Phase current reconstruction method and apparatus

Abstract

The application discloses a three-phase current reconstruction method, comprising the following steps: calculating three-phase duty ratios of a current PWM period according to three-phase current values of a previous PWM period; judging whether the current PWM period enters a non-observation area and determining a non-observation phase and an observation phase according to the three-phase duty ratios; when the current PWM period enters the non-observation area, obtaining a phase current of the non-observation phase according to a duty ratio of the current PWM period of the non-observation phase, a duty ratio of the previous PWM period, a duty ratio of a previous previous PWM period, a phase current of the previous PWM period and a phase current of the previous previous PWM period by using a current increment model; reconstructing the phase current of the current PWM period according to the phase current of the non-observation phase and a phase current of the observation phase; the non-observation area refers to that bus currents corresponding to two non-zero voltage vectors cannot be collected in the current PWM period. The application further discloses a three-phase current reconstruction device, which can improve voltage utilization, working range and load capacity of a motor.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, and in particular to a phase current reconstruction method and apparatus. Background Technology

[0002] In recent years, with the continuous research and application of high-performance permanent magnet materials, the size and weight of permanent magnet synchronous motors (PMSMs) have been greatly reduced, and their power density has been significantly improved. They have been widely developed and applied in aerospace, military, medical devices, new energy electric vehicles and other fields.

[0003] Permanent magnet synchronous motors typically employ vector control, which requires three-phase AC signals as feedback to achieve closed-loop current control. Two common current sampling methods are: 1. Using Hall effect sensors to sample two-phase currents and calculating the third-phase current from those two phases; 2. Using a single bus resistor to sample the current and reconstruct the motor's three-phase current. While Hall effect sensor two-phase current sampling offers high accuracy in phase current reconstruction, it is relatively large and expensive, making it unsuitable for cost-sensitive applications.

[0004] The principle of single-resistor current sampling is to collect the DC bus current using a sampling resistor installed on the DC bus. Then, based on the correspondence between the DC bus current and the motor phase current under different switching states, the three-phase current value is determined. Compared with the traditional two-resistor or three-resistor sampling method, this current method saves sampling channels and reduces the cost and size of the motor controller.

[0005] However, single-resistor current sampling technology has an unobservable region where the basic vector action time is less than the minimum current sampling time Tmin, affecting current sampling. While PWM (Pulse Width Modulation) phase-shifting can solve the current sampling problem in the sampling blind zone, this method requires shifting one or two phases of the PWM to ensure that the basic voltage vector action time is greater than Tmin. However, when the motor operates in the over-modulation region and is in the unobservable region, the three-phase stator current cannot be obtained through PWM phase-shifting, and the motor cannot operate normally in this region, reducing its load-carrying capacity.

[0006] Therefore, there is a need for an improved phase current reconstruction method and device that can reduce the footprint and power consumption, operate normally in the overmodulation region, and increase the motor's load-carrying capacity. Summary of the Invention

[0007] In view of the above problems, the purpose of this invention is to provide a three-phase current reconfiguration method and apparatus that can reduce the occupied area and power consumption, operate normally in the overmodulation region, and increase the motor's load-carrying capacity.

[0008] According to a first aspect of the present invention, a three-phase current reconstruction method is provided, comprising: calculating the three-phase duty cycle of the current PWM cycle based on the three-phase current values ​​of the previous PWM cycle; determining whether the current PWM cycle has entered the unobservable region and identifying the unobservable phase and the observable phase based on the three-phase duty cycle; when the current PWM cycle enters the unobservable region, using a current increment model to obtain the phase current of the unobservable phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle, wherein the current PWM cycle is the k-th PWM cycle, the previous PWM cycle is the (k-1)-th PWM cycle, and the previous PWM cycle is the (k-2)-th PWM cycle; reconstructing the phase current of the current PWM cycle based on the phase current of the unobservable phase and the phase current of the observable phase; wherein the unobservable region refers to the current of the bus corresponding to two non-zero voltage vectors that cannot be sampled in the current PWM cycle, the unobservable phase refers to a phase whose phase current cannot be sampled in the current PWM cycle, and the observable phase refers to a phase whose phase current can be sampled in the current PWM cycle.

[0009] Optionally, the current increment model is:

[0010]

[0011] Where m is any one of the three phases, Duty m (k) represents the duty cycle of the corresponding phase in the current PWM cycle. m (k-1) represents the duty cycle of the corresponding phase in the previous PWM cycle. m (k-2) represents the duty cycle of the corresponding phase in the previous PWM cycle, i m (k) represents the current of the corresponding phase in the current PWM cycle, i m (k-1) represents the current of the corresponding phase in the previous PWM cycle, i m (k-2) represents the current of the corresponding phase in the previous PWM cycle.

[0012] Optionally, determining whether the current PWM cycle has entered the unobservable region based on the three-phase duty cycle includes:

[0013] The duration of the high-level and low-level signals of the three phases are determined based on the three-phase duty cycle and the duration of the PWM cycle.

[0014] The duration between adjacent voltage vectors is obtained based on the high-level duration and low-level duration of the three phases;

[0015] The current PWM cycle is determined to be in the non-observation region based on the duration between adjacent voltage vectors and the minimum sampling duration of the bus current.

[0016] Optionally, the current PWM cycle enters the non-observation region when the duration between at least one adjacent voltage vector is less than the minimum sampling duration.

[0017] Optionally, the three-phase current reconstruction method further includes storing the duty cycle and phase current of the current PWM cycle and the previous PWM cycle.

[0018] Optionally, the three-phase current reconstruction method further includes: when the current PWM cycle enters the unobserved region, determining whether the unobserved region is an overmodulation region; wherein, when the unobserved region is an overmodulation region, a current increment model is used to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle; and the phase current of the current PWM cycle is reconstructed based on the phase current of the unobserved phase and the phase current of the observable phase; and when the unobserved region is not an overmodulation region, the three-phase PWM signals are phase-shifted so that the duration between adjacent voltage vectors is not less than the minimum sampling duration, and the phase current of the current PWM cycle is reconstructed.

[0019] According to another aspect of the present invention, a three-phase current reconstruction device is provided, comprising: a duty cycle calculation module, configured to calculate the three-phase duty cycle of the current PWM cycle based on the three-phase current values ​​of the previous PWM cycle; a judgment module, configured to determine whether the current PWM cycle has entered the unobservable region and to determine the unobservable phase and the observable phase based on the three-phase duty cycle; and a current reconstruction module, configured to, when the current PWM cycle enters the unobservable region, use a current increment model to calculate the duty cycle of the unobservable phase based on the current PWM cycle duty cycle, the previous PWM cycle duty cycle, the previous PWM cycle duty cycle, and the phase current of the previous PWM cycle, and the previous PWM cycle duty cycle duty cycle of the unobservable phase, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the current reconstruction module, configured to, when the current PWM cycle enters the unobservable region, use a current increment model to calculate the duty cycle of the unobservable phase based on the current PWM cycle duty cycle, the previous PWM cycle duty cycle, the previous PWM cycle duty cycle, and the phase current of the previous PWM cycle duty cycle duty cycle, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the current reconstruction module, configured to, when the current PWM cycle enters the unobservable region, use a current increment model to calculate the current PWM cycle duty cycle, the previous PWM cycle duty cycle duty cycle, the previous PWM cycle duty cycle duty cycle of the unobservable phase, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the current reconstruction module, configured to, when the current PWM cycle enters the unobservable region, use a current increment model to calculate the current PWM cycle duty cycle, the previous PWM cycle duty cycle duty cycle, the previous PWM cycle duty cycle duty cycle, and the previous PWM cycle phase current, and the previous PWM cycle phase current, and the previous PWM cycle phase The phase current of the PWM cycle is obtained from the phase current of the unobserved phase, and the phase current of the current PWM cycle is reconstructed based on the phase current of the unobserved phase and the phase current of the observable phase. The current PWM cycle is the k-th PWM cycle, the previous PWM cycle is the (k-1)-th PWM cycle, and the preceding PWM cycle is the (k-2)-th PWM cycle. The unobserved region refers to the bus current corresponding to two non-zero voltage vectors that cannot be sampled in the current PWM cycle. The unobserved phase refers to a phase whose phase current cannot be sampled in the current PWM cycle, and the observable phase refers to a phase whose phase current can be sampled in the current PWM cycle.

[0020] Optionally, the current increment model adopted by the current reconstruction module is:

[0021]

[0022] Where m is any one of the three phases, Dutym (k) represents the duty cycle of the corresponding phase in the current PWM cycle. m (k-1) represents the duty cycle of the corresponding phase in the previous PWM cycle. m (k-2) represents the duty cycle of the corresponding phase in the previous PWM cycle, i m (k) represents the current of the corresponding phase in the current PWM cycle, i m (k-1) represents the current of the corresponding phase in the previous PWM cycle, i m (k-2) represents the current of the corresponding phase in the previous PWM cycle.

[0023] Optionally, the judgment module is further configured to determine the high-level duration and low-level duration of the three phases based on the three-phase duty cycle and the duration of the PWM cycle; obtain the duration between adjacent voltage vectors based on the high-level duration and low-level duration of the three phases; and determine whether the current PWM cycle has entered the non-observation region based on the duration between adjacent voltage vectors and the minimum sampling duration of the bus current.

[0024] Optionally, when the duration between adjacent voltage vectors is less than the minimum sampling duration, the determination module determines that the current PWM cycle has entered the non-observation region.

[0025] Optionally, the three-phase current reconstruction device further includes a storage module for storing the duty cycle and phase current of the current PWM cycle and the previous PWM cycle.

[0026] Optionally, when the current PWM cycle enters the unobserved region, the judgment module is further used to determine whether the unobserved region is an overmodulation region; when the unobserved region is an overmodulation region, the current reconstruction module uses a current increment model to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle, and reconstructs the phase current of the current PWM cycle based on the phase current of the unobserved phase and the phase current of the observable phase; and when the unobserved region is not an overmodulation region, the current reconstruction module performs phase shifting processing on the three-phase PWM signals so that the duration between adjacent voltage vectors is not less than the minimum sampling duration, and reconstructs the phase current of the current PWM cycle.

[0027] The three-phase current reconstruction method and apparatus provided in this application use a current increment model to predict the phase current of the unobserved phase in the current PWM cycle based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. Then, the three-phase current is reconstructed based on the phase current of another observable phase. This can improve the voltage utilization rate of the motor and increase the operating range and load capacity of the motor.

[0028] Furthermore, this application can predict the current in the non-observation area without requiring motor parameters, which is simple and easy to implement. Attached Figure Description

[0029] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0030] Figure 1 This diagram illustrates the structure of a system applying the three-phase current reconstruction method of this application.

[0031] Figure 2 This diagram illustrates the principle of the unobserved region of the space voltage vector.

[0032] Figure 3 This diagram illustrates the principle of phase-shifting processing in related technologies.

[0033] Figure 4 A flowchart illustrating a three-phase current reconstruction method according to an embodiment of the present invention is shown;

[0034] Figure 5 A flowchart illustrating a three-phase current reconstruction method according to an embodiment of the present invention is shown;

[0035] Figure 6 A schematic diagram of a three-phase current reconfiguration device according to an embodiment of the present invention is shown. Detailed Implementation

[0036] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements or modules are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0037] It should be understood that, in the following description, "circuit" may include single or combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuit. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it may be directly coupled or connected to the other element, or there may be intermediate elements; the connection between elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0038] Furthermore, certain terms are used in this patent specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This patent specification and claims do not distinguish components based on differences in name, but rather on differences in function.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] Before describing the three-phase current reconstruction method of the embodiments of this application, an exemplary description of a system applying the three-phase current reconstruction method will be given first.

[0041] like Figure 1 As shown, the system includes a motor M, a three-phase bridge inverter 101, a DC power supply Vbus, and a bus current acquisition device 102.

[0042] For example, the DC power supply Vbus is converted into a three-phase power supply for motor M via a three-phase bridge inverter 101. Motor M can be a PMSM. The three-phase bridge inverter 101 can be controlled using SVPWM (Space Vector Pulse Width Modulation). The bus current sampling device 102 can employ a typical single-resistor sampling circuit, for example, including a sampling resistor Rs connected between the negative terminal of the DC power supply Vbus and the three-phase bridge inverter 101. The voltage across the sampling resistor Rs is transmitted to the MCU (Microcontroller Unit) via an operational amplifier and an ADC (Analog-to-digital converter) module. In the MCU, it is converted into a bus current, which is used for subsequent three-phase current reconstruction. The reconstructed three-phase current is then used as feedback current to achieve vector control of the motor.

[0043] Understandably, the three-phase bridge inverter uses SVPWM modulation for control, and the switching transistors have eight operating states, including six non-zero voltage vectors (V1-V6) and two zero voltage vectors (V0 and V7). This divides the voltage space plane into a hexagon, as shown below. Figure 2 As shown. The basic principle of phase current reconstruction is to obtain the current of two phases of the three phases by sampling the bus current at different times within one PWM cycle. Then, the current of the other phase is obtained through Kirchhoff's laws, thus obtaining the three-phase current of the motor. In practical applications, considering the time from the issuance of the PWM command to the acquisition of the bus current from the sampling resistor Rs, there are mainly delays in the switching transistor operation, the bus current settling time, and the output delay of the operational amplifier. After the PWM command is issued, a minimum sampling time Tmin is required to obtain the voltage on the sampling resistor Rs. Therefore, the sampling of the bus current must meet the sampling window.

[0044] See Figure 2 When the output voltage vector is in the low modulation region or sector switching boundary, there may be a situation within one PWM cycle where the duration of the non-zero voltage vector is less than the minimum sampling duration Tmin. In this case, the sampled bus current is not the phase current. In the embodiments of this application, the region where two different phase currents cannot be sampled within one PWM cycle is collectively referred to as the non-observation region.

[0045] In existing technologies, to ensure that two-phase currents can be sampled in each PWM cycle, phase shifting is required in the unobservable region to guarantee that two-phase currents are sampled within one PWM cycle. For example... Figure 3As shown, for example, the three-phase line includes: phase A, phase B and phase C. The sampling window corresponding to the original (100) vector is less than the minimum sampling time Tmin. By phase shifting, the high level of phase A is shifted to the left by Ts, so that the sampling window corresponding to the (100) vector is equal to the minimum sampling time Tmin. Similarly, the sampling window corresponding to the original (110) vector is less than the minimum sampling time Tmin. Shifting the high level of phase C to the right by Ts can make the sampling window corresponding to the phase-shifted (110) vector equal to the minimum sampling time Tmin.

[0046] When the unobservable region is an overmodulated region, for example, Figure 2 The region outside the inscribed circle of the hexagon shown is the overmodulation region. Even phase shifting cannot satisfy the condition that the sampling window must be longer than the minimum sampling time Tmin, resulting in the inability to acquire two phase currents within one PWM cycle. Therefore, the three-phase current reconstruction method based on phase shifting cannot meet the reconstruction requirements of the three-phase current in the overmodulation region.

[0047] Based on this, in various embodiments of this application, a three-phase current reconstruction method that can adapt to the over-modulation region is proposed, so that three-phase current reconstruction can be achieved based on the bus current in the over-modulation region.

[0048] Figure 4 A schematic flowchart of a three-phase current reconstruction method according to an embodiment of the present invention is shown. Figure 4 As shown, the three-phase current reconstruction method includes the following steps.

[0049] In step S410, the three-phase duty cycle of the current PWM cycle is calculated based on the three-phase current values ​​of the previous PWM cycle.

[0050] In this embodiment, step S410 is as follows: obtain the three-phase current values ​​ia, ib, and ic of the previous PWM cycle, where ia is the phase current corresponding to phase A, ib is the phase current corresponding to phase B, and ic is the phase current corresponding to phase C; calculate the three-phase duty cycles DutyA, DutyB, and DutyC through coordinate transformation, current controller, and SVPWM, where DutyA is the duty cycle of phase A, DutyB is the duty cycle of phase B, and DutyC is the duty cycle of phase C.

[0051] In step S420, the current PWM cycle is determined to be in the unobservable region based on the three-phase duty cycle, and the unobservable phase and observable phase are determined.

[0052] In this embodiment, the non-observable region refers to the region where the bus current corresponding to two non-zero voltage vectors cannot be sampled within the current PWM cycle. That is, two different phase currents cannot be sampled within a PWM cycle, resulting in the inability to complete the phase current reconstruction for the current PWM cycle. The non-observable phase refers to a phase whose phase current cannot be sampled within the current PWM cycle, while the observable phase refers to a phase whose phase current can be sampled within the current PWM cycle.

[0053] In step S430, when the current PWM cycle enters the unobserved region, the current increment model is used to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle.

[0054] In this embodiment, the voltage equation of the permanent magnet synchronous motor in a three-axis coordinate system is:

[0055] Where m is one of phases A, B, and C, U m R is the voltage of the corresponding phase. m For the resistance of the corresponding phase, i m L represents the current of the corresponding phase. m For the inductance of the corresponding phase, e m U is the back electromotive force of the corresponding phase. N This is the voltage at the center point.

[0056] Within one PWM cycle, assuming the back electromotive force and center voltage remain constant, and ignoring changes in inductor current and motor resistance, the phase current and phase voltage exhibit a linear relationship. The relationship between phase voltage and duty cycle is as follows:

[0057] U m =Vbus×Duty m Duty m Vbus represents the duty cycle of the corresponding phase and the bus voltage.

[0058] The voltage equation for the k-th period can be expressed as:

[0059]

[0060] The voltage equation for the (k-1)th period can be expressed as:

[0061]

[0062] Subtracting the two equations, we can see that within two adjacent PWM cycles, the increment of the phase current is directly proportional to the increment of the duty cycle, i.e., Vbus × [Duty]. m (k)-Duty m [(k-1)]=

[0063] R m [i m (k)-i m [(k-1)], where Duty m (k) represents the duty cycle of the corresponding phase in the current PWM cycle (i.e., the kth PWM cycle). m (k-1) represents the duty cycle of the corresponding phase in the previous PWM cycle (i.e., the (k-1)th PWM cycle), i m (k) represents the current of the corresponding phase in the current PWM cycle (i.e., the kth PWM cycle), i m (k-1) represents the current of the corresponding phase in the previous PWM cycle (i.e., the (k-1)th PWM cycle).

[0064] Therefore, the duty cycle (Duty) of the current PWM cycle (i.e., the k-th PWM cycle) can be used as a basis. m (k) Duty cycle of the previous PWM cycle (i.e., the (k-1)th PWM cycle). m (k-1) Duty cycle of the previous PWM cycle (i.e., the (k-2)th PWM cycle). m (k-2) and the phase current i of the previous PWM cycle (i.e., the (k-1)th PWM cycle). m (k-1), the phase current i of the previous PWM cycle (i.e., the (k-2)th PWM cycle). m (k-2) Obtain the phase current i of the non-observed phase. m (k).

[0065] The phase current of the unobserved phase in the current PWM cycle can be obtained using the following current increment model:

[0066]

[0067] In step S440, the phase current of the current PWM cycle is reconstructed based on the phase current of the unobserved phase and the phase current of the observable phase.

[0068] In this embodiment, when the unobserved phase is phase A, the phase A current i is calculated according to the formula in step S430. A (k); When the observable phase is phase C, the phase current obtained by sampling can be used as the phase C current i. C (k), according to Kirchhoff's laws, the B-phase current is: i B (k)=-i A (k)-i C (k).

[0069] In a preferred embodiment, step S440 is further included after step S450.

[0070] In step S450, the duty cycle and phase current of the current PWM cycle and the previous PWM cycle are stored.

[0071] In this embodiment, the duty cycle and phase current of the current PWM cycle and the previous PWM cycle are stored to prepare for current prediction in the next PWM cycle.

[0072] In some embodiments, step S420 includes the following steps.

[0073] In step S421, the high-level duration and low-level duration of the three phases are determined based on the three-phase duty cycle and the duration of the PWM cycle.

[0074] In step S422, the duration between adjacent voltage vectors is obtained based on the duration of the high level and the duration of the low level of the three phases.

[0075] In step S423, it is determined whether the current PWM cycle has entered the non-observation region based on the minimum sampling duration of the bus current between adjacent voltage vectors.

[0076] For example, assuming Tp is the duration of the PWM period, then the high-level duration T of phase A is... A1 =Tp*Duty A The duration of the low level of phase A, T A0 =Tp*(1-Duty) A The high-level duration T of phase B B1 =Tp*Duty B The duration of the low level in phase B, T B0 =Tp*(1-Duty) B The high-level duration T of phase C C1 =Tp*Duty C The duration of the low level of phase C, T C0 =Tp*(1-Duty) C The duration between adjacent voltage vectors is obtained based on the high-level and low-level durations of the three phases; for example, the duration between adjacent voltage vectors between phase A and phase B is |T A1 -T B1 | / 2. When the duration between at least one adjacent voltage vector is less than the minimum sampling duration, the current PWM cycle enters the unobservable region.

[0077] It is understandable that when the current PWM cycle enters the overmodulation region, it is impossible to acquire the two-phase current through phase shifting. Based on the method of this application embodiment, it is not necessary to acquire the two-phase current. Instead, a current increment model is used to reconstruct the three-phase current value of the current PWM cycle based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, and the phase current of the previous PWM cycle, thereby realizing vector control of the motor.

[0078] It is understood that when the non-observation region is not the overmodulation region, that is, when the PWM signal is phase-shifted and the duration between adjacent voltage vectors is not less than the minimum sampling time, the PWM signal can be phase-shifted to sample two phase currents within the PWM cycle and realize the reconstruction of the three-phase current. The reconstruction of the three-phase current can also be realized based on the method of the embodiments of this application. The embodiments of this application do not limit this.

[0079] The three-phase current reconstruction method provided in this invention uses a current increment model to predict the phase current of the unobserved phase in the current PWM cycle based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. Then, the three-phase current is reconstructed based on the phase current of another observable phase. This can improve the voltage utilization rate of the motor and increase the operating range and load capacity of the motor.

[0080] Furthermore, this application can predict the current in the non-observation area without requiring motor parameters, which is simple and easy to implement.

[0081] Figure 5 A schematic flowchart of a three-phase current reconstruction method according to another embodiment of the present invention is shown. Figure 5 As shown, the three-phase current reconstruction method includes the following steps.

[0082] In step S510, the duty cycle of the current PWM cycle and the size of the sampling window are calculated.

[0083] In this embodiment, the duty cycle of the current PWM cycle can be calculated based on the phase current of the previous PWM cycle. For details, please refer to the description in the previous embodiment, which will not be repeated here.

[0084] The size of the sampling window is the minimum sampling duration Tmin during which a non-zero voltage vector cannot be continuously sampled, for example, Tmin = T d +T set +T A , among which, T d T is the operating time of the switching transistor. set T is the bus current settling time. A This represents the output duration of the op-amp.

[0085] In step S520, it is determined whether the non-observation region has been entered. If the non-observation region has not been entered, step S530 is executed; if the non-observation region has been entered, step S540 is executed.

[0086] In this embodiment, the high-level duration and low-level duration of the three phases are determined based on the three-phase duty cycle and the duration of the PWM cycle; the duration between adjacent voltage vectors is obtained based on the high-level duration and low-level duration of the three phases; and the minimum sampling duration of the bus current is used to determine whether the current PWM cycle has entered the non-observation region based on the duration between adjacent voltage vectors.

[0087] In step S530, the normal three-phase current is reconfigured.

[0088] In this embodiment, when the current PWM cycle has not entered the non-observation region, the two-phase current can be collected normally to obtain the three-phase current, and the three-phase current and duty cycle of the current PWM cycle and the previous PWM cycle can be recorded.

[0089] In step S540, it is determined whether the non-observation region is an overmodulation region. If it is an overmodulation region, step S550 is executed; otherwise, step S560 is executed.

[0090] In step S550, the current increment model is used to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. The phase current of the current PWM cycle is reconstructed based on the phase current of the unobserved phase and the phase current of the observable phase.

[0091] In this embodiment, when the non-observation region is an overmodulation region, the phase current of the non-observation phase can be obtained based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. For details, please refer to the description in the previous embodiment, which will not be repeated here.

[0092] In step S560, the three-phase PWM signals are phase-shifted to reconstruct the phase current of the current PWM cycle.

[0093] In step S570, the three-phase current and duty cycle of the current PWM cycle and the previous PWM cycle are stored.

[0094] In step S580, motor vector calculation control is performed.

[0095] In this embodiment, motor vector control is performed based on the three-phase current of the current PWM cycle. For example, the motor is controlled using SVPWM.

[0096] Figure 6 A schematic diagram of a three-phase current reconfiguration device according to an embodiment of the present invention is shown. Figure 6 As shown, the three-phase current reconstruction device 600 includes a duty cycle calculation module 601, a judgment module 602, and a current reconstruction module 603.

[0097] The duty cycle calculation module 601 is used to calculate the three-phase duty cycle of the current PWM cycle based on the three-phase current value of the previous PWM cycle.

[0098] The judgment module 602 is used to determine whether the current PWM cycle has entered the unobservable region and to identify the unobservable phase and the observable phase based on the three-phase duty cycle.

[0099] In this embodiment, the judgment module 602 is specifically used to determine the high-level duration and low-level duration of the three phases based on the three-phase duty cycle and the duration of the PWM cycle; to obtain the duration between adjacent voltage vectors based on the high-level duration and low-level duration of the three phases; and to determine whether the current PWM cycle has entered the non-observation region based on the duration between adjacent voltage vectors and the minimum sampling duration of the bus current.

[0100] When the duration between at least one adjacent voltage vector is less than the minimum sampling duration, the judgment module 62 determines that the current PWM cycle has entered the non-observation region.

[0101] It is understandable that when the current PWM cycle enters the overmodulation region, it is impossible to acquire the two-phase current through phase shifting. Based on the method of this application embodiment, it is not necessary to acquire the two-phase current. Instead, a current increment model is used to reconstruct the three-phase current value of the current PWM cycle based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, and the phase current of the previous PWM cycle, thereby realizing vector control of the motor.

[0102] It is understood that when the non-observation region is not the overmodulation region, that is, when the PWM signal is phase-shifted and the duration between adjacent voltage vectors is not less than the minimum sampling time, the PWM signal can be phase-shifted to sample two phase currents within the PWM cycle and realize the reconstruction of the three-phase current. The reconstruction of the three-phase current can also be realized based on the method of the embodiments of this application. The embodiments of this application do not limit this.

[0103] The current reconstruction module 603 is used to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle when the current PWM cycle enters the unobserved region, and to reconstruct the phase current of the current PWM cycle based on the phase current of the unobserved phase and the phase current of the observable phase.

[0104] In a preferred embodiment, the three-phase current reconstruction device further includes a recording module 604 for storing the duty cycle of the current PWM cycle and the phase current of the previous PWM cycle.

[0105] In some preferred embodiments, when the current PWM cycle enters the unobserved region, the judgment module 602 is further used to determine whether the unobserved region is an overmodulation region.

[0106] When the unobserved region is an overmodulation region, the current reconstruction module 603 uses a current increment model to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle, and reconstructs the phase current of the current PWM cycle based on the phase current of the unobserved phase and the phase current of the observable phase.

[0107] And when the non-observation region is not the overmodulation region, the current reconstruction module 603 performs phase shifting processing on the three-phase PWM signals to reconstruct the phase current of the current PWM cycle.

[0108] In practical applications, the duty cycle calculation module 601, the judgment module 602, the current reconstruction module 603, and the recording module 604 can be implemented by the processor of the three-phase current reconstruction device. Of course, the processor needs to run the computer program in the memory to implement its functions.

[0109] It should be noted that the three-phase current reconstruction device provided in the above embodiments is only illustrated by the division of the above-described program modules. In practical applications, the above processing can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program modules to complete all or part of the processing described above. In addition, the three-phase current reconstruction device and the three-phase current reconstruction method embodiments provided in the above embodiments belong to the same concept, and the specific implementation process can be found in the method embodiments, which will not be repeated here.

[0110] It should be noted that those skilled in the art will understand that the terms “during,” “when,” and “when…” used herein in relation to circuit operation are not strict terms indicating an action that occurs immediately upon the commencement of a startup action, but rather that there may be some small but reasonable delays, such as various propagation delays, between the startup action and the reaction action initiated by it. The terms “approximately” or “substantially” used herein mean that an element value is expected to be close to the declared value or position. However, as is well known in the art, there are always small deviations that make it difficult for the value or position to be strictly the declared value. It has been properly determined in the art that a deviation of at least ten percent (10%) (or at least twenty percent (20%) for semiconductor doping concentration) is a reasonable deviation from the described accurate ideal target. When used in conjunction with signal states, the actual voltage value or logic state of the signal (e.g., “1” or “0”) depends on whether positive or negative logic is used.

[0111] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims and their equivalents.

Claims

1. A three-phase current reconstruction method, characterized in that, include: Calculate the three-phase duty cycle of the current PWM cycle based on the three-phase current values ​​of the previous PWM cycle; Determine whether the current PWM cycle has entered the unobservable region and identify the unobservable and observable phases based on the three-phase duty cycle; When the current PWM cycle enters the unobserved region, the current increment model is used to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. Here, the current PWM cycle is the kth PWM cycle, the previous PWM cycle is the (k-1)th PWM cycle, and the previous PWM cycle is the (k-2)th PWM cycle. The phase current of the current PWM cycle is reconstructed based on the phase current of the unobserved phase and the phase current of the observable phase. The non-observable region refers to the bus current corresponding to two non-zero voltage vectors that cannot be sampled in the current PWM cycle. The non-observable phase refers to a phase whose phase current cannot be sampled in the current PWM cycle. The observable phase refers to a phase whose phase current can be sampled in the current PWM cycle.

2. The three-phase current reconstruction method according to claim 1, characterized in that, The current increment model is as follows: Where m is any one of the three phases, Duty m (k) represents the duty cycle of the corresponding phase in the current PWM cycle. m (k-1) represents the duty cycle of the corresponding phase in the previous PWM cycle. m (k-2) represents the duty cycle of the corresponding phase in the previous PWM cycle, i m (k) represents the current of the corresponding phase in the current PWM cycle, i m (k-1) represents the current of the corresponding phase in the previous PWM cycle, i m (k-2) represents the current of the corresponding phase in the previous PWM cycle.

3. The three-phase current reconstruction method according to claim 1, characterized in that, Determining whether the current PWM cycle has entered the unobservable region based on the three-phase duty cycle includes: The duration of the high-level and low-level signals of the three phases are determined based on the three-phase duty cycle and the duration of the PWM cycle. The duration between adjacent voltage vectors is obtained based on the high-level duration and low-level duration of the three phases; The current PWM cycle is determined to be in the non-observation region based on the duration between adjacent voltage vectors and the minimum sampling duration of the bus current.

4. The three-phase current reconstruction method according to claim 3, characterized in that, The current PWM cycle enters the non-observation region when the duration between at least one adjacent voltage vector is less than the minimum sampling duration.

5. The three-phase current reconstruction method according to claim 1, characterized in that, Also includes: Store the duty cycle and phase current of the current PWM cycle and the previous PWM cycle.

6. The three-phase current reconstruction method according to claim 1, characterized in that, Also includes: When the current PWM cycle enters the unobservable region, it is determined whether the unobservable region is an overmodulation region. When the unobservable region is an overmodulation region, the current increment model is used to obtain the phase current of the unobservable phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. The phase current of the current PWM cycle is reconstructed based on the phase current of the unobservable phase and the phase current of the observable phase. as well as When the non-observation region is not the overmodulation region, the three-phase PWM signal is phase-shifted so that the duration between adjacent voltage vectors is not less than the minimum sampling duration, and the phase current of the current PWM cycle is reconstructed.

7. A three-phase current reconfiguration device, characterized in that, include: The duty cycle calculation module is used to calculate the three-phase duty cycle of the current PWM cycle based on the three-phase current values ​​of the previous PWM cycle. The judgment module is used to determine whether the current PWM cycle has entered the unobservable region and to identify the unobservable and observable phases based on the three-phase duty cycle. The current reconstruction module is used to obtain the phase current of the unobserved phase when the current PWM cycle enters the unobservable region by using the current increment model based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. It also reconstructs the phase current of the current PWM cycle based on the phase current of the unobserved phase and the phase current of the observable phase. The current PWM cycle is the kth PWM cycle, the previous PWM cycle is the (k-1)th PWM cycle, and the previous PWM cycle is the (k-2)th PWM cycle. The non-observable region refers to the bus current corresponding to two non-zero voltage vectors that cannot be sampled in the current PWM cycle. The non-observable phase refers to a phase whose phase current cannot be sampled in the current PWM cycle. The observable phase refers to a phase whose phase current can be sampled in the current PWM cycle.

8. The three-phase current reconstruction device according to claim 7, characterized in that, The current increment model used in the current reconstruction module is as follows: Where m is any one of the three phases, Duty m (k) represents the duty cycle of the corresponding phase in the current PWM cycle. m (k-1) represents the duty cycle of the corresponding phase in the previous PWM cycle. m (k-2) represents the duty cycle of the corresponding phase in the previous PWM cycle, i m (k) represents the current of the corresponding phase in the current PWM cycle, i m (k-1) represents the current of the corresponding phase in the previous PWM cycle, i m (k-2) represents the current of the corresponding phase in the previous PWM cycle.

9. The three-phase current reconstruction device according to claim 7, characterized in that, The judgment module is also used to determine the high-level duration and low-level duration of the three phases based on the three-phase duty cycle and the duration of the PWM cycle; to obtain the duration between adjacent voltage vectors based on the high-level duration and low-level duration of the three phases; and to determine whether the current PWM cycle has entered the non-observation region based on the duration between adjacent voltage vectors and the minimum sampling duration of the bus current.

10. The three-phase current reconstruction device according to claim 9, characterized in that, When the duration between adjacent voltage vectors is less than the minimum sampling duration, the judgment module determines that the current PWM cycle has entered the non-observation region.

11. The three-phase current reconstruction device according to claim 7, characterized in that, Also includes: The storage module is used to store the duty cycle and phase current of the current PWM cycle and the previous PWM cycle.

12. The three-phase current reconstruction device according to claim 7, characterized in that, When the current PWM cycle enters the unobservable region, the judgment module is also used to determine whether the unobservable region is an overmodulation region; When the unobserved region is an overmodulation region, the current reconstruction module uses a current increment model to obtain the phase current of the unobserved phase based on the duty cycle of the current PWM cycle, the duty cycle of the previous PWM cycle, the duty cycle of the previous PWM cycle, the phase current of the previous PWM cycle, and the phase current of the previous PWM cycle. The module also reconstructs the phase current of the current PWM cycle based on the phase current of the unobserved phase and the phase current of the observable phase. as well as When the non-observation region is not the overmodulation region, the current reconstruction module performs phase shifting processing on the three-phase PWM signal so that the duration between adjacent voltage vectors is not less than the minimum sampling duration, and reconstructs the phase current of the current PWM cycle.

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