CN104868807A - Active damping method of Buck circuit brushless direct current motor control system - Google Patents

Abstract

The invention disclosed an active damping method of a Buck circuit brushless direct current motor control system. The active damping method can be realized through the following three kinds of modes: a Buck capacitor is connected in parallel with a virtual resistor; a Buck capacitor is connected in series with a virtual resistor; and an inverter bus is connected in series with a virtual resistor. According to the active damping method, a driving system is under rotation speed and current double-closed-loop control, wherein the outer loop is a rotation speed loop which adopts PI adjuster control, and the inner loop is a current loop, wherein the current loop adopts single-period control so that inductive current can better track a given value. When the value of the Buck capacitor is small, the method can increase the damping of the control system, and stabilize the output voltage of a Buck bus fast in a phase converting period, and therefore, motor phase current can fast recover a steady-state value in the phase converting period, and current resonance can be inhibited. A damping effect is realized through the control algorithm of the system, and the damping of the system can be effectively increased under the premise that system loss is not increased, and the resonance of the motor phase current can be suppressed, and the stability of the control system can be improved.

Description

A kind of active damping method of Buck circuit brushless DC motor control system

Technical field

The present invention relates to a kind of active damping method of Buck circuit brushless DC motor control system, 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.In order to reduce the volume of Buck converter, generally when meeting design requirement, reduce the value of inductance and electric capacity as far as possible.

But when Buck electric capacity value is less, appear in brshless DC motor commutation period, the phenomenon of capacitance boost.And at motor commutation period, inductive current thinks constant, be equivalent to current source Buck electric capacity and motor impedance is connected in constant-current source, strong current resonance can be caused when motor impedance is fixed and be less, make electric machine phase current waveform unstable.

Summary of the invention

For the deficiency of above-mentioned background technology, in order to suppress current resonance, improve the stability of system, the present invention proposes a kind of active damping method based on Buck circuit brushless DC motor control system; The method, by the analysis to ssystem transfer function, utilizes the equivalent transformation of control theory, is in fact equivalent to add resistance in the controls, effectively increases the damping of system, inhibit current resonance.

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

An active damping method for Buck circuit brushless DC motor control system, adopts digital signal processor to calculate the feedback signal n of motor speed as motor speed ring in real time _fed, with the motor speed signal n of setting _refsubtract each other and control through pi regulator, obtain rotating speed outer shroud output valve, be set to i _lref, and as the set-point of inner ring; 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, with rotating speed outer shroud output valve i _lrefsubtract each other through one circle control policy control Buck circuit, the control signal that Buck circuit produces is by controlling three-phase inverter to control motor;

Wherein, by electric machine control system respectively Buck bus capacitor parallel virtual resistance, series connection virtual resistance, inverter bus series connection virtual resistance, increase system damping, inhibit the strong system resonance because the parameter of electric machine and Buck circuit parameter do not mate and produce.

The method provides a kind of Buck circuit brushless DC motor control system, specifically comprises power supply, Buck converter, 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 anode of three-phase inverter bus, and the negative pole of Buck converter connects the negative terminal of three-phase inverter bus; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.

The method provides a kind of Buck circuit brushless DC motor control system, and wherein give Buck Capacitance parallel connection virtual resistance, be equivalent to virtual resistance one end and be connected with power cathode, the other end is connected with one end of Buck electric capacity and one end of Buck inductance;

Specifically comprise the following steps:

Step 1, the capacitance voltage u in a control cycle start time sampling Buck converter _cf;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, subtracts each other regulate through pi regulator with the motor speed value of setting, as the output valve of motor speed ring, i.e. the reference value i of current inner loop _lref;

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the u obtained that samples in step 1 _cfbe handled as follows, be first multiplied by the 1/R reciprocal of the virtual resistance needed for this system, then be multiplied by inductive current one circle control transfer function G (s) and obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedas inductive current reference value i _lrefnegative feedback, join inductor current signal reference value i _lrefinput.

By the u obtained that samples in Laplace transformation _cfbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows: $i_{\mathrm{Lsig}\_\mathrm{fed}}\left(s\right)=\frac{1}{R}G\left(s\right)u_{\mathrm{cf}}\left(s\right);$

In formula: i _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

U _cfs () is capacitance voltage value under complex frequency domain;

R is the virtual resistance resistance of Buck Capacitance parallel connection in this control system under complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback value follows set-point, and G (s) is approximately 1.

The method provides a kind of Buck circuit brushless DC motor control system, and wherein give Buck capacitances in series connection virtual resistance, one end of described virtual resistance one end Buck electric capacity is connected, and the other end is connected with one end of Buck inductance; The method comprises the following steps:

Step 1, the capacitance current i in a control cycle start time sampling Buck converter _cf;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, regulates through pi regulator with the motor speed set-point of setting, as the output valve of motor speed ring, i.e. the reference value i of current inner loop _lref;

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the i obtained that samples in step 1 _cfbe handled as follows, be first multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the inverse of impedance of motor one phase be multiplied by inductive current one circle control transfer function G (s), feedback quantity moved on to control signal end, obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedinductive current reference value i is added to as negative feedback _lref.

By the i obtained that samples in pull-type change _cfbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows: $i_{\mathrm{Lsig}\_\mathrm{fed}}\left(s\right)=i_{\mathrm{cf}}\left(s\right)R\frac{1}{r_m+L_{m}s}G\left(s\right);$

In formula, all variablees are all the values under complex frequency domain;

I _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

I _cfs () is capacitance current value under complex frequency domain;

R is the value of the virtual resistance of Buck capacitances in series in this control system under complex frequency domain;

for motor one phase of impedance is at the inverse of complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback amount follows specified rate all the time, and therefore G (s) is approximately 1.

The method provides a kind of Buck circuit brushless DC motor control system, and wherein, to three-phase inverter bus series connection virtual resistance, be equivalent to virtual resistance one end Buck electric capacity and Buck inductance one end is connected, and other end three-phase inverter bus is connected; The method comprises the following steps:

Step 1, at a control cycle start time sampling inverter bus current, in this change ignoring commutation period motor phase of impedance series-parallel system on the impact of damping coefficient, inverter bus current replaces phase current to be designated as i _bus;

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

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the i obtained that samples in step 1 _busbe handled as follows, first be multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the complex frequency domain impedance Cs of Buck electric capacity, be multiplied by inductive current one circle control transfer function G (s), feedback quantity is moved on to control signal end, obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedinductive current reference value i is added to as negative feedback _lref.

By the i obtained that samples in Laplace transformation _busbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows: i _{lsig_fed}(s)=i _bus(s) RCsG (s);

In formula, all variablees are all the values under complex frequency domain

I _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

I _buss () is three-phase inverter bus current under complex frequency domain;

R is the value of the virtual resistance of inverter bus series connection in this control system under complex frequency domain;

Cs is the complex frequency domain impedance of Buck electric capacity under complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback value follows set-point, and G (s) is approximately 1.

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

In order to suppress the resonance characteristic of parallel resonance, improve the stability of system, the simplest method be exactly on capacitor loop series connection or parallel resistance to increase the damping of system, i.e. passive damped method.But the increase of damping resistance, may affect the filtering performance of harmonic wave on the one hand, also seriously can increase system loss on the other hand, reduces system effectiveness.Especially in large-power occasions, damping resistance heating is serious.

The present invention, under the prerequisite not increasing system loss, effectively increases system damping, suppresses system resonance, and improve the stability of control system operation, by Laplace transformation, equivalent transformation is carried out to ssystem transfer function, to control to replace actual damping resistance, realize damping action.

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 electric capacity after equivalence and load circuit figure;

Fig. 4 is the electric machine phase current oscillogram without active damping method;

Fig. 5 is the load circuit figure of capacitive branch damping resistance in parallel;

Fig. 6 is the Buck circuit brshless DC motor current loop control structure chart of capacitive branch parallel resistance;

Fig. 7 is the Buck circuit brshless DC motor electric current loop structural equivalents Structural Transformation figure of capacitive branch parallel resistance;

Fig. 8 is the electric machine phase current oscillogram under Buck capacitive branch parallel virtual resistive method;

Fig. 9 is the load circuit figure of capacitive branch series damping resistor;

Figure 10 is the Buck circuit brshless DC motor current loop control structure chart of capacitive branch series resistance;

Figure 11 is the Buck circuit brshless DC motor electric current loop structural equivalents Structural Transformation figure of capacitive branch series resistance;

Figure 12 is the electric machine phase current oscillogram under Buck capacitive branch series connection virtual resistance method;

Figure 13 is the load circuit figure of inverter bus series damping resistor;

Figure 14 is the Buck circuit brshless DC motor current loop control structure chart of inverter bus series resistance;

Figure 15 is the Buck circuit brshless DC motor electric current loop structural equivalents Structural Transformation figure of inverter bus series resistance;

Figure 16 is the electric machine phase current oscillogram under inverter bus series connection virtual resistance method.

Embodiment

The invention provides a kind of active damping method of Buck circuit brushless DC motor control system, 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:

The active damping method of a kind of Buck circuit brushless DC motor control system provided by the invention, is launch based on the Buck circuit brushless DC motor control system of routine, specifically comprises power supply, Buck converter, 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 anode of three-phase inverter bus, and the negative pole of Buck converter connects the negative terminal of three-phase inverter bus; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.

This method, has three kinds of forms of expression, is illustrated respectively:

As shown in Figure 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.Fig. 3 is system equivalent circuit diagram, and under the control system without active damping method, as shown in Figure 4, phase current creates strong concussion at commutation period to electric machine phase current waveform.

Embodiment 1:Buck Capacitance parallel connection virtual resistance

(1) Fig. 5 be the increase in damping resistance after equivalent circuit diagram.As shown in Figure 5, motor commutation moment inductive current keeps constantly, and can be considered constant-current source, its current value is i _l.Electric capacity C _finductance two ends are connected in parallel on, r with motor phase windings _mfor motor phase resistance, L _mfor motor phase inductance.R is increased virtual resistance resistance, and equivalent parallel is at electric capacity two ends.According to Fig. 5, as follows at complex frequency domain row write circuit equation:

$i_{\mathrm{cf}}\left(s\right).\frac{1}{\mathrm{Cs}}=u_{\mathrm{cf}}\left(s\right)$

i _R(s).R＝u _cf(s)

i _phase(s).(L _ms+r _m)＝u _cf(s)

i _Lfed(s)＝i _cf(s)+i _R(s)+i _phase(s)

In formula, i _cfs () is capacitance current under complex frequency domain;

I _rs () is damping resistance electric current under complex frequency domain;

I _lfeds () is inductive current actual value under complex frequency domain;

R is the resistance with Capacitance parallel connection under complex frequency domain;

U _cfs () is capacitance voltage under complex frequency domain;

I _phases () is electric machine phase current under complex frequency domain;

L _ms () is motor phase inductance under complex frequency domain;

R _mfor motor phase resistance under complex frequency domain;

According to above-mentioned complex frequency domain equation, the Buck circuit brshless DC motor current loop control structure chart of capacitive branch parallel resistance can be made, as shown in Figure 6.

(2) in order to the damping action of virtual resistance is embodied by control algolithm, need the branch road containing damping resistance R to process.Do equivalence change according to control theory, obtain equivalent block diagram as shown in Figure 7.

(3) as shown in Figure 7, this current loop control structural table understands the core concept that the present invention proposes: sampled capacitor voltage u _cf, first by u _cfbe multiplied by 1/R, wherein R is the resistance of virtual resistance, then is multiplied by inductive current one circle control transfer function G (s), namely obtains inductor current signal value of feedback i _{lsig_fed}.This value is as the negative feedback of inductive current reference value.

In order to verify that the active damping method of the virtual resistance shunt capacitance of Buck circuit brushless DC motor control system in this paper is on the impact of current resonance.Fig. 8 is the electric machine phase current oscillogram under the active damping method of virtual resistance shunt capacitance, wherein damping resistance value 0.5 ohm.As can be seen from the figure, due to the existence having virtual resistance, add the damping of system, electric machine phase current resonance obtains and greatly suppresses, and during commutating, electric machine phase current can realize fast and stable.

Embodiment 2:Buck capacitances in series virtual resistance

(1) Fig. 9 be the increase in damping resistance after equivalent circuit diagram.As shown in Figure 9, motor commutation moment inductive current keeps constantly, and can be considered constant-current source, its current value is i _l.Electric capacity C _finductance two ends are connected in parallel on, r with motor phase windings _mfor motor phase resistance, L _mfor motor phase inductance.R is increased virtual resistance resistance, and equivalent series is on capacitive branch.According to Fig. 9, as follows at complex frequency domain row write circuit equation:

$i_{\mathrm{cf}}(R+\frac{1}{\mathrm{Cs}})=u_{\mathrm{cf}}$

i _phase(L _ms+r _m)＝u _cf

i _Lfed＝i _cf+i _phase

In formula, i _cfs () is capacitance current under complex frequency domain;

R is the resistance of complex frequency domain and capacitances in series;

U _cfs () is capacitance voltage under complex frequency domain;

I _phases () is electric machine phase current under complex frequency domain;

I _lfeds () is inductive current actual value under complex frequency domain;

L _ms () is motor phase inductance under complex frequency domain;

R _mfor motor phase resistance under complex frequency domain;

According to above-mentioned complex frequency domain equation, the Buck circuit brshless DC motor current loop control structure chart of capacitive branch series resistance can be made, as shown in Figure 10.Wherein i _lrefcurrent inner loop inductive current reference value, i _lfedit is inductive current actual value.G (s) is the transfer function of inductive current actual value and set-point, and under inductive current monocycle control method, transfer function is approximate can regard 1 as.

(2) as shown in Figure 10,11, this current loop control structural table understands the core concept that the present invention proposes: sample the i obtained _cfbe handled as follows, be first multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the inverse of impedance of motor one phase feedback quantity is moved on to control signal end, obtain inductor current signal offset i _{lsig_fed}.

In order to verify that the active damping method of the virtual resistance series capacitance of Buck circuit brushless DC motor control system in this paper is on the impact of current resonance, Figure 12 is the electric machine phase current oscillogram under the active damping method of virtual resistance series capacitance.Wherein damping resistance value 1 ohm.As can be seen from the figure, due to the existence having virtual resistance, add the damping of system, electric machine phase current resonance obtains and greatly suppresses, and during commutating, electric machine phase current can realize fast and stable.

Embodiment 3: inverter bus series connection virtual resistance

(1) Figure 13 be the increase in damping resistance after equivalent circuit diagram.As shown in figure 13, motor commutation moment inductive current keeps constantly, and can be considered constant-current source, its current value is i _l.Electric capacity C _finductance two ends are connected in parallel on, r with motor phase windings _mfor motor phase resistance, L _mfor motor phase inductance.R is increased virtual resistance resistance, and equivalent series is on inverter bus branch road.According to Figure 13, as follows at complex frequency domain row write circuit equation:

$i_{\mathrm{cf}}(R+\frac{1}{\mathrm{Cs}})=u_{\mathrm{cf}}$

i _bus(L _ms+r _m)＝u _cf

i _Lfed＝i _cf+i _bus

In formula, i _cfs () is capacitance current under complex frequency domain;

R is the resistance of connecting with inverter bus under complex frequency domain;

U _cfs () is capacitance voltage under complex frequency domain;

I _buss () is inverter bus current under complex frequency domain;

I _lfeds () is inductive current actual value under complex frequency domain;

L _ms () is motor phase inductance under complex frequency domain;

R _mfor motor phase resistance under complex frequency domain;

According to above-mentioned complex frequency domain equation, the Buck circuit brshless DC motor current loop control structure chart of capacitive branch series resistance can be made, as shown in figure 14.Wherein i _lrefcurrent inner loop inductive current reference value, i _lfedit is inductor current feedback value.

(2) as shown in figure 15, this current loop control structural table understands the core concept that the present invention proposes: sample the i obtained _busbe handled as follows, be first multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the complex frequency domain impedance Cs of Buck electric capacity, feedback quantity is moved on to control signal end, obtain inductor current signal offset i _{lsig_fed}.

In order to verify that the active damping method of the virtual resistance series capacitance of Buck circuit brushless DC motor control system in this paper is on the impact of current resonance, Figure 16 is the electric machine phase current oscillogram under the active damping method of virtual resistance series capacitance.Wherein damping resistance value 2 ohm.As can be seen from the figure, due to the existence having virtual resistance, add the damping of system, electric machine phase current resonance obtains and greatly suppresses, and during commutating, electric machine phase current can realize fast and stable.

It should be noted that, the phase current of commutation start time impacts, and is because this Buck circuit brushless DC motor control system have chosen caused by small capacitances, not in discussion scope of the present invention and so on.

In sum, the active damping method of Buck circuit brushless DC motor control system proposed by the invention, the effect of damping is realized by the control algolithm of system, under the prerequisite not increasing system loss, effectively add system damping, inhibit the resonance of electric machine phase current, improve the stability of control system.This algorithm can reduce the impact of busbar voltage to electric machine phase current effectively at brshless DC motor commutation period, inhibits electric machine phase current resonance, achieves good control effects.

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 (8)

1. an active damping method for Buck circuit brushless DC motor control system, is characterized in that: adopt digital signal processor to calculate the feedback signal n of motor speed as motor speed ring in real time _fed, with the motor speed signal n of setting _refsubtract each other and control through pi regulator, obtain rotating speed outer shroud output valve, be set to i _lref, and as the set-point of inner ring; 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, with rotating speed outer shroud output valve i _lrefsubtract each other through one circle control policy control Buck circuit, the control signal that Buck circuit produces is by controlling three-phase inverter to control motor;

Wherein, by electric machine control system respectively at Buck bus capacitor parallel virtual resistance, series connection virtual resistance, inverter bus series connection virtual resistance, increase system damping, inhibit the strong system resonance because the parameter of electric machine and Buck circuit parameter do not mate and produce.

2. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 1, it is characterized in that: the method provides a kind of Buck circuit brushless DC motor control system, specifically comprises power supply, Buck converter, 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 anode of three-phase inverter bus, and the negative pole of Buck converter connects the negative terminal of three-phase inverter bus; The mid point of each phase of described three-phase inverter connects on brshless DC motor three-phase.

3. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 2, it is characterized in that: the method provides a kind of Buck circuit brushless DC motor control system, wherein give Buck Capacitance parallel connection virtual resistance, be equivalent to virtual resistance one end to be connected with power cathode, the other end is connected with one end of Buck electric capacity and one end of Buck inductance;

Specifically comprise the following steps:

Step 1, the capacitance voltage u in a control cycle start time sampling Buck converter _cf;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, subtracts each other regulate through pi regulator with the motor speed value of setting, as the output valve of motor speed ring, i.e. the reference value i of current inner loop _lref;

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the u obtained that samples in step 1 _cfbe handled as follows, be first multiplied by the 1/R reciprocal of the virtual resistance needed for this system, then be multiplied by inductive current one circle control transfer function G (s) and obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedas inductive current reference value i _lrefnegative feedback, join inductor current signal reference value i _lrefinput.

4. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 3, is characterized in that: by the u obtained that samples in Laplace transformation _cfbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows:

$i_{\mathrm{Lsig}\_\mathrm{fed}}\left(s\right)=\frac{1}{R}G\left(s\right)u_{\mathrm{cf}}\left(s\right);$

In formula: i _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

U _cfs () is capacitance voltage value under complex frequency domain;

R is the virtual resistance resistance of Buck Capacitance parallel connection in this control system under complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback value follows set-point, and G (s) is approximately 1.

5. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 2, it is characterized in that: the method provides a kind of Buck circuit brushless DC motor control system, wherein give Buck capacitances in series connection virtual resistance, the one end being equivalent to virtual resistance one end Buck electric capacity is connected, and the other end is connected with one end of Buck inductance;

The method comprises the following steps:

Step 1, the capacitance current i in a control cycle start time sampling Buck converter _cf;

Step 2, when brshless DC motor commutation, digital signal processor calculates the feedback of motor speed as motor speed ring in real time, regulates through pi regulator with the motor speed set-point of setting, as the output valve of motor speed ring, i.e. the reference value i of current inner loop _lref;

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the i obtained that samples in step 1 _cfbe handled as follows, be first multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the inverse of impedance of motor one phase be multiplied by inductive current one circle control transfer function G (s), feedback quantity moved on to control signal end, obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedinductive current reference value i is added to as negative feedback _lref.

6. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 5, is characterized in that: by the i obtained that samples in pull-type change _cfbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows:

$i_{\mathrm{Lsig}\_\mathrm{fed}}\left(s\right)=i_{\mathrm{cf}}\left(s\right)R\frac{1}{r_m+L_{m}s}G\left(s\right);$

In formula, all variablees are all the values under complex frequency domain;

I _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

I _cfs () is capacitance current value under complex frequency domain;

R is the value of the virtual resistance of Buck capacitances in series in this control system under complex frequency domain;

for motor one phase of impedance is at the inverse of complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback amount follows specified rate all the time, and therefore G (s) is approximately 1.

7. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 2, it is characterized in that: the method provides a kind of Buck circuit brushless DC motor control system, wherein, to three-phase inverter bus series connection virtual resistance, be equivalent to virtual resistance one end Buck electric capacity and Buck inductance one end is connected, and other end three-phase inverter bus is connected; The method comprises the following steps:

Step 1, at a control cycle start time sampling inverter bus current, in this change ignoring commutation period motor phase of impedance series-parallel system on the impact of damping coefficient, inverter bus current replaces phase current to be designated as i _bus;

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

Step 3, formulates the circuit expressions formula of this control system, and carries out Laplace transformation, draws the current loop control structure of system, and carry out equivalent transformation to this structure according to Laplace transformation;

Step 4, by the i obtained that samples in step 1 _busbe handled as follows, first be multiplied by the resistance R of the virtual resistance needed for this system, then be multiplied by the complex frequency domain impedance Cs of Buck electric capacity, be multiplied by inductive current one circle control transfer function G (s), feedback quantity is moved on to control signal end, obtain inductor current signal value of feedback i _{lsig_fed};

Step 5, by this inductor current signal value of feedback i _lsig-fedinductive current reference value i is added to as negative feedback _lref.

8. the active damping method of a kind of Buck circuit brushless DC motor control system according to claim 7, is characterized in that: by the i obtained that samples in Laplace transformation _busbe converted into inductor current signal value of feedback i _{lsig_fed}, its formula is as follows:

i _{Lsig_fed}(s)＝i _bus(s)RCsG(s)；

In formula, all variablees are all the values under complex frequency domain

I _{lsig_fed}s () is inductor current signal value of feedback under complex frequency domain;

I _buss () is three-phase inverter bus current under complex frequency domain;

R is the value of the virtual resistance of inverter bus series connection in this control system under complex frequency domain;

Cs is the complex frequency domain impedance of Buck electric capacity under complex frequency domain;

G (s) is inductive current one circle control transfer function under complex frequency domain, and under one circle control mode, inductor current feedback value follows set-point, and G (s) is approximately 1.