The ovennodulation control method without three-phase current sensor for permanent magnet synchronous motor
Technical field
The present invention relates to motor control technology field more particularly to permanent magnet synchronous motor bus current acquisition technique field,
Specifically refer to a kind of ovennodulation control method without three-phase current sensor for permanent magnet synchronous motor.
Background technique
Whether stator three-phase current detection accurately has large effect to real electrical machinery control, usually using Hall current
Sensor samples three-phase current, although current sensor is easy to use, precision is higher, higher cost, circuit volume
Greatly.It is more stringent to the limitation of cost in the control of low-power permanent magnet synchronous motor, therefore some methods are in inverter circuit three
A lower bridge arm installs a sampling resistor respectively, although however in this way cost is relatively low, need when zero vector to electricity
Stream is sampled, and is not suitable for the modulator approach without zero vector, and three resistance need biggish PCB (Printed Circuit
Board, printed circuit board) cloth plate suqare and cause certain circuit loss.In order to solve these problems and further decrease into
This, is currently suggested the method using single resistance bus current sampling, then reconstructs stator three-phase current.
Single resistor current sampling is single resistance of only connecting on bus, according to SVPWM (Space Vector Pulse
Width Modulation, space vector pulse width modulation) waveform single resistance is sampled in the different moments of carrier cycle
And phase current reconstruction is carried out to obtain the true value of three-phase current in the carrier cycle according to sampled value.Realize single resistance electricity
Stream sampling mainly needs to solve three key technology points: the pwm signal in unobservable area changes, sampling time point calculates, is high
Current measurement in the case of modulation ratio.The method of single resistance sampling common at present passes through phase shift primarily directed to preceding two o'clock
Method samples the bus current in unobservable region.
Single resistance sampling basic principle, which refers to, only obtains the principle of motor three-phase current using a sampling resistor.The principle
The relationship of the bus current and three-phase current measured on bus is judged using the switch combination relationship of a PWM cycle.With
For VI sector, in the sector, corresponding PWM waveform is as shown in Figure 1.
Rated current inflow is positive in motor, and outflow is negative.When basic voltage vectors are 100, A phase is flowed into, B, C phase
Outflow, bus current size and A phase current are equal in magnitude at this time, contrary;When basic voltage vectors are 101, A, C phase flow
Enter, B phase flows out, and bus current size and B phase current are equal in magnitude at this time, contrary.Therefore, two in 1 PWM cycle
The electric current surveyed in the action time of a basic voltage vectors to bus, which carries out sampling, can be obtained by three-phase current (such as Fig. 1).It is logical
It is often that two basic voltage vectors time points of the left half period of PWM are sampled, third phase current can pass through formula IA+
IB+IC=0 obtains.Certainly, the corresponding relationship of basic voltage vectors and electric current is on condition that the phase difference of voltage and electric current is sufficiently small.
The electric current reconstructing relationship of VI sector is only analyzed above.Table 1 gives each sector Down Highway electric current and each phase electricity
The relationship of stream:
Table 1
Sector |
The bus current of sampling for the first time |
The bus current of second of sampling |
Ⅰ |
IA |
-IC |
Ⅱ |
IB |
-IC |
Ⅲ |
IB |
-IA |
Ⅳ |
IC |
-IA |
Ⅴ |
IC |
-IB |
Ⅵ |
IA |
-IB |
In Fig. 1, ADC (Analog-to-Digital Converter, A/D converter) sampling twice is respectively in T1
It is realized in the T2 period, but if ADC is not enough to sample out in the case where T1 very little or T2 very little, or both all very littles
Bus current is mostly occurred in this case when low modulation ratio, sector borders.Using the principle of random PWM, do not changing
When target voltage vector, go out the enough T1 and T2 time by changing three-phase PWM waveform construction.Specific principle are as follows: when
The time of T1 (time difference for being defaulted as larger phase with interphase) or T2 (time difference for being defaulted as smaller phase with interphase) are not
When sufficient, larger phase is moved to left, and smaller phase moves to left.When modulating relatively low, three-phase PWM waveform should be all close to 50%, this leads to T1
It is not enough to complete the sampling of the ADC in the respective period with the time of T2.In order to realize ADC sample, will be moved to left to compared with sport, it is smaller
Item moves to right, as shown in Fig. 2, target vector does not change after being moved to left and being moved to right.
When being in sector borders, wherein a phase sampling time is longer, and another phase sampling time is shorter, is not enough to
Bus current is sampled out, needs mutually to move this at this time, by taking the first sector borders as an example, as shown in Figure 3.
It is above exactly currently used single resistance bus current sampling principle.
Summary of the invention
The purpose of the present invention is overcoming the above-mentioned prior art, providing one kind can spread not against three-phase electricity
Sensor realizes the mistake without three-phase current sensor for permanent magnet synchronous motor that bus current is correctly acquired when modulation ratio is excessively high
Modulation control method.
To achieve the goals above, of the invention that there is following constitute:
This is used for the ovennodulation control method without three-phase current sensor of permanent magnet synchronous motor, comprising the following steps:
(1) action time T' is calculated according to reference voltage;
(2) judge whether T' is less thanIf it is, continuing step (3), otherwise, B phase is not moved, and A phase moves to left, C phase
It moves to right, wherein TminFor the minimal sampling time of single resistance sampling;
(3) coboundary or lower boundary of the reference voltage close to place sector are judged, if reference voltage is fanned close to place
The coboundary in area is continued step (4), if reference voltage continues step (5) close to the lower boundary of place sector;
(4) it enablesA is failed to agree and moves to boundary, B phase moves to right;
(5) it enablesC phase is moved to right to boundary, B phase moves to left.
Preferably, the step (1) is further comprising the steps of:
(1-1) calculates the action time T of the adjacent two-phase in current sector according to reference voltage1And T2;
(1-2) is according to T1And T2Calculate zero vector action time:
T0=T-T1-T2,
Wherein, T is PWM cycle.
(1-3) sets the minimal sampling time of single resistance sampling as Tmin, action time is that calculating acts on T' according to the following formula
Time:
Using the ovennodulation control method without three-phase current sensor for permanent magnet synchronous motor in the invention,
When reference voltage enters non-observation area, single resistance sampling can be accurately completed, and while modifying reference voltage, three-phase is all
It is moved, the modification amount of reference voltage can be made to reach minimum in this way, there is extensive reference range.
Detailed description of the invention
Fig. 1 is the ADC sampled point and timing diagram of the prior art.
Fig. 2 be the prior art low modulation than when PWM shift waveform diagram.
PWM when Fig. 3 is the sector borders of the prior art shifts waveform diagram.
When Fig. 4 is the ovennodulation of the ovennodulation control method without three-phase current sensor of permanent magnet synchronous motor of the invention
Inactive area schematic diagram.
Fig. 5 is the reference voltage of the ovennodulation control method without three-phase current sensor of permanent magnet synchronous motor of the invention
Waveform diagram close to coboundary.
Fig. 6 is the reference voltage of the ovennodulation control method without three-phase current sensor of permanent magnet synchronous motor of the invention
Close to the waveform diagram of lower boundary.
Fig. 7 is that single resistance of the ovennodulation control method without three-phase current sensor of permanent magnet synchronous motor of the invention is adopted
Sample schematic illustration.
Specific embodiment
It is further to carry out combined with specific embodiments below in order to more clearly describe technology contents of the invention
Description.
In a preferred embodiment, the ovennodulation control without three-phase current sensor for being used for permanent magnet synchronous motor
Method processed, comprising the following steps:
(1) action time T' is calculated according to reference voltage;
(2) judge whether T' is less thanIf it is, continuing step (3), otherwise, B phase is not moved, and A phase moves to left, C phase
It moves to right, wherein TminFor the minimal sampling time of single resistance sampling;
(3) coboundary or lower boundary of the reference voltage close to place sector are judged, if reference voltage is fanned close to place
The coboundary in area is continued step (4), if reference voltage continues step (5) close to the lower boundary of place sector;
(4) it enablesA is failed to agree and moves to boundary, B phase moves to right;
(5) it enablesC phase is moved to right to boundary, B phase moves to left.
In a kind of preferable embodiment, the step (1) is further comprising the steps of:
(1-1) calculates the action time T of the adjacent two-phase in current sector according to reference voltage1And T2;
(1-2) is according to T1And T2Calculate zero vector action time:
T0=T-T1-T2,
Wherein, T is PWM cycle.
(1-3) sets the minimal sampling time of single resistance sampling as Tmin, action time is that calculating acts on T' according to the following formula
Time:
In SVPWM control, required reference voltage is exported, is by decomposing it in sector, by institute
Two unit vector voltages in sector indicate that the difference of each unit vector action time just constitutes size and Orientation difference
Reference voltage, finally according to the length of action time control IGBT (Insulated Gate Bipolar Transistor,
Insulated gate bipolar transistor) turn-on time length, the adjusting of the length of time is calculated by algorithm, i.e., according to reference
What voltage vector calculated.
When ovennodulation, with increasing for modulation ratio, the amplitude of reference voltage vector is gradually increased, and modulated vector is more next
Closer to six effective vectors of unit, zero vector action time shortens, and reference voltage vector enters inactive area, in Fig. 4
Shown in shade, at this moment by the sampling request that the method for simple phase shift is it is impossible to meet electric current reconstructing, i.e., no matter such as
What carries out the demand that minimal sampling time is all not achieved in phase shift.In order to solve this problem, modification reference voltage arrow can be passed through
The method of amount may be implemented, and specifically be analyzed below.
In a kind of specific embodiment, the action time T1 of the adjacent two-phase in current sector is calculated according to reference voltage
And T2, while zero vector action time T0=T-T1-T2.Assuming that the minimal sampling time of single resistance sampling is Tmin, if that
Action time meetsCarrying out phase shift anyway i.e. in the boundary PWM cannot all be had
In the sampling time of effect, at this moment reference voltage is close to sector borders.By taking the first sector as an example, when close to sector coboundary, such as Fig. 5
It is shown;When close to sector lower boundary, as shown in Figure 6.Such as in Fig. 5, A, which fails to agree, moves to boundary, and B phase is moved to right to boundary,
100 sampling time is still less than minimal sampling time T at this timemin, can not effectively be sampled, just need to modify at this time single
The action time of bit vector is adjusted.
By being analyzed above it is found that carrying out phase shift anyway all cannot be guaranteed the time of enough samplings, therefore this patent
The method for proposing modification unit vector action time (i.e. modification reference voltage) is adjusted, in order to minimize modification unit
It is influenced brought by vector action time, needs to guarantee that the difference of modification is small as far as possible.Therefore three-phase is proposed to be moved
The method combined with modification unit vector action time is adjusted, to realize the smallest modification meet demand.Specially work as
When there is the case where Fig. 5, enableA, which fails to agree, simultaneously moves to boundary, and B phase moves to right;When there is the case where Fig. 6, enableC phase is moved to right to boundary simultaneously, and B phase moves to left.The modification of the action time of minimum, this patent can be realized in this way
Bus current list resistance sampling schematic diagram it is as shown in Figure 7.
Using the ovennodulation control method without three-phase current sensor for permanent magnet synchronous motor in the invention,
When reference voltage enters non-observation area, single resistance sampling can be accurately completed, and while modifying reference voltage, three-phase is all
It is moved, the modification amount of reference voltage can be made to reach minimum in this way, be with a wide range of applications.
In this description, the present invention is described with reference to its specific embodiment.But it is clear that can still make
Various modifications and alterations are without departing from the spirit and scope of the invention.Therefore, the description and the appended drawings should be considered as illustrative
And not restrictive.