US 4,812,669 AGranted

Harmonic suppressing device

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorsMasatoshi Takeda, Kazuo Ikeda, Yoshiharu Tominaga, Kenji Mori

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Abstract

A harmonic suppressing device provided in a power system such as, for example, a transmission and distribution system or a power generating system, to filter higher harmonic currents generated by a higher harmonic current source of the power system such as, for example, a cycloconverter. The harmonic suppressing device comprises, as the principal components thereof, a passive filter serving as a high-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively high order among those generated by the higher harmonic current source, and an active filter serving as low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders among those generated by the higher harmonic current source. The active filter comprises: a main active filtering circuit comprising a plurality of switching transistors, rectifying diodes combined with the switching transistors, respectively, a capacitor, and a reactor; an operating circuit which calculates controlling data for controlling the commutating action of the main active filtering circuit on the basis of the detected values of the higher harmonic currents that flows into the power source side of the power system and the detected values of the output voltage of the higher harmonic current source; and a control circuit which gives control signals such as, for example, pulse width modulating signals to the main active filtering circuit. The harmonic suppressing device is capable of filtering higher harmonic currents in a wide frequency band.

Claims9

Dependent claims

A harmonic suppressing device comprising:

a passive filter comprising a series connection of a capacitor and a reactor, and serving as a high-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively high orders in a frequency band around a tuned point among higher harmonic currents generated by the higher harmonic current source of a power system;
an active filter serving as low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders in a frequency band around an antiresonance point among those generated by said higher harmonic current source, connected in parallel to said passive filter and adapted so as to be controlled on the basis of a value obtained by multiplying the detected value of a higher harmonic current that flows into the power source side beyond the connecting point of said passive filter and a power source by a fixed gain;
said active filter comprising:
a main active filtering circuit comprising a parallel connection of a plurality of switching transistors, diodes connected in parallel to said switching transistors, respectively, and a capacitor;
and control means for controlling said switching transistors for on-off operation;
and
said control means comprising a PWM control circuit capable of carrying out PWM control on the basis of a value obtained by processing through subtraction, amplification and addition the output of a gain circuit which executes a first order lag operation by multiplying the detected values of higher harmonic currents that flow into the power source side of said power system by a fixed gain, the detected current values of the output currents of said main active filtering circuit, and the detected voltage values of higher harmonic currents generated by said higher harmonic current source and flowing into the power source side of said power system.

4 more elements

A harmonic suppressing device comprising:

a passive filter serving as a high-order higher harmonic filtering unit comprising a series connection of a capacitor and a reactor and capable of filtering higher harmonic currents of comparatively high orders in a frequency band around a tuned point among those generated by a higher harmonic current source;
and
an active filter serving as a low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders in a frequency band around a resonance point, comprising:
a main active filtering circuit comprising a parallel connection of a plurality of switching transistors, diodes connected in parallel to said switching transistors, respectively, and a capacitor connected in parallel with said parallel connection of switching transistors;
and
control means comprising:
operating means which processes through a predetermined advancing operation the detected values of higher harmonic currents that flow into the power source side of said power system beyond the connecting point of said passive filter and said power system;
and control means for controlling said switching transistors for on-off operation by a control output obtained by subjecting the detected current values of the output currents of said main circuit, and detected voltage values detected in the neighborhood of said higher harmonic current source on the basis of the results of operation of said operating means to addition, subtraction and amplification.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/066,203Filed 25 Jun 1987
Priority: JP 61-14810226 Jun 1986
Granted: 14 Mar 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

H02J 3/01
Circuit arrangements for AC mains or AC distribution networks: arrangements for reducing harmonics or ripples
H02M 1/084
Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters: using a control…
H02M 1/12
Details of apparatus for conversion: arrangements for reducing harmonics from AC input or output
H02M 1/4283
Arrangements for improving power factor of AC input: by adding a controlled rectifier in parallel to a first rectifier feeding a smoothing capacitor