Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Patent
1994-06-02
1997-05-20
Nguyen, Matthew V.
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
318812, H02M 545, H02P 318
Patent
active
056318120
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor drive control method which is controlled based on the PWM (Pulse Width Modulation) method, and more particularly to a motor drive current control method.
2. Description of the Related Art
FIG. 5 is a block diagram of a motor current drive circuit according to a conventional PWM control method. A block shown by a reference numeral 1 is a rectification circuit, which rectifies an AC electric power source of three phases, that is, R-, S- and T-, phases, to generate a DC main voltage Vlink. This main voltage Vlink is applied to a bridge circuit in an electric power conversion circuit 2. A reference character C1 represents a smoothing capacitor. A current control section 3 outputs PWM signals so that the motor current follows a current command Icmd on the basis of the current command Icmd and respective phase currents i.sub.1 to i.sub.n detected by respective phase current detecting circuits 5-1 to 5-n, whereby the switching elements of the bridge circuit 2, such as transistors G1 to Gn, can be turned on and off.
FIG. 6 is a block diagram showing one example of a current drive circuit for a DC (direct current) motor based on the conventional PWM control system. A main voltage Vlink outputted from a rectification circuit 1 is applied to an electric power conversion circuit 2. This electric power conversion circuit 2 includes of a bridge circuit of transistors and diodes. A current control section 3 calculates a PWM signal based on a current command value Icmd and an actual current i detected by a current detector 5-1, and outputs the PWM signal to each of the base terminals of transistors G1 to G4 for the on-off control of each of the transistors and the drive control of a DC motor 6-3 therethrough. The on and off states of the transistors G1 to G4 are controlled in a manner such that the transistor G1 is on while the transistor G2 is off and vice versa, applying the same to the transistors G3 and G4, and that the transistors G1 and G4 are turned on and off simultaneously, applying the same to the transistors G2 and G3. As shown in FIG. 6, outputs of the current control section 3 are represented by reference characters G1 to G4 corresponding to the bases of respective transistors G1 to G4.
FIG. 7(a) is a block diagram illustrating current loop control based on the proportional control in the current control section 3 of the DC motor current drive circuit as shown in FIG. 6.
In the current control section 3, the current command value Icmd is subtracted from the actual current i detected by the current detector 5-1 to obtain a current deviation (Icmd-i), and this current deviation is multiplied by a predetermined current loop proportional gain K (set in an element 31) to obtain a voltage command Vcmd. Then, the resulting value is multiplied by a reciprocal of a doubled value of a predetermined main voltage equivalent value Vlink1 (in an element 32). To this result, 1/2 is added to obtain a duty ratio .eta. of the PWM signal. That is,
The procedure for obtaining the PWM signal with this duty ratio .eta. (corresponding to a portion denoted by reference numeral 3 and encircled by a dotted line in FIG. 7(a)) is executed by ordinary processors. The PWM signal with this duty ratio .eta. is inputted into the gates (G1 to G4 of FIG. 6) of respective transistors in the electric power conversion circuit 2.
Then, 1/2 is subtracted from the output .eta. of the electric power control section 3, and the result is multiplied by a value of an element 10 to obtain a voltage V to be actually supplied to a motor. A half value of the element 10, i.e., Vlink2 of FIG. 7(a), is an actual main voltage Vlink outputted from the rectification circuit 1 of FIG. 6. When the actual main voltage Vlink remains constant regardless of time, and the value Vlink1 equivalent to the predetermined main voltage is equal to the value Vlink in the current control section 3 (i.e. element 32), or where Vlink=Vlink1=Vlink2, the voltage V to be applied to the motor
REFERENCES:
patent: 4876637 (1989-10-01), Mose et al.
patent: 4903184 (1990-02-01), Hirose
patent: 4933828 (1990-06-01), Ogawa
patent: 4934822 (1990-06-01), Higaki
patent: 5050057 (1991-09-01), Notohara et al.
patent: 5483167 (1996-01-01), Mikami
Arimoto Kohei
Sakano Tetsuro
Fanuc Ltd.
Nguyen Matthew V.
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