Sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.: ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

A single resistance phase-shifting current sampling apparatus, comprising:

the judging unit is used for judging whether all the non-zero vector action time is greater than the minimum current sampling time according to the three-phase PWM duty ratio;

the first calculation unit is used for collecting bus currents of 4 non-zero vector action time midpoints in each period when all the non-zero vector action time is greater than the minimum current sampling time, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value;

and the second calculation unit is used for shifting the phase by adopting a PWM phase-shifting method which ensures that the starting state of the non-zero vector is unchanged when the acting time of all the non-zero vectors is not greater than the minimum current sampling time, acquiring the bus current of the non-zero vector with the increased acting time of the non-zero vector by adopting a bus current unstability time phase current calculation method, acquiring the bus current of a middle point of the non-zero vector with the original acting time of the non-zero vector greater than the minimum current sampling time, calculating a two-phase current value, and determining the three-phase current value according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value.

Specifically, the first calculating unit is configured to:

setting 4 sections of non-zero vector action time, namely two ends V2 and two ends V3, in a PWM period, acquiring bus current in a V2 action period as phase A current, and acquiring bus current in a V3 action period as a negative value of phase C current;

the bus current is sampled at the middle moment of the two ends V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

The bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.: ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

Specifically, the second calculating unit is configured to:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.:

I_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2

sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.:

Ic＝(-1)*I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2

determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

According to the technical scheme, compared with the prior art, the invention discloses a single-resistor phase-shift current sampling method and a single-resistor phase-shift current sampling device, wherein the method judges whether all non-zero vector action time is greater than the minimum current sampling time according to a three-phase PWM duty ratio; if yes, collecting bus currents of 4 non-zero vector action time midpoints in each period, and calculating a two-phase current value; if not, a PWM phase shifting method for ensuring the starting state of the non-zero vector is adopted to shift the phase, a bus current is acquired by adopting a bus current unstability time phase current calculation method for the non-zero vector with increased non-zero vector acting time, the bus current at the midpoint of the non-zero vector with the original non-zero vector acting time larger than the minimum current sampling time is acquired, a two-phase current value is calculated, and a three-phase current value is determined according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value.

The single-resistor phase-shift current sampling method and the single-resistor phase-shift current sampling device increase the action time of a basic vector with too short action time by using a PWM phase-shift method for ensuring that the starting state of a non-zero vector of current sampling is unchanged, ensure that the action starting state of the basic vector is the same as the state without phase shift, sample and calculate the average value of phase currents in the action period of the basic vector under the condition without phase shift by using a bus current unstable time phase current calculation method, can effectively collect phase currents in a current sampling blind area, and avoid current collection errors caused by abnormal current transformation due to unstable bus currents and phase shift.

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 embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of phase currents sampled by a single resistance phase-shifted current in the prior art;

FIG. 2 is a graph of current before and after phase shifting under the same starting state in the prior art;

fig. 3 is a schematic flow chart of a single-resistor phase-shift current sampling method according to an embodiment of the present invention;

FIG. 4 is a graph of current before and after phase shifting under the same starting conditions provided by the embodiment of the present invention;

FIG. 5 is a schematic diagram of a PWM cycle including 4 non-zero vector active times according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of PWM waveforms before and after single resistance phase shifting according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a single-resistor phase-shifting current sampling apparatus according to an embodiment of the present invention.

Detailed Description

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. 3, an embodiment of the present invention provides a single-resistor phase-shift current sampling method, which specifically includes the following steps:

s301, judging whether all non-zero vector action time is greater than minimum current sampling time according to the three-phase PWM duty ratio, if so, executing a step S302; if not, go to step S303.

Specifically, as shown in fig. 4, under the condition that the starting state of the non-zero vector is guaranteed to be unchanged, the acting time of the non-zero vector is increased through phase shifting, as shown in fig. 4, at times T1 and T2, bus currents (at this time, the bus currents are phase currents) are collected twice, I _1 and I _2, and the current I at the time of the middle time (T is before phase shifting/2) of the non-zero vector acting is calculated according to the following formula, and the current is the average value of the phase currents in the non-zero vector acting time period before phase shifting.

S302, collecting bus currents of 4 non-zero vector action time middle points in each period, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value.

Specifically, when all the non-zero vector action time is greater than the minimum current sampling time, the three-phase PWM signal is directly controlled and output to trigger the driving circuit according to conventional algorithm software without phase shift processing, and each period is divided into 7 sections of processes. During the active vector action time, the bus current is equal to one phase current of the three-phase currents (IA, IB, IC).

The method comprises the following steps of collecting bus currents of 4 non-zero vector action time midpoints in each period, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value, wherein the three-phase current value comprises the following steps:

setting 4 non-zero vector action time segments in a PWM period, as shown in FIG. 5, namely two ends V2 and two ends V3, wherein the bus current collected in the action period of V2 is the phase A current, and the bus current collected in the action period of V3 is the negative value of the phase C current;

the bus current is sampled at the middle moment of the two ends V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.:

I_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2

the bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.:

Ic＝(-1)*I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0–I_A-I_C。

S303, shifting the phase by adopting a PWM phase shifting method for ensuring the starting state of the non-zero vector to be unchanged, collecting the bus current of the non-zero vector with increased non-zero vector action time by adopting a bus current unstability time phase current calculation method, collecting the bus current of a midpoint of the non-zero vector with the original non-zero vector action time being greater than the minimum current sampling time, calculating a two-phase current value, and determining the three-phase current value according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value.

Specifically, when the action time of all non-zero vectors is not greater than the minimum current sampling time, a PWM phase-shifting method that ensures that the starting state of the non-zero vectors is unchanged is required to perform phase-shifting processing, and then a bus current unstability time phase current calculation method is used to acquire the bus current for the non-zero vectors with increased non-zero vector action time.

The principle of the phase current calculation method when the bus current is not stable is as follows: in the non-zero vector acting period, the circuit can be approximately equivalent to LR current, the phase current transformation trend is an exponential function, and the phase current transformation trend can be approximately considered to be an inclined straight line because the non-zero vector acting time and the electromagnetic time constant t of the circuit are smaller than L/R, so that the average value of the phase current in the non-zero vector acting period is equal to the instantaneous value of the phase current at the middle moment.

Under the condition that the starting state of the non-zero vector is guaranteed to be unchanged, the acting time of the non-zero vector is increased through phase shifting, as shown in fig. 4, bus currents (namely phase currents) are collected twice at the moments T1 and T2, I _1 and I _2 are obtained, the current I at the moment of the middle moment of the non-zero vector acting (T is equal to the phase current before the phase shifting/2) is calculated according to the following formula, and the current is the average value of the currents in the non-zero vector acting time period before the phase shifting.

The PWM phase shifting method for ensuring the non-zero vector starting state of the current sampling is as follows, the non-zero vector acting time at the current sampling position is increased through phase shifting, and meanwhile, the action time sequence of three-phase voltage is not changed in a period of time before the non-zero vector, so that the non-zero vector starting state is ensured to be the same as the non-zero vector starting state before the phase shifting when the non-zero vector acting time is increased.

As shown in FIG. 6, in a specific example, the non-zero vectors V1_1 and V1_2 have an action time less than the minimum sampling time Tmin, and the phase shifting method in the figure is a PWM phase shifting method that ensures that the starting state of the non-zero vector where the current is sampled is unchanged. The upper graph in FIG. 6 is the waveform without phase shift, and the action time of V1_1 and V1_2 in each cycle is too short to be sampled by the minimum sampling time. As shown in FIG. 6, the shaded portion is moved to the right a distance, which increases the action time of V1_2 in Cycle1 and V1_1 in Cycle 3.

The time lengths of V2_1 and V2_2 in the Cycle1 after phase shifting are not changed, and the action time sequence of three-phase voltage in the previous Cycle (Cycle4) is the same as that before phase shifting, so that the current is sampled at the middle moment between V2_1 and V2_2 of the Cycle1 to obtain I2_1 and I2_2, namely the average current in V2_1 and V2_2 before phase shifting; after the phase shift, the action time of V1_2 in the Cycle1 is increased, the action time sequence of three-phase voltage in a period before V1_2 is the same as that before the phase shift, so the starting state of V1_2 is consistent with that before the phase shift, and the average current I1_2 in V1_2 before the phase shift can be calculated by adopting a bus current unstability time phase current calculation method in V1_ 2; after the phase shift, the action time of V1_1 in the Cycle3 is increased, the action time sequence of three-phase voltage in a period before V1_1 is the same as that before the phase shift, so the starting state of V1_1 is consistent with that before the phase shift, and the average current I1_1 in V1_1 before the phase shift can be calculated by adopting a bus current unstability time phase current calculation method in V1_ 1; finally, two-phase average currents I1 and I2 can be calculated according to I2_1, I2_2, I1_2 and I1_ 1.

I1＝(I1_2+I1_1)/2；

I2＝(I2_2+I2_1)/2；

Specifically, the PWM phase shifting method for ensuring that the starting state of the non-zero vector where the current sampling is located is not changed is implemented in various ways, not limited to that shown in fig. 6, and the key principle is to ensure that the starting state of the non-zero vector where the current sampling is located is not changed.

The method comprises the following steps of performing phase shifting by adopting a PWM phase shifting method for ensuring that the starting state of a non-zero vector is unchanged, acquiring bus current for the non-zero vector with increased non-zero vector action time by adopting a bus current unstability time phase current calculation method, acquiring the bus current with original non-zero vector action time larger than the minimum current sampling time midpoint, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value, wherein the method comprises the following steps:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.:

I_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2

sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.:

Ic＝(-1)*I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2

determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

It should be noted that the three-phase current value is determined according to the correspondence between the three-phase PWM duty ratio and the two-phase current value, and the three-phase current value is determined according to table 1.

TABLE 1 corresponding relationship between three-phase current and I1 and I2

Note: DutyA, DutyB, DutyC represent the duty cycle of A, B, C three-phase PWM.

The invention discloses a single-resistor phase-shifting current sampling method, which utilizes a PWM phase-shifting method for ensuring that the starting state of a non-zero vector of current sampling is unchanged to increase the action time of a basic vector with too small action time and ensure that the action starting state of the basic vector is the same as the state without phase shifting, and utilizes a bus current unstable time phase current calculation method to sample and calculate the average value of phase currents in the action period of the basic vector under the condition without phase shifting, thereby effectively acquiring the phase currents in a current sampling blind area and avoiding current acquisition errors caused by current abnormal transformation due to bus current instability and phase shifting.

The invention also discloses a corresponding device on the basis of the method.

The single-resistor phase-shift current sampling device provided in the embodiments of the present invention is described below, and it should be noted that the description of the single-resistor phase-shift current sampling device may refer to the single-resistor phase-shift current sampling method provided above, and details are not described below.

Referring to fig. 7, an embodiment of the present invention provides a single-resistor phase-shifting current sampling apparatus, which specifically includes: a determination unit 701, a first calculation unit 702, and a second calculation unit 703, wherein:

a judging unit 701, configured to judge whether all non-zero vector action times are greater than the minimum current sampling time according to a three-phase PWM duty cycle;

a first calculating unit 702, configured to, when all the non-zero vector action times are greater than the minimum current sampling time, acquire bus currents at midpoints of 4 non-zero vector action times in each period, calculate a two-phase current value, and determine a three-phase current value according to a correspondence between a three-phase PWM duty ratio and the two-phase current value;

a second calculating unit 703, configured to, when the acting time of all non-zero vectors is not all greater than the minimum current sampling time, perform phase shifting by using a PWM phase shifting method that ensures that the starting state of the non-zero vectors is unchanged, acquire a bus current for the non-zero vector whose acting time of the non-zero vector is increased by using a bus current unstability time phase current calculating method, acquire a bus current at a midpoint of the non-zero vector whose acting time of the non-zero vector is greater than the minimum current sampling time, calculate a two-phase current value, and determine a three-phase current value according to a corresponding relationship between a three-phase PWM duty ratio and the two-phase current value.

Specifically, the first calculating unit 702 is configured to:

setting 4 sections of non-zero vector action time, namely two ends V2 and two ends V3, in a PWM period, acquiring bus current in a V2 action period as phase A current, and acquiring bus current in a V3 action period as a negative value of phase C current;

the bus current is sampled at the middle moment of the two ends V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.:

I_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2

the bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.:

Ic＝(-1)*I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2

determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

Specifically, the second calculating unit 603 is configured to:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

Sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., the phase current of C, i.e., Ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

The invention discloses a single-resistor phase-shifting current sampling device, which utilizes a PWM phase-shifting method for ensuring that the starting state of a non-zero vector of current sampling is unchanged to increase the action time of a basic vector with too small action time and ensure that the starting state of the basic vector action is the same as the state without phase shifting, and utilizes a bus current unstable time phase current calculation method to sample and calculate the average value of phase currents in the action period of the basic vector under the condition without phase shifting, thereby effectively acquiring the phase current in a current sampling blind area and avoiding current acquisition errors caused by abnormal current transformation due to unstable bus current and phase shifting.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in an article or device that comprises the element.

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 invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (2)

1. A single-resistor phase-shift current sampling method is characterized by comprising the following steps:

judging whether all non-zero vector action time is greater than the minimum current sampling time according to the three-phase PWM duty ratio;

if yes, collecting bus current of 4 non-zero vector action time middle points in each period, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value;

if not, performing phase shifting by adopting a PWM phase shifting method for ensuring the starting state of the non-zero vector to be unchanged, increasing the acting time of the non-zero vector at the current sampling position, acquiring the bus current of the non-zero vector with the increased acting time of the non-zero vector by adopting a bus current unstability time phase current calculation method, acquiring the bus current of a midpoint of the non-zero vector with the acting time of the original non-zero vector being greater than the minimum current sampling time, calculating a two-phase current value, and determining the three-phase current value according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value;

the method comprises the following steps of collecting bus currents of 4 non-zero vector action time midpoints in each period, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value, wherein the method comprises the following steps:

setting 4 sections of non-zero vector action time, namely two sections of V2 and two sections of V3, in a PWM period, acquiring bus current in a V2 action period as phase A current, and acquiring bus current in a V3 action period as a negative value of phase C current;

the bus current is sampled at the middle moment of two segments of V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

The bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., the phase current of C, i.e., Ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

According to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value andthe sum of the three-phase currents is zero, and a third phase current value I is determined_B＝0-I_A-I_C；

The method comprises the following steps of performing phase shift processing by adopting a PWM phase shift method which ensures that the starting state of a non-zero vector is unchanged, increasing the acting time of the non-zero vector at a current sampling position, collecting bus current of the non-zero vector with the increased acting time of the non-zero vector by adopting a bus current unstability time phase current calculation method, collecting the bus current of which the acting time of the original non-zero vector is greater than the midpoint of the minimum current sampling time, calculating a two-phase current value, and determining the three-phase current value according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value, wherein:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

Sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.: ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

2. A single resistance phase-shifted current sampling apparatus, comprising:

the judging unit is used for judging whether all the non-zero vector action time is greater than the minimum current sampling time according to the three-phase PWM duty ratio;

the first calculation unit is used for collecting bus currents of 4 non-zero vector action time midpoints in each period when all the non-zero vector action time is greater than the minimum current sampling time, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value;

the second calculation unit is used for performing phase shifting treatment by adopting a PWM phase shifting method for ensuring that the starting state of a non-zero vector is unchanged when all the non-zero vector action time is not greater than the minimum current sampling time, increasing the non-zero vector action time at a current sampling position, collecting bus current for the non-zero vector with the increased non-zero vector action time by adopting a bus current unstability time phase current calculation method, collecting the bus current of a middle point for the non-zero vector with the original non-zero vector action time greater than the minimum current sampling time, calculating a two-phase current value, and determining a three-phase current value according to the corresponding relation between a three-phase PWM duty ratio and the two-phase current value;

wherein the first computing unit is to:

setting 4 sections of non-zero vector action time, namely two sections of V2 and two sections of V3, in a PWM period, acquiring bus current in a V2 action period as phase A current, and acquiring bus current in a V3 action period as a negative value of phase C current;

the bus current is sampled at the middle moment of two segments of V2 to obtain I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.: i is_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2；

The bus current is sampled at the middle moment of two segments of V3 to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.: ic (-1) × I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2；

Determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C；

Wherein the second computing unit is to:

setting a PWM period including 4 sections of non-zero vector action time, and adopting a PWM phase-shifting method for ensuring the starting state of the non-zero vector to shift the phase to eliminate a sampling blind area;

collecting bus current by bus current unstability time phase current calculation method for non-zero vector with increased action time, and measuring I_{1_1}，I_{1_2}Taking the average value I_1AVRI.e., phase a current, i.e.:

I_A＝I_1AVR＝(I_{1_1}+I_{1_2})/2

sampling bus current at the middle time of non-zero vector with unchanged action time to obtain I_{2_1}，I_{2_2}Taking the average value I_2AVRI.e., phase C current, i.e.:

Ic＝(-1)*I_2AVR＝(-1)*(I_{2_1}+I_{2_2})/2

determining a third phase current value I according to the corresponding relation between the three-phase PWM duty ratio and the two-phase current value and the condition that the sum of the three-phase currents is zero_B＝0-I_A-I_C。

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