A current sampling system and method

Abstract

The application provides a current sampling system and method, the current sampling system comprising a motor three-phase circuit and a processing module; a first phase comprising a first IGBT chip and a second IGBT chip; a second phase comprising a third IGBT chip and a fourth IGBT chip; a third phase comprising a fifth IGBT chip and a sixth IGBT chip; a sampling unit of the processing module sampling at a wave trough moment and a wave peak moment of a switching cycle to form a first current sampling value and a second current sampling value; a calculation unit extracting effective current sampling data in the first current sampling value and the second current sampling value at the wave trough moment of the switching cycle, and correcting current sampling zero value data in the first current sampling value and the second current sampling value into estimated current sampling data. After the above technical scheme is adopted, the sampling current of the on-chip current sensor in the new generation of IGBT chips can be directly used for motor control, the current sensor in the original circuit is saved, the circuit structure is simplified, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of motor control, and more particularly to a current sampling system and method. Background Technology

[0002] With the rapid development of new energy vehicles, the design of their core components—the motor and its controller—has become a key design area for various electric control manufacturers. Current motor controllers and inverters / frequency converters for other applications typically use Hall effect current sensors to sample the three-phase current. However, the new generation of IGBT chips incorporates on-chip current sensors, and using on-chip current sensors for sampling is difficult to implement using traditional methods.

[0003] Traditional methods can only capture the forward current of the switching transistor, not the current in the anti-parallel diode. Furthermore, within each half-cycle of a sinusoidal current, only one IGBT chip in the bridge arm experiences forward current, making it unsuitable for direct control and unable to obtain the full-cycle current.

[0004] Therefore, a novel current sampling system and method are needed, which can utilize a control strategy that dynamically switches the sampling chip when the current crosses zero, in order to achieve full-cycle sampling of the bridge arm current. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a current sampling system and method that can directly use the sampled current of the on-chip current sensor in the IGBT chip for motor control, thus simplifying the circuit structure.

[0006] This invention discloses a current sampling system, which includes a three-phase motor circuit and a processing module;

[0007] A three-phase circuit for a motor includes the first phase, the second phase, and the third phase.

[0008] The first phase includes a first IGBT chip and a second IGBT chip connected in series. The first IGBT chip includes a first switch and a first diode connected in parallel with opposite current flows. The second IGBT chip includes a second switch and a second diode connected in parallel with opposite current flows.

[0009] The second phase includes a third IGBT chip and a fourth IGBT chip connected in series. The third IGBT chip includes a third switch and a third diode connected in parallel with opposite current flows, and the fourth IGBT chip includes a fourth switch and a fourth diode connected in parallel with opposite current flows.

[0010] The third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series. The fifth IGBT chip includes a fifth switch and a fifth diode connected in parallel with opposite current flows. The sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flows.

[0011] The processing module includes a sampling unit and a calculation unit. The sampling unit samples the current flowing through the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch at the trough and peak times of a switching cycle, and forms the first current sampling value and the second current sampling value, respectively.

[0012] The calculation unit extracts the effective current sampling data within the first current sampling value and the second current sampling value at the trough of the switching cycle, and corrects the zero current sampling data within the first current sampling value and the second current sampling value into estimated current sampling data based on the sum of the three-phase currents being zero or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first phase current, the second phase current and the third phase current respectively.

[0013] Preferably, at the trough moment, the first current sampling value includes: the first current of the first switch, the second current of the second switch, the third current of the third switch, the fourth current of the fourth switch, the fifth current of the fifth switch, and the sixth current of the sixth switch.

[0014] At the peak moment, the second current sampling value includes: the seventh current of the first switch, the eighth current of the second switch, the ninth current of the third switch, the tenth current of the fourth switch, the eleventh current of the fifth switch, and the twelfth current of the sixth switch.

[0015] The switching cycle is different from the cycle of the motor's sinusoidal current.

[0016] Preferably, at the trough moment, the value of the triangular carrier wave used to control the opening and closing of any one or any two phases of the first, second, and third phases in the three-phase circuit of the motor is less than the value of the sinusoidal current of the motor at the same moment, so that the first, third, and fifth switches are turned on, and the second, fourth, and sixth switches are turned off.

[0017] At the peak of the wave, the value of the triangular carrier wave used to control the opening and closing of any one or any one of the first, second, and third phases in the three-phase circuit of the motor is greater than the value of the sinusoidal current of the motor at the same time, so that the first, third, and fifth switches are turned off, and the second, fourth, and sixth switches are turned on.

[0018] When the first phase current, the second phase current, or the third phase current is positive, current flows through the first switch and the second diode, or the third switch and the fourth diode, or the fifth switch and the sixth diode, making the first current, the third current, or the fifth current valid current sampling data, and the second current, the fourth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current zero current sampling value.

[0019] When the first phase current, the second phase current, or the third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode, making the eighth current, the tenth current, or the twelfth current valid current sampling data, while the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the ninth current, and the eleventh current are zero current sampling values.

[0020] Preferably, the calculation unit determines the positive or negative status of the first current, the third current, and the fifth current at the trough moment;

[0021] When two of the first, third, and fifth currents are positive and one is negative, the current sampled to estimate the current is corrected based on the sum of the three-phase currents being zero and the current sampled to be negative.

[0022] When two of the first, third, and fifth currents are negative and one is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0023] The calculation unit determines the sign of the eighth, tenth, and twelfth currents at the peak of the wave.

[0024] When two of the eighth, tenth, and twelfth currents are positive and one is negative, the current sampled by the negative one is corrected based on the sum of the three-phase currents being zero;

[0025] When two of the eighth, tenth, and twelfth currents are negative and one is positive, the change in motor angle is calculated based on the ratio of half the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0026] Preferably, the calculation unit further extracts and compares the first current sample value and the second current sample value at the peak time;

[0027] When the data of the first current sample value and the second current sample value are: the seventh current and the eighth current, or the ninth current and the tenth current, or the eleventh current and the twelfth current, which are both zero current sampling values, the calculation unit keeps the first current sample value and the second current sample value extracted at the trough time of the previous switching cycle unchanged.

[0028] When the data of the first current sampling value and the second current sampling value are: the first current as valid current sampling data and the second current as zero current sampling value, the third current as valid current sampling data and the fourth current as zero current sampling value, the fifth current as valid current sampling data and the sixth current as zero current sampling value, the calculation unit records the first current, the third current and the fifth current as the first phase current, the second phase current and the third phase current.

[0029] When the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero current sampling value, the tenth current as valid current sampling data and the ninth current as zero current sampling value, the twelfth current as valid current sampling data and the eleventh current as zero current sampling value, the calculation unit records the eighth current, the tenth current, and the twelfth current as the first phase current, the second phase current, and the third phase current.

[0030] This invention also discloses a current sampling method, comprising the following steps:

[0031] A three-phase motor circuit and processing module are configured with interconnected components. The three-phase motor circuit includes a first phase, a second phase, and a third phase. The first phase includes a first IGBT chip and a second IGBT chip connected in series. The first IGBT chip includes a first switch and a first diode connected in parallel with opposite current flows. The second IGBT chip includes a second switch and a second diode connected in parallel with opposite current flows. The second phase includes a third IGBT chip and a fourth IGBT chip connected in series. The third IGBT chip includes a third switch and a third diode connected in parallel with opposite current flows. The fourth IGBT chip includes a fourth switch and a fourth diode connected in parallel with opposite current flows. The third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series. The fifth IGBT chip includes a fifth switch and a fifth diode connected in parallel with opposite current flows. The sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flows. The processing module includes a sampling unit and a calculation unit.

[0032] The sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, respectively forming the first current sampling value and the second current sampling value.

[0033] The calculation unit extracts the effective current sampling data within the first current sampling value and the second current sampling value at the trough of the switching cycle, and corrects the zero current sampling data within the first current sampling value and the second current sampling value into estimated current sampling data based on the sum of the three-phase currents being zero or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first phase current, the second phase current and the third phase current respectively.

[0034] Preferably, the step of sampling the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, and forming the first current sampling value and the second current sampling value respectively, includes:

[0035] At the trough moment, the first current sampling value includes: the first current of the first switch, the second current of the second switch, the third current of the third switch, the fourth current of the fourth switch, the fifth current of the fifth switch, and the sixth current of the sixth switch.

[0036] At the peak moment, the second current sampling value includes: the seventh current of the first switch, the eighth current of the second switch, the ninth current of the third switch, the tenth current of the fourth switch, the eleventh current of the fifth switch, and the twelfth current of the sixth switch.

[0037] The switching cycle is different from the cycle of the motor's sinusoidal current.

[0038] Preferably, the step of sampling the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, and forming the first current sampling value and the second current sampling value respectively, includes:

[0039] At the trough moment, the value of the triangular carrier wave used to control the opening and closing of any one or any of the first, second, and third phases in the three-phase circuit of the motor is less than the value of the sinusoidal current of the motor at the same moment, so that the first, third, and fifth switches are turned on, and the second, fourth, and sixth switches are turned off.

[0040] At the peak of the wave, the value of the triangular carrier wave used to control the opening and closing of any one or any one of the first, second, and third phases in the three-phase circuit of the motor is greater than the value of the sinusoidal current of the motor at the same time, so that the first, third, and fifth switches are turned off, and the second, fourth, and sixth switches are turned on.

[0041] When the first phase current, the second phase current, or the third phase current is positive, current flows through the first switch and the second diode, or the third switch and the fourth diode, or the fifth switch and the sixth diode, making the first current, the third current, or the fifth current valid current sampling data, and the second current, the fourth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current zero current sampling value.

[0042] When the first phase current, the second phase current, or the third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode, making the eighth current, the tenth current, or the twelfth current valid current sampling data, while the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the ninth current, and the eleventh current are zero current sampling values.

[0043] Preferably, the calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current, to obtain the first-phase current, second-phase current, and third-phase current respectively. The steps include:

[0044] The calculation unit determines the sign of the first, third, and fifth currents at the trough time;

[0045] When two of the first, third, and fifth currents are positive and one is negative, the current sampled to estimate the current is corrected based on the sum of the three-phase currents being zero and the current sampled to be negative.

[0046] When two of the first, third, and fifth currents are negative and one is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0047] The calculation unit determines the sign of the eighth, tenth, and twelfth currents at the peak of the wave.

[0048] When two of the eighth, tenth, and twelfth currents are positive and one is negative, the current sampled by the negative one is corrected based on the sum of the three-phase currents being zero;

[0049] When two of the eighth, tenth, and twelfth currents are negative and one is positive, the change in motor angle is calculated based on the ratio of half the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0050] Preferably, the calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first-phase current, second-phase current, and third-phase current respectively. The step further includes:

[0051] The computing unit also extracts and compares the first current sample value and the second current sample value at the peak of the wave.

[0052] When the data of the first current sample value and the second current sample value are: the seventh current and the eighth current, or the ninth current and the tenth current, or the eleventh current and the twelfth current, which are both zero current sampling values, the calculation unit keeps the first current sample value and the second current sample value extracted at the trough time of the previous switching cycle unchanged.

[0053] When the data of the first current sampling value and the second current sampling value are: the first current as valid current sampling data and the second current as zero current sampling value, the third current as valid current sampling data and the fourth current as zero current sampling value, the fifth current as valid current sampling data and the sixth current as zero current sampling value, the calculation unit records the first current, the third current and the fifth current as the first phase current, the second phase current and the third phase current.

[0054] When the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero current sampling value, the tenth current as valid current sampling data and the ninth current as zero current sampling value, the twelfth current as valid current sampling data and the eleventh current as zero current sampling value, the calculation unit records the eighth current, the tenth current, and the twelfth current as the first phase current, the second phase current, and the third phase current.

[0055] Compared with existing technologies, the above technical solution has the following advantages:

[0056] It can solve the problem that the on-chip current sensor of IGBT cannot sample and obtain the complete current, and it is applicable regardless of the sampling and calculation frequency.

[0057] It can achieve closed-loop control of various motors without the need for an additional current sampling device, saving the cost of the converter. Attached Figure Description

[0058] Figure 1 To conform to the three-phase circuit topology of the motor in a preferred embodiment of the present invention;

[0059] Figure 2 This is a schematic diagram of the first phase conduction status in a preferred embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram illustrating the correspondence between the triangular carrier wave and the sinusoidal current of the motor used to control the on / off of any one or any of the first, second, and third phases in the three-phase circuit of the motor, and the on / off of the first, third, fifth, second, fourth, and sixth switching transistors, in accordance with a preferred embodiment of the present invention. Detailed Implementation

[0061] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0062] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0063] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0064] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0065] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0066] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0067] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0068] For example Figure 1 The present invention provides a current sampling system for detecting the current of each phase of a three-phase motor circuit, which includes a first phase, a second phase, and a third phase.

[0069] - The first phase includes a first IGBT chip and a second IGBT chip connected in series. The first IGBT chip includes a first switch and a first diode connected in parallel with opposite current flows. The second IGBT chip includes a second switch and a second diode connected in parallel with opposite current flows. That is, when the first switch is turned on, the first diode is turned off, and vice versa.

[0070] - The second phase includes a third IGBT chip and a fourth IGBT chip connected in series, wherein the third IGBT chip includes a third switch and a third diode connected in parallel with opposite current flows, and the fourth IGBT chip includes a fourth switch and a fourth diode connected in parallel with opposite current flows.

[0071] - The third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series. The fifth IGBT chip includes a fifth switch and a fifth diode connected in parallel with opposite current flows, and the sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flows.

[0072] It is understandable that the first IGBT chip, the second IGBT chip, the third IGBT chip, the fourth IGBT chip, the fifth IGBT chip, and the sixth IGBT chip described above can also be integrated chips formed by multiple IGBTs connected in parallel.

[0073] See Figure 2 Because the direction of current flow may change in the three-phase circuit of a motor, when the current is positive (flowing towards the motor windings), the first switch is turned on, the second switch is turned off, the first diode is turned off, and the second diode is turned on. Conversely, when the current is negative, the first switch is turned off, the second switch is turned on, the first diode is turned on, and the second diode is turned off. The same applies to other combinations of switches and diodes.

[0074] The current sampling system also includes a processing module, which specifically comprises a sampling unit and a calculation unit. The sampling unit is connected across the first, second, third, fourth, fifth, and sixth switching transistors to detect the current flowing through the switching transistors at a given moment. It is understood that each group of switching transistors is connected in parallel with a diode, and the current flowing through the diode is typically not sampled. Therefore, after processing the sampled current of the switching transistors, the sampling unit calculates the current of each phase of the motor controller. Thus, the sampling unit is also electrically connected to a calculation unit, such as a CPU, to process the data collected by the sampling unit. In one embodiment, the sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, forming a first current sampling value and a second current sampling value, respectively. It is understood that the switching cycle is the period during which each switching transistor is controlled to turn on and off. Since the control carrier wave is a triangular wave, the sampling time of the sampling unit is determined at the trough and peak times of each switching cycle, that is, sampling is performed twice per switching cycle. Similarly, it can be understood that the first and second current sampling values ​​contain the current values ​​of each switch at the trough and peak times. The current values ​​of switches on the same phase (such as the first and second switches) can be stored or transferred in matrix form.

[0075] In the above embodiments, the sampling unit may be integrated into the IGBT chip or independent of the IGBT chip.

[0076] The calculation unit is triggered once per switching cycle, extracting effective current sampling data from the first and second current sampling values ​​at the trough of the switching cycle. Effective current sampling data is defined as current sampling values ​​that are not zero. It can be understood that effective current sampling data is sampled only when the switch is turned on and current flows. In other words, within one cycle of the motor's sinusoidal current, the current in one phase is positive for half the cycle and negative for the other half (switching at zero point). This means that the current can only be sampled for half a cycle within one cycle of the motor's sinusoidal current. Furthermore, the switch must be turned on within this half-cycle, resulting in only 1 / 4 of the sampled current data being non-zero; these are the effective current sampling data. This further delays the calculation of current by the calculation unit (it must wait for the effective current sampling data to appear before calculation can begin), with a delay period of approximately half a switching cycle. Therefore, for those zero-value current samples, the zero-value current samples in the first and second current samples will be corrected into estimated current samples based on the fact that the sum of the three-phase currents is zero (the nature of the motor's three-phase currents) or the relationship between the amplitude and angle of the motor's sinusoidal current (predicting and compensating for the theoretical change in current value caused by the known amplitude of the motor's sinusoidal current, the ratio of the switching period to the period of the motor's sinusoidal current before the half-cycle delay). This eliminates the need to wait for the first phase current, second phase current, and third phase current to be obtained separately. After adopting the above technical solution, there will be no delay in calculation and sampling time, and motor control can be implemented in real time.

[0077] In a preferred embodiment, the switching cycle is different from the cycle of the motor's sinusoidal current. The sampling unit is configured to sample the current of all switching transistors at the trough of the switching cycle, such that the first current sample value includes: the first current of the first switching transistor, the second current of the second switching transistor, the third current of the third switching transistor, the fourth current of the fourth switching transistor, the fifth current of the fifth switching transistor, and the sixth current of the sixth switching transistor. At the peak of the switching cycle, the current of all switching transistors is sampled, such that the second current sample value includes: the seventh current of the first switching transistor, the eighth current of the second switching transistor, the ninth current of the third switching transistor, the tenth current of the fourth switching transistor, the eleventh current of the fifth switching transistor, and the twelfth current of the sixth switching transistor. That is, sampling is performed twice within each switching cycle, and the result is calculated once by the calculation unit.

[0078] For further details, please refer to [link / reference]. Figure 3Because the switching period differs from the period of the motor's sinusoidal current, they intersect at a point where the switching transistors are turned on and off (a high level indicates all upper transistors are on, and a low level indicates all lower transistors are on). Specifically, when the magnitude of the triangular carrier wave that controls the on / off state of any one or any of the first, second, and third phases in the three-phase control circuit of the motor is less than the magnitude of the motor's sinusoidal current at the same moment, the first, third, and fifth switching transistors are turned on, while the second, fourth, and sixth switching transistors are turned off. Since the sampling time is only located at the trough and peak of the triangular carrier wave, the trough moment is precisely when the first, third, and fifth switching transistors are turned on, and the second, fourth, and sixth switching transistors are turned off. Conversely, at the peak of the wave, the value of the triangular carrier wave used to control the opening and closing of any one or any of the first, second, and third phases in the three-phase circuit of the motor is greater than the value of the sinusoidal current of the motor at the same moment, causing the first, third, and fifth switches to turn off, and the second, fourth, and sixth switches to turn on.

[0079] Simultaneously, considering the positive and negative values ​​of the motor's sinusoidal current, when the first, second, or third phase current is positive, current flows through the first switch and second diode, or the third switch and fourth diode, or the fifth switch and sixth diode. Combined with the aforementioned trough moment, only the first, third, and fifth switches are turned on. This ensures that when the motor's sinusoidal current is positive and sampling occurs at a trough moment, only the first, third, or fifth current has valid current sampling data, while the second, fourth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth currents have zero sampling values. Conversely, when the first, second, or third phase current is positive, current flows through the second, third, or fifth diode. When the current is positive, coinciding with the peak time mentioned above, only the second, fourth, and sixth switches are turned on, and the data sampled at the peak time are all zero. On the other hand, when the first, second, or third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode. Coinciding with the peak time mentioned above, only the second, fourth, and sixth switches are turned on, making the eighth, tenth, or twelfth currents valid current sampling data, while the first, second, third, fourth, fifth, sixth, seventh, ninth, and eleventh currents have zero current sampling values. Conversely, when the first, second, or third phase current is negative, coinciding with the trough time mentioned above, only the first, third, and fifth switches are turned on, and the data sampled at the trough time are all zero.

[0080] Based on this, in a preferred embodiment, the calculation unit determines the positive and negative status of the first current, the third current, and the fifth current at the trough time. When two of the first current, the third current, and the fifth current are positive and one is negative, it indicates that within the motor current, two phases are positive and one phase is negative. Moreover, the sampled value of this negative data in the first half of the switching cycle is not equal to the current at both ends of the switching tube at the current moment. Therefore, the current sampled data of the estimated current is corrected based on the sum of the three-phase currents being zero and the current of one being negative. When two of the first, third, and fifth currents are negative and one is positive, it indicates that within the motor current, two phases are negative and one phase is positive. The change in motor angle is calculated based on the ratio of half the switching cycle to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current (i.e., under such a change in motor angle, the change in the motor sinusoidal current is estimated by pushing back the motor angle change, and the approximate value of the motor sinusoidal current half a switching cycle ago). The current correction is added to this current as estimated current sampling data. The other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0081] On the other hand, the calculation unit determines the positive and negative status of the eighth, tenth, and twelfth currents at the peak of the wave. When two of the eighth, tenth, and twelfth currents are positive and one is negative, the negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero. When two of the eighth, tenth, and twelfth currents are negative and one is positive, the motor angle change is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction amount is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current. The current correction amount is compensated into the current as the estimated current sampling data. The other negative current is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

[0082] In another preferred embodiment, the calculation frequency of the calculation unit can be increased, so that the calculation unit also extracts and compares the first current sampling value and the second current sampling value at the peak moment. As mentioned above, the possible data results of the first current sampling value and the second current sampling value are: both are 0, only the upper half of the switching transistor has effective current sampling data, and only the lower half of the switching transistor has effective current sampling data. Therefore, when the data of the first current sampling value and the second current sampling value are: the seventh current and the eighth current, or the ninth current and the tenth current, or the eleventh current and the twelfth current, both are zero current sampling values, the calculation unit keeps the first current sampling value and the second current sampling value extracted at the trough moment of the previous switching cycle unchanged, that is, it still uses the previous calculation result for control; when the data of the first current sampling value and the second current sampling value are: the first current with effective current sampling data and the second current with zero current sampling value, the third current with effective current sampling data and the fourth current with zero current sampling value, and the first current with effective current sampling data and the second current with zero current sampling value, the calculation unit keeps the first current sampling value and the second current with zero current sampling value, and the second current with zero current sampling value, both are zero current sampling values. When the fifth current and the sixth current are at zero sampling values, the calculation unit records the first current, the third current, and the fifth current as the first phase current, the second phase current, and the third phase current; when the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero sampling value, the tenth current as valid current sampling data and the ninth current as zero sampling value, the twelfth current as valid current sampling data and the eleventh current as zero sampling value, the calculation unit records the eighth current, the tenth current, and the twelfth current as the first phase current, the second phase current, and the third phase current.

[0083] In the above embodiments, the peak and trough times can also be the times when the current is greater than zero or less than zero.

[0084] This invention also discloses a current sampling method, comprising the following steps: configuring a three-phase motor circuit and a processing module electrically connected to each other, wherein the three-phase motor circuit includes a first phase, a second phase, and a third phase; the first phase includes a first IGBT chip and a second IGBT chip connected in series, wherein the first IGBT chip includes a first switching transistor and a first diode connected in parallel with opposite current flows, and the second IGBT chip includes a second switching transistor and a second diode connected in parallel with opposite current flows; the second phase includes a third IGBT chip and a fourth IGBT chip connected in series, wherein the third IGBT chip includes a third switching transistor and a third diode connected in parallel with opposite current flows, and the fourth IGBT chip includes a fourth switching transistor and a fourth diode connected in parallel with opposite current flows; the third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series, wherein the fifth IGBT chip includes a first switching transistor and a second diode connected in parallel with opposite current flows. The fifth IGBT chip includes a fifth switch and a fifth diode with opposite current flow directions. The sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flow directions. The processing module includes a sampling unit and a calculation unit. The sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switches at the trough and peak times of a switching cycle, forming a first current sampling value and a second current sampling value, respectively. The calculation unit extracts the effective current sampling data within the first and second current sampling values ​​at the trough times of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first phase current, second phase current, and third phase current, respectively.

[0085] Preferably or optionally, the sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle to form a first current sampling value and a second current sampling value, respectively. The steps include: at the trough time, the first current sampling value includes: the first current of the first switching transistor, the second current of the second switching transistor, the third current of the third switching transistor, the fourth current of the fourth switching transistor, the fifth current of the fifth switching transistor, and the sixth current of the sixth switching transistor; at the peak time, the second current sampling value includes: the seventh current of the first switching transistor, the eighth current of the second switching transistor, the ninth current of the third switching transistor, the tenth current of the fourth switching transistor, the eleventh current of the fifth switching transistor, and the twelfth current of the sixth switching transistor; the switching cycle is different from the cycle of the sinusoidal current of the motor.

[0086] Preferably or optionally, the sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switches at the trough and peak times of a switching cycle to form the first current sampling value and the second current sampling value, respectively. This step includes: at the trough time, the value of the triangular carrier wave used to control the on / off state of any one or any of the first, second, and third phases in the three-phase motor circuit is less than the value of the motor's sinusoidal current at the same time, causing the first, third, and fifth switches to be turned on, and the second, fourth, and sixth switches to be turned off; at the peak time, the value of the triangular carrier wave used to control the on / off state of any one or any of the first, second, and third phases in the three-phase motor circuit is greater than the value of the motor's sinusoidal current at the same time, causing the first, third, and fifth switches to be turned off, and the second, fourth, and sixth switches to be turned off. When the sixth switch is turned on, and the first, second, or third phase current is positive, current flows through the first switch and the second diode, or the third switch and the fourth diode, or the fifth switch and the sixth diode, making the first, third, or fifth current valid current sampling data, and the second, fourth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth currents zero current sampling values; when the first, second, or third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode, making the eighth, tenth, or twelfth current valid current sampling data, and the first, second, third, fourth, fifth, sixth, seventh, ninth, and eleventh currents zero current sampling values.

[0087] Preferably or optionally, the calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current, to obtain the first-phase current, second-phase current, and third-phase current respectively. This step includes: the calculation unit determining the positive and negative states of the first, third, and fifth currents at the trough; when two of the first, third, and fifth currents are positive and one is negative, correcting the negative current to estimated current sampling data based on the sum of the three-phase currents being zero; when two of the first, third, and fifth currents are negative and one is positive, calculating the motor angle change based on the ratio of ½ of the switching cycle to the period of the motor sinusoidal current, and based on the sampling time of any of the two negative currents. The calculation unit calculates the current correction amount based on the amplitude of the motor sinusoidal current, and compensates for the current by adding the current correction amount to the current as estimated current sampling data. It also corrects the other current among the two negative currents based on the sum of the three-phase currents being zero, and adds it to the estimated current sampling data. At the peak of the wave, the calculation unit determines the sign of the eighth, tenth, and twelfth currents. When two of the eighth, tenth, and twelfth currents are positive and one is negative, the current among the negative currents is corrected based on the sum of the three-phase currents being zero, and adds it to the estimated current sampling data. When two of the eighth, tenth, and twelfth currents are negative and one is positive, the motor angle change is calculated based on the ratio of half the switching period to the period of the motor sinusoidal current. The current correction amount is calculated based on the sampling time of any of the two negative currents and the amplitude of the motor sinusoidal current, and is compensated for by adding the current correction amount to the current as estimated current sampling data. It also corrects the other current among the two negative currents based on the sum of the three-phase currents being zero, and adds it to the estimated current sampling data.

[0088] Preferably or optionally, the calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first-phase current, second-phase current, and third-phase current respectively. The step further includes: the calculation unit also extracts and compares the first and second current sampling values ​​at the peak; when the data of the first and second current sampling values ​​are: the seventh and eighth currents, or the ninth and tenth currents, or the eleventh and twelfth currents, both showing zero current sampling values, the calculation unit keeps the first and second current sampling values ​​extracted at the previous trough of the switching cycle unchanged; when... When the data of the first current sampling value and the second current sampling value are: the first current as valid current sampling data and the second current as zero current sampling value, the third current as valid current sampling data and the fourth current as zero current sampling value, the fifth current as valid current sampling data and the sixth current as zero current sampling value, the calculation unit records the first current, the third current, and the fifth current as the first phase current, the second phase current, and the third phase current; when the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero current sampling value, the tenth current as valid current sampling data and the ninth current as zero current sampling value, the twelfth current as valid current sampling data and the eleventh current as zero current sampling value, the calculation unit records the eighth current, the tenth current, and the twelfth current as the first phase current, the second phase current, and the third phase current.

[0089] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A current sampling system, characterized in that, The current sampling system includes a three-phase motor circuit and a processing module; A three-phase circuit for a motor includes the first phase, the second phase, and the third phase. The first phase includes a first IGBT chip and a second IGBT chip connected in series, wherein the first IGBT chip includes a first switch and a first diode connected in parallel with opposite current flows, and the second IGBT chip includes a second switch and a second diode connected in parallel with opposite current flows. The second phase includes a third IGBT chip and a fourth IGBT chip connected in series, wherein the third IGBT chip includes a third switch and a third diode connected in parallel with opposite current flows, and the fourth IGBT chip includes a fourth switch and a fourth diode connected in parallel with opposite current flows. The third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series, wherein the fifth IGBT chip includes a fifth switch and a fifth diode connected in parallel with opposite current flows, and the sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flows. The processing module includes a sampling unit and a calculation unit. The sampling unit samples the current flowing through the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch at the trough and peak times of a switching cycle, and forms the first current sampling value and the second current sampling value, respectively. The calculation unit extracts effective current sampling data within the first current sampling value and the second current sampling value at the trough of the switching cycle, and corrects the zero current sampling data within the first current sampling value and the second current sampling value into estimated current sampling data based on the sum of the three-phase currents being zero or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first phase current, the second phase current and the third phase current respectively. At the trough moment, the first current sampling value includes: the first current of the first switch, the second current of the second switch, the third current of the third switch, the fourth current of the fourth switch, the fifth current of the fifth switch, and the sixth current of the sixth switch. At the peak moment, the second current sampling value includes: the seventh current of the first switch, the eighth current of the second switch, the ninth current of the third switch, the tenth current of the fourth switch, the eleventh current of the fifth switch, and the twelfth current of the sixth switch. The switching period is different from the period of the motor sinusoidal current; The calculation unit determines the positive or negative status of the first current, the third current, and the fifth current at the trough time; When two of the first, third, and fifth currents are positive and the other is negative, the current sampled data is estimated based on the three-phase currents and the current with a negative value corrected to zero. When two of the first, third, and fifth currents are negative and the other is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any one of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other current among the two negative currents is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero. The calculation unit determines the positive or negative status of the eighth, tenth, and twelfth currents at the peak of the wave. When two of the eighth, tenth, and twelfth currents are positive and the other is negative, the current sampled data is estimated based on the three-phase currents and the current value is negative when the sum of the three-phase currents is zero. When two of the eighth, tenth, and twelfth currents are negative and the other is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any one of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other current among the two negative currents is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

2. The current sampling system as described in claim 1, characterized in that, At the trough moment, the value of the triangular carrier wave used to control the opening and closing of any one or any of the first, second, and third phases in the three-phase circuit of the motor is less than the value of the sinusoidal current of the motor at the same moment, so that the first, third, and fifth switches are turned on, and the second, fourth, and sixth switches are turned off. At the peak of the wave, the value of the triangular carrier wave used to control the opening and closing of any one or any one of the first, second, and third phases in the three-phase circuit of the motor is greater than the value of the sinusoidal current of the motor at the same time, so that the first, third, and fifth switches are turned off, and the second, fourth, and sixth switches are turned on. When the first phase current, the second phase current, or the third phase current is positive, current flows through the first switch and the second diode, or the third switch and the fourth diode, or the fifth switch and the sixth diode, so that the first current, the third current, or the fifth current are valid current sampling data, and the second current, the fourth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current are current sampling zero values. When the first phase current, the second phase current, or the third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode, making the eighth current, the tenth current, or the twelfth current valid current sampling data, and the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the ninth current, and the eleventh current have zero current sampling values.

3. The current sampling system as described in claim 2, characterized in that, The calculation unit also extracts and compares the first current sample value and the second current sample value at the peak time; When the data of the first current sampling value and the second current sampling value are: the seventh current and the eighth current, or the ninth current and the tenth current, or the eleventh current and the twelfth current, which are both zero current sampling values, the calculation unit keeps the first current sampling value and the second current sampling value extracted at the trough time of the previous switching cycle unchanged. When the data of the first current sampling value and the second current sampling value are: the first current as valid current sampling data and the second current as zero current sampling value, the third current as valid current sampling data and the fourth current as zero current sampling value, the fifth current as valid current sampling data and the sixth current as zero current sampling value, the calculation unit records the first current, the third current and the fifth current as the first phase current, the second phase current and the third phase current. When the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero current sampling value, the tenth current as valid current sampling data and the ninth current as zero current sampling value, the twelfth current as valid current sampling data and the eleventh current as zero current sampling value, the calculation unit records the eighth current, the tenth current and the twelfth current as the first phase current, the second phase current and the third phase current.

4. A current sampling method, characterized in that, Includes the following steps: A three-phase motor circuit and processing module are configured with interconnected components. The three-phase motor circuit includes a first phase, a second phase, and a third phase. The first phase includes a first IGBT chip and a second IGBT chip connected in series. The first IGBT chip includes a first switch and a first diode connected in parallel with opposite current flows, and the second IGBT chip includes a second switch and a second diode connected in parallel with opposite current flows. The second phase includes a third IGBT chip and a fourth IGBT chip connected in series. The third IGBT chip includes a third switch and a third diode connected in parallel with opposite current flows, and the fourth IGBT chip includes a fourth switch and a fourth diode connected in parallel with opposite current flows. The third phase includes a fifth IGBT chip and a sixth IGBT chip connected in series. The fifth IGBT chip includes a fifth switch and a fifth diode connected in parallel with opposite current flows, and the sixth IGBT chip includes a sixth switch and a sixth diode connected in parallel with opposite current flows. The processing module includes a sampling unit and a calculation unit. The sampling unit samples the current flowing through the first switch transistor, the second switch transistor, the third switch transistor, the fourth switch transistor, the fifth switch transistor, and the sixth switch transistor at the trough and peak times of a switching cycle, respectively forming the first current sampling value and the second current sampling value. The calculation unit extracts effective current sampling data within the first current sampling value and the second current sampling value at the trough of the switching cycle, and corrects the zero current sampling data within the first current sampling value and the second current sampling value into estimated current sampling data based on the sum of the three-phase currents being zero or the amplitude and angle relationship of the motor sinusoidal current, so as to obtain the first phase current, the second phase current and the third phase current respectively. The sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, respectively, to form the first current sampling value and the second current sampling value. The steps include: At the trough moment, the first current sampling value includes: the first current of the first switch, the second current of the second switch, the third current of the third switch, the fourth current of the fourth switch, the fifth current of the fifth switch, and the sixth current of the sixth switch. At the peak moment, the second current sampling value includes: the seventh current of the first switch, the eighth current of the second switch, the ninth current of the third switch, the tenth current of the fourth switch, the eleventh current of the fifth switch, and the twelfth current of the sixth switch. The switching period is different from the period of the motor sinusoidal current; The calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current. The steps for obtaining the first-phase current, second-phase current, and third-phase current respectively include: The calculation unit determines the positive or negative status of the first current, the third current, and the fifth current at the trough time; When two of the first, third, and fifth currents are positive and the other is negative, the current sampled data is estimated based on the three-phase currents and the current with a negative value corrected to zero. When two of the first, third, and fifth currents are negative and the other is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any one of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other current among the two negative currents is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero. The calculation unit determines the positive or negative status of the eighth, tenth, and twelfth currents at the peak of the wave. When two of the eighth, tenth, and twelfth currents are positive and the other is negative, the current sampled data is estimated based on the three-phase currents and the current value is negative when the sum of the three-phase currents is zero. When two of the eighth, tenth, and twelfth currents are negative and the other is positive, the change in motor angle is calculated based on the ratio of ½ of the switching period to the period of the motor sinusoidal current. The current correction is calculated based on the sampling time of any one of the two negative currents and the amplitude of the motor sinusoidal current. The current correction is then added to that current as estimated current sampling data. Finally, the other current among the two negative currents is corrected to the estimated current sampling data based on the fact that the sum of the three-phase currents is zero.

5. The current sampling method as described in claim 4, characterized in that, The sampling unit samples the current flowing through the first, second, third, fourth, fifth, and sixth switching transistors at the trough and peak times of a switching cycle, respectively, to form the first current sampling value and the second current sampling value. The steps include: At the trough moment, the value of the triangular carrier wave used to control the opening and closing of any one or any of the first, second, and third phases in the three-phase circuit of the motor is less than the value of the sinusoidal current of the motor at the same moment, so that the first, third, and fifth switches are turned on, and the second, fourth, and sixth switches are turned off. At the peak of the wave, the value of the triangular carrier wave used to control the opening and closing of any one or any one of the first, second, and third phases in the three-phase circuit of the motor is greater than the value of the sinusoidal current of the motor at the same time, so that the first, third, and fifth switches are turned off, and the second, fourth, and sixth switches are turned on. When the first phase current, the second phase current, or the third phase current is positive, current flows through the first switch and the second diode, or the third switch and the fourth diode, or the fifth switch and the sixth diode, so that the first current, the third current, or the fifth current are valid current sampling data, and the second current, the fourth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current are current sampling zero values. When the first phase current, the second phase current, or the third phase current is negative, current flows through the second switch and the first diode, or the fourth switch and the third diode, or the sixth switch and the fifth diode, making the eighth current, the tenth current, or the twelfth current valid current sampling data, and the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the ninth current, and the eleventh current have zero current sampling values.

6. The current sampling method as described in claim 5, characterized in that, The calculation unit extracts effective current sampling data within the first and second current sampling values ​​at the trough of the switching cycle, and corrects the zero-value current sampling data within the first and second current sampling values ​​to estimated current sampling data based on the sum of the three-phase currents being zero, or the amplitude and angle relationship of the motor sinusoidal current. The step of obtaining the first-phase current, second-phase current, and third-phase current respectively further includes: The calculation unit also extracts and compares the first current sample value and the second current sample value at the peak time; When the data of the first current sampling value and the second current sampling value are: the seventh current and the eighth current, or the ninth current and the tenth current, or the eleventh current and the twelfth current, which are both zero current sampling values, the calculation unit keeps the first current sampling value and the second current sampling value extracted at the trough time of the previous switching cycle unchanged. When the data of the first current sampling value and the second current sampling value are: the first current as valid current sampling data and the second current as zero current sampling value, the third current as valid current sampling data and the fourth current as zero current sampling value, the fifth current as valid current sampling data and the sixth current as zero current sampling value, the calculation unit records the first current, the third current and the fifth current as the first phase current, the second phase current and the third phase current. When the data of the first current sampling value and the second current sampling value are: the eighth current as valid current sampling data and the seventh current as zero current sampling value, the tenth current as valid current sampling data and the ninth current as zero current sampling value, the twelfth current as valid current sampling data and the eleventh current as zero current sampling value, the calculation unit records the eighth current, the tenth current and the twelfth current as the first phase current, the second phase current and the third phase current.

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