CN110784152B - Multiphase switched reluctance motor system and control method thereof - Google Patents
Multiphase switched reluctance motor system and control method thereof Download PDFInfo
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- CN110784152B CN110784152B CN201910963322.9A CN201910963322A CN110784152B CN 110784152 B CN110784152 B CN 110784152B CN 201910963322 A CN201910963322 A CN 201910963322A CN 110784152 B CN110784152 B CN 110784152B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/08—Reluctance motors
- H02P25/092—Converters specially adapted for controlling reluctance motors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/08—Reluctance motors
- H02P25/098—Arrangements for reducing torque ripple
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
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Abstract
The invention discloses a multiphase switch reluctance motor system and a control method thereof, wherein the system comprises a direct current bus current sensor, a position sensor, a multiphase power converter, a multiphase switch reluctance motor and a controller; one end of each direct current bus current sensor is connected with the negative electrode of the direct current bus capacitor and the negative electrode of the direct current power supply, and the other end of each direct current bus current sensor is connected with the emitting electrode of the lower switch tube in each phase of half-bridge conversion circuit in the multiphase power converter. According to the invention, the negative direct current buses of the multiphase power converter are separated, the direct current bus current sensors are arranged on the separated negative direct current buses, the bus current is collected at specific sampling time points of each phase through the direct current bus current sensors, and the winding current of each phase of the multiphase switched reluctance motor can be obtained by only using one direct current bus current sensor, so that the volume and the cost of the system are greatly reduced, the power density and the robustness of the system are improved, and the stability is high.
Description
Technical Field
The invention belongs to the technical field of motor drive control, and particularly relates to a multi-phase switched reluctance motor system and a control method thereof.
Background
The switched reluctance motor has the advantages of high power density, simple structure, low cost, large starting torque, good speed regulation performance and the like, and has wide application prospect in the field of electric automobiles. However, compared with a permanent magnet synchronous motor commonly used in the electric automobile industry, the switched reluctance motor has a simple double salient pole structure, so that the switched reluctance motor has large torque ripple, which also limits the application scenarios of the switched reluctance motor.
In the motor structure, in order to reduce torque ripple of the switched reluctance motor due to the doubly salient pole structure, a structure of a multiphase switched reluctance motor is generally adopted. The increase of the number of phases of the motor not only reduces the torque pulsation of the switched reluctance motor, but also improves the torque output capability and efficiency of the motor.
In terms of a driving control strategy, in order to reduce torque ripple caused by current overshoot when the motor operates at a low speed, the switched reluctance motor is generally controlled by adopting a current chopping control mode, and a driving signal for controlling the power converter is obtained by comparing an actual value and a set value of each phase winding current of the switched reluctance motor. Thus, for a switched reluctance motor system, the motor phase winding current must be sampled in real time during each control cycle. In the traditional switched reluctance motor driving topology, current sensors are directly arranged on each phase winding of the motor and used for respectively detecting the current of each phase winding of the motor, so that the number of the current sensors is the same as the number N of phases of a multi-phase switched reluctance electrode. However, the cost and the volume of the multi-phase switch reluctance motor system are improved by a large number of current sensors, and the stability of the multi-phase switch reluctance motor system is also reduced.
In summary, it is an urgent need to solve the above problems to provide a low-cost multi-phase switched reluctance motor system and a control method thereof.
Disclosure of Invention
The invention aims to provide a multi-phase switched reluctance motor system and a control method thereof, aiming at solving the problem that the cost of the multi-phase switched reluctance motor system is higher due to the large number of current sensors in the prior art.
In order to achieve the above object, an aspect of the present invention provides a multi-phase switched reluctance motor system, including a dc bus current sensor, a position sensor, a multi-phase power converter, a multi-phase switched reluctance motor, and a controller;
each phase winding of the multi-phase switched reluctance motor is respectively connected between an emitter of an upper switch tube and a collector of a lower switch tube of each phase half-bridge power converter in the multi-phase power converter; the lower switch tubes of each phase of half-bridge conversion circuit in the multiphase power converter are respectively connected to a negative direct current bus, a direct current bus current sensor is placed on the negative direct current bus of the multiphase power converter and connected with the multiphase power converter, the output ends of the direct current bus current sensor and the position sensor are connected with the input end of a controller, and the output end of the controller is connected to the multiphase power converter;
the direct current bus current sensor is used for collecting the sum of each phase current of a conduction area in the multiphase power converter, namely bus current;
the position sensor is used for acquiring a rotating speed feedback value and a position feedback value of the switched reluctance motor;
the multiphase power converter is used for providing exciting current for each phase of stator winding of the multiphase switched reluctance motor;
the controller is used for obtaining current feedback values of all phases of windings of the multi-phase switched reluctance motor by controlling and reading the time of the bus current collected by the direct current bus current sensor, and controlling by adopting current chopping based on the winding current feedback values, the rotating speed set values and the rotating speed feedback values and the position feedback values of the switched reluctance motor collected by the position sensor to provide driving signals for a switching tube in the multi-phase power converter.
Further, the multiphase power converter comprises a direct current bus capacitor and a multiphase half-bridge conversion circuit; each phase of half-bridge conversion circuit comprises an upper switch tube and a lower switch tube; the lower diode and the lower switch tube of each phase are respectively connected to the two circuits; one end of each direct current bus current sensor is connected with the negative electrode of the direct current bus capacitor and the negative electrode of the direct current power supply, and the other end of each direct current bus current sensor is connected with the emitting electrode of the lower switch tube in each phase of half-bridge conversion circuit.
More preferably, the dc bus current sensor is a hall current sensor.
The invention provides a control method of a multi-phase switch reluctance motor, which comprises the following steps:
s1, calculating a winding current given value by using a proportional-integral regulator based on the rotating speed given value and a rotating speed feedback value of the switched reluctance motor acquired by the position sensor;
s2, obtaining current feedback values of each phase winding of the multi-phase switch reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor;
and S3, controlling by adopting current chopping based on the given value of the winding current, the feedback value of the winding current and the position feedback value of the switched reluctance motor acquired by the position sensor, and obtaining the driving signal of each switching tube in the multiphase power converter.
Further preferably, the method for obtaining the current feedback value of each phase winding of the multi-phase switched reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor comprises the following steps:
s21, obtaining sampling time points of each phase according to the falling edge of the reference auxiliary pulse in one phase current sampling period;
s22, delaying the multiple frequency multiplication auxiliary pulse signal according to each phase sampling time point to obtain each phase multiple frequency multiplication auxiliary pulse signal, so that only one of each auxiliary pulse signal is at a high level at each sampling point;
s23, respectively inputting each phase multiple frequency auxiliary pulse signal into the lower switch tube of the corresponding half-bridge conversion circuit in the conduction interval of each phase of the multiphase power converter;
and S24, respectively recording the current values acquired by the direct current bus current sensor at each phase sampling time point, namely, the current feedback values of each phase winding of the multi-phase switched reluctance motor.
Further preferably, the duty ratio D of the frequency-multiplied auxiliary pulse signal satisfies:
wherein, TminMinimum time, T, required for a DC bus current sensor to complete a precise sampling and A/D conversionPWMIs the period of the auxiliary pulse signal.
Further preferably, the ratio of the pulse frequency of the frequency-multiplied auxiliary pulse signal to the winding current sampling frequency expected by the controller is equal to the number of phases of the multi-phase switched reluctance motor, and in this case, the multi-phase switched reluctance motor control method is suitable for switched reluctance motors with any number of phases.
Through the technical scheme, compared with the prior art, the invention can obtain the following beneficial effects:
1. the invention provides a multi-phase switch reluctance motor system, which can obtain winding current of each phase of a multi-phase switch reluctance motor by separating a negative direct current bus of a multi-phase power converter, installing a direct current bus current sensor on the separated negative direct current bus and respectively injecting auxiliary pulse signals into a lower switch tube in the multi-phase power converter.
2. The invention provides a control method of a multi-phase switch reluctance motor, which is characterized in that the current of each phase winding of each phase switch reluctance motor is measured by only adopting a direct current bus current sensor, and the current of each phase winding of the multi-phase switch reluctance motor can be obtained by collecting the bus current at a specific sampling time point of each phase by the direct current bus current sensor, so that the volume and the cost of a system are reduced, the power density and the robustness of the system are improved, and the stability is high.
Drawings
FIG. 1 is a schematic diagram of a multi-phase switched reluctance machine system according to the present invention;
FIG. 2 is a schematic diagram of a five-phase power converter according to an embodiment of the present invention;
fig. 3 is a schematic diagram of operating currents of a five-phase switched reluctance motor according to an embodiment of the present invention in a current chopping control mode;
fig. 4 is a schematic diagram of three operation modes of an a-phase half-bridge inverter circuit under current chopping control according to an embodiment of the present invention; fig. 4 (a) is an excitation pattern schematic diagram of an a-phase half-bridge conversion circuit under current chopping control; fig. 4 (b) is a schematic diagram of a freewheeling mode of the a-phase half-bridge inverter circuit under current chopping control; fig. 4 (c) is a schematic diagram of a demagnetization mode of the a-phase half-bridge conversion circuit under the current chopping control;
fig. 5 is a schematic diagram of an auxiliary pulse signal according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further 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 invention and are not intended to limit the invention.
To achieve the above object, in one aspect, the present invention provides a multi-phase switched reluctance motor system, as shown in fig. 1, including a dc bus current sensor, a position sensor, a multi-phase power converter, a multi-phase switched reluctance motor, and a controller;
each phase winding of the multi-phase switched reluctance motor is respectively connected between an emitter of an upper switch tube and a collector of a lower switch tube of each phase half-bridge power converter in the multi-phase power converter; the lower switch tubes of each phase of half-bridge conversion circuit in the multiphase power converter are respectively connected to a negative direct current bus, a direct current bus current sensor is placed on the negative direct current bus of the multiphase power converter and connected with the multiphase power converter, the output ends of the direct current bus current sensor and the position sensor are connected with the input end of a controller, and the output end of the controller is connected to the multiphase power converter;
the direct current bus current sensor is used for collecting the sum of each phase current of a conduction area in the multiphase power converter, namely bus current; preferably, the direct current bus current sensor can be a hall type current sensor, the hall type current sensor has the advantages of small sampling time, high precision and the like, and the sampling time of the hall type current sensor is far shorter than the auxiliary pulse period, so that the duty ratio of the auxiliary pulse can be approximately equivalent to 1, namely, the injection of the auxiliary pulse cannot cause great influence on the normal operation of the motor.
The position sensor is used for acquiring a rotating speed feedback value and a position feedback value of the switched reluctance motor;
the multiphase power converter is used for providing exciting current for each phase of stator winding of the multiphase switched reluctance motor;
the controller is used for obtaining current feedback values of all phases of windings of the multi-phase switched reluctance motor by controlling and reading the time of the bus current collected by the direct current bus current sensor, and controlling by adopting current chopping based on the winding current feedback values, the rotating speed set values and the rotating speed feedback values and the position feedback values of the switched reluctance motor collected by the position sensor to provide driving signals for a switching tube in the multi-phase power converter.
Specifically, the multiphase power converter comprises a direct current bus capacitor and a multiphase half-bridge conversion circuit; each phase of half-bridge conversion circuit comprises an upper switch tube and a lower switch tube; the lower diode and the lower switch tube of each phase are respectively connected to the two circuits; one end of each direct current bus current sensor is connected with the negative electrode of the direct current bus capacitor and the negative electrode of the direct current power supply, and the other end of each direct current bus current sensor is connected with the emitting electrode of the lower switch tube in each half-bridge conversion circuit.
The invention provides a control method of a multi-phase switch reluctance motor, which comprises the following steps:
s1, calculating a winding current given value by using a proportional-integral regulator based on the rotating speed given value and a rotating speed feedback value of the switched reluctance motor acquired by the position sensor;
s2, obtaining current feedback values of each phase winding of the multi-phase switch reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor;
and S3, controlling by adopting current chopping based on the given value of the winding current, the feedback value of the winding current and the position feedback value of the switched reluctance motor acquired by the position sensor, and obtaining the driving signal of each switching tube in the multiphase power converter.
Specifically, the method for obtaining the current feedback value of each phase winding of the multi-phase switched reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor includes the following steps:
s21, obtaining sampling time points of each phase according to the falling edge of the reference auxiliary pulse in one phase current sampling period;
specifically, the reference auxiliary pulse is determined by a driving signal actually input to the switching tube by the controller. The falling edge of the reference auxiliary pulse triggers sampling of the direct current bus current sensor and corresponding A/D conversion, so that the falling edge of the reference auxiliary pulse serves as a sampling time point of each phase in one phase current sampling period.
S22, delaying the multiple frequency multiplication auxiliary pulse signal according to each phase sampling time point to obtain each phase multiple frequency multiplication auxiliary pulse signal, so that only one of each auxiliary pulse signal is at a high level at each sampling point;
specifically, in order not to influence the motor operation, the duty cycle of auxiliary pulse needs as big as possible, but because current sensor's sampling and AD conversion need certain time, in order to guarantee that direct current bus current sensor can accomplish accurate sampling at every sampling point homoenergetic, auxiliary pulse's maximum duty cycle D needs to satisfy:
wherein, TminMinimum time, T, required for a DC bus current sensor to complete a precise sampling and A/D conversionPWMIs the period of the auxiliary pulse signal.
Specifically, the ratio of the pulse frequency of the auxiliary pulse signal to the winding current sampling frequency expected by the controller is equal to the number of phases of the multi-phase switched reluctance motor, and at this time, the multi-phase switched reluctance motor control method is suitable for switched reluctance motors with any number of phases.
Specifically, at each phase sampling time point, only the auxiliary pulse of the current phase is at a high level, and the auxiliary pulses of the other phases are at a low level, that is, at each sampling point, only the lower switching tube of one phase is turned on, and the lower switching tubes of the other phases are turned off, so that the winding current of the switched reluctance motor of each phase can be respectively measured by adopting a direct current bus current sensor.
S23, respectively inputting each phase multiple frequency auxiliary pulse signal into the lower switch tube of the corresponding half-bridge conversion circuit in the conduction interval of each phase of the multiphase power converter;
and S24, respectively recording the current values acquired by the direct current bus current sensor at each phase sampling time point, namely, the current of each phase winding of the multi-phase switched reluctance motor.
To further illustrate the present invention, a multi-phase switched reluctance motor system is provided, which is described in detail with reference to the following embodiments and accompanying drawings:
examples 1,
Taking a five-phase switched reluctance motor system as an example, the five-phase switched reluctance motor system comprises a direct current bus current sensor, a position sensor, a five-phase power converter, a five-phase switched reluctance motor and a controller;
the schematic diagram of the five-phase power converter is shown in fig. 2, and includes a dc power supply UdcThe DC bus capacitor C and the five asymmetric half-bridge conversion circuits; each half-bridge conversion circuit comprises an upper switch tube, a lower switch tube, an upper diode and a lower diode. Each half-bridge conversion circuit corresponds to one phase of the multi-phase switched reluctance motor, and each phase winding of the five-phase switched reluctance motor is connected between an emitter of an upper switch tube and a collector of a lower switch tube of each phase of the half-bridge power converter in the multi-phase power converter. Taking the phase a as an example, the phase a half-bridge conversion circuit includes an upper switching tube S1, a lower switching tube S2, an upper diode D1, and a lower diode D2, wherein the upper switching tube S1 is connected to the lower diode D2, the upper diode D1 is connected to the lower switching tube S2, and the phase a winding of the five-phase switched reluctance motor is connected between the emitter of the upper switching tube S1 and the collector of the lower switching tube S2. And the lower diode and the lower switching tube of each phase are respectively connected to the two circuits. Wherein, the lower switch tube of each phase half-bridge conversion circuit in the five-phase power converter is respectively connected with the negative DC bus, the DC bus current sensor is arranged on the negative DC bus of the multiphase power converter, the DC bus current sensorOne end of the capacitor is connected with a direct current bus capacitor C and is connected to a direct current power supply to the negative electrode; the other end of the DC bus current sensor is respectively connected with the emitter of the lower switching tubes S2, S4, S6, S8 and S10 in the A-E phase half-bridge conversion circuit and is commonly connected to a DC power supply UdcThe negative electrode of (1).
Specifically, the direct current bus current sensor is used for collecting the sum of each phase current in a conduction area in the multiphase power converter, namely bus current; preferably, the direct current bus current sensor can be a hall type current sensor, the hall type current sensor has the advantages of small sampling time, high precision and the like, and the sampling time of the hall type current sensor is far shorter than the auxiliary pulse period, so that the duty ratio of the auxiliary pulse can be approximately equivalent to 1, namely, the injection of the auxiliary pulse cannot cause great influence on the normal operation of the motor.
The position sensor is used for acquiring a rotating speed feedback value and a position feedback value of the switched reluctance motor;
the five-phase power converter is used for providing exciting current for each phase of stator winding of the five-phase switched reluctance motor;
the controller is used for obtaining current feedback values of all phases of windings of the five-phase switched reluctance motor by controlling and reading the time of the bus current collected by the direct current bus current sensor, and controlling by adopting current chopping based on the winding current feedback values, the rotating speed set values and the rotating speed feedback values and the position feedback values of the switched reluctance motor collected by the position sensor to provide driving signals for a switching tube in the multiphase power converter.
Specifically, in order to reduce torque ripple caused by current overshoot, in the present embodiment, the controller employs a current chopping control scheme. Fig. 3 shows a schematic diagram of operating currents of a five-phase switched reluctance motor in a current chopping control mode. Wherein, the horizontal axis represents time value, the vertical axis represents current value collected by the DC bus current sensor, and current Ia～IeThe current values collected by the DC bus current sensor in the area I are the A-phase winding current, the D-phase winding current,And E phase winding current superposition. In the area II, the current value acquired by the direct current bus current sensor is the superposition of the A-phase winding current and the E-phase winding current. In the area III, the current value acquired by the direct current bus current sensor is the superposition of the A-phase winding current, the B-phase winding current and the E-phase winding current. In the area IV, the current value acquired by the direct current bus current sensor is the superposition of the A-phase winding current and the B-phase winding current. In the area V, the current value acquired by the direct current bus current sensor is the superposition of the B-phase winding current, the C-phase winding current and the D-phase winding current. The area II and the area IV are the overlapping of two-phase current in a conduction interval, and the area I, the area III and the area V are the overlapping of three-phase current in the conduction interval. It can be seen that during operation of a five-phase switched reluctance motor, both two-phase current overlap and three-phase current overlap may occur. The direct current bus current sensor mounted on the negative direct current bus detects the sum of the currents of the phase windings in the conduction interval.
Specifically, the control method of the five-phase switched reluctance motor includes the following steps:
s1, calculating a winding current given value by using a proportional-integral regulator based on the rotating speed given value and a rotating speed feedback value of the switched reluctance motor acquired by the position sensor;
s2, obtaining current feedback values of each phase winding of the five-phase switched reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor;
and S3, controlling by adopting current chopping based on the given value of the winding current, the feedback value of the winding current and the position feedback value of the switched reluctance motor acquired by the position sensor, and obtaining the driving signal of each switching tube in the five-phase power converter.
In the process of controlling the switched reluctance motor by adopting a current chopping control mode, the actual value and the given value of the current of each phase winding of the switched reluctance motor need to be compared, so that a driving signal for controlling the power converter is obtained. Therefore, in each control period, the current of each phase winding of the switched reluctance motor must be acquired in real time. In order to obtain the phase winding currents, it is necessary to make the bus current collected by the dc bus current sensor at each sampling time include only one phase winding current.
Specifically, taking an a-phase half-bridge conversion circuit as an example, three operation modes of current chopping control are respectively shown in fig. 4, where (a) in fig. 4 is an excitation mode, in which two switching tubes in the asymmetric half-bridge converter corresponding to a are both turned on, and the winding L is wound onAThe voltage at both ends is equal to the positive voltage UdcAnd the A-phase winding current flows through the direct current bus current sensor. Fig. 4 (b) shows a freewheel mode in which the upper switch S1 of the a-phase half-bridge inverter circuit is turned off, the lower switch S2 is turned on, and the winding L is turned onAThe voltage at the two ends is equal to zero, and the A-phase winding current flows through the direct current bus current sensor. Fig. 4 (c) shows a demagnetization mode, in which the upper and lower switching tubes in the a-phase half-bridge inverter circuit are both turned off and the winding L is woundAThe voltage across is equal to the negative voltage-UdcAnd the A-phase current does not flow through the direct current bus current sensor. Thus, the current i flowing through the DC bus current sensordcCan be expressed as follows:
idc＝iaSa-+ibSb-+icSc-+idSd-+ieSe-
wherein ia、ib、ic、id、ieRespectively represent the A-E phase winding currents, Sa-、Sb-、Sc-、Sd-、Se-Respectively representing the driving signals of the lower switch tube in the A-E phase half-bridge conversion circuit. When the driving signal is 1, the corresponding switch tube is conducted; when the driving signal is 0, the corresponding switch tube is turned off. Therefore, if the two-phase currents overlap, as shown in fig. 3, which is a region II, the current flowing through the dc bus current sensor is the sum of the a-phase current and the E-phase current. When the A-phase lower tube is switched off, the current of the direct-current bus current sensor is the current of the E-phase winding; when the E-phase lower tube is turned off, the current of the direct current bus current sensor is the A-phase winding current. By using the same analysis idea, when three-phase currents are overlapped, the three-phase currents are plottedRegion I in 3 is an example, and in this region, the current flowing through the dc bus current sensor is the sum of the a-phase, D-phase, and E-phase currents. When the A-phase lower tube and the D-phase lower tube are simultaneously turned off, the current of the direct current bus current sensor is the current of the E-phase winding; when the A-phase lower tube and the E-phase lower tube are simultaneously turned off, the current of the direct current bus current sensor is the D-phase winding current; when the D-phase lower tube and the E-phase lower tube are simultaneously turned off, the current of the direct current bus current sensor is the A-phase winding current.
Based on the above analysis, the method for obtaining the current feedback value of each phase winding of the five-phase switched reluctance motor by controlling and reading the time of the bus current acquired by the direct current bus current sensor in the step S2 includes the following steps:
s21, obtaining sampling time points of each phase according to the falling edge of the reference auxiliary pulse in one phase current sampling period;
specifically, the reference auxiliary pulse is determined by a driving signal actually input to the switching tube by the controller.
S22, delaying the multiple frequency multiplication auxiliary pulse signal according to each phase sampling time point to obtain each phase multiple frequency multiplication auxiliary pulse signal, so that only one of each auxiliary pulse signal is at a high level at each sampling point;
specifically, the duty ratio D of the multiple frequency auxiliary pulse signal may be represented as:
wherein, tonAnd toffRespectively the duration of the high and low level in one auxiliary pulse period. The frequency and duty cycle of the injected auxiliary pulse should be large enough to ensure accuracy of the current sampling.
In order not to influence the motor operation, the duty cycle of auxiliary pulse needs as big as possible, but because sampling and the A/D conversion of current sensor need certain time, in order to guarantee that direct current bus current sensor can accomplish accurate sampling at every sampling point, the duty cycle D of auxiliary pulse needs to satisfy:
wherein, TminMinimum time, T, required for a DC bus current sensor to complete a precise sampling and A/D conversionPWMIs the period of the auxiliary pulse signal.
Wherein, the ratio of the pulse frequency of the auxiliary pulse signal to the winding current sampling frequency expected by the controller is equal to the number of phases 5 of the multi-phase switched reluctance motor.
S23, respectively inputting each phase multiple frequency auxiliary pulse signal into the lower switch tube of the corresponding half-bridge conversion circuit in the conduction interval of each phase of the multiphase power converter;
and S24, respectively recording the current values acquired by the direct current bus current sensor at each phase sampling time point, namely, the current of each phase winding of the multi-phase switched reluctance motor.
Specifically, the schematic diagram of the auxiliary pulse signal is shown in fig. 5, in which the falling edge of the reference auxiliary pulse triggers sampling of the dc bus current sensor and corresponding a/D conversion, so T1, T2, T3, T4, and T5 are five current sampling points in one phase current sampling period, respectively. The A, B, C, D, E-phase auxiliary pulses are respectively auxiliary pulse signals injected into a lower switch tube of the A, B, C, D, E-phase half-bridge conversion circuit, and the frequency of the auxiliary pulse signals is five times of the phase current sampling frequency. At each sampling point, at each phase sampling time point, only the auxiliary pulse of the current phase is at a high level, and the auxiliary pulses of the other phases are at a low level, namely, at each sampling point, only the lower switch tube of one phase is switched on, the lower switch tubes of the other phases are switched off, and at the moment, the current value acquired by the direct current bus current sensor is the phase winding current switched on by the lower switch tube at the moment. At each sampling point, the corresponding relationship between the sampling value of the dc bus current sensor and each phase current is shown in table 1. Sampling is carried out on five current sampling points of T1, T2, T3, T4 and T5 respectively, and the five-phase winding current can be obtained according to the corresponding relation in the table 1.
TABLE 1
The invention provides a multiphase switched reluctance motor system and a control method thereof, which can obtain winding current of each phase of a multiphase switched reluctance motor by separating a negative direct current bus of a multiphase power converter, installing a direct current bus current sensor on the separated negative direct current bus and collecting the bus current at a specific sampling time point of each phase through the direct current bus current sensor.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A multi-phase switch reluctance motor system is characterized by comprising a direct current bus current sensor, a position sensor, a multi-phase power converter, a multi-phase switch reluctance motor and a controller;
each phase winding of the multi-phase switched reluctance motor is respectively connected between an emitter of an upper switch tube and a collector of a lower switch tube of each phase half-bridge power converter in the multi-phase power converter; the lower switch tube of each phase of half-bridge conversion circuit in the multiphase power converter is respectively connected to a negative direct current bus, the direct current bus current sensor is placed on the negative direct current bus of the multiphase power converter and connected with the multiphase power converter, the output ends of the direct current bus current sensor and the position sensor are connected with the input end of the controller, and the output end of the controller is connected to the multiphase power converter;
the direct current bus current sensor is used for collecting the sum of each phase current of a conduction area in the multiphase power converter, namely bus current;
the position sensor is used for acquiring a rotating speed feedback value and a position feedback value of the switched reluctance motor;
the multiphase power converter is used for providing exciting current for each phase of stator winding of the multiphase switched reluctance motor;
the controller is used for obtaining current feedback values of each phase winding of the multi-phase switched reluctance motor by controlling and reading the sampling time point of the bus current acquired by the direct current bus current sensor, and controlling by adopting current chopping based on the winding current feedback values, the rotating speed set value and the rotating speed feedback values and the position feedback values of the switched reluctance motor acquired by the position sensor to provide driving signals for a switching tube in the multi-phase power converter;
the method for obtaining the current feedback value of each phase winding of the multi-phase switched reluctance motor comprises the following steps:
s21, obtaining sampling time points of each phase according to the falling edge of the reference auxiliary pulse in one phase current sampling period; the reference auxiliary pulse is determined by a driving signal actually input to a switching tube by the controller; the falling edge of the reference auxiliary pulse triggers the sampling of the direct current bus current sensor and the corresponding A/D conversion;
s22, obtaining each phase multiple frequency auxiliary pulse signal according to each phase sampling time point and the reference auxiliary pulse; in a phase current sampling period, only one of the multiple frequency multiplication auxiliary pulse signals of each phase is at a high level at each sampling point; the method for obtaining the ith-phase multiple frequency auxiliary pulse signal comprises the following steps: in a phase current sampling period, converting a low level of a reference auxiliary pulse in a time period from a falling edge to a next rising edge at an ith phase sampling time point into a high level to obtain an ith phase frequency multiplication auxiliary pulse signal; 1,2, …, N; n is the number of phases of the multi-phase switched reluctance motor;
the duty ratio D of each phase of the multi-frequency multiplication auxiliary pulse signal meets the following requirements:
wherein, TminMinimum time, T, required for a DC bus current sensor to complete a precise sampling and A/D conversionPWMIs the period of the reference auxiliary pulse signal;
s23, respectively inputting each phase multiple frequency auxiliary pulse signal into the lower switch tube of the corresponding half-bridge conversion circuit in the conduction interval of each phase of the multiphase power converter;
and S24, respectively recording the current values acquired by the direct current bus current sensor at each phase sampling time point, namely, the current feedback values of each phase winding of the multi-phase switched reluctance motor.
2. The multiphase switched reluctance motor system of claim 1 wherein the multiphase power converter comprises a dc bus capacitor and a multiphase half bridge converter circuit; each phase of half-bridge conversion circuit comprises an upper switch tube, a lower switch tube, an upper diode and a lower diode; the lower diode and the lower switch tube of each phase are respectively connected to the two circuits; one end of each direct current bus current sensor is connected with the negative electrode of the direct current bus capacitor and the negative electrode of the direct current power supply, and the other end of each direct current bus current sensor is connected with the emitting electrode of the lower switch tube in each phase of half-bridge conversion circuit.
3. The poly-phase switched reluctance motor system according to claim 1, wherein the dc bus current sensor is a hall type current sensor.
4. A method of controlling a polyphase switched reluctance machine system according to any one of claims 1 to 3 comprising the steps of:
s1, calculating a winding current given value by using a proportional-integral regulator based on the rotating speed given value and a rotating speed feedback value of the switched reluctance motor acquired by the position sensor;
s2, obtaining current feedback values of each phase winding of the multi-phase switch reluctance motor by controlling and reading the sampling time point of the bus current acquired by the direct current bus current sensor; the method specifically comprises the following steps:
s21, obtaining sampling time points of each phase according to the falling edge of the reference auxiliary pulse in one phase current sampling period;
s22, obtaining each phase multiple frequency auxiliary pulse signal according to each phase sampling time point and the reference auxiliary pulse; in a phase current sampling period, only one of the multiple frequency multiplication auxiliary pulse signals of each phase is at a high level at each sampling point; the method for obtaining the ith-phase multiple frequency auxiliary pulse signal comprises the following steps: in a phase current sampling period, converting a low level of a reference auxiliary pulse in a time period from a falling edge to a next rising edge at an ith phase sampling time point into a high level to obtain an ith phase frequency multiplication auxiliary pulse signal; 1,2, …, N; n is the number of phases of the multi-phase switched reluctance motor;
the duty ratio D of each phase of the multi-frequency multiplication auxiliary pulse signal meets the following requirements:
wherein, TminMinimum time, T, required for a DC bus current sensor to complete a precise sampling and A/D conversionPWMIs the period of the reference auxiliary pulse signal;
s23, respectively inputting each phase multiple frequency auxiliary pulse signal into the lower switch tube of the corresponding half-bridge conversion circuit in the conduction interval of each phase of the multiphase power converter;
s24, respectively recording current values acquired by the direct current bus current sensor at each phase sampling time point, namely current feedback values of each phase winding of the multi-phase switched reluctance motor;
and S3, controlling by adopting current chopping based on the given value of the winding current, the feedback value of the winding current and the position feedback value of the switched reluctance motor acquired by the position sensor, and obtaining the driving signal of each switching tube in the multiphase power converter.
5. The method of claim 4, wherein the ratio of the pulse frequency of each phase of the multiple frequency auxiliary pulse signal to the winding current sampling frequency expected by the controller is equal to the number of phases of the multiple phase switched reluctance motor.
6. The method of claim 5, wherein the method is applicable to any number of phases of the switched reluctance motor.
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