Active filter control device
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Solution Overview
Problem
The current control methods for parallel active filters, which rely on proportional integral controllers, suffer from delays in compensating current due to arithmetic processing, hindering the effective suppression of harmonic components in power current.
Innovation Solution
An active filter control device that includes a harmonic component extraction unit, a difference current generation unit with a phase leading mechanism to eliminate delays, and a current controller to generate control signals for the parallel active filter, ensuring the compensating current aligns with the command value by introducing a predetermined phase difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a proportional integral controller is used for current control in a parallel active filter, then the controller can effectively regulate the compensating current, but the arithmetic processing causes a delay in the compensating current relative to the command value
Solution Approach 1:
The patent applies preliminary action by calculating and storing prediction values of the command value in advance. The prediction value calculation unit computes future command values based on past values, and these pre-calculated prediction values are stored in memory for immediate use during control processing, eliminating the need for real-time arithmetic operations that cause delay
Solution Approach 2:
The patent uses copying by creating prediction values that replicate the expected command value waveform. Instead of performing complex real-time calculations, the system copies the pattern from past command values to generate future prediction values, which are then used directly in the control loop without additional processing delay
2Productivity
If the command value varies significantly, then the active filter must respond quickly to maintain harmonic suppression, but the arithmetic processing delay becomes more noticeable and reduces effectiveness
Solution Approach 1:
The system performs preliminary calculation of prediction values that anticipate future command values. By pre-computing these values based on the historical pattern of command variations, the system is prepared for significant changes before they occur, enabling rapid response without real-time calculation delays
Solution Approach 2:
The prediction value calculation uses feedback from past command values to generate accurate predictions of future values. This feedback mechanism allows the system to adapt to varying command patterns and maintain accurate prediction even when the command value changes significantly, ensuring continuous effective harmonic suppression
Data Source
AI summary
A harmonic component extraction unit obtains a command value of compensating current from a harmonic component of the load current. A difference current generation unit obtains a deviation between the compensating current and a value obtained by leading a phase of the command value by a predetermined phase difference. A current controller generates a control signal based on output of the difference current generation unit. A driving signal generation circuit generates, based on the control signal, a driving signal driving a parallel active filter.