Power Conversion Device Leak Current Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion and compressor driving devices face challenges in reducing leak current to ground effectively, as previous methods either lead to inverse compensation or suffer from delay in compensation operations, resulting in incomplete leak current reduction.
Innovation Solution
A power conversion device with a feedback control system that includes a leak-current detecting unit, a leak-current control unit for lead compensation, and an anti-phase current generating unit, which accumulates leak current data to instantaneously cancel out the leak current without causing inverse compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If anti-phase current is injected using inverter driving signal to reduce leak current, then leak current is reduced under ideal conditions, but phase mismatch may occur causing inverse compensation that increases leak current
Solution Approach 1:
The patent implements a feedback control system that detects the actual leak current and uses this information to adjust the anti-phase current injection. The detection unit measures the leak current, and the control unit processes this feedback signal to generate an adjusted anti-phase current that compensates for both the leak current and any injection circuit delays, preventing inverse compensation
Solution Approach 2:
The patent introduces a delay element that advances the anti-phase current injection timing before the leak current detection is completed. This preliminary action ensures that the anti-phase current is injected at the correct phase angle, compensating for the inherent delay in the injection circuit and preventing phase mismatch that would cause inverse compensation
2Measurement precision
If leak current is detected first and then compensation operation is performed, then compensation can be performed based on actual leak current, but delay occurs preventing synchronized compensation
Solution Approach 1:
The patent performs preliminary timing adjustment by introducing a delay element that advances the anti-phase current injection timing. This ensures that the compensation operation is synchronized with the leak current waveform, eliminating the time loss that would otherwise prevent effective compensation
3Measurement precision
If compensation operation is performed after leak current detection, then detection accuracy is achieved, but compensation amount is insufficient due to delay
Solution Approach 1:
The patent uses feedback control where the detected leak current is processed to generate an adjusted anti-phase current that accounts for injection circuit delays. This feedback mechanism ensures that the compensation amount is sufficient and effective, maintaining both detection accuracy and compensation productivity
Solution Approach 2:
The patent introduces a delay element that advances the injection timing, ensuring that the anti-phase current is injected at the optimal phase angle. This preliminary timing adjustment maximizes the compensation effectiveness, ensuring that the full compensation potential is achieved without loss of productivity
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
To include a leak-current detecting unit 21 that detects a zero-phase current flowing from an electric-motor driving device 100, which drives an electric motor 5 with electric power from an alternating-current power supply 1, or the electric motor 5 to a ground E2, a leak-current control unit 22 that, on the basis of the zero-phase current detected by the leak-current detecting unit 21, generates a control signal having cyclicity synchronized with the alternating-current power supply 1, and an anti-phase generating unit 23 that generates an anti-phase current that is in anti-phase to the zero-phase current on the basis of the control signal from the leak-current control unit 22, and outputs the anti-phase current.