阅读说明：本技术 倍频单电阻电流采样方法及其装置 (Frequency multiplication single resistance current sampling method and device thereof ) 是由 李柏松 陈伟 成爱军 时迎亮 李武君 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种倍频单电阻电流采样方法及其装置,该方法包括以下步骤：a、对PWM控制算法计算出的三相占空比进行调整,获得调整后的三相占空比；b、根据调整后的三相占空比计算电流采样时刻t-(s1)、t-(s2)、t-(s3)和t-(s4)；c、按照调整后的三相占空比输出三相电压；d、在电流采样时刻t-(s1)、t-(s2)、t-(s3)和t-(s4)进行电流采样,根据电流采样结果分别重构出载波周期的前半个周期和后半个周期的三相电流,进而获得载波周期的三相平均电流。本发明可以提高单电阻电流采样方法的电流采样精度。(The invention discloses a frequency multiplication single-resistor current sampling method and a device thereof, wherein the method comprises the following steps: a. adjusting the three-phase duty ratio calculated by the PWM control algorithm to obtain the adjusted three-phase duty ratio; b. calculating current sampling time t according to the adjusted three-phase duty ratio s1 、t s2 、t s3 And t s4 (ii) a c. Outputting three-phase voltage according to the adjusted three-phase duty ratio; d. at the current sampling time t s1 、t s2 、t s3 And t s4 And carrying out current sampling, and respectively reconstructing three-phase currents of the first half period and the second half period of the carrier period according to current sampling results so as to obtain the three-phase average current of the carrier period. The invention can improve the current sampling precision of the single-resistor current sampling method.)

1. A frequency multiplication single resistance current sampling method is characterized by comprising the following steps:

a. three-phase duty ratio D [ a ] calculated by PWM control algorithm]、D[b]、D[c]Adjusting to obtain the adjusted three-phase duty ratio D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c](ii) a Wherein D is₁[a]、D₁[b]、D₁[c]Three-phase duty cycle, D, being one of the first half or the second half of the carrier cycle₂[a]、D₂[b]、D₂[c]A three-phase duty cycle that is the other of the first half cycle or the second half cycle of the carrier cycle;

b. calculating current sampling time t according to the adjusted three-phase duty ratio_s1、t_s2、t_s3And t_s4；

c. Outputting three-phase voltage according to the adjusted three-phase duty ratio;

d. at the current sampling time t_s1、t_s2、t_s3And t_s4And respectively carrying out current sampling, and respectively reconstructing three-phase currents of the first half period and the second half period of the carrier period according to current sampling results so as to obtain the three-phase average current of the carrier period.

2. The frequency-doubled single-resistor current sampling method according to claim 1, wherein step a comprises:

a1, three-phase duty ratio D [ a ] calculated by PWM control algorithm]、D[b]、D[c]Sorting according to the size sequence to obtain the maximum value D_maxMiddle value D_midMinimum value D_minAnd recording the maximum value D_maxMiddle value D_midAnd a minimum value D_minIf the corresponding phase is a phase a, a phase b or a phase c, making Max represent the serial number of the phase corresponding to the maximum value of the duty ratio, Mid represent the serial number of the phase corresponding to the intermediate value of the duty ratio, and Min represent the serial number of the phase corresponding to the minimum value of the duty ratio; when the three-phase duty ratios are equal, firstly, appointing any one-phase duty ratio as a maximum value, then appointing any one-phase duty ratio in the rest two-phase duty ratios as an intermediate value, and appointing the rest one-phase duty ratio as a minimum value; when the two-phase duty ratios are equal, designating any one phase of the equal two-phase duty ratios as a large value and designating the other phase of the equal two-phase duty ratios as a small value;

a2, calculation D_maxAnd D_midDifference D of_xdAnd D_midAnd D_minDifference D of_dn：

Wherein D is_max、D_midAnd D_minAre respectively the three-phase duty ratio D [ a ]]、D[b]、D[c]Maximum, intermediate and minimum values of;

a3, according to D_xdAnd D_dnObtaining a first temporary calculated variable D_xd1A second temporary calculated variable D_dn1A third temporary calculated variable D_xd2And a fourth temporary calculated variable D_dn2：

In the above formula,. DELTA.D_xdAnd Δ D_dnAre respectively D_xdAnd D_dnAdjustment of (D), Δ D_xdAnd Δ D_dnThe value taking mode is as follows: in the following six groups Δ D_xdAnd Δ D_dnSix groups of delta D solved by the calculation formula_xdAnd Δ D_dnIn (1), selecting Δ D_xdAnd Δ D_dnThe set of solutions with the smallest sum is used as the actual Δ D_xdAnd Δ D_dn；

The six formulas are respectively as follows:

wherein D is_Ts＝T_s2/T, wherein T is a carrier period, and Ts is a preset minimum sampling window; the functions fun1() and fun2() are defined as follows:

for D calculated by the above formula_xd1、D_dn1、D_xd2、D_dn2The final D is obtained by limiting according to the following limiting rule_xd1、D_dn1、D_xd2、D_dn2：

If D is_xd1And D_dn1Sum greater than 1, D_xd1And D_dn1Is unchanged for the smaller of D_xd1And D_dn1The larger of which becomes 1 minus the smaller;

if D is_xd2And D_dn2Sum greater than 1, D_xd2And D_dn2Is unchanged for the smaller of D_xd2And D_dn2The larger of which becomes 1 minus the smaller;

a4, according to D_xd1、D_dn1And D_xd2、D_dn2Calculate D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c]：

Wherein D is_z1Has a value range of [0, 1-D_xd1-D_dn1]；D_z2Has a value range of [0, 1-D_xd2-D_dn2](ii) a The definition of function sign1() and function sign2() are shown as follows:

。

3. the frequency-doubled single-resistor current sampling method of claim 2, wherein D is₁[a]、D₁[b]、D₁[c]Three-phase duty cycle being the first half of the carrier cycle, D₂[a]、D₂[b]、D₂[c]The three-phase duty cycle of the latter half of the carrier period.

4. The frequency-doubling single-resistor current sampling method according to claim 3, wherein in the step b, the current sampling time t is calculated according to the adjusted three-phase duty ratio_s1、t_s2，t_s3And t_s4The process of (2) is as follows:

b1, calculating the current sampling time t of the first half carrier period_s1And t_s2：

Three-phase duty ratio D of the first half carrier period₁[a]、D₁[b]、D₁[c]Sorting according to the size sequence to obtain the maximum value D_max1Middle value D_mid1Minimum value D_min1And recording the maximum value D_max1Middle value D_mid1And a minimum value D_min1The corresponding phase is a phase, b phase or c phase, and Max is ordered₁Representative duty cycleNumber of phase corresponding to maximum value, Mid₁Number, Min, representing phase of duty cycle median₁Representing the serial number of the corresponding phase of the minimum value of the duty ratio; current sampling time t_s1And t_s2Calculated from the following formula:

b2, calculating current sampling time t of the second half carrier wave period_s3And t_s4：

Three-phase duty ratio D of the second half carrier period₂[a]、D₂[b]、D₂[c]Sorting according to the size sequence to obtain the maximum value D_max2Middle value D_mid2Minimum value D_min2And recording the maximum value D_max2Middle value D_mid2And a minimum value D_min2The corresponding phase is a phase, b phase or c phase, and Max is ordered₂Number, Mid, representing the phase corresponding to the maximum value of the duty cycle₂Number, Min, representing phase of duty cycle median₂Representing the serial number of the corresponding phase of the minimum value of the duty ratio; current sampling time t_s3And t_s4Calculated from the following formula:

。

5. the frequency-doubled single-resistor current sampling method according to claim 3 or 4, wherein in the first half of the carrier period, when the time t is less than (1-D)₁[x]) When T/2, the x phase outputs low level, otherwise, high level is output; in the latter half of the carrier period, when the time t is less than (1+ D)₂[x]) When T/2, the x phase outputs high level, otherwise, the x phase outputs low level; d₁[x]Represents D₁[a]、D₁[b]And D₁[c]，D₂[x]Represents D₂[a]、D₂[b]And D₂[c]。

6. The frequency-doubling single-resistor current sampling method according to claim 2, wherein in the step d, reconstructing three-phase currents of a first half period and a second half period of a carrier period respectively according to the current sampling result, and further obtaining a three-phase average current of the carrier period comprises the following steps:

calculating three-phase current I of the first half of the carrier period₁[a]、I₁[b]And I₁[c]：

Calculating three-phase current I of the latter half period of the carrier period₂[a]、I₂[b]And I₂[c]：

Calculating three-phase average currents Ia, Ib and ic of the carrier period:

wherein, I_dc1、I_dc2、I_dc3And I_dc4Are each at t_s1、t_s2、t_s3And t_s4And sampling the obtained bus current at any time.

7. A frequency-doubling single-resistor current sampling device is characterized by comprising:

a memory for storing a program;

a processor for loading the program to perform the frequency multiplying single resistance current sampling method according to any one of claims 1 to 6.

Technical Field

The invention relates to a single-resistor current sampling technology.

Background

The inverter is typically a three-phase output used to control a three-phase ac motor. The frequency converter generally needs three-phase current signals to realize motor control, and simultaneously, the frequency converter and the motor are protected according to the three-phase current signals. There are many ways to obtain three-phase current signals, and obtaining current signals through sampling resistors is a common current sampling way. According to the number of the sampling resistors, the current sampling method can be divided into three-resistor current sampling, two-resistor current sampling and single-resistor current sampling, wherein the hardware cost of the single-resistor current sampling is the lowest. When the requirement on the system cost is high, single resistance current sampling is a good choice.

The single-resistor current sampling is to collect the bus current, and then the three-phase current is obtained in a reconstruction mode. In order to ensure that three-phase current can be accurately obtained, a single-resistor current sampling method has certain requirements on a sampling window and sampling time, and in order to meet the requirements, only one group of current signals are generally collected in one carrier period in the prior art, namely the current sampling frequency is the same as the carrier frequency, which also causes low current signal sampling precision.

Disclosure of Invention

The invention aims to provide a frequency-doubling single-resistor current sampling method, which can sample two groups of current signals in one carrier period and improve the current sampling frequency and the current sampling precision.

The invention provides a frequency multiplication single-resistor current sampling device.

The embodiment of the invention provides a frequency multiplication single-resistor current sampling method, which comprises the following steps:

a. three-phase duty ratio D [ a ] calculated by PWM control algorithm]、D[b]、D[c]Adjusting to obtain the adjusted three-phase duty ratio D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c](ii) a Wherein D is₁[a]、D₁[b]、D₁[c]Three-phase duty cycle, D, being one of the first half or the second half of the carrier cycle₂[a]、D₂[b]、D₂[c]A three-phase duty cycle that is the other of the first half cycle or the second half cycle of the carrier cycle;

b. calculating current sampling time t according to the adjusted three-phase duty ratio_s1、t_s2、t_s3And t_s4；

c. Outputting three-phase voltage according to the adjusted three-phase duty ratio;

d. at the current sampling time t_s1、t_s2、t_s3And t_s4And respectively carrying out current sampling, and respectively reconstructing three-phase currents of the first half period and the second half period of the carrier period according to current sampling results so as to obtain the three-phase average current of the carrier period.

The invention also provides a frequency multiplication single-resistor current sampling device, which comprises: a memory for storing a program; and the processor is used for loading the program to execute the frequency multiplication single-resistor current sampling method.

According to the frequency multiplication single-resistor current sampling method and the frequency multiplication single-resistor current sampling device, two groups of current signals can be sampled in one carrier period, and then three-phase average current of the carrier period can be obtained, so that the current sampling precision of the single-resistor current sampling method is improved.

Drawings

Fig. 1 shows a schematic flow diagram of a frequency-doubling single-resistor current sampling method according to an embodiment of the present invention.

Fig. 2 shows a schematic diagram of four sampling instants according to an embodiment of the invention.

FIG. 3 shows a schematic diagram of a single phase voltage output at a regulated duty cycle according to an embodiment of the present invention.

Detailed Description

Please refer to fig. 1. According to the frequency multiplication single-resistor current sampling method provided by the embodiment of the invention, the bus current is sampled through the sampling resistor arranged on the bus of the three-phase inverter circuit, and the method comprises the following steps:

a. three-phase duty ratio D [ a ] calculated by PWM control algorithm]、D[b]、D[c]Adjusting to obtain the adjusted three-phase duty ratio D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c](ii) a Wherein D is₁[a]、D₁[b]、D₁[c]Is one of the first half period or the second half period of the carrier wave periodThree-phase duty cycle of D₂[a]、D₂[b]、D₂[c]A three-phase duty cycle that is the other of the first half cycle or the second half cycle of the carrier cycle;

b. calculating current sampling time t according to the adjusted three-phase duty ratio_s1、t_s2、t_s3And t_s4；

c. Outputting three-phase voltage according to the adjusted three-phase duty ratio;

d. at the current sampling time t_s1、t_s2、t_s3And t_s4And respectively carrying out current sampling, and respectively reconstructing three-phase currents of the first half period and the second half period of the carrier period according to current sampling results so as to obtain the three-phase average current of the carrier period.

The frequency multiplication single-resistor current sampling method comprises the following steps:

a1, three-phase duty ratio D [ a ] calculated by PWM control algorithm]、D[b]、D[c]Sorting according to the size sequence to obtain the maximum value D_maxMiddle value D_midMinimum value D_minAnd recording the maximum value D_maxMiddle value D_midAnd a minimum value D_minIf the corresponding phase is a phase a, a phase b or a phase c, making Max represent the serial number of the phase corresponding to the maximum value of the duty ratio, Mid represent the serial number of the phase corresponding to the intermediate value of the duty ratio, and Min represent the serial number of the phase corresponding to the minimum value of the duty ratio; when the three-phase duty ratios are equal, firstly, appointing any one-phase duty ratio as a maximum value, then appointing any one-phase duty ratio in the rest two-phase duty ratios as an intermediate value, and appointing the rest one-phase duty ratio as a minimum value; when the two-phase duty ratios are equal, designating any one phase of the equal two-phase duty ratios as a large value and designating the other phase of the equal two-phase duty ratios as a small value;

a2, calculation D_maxAnd D_midDifference D of_xdAnd D_midAnd D_minDifference D of_dn：

Wherein D is_max、D_midAnd D_minAre respectively the three-phase duty ratio D [ a ]]、D[b]、D[c]Maximum, intermediate and minimum values of;

a3, according to D_xdAnd D_dnObtaining a first temporary calculated variable D_xd1A second temporary calculated variable D_dn1A third temporary calculated variable D_xd2And a fourth temporary calculated variable D_dn2：

In the above formula,. DELTA.D_xdAnd Δ D_dnAre respectively D_xdAnd D_dnAdjustment of (D), Δ D_xdAnd Δ D_dnThe value taking mode is as follows: in the following six groups Δ D_xdAnd Δ D_dnSix groups of delta D solved by the calculation formula_xdAnd Δ D_dnIn (1), selecting Δ D_xdAnd Δ D_dnThe set of solutions with the smallest sum is used as the actual Δ D_xdAnd Δ D_dn；

The six formulas are respectively as follows:

wherein D is_Ts＝T_s2/T, wherein T is a carrier period, and Ts is a preset minimum sampling window; the functions fun1() and fun2() are defined as follows:

for D calculated by the above formula_xd1、D_dn1、D_xd2、D_dn2The final D is obtained by limiting according to the following limiting rule_xd1、D_dn1、D_xd2、D_dn2：

If D is_xd1And D_dn1Sum greater than 1, D_xd1And D_dn1Is unchanged for the smaller of D_xd1And D_dn1The larger of which becomes 1 minus the smaller;

if D is_xd2And D_dn2Sum greater than 1, D_xd2And D_dn2Is unchanged for the smaller of D_xd2And D_dn2The larger of which becomes 1 minus the smaller;

a4, according to D_xd1、D_dn1And D_xd2、D_dn2Calculate D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c]：

Wherein D is_z1Has a value range of [0, 1-D_xd1-D_dn1]；D_z2Has a value range of [0, 1-D_xd2-D_dn2](ii) a The definition of function sign1() and function sign2() are shown as follows:

。

the working process of the frequency-doubling single-resistor current sampling method of the present invention is further described with reference to a specific embodiment.

According to the embodiment, the three-phase duty ratio calculated by the PWM control algorithm is firstly adjusted, then the time of four times of current sampling is calculated, and finally three-phase currents of the first half carrier period and the second half carrier period are respectively reconstructed according to the bus current obtained by sampling, so that the three-phase average current of the carrier period is obtained. The frequency multiplication single-resistance current sampling method of the embodiment is applied to a frequency converter, the carrier period of the frequency converter is T, and the minimum sampling window is T_sA PWM control algorithm for controlling the operation of the motor and a sampling algorithm are performed once per carrier period. In this embodiment, the duty ratios of the a-phase, the b-phase and the c-phase are all zero. The specific steps of this example are as follows:

step a, calculating the three-phase duty ratio D [ a ] of the PWM control algorithm]、D[b]、D[c]Adjusting to obtain the adjusted three-phase duty ratio D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c](ii) a Step a further comprises:

a1, calculating the three-phase duty ratio D [ a ] by PWM control algorithm]、D[b]、D[c]Sorting according to the size sequence to obtain the maximum value D_maxMiddle value D_midMost preferablySmall value of D_minAnd recording whether the phase corresponding to the maximum value, the intermediate value and the minimum value is a phase, b phase or c phase. Max represents the serial number of the phase corresponding to the maximum value of the duty ratio, Mid represents the serial number of the phase corresponding to the intermediate value of the duty ratio, Min represents the serial number of the phase corresponding to the minimum value of the duty ratio, the values of Max, Mid and Min are all a, b or c, and a, b and c are the serial numbers of the phase a, the phase b and the phase c respectively. In this embodiment, before the adjustment, since the duty ratios of the a-phase, the b-phase and the c-phase are all zero, D is_max＝0、D_mid＝0、D_minMax ═ a, Mid ═ b, and Min ═ c. Note that Max denotes that the a-phase duty ratio is the maximum before adjustment, and Max stores the number of the phase corresponding to the maximum duty ratio before adjustment, but the a-phase duty ratio after adjustment (i.e., D to be described later)₁[a]And D₂[a]) May no longer be the maximum. Mid and Min are similar to the meaning of b and c.

a2, calculation D_maxAnd D_midDifference D of_xdAnd D_midAnd D_minDifference D of_dn，D_xdAnd D_dnCalculated according to the following formula:

a3, according to D_xdAnd D_dnObtaining a first temporary calculated variable D_xd1A second temporary calculated variable D_dn1A third temporary calculated variable D_xd2Fourth temporary calculated variable D_dn2；D_xd1、D_dn1And D_xd2、D_dn2The following formula was used for calculation:

in the above formula,. DELTA.D_xdAnd Δ D_dnAre respectively D_xdAnd D_dnThe amount of adjustment of (a). Delta D_xdAnd Δ D_dnThere are six possibilities for taking values, which are shown below:

wherein D is_Ts＝T_s2/T, wherein T is a carrier period, and Ts is a preset minimum sampling window; the functions fun1() and fun2() are defined as follows:

six groups of delta D can be solved according to the six groups of formulas_xdAnd Δ D_dnSelecting Δ D_xdAnd Δ D_dnThe set of solutions with the smallest sum is used as the actual Δ D_xdAnd Δ D_dnI.e. the last group, to obtain D_xd1、D_dn1And D_xd2、D_dn2。

Calculate D_xd1、D_dn1And D_xd2、D_dn2Then, the pair D is also required_xd1、D_dn1And D_xd2、D_dn2Limiting according to the following limiting rule to obtain the final D_xd1、D_dn1、D_xd2、D_dn2：

If D is_xd1And D_dn1The sum is greater than 1, then D_xd1And D_dn1Is unchanged for the smaller of D_xd1And D_dn1The larger of which becomes 1 minus the smaller (1-smaller);

if D is_xd2And D_dn2The sum is greater than 1, then D_xd2And D_dn2Is unchanged for the smaller of D_xd2And D_dn2The larger of which becomes 1 minus the smaller (the larger is 1-smaller).

a4, according to D_xd1、D_dn1And D_xd2、D_dn2Calculate D₁[a]、D₁[b]、D₁[c]And D₂[a]、D₂[b]、D₂[c]；D₁[a]、D₁[b]、D₁[c]Obtained by the following formula:

in the above formula, D_z1Has a value range of [0, 1-D_xd1-D_dn1]I.e. D_z1Is 0, 1-D_xd1-D_dn1Or 0 and 1-D_xd1-D_dn1Any value in between.

D₂[a]、D₂[b]、D₂[c]Obtained by the following formula:

in the above formula, D_z2Has a value range of [0, 1-D_xd2-D_dn2]I.e. D_z2Is 0, 1-D_xd2-D_dn2Or 0 and 1-D_xd2-D_dn2Any value in between.

Step b, calculating current sampling time t according to the adjusted three-phase duty ratio_s1、t_s2，t_s3And t_s4：

Firstly, calculating the current sampling time t of the first half carrier period_s1And t_s2：

Three-phase duty ratio D of the first half carrier period₁[a]、D₁[b]、D₁[c]Sorting according to the size sequence to obtain the maximum value D_max1Middle value D_mid1Minimum value D_min1And recording the maximum value D_max1Middle value D_mid1And a minimum value D_min1The corresponding phase is a phase, b phase or c phase, and Max is ordered₁Number, Mid, representing the phase corresponding to the maximum value of the duty cycle₁Number, Min, representing phase of duty cycle median₁Representing the serial number of the corresponding phase of the minimum value of the duty ratio; max (maximum of ten)₁、Mid₁And Min₁The value is a, b or c, and the a, b and c are respectively the serial numbers of the a phase, the b phase and the c phase. Can obtain D_max1＝D₁[a]、D_mid1＝D₁[b]、D_min1＝D₁[c]、Max₁＝a、Mid₁＝b、Min₁＝c。

t_s1And t_s2Can be calculated from the following formula.

Then calculating the current sampling time t of the second half carrier period_s3And t_s4：

Three-phase duty ratio D of the second half carrier period₂[a]、D₂[b]、D₂[c]Sorting according to the size sequence to obtain the maximum value D_max2Middle value D_mid2Minimum value D_min2And is combined withRecord the maximum value D_max2Middle value D_mid2And a minimum value D_min2The corresponding phase is a phase, b phase or c phase, and Max is ordered₂Number, Mid, representing the phase corresponding to the maximum value of the duty cycle₂Number, Min, representing phase of duty cycle median₂Number, Max, representing phase corresponding to minimum value of duty ratio₂、Mid₂And Min₂The value is a, b or c, and the a, b and c are respectively the serial numbers of the a phase, the b phase and the c phase. Can obtain D_max2＝D₂[c]、D_mid2＝D₂[b]、D_min2＝D₂[a]、Max₂＝c、Mid₂＝b、Min₂A. Current sampling time t_s3And t_s4Calculated from the following formula.

Fig. 2 shows a schematic diagram of four sampling instants according to a first embodiment of the present invention, where 0 in fig. 2 represents the start instant of a carrier period.

And c, outputting the three-phase voltage according to the adjusted three-phase duty ratio. According to D in the first half of the carrier period₁[a]、D₁[b]、D₁[c]Outputting three-phase voltage according to D in the latter half period of the carrier wave period₂[a]、D₂[b]、D₂[c]And outputting three-phase voltage.

For simplicity of description, x represents a, b, c, by D₁[x]Represents D₁[a]、D₁[b]、D₁[c]By D₂[x]Represents D₂[a]、D₂[b]、D₂[c]. In the first half of the carrier period, when time t is less than (1-D)₁[x]) When T/2, the x phase outputs low level, otherwise, high level is output; in the latter half of the carrier period, when the time t is less than (1+ D)₂[x]) And T/2, outputting high level by the x phase, and otherwise, outputting low level. Fig. 3 is a schematic diagram illustrating a single-phase voltage output according to an adjusted duty ratio according to an embodiment of the present invention. 0 in FIG. 3 represents the start of the carrier cycle, in this embodiment, the sampling algorithm cycle andthe carrier period is the same, and 0 is also the starting time of the sampling algorithm period. The time t mentioned above is the time within the current sampling algorithm period.

Step d, current sampling time t in carrier period_s1、t_s2、t_s3And t_s4Respectively sampling to obtain bus current I_dc1、I_dc2、I_dc1And I_dc2And respectively reconstructing three-phase currents of the first half period and the second half period of the carrier period according to the bus current obtained by sampling, and further obtaining the three-phase average current of the carrier period.

The three-phase currents in the first half of the wave period are respectively I₁[a]、I₁[b]And I₁[c]，I₁[a]、I₁[b]And I₁[c]Obtained by the following formula:

the three-phase currents in the latter half of the wave period are respectively I₂[a]、I₂[b]And I₂[c]，I₂[a]、I₂[b]And I₂[c]Obtained by the following formula.

The three-phase average currents Ia, Ib and ic of the carrier period are obtained by the following formula.

According to the embodiment of the invention, firstly, the three-phase duty ratio calculated by the PWM control algorithm is adjusted, then the time of four times of current sampling is calculated, and finally, three-phase currents of front and back half carrier periods are respectively reconstructed according to the bus current obtained by sampling, so that the three-phase average current of the carrier period is obtained. In the embodiment of the invention, the duty ratio of the first half period and the duty ratio of the second half period of each carrier wave period can be exchanged, and after the exchange, the sampling time and the calculation formula of current reconstruction are correspondingly modified to realize single-resistor current sampling, and a specific formula is not given here.

In the embodiment of the present invention, when the voltage is output, the polarity of the level may be changed. If the high level is changed into the low level, and the low level is changed into the high level, the same voltage can be ensured to be output only by adjusting the original duty ratio (the value of the original duty ratio is changed into 1 and the value is subtracted), at the moment, the single-resistance current sampling can be realized by correspondingly modifying the sampling time and the calculation formula of current reconstruction, and a specific formula is not given here.

Still another embodiment of the present invention further provides a frequency-doubled single-resistor current sampling apparatus, which includes a memory and a processor. The memory is used for storing programs; the processor is used for loading the program to execute the frequency multiplication single-resistance current sampling method.

According to the frequency multiplication single-resistance current sampling method and the frequency multiplication single-resistance current sampling device, two groups of current signals can be sampled in one carrier period, and then three-phase average current of the carrier period can be obtained, so that the current sampling precision of the single-resistance current sampling method is improved, and further control over a three-phase motor and protection over a motor driving device (such as a frequency converter and the like) and the motor are achieved.