CN104022716A - Method for controlling maximum torque current ratio of excitation-variation synchronous motor through coefficient fitting - Google Patents

Abstract

The invention relates to a method for controlling the maximum torque current ratio of an excitation-variation synchronous motor through coefficient fitting. Discretization is conducted on excitation flux linkages according to the variation range of an excitation current; under the condition that each specific excitation flux linkage is fixed, only an electromagnetic torque serves as a variable to conduct rectangular axis current functional fitting, and therefore a plurality of fitting curves under the condition that the excitation flux linkages vary are obtained. In the process of system operation, according to the sizes of the excitation flux linkages at different periods, the fitting curves closest to the corresponding excitation flux linkages are selected to conduct calculation of rectangular axis currents, set values of the rectangular shaft currents at different times can be obtained, and finally MTPA control over the excitation-variation synchronous motor is finally achieved.

Description

The change excitation magnetic synchronization motor maximum torque per ampere control method of Coefficient Fitting

Technical field

The invention belongs to the control method field of motor, be specifically related to a kind of change excitation magnetic synchronization motor maximum torque per ampere control method of Coefficient Fitting, the control strategy that the synchronous machine changing for exciting current proposes, by adopting Coefficient Fitting Methods to realize the method that breakdown torque current ratio (MTPA) is controlled, belong to alternating current machine drive technology field.

Background technology

Nowadays large aircraft develops very rapidly, exchanges aviation power system and has occupied more and more consequence.And at present, exchange aviation power system and mainly adopt the generator of three grades of formula brushless synchronous machines as system, engine adopts in addition independently starter to start, and such starting-generating integrated system is comparatively complicated, and volume and weight is larger.But make original three grades of formula brushless synchronous machines complete starting by control method, can realize starting-generating integration.So just can save original starter, reduce integrated machine and load with load.But, when this design of electrical motor, be mainly and meet electricity generate function, while being operated in motoring condition, but there are the following problems: (1) is when a machine is during in static or low-speed running, due to lower exciter output voltage and less main generator excitation electric current, the loaded starting ability of main generator has been received impact; (2) main generator excitation electric current in motor starting process always in change among, this be due to exciter output voltage along with the rising of motor speed gradually increase, caused main generator excitation electric current also gradually increase.

Single from electric machine structure, main generator is electric field excitation salient pole synchronous machine.Adopt MTPA control strategy can significantly improve the load capacity of main generator in the time of static and low speed.For electric excitation synchronous motor or the permagnetic synchronous motor of permanent excitation, its exciting current or excitation flux linkage are to keep constant, according to electromagnetic torque equation T _e=n _p(ψ _di _q-ψ _qi _d)=n _p[ψ _fi _q+ (L _d-L _q) i _di _q], wherein n _pfor the number of pole-pairs of motor, ψ _d, ψ _qbe respectively d-axis magnetic linkage, quadrature axis magnetic linkage, i _d, i _qbe respectively stator direct-axis current, stator quadrature axis electric current, L _d, L _q-stator d-axis, quadrature axis inductance; ψ _ffor steady state value, therefore to meet exactly following planning for the electric excitation synchronous motor of permanent excitation or the MTPA of permagnetic synchronous motor control, to try to achieve the reference value of rectangular axis electric current:

$\left\{\begin{array}{c}\min ={i_d}^2+{i_q}^2\\ T_e=n_p[{\mathrm{\Ψ}}_f{i}_q+(L_d-L_q)i_d{i}_q]\end{array}\right.---\left(1\right)$

Encourage synchronous machine for perseverance, ψ _fconstant, therefore, meet the i that MTPA controls _d, i _qwith T _erelation

$\left\{\begin{array}{c}{i}_d=f_1\left(T_e\right)\\ i_q=f_2\left(T_e\right)\end{array}\right.---\left(2\right)$

Work as ψ _fwhen non-constant, when the exciting current of synchronous machine, along with rotating speed, variation is occurring, solved the i that MTPA controls that meets coming by formula (1) _d, i _qwith T _erelational expression as follows:

$\left\{\begin{array}{c}{i}_d=f_1(T_e,{\mathrm{\Ψ}}_f)\\ i_q=f_2(T_e,{\mathrm{\Ψ}}_f)\end{array}\right.---\left(3\right)$

For formula (3), function f ₁and f ₂the exact analytic expression be more difficult to determine, and can not adopt simple secondary or cubic polynomial to carry out matching.

Summary of the invention

The technical problem solving

For fear of the deficiencies in the prior art part, the present invention proposes a kind of change excitation magnetic synchronization motor maximum torque per ampere control method of Coefficient Fitting,

Technical scheme

A change excitation magnetic synchronization motor maximum torque per ampere control method for Coefficient Fitting, is characterized in that step is as follows:

Step 1: to becoming the excitation flux linkage data Ψ of excitation magnetic synchronization motor _fcarry out discretization processing, obtain n discrete point Ψ _fi, i=1,2 ..., n;

Step 2: by each Ψ _ficorresponding rectangular axis current i _di, i _qilinear expression is: i _di=k _1iu, i _qi=k _2iu, wherein: u is speed regulator output, k _1i, k _2ibe two unknown parameters;

Step 3: each excitation flux linkage discrete point Ψ _fisubstitution performance index $P\left(\mathrm{\α}\right)=\frac{1}{2}{n}_p{\mathrm{\Ψ}}_{\mathrm{fi}}\frac{k_{2i}}{\sqrt{(k_{1i}^2+k_{2i}^2)}}{\mathrm{\α}}^2-\frac{1}{3}{n}_p(L_d-L_q)\frac{k_{1i}{k}_{2i}}{k_{1i}^2+k_{2i}^2}{\mathrm{\α}}^3$ In, and it is carried out to partial differential iterative, obtain two parameter k at each excitation flux linkage discrete point place _1i, k _2i, bring rectangular axis current i into _di, i _qilinear expression obtains the approximate expression of rectangular axis electric current, and wherein α is motor stator current amplitude;

Step 4: when becoming excitation magnetic synchronization motor when starting, according to the excitation flux linkage changing, by with the excitation flux linkage discrete point Ψ of the identical numerical value of excitation flux linkage _fithe rectangular axis electric current that the approximate expression of the rectangular axis electric current corresponding, step 3 obtains calculates is as the rectangular axis electric current that becomes excitation magnetic synchronization motor.

Beneficial effect

The change excitation magnetic synchronization motor maximum torque per ampere control method of a kind of Coefficient Fitting that the present invention proposes, according to the excursion of exciting current, excitation flux linkage is carried out to discretization processing, then under the fixing condition of each specific excitation flux linkage, only carry out the matching of rectangular axis current function taking electromagnetic torque as variable, obtain many matched curves under excitation flux linkage change condition.When system operation, according to the excitation flux linkage size of different times, select matched curve immediate with it to carry out the calculating of rectangular axis electric current, just can obtain not the set-point of rectangular axis current value in the same time, finally complete the MTPA control that becomes excitation magnetic synchronization motor.

The inventive method has following beneficial effect:

1) adopt Coefficient Fitting Methods to carry out the matching of rectangular axis current function, solved and become the problem that in excitation magnetic synchronization motor MTPA control, rectangular axis current function is difficult to acquisition;

2) Coefficient Fitting Methods adopting in the inventive method is simply effective, has fitting degree good, the advantage that shared internal memory is little;

3) become excitation electromotor and in starting process, tend to produce torque pulsation because of the change of exciting current, adopt Coefficient Fitting Methods can effectively reduce to start the torque pulsation in period, make whole starting process comparatively level and smooth.

Brief description of the drawings

Fig. 1: the three grades of brushless synchronous initiation/power generation system structure of formula figure

Fig. 2: the flow chart that becomes excitation magnetic synchronization motor control method

Fig. 3: become excitation magnetic synchronization motor maximum torque per ampere control schematic diagram

Fig. 4: exciting current is with motor speed change curve

Fig. 5: the curve of direct-axis current under different exciting magnetic linkage

Fig. 6: the curve of quadrature axis electric current under different exciting magnetic linkage

Fig. 7: become excitation magnetic synchronization motor maximum torque per ampere control simulation result---rotating speed and torque curve

Fig. 8: become excitation magnetic synchronization motor maximum torque per ampere control simulation result---A phase current curve

Embodiment

Now in conjunction with the embodiments, the invention will be further described for accompanying drawing:

Become the control structure figure of excitation magnetic synchronization motor MTPA control as shown in Figure 2, the MTPA control becoming under excitation condition by adding MTPA Coefficient Fitting module to realize.

Becoming excitation magnetic synchronization motor MTPA controls compared with the permanent excitation of tradition or permagnetic synchronous motor MTPA control, maximum difference is that the MTPA of rectangular axis electric current resolves module, the present invention resolves module mainly for the rectangular axis electric current in control structure figure, a kind of method of Coefficient Fitting is proposed, under the prerequisite of formula (3), according to the excursion of exciting current, excitation flux linkage is carried out to discretization processing, then under the fixing condition of each specific excitation flux linkage, only carry out the matching of rectangular axis current function taking electromagnetic torque as variable, obtain many matched curves under excitation flux linkage change condition.When system operation, according to the excitation flux linkage size of different times, select matched curve immediate with it to carry out the calculating of rectangular axis electric current, just can obtain not the set-point of rectangular axis current value in the same time, finally complete the MTPA control that becomes excitation magnetic synchronization motor.

For checking the inventive method, adopt Matlab2012a-Simulink7.0 to carry out simulating, verifying.In emulation, electric excitation synchronous motor parameter is: number of pole-pairs n _p=3; Stator winding resistance R _s=10.3m Ω; D-axis inductance L _d=0.63mH; Quadrature axis inductance L _q=0.31mH; Mutual inductance L _m=6mH; Given rotating speed is 3500 (r/min).Exciting current with the curve of rotation speed change as shown in Figure 3.Concrete simulated conditions is set as: starting duty is 15Nm, and 500 (r/min) are increased to 45Nm afterwards gradually, and in the time that motor torque reaches 2200 (r/min), load declines again gradually, stable while being 6Nm to load.The three grades of brushless synchronous initiation/power generation system structure of formula figure as shown in Figure 1, become excitation magnetic synchronization motor maximum torque per ampere control schematic diagram as shown in Figure 2, and the flow chart of whole control method as shown in Figure 3.

The concrete steps that enforcement comprises are as follows:

(1) excitation flux linkage Ψ _fexcursion be 0.06～0.144Wb, so by its discrete be 0.06,0.072,0.084,0.096,0.108,0.12,0.132,0.144;

(2) by d-axis, the linear expression of quadrature axis electric current;

(3) each excitation flux linkage discrete point substitution performance index

$P\left(\mathrm{\α}\right)=\frac{1}{2}{n}_p{\mathrm{\Ψ}}_{\mathrm{fi}}\frac{k_{2i}}{\sqrt{(k_{1i}^2+k_{2i}^2)}}{\mathrm{\α}}^2-\frac{1}{3}{n}_p(L_d-L_q)\frac{k_{1i}{k}_{2i}}{k_{1i}^2+k_{2i}^2}{\mathrm{\α}}^3$ In and it is carried out to partial differential iteration

Solve, the rectangular axis electric current approximate expression under the different exciting current condition obtaining is as shown in the table, directly

Expression in angle coordinate system as shown in Figure 5,6;

Excitation flux linkage	Exciting current	Direct-axis current id polynomial fitting	Quadrature axis current i q polynomial fitting
				0.06	10	id 1＝0.2059*u	iq 1＝0.9785*u
0.072	12	id 2＝0.1914*u	iq 2＝0.9815*u
				0.084	14	id 3＝0.1774*u	iq 3＝0.9841*u
0.096	16	id 4＝0.16645*u	iq 4＝0.9860*u
				0.108	18	id 5＝0.15278*u	iq 5＝0.98826*u
0.12	20	id 6＝0.14220*u	iq 6＝0.9898*u
				0.132	22	id 7＝0.13270*u	iq 7＝0.99115*u
0.144	24	id 9＝0.12423*u	iq 9＝0.99225*u

(4) be basis according to rectangular axis electric current fitting function under the different exciting magnetic linkage obtaining, write rectangular axis electric current MTPA and resolve module.Exciting current (being designated as i_f) and the speed regulator output that is input as of this module (is designated as u), is output as direct-axis current set-point and quadrature axis given value of current value.

Here resolve as example and provide concrete implementation method taking direct-axis current, quadrature axis electric current is similar with it:

function?id＝fcn(u,i_f)

if(i_f<＝11)

id＝0.2059*u；

elseif(i_f<＝13)

id＝0.1914*u；

elseif(i_f<＝15)

id＝0.1774*u；

elseif(i_f<＝17)

id＝0.16645*u；

elseif(i_f<＝19)

id＝0.15278*u；

elseif(i_f<＝21)

id＝0.1422*u；

elseif(i_f<＝23)

id＝0.1327*u；

else

id＝0.12423*u；

end

Taking Fig. 2 as basis, in Matlab, set up and become excitation magnetic synchronization motor MTPA and control simulation model, wherein direct-axis current MTPA resolves module and writes according to foregoing, finally obtains simulation result as shown in Figure 7,8.

Claims (1)

1. a change excitation magnetic synchronization motor maximum torque per ampere control method for Coefficient Fitting, is characterized in that step is as follows:

Step 1: to becoming the excitation flux linkage data Ψ of excitation magnetic synchronization motor _fcarry out discretization processing, obtain n discrete point Ψ _fi, i=1,2 ..., n;

Step 2: by each Ψ _ficorresponding rectangular axis current i _di, i _qilinear expression is: i _di=k _1iu, i _qi=k _2iu, wherein: u is speed regulator output, k _1i, k _2ibe two unknown parameters;

Step 3: each excitation flux linkage discrete point Ψ _fisubstitution performance index in, and it is carried out to partial differential iterative, obtain two parameter k at each excitation flux linkage discrete point place _1i, k _2i, bring rectangular axis current i into _di, i _qilinear expression obtains the approximate expression of rectangular axis electric current, and wherein α is motor stator current amplitude;

Step 4: when becoming excitation magnetic synchronization motor when starting, according to the excitation flux linkage changing, by with the excitation flux linkage discrete point Ψ of the identical numerical value of excitation flux linkage _fithe rectangular axis electric current that the approximate expression of the rectangular axis electric current corresponding, step 3 obtains calculates is as the rectangular axis electric current that becomes excitation magnetic synchronization motor.