Active Filter Control Device for Resonance Suppression
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Solution Overview
Problem
Conventional active filter techniques fail to effectively reduce resonance when an electrolytic capacitorless inverter is used as a load and power source impedance is high, and they also cannot minimize the capacity of the active filter.
Innovation Solution
A control device for an active filter that adjusts the compensation rates of the q-axis and d-axis currents, specifically reducing the q-axis compensation rate to less than 1.0 and setting the d-axis compensation rate as low as possible to minimize the active filter's capacity and resonance, while ensuring the harmonic current is reduced to a standard value or lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional active filter control techniques are used, then harmonic current compensation is provided, but resonance cannot be effectively reduced when power source impedance is large
Solution Approach 1:
The patent changes the control parameters by introducing separate compensation rates Kd and Kq for d-axis and q-axis currents. By adjusting these parameters (specifically setting Kq < 1.0 and Kd as low as possible), the system achieves both harmonic current reduction and resonance suppression when power source impedance is large, resolving the contradiction between harmonic compensation and resonance reduction effectiveness.
2Object-generated harmful factors
If conventional active filter control techniques are used, then harmonic current compensation is provided, but the capacity of the active filter cannot be minimized
Solution Approach 1:
The patent optimizes the capacity of the active filter by changing the control parameters Kd and Kq. By setting Kq to a value less than 1.0 and Kd as low as possible, the compensation current magnitude is reduced while still meeting harmonic current standards, thereby minimizing the required active filter capacity.
Solution Approach 2:
The patent applies partial compensation rather than full compensation by setting compensation rates less than 1.0. This partial action approach reduces the active filter capacity requirements while still achieving acceptable harmonic current levels that meet regulatory standards.
3Reliability
If the q-axis compensation rate is reduced to minimize resonance, then resonance is reduced, but harmonic current reduction effectiveness may be compromised
Solution Approach 1:
The patent segments the compensation control into two independent components: d-axis current compensation with rate Kd and q-axis current compensation with rate Kq. This segmentation allows independent optimization of each axis, enabling the system to reduce resonance by adjusting Kq while maintaining harmonic current reduction effectiveness through appropriate Kd settings.
Solution Approach 2:
By introducing separate compensation rates for d-axis and q-axis currents, the patent enables independent parameter optimization. The system can set Kq < 1.0 to reduce resonance while adjusting Kd to maintain effective harmonic current compensation, resolving the contradiction between resonance reduction and harmonic current reduction effectiveness.
Data Source
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AI summary
Disclosed is a control device (71) controlling an operation of an active filter (6) which is connected in parallel with a load (2) at an installation point (P) with respect to an AC power source (1) and which supplies a compensation current (Ic) to the installation point (P) so as to compensate for a harmonic component of a load current (Io) flowing through the load (2). The control device (71) includes: a dq converter (703) converting the load current (Io) into a component of a d-axis current and a component of a q-axis current; a high-pass filter (704, 705) extracting a harmonic component from at least the component of the q-axis current output from the dq converter; a multiplier (716) outputting a result obtained by multiplying a component of a d-axis current output from the high-pass filter (704) by a compensation rate (Kd) as a current command value (id*); and a multiplier (717) outputting a result obtained by multiplying the component of the q-axis current output from the dq converter (703) or a component of a q-axis current output from the high-pass filter (705) by a compensation rate (Kq) as a current command value (iq*). The compensation rate (Kq) of the q-axis current in the multipliers (716, 717) is adjustable.