Inverter Driving Device Offset Current Detection
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Solution Overview
Problem
Existing inverter driving devices inaccurately detect motor current offsets during ground or sky faults, leading to decreased current detection accuracy due to misidentification of fault currents as offset currents.
Innovation Solution
An inverter driving device that detects and compensates for offset currents by calculating the offset component using coincident current values in two phases of a three-phase alternating current, improving detection accuracy without increasing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If offset detection is performed using direct bus current during PWM period with vector V0, then offset detection is simplified, but ground fault or sky fault currents are misdetected as offset currents, decreasing measurement precision
Solution Approach 1:
The patent extracts and identifies the characteristic feature of valid offset detection conditions by comparing current values across three phases. It separates valid offset detection (when two phases have substantially equal current values) from invalid detection (when fault currents are present), allowing the system to perform offset detection only under valid conditions while rejecting measurements during ground or sky faults.
Solution Approach 2:
The patent performs preliminary verification by comparing current values in two phases before accepting the offset detection result. This preliminary action checks whether the detected offset is valid by verifying that current values in two phases substantially coincide, preventing misidentification of fault currents as offset currents before the offset correction is applied.
2Device complexity
If current sensors are reduced to use direct bus current for motor current detection, then device complexity is reduced, but detection accuracy deteriorates due to fault current misidentification
Solution Approach 1:
The patent introduces an intermediary verification mechanism that uses the relationship between three-phase current values as a mediator to validate offset detection results. By checking whether current values in two phases substantially coincide, the system uses this intermediary condition to distinguish between valid offset detection and fault conditions, ensuring accurate motor current detection even with reduced sensor count.
Solution Approach 2:
The patent implements feedback by continuously monitoring current values in multiple phases and using this information to validate offset detection results. The system feeds back the comparison result to determine whether to accept or reject the detected offset, preventing fault currents from corrupting the motor current detection while maintaining the simplified single-sensor architecture.
3Measurement precision
If offset correction is applied using detected offset values, then measurement precision is improved under normal conditions, but reliability decreases when ground or sky faults occur due to misdetected offset values
Solution Approach 1:
The patent applies preliminary anti-action by implementing a verification check before applying offset correction. It anticipates the possibility of fault conditions and prevents harmful offset correction by verifying that current values in two phases substantially coincide. This preliminary protective action blocks the application of incorrect offset values during ground or sky faults while allowing normal offset correction during healthy operation.
Solution Approach 2:
The patent performs preliminary validation of offset detection results by comparing current values across phases before applying offset correction. This preliminary action ensures that only valid offset values (those detected under normal operating conditions) are used for correction, preventing reliability degradation during fault conditions while maintaining measurement precision during normal operation.
Data Source
AI summary
A motor driving device controls driving of an inverter device, detects current values in two phases, and compensates a value. The motor driving device detects current values in two phases, namely, a maximum phase current value and a minimum phase current value, within a single cycle of a PWM carrier frequency. The motor driving device compensates a value obtained by subtracting an absolute value of a difference between two absolute values, namely, the detected maximum phase current value and minimum phase current value, from the smaller value of the absolute values, as the offset current component.