Method and system for controlling a rotary electric machine

Abstract

The invention relates to a method (200) and a system (100) for controlling a rotary electric machine, wherein a state of the rotary electric machine is determined between a low speed state and a high speed state. In the low speed state, a first rotor position (P1) and a first rotor speed (S1) are estimated based on a PWM-internal current ripple (ΔX), an average current vector (Y) and an inductance vector. A second rotor position (P2) and a second rotor speed (S2) are estimated based on an average current flowing through a stator phase winding. The state of the rotary electric machine is selected based on the estimated first rotor speed (S1) and / or the estimated second rotor speed (S2). In the low speed state, a PWM signal is updated based on the estimated first rotor position (P1), while in the high speed state, the PWM signal is updated based on the estimated second rotor position (P2).

Description

Technical Field

[0001] This invention relates to the control of rotary electric machines. Background Technology

[0002] Traditional electric motor drive systems typically include a motor controller connected to an electric motor, which comprises a rotor and a stator. The stator further comprises N phases, each consisting of a winding consisting of a set of coils connected in a series-parallel configuration. The motor controller achieves optimal torque generation and efficient performance of the motor drive system by applying optimal commutation to the stator phase windings. To maximize system performance and operate the system at its maximum efficiency, the motor controller requires information about the relative position of the rotor with respect to the stator. Therefore, the motor is typically connected to a position sensor, such as a set of Hall effect sensors or an optical encoder. The position sensor is usually connected to the motor controller using a wiring harness.

[0003] As described above, the position sensor increases the system cost. Furthermore, the position sensor and its associated wiring harness are prone to failure due to exposure to high temperatures, vibrations, and proximity to high-speed moving mechanical objects (typically part of the rotor). Additionally, the placement of the position sensor within the motor's mechanical package occupies space, resulting in a suboptimal motor package design.

[0004] Attempts have been made to reduce system costs and improve system robustness by controlling electric motors without using position sensors. Existing sensorless control methods involve sensing or estimating the back electromotive force voltage induced in the stator windings due to the relative motion between the rotor and stator. However, this method is only effective when the rotor rotates at relatively high speeds. Another approach to sensorless control of electric motors involves injecting high-frequency voltages into the stator windings to determine the rotor position by utilizing rotor saliency. However, this method results in suboptimal machine efficiency due to undesirable harmonics in the stator winding current, further leading to unwanted vibration and noise in the machine.

[0005] Therefore, there is a need in the art for a method and system for controlling rotating electric machines that at least solves the above-mentioned problems. Summary of the Invention

[0006] In one aspect of the invention, the present invention relates to a method for controlling a rotating electric machine. The method includes the following steps: determining a state of the rotating electric machine based on the speed of its rotor. The state includes a high-speed state when the rotor speed is greater than a predetermined threshold speed and a low-speed state when the rotor speed is less than the predetermined threshold speed. If the rotating electric machine is in the low-speed state, a current ripple and an average current vector within a pulse width modulation (PWM) cycle are calculated by measuring the current in the stator phase windings of the rotating electric machine. An inductance vector is calculated based on the current ripple within the PWM cycle. A first rotor position (P1) and a first rotor speed (S1) are estimated based on the inductance vector and the average current vector. If the rotating electric machine is in the high-speed state, the current in the stator phase windings of the rotating electric machine is measured within the PWM cycle. An average current in each stator phase winding of the rotating electric machine is determined within the PWM cycle. A second rotor position (P2) and a second rotor speed (S2) are estimated based on the average current in the stator phase windings within the PWM cycle. The state of the rotating motor is selected between the high-speed state and the low-speed state based on the estimated first rotor speed (S1) and / or the estimated second rotor speed (S2). If the low-speed state is selected, the pulse width modulation signal is updated based on the estimated first rotor position (P1). If the high-speed state is selected, the pulse width modulation signal is updated based on the estimated second rotor position (P2).

[0007] In an embodiment of the invention, the state of the rotating motor is initialized to the low-speed state by determining the initial position (Pi) of the rotor relative to the stator of the rotating motor through a set of commutations applied to the stator phase windings and determining the value of the DC-side current corresponding to each commutation, and the rotor position is initialized based on the commutation that results in the maximum current. A pulse width modulation signal is applied to the stator phase windings based on the initial position (Pi) of the rotor; thereafter, the state of the rotating motor is determined to be the low-speed state.

[0008] In another embodiment of the invention, if the rotating motor is determined to be in the low-speed state, the current in the stator windings of all phases of the rotating motor is measured by measuring at least two samples from at least N-1 of the total N stator windings. In one embodiment, it is checked whether current sampling of the stator windings corresponding to all N phases has been performed. In one embodiment, if current sampling of the stator windings corresponding to all N phases has not been performed, multiple current samples of the Nth phase within the pulse width modulation period are reconstructed.

[0009] In another embodiment of the invention, if the rotating motor is determined to be in the high-speed state, the measurement of the current in the stator phase windings of all phases of the rotating motor is performed by measuring at least one sample from at least N-1 of the total N stator phase windings. In one embodiment, it is checked whether current sampling of the stator phase windings corresponding to all N has been performed. In one embodiment, if current sampling of the stator phase windings corresponding to all N has not been performed, multiple current samples of the Nth phase within the pulse width modulation period are reconstructed.

[0010] In another embodiment of the invention, the average current flowing in the stator phase windings is estimated based on the assumed rotor position, DC bus voltage, and PWM signal applied to the motor, and the estimated average current is compared with a determined average current. In one embodiment, the estimation of the second rotor position (P2) and the second rotor speed (S2) is corrected by an error metric based on the difference between the estimated average current and the determined average current.

[0011] In another aspect, the present invention relates to a system for controlling a rotating electric machine. The system includes: a pulse width modulator (PWM) for applying a pulse width modulated signal to a stator phase winding of the rotating electric machine; a plurality of semiconductor power switches for receiving the PWM signal and converting the signal into an AC voltage for the stator phase winding of the rotating electric machine; a plurality of current sensing devices for sensing currents in the corresponding stator phase windings of the rotating electric machine; and a control unit. The control unit is configured to determine a state of the rotating electric machine based on the speed of the rotor, between a high-speed state when the rotor speed is greater than a predetermined threshold speed and a low-speed state when the rotor speed is less than the predetermined threshold speed. If the rotating electric machine is in the low-speed state, the control unit is configured to calculate a current ripple and an average current vector within the PWM by measuring the current in the stator phase winding of the rotating electric machine during the PWM period; calculate an inductance vector based on the current ripple within the PWM; and estimate a first rotor position (P1) and a first rotor speed (S1) based on the inductance vector and the average current vector. If the rotating motor is in the high-speed state, the control unit is configured to measure the current in the stator phase windings of the rotating motor within a pulse width modulation period. The control unit is also configured to determine the average current in each stator phase winding of the rotating motor within the pulse width modulation period; estimate a second rotor position (P2) and a second rotor speed (S2) based on the average current in the stator phase windings within the pulse width modulation period; and select a state of the rotating motor between the high-speed state and the low-speed state based on the estimated first rotor speed (S1) and / or the estimated second rotor speed (S2). If the low-speed state is selected, the control unit is configured to update the pulse width modulation signal based on the estimated first rotor position (P1); and if the high-speed state is selected, the control unit is configured to update the pulse width modulation signal based on the estimated second rotor position (P2).

[0012] In one embodiment of the invention, the control unit is further configured to perform the following steps: initializing the state of the rotating motor to the low-speed state; determining the initial position (Pi) of the rotor of the rotating motor relative to the stator of the rotating motor by applying a set of commutations to the stator phase windings and determining the value of the DC-side current corresponding to each commutation, and initializing the rotor position based on the commutation that results in the maximum current; applying a pulse width modulation signal to the stator phase windings based on the initial position (Pi) of the rotor; and then determining the state of the rotating motor to the low-speed state.

[0013] In another embodiment of the invention, the plurality of power switches include a three-phase H-bridge having six semiconductor power switches arranged in three H-bridge arms, such that each arm has a high-power semiconductor switch and a low-power semiconductor switch. In one embodiment, the system is configured to use space vector modulation (SVM) technology to generate pulse width modulation (PWM) signals based on center-aligned PWM.

[0014] In another embodiment of the invention, the system has a current monitor configured to: measure one current sample per phase per pulse width modulation cycle during the high-speed state, substantially at the center of the zero-sequence commutation; and measure two current samples per phase per pulse width modulation cycle during the low-speed state, substantially equidistant from the center of the zero-sequence commutation.

[0015] In another embodiment of the invention, the system has at least two current sensing devices, wherein each current sensing device measures the current flowing through the low-power semiconductor switch of each H-bridge arm. In an alternative embodiment, the system has at least two current sensing devices, wherein each current sensing device is connected in series with a stator phase winding.

[0016] In another embodiment of the invention, the analog measurement bandwidth of the current monitor is substantially greater than 10 times the frequency of the PWM signal applied to the stator phase winding.

[0017] In another embodiment of the invention, the system is configured to change the frequency of the pulse width modulator according to variables including an estimated first rotor speed (S1) and an estimated second rotor speed (S2). Attached Figure Description

[0018] Reference will be made to embodiments of the invention, examples of which are illustrated in the accompanying drawings. These figures are intended to be illustrative and not limiting. Although the invention has been generally described in the context of these embodiments, it should be understood that the scope of the invention is not intended to be limited to these specific embodiments.

[0019] Figure 1 A flowchart of a method for controlling a rotary motor according to an embodiment of the present invention is shown.

[0020] Figure 2 An exemplary variation of the speed of the rotor of a rotating electric motor in operation over time is shown according to an embodiment of the present invention.

[0021] Figure 3 The internal current ripple of a PWM based on three current variations is shown according to an embodiment of the present invention.

[0022] Figure 4The diagram illustrates a reconstructed PWM internal current ripple based on a DC bus-side current variation according to an embodiment of the present invention, the DC bus-side current variation being constructed using individual current variations in each stator winding phase.

[0023] Figure 5 A flowchart of a trained estimation model for estimating rotor position and rotor speed according to an embodiment of the present invention is shown.

[0024] Figure 6 A system for controlling a rotary electric motor according to an embodiment of the present invention is shown.

[0025] Figure 7 A system for controlling a rotary electric motor according to an embodiment of the present invention is shown.

[0026] Figure 8 The invention illustrates PWM signal generation using a center-aligned PWM-based space vector modulation technique and a current sampling scheme in zero-sequence commutation, according to an embodiment of the invention. Detailed Implementation

[0027] This invention relates to a method and system for controlling a rotating electric motor. More specifically, this invention relates to a method and system for sensorless control of a rotating electric motor.

[0028] Figure 1 A flowchart illustrating the method steps involved in a method 200 for controlling a rotating electric motor according to an embodiment of the present invention is shown. To control the rotating electric motor, states of the rotating electric motor are defined. In this invention, when the speed of the rotor of the rotating electric motor is less than a predetermined threshold speed, the state of the rotating motor is defined as a low-speed state; when the speed of the rotor is greater than the predetermined threshold speed, the state of the rotating motor is defined as a high-speed state. (Refer to...) Figure 2 , Figure 2 The diagram illustrates the change in rotor speed of a rotating electric motor over time during operation, where the rotor speed is confined to three regions. (See diagram for details.) Figure 2 As shown, when the rotating electric motor starts from a stationary position, its state is defined as a low-speed state until the rotor speed remains below a first predetermined threshold speed (N2). Thereafter, when the rotor speed exceeds the first predetermined threshold (N2), the state of the rotating electric motor is defined as a high-speed state as long as the rotor speed remains above a second predetermined threshold speed (N1). When the rotor speed drops below the second predetermined threshold speed (N1), the state of the rotating electric motor is again defined as a low-speed state.

[0029] like Figure 1As shown, in step 2A, when starting control of the rotating motor from the stop position, the control unit initializes the state of the rotating motor to a low-speed state. In step 2B, the control unit determines the initial position (Pi) of the rotor of the rotating motor relative to the stator of the rotating motor. This is done by applying a set of commutations to the stator phase windings, determining the value of the DC-side current corresponding to each commutation, and starting the rotor position based on the commutation that results in the maximum current. In step 2C, a pulse width modulation signal is applied to the stator phase windings based on the initial position (Pi) of the rotor, thereby initializing the control of the rotating motor. Method 200 also includes a step 2D of measuring the DC bus voltage.

[0030] In step 2E, the state of the rotating electric motor is determined between a high-speed state and a low-speed state based on the rotor speed, as explained above. When the control of the rotating electric motor is initialized as in steps 2A to 2D, the state of the rotating electric motor is initially determined to be a low-speed state. Afterwards, the state of the rotating electric motor is defined based on the rotor speed. The method steps involved in controlling the rotating electric motor when its state is determined to be a low-speed state are separate from the method steps involved in controlling the rotating electric motor when its state is determined to be a high-speed state.

[0031] If it is determined that the rotational state is at a low speed, method 200 proceeds to step 2F; otherwise, method 200 proceeds to step 2M. In step 2F, the current in the stator phase windings of all phases of the rotating electric machine is measured. This is done by measuring at least two samples from at least N-1 of the total N stator phase windings. In step 2G, it is checked whether current sampling corresponding to all N phase stator phase windings has been performed. If current sampling corresponding to all N phase stator phase windings has been performed, method 200 proceeds to step 2I; otherwise, method 200 proceeds to step 2H, where, since current sampling corresponding to all N phase stator phase windings has not been performed, multiple current samples of the Nth phase within the pulse width modulation period are reconstructed. This reconstruction is achieved by utilizing the fact that the sum of the currents flowing through all phase windings at a single moment is zero. (Reference) Figure 8 This illustrates an exemplary current sampling scheme for reconstructing the current of the Nth phase, as described above. Figure 8 The current sampling scheme shown pertains to a three-phase motor, wherein two current samples are measured for each phase per PWM cycle within zero commutation as part of space vector modulation, such that the two current samples for each phase are approximately equidistant from the center of zero commutation. This completes the current sampling of the stator phase windings corresponding to all N phases of the rotating motor.

[0032] In step 2I as described above, the PWM current ripple (ΔX) is calculated by measuring the current in the stator phase windings of the rotating motor within the pulse width modulation period. The PWM current ripple (ΔX) is defined as the change or variation of the current in the stator phase windings within the pulse width modulation period. This change or variation of the current with the PWM period is related to the inductance of the stator windings, which is an indicator of the rotor's position in the rotating motor. Figure 3 The diagram illustrates the current changes or variations across all three phases of an exemplary rotating motor. For example... Figure 3 As shown, the PWM internal current ripple (ΔX) consists of three separate current changes (ΔX) corresponding to the three current changes of the rotating motor. a ΔX b ΔX c )composition. Figure 3 The method describes how to calculate the PWM internal current ripple (ΔX) by reconstructing the DC-side current using current samples from a single stator phase winding and determining the current change in the reconstructed DC-side current. Figure 4 Another embodiment of the invention is shown, wherein the PWM internal current ripple (ΔX) consists of a single current change.

[0033] Furthermore, in step 2J, the average current vector (Y) is calculated by measuring the current in the stator phase windings of the rotating electrical machine within the pulse width modulation period. The average current vector (Y) represents the magnitude of the current in the stator phase windings. Figure 3 In the embodiment shown, the average current vector (Y) is derived from the three-phase (Y) a Y b Y c The average current composition within the PWM cycle. Figure 4 In the embodiment shown, the average current vector (y) consists of the average current over the PWM cycle for the reconstructed DC-side current waveform.

[0034] In step 2K, the inductance vector is calculated based on the PWM internal current ripple (ΔX). For stator phase windings with low inductance and resistance ratios, the values ​​contained in the PWM internal current ripple (ΔX) are typically large. Similarly, for stator phase windings with high inductance and resistance ratios, the values ​​contained in the PWM internal current ripple (ΔX) are typically small. The inductance vector represents the rotor position of the rotating electric machine. This is because the inductance of the stator phase windings changes with the rotor position due to the salient pole effect in salient pole motors or magnetic saturation in non-salient pole motors, or a combination thereof. In summary, the rotor position can be inferred from the inductance vector.

[0035] In step 2L, the first rotor position (P1) and the first rotor speed (S1) are estimated based on the inductance vector and the average current vector (Y). The rotor position and rotor speed are inferred based on the inductance vector, and the average current vector (Y) is used to compensate for the effects of magnetic saturation caused by the current flowing in the stator phase windings. Method 200 then continues to step 2P.

[0036] As described above, if the state of the rotating motor is not determined to be a low-speed state, i.e., the state of the rotating motor is determined to be a high-speed state, then method 200 moves from step 2E to step 2M. In step 2M, the current in the stator phase windings of the rotating motor is measured within the pulse width modulation period. This is accomplished by measuring the current in the stator phase windings for all phases of the rotating motor by measuring at least one sample from at least N-1 stator phase windings out of a total of N stator phase windings. In step 2N, it is checked whether current sampling of the stator phase windings corresponding to all N has been performed. If current sampling of the stator phase windings corresponding to all N has been performed, then method 200 moves to step 2P; otherwise, method 200 moves to step 2O, where, since current sampling of the stator phase windings corresponding to all N has not been performed, the multiple current samples for the Nth phase within the pulse width modulation period are reconstructed according to the same principle as described above, i.e., the sum of the currents flowing through all phase windings at a single moment is zero. Method 200 then moves to step 2P.

[0037] In step 2P, the average current of each stator phase winding of the rotating electric machine is determined within the pulse width modulation period. In step 2Q, the second rotor position (P2) and the second rotor speed (S2) are estimated based on the average current in the stator phase windings within the pulse width modulation period. Figure 5 In one embodiment of the invention depicted in the flowchart, the estimation of the second rotor position (P2) and the second rotor speed (S2) is accomplished by means of a trained estimation model of a rotating electric machine, incorporating knowledge of the inductance and resistance of the stator windings. The dynamic estimation model is used to estimate the current flowing in the stator phase windings based on the assumed rotor position, the DC bus voltage measured in step 2D, and the PWM signal applied to the motor. The estimated current thus measured is then compared with a determined average current in step 2P. The difference between the estimated current and the determined average current is called an error metric, and this error metric is used to further correct the estimation of the second rotor position and the second rotor speed, such that the value of the error metric remains close to zero.

[0038] In step 2R, according to Figure 2The embodiments described herein select a state of the rotating motor between a high-speed state and a low-speed state based on an estimated first rotor speed (S1) and / or an estimated second rotor speed (S2). In one embodiment, the state of the rotating motor is based on a combination of the estimated first rotor speed (S1) and the estimated second rotor speed (S2). In embodiments of the invention, the state of the rotating motor thus selected in step 2R is fed as the determined state of the rotating motor in step 2E; that is, the state of the rotating motor selected in step 2R is used as the determined state of the rotating motor in step 2E.

[0039] In step 2S, the control unit checks the state selected in step 2R. If the state of the rotating motor is selected as low speed, method 200 moves to step 2T, where the pulse width modulation signal applied to the stator phase winding is updated based on the estimated first rotor position (P1). Conversely, if the state of the rotating motor is selected as high speed, method 200 moves to step 2U, where the pulse width modulation signal applied to the stator phase winding is updated based on the estimated second rotor position (P2).

[0040] In another aspect, the present invention relates to a system 100 for controlling a rotary electric motor. Figure 6 A system 100 for controlling a rotating electric motor according to an embodiment of the present invention is shown. In one embodiment, system 100 is connected to a DC voltage and current source 110, such as a battery that powers system 100 and the rotating electric motor. Figure 6 As shown, system 100 includes: a pulse width modulator 120 for applying a pulse width modulated signal to the stator phase winding of a rotating electric machine; a plurality of semiconductor power switches 130 for receiving the pulse width modulated signal and converting the signal into an AC voltage for the stator phase winding of the rotating electric machine; a plurality of current sensing devices 140 for sensing the current in the corresponding stator phase winding of the rotating electric machine; and a control unit 150 configured to perform method steps 2A to 2U as described above.

[0041] In an embodiment of the invention, the plurality of semiconductor power switches 130 include a three-phase H-bridge having six semiconductor power switches 130AH, 130BH, 130CH, 130AL, 130BL, and 130CL arranged in three H-bridge arms, such that each arm has a high-power semiconductor switch and a low-power semiconductor switch. As a result, the three-phase H-bridge has a total of three high-power semiconductor switches 130AH, 130BH, and 130CH and three low-power semiconductor switches 130AL, 130BL, and 130CL. In one embodiment, the plurality of power switches 130 include metal-oxide-semiconductor field-effect transistors (MOSFETs) of insulated-gate bipolar transistors (IGBTs). In an embodiment of the invention, the system 100 is configured to use space vector modulation techniques based on, for example... Figure 8 The pulse width modulation signal is generated by center-aligned pulse width modulation.

[0042] In another embodiment of the invention, the plurality of current sensing devices 140 include at least two current sensing devices, wherein each current sensing device measures the current flowing through the low-power semiconductor switches 130AL, 130BL, 130CL of each H-bridge arm. Figure 6 The illustrated embodiment describes three current sensing devices 140A, 140B, and 140C, wherein each current sensing device measures the current flowing through the low-power semiconductor switches 130AL, 130BL, and 130CL in each H-bridge arm. Figure 7 In an alternative embodiment of the invention shown, the plurality of current sensing devices 140 includes at least two current sensing devices, wherein each current sensing device is connected in series with a stator phase winding. In one embodiment, the plurality of current sensing devices 140 includes three current sensing devices 140A, 140B, and 140C, wherein each current sensing device is connected in series with three stator phase windings corresponding to an exemplary three-phase rotating electric motor.

[0043] like Figure 6 As shown, system 100 also includes a current monitor 160 configured to measure one current sample per phase per pulse width modulation cycle when the rotating motor is in a high-speed state, wherein the current sampling is performed substantially at the center of the zero-sequence commutation. The current monitor 160 is also configured to measure two current samples per phase per pulse width modulation cycle when the rotating motor is in a low-speed state, wherein the current sampling is performed substantially equidistant from the center of the zero-sequence commutation.

[0044] In order to accurately detect changes or variations in current within the pulse width modulation period, the current sensing device 140 preferably has a sufficiently large analog measurement bandwidth, preferably more than 10 times the frequency of the PWM signal applied to the stator phase winding.

[0045] In operation, system 100 is configured via pulse width modulator 120 to generate PWM signals of different frequencies for the stator phase windings at different rotor speeds of the rotating electric motor, and to generate PWM duty cycle values ​​for different arms of the three-phase H-bridge, such as... Figure 8 As shown. The PWM duty cycle is defined by the ratio of 1s to 0s received from the pulse width modulator. During low-speed conditions, the lower frequency of the PWM signal allows for more accurate measurement of current changes or variations because the lower PWM frequency allows for an increased duration between the first and last current samples within the PWM cycle. During high-speed conditions, the higher PWM frequency allows for a greater number of current samples per unit rotor movement, and correspondingly allows for a larger update rate of the PWM signal to the stator phase windings, thus resulting in better control bandwidth.

[0046] Advantageously, the present invention provides a method and system for controlling a rotating electric motor, thereby providing sensorless control of the rotating electric motor and eliminating the need for sensors such as Hall sensors in the motor. This allows for optimal mechanical packaging of the electric motor.

[0047] Furthermore, the method of the present invention provides sensorless control of the rotating electric motor at all operating speeds, especially at low speeds, without increasing unwanted harmonic currents in the stator phase windings.

[0048] Although the invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method (200) for controlling a rotating electric motor, the method comprising the following steps: The state of the rotating electric motor is determined based on the speed of its rotor, and the state includes a high-speed state when the speed of the rotor is greater than a predetermined threshold speed and a low-speed state when the speed of the rotor is less than the predetermined threshold speed. If the rotary motor is in the low-speed state: The current ripple (ΔX) and average current vector (Y) within the PWM are calculated by measuring the current in the stator phase windings of the rotating motor during the pulse width modulation period. The inductance vector is calculated based on the PWM internal current ripple (ΔX); The first rotor position (P1) and the first rotor speed (S1) are estimated based on the inductance vector and the average current vector (Y); If the rotary motor is in the high-speed state: The current in the stator phase windings of the rotating electric machine is measured within the pulse width modulation period; The average current of each stator phase winding of the rotating electric machine is determined within the pulse width modulation period; The second rotor position (P2) and the second rotor speed (S2) are estimated based on the average current in the stator phase windings during the pulse width modulation period. The state of the rotating motor is selected between the high-speed state and the low-speed state based on the estimated first rotor speed (S1) and / or the estimated second rotor speed (S2); If the low-speed state is selected, the pulse width modulation signal is updated based on the estimated first rotor position (P1); as well as If the high-speed state is selected, the pulse width modulation signal is updated based on the estimated second rotor position (P2).

2. The method (200) according to claim 1, further comprising the following steps: The state of the rotary motor is initialized to the low-speed state; The initial position (Pi) of the rotor of the rotating machine relative to the stator of the rotating machine is determined by applying a set of commutations to the stator phase windings and determining the value of the DC side current corresponding to each commutation, and the rotor position is initialized based on the commutation that results in the maximum current. A pulse width modulation signal is applied to the stator phase winding based on the initial position (Pi) of the rotor; Then, the state of the rotary motor is determined to be the low-speed state.

3. The method (200) according to claim 1, wherein, If the rotating motor is determined to be in the low-speed state, the current in the stator phase windings of all phases of the rotating motor is measured by measuring at least two samples from at least N-1 of the total N stator phase windings.

4. The method (200) according to claim 3, further comprising the following steps: Check whether current sampling of the stator phase windings corresponding to all N has been performed.

5. The method (200) according to claim 4, further comprising the following step: If current sampling of the stator phase windings corresponding to all N is not performed, multiple current samples of the Nth phase within the pulse width modulation period are reconstructed.

6. The method (200) according to claim 1, wherein, If the rotating electric motor is determined to be in the high-speed state, the current in the stator phase windings of all phases of the rotating electric motor is measured by measuring at least one sample of at least N-1 stator phase windings out of a total of N stator phase windings.

7. The method (200) according to claim 6, further comprising the following step: Check whether current sampling of the stator phase windings corresponding to all N has been performed.

8. The method (200) according to claim 7, further comprising the step of: If current sampling of the stator phase windings corresponding to all N is not performed, multiple current samples of the Nth phase within the pulse width modulation period are reconstructed.

9. The method (200) according to claim 1, further comprising the following steps: The average current flowing in the stator phase windings is estimated based on the assumed rotor position, DC bus voltage, and PWM signal applied to the motor, and the estimated average current is compared with the determined average current.

10. The method (200) according to claim 9, wherein, The estimation of the second rotor position (P2) and the second rotor speed (S2) is corrected by an error metric based on the difference between the estimated average current and the determined average current.

11. A system (100) for controlling a rotating electric motor, the system comprising: A pulse width modulator (120) is used to apply a pulse width modulated signal to the stator phase windings of the rotating electric machine; Multiple semiconductor power switches (130) are used to receive pulse width modulation signals and convert the signals into AC voltages for the stator phase windings of the rotating motor; Multiple current sensing devices (140) are used to sense the current in the stator phase windings corresponding to the rotating electric motor; as well as A control unit (150) is configured to perform the following steps: Based on the speed of the rotor of the rotary motor, the state of the rotary motor is determined between a high-speed state when the speed of the rotor is greater than a predetermined threshold speed and a low-speed state when the speed of the rotor is less than the predetermined threshold speed. If the rotary motor is in the low-speed state: The current ripple (ΔX) and average current vector (Y) within the PWM are calculated by measuring the current in the stator phase windings of the rotating motor during the pulse width modulation period. The inductance vector is calculated based on the PWM internal current ripple (ΔX); The first rotor position (P1) and the first rotor speed (S1) are estimated based on the inductance vector and the average current vector (Y); If the rotary motor is in the high-speed state: The current in the stator phase windings of the rotating electric machine is measured within the pulse width modulation period; The average current of each stator phase winding of the rotating electric machine is determined within the pulse width modulation period; The second rotor position (P2) and the second rotor speed (S2) are estimated based on the average current in the stator phase windings during the pulse width modulation period. The state of the rotating motor is selected between the high-speed state and the low-speed state based on the estimated first rotor speed (S1) and / or the estimated second rotor speed (S2); If the low-speed state is selected, the pulse width modulation signal is updated based on the estimated first rotor position (P1); as well as If the high-speed state is selected, the pulse width modulation signal is updated based on the estimated second rotor position (P2).

12. The system (100) according to claim 11, wherein, The control unit (150) is further configured to perform the following steps: The state of the rotary motor is initialized to the low-speed state; The initial position (Pi) of the rotor of the rotating machine relative to the stator of the rotating machine is determined by applying a set of commutations to the stator phase windings and determining the value of the DC side current corresponding to each commutation, and the rotor position is initialized based on the commutation that results in the maximum current. A pulse width modulation signal is applied to the stator phase winding based on the initial position (Pi) of the rotor; Then, the state of the rotary motor is determined to be the low-speed state.

13. The system (100) according to claim 11, wherein, The plurality of power switches (130) include a three-phase H-bridge having six semiconductor power switches (130AH, 130BH, 130CH, 130AL, 130BL, 130CL) arranged in three H-bridge arms, such that each arm has a high-power semiconductor switch and a low-power semiconductor switch.

14. The system (100) of claim 13, wherein the system is configured to use space vector modulation techniques to generate pulse width modulation signals based on center-aligned PWM.

15. The system (100) according to claim 14, wherein, The current monitor (160) is configured to measure one current sample per phase per pulse width modulation cycle during the high-speed state, with current sampling essentially at the center of zero-sequence commutation. Furthermore, during the low-speed state, two current samples are measured per phase per pulse width modulation cycle, and current sampling is performed substantially equidistant from the center of the zero-sequence commutation.

16. The system (100) according to claim 13, wherein the system comprises at least two current sensing devices (140), wherein, Each current sensing device measures the current flowing through the low-power semiconductor switches (130AL, 130BL, 130CL) of each H-bridge arm.

17. The system (100) according to claim 13, wherein the system comprises at least two current sensing devices (140), wherein, Each current sensing device is connected in series with a stator phase winding.

18. The system (100) according to claim 15, wherein, The analog measurement bandwidth of the current monitor (160) is substantially greater than 10 times the frequency of the PWM signal applied to the stator phase winding.

19. The system (100) of claim 11, wherein the system is configured to change the frequency of the pulse width modulator (120) according to variables including an estimated first rotor speed (S1) and an estimated second rotor speed (S2).

Images