CN104753414A - Buck circuit brushless direct current motor driving system and control method thereof - Google Patents

Abstract

The invention discloses a Buck circuit brushless direct current motor driving system and a control method of the Buck circuit brushless direct current motor driving system. Constant inductive current can be maintained between a conducting zone and a phase exchanging phase of a brushless direct current motor; the driving system is a rotate-speed current double closed loop control, wherein the outer ring is a rotate speed ring and controlled by a PI adjustor; an inner ring is a current ring and controlled by a single cycle algorithm. The Buck circuit brushless direct current motor driving system and the control method thereof can make the inductive current timely respond the change of Buck sudden unloading in phase exchanging moment of the brushless direct current motor; through detecting the Buck inductive current and the Buck capacitance voltage, constant inductive current is maintained; the method can effectively improve the responding ability of the current inner ring on the load change; therefore, the method has significant meaning.

Description

A kind of Buck circuit BLDCM Drive System and control method thereof

Technical field

The present invention relates to a kind of Buck circuit BLDCM Drive System control method, belong to DC converter-motor-driven field.

Background technology

Brushless DC motor rotor adopts permanent magnetic material excitation, because its volume is little, power density is high, dynamic adaptable is strong, control the features such as easy, has been widely used in the every field of productive life.But the brshless DC motor under traditional various PWM control modes, its speed adjustable range is subject to the restriction of inverter switching device pipe frequency, and high-frequency PWM copped wave can increase switching loss greatly.

Along with the development of power electronic technology, Buck circuits get is applied to the occasion of electric machine speed regulation manyly.Control switch pipe duty ratio just can regulate Buck circuit output voltage, is highly suitable for the occasion that some need variable voltage control, especially more extensive in the application of high-speed electric expreess locomotive field variable voltage control.

When connecing resistive load for traditional Buck circuit, its electric current loop generally adopts PI to control, and in this situation, pi regulator can make electric current loop make good response to load variations.But when Buck circuit connects brshless DC motor load, unloaded suddenly owing to being equivalent to during brshless DC motor commutation at commutation moment Buck, now pi regulator can not make the timely responsive load change of current inner loop, inductive current is caused to fall, could not realize the control objectives of double closed-loop control system, namely current inner loop could not make adjustment to zero load in time.

Summary of the invention

For the deficiency of above-mentioned background technology, the invention provides a kind of Buck circuit BLDCM Drive System and control method thereof, the current reference value that this utilizes der Geschwindigkeitkreis given, the value of feedback of inductive current and the capacitance voltage value sampled, carry out prediction to the switching tube duty ratio in each cycle to distribute, make control system can respond motor commutation moment Buck situation unloaded suddenly in time, keep inductive current constant.

The present invention is for solving the problems of the technologies described above by the following technical solutions:

A kind of Buck circuit BLDCM Drive System control method, the method comprises the following steps:

Step 1, gathers inductive current, the capacitance voltage in Buck converter a control cycle start time, utilizes transducer to detect the position signalling of brushless DC motor rotor, communicates the signals in digital signal processor;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, regulates, as the output valve of motor speed ring with the motor speed set-point of setting through pi regulator;

Step 3, using the set-point of der Geschwindigkeitkreis output valve as electric current loop, utilize one circle control algorithm, according to the difference of this switch periods internal inductance given value of current value and value of feedback, calculate the duty ratio of next control cycle to eliminate the error of this control cycle internal inductance given value of current value and value of feedback.

Further, the one circle control algorithmic formula described in step 3 is specially,

$D_{(k+1)}=\frac{(i_{\mathrm{Lref}\left(k\right)}-i_{\mathrm{Lfed}\left(k\right)}+\frac{u_{\mathrm{cf}\left(k\right)}}{L}T)L}{{\mathrm{Tu}}_{d\left(k\right)}};$

In formula, D _(k+1)be in (k+1) individual control cycle, the duty ratio of switching tube;

I _{lref (k)}for the reference value of a kth control cycle internal inductance electric current, i.e. the output valve of der Geschwindigkeitkreis;

I _{lfed (k)}for in a kth control cycle, the value of feedback of inductive current;

U _{cf (k)}for in a kth control cycle, the magnitude of voltage on electric capacity;

L is the inductance value of Buck circuit;

U _{d (k)}for supply voltage value, be generally considered as steady state value;

T is the time of a control cycle.

A kind of at Buck circuit BLDCM Drive System, this system comprises power supply, Buck converter, brshless DC motor and three-phase inverter;

The positive pole of described power supply connects the forward voltage input of Buck converter, and the negative pole of power supply connects the negative pole of Buck converter;

The forward voltage output of described Buck converter connects the positive pole of inverter, and the negative pole of Buck converter connects the negative pole of three-phase inverter; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.

The present invention adopts above technical scheme compared with prior art, has following technique effect:

The method is when brshless DC motor commutation, utilize the position signalling that digital signal processor detection motor Hall element sends, the position signal of hall sensor detected is sent into digital signal processor inner, digital signal processor is according to next interval inverter switching device pipe on off state of the Hall element signal controlling received, through the switching signal of the PWM mouth output inverter switching tube of digital signal processor, carry out correct commutation.

This drive system is speed and current double closed loop control system, and its outer-loop is der Geschwindigkeitkreis, and digital signal processor calculates the feedback n of motor speed as motor speed ring in real time _fed, with the given n of motor speed of setting _refregulate through pi regulator, given as current inner loop of rotating speed outer shroud output valve, is set to i _lref.Inner ring is electric current loop, and digital signal processor real-time sampling Buck inductive current is as the feedback i of current inner loop _lfed.

In the current inner loop of one circle control, digital signal processor is by detecting this control cycle internal inductance current i of sampling in real time _lfedwith capacitance voltage u _cfutilize one circle control algorithm can according to the difference of this switch periods internal inductance given value of current value and value of feedback, calculate the duty ratio of next switch periods to eliminate the error of this cycle internal inductance given value of current value and value of feedback, make inductor current feedback value real-time tracking set-point, when inductive current set-point is constant, keep inductive current constant.

Real-time detection inductive current and capacitance voltage, by designed one circle control algorithm, make inductive current can respond the situation of motor commutation moment load changing in time; Under solving pi regulator control, PI parameter relies on empirical value to determine the change that can not respond capacitance voltage in time, the duty ratio that the PI caused regulates has been not suitable with the dynamic parameter in motor commutation situation, can not adjust switching tube duty ratio in time to make inductive current constant; Compared with the control algolithms such as other such as variable PI parameter, this algorithm is short and sweet, easily realizes.

Accompanying drawing explanation

Fig. 1 is Buck circuit BLDCM Drive System equivalent circuit diagram;

Fig. 2 is Buck circuit BLDCM Drive System speed and current double closed loop equivalent control block diagram;

Fig. 3 is inductive current operating state oscillogram under monocycle algorithm control mode;

Fig. 4 is Buck circuit BLDCM Drive System block diagram;

Fig. 5 is inductive current simulation waveform figure;

Fig. 6 is inductive current and Buck converter switches signal detail oscillogram.

Embodiment

The invention provides a kind of Buck circuit BLDCM Drive System and control method thereof, for making object of the present invention, clearly, clearly, and the present invention is described in more detail with reference to accompanying drawing examples for technical scheme and effect.Should be appreciated that concrete enforcement described herein is only in order to explain the present invention, is not intended to limit the present invention.

Be described in detail below in conjunction with the technical scheme of accompanying drawing to invention:

As shown in Figure 2, Figure 4 shows, a kind of Buck circuit BLDCM Drive System control method, controls the one circle control algorithm that inductive current is constant, comprises the steps:

(1) during brshless DC motor commutation, utilize the position signalling that digital signal processor detection motor Hall element sends, the position signal of hall sensor detected is sent into digital signal processor inner, digital signal processor is according to next interval inverter switching device pipe on off state of the Hall element signal controlling received, through the switching signal of the PWM mouth output inverter switching tube of digital signal processor, carry out correct commutation.

(2) this drive system is speed and current double closed loop control system, and its outer-loop is der Geschwindigkeitkreis, and digital signal processor calculates the feedback n of motor speed as motor speed ring in real time _fed, with the given n of motor speed of setting _refcontrol through pi regulator, given as current inner loop of rotating speed outer shroud output valve, is set to i _lref.Inner ring is electric current loop, and digital signal processor real-time sampling Buck inductive current is as the feedback i of current inner loop _lfed.

(3) in the current inner loop of one circle control, digital signal processor is by detecting this control cycle start time inductive current of sampling i in real time _lfedwith capacitance voltage u _cfutilize one circle control algorithm can according to the difference of this switch periods internal inductance given value of current value and value of feedback, calculate the duty ratio of next switch periods to eliminate the error of this cycle internal inductance given value of current value and value of feedback, make inductor current feedback value real-time tracking set-point, when inductive current set-point is constant, keep inductive current constant.

The one that the present invention proposes is at Buck circuit BLDCM Drive System, and its equivalent electric circuit as shown in Figure 1, comprises power supply, Buck converter, brshless DC motor and three-phase inverter; The positive pole of above-mentioned power supply connects the forward voltage input of Buck converter, and the negative pole of power supply connects the negative pole of Buck converter; The forward voltage output of above-mentioned Buck converter connects the positive pole of inverter, and the negative pole of Buck converter connects the negative pole of three-phase inverter; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.

As shown in Figure 3, the constant principle of monocycle algorithm control inductive current is as follows:

Suppose that rotating speed outer shroud is i to the output of current inner loop _lref, when invariablenes turning speed, through digital signal processor output current reference value substantially constant.The actual value of inductive current is as the feedback of current inner loop, and this value is set to i _lfed.Assuming that in this control cycle, inductive current does not have actual value not follow the tracks of electric current loop set-point, the error amount Δ i of generation:

As the above analysis, the error amount of inductive current is:

Δi＝i _Lref-i _Lfed(1)

In formula (1):

Δ i is the difference of inductive current reference value and value of feedback;

I _lreffor inductive current reference value;

I _lfedfor inductor current feedback value.

When Buck contactor pipe closes, following formula is had to set up:

$u_d-u_{\mathrm{cf}}=L\frac{\mathrm{di}}{\mathrm{dt}}=L\frac{\mathrm{\Δ}{i}_{L1}}{\mathrm{DT}}---\left(2\right)$

In formula (2):

U _dfor supply voltage;

U _cffor capacitance voltage value;

L is Buck circuit inductance values;

Δ i _l1for switching tube period of contact, inductive current rising value;

D is switching tube duty ratio;

T is the time of a control cycle;

Can obtaining of solution:

$\mathrm{\Δ}{i}_{L1}=\frac{u_d-u_{\mathrm{cf}}}{L}\mathrm{DT}---\left(3\right)$

In formula (3):

Δ i _l1for switching tube period of contact, inductive current rising value;

U _dfor supply voltage;

U _cffor capacitance voltage value;

L is Buck circuit inductance values;

D is switching tube duty ratio;

T is the time of a control cycle.

When in like manner can obtain switch disconnection, inductive current drop-out value is:

$\mathrm{\Δ}{i}_{L2}=\frac{u_{\mathrm{cf}}}{L}(1-D)T---\left(4\right)$

In formula (4):

Δ i _l2for switching tube blocking interval, inductive current drop-out value;

U _cffor capacitance voltage value;

L is Buck circuit inductance values;

D is switching tube duty ratio;

T is the time of a control cycle;

Utilize the difference compensating inductance given value of current value of a switch periods internal inductance electric current rising value and drop-out value and the difference of value of feedback, eliminate the error of electric current loop.

Simultaneous formula (1,2,3)

$i_{\mathrm{Lref}}-i_{\mathrm{Lfed}}=\frac{u_d-u_{\mathrm{cf}}}{L}\mathrm{DT}-\frac{u_{\mathrm{cf}}}{L}(1-D)T---\left(5\right)$

In formula (5):

I _lreffor inductive current reference value;

I _lfedfor inductor current feedback value;

U _dfor supply voltage;

U _cffor capacitance voltage value;

L is Buck circuit inductance values;

D is switching tube duty ratio;

T is the time of a control cycle.

By above formula discretization, the difference of this cycle internal inductance electric current rising value and drop-out value is utilized to go offset current inner loop error value:

$\frac{u_{d\left(k\right)}-u_{\mathrm{cf}\left(k\right)}}{L}{D}_{k+1}T-\frac{u_{\mathrm{cf}}}{L}(1-D_{k+1})T=i_{\mathrm{Lref}\left(k\right)}-i_{\mathrm{Lfed}\left(k\right)}---\left(6\right)$

In formula (6):

U _{d (k)}for supply voltage value, be generally considered as steady state value;

U _{cf (k)}for in a kth control cycle, the magnitude of voltage on electric capacity;

D _(k+1)for in a kth control cycle, the duty ratio of switching tube;

L is Buck circuit inductance values;

T is the time of a control cycle;

I _{lref (k)}for the reference value of a kth control cycle internal inductance electric current, i.e. the output valve of der Geschwindigkeitkreis;

I _{lfed (k)}for in a kth control cycle, the value of feedback of inductive current.

Formula (6) the right represents, the error of kth between switch periods internal inductance given value of current value and value of feedback;

Formula (6) left side represents, in a kth switch periods, and the error between inductive current rising value and drop-out value.

Formula (6) shows, the error utilizing the difference of kth between switch periods internal inductance electric current rising value and drop-out value to make up current inner loop to produce.Calculate the duty ratio of switching tube in (k+1) individual switch periods, shown in (7):

$D_{(k+1)}=\frac{(i_{\mathrm{Lref}\left(k\right)}-i_{\mathrm{Lfed}\left(k\right)}+\frac{u_{\mathrm{cf}\left(k\right)}}{L}T)L}{{\mathrm{Tu}}_{d\left(k\right)}}---\left(7\right)$

In formula (7):

D _(k+1)for in a kth control cycle, the duty ratio of switching tube;

I _{lref (k)}for the reference value of a kth control cycle internal inductance electric current, i.e. the output valve of der Geschwindigkeitkreis;

I _{lfed (k)}for in a kth control cycle, the value of feedback of inductive current;

U _{cf (k)}for in a kth control cycle, the magnitude of voltage on electric capacity;

L is Buck circuit inductance values;

T is the time of a control cycle;

U _{d (k)}for supply voltage value, be generally considered as steady state value.

Formula (7) shows, digital signal processor can detect the actual value of a kth switch periods internal inductance electric current and capacitance voltage in real time, controls next (k+1) switch periods switching tube duty ratio.For the situation of motor commutation moment load changing, show capacitance voltage u _cftransient changing.This algorithm utilizes digital signal processor to capacitance voltage u in a kth switch periods _cfwith inductive current i _lfedcarry out real-time detection, in the dynamic change of motor commutation moment timely responsive load, can distribute the duty ratio of switching tube in (k+1) individual switch periods in time, realize the inductive current i of current inner loop _lfedall the time follow current ring set-point i _lref, when electric current loop given constant, keep electric current loop value of feedback and inductive current constant.

In order to verify that current inner loop one circle control algorithm in this paper is on the impact of the performance of Buck converter brushless DC motor control system, has done following simulating, verifying herein, as shown in Fig. 5 Fig. 6.As can be seen from Figure 5, inductive current can keep stable within all the period of time, still can follow the current reference value of the current inner loop that rotating speed outer shroud exports at commutation period well.As can be seen from Figure 6, the switching tube duty ratio controlled under this algorithm, can consider Buck capacitance boost at commutation period, make switching tube constant conduction when commutation, to make up the trend that inductive current fell in the motor commutation moment, the final inductive current that maintains is stablized within all the period of time.

In sum, inductive current constancy algorithms proposed by the invention has good rapidity and dynamic property, and higher reliability and the scope of application, can adapt to motor load even load and dash forward and unload the situation of impact, significant.

Be understandable that, for those of ordinary skills, can be equal to according to technical scheme of the present invention and inventive concept thereof and replace or change, and all these change or replace the protection range that all should belong to the claim appended by the present invention.

Claims (3)

1. a Buck circuit BLDCM Drive System control method, is characterized in that: the method comprises the following steps:

Step 1, gathers inductive current, the capacitance voltage in Buck converter a control cycle start time, utilizes transducer to detect the position signalling of brushless DC motor rotor, communicates the signals in digital signal processor;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, regulates, as the output valve of motor speed ring with the motor speed set-point of setting through pi regulator;

Step 3, using the set-point of der Geschwindigkeitkreis output valve as electric current loop, utilize one circle control algorithm, according to the difference of this switch periods internal inductance given value of current value and value of feedback, calculate the duty ratio of next control cycle to eliminate the error of this control cycle internal inductance given value of current value and value of feedback.

2. a kind of Buck circuit BLDCM Drive System control method according to claim 1, the one circle control algorithmic formula described in step 3 is specially:

$D_{(k+1)}=\frac{(i_{\mathrm{Lref}\left(k\right)}-i_{\mathrm{Lfed}\left(k\right)}+\frac{u_{\mathrm{cf}\left(k\right)}}{L}T)L}{{\mathrm{Tu}}_{d\left(k\right)}};$

In formula, D _(k+1)be in (k+1) individual control cycle, the duty ratio of switching tube;

I _{lref (k)}for the reference value of a kth control cycle internal inductance electric current, i.e. the output valve of der Geschwindigkeitkreis;

I _{lfed (k)}for in a kth control cycle, the value of feedback of inductive current;

U _{cf (k)}for in a kth control cycle, the magnitude of voltage on electric capacity;

L is the inductance value of Buck circuit;

U _{d (k)}for supply voltage value, be considered as steady state value;

T is the time of a control cycle.

3. a Buck circuit BLDCM Drive System, is characterized in that: this system comprises power supply, Buck converter, brshless DC motor and three-phase inverter;

The positive pole of described power supply connects the positive pole of Buck converter, and the negative pole of power supply connects the negative pole of Buck converter;

The forward voltage output of described Buck converter connects the positive pole of inverter, and the negative pole of Buck converter connects the negative pole of three-phase inverter; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.