Current sampling device of dual-motor driving system and refrigerating system

Abstract

The invention discloses a current sampling device of a dual-motor driving system and a refrigerating system, the dual-motor driving system at least comprises a five-bridge-arm circuit connected with a bus capacitor, and the five-bridge-arm circuit is used for driving a first motor and a second motor which are connected with the five-bridge-arm circuit. The current sampling device comprises a current sensor arranged on a direct current bus between the five-bridge-arm circuit and the bus capacitor, and the current sensor acquires current parameters of the first motor and the second motor by acquiring current parameters of the five-bridge-arm circuit in different switching states. Compared with the prior art, the single current sensor is adopted and arranged on the direct-current bus, and is matched with different switching states of the five-bridge-arm circuit, so that the current of a plurality of bridge arms or phase lines can be monitored through one current sensor, and the hardware cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to motor drive systems, and more particularly to a current sampling device and a cooling system for a dual-motor drive system. Background Technology

[0002] In motor drive systems, current sampling is one of the key steps to achieve precise control. Traditional motor drive systems typically employ a three-phase bridge arm structure, using combinations of the switching states of the upper and lower bridge arms to drive and control the motor.

[0003] In recent years, five-arm drive schemes have gradually become a research hotspot. Compared with traditional three-phase arm drive schemes, the five-arm drive scheme, by adding two extra arms, can achieve more flexible switching state combinations, thereby improving the control accuracy and efficiency of the system. Especially in dual-motor drive systems, the five-arm drive scheme can reduce hardware costs while achieving control of two motors, and has high engineering application value.

[0004] In terms of current sampling, traditional solutions typically require configuring an independent current sensor for each bridge arm or phase line, which not only increases the hardware cost and complexity of the system, but may also lead to signal interference and installation space limitations.

[0005] Therefore, how to design a current sampling device and cooling system for a dual-motor drive system that can reduce the number of current sensors, lower costs and complexity is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] To address the problem that existing technologies require an independent current sensor for each bridge arm or phase line during current sampling, which increases the hardware cost and complexity of the system, this invention proposes a current sampling device and cooling system for a dual-motor drive system.

[0007] The technical solution of the present invention is to propose a current sampling device for a dual-motor drive system. The dual-motor drive system includes at least a five-arm circuit connected to a bus capacitor. The five-arm circuit is used to drive a first motor and a second motor connected thereto. The current sampling device includes a current sensor disposed on a DC bus between the five-arm circuit and the bus capacitor. The current sensor obtains the current parameters of the first motor and the second motor by collecting the current parameters of the five-arm circuit in different switching states.

[0008] Furthermore, the five-arm circuit has a first arm, a second arm, a third arm, a fourth arm, and a fifth arm;

[0009] The three-phase windings of the first motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm, and the fifth bridge arm, and the three-phase windings of the second motor are respectively connected to the midpoints of the third bridge arm, the fourth bridge arm, and the fifth bridge arm.

[0010] Furthermore, the switching states of the first bridge arm and the third bridge arm are consistent, and the switching states of the second bridge arm and the fourth bridge arm are consistent.

[0011] When the upper arm of the first bridge arm is turned on and the lower arms of the second and fifth bridge arms are turned on, the current sensor collects the sum of the a-phase currents of the first motor and the second motor.

[0012] When the upper arm of the second bridge arm is turned on and the lower arms of the first and fifth bridge arms are turned on, the current sensor collects the sum of the b-phase currents of the first motor and the second motor.

[0013] When the upper arm of the third bridge arm is turned on and the lower arms of the first and second bridge arms are turned on, the current sensor collects the sum of the c-phase currents of the first motor and the second motor.

[0014] Furthermore, the minimum sampling time of the current sensor satisfies:

[0015] Tmin=Ton+Tdb+Trise+Tsr+Tmin+Tcon;

[0016] Where Tmin is the minimum sampling time, Ton is the conduction time of the switching transistor in the five-arm bridge circuit, Tdb is the dead time, Trise is the current rise time, Tsr is the current oscillation time, and Tcon is the AD conversion time.

[0017] Furthermore, the five-arm circuit is controlled by a PWM signal, and within one PWM signal cycle, it has at least a sector boundary region at the high-low level switching point and a low-modulation region where the high level time is less than the threshold time.

[0018] Within the sector boundary region, the current sensor inserts a measurement vector time within the PWM signal cycle each time it samples; within the low modulation region, the current sensor inserts two measurement vector times within the PWM signal cycle each time it samples.

[0019] Furthermore, the measurement vector time satisfies:

[0020] Tdef≧Tmin+Tdb

[0021] Where Tdef is the measurement vector time, Tmin is the minimum sampling time, and Tdb is the dead time.

[0022] Furthermore, an observable region is also included within a PWM signal cycle. The current sensor performs at least two samplings within a PWM signal cycle. Within the observable region, the first sampling time is set to Tsample1 = (T1 + T2) / 2 + Tdelay, and the second sampling time is set to Tsample2 = (T2 + T3) / 2 + Tdelay.

[0023] Where T1, T2, and T3 are the times when the PWM signal is at its rising edge, and Tdelay is the sampling delay time.

[0024] Furthermore, within the sector boundary region, the first sampling time is set to Tsample1 = (T2 + T3) / 2 + Tdelay, and the second sampling time is set to Tsample2 = Tmid + Tdelay.

[0025] Where T1, T2, and T3 are the times when the PWM signal is at its rising edge, Tdelay is the sampling delay time, and Tmin is the minimum sampling time.

[0026] Furthermore, within the low-modulation region, the first sampling time is Tsample1 = (T2 + T3 + Tdef) / 2 + Tdelay;

[0027] Where T1, T2, and T3 are the times when the PWM signal is at its rising edge, Tdef is the measurement vector time, and Tdelay is the sampling delay time.

[0028] The present invention also proposes a refrigeration system having at least two motors and a dual-motor drive system, and further having a current sampling device for the aforementioned dual-motor drive system.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] 1. This invention uses a single current sensor, which is placed on the DC bus between the five-arm circuit and the bus capacitor. In conjunction with the switching state of the five-arm circuit, it can monitor the current of multiple arms or phase lines through a single current sensor.

[0031] 2. This invention can extract multi-phase current information from the signal obtained by a single current sensor, taking into account the phase difference of the current and signal superposition, accurately separating the current value of each phase, and ensuring the accuracy and real-time performance of sampling.

[0032] 3. This invention reduces the number of sensors, and only one current sensor is needed to monitor the current of multiple bridge arms or phase lines, which greatly reduces hardware costs;

[0033] 4. This invention enables current sampling of each motor in a dual-motor drive system, which can be used to ensure coordinated operation between the two motors, thereby improving the overall control accuracy and dynamic response performance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the current sensor setup in a five-arm bridge circuit in the prior art;

[0036] Figure 2 This is a schematic diagram showing the current sensor configuration in the five-arm bridge circuit of this invention.

[0037] Figure 3 This is a schematic diagram of the sector boundary region of the PWM signal in this invention;

[0038] Figure 4 This is a schematic diagram of the low-modulation region of the PWM signal in this invention;

[0039] Figure 5 This is a schematic diagram of SSVPWM control in the sector boundary region of the present invention;

[0040] Figure 6 This is a schematic diagram of SSVPWM control in the low modulation region of the present invention;

[0041] Figure 7 This is a schematic diagram of the sampling time in the observable area of ​​the present invention;

[0042] Figure 8 This is a schematic diagram of the sampling time in the sector boundary region of the present invention;

[0043] Figure 9 This is a schematic diagram of the sampling time in the low-modulation region of the present invention;

[0044] Figure 10 This is a schematic diagram of the control system architecture of the present invention. Detailed Implementation

[0045] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0046] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0047] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0048] Please see Figure 1 Currently, in the five-arm drive scheme, when sampling current, a current sensor needs to be set on each arm, namely current sensor RS1, current sensor RS2, current sensor RS3, current sensor RS4, and current sensor RS5. Although this setting method can realize current sampling of multiple arms and different phase lines, it also increases hardware cost and complexity, and may also lead to signal interference and installation space limitations.

[0049] To address the aforementioned issues, this invention proposes a current sampling device for a dual-motor drive system. The dual-motor drive system includes at least a five-bridge-arm circuit connected to a bus capacitor. The five-bridge-arm circuit drives a first motor and a second motor connected thereto. The current sampling device includes a current sensor disposed on a DC bus between the five-bridge-arm circuit and the bus capacitor. The current sensor acquires the current parameters of the first motor and the second motor by collecting the current parameters of the five-bridge-arm circuit in different switching states.

[0050] Please see Figure 2 The five-arm circuit consists of switching transistors S1, S2, S3, S4, S5, S6, S7, S8, S9, and S10. The first motor is a motor connected to switching transistors S1, S2, S3, S4, S9, and S10. The second motor is a motor connected to switching transistors S5, S6, S7, S8, S9, and S10. The current sensor Rs is located between the bus capacitor Udc and the five-arm circuit.

[0051] As can be seen from the above structure, the current in any bridge arm or phase line will pass through the DC bus. Therefore, by placing the current sensor Rs after the DC bus in this invention, the current flowing through the components can be detected. At the same time, in conjunction with the control of the conduction state of each bridge arm, the monitoring of the current of multiple bridge arms or phase lines can be realized. That is, the current sensor mentioned above obtains the current parameters of the first motor and the second motor by collecting the current parameters of the five bridge arm circuit in different switching states.

[0052] Please see Figure 2 The five-bridge circuit in this invention has a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, and a fifth bridge arm;

[0053] The three-phase windings of the first motor are connected to the midpoints of the first bridge arm, the second bridge arm, and the fifth bridge arm, respectively. The three-phase windings of the second motor are connected to the midpoints of the third bridge arm, the fourth bridge arm, and the fifth bridge arm, respectively.

[0054] In this connection method, the first motor and the second motor can be connected to the five-bridge arm circuit, and the current path can be adjusted by the conduction state of each switch in the five-bridge arm circuit, thereby obtaining the current parameters of different phase lines of the first motor and the second motor.

[0055] Furthermore, the relationship between the conduction state of each switch in the five-bridge arm circuit and the phase current of the first and second motors in this invention can be set as follows:

[0056] The switching states of the first bridge arm and the third bridge arm are kept consistent, and the switching states of the second bridge arm and the fourth bridge arm are kept consistent.

[0057] When the upper arm of the first bridge arm is turned on and the lower arms of the second and fifth bridge arms are turned on, the current sensor collects the sum of the a-phase currents of the first motor and the second motor.

[0058] When the upper arm of the second bridge arm is turned on and the lower arms of the first and fifth bridge arms are turned on, the current sensor collects the sum of the b-phase currents of the first and second motors.

[0059] When the upper arm of the third bridge arm is turned on and the lower arms of the first and second bridge arms are turned on, the current sensor collects the sum of the c-phase currents of the first and second motors.

[0060] Here, the switching states of the first and third bridge arms are kept consistent, and the switching states of the second and fourth bridge arms are kept consistent. This is to ensure that the phase currents of the same phase in the first and second motors are the same. Please refer to [link to relevant documentation]. Figure 2In this invention, phase a of the first motor is connected to the first bridge arm, phase a of the second motor is connected to the third bridge arm, phase b of the first motor is connected to the second bridge arm, and phase b of the second motor is connected to the fourth bridge arm. Therefore, keeping the switching states of the first and third bridge arms consistent, and keeping the switching states of the second and fourth bridge arms consistent, ensures that the phase currents of phases a and b of the first and second motors are the same. In addition, since phase c of the first and second motors is simultaneously connected to the fifth bridge arm, no other adjustment method is required to ensure that the phase currents of phase c of the first and second motors are the same.

[0061] The above settings ensure that the phase currents of the same phases of the first and second motors are the same, which is used to obtain accurate phase currents of the first and second motors in subsequent detection. As mentioned earlier, when the upper arm of the first bridge arm is conducting and the lower arms of the second and fifth bridge arms are conducting, the current sensor collects the sum of the a-phase currents of the first and second motors. When the a-phase currents of the first and second motors are the same, it is only necessary to obtain the current flowing through the DC bus at this time through the current sensor, and then take half of the current value to obtain the a-phase current of the first and second motors. However, by adjusting the conduction state of the five-bridge arm circuit to sample the other phase currents, the total phase currents of the first and second motors can be obtained.

[0062] Specifically, the relationship between the instantaneous current of the DC bus and the phase currents of the first and second motors depends on the switching state of the five-arm circuit. That is, under different basic voltage vectors, the conduction state of the switching transistors is different, resulting in different current paths. Based on the current paths, the relationship between the DC bus current and the phase currents of the first and second motors can be deduced.

[0063] If S n (n = 1, 2, 5) represents the state (S) of the upper and lower switches in the nth bridge arm of the inverter. n =1 indicates that the upper arm of the nth bridge arm is conducting and the lower arm is off; S n =0 indicates that the lower arm of the nth bridge arm is on and the upper arm is off. Then, the relationship between the DC bus current and the motor phase current under different basic voltage vectors can be expressed as i dc =i a S1+i b S2+i c S5, the specific relationships are shown in the table below;

[0064]

[0065] Here, V1 to V6 represent different voltage vectors, and the parentheses contain the conduction state of each bridge arm. For example, (100) is actually S1 = 1, S2 = 0, S5 = 0, which means that the upper arm of the first bridge arm is conducting, the lower arm of the second bridge arm is conducting, and the lower arm of the fifth bridge arm is conducting.

[0066] The reason for describing the conduction status of the first bridge arm, the second bridge arm, and the fifth bridge arm here is that the first bridge arm and the third bridge arm have the same conduction status, and the second bridge arm and the fourth bridge arm have the same conduction status. Therefore, by obtaining the conduction status of the first bridge arm, the second bridge arm, and the fifth bridge arm, the conduction status of all bridge arms can be obtained.

[0067] As mentioned above, the phase currents of the same phase of the first motor and the second motor are the same. The first bridge arm, the second bridge arm, and the fifth bridge arm are respectively connected to phase a, phase b, and phase c of the first motor. They can control the state of phase a, phase b, and phase c of the first motor connected to the five-bridge arm circuit, thereby realizing the detection of the phase current of each phase. The DC bus current detected by the current sensor each time is twice the phase current connected to the first motor (the phase current connected to the second motor is the same as the phase current connected to the first motor, and can be considered as twice the phase current connected to the first motor).

[0068] Therefore, under the basic voltage vector of V1(100), it can be recorded that the DC bus current is twice the a-phase current of the first motor. Based on this, after detection, the accurate magnitude of the phase current of each phase of the first motor and the second motor can be accurately obtained.

[0069] Here, the positive and negative values ​​in the table above represent the direction of current flow. Clockwise is positive and counterclockwise is negative. For example, under the basic voltage vector of V1(100), for the first motor, its current flows into phase a through switch S1, then flows out through phase b and phase c of the first motor respectively, and finally forms a circuit through switch S4 and switch S10. Here, the flow direction from phase a to phase b, phase a to phase c, and phase b to phase c is the clockwise flow direction, which is recorded as positive. Conversely, the flow direction from phase b to phase a, phase c to phase a, and phase c to phase b is the counterclockwise flow direction, which is recorded as negative.

[0070] Based on the above settings, the present invention can monitor the current of multiple bridge arms or phase lines through a single current sensor by adjusting the switching state of the five-arm circuit.

[0071] Furthermore, in order to achieve accurate sampling of current information, the sampling process must be guaranteed in terms of time. The minimum time required to sample accurate current information is defined as the minimum sampling time T. min It can be represented as T min =T on +T db +T rise+T sr +T min +T con ;

[0072] Among them, T on T is the conduction time of the switching transistor in the five-arm bridge circuit. db For dead time, T rise T is the current rise time. sr T is the current oscillation time. con T is the A / D conversion time. min It is not a constant, and its specific value is affected by the performance of the switching devices and the AD conversion chip.

[0073] Seven-segment SVPWM divides the voltage vector into two equal parts, distributed across the first and second half-cycles, thus dispersing the effective vector's duration. Therefore, in actual sampling, the sampling window duration is at most only half of its effective duration. For example... Figure 3 In sector 1, the effective vectors V1 and V2 have durations of t1 / 2 and t2 / 2 in the first and second halves of the cycle, respectively. Therefore, the maximum durations of the two sampling windows are t1 / 2 and t2 / 2, respectively.

[0074] As analyzed above regarding the minimum sampling time, accurate current information can only be obtained when both sampling window durations are greater than the minimum sampling time. Therefore, to reconstruct the three-phase current, the continuous action time of both effective voltages must reach the minimum sampling time. If even one sampling window duration is less than T... min If this happens, the three-phase current cannot be reconfigured. The region where this occurs is called the unobservable region. In actual motor operation, there are two special regions where the above situation occurs.

[0075] When the motor operates in the sector boundary region, the synthesized voltage vector continuously approaches a certain fundamental vector, and the duration of the other voltage vector is gradually compressed. When its continuous duration is compressed to the point where it does not meet the minimum sampling time, sampling fails, resulting in the inability to complete current reconstruction. Therefore, the sector boundary region is an unobservable region. Figure 3 As shown.

[0076] Furthermore, when the motor is operating in the low-modulation region, the duration of both current sampling windows cannot guarantee the minimum sampling time, such as... Figure 4 As shown.

[0077] The above analysis shows that the unobservable regions include sector boundary regions and low-modulation regions. In traditional SVPWM, the three-phase current reconstructed using DC bus sampling technology leads to current reconstruction failure. The key to DC bus current sampling is to eliminate the influence of sector boundary regions and low-modulation regions on current sampling.

[0078] To address the incompatibility between traditional SVPWM and DC bus sampling technology, this patent proposes a DC bus current sampling space vector pulse width modulation (SSVPWM) method by inserting measurement vectors and compensation vectors. This effectively solves the problem that current in unobservable regions cannot be accurately detected. The proposed SSVPWM modulation method enables current sampling and reconstruction under different modulation intensities.

[0079] The specific SSVPWM modulation method is as follows:

[0080] The five-bridge arm circuit is controlled by a PWM signal. Within one PWM signal cycle, it has at least a sector boundary region at the high-low level switching point and a low-modulation region where the high level time is less than the threshold time.

[0081] Within the sector boundary region, the current sensor inserts a measurement vector time within the PWM signal period each time it samples. Within the low modulation region, the current sensor inserts two measurement vector times within the PWM signal period each time it samples.

[0082] The measurement vector time satisfies:

[0083] T def ≧T min +T db

[0084] Among them, T def To measure vector time, T min For the minimum sampling time, T db This refers to the dead zone time.

[0085] Please see Figure 5 Within the sector boundary region, SSVPWM first inserts a measurement vector time into the PWM waveform. To ensure sufficient time for current measurement, the inserted measurement vector time T is... def T should be satisfied def ≧T min +T db =2T db +T on +T rise +T sr +T con In order to avoid changing the duty cycle and symmetry of the original PWM signal, compensation must be performed at both ends of the PWM signal of that phase, according to the principle of compensating only as much as inserted. Specifically, the signal should be shifted forward and backward by T at the points where Sa transitions from low to high and from high to low, respectively. def / 2,

[0086] Please see Figure 6In the low modulation region, the duty cycles of the three-phase PWM signals are relatively close, so accurate current information cannot be sampled during the two non-zero basic voltage vector action times. If the solution of the sector boundary region is used, only one phase can be obtained, and the three-phase current cannot be reconstructed. To solve this problem, the dual measurement vector insertion method is used in the low modulation region, that is, two measurement vector times are inserted in the middle of the PWM cycle.

[0087] Based on the above settings, the present invention can provide sufficient time for current measurement, thereby ensuring accurate sampling of current information. In addition, the above compensation scheme will not change the duty cycle and symmetry of the original PWM signal, and will not affect the original control logic of the motor.

[0088] Since reconstructing the three-phase voltage requires obtaining information from at least two phase currents, the DC bus must be sampled twice within one PWM cycle. Let T1, T2, and T3 be the rising edges of the three-phase PWM, and Tmid be the midpoint of the PWM cycle.

[0089] Please see Figure 7 Taking sector 1 as an example, the observable region is also included within one PWM signal cycle. The current sensor performs at least two samplings within one PWM signal cycle. Within the observable region, the first sampling time is set to T. sample1 = (T1+T2) / 2+T delay The second sampling time is set to T. sample2 = (T2+T3) / 2+T delay ;

[0090] Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... delay This is the sampling delay time.

[0091] Theoretically, the sampling pulse should trigger sampling midway between T1 and T2. However, current stabilization takes time and is affected by the current rise phase and the slew rate of the operational amplifier. To eliminate this influence, a certain delay T needs to be given to the sampling time. delay =T rise +T sr .

[0092] Please see Figure 8 In this invention, the first sampling time is set to T within the unobservable region. sample1 = (T2+T3) / 2+T delay The second sampling time is set to T. sample2 =T mid +T delay ;

[0093] Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... delay T is the sampling delay time. min This is the minimum sampling time.

[0094] Please see Figure 9 In this invention, the first sampling time in the low modulation region is T. sample1 = (T2+T3+T) def ) / 2+T delay ;

[0095] Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... def To measure vector time, T delay This is the sampling delay time.

[0096] The above analysis shows that, within the originally unobservable region, when the voltage vector's action time is less than T... min At that time, obtaining current information by measuring vectors effectively eliminated the influence of unobservable areas.

[0097] Because a single current sensor carries the corresponding phase current in a time-sharing manner, the control system typically requires more than two current samples to reconstruct the phase current. Therefore, a single-current-sensor AC motor control system has multiple foreground tasks, i.e., multiple ISR programs that perform current sampling at different times.

[0098] like Figure 10 As shown, in a typical single-current sensing control system, foreground task 1 is responsible for the first current sampling; foreground task 2 is responsible for the second current sampling; when zero-point drift detection is performed, a third current sampling is also required at an appropriate time when the first or second sampling complements each other. Foreground task 4, i.e., the main ISR, needs to occur after foreground tasks 1, 2, and 3 to perform current reconstruction and error correction, thereby obtaining three-phase current information. In addition, the main ISR also needs to update the current sampling time after the PWM register is updated and before the next PWM control cycle, so as to accurately trigger each current sampling interrupt in the next control cycle.

[0099] In summary, compared with the prior art, the present invention has at least the following beneficial effects:

[0100] 1. This invention uses a single current sensor, which is placed on the DC bus between the five-arm circuit and the bus capacitor. In conjunction with the switching state of the arm circuit, it can monitor the current of multiple arms or phase lines through a single current sensor.

[0101] 2. This invention can extract multi-phase current information from the signal obtained by a single current sensor, taking into account the phase difference of the current and signal superposition, accurately separating the current value of each phase, and ensuring the accuracy and real-time performance of sampling.

[0102] 3. This invention reduces the number of sensors, and only one current sensor is needed to monitor the current of multiple bridge arms or phase lines, which greatly reduces hardware costs;

[0103] 4. This invention enables current sampling of each motor in a dual-motor drive system, which can be used to ensure coordinated operation between the two motors, thereby improving the overall control accuracy and dynamic response performance.

[0104] The present invention also proposes a refrigeration system having at least two motors and a dual-motor drive system, and a current sampling device for the dual-motor drive system.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A current sampling device for a dual-motor drive system, the dual-motor drive system comprising at least a five-bridge circuit connected to a bus capacitor, the five-bridge circuit being used to drive a first motor and a second motor connected thereto, characterized in that, The current sampling device includes a current sensor disposed on the DC bus between the five-arm circuit and the bus capacitor. The current sensor acquires the current parameters of the first motor and the second motor by collecting the current parameters of the five-arm circuit in different switching states.

2. The current sampling device for the dual-motor drive system according to claim 1, characterized in that, The five-arm circuit has a first arm, a second arm, a third arm, a fourth arm, and a fifth arm. The three-phase windings of the first motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm, and the fifth bridge arm, and the three-phase windings of the second motor are respectively connected to the midpoints of the third bridge arm, the fourth bridge arm, and the fifth bridge arm.

3. The current sampling device for the dual-motor drive system according to claim 2, characterized in that, The switching states of the first bridge arm and the third bridge arm are consistent, and the switching states of the second bridge arm and the fourth bridge arm are consistent. When the upper arm of the first bridge arm is turned on and the lower arms of the second and fifth bridge arms are turned on, the current sensor collects the sum of the a-phase currents of the first motor and the second motor. When the upper arm of the second bridge arm is turned on and the lower arms of the first and fifth bridge arms are turned on, the current sensor collects the sum of the b-phase currents of the first motor and the second motor. When the upper arm of the third bridge arm is turned on and the lower arms of the first and second bridge arms are turned on, the current sensor collects the sum of the c-phase currents of the first motor and the second motor.

4. The current sampling device for the dual-motor drive system according to claim 1, characterized in that, The minimum sampling time of the current sensor satisfies: T min =T on +T db +T rise +T sr +T min +T con ; Among them, T min For the minimum sampling time, T on T is the conduction time of the switching transistor in the five-arm bridge circuit. db For dead time, T rise T is the current rise time. sr T is the current oscillation time. con This refers to the A / D conversion time.

5. The current sampling device for a dual-motor drive system according to claim 1, characterized in that, The five-bridge arm circuit is controlled by a PWM signal, and within one PWM signal cycle, it has at least a sector boundary region at the high-low level switching point and a low-modulation region where the high level time is less than the threshold time. Within the sector boundary region, the current sensor inserts a measurement vector time within the PWM signal cycle each time it samples; within the low modulation region, the current sensor inserts two measurement vector times within the PWM signal cycle each time it samples.

6. The current sampling device for a dual-motor drive system according to claim 5, characterized in that, The measurement vector time satisfies: T def ≧T min +T db Among them, T def To measure vector time, T min For the minimum sampling time, T db This refers to the dead zone time.

7. The current sampling device for a dual-motor drive system according to claim 5, characterized in that, The observable region is also included within a PWM signal cycle, and the current sensor performs at least two samplings within a PWM signal cycle. Within this observable region, the first sampling time is set to T. sample1 = (T1+T2) / 2+T delay The second sampling time is set to T. sample2 = (T2+T3) / 2+T delay ; Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... delay This is the sampling delay time.

8. The current sampling device for a dual-motor drive system according to claim 5, characterized in that, Within the sector boundary region, the first sampling time is set to T. sample1 = (T2+T3) / 2+T delay The second sampling time is set to T. sample2 =T mid +T delay ; Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... delay T is the sampling delay time. min This is the minimum sampling time.

9. The current sampling device for a dual-motor drive system according to claim 5, characterized in that, Within the low-modulation region, the first sampling time is T. sample1 = (T2+T3+T) def ) / 2+T delay ; Where T1, T2, and T3 are the moments when the PWM signal is at its rising edge, and T... def To measure vector time, T delay This is the sampling delay time.

10. A refrigeration system comprising at least two motors and a dual-motor drive system, characterized in that, It also includes a current sampling device for the dual-motor drive system as described in any one of claims 1 to 9.

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