Phase Current Prediction Using DC Link Measurement
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Solution Overview
Problem
In motor control systems using a single current sensor, current measurements during the switching period result in current errors and ripples due to varying motor currents, leading to noise and degraded product quality in SVPWM schemes.
Innovation Solution
A phase current prediction method that measures DC link current during effective voltage vector periods and predicts phase currents for a PWM period, using these measurements to reduce current errors and ripples by applying sequential effective voltage vectors and reconstructing phase currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current is measured in a switching period using a single current sensor, then device complexity is reduced, but measurement precision deteriorates due to current errors and ripples
Solution Approach 1:
The patent uses DC link current as an intermediary measurement to indirectly obtain phase current information. Instead of directly measuring phase currents with multiple sensors, the method measures the DC link current during effective voltage vector periods and uses it as a mediator to calculate representative phase currents, thereby reducing sensor requirements while maintaining measurement accuracy
Solution Approach 2:
The patent applies preliminary action by measuring DC link current during effective voltage vector periods before the actual PWM switching occurs. This preliminary measurement allows the system to predict and calculate accurate phase current representative values in advance, avoiding the measurement errors that occur when measuring during the switching period itself
2Measurement precision
If DC link current is measured during effective voltage vector periods and phase currents are predicted, then measurement precision is improved by reducing current errors, but device complexity increases due to additional prediction calculations
Solution Approach 1:
The patent changes the measurement parameter from direct phase current to DC link current during effective voltage vector periods. This parameter change simplifies the measurement process and enables more accurate predictions by measuring during periods when the relationship between DC link current and phase current is well-defined and stable
Solution Approach 2:
The patent creates a simplified copy of the current measurement problem by measuring DC link current instead of directly measuring phase currents. This copying approach allows the system to obtain sufficient current information for control purposes while avoiding the complexity of direct phase current measurement during switching periods
Data Source
AI summary
A phase current prediction method is disclosed. The phase current prediction method predicts current representative of a PWM period using a motor model which receives current measured through a single current sensor as an input, instead of the measured current, and determines the predicted current to be phase current.