CN115276499A - Method and system for estimating natural rotation speed of permanent magnet synchronous fan motor - Google Patents
Method and system for estimating natural rotation speed of permanent magnet synchronous fan motor Download PDFInfo
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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
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
- H02P21/18—Estimation of position or speed
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/004—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids by varying driving speed
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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
- H02P25/022—Synchronous 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
- 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
- H02P27/12—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 pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
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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
- H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
- H02P2207/05—Synchronous machines, e.g. with permanent magnets or DC excitation
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Abstract
The invention discloses a method and a system for estimating the natural rotation speed of a permanent magnet synchronous fan motor, which comprises the following steps: judging whether the motor rotates naturally or not, and if so, inputting a zero voltage vector to a three-phase stator winding of the motor under the natural rotation to generate space vector current; selecting a sampling time point t in the last PWM period of the input zero voltage vector n‑1 Executing the angle obtaining step to obtain a first angle; selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle obtaining step to obtain a second angle; obtaining the instantaneous angular velocity of the rotor according to the rates of change of the first and second angles; will instantaneously change the angular velocityObtaining the average angular velocity of natural rotation after digital low-pass filtering; and judging whether the permanent magnet synchronous fan motor adopts braking or not according to the average angular speed. The invention solves the technical problems that the existing estimation method greatly increases the code amount, occupies more storage space and has larger error.
Description
Technical Field
The invention relates to the technical field of variable frequency fans of air conditioners, in particular to a method and a system for estimating the natural rotation speed of a permanent magnet synchronous fan motor.
Background
In recent years, the frequency conversion technology is widely adopted, so that the motor technology enters an important revolution. Moreover, new requirements are put on the motor due to the consideration of energy crisis and environmental protection. At present, the development of high-efficiency motors is not limited to the simple pursuit of small and light weights in the conventional sense, but is regarded as a global problem. At present, the permanent magnet synchronous motor adopting the high-performance permanent magnet has the advantages of high efficiency, wide adjustable rotating speed range and the like, and is widely applied. Especially in the field of air conditioning and heating ventilation of large-scale users, more and more outdoor fans of air conditioning equipment adopt alternating current permanent magnet synchronous motors to replace traditional asynchronous motors.
However, the permanent magnet synchronous motor has a characteristic that when the controller encounters strong wind in a no-output state, the permanent magnet synchronous motor is operated at a high speed and in a power generation state, so that when the permanent magnet synchronous motor is restarted, a start failure or overcurrent protection is easily generated. Therefore, the initial rotation speed of the permanent magnet synchronous motor needs to be detected to judge whether a headwind state needs to be kept or whether braking is needed, and if braking is needed, which mode needs to be adopted for braking, and the like.
For detecting the initial rotating speed of the permanent magnet synchronous motor, at present, two processing modes are mainly provided. One is that no detection is made, no matter what kind of reverse speed, forced braking is adopted, and the processing mode can not utilize natural wind energy, and even larger over current can be generated to cause unit protection; the other is to adopt a kind of more complex algorithm, the basic principle is to utilize the mathematical model of the permanent magnet synchronous motor and carry out online estimation according to the automatic control technology, and the method is different from the algorithm in normal operation, which is equivalent to that one program needs two sets of complex algorithms, thereby causing the code amount to be greatly increased and occupying more storage space. And the algorithm needs to increase a space voltage vector, so that the braking influence is exerted on the actual rotating speed, and the calculation error is larger.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method and a system for estimating the natural rotation speed of a permanent magnet synchronous fan motor, which solve the technical problems that the code amount is greatly increased, more storage space is occupied and the error is larger in the conventional method for estimating the rotation speed, so that the aims of small influence of braking, high estimation precision of the actual rotation speed and reduction of the storage space of a control chip are fulfilled.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a method for estimating the natural rotation speed of a permanent magnet synchronous fan motor comprises the following steps:
judging whether the permanent magnet synchronous fan motor in the current state rotates naturally or not, if so, after a zero voltage vector is input to a three-phase stator winding of a permanent magnet synchronous fan motor under natural rotation, the three-phase stator winding is prompted to generate space vector current;
selecting a sampling time point t in the last PWM period of the input zero voltage vector n-1 Executing the angle obtaining step to obtain a first angle;
selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle obtaining step to obtain a second angle;
obtaining the instantaneous angular speed of the rotor in natural rotation according to the change rate between the first angle and the second angle;
obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
judging whether the permanent magnet synchronous fan motor is braked or not according to the average angular speed;
the permanent magnet synchronous fan motor comprises a three-phase stator winding and a rotor, wherein the rotor naturally rotates in the downwind direction, the upwind direction or the shutdown direction, and the angle acquisition step comprises the following steps: collecting three-phase current of the three-phase stator winding; obtaining the projection of space vector current generated by the three-phase stator winding on the two-phase static coordinate axis according to the three-phase current; and obtaining an angle between the space vector current and the two stationary coordinate axes, namely a rotation angle, according to the projection on the two stationary coordinate axes.
In a preferred embodiment of the present invention, the method for obtaining the projection of the space vector current on the two stationary coordinate axes includes: using said three-phase current directlyCalculating the space vector current I s Projection i on the alpha axis of a two-phase stationary coordinate system α And projection i of the beta axis β Specifically, as shown in formula 1 and formula 2:
i α ＝i u (formula 1);
wherein i u Sampled values for the U-phase current, i α Is a component on an alpha axis under a two-phase static coordinate system;
wherein i v 、i w Is V, W phase current sample value, i β Is the component on the beta axis in a two-phase stationary coordinate system.
As a preferred embodiment of the present invention, the method for obtaining the first angle and the second angle includes: assuming said space vector current I s The angle with the alpha axis is theta s Then the projection i α And projection i β With said space vector current I s The relationship between them is shown in equations 3 and 4:
i α ＝I s cosθ s (formula 3);
i β ＝I s sinθ s (equation 4);
determining theta by using the formula 3 and the formula 4 s As shown in equation 5:
wherein the first angle and the second angle are respectively time points t n-1 And a point in time t n Lower space vector current I s Angle theta to alpha axis s1 And theta s2 。
In a preferred embodiment of the present invention, the method for obtaining the average angular velocity of the rotor under natural rotation includes: passing through the time point t n-1 And a point in time t n Get a time changeChange value dt through the first angle theta S1 And a second angle theta S2 Obtaining the angle change value d theta s As shown in equations 6 and 7:
dt＝t n -t n-1 (equation 6);
dθ s ＝θ s2 -θ s1 (equation 7);
by said dt and d θ s Obtaining an instantaneous angular velocity of the rotor as shown in equation 8:
then, after digital low-pass filtering Wr is obtained
I.e. to estimate the average angular velocity of the rotor.
As a preferred embodiment of the present invention, the method for inputting a zero voltage vector to the three-phase stator winding includes: starting a three-phase full-bridge inverter to input a zero voltage vector to the three-phase stator winding;
the three-phase full-bridge inverter comprises a first bridge arm, a second bridge arm and a third bridge arm, and when a zero-voltage vector is output, the duty ratios of the first bridge arm, the second bridge arm and the third bridge arm are equal.
As a preferred embodiment of the present invention, when it is determined that the permanent magnet synchronous fan motor in the current state is naturally rotating, it is determined that the permanent magnet synchronous fan motor is naturally rotating in the downwind direction or in the upwind direction, and the determination conditions are as follows: specifying a positive direction along the phase sequence U, V, W, then
More than 0 is downwind and less than 0 is upwind.
As a preferred embodiment of the present invention, when determining whether the permanent magnet synchronous fan motor in the current state is rotating naturally, if not, the angle obtaining step does not need to be executed, and the permanent magnet synchronous fan motor is determined to be in a static state or a micro-motion state without being started in the forward or reverse wind.
As a preferred embodiment of the present invention, the method for determining whether or not to apply braking includes:
when in use
When the brake is needed, the brake is adopted;
when in use
In time, the brake is not needed, and the direct start can be realized;
wherein Wr _ set0 and Wr _ set1 are set braking rotating speeds, the range of Wr _ set0 is more than or equal to 0 and less than or equal to 90rpm, and the range of Wr _ set1 is more than or equal to-90 rpm.
As a preferred embodiment of the present invention, when determining whether or not to apply braking, the method further includes:
when in use
When the rotating speed is not needed to be braked, setting the calculated rotating angle and current value as the initialization value of a closed-loop program, and directly switching to the closed-loop program to operate to a set rotating speed;
when in use
When the system is in use, the upwind deceleration operation is carried out, the calculated rotation angle and current value are set as the initialization values of a closed-loop program, the closed-loop program is directly switched to operate, the set rotation speed is 0, and then the system is normally started to the set rotation speed;
when in use
When the wind is in the strong headwind state, the processing modes are two: the first method is to stop PWM output of the three-phase full-bridge inverter and naturally dissipate heat of a unit by utilizing strong headwind; second, upwind reductionThe method comprises the following steps of (1) running at a high speed, setting the calculated rotation angle and current value as initialization values of a closed-loop program, directly switching to the closed-loop program to run, setting the rotation speed to be 0, and then normally starting to the set rotation speed;
when in use
When the motor is in a static state, a static magnetic field is given to force the permanent magnet synchronous fan motor to be in a static state;
wherein the value range of Wr _ set2 is that Wr _ set3 is less than or equal to-120 rpm of Wr _ set 2; the value range of Wr _ set3 is that Wr _ set3 is less than or equal to-420 rpm.
A system for estimating a natural rotation speed of a permanent magnet synchronous fan motor, comprising:
a rotation determination unit: the system comprises a motor, a motor controller, a three-phase stator winding, a motor controller and a motor controller, wherein the motor controller is used for judging whether a permanent magnet synchronous fan motor in the current state rotates naturally or not, and if yes, after a zero voltage vector is input to the three-phase stator winding of the permanent magnet synchronous fan motor under the natural rotation, the three-phase stator winding is prompted to generate space vector current;
an angle acquisition unit: for selecting a sampling time point t in the last PWM period of the input zero-voltage vector n-1 Executing the angle acquisition step to obtain a first angle; selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle obtaining step to obtain a second angle;
an angular velocity calculation unit: the instantaneous angular speed of the rotor in natural rotation is obtained according to the change rate between the first angle and the second angle; obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
an angular velocity determination unit: the controller is used for judging whether the permanent magnet synchronous fan motor adopts braking or not according to the average angular speed;
the permanent magnet synchronous fan motor comprises a three-phase stator winding and a rotor, wherein the rotor naturally rotates in the downwind direction, the upwind direction or the shutdown direction, and the angle acquisition step comprises the following steps: collecting three-phase current of the three-phase stator winding; obtaining the projection of space vector current generated by the three-phase stator winding on the two-phase static coordinate axis according to the three-phase current; and obtaining an angle between the space vector current and the two stationary coordinate axes, namely a rotation angle, according to the projection on the two stationary coordinate axes.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention does not depend on motor parameters, does not need to consider whether the rotor is in a surface-mounted or built-in structure, and has simple calculation and reliable result;
(2) The invention can greatly reduce the program code amount, reduce the storage space of the control chip and even the cost, and is particularly suitable for the special motor control chip with small storage space and limited resources.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Drawings
FIG. 1 is a step diagram of a method for estimating the natural rotational speed of a PMSM motor according to an embodiment of the present invention;
FIG. 2-is a schematic view of angular velocity estimation of an embodiment of the present invention;
fig. 3-is a schematic diagram of a three-phase full-bridge inverter structure according to an embodiment of the invention.
Detailed Description
The method for estimating the natural rotation speed of the permanent magnet synchronous fan motor, as shown in fig. 1, comprises the following steps:
step S1: judging whether the permanent magnet synchronous fan motor in the current state rotates naturally or not, and if so, inputting a zero voltage vector to a three-phase stator winding of the permanent magnet synchronous fan motor under the natural rotation to promote the three-phase stator winding to generate space vector current;
step S2: selecting a sampling time point t in the last PWM period of the input zero voltage vector n-1 Executing the angle obtaining step to obtain a first angle;
and step S3: selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle obtaining step to obtain a second angle;
and step S4: obtaining the instantaneous angular speed of the rotor in natural rotation according to the change rate between the first angle and the second angle;
step S5: obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
step S6: judging whether the permanent magnet synchronous fan motor is braked or not according to the average angular speed;
wherein, permanent magnetism synchronous fan motor includes three-phase stator winding and rotor, and the rotor produces the natural rotation when following wind, headwind or shutting down, and the angle obtains the step and includes: collecting three-phase current of a three-phase stator winding; obtaining the projection of space vector current generated by a three-phase stator winding on two stationary coordinate axes according to the three-phase current; and obtaining the angle between the space vector current and the two stationary coordinate axes, namely the rotation angle according to the projection on the two stationary coordinate axes.
Further, the zero voltage vector referred by the invention is defined as that the upper bridge switching tube and the lower bridge switching tube of the three-phase inversion full bridge are simultaneously conducted and simultaneously turned off, or the upper bridge switching tube and the lower bridge switching tube are simultaneously turned off and simultaneously turned on.
A permanent magnet synchronous alternating current (PMSM) is a generic name of a motor in which a mechanical rectification action of a brush and a commutator of a dc motor is replaced with a semiconductor rectification action, and the dc motor is a so-called rotating rotor type structure in which a permanent magnet for a magnetic field is mounted on a stator and an armature coil is mounted on a rotor side in principle. In the PMSM, the mechanical rectification function is replaced by the semiconductor rectification function, and therefore, the permanent magnet is provided in the rotor and the armature coil is provided in the stator, thereby forming a rotating magnetic field structure. It can also be understood that the stator side structure of the traditional three-phase asynchronous motor is not changed, and the rotor side replaces the armature coil winding by the permanent magnet device, and a semiconductor rectifying device, namely a frequency converter, is added. The PMSM is not independent of the frequency converter, and the PMSM alone is not self-starting and running.
A fan using a PMSM motor, also called a dc fan, is widely used in a household variable frequency air conditioner due to its low noise, low energy consumption and wide speed control range, and is also very commonly used in a commercial air conditioner, such as a unit machine, a hot air blower, a hot water blower and a multi-split air conditioner. The fan motor function of the air conditioning equipment aims to reasonably radiate heat for the heat exchanger and ensure that the air conditioner operates in the optimal state. If the optimum working state can be ensured, there is no specific requirement on the rotation direction of the fan, so if the natural wind can be used for heat dissipation in strong wind, the electric energy can be further saved, and if the optimum working state of the air conditioner can not be ensured, the air conditioner needs to be started to the set speed along the wind against the strong wind. Therefore, the estimation method can estimate the rotor speed under natural rotation so as to judge whether the air conditioner is in the optimal working state.
In the step S3, as shown in fig. 2, the projection of the space vector current on the two-phase stationary coordinate axes includes: directly obtaining space vector current I by utilizing three-phase current s Projection i on the alpha axis of a two-phase stationary coordinate system α And projection i of the beta axis β Specifically, as shown in formula 1 and formula 2:
i α ＝i u (formula 1);
wherein i u Sampled values for the U-phase current, i α Is a component on an alpha axis under a two-phase static coordinate system;
wherein i v 、i w Is V, W phase current sample value, i β Is the component on the beta axis in a two-phase stationary coordinate system.
In the step S3, as shown in fig. 2, when the first angle and the second angle are obtained, the method includes: assuming space vector current I s At an angle theta to the alpha axis s Then project i α And projection i β And space vector current I s The relationship between them is shown in equations 3 and 4:
i α ＝I s cosθ s (formula 3);
i β ＝I s sinθ s (equation 4);
determining theta by formula 3 and formula 4 s As shown in equation 5:
wherein the first angle and the second angle are respectively time points t n-1 And a point in time t n Lower space vector current I s Angle theta to alpha axis s1 And theta s2 。
In the steps S4 and S5, as shown in fig. 2, when obtaining the average angular velocity of the rotor in the natural rotation, the method includes: passing through the time point t n-1 And a point in time t n Obtaining a time variation dt through a first angle theta S1 And a second angle theta S2 Obtaining the angle change value d theta s As shown in equations 6 and 7:
dt＝t n -t n-1 (equation 6);
dθ s ＝θ s2 -θ s1 (equation 7);
by dt and d θ s The instantaneous angular velocity of the rotor is obtained as shown in equation 8:
then, after digital low-pass filtering Wr is obtained
I.e. the average angular velocity of the rotor is estimated.
From the foregoing, the PMSM motor is a direct current motor of another structural form, and the analyzing and controlling means is equivalent to a direct current motor according to a motor double reaction theory, and establishes a dq axis mathematical model based on a rotating coordinate system, and a voltage equation of the model is as follows:
V d ＝R s I d +sL d I d -ω r L q I q
V q ＝R s I q +sL q I q +ω r L d I d +ω r K e
wherein, V d 、V q Terminal voltage of the machine in dq coordinate system, I d 、I q Is the motor current in dq coordinate system, omega r Is the angular velocity of rotation of the rotor, K e Is the back electromotive force constant.
If the rotational angular velocity of the rotor is calculated by the above-mentioned voltage equation, it is necessary to calculate the rotational angular velocity by applying the three-phase current I in the stationary coordinate system a 、I b 、I c Current I transformed into rotating coordinate system d 、I q Since the angle θ between the d-axis of the rotating coordinate system and the a-axis of the stationary coordinate system cannot be known e So that accurate I cannot be obtained d 、I q . Although a state observer can be constructed and can be deduced through a proper control link, obviously, the calculation amount of the method is large, and the voltage of a non-zero vector must be injected, and the existence of the voltage of the non-zero vector can inhibit the natural rotating speed, so that the deviation of the calculated result is large.
The method provided by the invention is used for estimating the angular velocity omega from a voltage equation under an equivalent two-phase stationary alpha and beta coordinate system r . The method theoretically eliminates the influence of external factors such as a rotor structure, motor parameters and the like, does not need to establish a mathematical model based on a rotating coordinate system for any motor, does not depend on the motor parameters, and is simple and reliable in calculation method.
In the step S1, when a zero voltage vector is input to the three-phase stator windings, the method includes: starting a three-phase full-bridge inverter to input a zero voltage vector to a three-phase stator winding;
the three-phase full-bridge inverter comprises a first bridge arm, a second bridge arm and a third bridge arm, and when a zero-voltage vector is output, the duty ratios of the first bridge arm, the second bridge arm and the third bridge arm are equal.
The invention inputs zero voltage vector to the three-phase stator winding of the motor through the three-phase full-bridge inverter to obtain phase current in a zero voltage vector state so as to reduce the influence on the actual rotating speed to the maximum extent, the method for outputting the zero voltage vector is that the duty ratio of each bridge arm in the given three bridge arms is equal, and the detection duration can be set according to the actual situation.
In the step S1, when the permanent magnet synchronous fan motor in the current state is determined to be rotating naturally, it is determined to be rotating naturally with the wind or rotating naturally with the headwind, and the determination conditions are as follows: specifies a positive direction along the phase sequence U, V, W, then
More than 0 is downwind and less than 0 is upwind.
In the step S1, when determining whether the permanent magnet synchronous fan motor in the current state is rotating naturally, if not, the angle obtaining step does not need to be executed, and it is determined that the permanent magnet synchronous fan motor is in a static state or a micro-motion state without performing forward or reverse wind starting.
In the step S6, when determining whether or not braking is to be performed, the method includes:
when in use
When the brake is needed, the brake is adopted;
when in use
In time, the brake is not needed, and the direct start can be realized;
wherein Wr _ set0 and Wr _ set1 are set braking rotating speeds, the value range of Wr _ set0 is more than or equal to 0 and less than or equal to 90rpm, and the value range of Wr _set1is more than or equal to-90 rpm.
Further, when judging whether to adopt the braking, the method further comprises the following steps:
when in use
In the process, the braking is not needed, and the calculated rotating angle and the current value are set as the beginning of a closed-loop programThe initialization value is directly switched to a closed-loop program to run to a set rotating speed;
when in use
When the system runs in a headwind deceleration mode, the calculated rotating angle and the current value are set as initialization values of a closed-loop program, the closed-loop program is directly switched to run, the set rotating speed is 0, and then the system is normally started to the set rotating speed;
when in use
When the wind is in the strong headwind state, the processing mode is two: the first method is to stop PWM output of the three-phase full-bridge inverter and naturally dissipate heat of a unit by utilizing strong headwind; the second method is to carry out upwind deceleration operation, set the calculated rotation angle and current value as the initialization value of a closed-loop program, directly switch to the closed-loop program operation, set the rotation speed to 0, and then normally start to the set rotation speed;
when in use
When the motor is in a static state, a static magnetic field is given to force the permanent magnet synchronous fan motor to be in a static state;
wherein, the value range of Wr _ set2 is that Wr _ set3 is less than or equal to-120 rpm of Wr _ set 2; the value range of Wr _ set3 is that Wr _ set3 is less than or equal to-420 rpm.
The invention provides a system for estimating the natural rotation speed of a permanent magnet synchronous fan motor, which comprises:
a rotation determination unit: the system is used for judging whether the permanent magnet synchronous fan motor in the current state rotates naturally or not, and if so, after zero voltage vectors are input to a three-phase stator winding of the permanent magnet synchronous fan motor under the natural rotation, the three-phase stator winding is promoted to generate space vector current;
an angle acquisition unit: for selecting a sampling time point t in the last PWM period of the input zero-voltage vector n-1 Executing the angle obtaining step to obtain a first angle; selecting a sampling time point t in the current PWM period of the input zero voltage vector n Angle of executionAn obtaining step of obtaining a second angle;
an angular velocity calculation unit: the instantaneous angular speed of the rotor in natural rotation is obtained according to the change rate between the first angle and the second angle; obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
angular velocity determination unit: the device is used for judging whether the permanent magnet synchronous fan motor adopts braking or not according to the average angular speed;
wherein, permanent magnetism synchronous fan motor includes three-phase stator winding and rotor, and the rotor produces the natural rotation when following wind, contrary wind or shutting down, and the angle obtains the step and includes: collecting three-phase currents of the three-phase stator winding; obtaining the projection of space vector current generated by a three-phase stator winding on two-phase stationary coordinate axes according to the three-phase current; and obtaining an angle between the space vector current and the two stationary coordinate axes, namely a rotation angle according to the projection on the two stationary coordinate axes.
When the air conditioner is stopped, the fan is driven by natural wind to rotate, the inverter does not output at this time, and the rotation speed cannot be detected theoretically because the rotation speed or the position sensor is not provided. The invention adopts a magnetic field directional control mode without a position sensor, a hardware topological structure adopts a voltage type three-phase full-bridge inverter, as shown in figure 3, a precise resistor is respectively arranged on two lower bridge arms of the two phases of the inverter for detecting space vector current generated by a motor, and the space vector current generated by the motor must flow through the precise resistor of the three-phase full-bridge inverter in order to detect upwind rotating speed. The invention inputs zero voltage vector to the three-phase stator winding of the motor and calculates the rotating speed by using the induced current generated by the induced voltage of the stator winding.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention does not depend on motor parameters, does not need to consider whether the rotor is in a surface-mounted or built-in structure, and has simple calculation and reliable result;
(2) The invention can greatly reduce the program code amount, reduce the storage space of the control chip and even the cost, and is particularly suitable for a special motor control chip with small storage space and limited resources.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A method for estimating the natural rotation speed of a permanent magnet synchronous fan motor is characterized by comprising the following steps:
judging whether the permanent magnet synchronous fan motor in the current state rotates naturally or not, and if so, inputting a zero voltage vector to a three-phase stator winding of the permanent magnet synchronous fan motor under the natural rotation to promote the three-phase stator winding to generate a space vector current;
selecting a sampling time point t in the last PWM period of the input zero voltage vector n-1 Executing the angle obtaining step to obtain a first angle;
selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle acquisition step to obtain a second angle;
obtaining the instantaneous angular speed of the rotor in natural rotation according to the change rate between the first angle and the second angle;
obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
judging whether the permanent magnet synchronous fan motor is braked or not according to the average angular speed;
the permanent magnet synchronous fan motor comprises a three-phase stator winding and a rotor, wherein the rotor naturally rotates in the downwind direction, the upwind direction or the shutdown direction, and the angle acquisition step comprises the following steps: collecting three-phase current of the three-phase stator winding; obtaining the projection of space vector current generated by the three-phase stator winding on the two-phase static coordinate axis according to the three-phase current; and obtaining an angle between the space vector current and the two stationary coordinate axes, namely a rotation angle, according to the projection on the two stationary coordinate axes.
2. The method of claim 1, when obtaining the projection of the space vector current on the two stationary coordinate axes, comprising: directly obtaining space vector current I by utilizing the three-phase current s Projection i on the alpha axis of a two-phase stationary coordinate system α And projection of the beta axis i β Specifically, as shown in formula 1 and formula 2:
i α ＝i u (formula 1);
wherein i u Sampled values of the U-phase current, i α Is a component on an alpha axis under a two-phase static coordinate system;
wherein i v 、i w Is V, W phase current sample value, i β Is the component on the beta axis in a two-phase stationary coordinate system.
3. The method of estimating a natural rotational speed of a permanent magnet synchronous fan motor according to claim 2, when obtaining the first angle and the second angle, comprising: assuming said space vector current I s The angle with the alpha axis is theta s Then the projection i α And projection i β With said space vector current I s The relationship between them is shown in equation 3 and equation 4:
i α ＝I s cosθ s (formula 3);
i β ＝I s sinθ s (equation 4);
determining theta by using the formula 3 and the formula 4 s As shown in equation 5:
wherein, theThe first angle and the second angle are respectively time points t n-1 And a point in time t n Lower space vector current I s Angle theta to alpha axis s1 And theta s2 。
4. The method of estimating a natural rotational speed of a permanent magnet synchronous fan motor according to claim 3, when obtaining an average angular speed of the rotor under the natural rotation, comprising: passing through the time point t n-1 And a point in time t n Obtaining a time variation value dt passing through the first angle theta S1 And a second angle theta S2 Obtaining the angle change value d theta s As shown in equations 6 and 7:
dt＝t n -t n-1 (equation 6);
dθ s ＝θ s2 -θ s1 (equation 7);
by said dt and d θ s Obtaining an instantaneous angular velocity of the rotor as shown in equation 8:
then, after digital low-pass filtering Wr is obtained
I.e. the average angular velocity of the rotor is estimated.
5. The method of estimating a natural rotation speed of a permanent magnet synchronous fan motor according to claim 1, when a zero voltage vector is inputted to the three-phase stator winding, comprising: starting a three-phase full-bridge inverter to input a zero voltage vector to the three-phase stator winding;
the three-phase full-bridge inverter comprises a first bridge arm, a second bridge arm and a third bridge arm, and when a zero-voltage vector is output, the duty ratios of the first bridge arm, the second bridge arm and the third bridge arm are equal.
6. The method of claim 1, wherein when the permanent magnet synchronous fan motor in the current state is determined to be naturally rotating, the permanent magnet synchronous fan motor is determined to be naturally rotating in the downwind direction or in the upwind direction, and the determination conditions are as follows: specifies a positive direction along the phase sequence U, V, W, then
More than 0 is downwind and less than 0 is upwind.
7. The method of claim 1, wherein when determining whether the current permanent magnet synchronous fan motor is rotating naturally, if not, the angle obtaining step is not required, and the permanent magnet synchronous fan motor is determined to be in a static or micro-motion state without being started by a forward or reverse wind.
8. The method of estimating a natural rotational speed of a permanent magnet synchronous fan motor according to claim 1, when determining whether or not braking is applied, comprising:
when in use
When the brake is needed, the brake is adopted;
when in use
In time, the brake is not needed, and the direct start can be realized;
wherein Wr _ set0 and Wr _ set1 are set braking rotating speeds, the range of Wr _ set0 is more than or equal to 0 and less than or equal to 90rpm, and the range of Wr _ set1 is more than or equal to-90 rpm.
9. The method of estimating a natural rotational speed of a permanent magnet synchronous fan motor according to claim 8, further comprising, when determining whether to apply braking:
when the temperature is higher than the set temperature
When the rotating speed is not needed to be braked, setting the calculated rotating angle and current value as the initialization value of a closed-loop program, and directly switching to the closed-loop program to operate to a set rotating speed;
when in use
When the system runs in a headwind deceleration mode, the calculated rotating angle and the current value are set as initialization values of a closed-loop program, the closed-loop program is directly switched to run, the set rotating speed is 0, and then the system is normally started to the set rotating speed;
when in use
When the wind is in the strong headwind state, the processing mode is two: the first method is to stop PWM output of the three-phase full-bridge inverter and naturally dissipate heat of a unit by utilizing strong headwind; the second method is to carry out upwind deceleration operation, set the calculated rotation angle and current value as the initialization value of a closed-loop program, directly switch to the closed-loop program operation, set the rotation speed to 0, and then normally start to the set rotation speed;
when the temperature is higher than the set temperature
When the motor is in a static state, a static magnetic field is given to force the permanent magnet synchronous fan motor to be in a static state;
wherein, the value range of Wr _ set2 is Wr _ set3< Wr _ set2 ≤ 120rpm; the value range of Wr _ set3 is that Wr _ set3 is less than or equal to-420 rpm.
10. A system for estimating a natural rotation speed of a permanent magnet synchronous fan motor, comprising:
a rotation determination unit: the system comprises a motor, a motor controller, a three-phase stator winding, a motor controller and a motor controller, wherein the motor controller is used for judging whether a permanent magnet synchronous fan motor in the current state rotates naturally or not, and if yes, after a zero voltage vector is input to the three-phase stator winding of the permanent magnet synchronous fan motor under the natural rotation, the three-phase stator winding is prompted to generate space vector current;
an angle acquisition unit: for selecting a sampling time point t in the last PWM period of the input zero-voltage vector n-1 Executing the angle obtaining step to obtain a first angle; selecting a sampling time point t in the current PWM period of the input zero voltage vector n Executing the angle obtaining step to obtain a second angle;
an angular velocity calculation unit: the instantaneous angular speed of the rotor in natural rotation is obtained according to the change rate between the first angle and the second angle; obtaining the average angular velocity of natural rotation after the instantaneous angular velocity is subjected to digital low-pass filtering;
an angular velocity determination unit: the permanent magnet synchronous fan motor is used for judging whether to adopt braking according to the average angular speed;
the permanent magnet synchronous fan motor comprises a three-phase stator winding and a rotor, wherein the rotor naturally rotates in the downwind direction, the upwind direction or the shutdown direction, and the angle acquisition step comprises the following steps: collecting three-phase current of the three-phase stator winding; obtaining the projection of space vector current generated by the three-phase stator winding on the two-phase static coordinate axis according to the three-phase current; and obtaining an angle between the space vector current and the two stationary coordinate axes, namely a rotation angle, according to the projection on the two stationary coordinate axes.
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