Damping resonant oscillations in a parallel resonant inverter

• US 5,128,853 A
• Filed: 02/07/1991
• Issued: 07/07/1992
• Est. Priority Date: 02/07/1990
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Heinle, Georg
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US07/652,423
• Time in Patent Office: 516 Days
• Field of Search: 363/34, 363/37, 363/39, 363/40, 363/41, 363/95, 363/96, 363/137
• US Class Current: 363/41
• CPC Class Codes: H02M 5/4505 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/53873 with digital control

Abstract

A control process and trigger equipment damps resonant oscillations of a parallel-resonant circuit for a pulse-controlled inverter of a current-source inverter. The pulse-controlled inverter contains turn-off current-converter switches and is linked to an inductive and to a capacitive load. This inductive and capacitive load forms a parallel-resonant circuit. A modulation mode is selected from several stored modulation modes from the system frequency (f₁) of the converter current (I_R). Depending upon a calculated factor (f₁ /f_res) and the selected modulation mode, switching angles (α₁, α₂, . . . , α_n) are determined depending upon system frequency by means of stored, pre-set switching angles. From these switching angles the control times for the pulse-controlled inverter are then generated. Thus, the pulse edges of a selected modulation mode can be adjusted with the system frequency as a function of frequency, enabling the resonant oscillations to be adequately damped over the entire system frequency range.

Claims

1. A control process for damping resonant oscillations of a parallel-resonant circuit for a pulse-controlled inverter, which has a plurality of current-converter switches, of a current-source inverter, comprising the steps of:

a) forming a parallel-resonant circuit by linking the current converter switches to an inductive load and to a capacitive load;

b) storing a plurality of modulation modes and pre-set switching angles;

c) receiving a system frequency of a converter current;

d) selecting a selected modulation mode by means of the system frequency from the plurality of stored modulation modes;

e) calculating a factor (f₁ /f_res);

f) determining a plurality of switching angles from the stored plurality of pre-set switching angles, depending upon the factor (f₁ /f_res), the selected modulation mode, and the system frequency; and

g) generating a plurality of control times for the pulse-controlled inverter.

2. The control process according to claim 1, further comprising the step of calculating the plurality of pre-set switching angles for a 3-times pulsation from the following equations:

##EQU7## wherein α

₁ is a switching angle, and α

_up and α

_low are an upper and a lower limit respectively of α

₁.

3. The control process according to claim 1, further comprising the step of calculating the plurality of pre-set switching angles for a 5-times pulsation from the following equations:

##EQU8## wherein α

₁ and α

₂ are switching angles, α

_up1 and α

_low1 are an upper and a lower limit respectively of α

₁, and α

_up2 and α

_low2 are an upper and a lower limit respectively of α

₂.

4. The control process according to claim 1, further comprising the step of calculating the plurality of pre-set switching angles for a 7-times pulsation from the following equations:

##EQU9## wherein α

₁, α

₂, and α

₃ are switching angles, α

_up1 and α

_low1 are an upper and a lower limit respectively of α

₁, α

_up2 and α

_low2 are an upper and a lower limit respectively of α

₂, and α

_up3 and α

_low3 are an upper and a lower limit respectively of α

₃.

5. A trigger equipment for a pulse-controlled inverter, which has a plurality of current switches, of a current-source inverter, comprising:

a) an inductive load and a capacitive load being linked to the current switches, and forming a parallel-resonant circuit having a resonant frequency (f_res);

b) a memory containing a plurality of tables and storing a plurality of modulation modes and pre-set switching angles, and having a first and second input;

c) a generating device generating a plurality of control times for the pulse-controlled inverter, and being coupled in series with the memory;

d) an identifying device identifying a system frequency range, having a system frequency of the current-source inverter as an input, and having an output coupled to the first input of the memory, wherein the memory selects a selected modulation mode from the plurality of modulation modes stored in memory based on the system frequency; and

e) a divider having a first and second input, dividing the first input by the second input to form a factor (f₁ /f_res), and having an output coupled to the second input of the memory, whereby a system frequency (f₁) is applied to the input of the identifying device and is also applied to the first input of the divider, and the resonant frequency (f_res) is applied to second input of the divider, wherein the memory determines the plurality of switching angles from the stored plurality of pre-set switching angles based on the factor (f₁ /f_res), the selected modulation mode and the system frequency.

6. A trigger apparatus for a pulse-controlled inverter, which has a plurality of current switches, of a current-source inverter, comprising:

a) an inductive load and a capacitive load being linked to the current switches, and forming a parallel-resonant circuit having a resonant frequency (f_res);

b) a microcomputer, receiving the system frequency (f ) and the resonant frequency (f_res), storing a plurality of tables, identifying a system frequency range, calculating a plurality of control times from the plurality of tables and system frequency range, and outputting the control times.