PWM rectifier including capacitance calculation unit

Patent metadata

Field	Value
Publication number	US-9923477-B2
Application number	US-201615387581-A
Country	US
Kind code	B2
Filing date	Dec 21, 2016
Priority date	Sep 10, 2014
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

A PWM rectifier includes a main circuit unit carrying out AC-DC power conversion by PWM-control, a PWM control unit PWM-controlling the main circuit unit, a DC voltage detection unit detecting a DC voltage across a smoothing capacitor connected to the DC-side of the main circuit unit, a DC voltage storage unit storing respective DC voltages at the start and end times of an initial boost period during which the smoothing capacitor having been charged to an AC voltage peak value is further charged to a higher voltage, an input power calculation unit calculating input power flowing in from the AC-side based on an AC voltage and current, an integral power calculation unit calculating integral power from the input power over the initial boost period, and a capacitance calculation unit calculating the capacitance of the smoothing capacitor based on the respective DC voltages and the integral power.

First claim

What is claimed is:

1. A PWM rectifier, comprising:
a main circuit unit configured to carry out power conversion between AC power on an AC side of the main circuit unit and DC power on a DC side of the main circuit unit through a switching operation of a switching element being PWM-controlled by a received PWM control signal;
a PWM control unit configured to generate and output the PWM control signal to the main circuit unit;
a DC voltage detection unit configured to detect a DC voltage across a smoothing capacitor, which is connected to the DC side of the main circuit unit in parallel;
a DC voltage storage unit configured to, in an initial boost period during which the smoothing capacitor, which has been initially charged to a peak value of an AC voltage on the AC side of the main circuit unit, is further charged to a voltage higher than the peak value of the AC voltage through a power conversion operation of the main circuit unit, store respective DC voltages detected by the DC voltage detection unit at a start time and an end time of the initial boost period;
an input power calculation unit configured to calculate input power flowing into the main circuit unit from the AC side based on an AC voltage and an AC current on the AC side of the main circuit unit;
an integral power calculation unit configured to integrate the input power calculated by the input power calculation unit during the initial boost period and output the integrated value as energy; and
a capacitance calculation unit configured to calculate a capacitance of the smoothing capacitor based on the DC voltage at the start time of the initial boost period and the DC voltage at the end time of the initial boost period, which are stored in the DC voltage storage unit, and the energy.

2. The PWM rectifier according to claim 1 ,
wherein, when it is assumed that the DC voltage at the start time of the initial boost period, the DC voltage at the end time of the initial boost period, and the energy are denoted by VL, VH, and W, respectively, the capacitance calculation unit calculates a capacitance C of the smoothing capacitor by the following equation

C
=

2
×
W

V
H
2

-

V
L
2

.

3. The PWM rectifier according to claim 1 , further comprising:
a capacitance drop judgment unit configured to judge whether or not the capacitance calculated by the capacitance calculation unit is lower than a predetermined value; and
a warning signal output unit configured to output a warning signal when the capacitance drop judgment unit judges that the capacitance is lower than the predetermined value.

4. The PWM rectifier according to claim 3 , further comprising:
a notification unit configured to prompt a replacement of the smoothing capacitor, which is connected to the DC side of the main circuit unit in parallel, when the warning signal output unit outputs the warning signal.

5. The PWM rectifier according to claim 3 , further comprising:
a stop instruction unit configured to instruct stop of the switching operation of the switching element in the main circuit unit when the warning signal output unit outputs the warning signal.

Assignees

• Fanuc Corp

Inventors

• Niwa Masakazu

Classifications

• H02M7/2173

  in a biphase or polyphase circuit arrangement (H02M7/2176 takes precedence; voltage multipliers H02M7/25) · CPC title

• H02M5/4585 Primary

  having a rectifier with controlled elements · CPC title

• H02M7/219

  in a bridge configuration · CPC title

• G01R27/26

  Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants {; Measuring impedance or related variables} · CPC title

• G01R31/40

  Testing power supplies (testing photovoltaic devices H02S50/10) · CPC title