A control method for a semi-centralized open winding multi-motor drive system, wherein the drive system is composed of N motors (N>0), one side of each rotor winding is respectively connected to an independent inverter, the other sides of all rotor windings are connected to a shared inverter together, and all rotors are rigidly connected;
- the control method comprises the following steps:
- step 1:
- distributing a q axis current instruction i*q_x to a motor according to a thrust demand F*e:
- i
- q
-
- _
-
- x
- *
- =
- τ
- s
-
- F
- e
- *
- 3
-
- N
-
- π
-
- ψ
- f
-
- 1
- wherein ψƒ1 represents a permanent flux linkage of the motor, τs represents a polar distance of the same polarity between linear motors, and N represents the number of motors;
- step 2:
- computing a dq0 axis voltage required for each motor:
- first, computing a dq axis voltage using a proportional integral (PI) regulator:
- {
- u
- d
-
- _
-
- x
- =
- k
- p
-
- _
-
- d
-
- _x
- (
- i
- d
-
- _
-
- x
- *
- -
- i
- d
-
- _
-
- x
- )
- +
- k
- i_d
-
- _
-
- x
-
- ∫
- (
- i
- d
-
- _
-
- x
- *
- -
- i
- d
-
- _
-
- x
- )
-
- dt
- u
- d
-
- _
-
- x
- =
- k
- p
-
- _
-
- q
-
- _x
-
- (
- i
- q
-
- _
-
- x
- *
- -
- i
- q
-
- _
-
- x
- )
- +
- k
- i_q
-
- _
-
- x
-
- ∫
- (
- i
- q
-
- _
-
- x
- *
- -
- i
- q
-
- _
-
- x
- )
-
- dt
- wherein id_x, i*d_x, iq_x and i*q_x respectively represent actual dq axis currents and reference dq axis currents of the motor x, u*d_x and u*q_x represent voltage demands of the motor x, kp_d_v, ki_d_v, kp_q_v and ki_q_v respectively represent proportional coefficients and integral coefficients of a dq axis current regulator of the motor x, and x is the motor x, taking I, II, . . . , N;
- then, computing a zero sequence voltage by a proportional resonant (PR) regulator, as shown in the form of discretization:
- u
- k
- =
- K
- p
-
- _
-
- PI
- *
- e
- k
- +
- b
- 0
- *
- e
- k
- +
- b
- 2
- *
- e
- k
- -
- 2
- -
- a
- 1
-
- u
- k
- -
- 1
- -
- a
- 2
-
- u
- k
- -
- 2
- {
- a
- 0
- =
- -
- a
- 2
- =
- 4
-
- K
- s
-
- ω
- c
-
- T
- s
- 4
- +
- 4
-
- ω
- c
-
- T
- s
- +
- ω
- 0
- 2
-
- T
- s
- 2
- a
- 1
- =
- 0
- ,
- b
- 1
- =
- 1
- b
- 1
- =
- 2
-
- ω
- 0
- 2
-
- T
- s
- 2
- -
- 8
- 4
- +
- 4
-
- ω
- c
-
- T
- s
- +
- ω
- 0
- 2
-
- T
- s
- 2
- ,
- b
- 2
- =
- 4
- -
- 4
-
- ω
- c
-
- T
- s
- +
- ω
- 0
- 2
-
- T
- s
- 2
- 4
- +
- 4
-
- ω
- c
-
- T
- s
- +
- ω
- 0
- 2
-
- T
- s
- 2
- wherein uk represents a zero sequence voltage reference value u*0_x computed by the PR regulator at the time k, ek represents a difference value between 0 and a zero sequence current at the time k, subscripts k, k-1 and k-2 represent values at the time k, time k-1 and time k-2, Ts represents a counting period of a real-time processor, ωc represents a proportional resonant frequency, ω0 represents an electrical angular frequency of the motor, and Kp_PI and Ks represent proportional resonant coefficients of the motor;
- step 3:
- converting a dq axis reference voltage of each motor to the abc coordinate system:
- [
- u
- a
-
- _
-
- x
- *
- u
- b
-
- _
-
- x
- *
- u
- c
-
- _
-
- x
- *
- ]
- =
- [
- cos
-
- (
- θ
- x
- )
- -
- s
-
- in
-
- (
- θ
- x
- )
- 1
- cos
- (
- θ
- x
- -
- 2
- 3
-
- π
- )
- -
- sin
- (
- θ
- x
- -
- 2
- 3
-
- π
- )
- 1
- cos
-
- (
- θ
- x
- +
- 2
- 3
-
- π
- )
- -
- sin
- (
- θ
- x
- -
- 2
- 3
-
- π
- )
- 1
- ]
- [
- u
- d
-
- _
-
- x
- *
- u
- q
-
- _
-
- x
- *
- u
- 0
-
- _
-
- x
- *
- ]
- step 4:
- computing a voltage modulation coefficient of each phase of each motor:
- my_x=u*y_x/udc
- wherein u*y_x represents a phase voltage of the motor x, a subscript y represents a y phase, taking a, b or c, udc represents a direct current voltage of the motor, and my_x represents a y-phase voltage modulation coefficient of the motor x;
- computing limit values of the voltage modulation coefficient:
- {
- m
- y
-
- _
-
- max
- =
- max
-
- {
- m
- y
-
- _
-
- I
- ,
- m
- y
-
- _
-
- II
- ,
- …
- ,
- m
- y
-
- _
-
- N
- }
- m
- y
-
- _
-
- min
- =
- min
-
- {
- m
- y
-
- _
-
- I
- ,
- m
- y
-
- _
-
- II
- ,
- …
- ,
- m
- y
-
- _
-
- N
- }
- wherein my_max represents a maximum voltage modulation coefficient of the y phase, and my_min represents a minimum voltage modulation coefficient of the y phase;
- judging an operating area of the motor:
- k=max {ma_max−ma_min,mb_max−mb_min,mc_max−mc_min}
- wherein in a case that k>1, the motor is located in an over-modulated area, otherwise, the motor is located in a linear modulation area;
- step 5:
- processing the over-modulated area:
- computing limit values of a corrected voltage modulation coefficient:
- {
- m
- y
-
- _
-
- max
- k
- =
- m
- y
-
- _
-
- max
- max
-
- {
- 1
- ,
- m
- y
-
- _
-
- max
- -
- m
- y
-
- _
-
- min
- }
- m
- y
-
- _
-
- min
- k
- =
- m
- y
-
- _
-
- min
- max
-
- {
- 1
- ,
- m
- y
-
- _
-
- max
- -
- m
- y
-
- _
-
- min
- }
- wherein my_maxk represents an improved maximum voltage modulation coefficient of the y phase, and my_mink represents an improved minimum voltage modulation coefficient of the y phase;
- computing corrected limit coefficients (ky_xmax, ky_xmin) of the voltage modulation coefficient:
- {
- k
- y
-
- _
-
- x
- max
- =
- min
-
- {
- m
- y
-
- _
-
- x
- ,
- m
- y
-
- _
-
- max
- k
- }
- m
- y
-
- _
-
- x
- k
- y
-
- _
-
- x
- min
- =
- max
-
- {
- m
- y
-
- _
-
- x
- ,
- m
- y
-
- _
-
- min
- k
- }
- m
- y
-
- _
-
- x
- computing a phase correction coefficient ky_x of the voltage modulation coefficient of each phase:
- ky_x=min {ky_xmax,ky_xmin}
- computing a correction coefficient kx of the motor of the voltage modulation coefficient:
- kx=min {ka_x,kb_x,kc_x}
- computing a voltage modulation coefficient corrected value myk by the corrected value and the voltage modulation coefficient:
- my_xk=kxmy_x
- step 6:
- computing limit duty ratios (δy_s_max, δy_s_max) of a shared bridge arm:
- {
- δ
- y
-
- _
-
- s
-
- _
-
- max
- =
- min
-
- {
- 1
- -
- m
- y
-
- _
-
- max
- k
- ,
- 1
- }
- δ
- y
-
- _
-
- s
-
- _
-
- min
- =
- max
-
- {
- -
- m
- y
-
- _
-
- min
- k
- ,
- 0
- }
- computing an optimal duty ratio δy_s of the shared bridge arm by the limit duty ratios:
- δ
- y
-
- _
-
- s
- =
- δ
- y
-
- _
-
- s
-
- _
-
- max
- +
- δ
- y
-
- _
-
- s
-
- _
-
- min
- 2
- computing a duty ratio of an independent bridge arm based on the optimal duty ratio of the shared bridge arm and the voltage modulation coefficient:
- δy_x=my_xk+δy_P.