Multiphase Power Converter Current Estimation with Fixed Sampling Cycle
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Solution Overview
Problem
Existing multiphase power converters face issues with estimation error and delay due to the inability to acquire sufficient sampling information at fixed cycles, particularly when voltage conditions result in overlapping ON/OFF switching timings and detection timings, and non-regular matrix representations lead to estimation challenges.
Innovation Solution
A power conversion device with a PWM control unit generating ON/OFF signals based on Duty commands and triangular wave carriers with different initial phases, a current estimation unit acquiring detected values at a sampling cycle distinct from the carrier cycle, and a current control unit adjusting Duty commands to synchronize phase currents with target values, ensuring stable current estimation and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two pieces of sampling information are acquired per carrier cycle using switching patterns and zero-sum characteristics, then phase current estimation is achieved, but estimation error occurs when voltage conditions cause overlapping ON/OFF timings
Solution Approach 1:
The patent changes the sampling cycle parameter from being tied to the carrier cycle to being a fixed independent cycle. This allows sampling to occur at optimal timing points regardless of the carrier wave phase, avoiding the estimation errors that occur when voltage conditions cause overlapping switching timings. The sampling timing is adjusted to coincide with maximum and minimum values of triangular wave carriers, ensuring reliable measurement.
Solution Approach 2:
The patent performs preliminary selection of sampling points that coincide with maximum and minimum values of triangular wave carriers before actual current estimation. By pre-identifying optimal sampling timing based on carrier wave characteristics, the system ensures that sampling always occurs at reliable points where switching states are clearly defined, preventing estimation errors from overlapping timings.
2Productivity
If sampling is performed at carrier cycle frequency, then phase current estimation is possible, but fixed cycle sampling cannot be achieved
Solution Approach 1:
The patent introduces dynamic adjustment of sampling timing relative to the carrier cycle. The sampling cycle is set independently and may differ from the carrier cycle, allowing the system to adapt sampling frequency to optimization criteria rather than being constrained to carrier cycle frequency. This dynamic approach enables both high productivity and cycle consistency.
Solution Approach 2:
The patent segments the sampling process from the carrier wave generation process. By treating sampling as a separate, independently timed operation rather than being locked to carrier cycle events, the system can maintain fixed cycle sampling while still operating at appropriate rates for accurate current estimation.
3Measurement precision
If matrix expression with switch ON/OFF states is used for current estimation, then phase current can be reproduced, but estimation cannot be performed when matrix is not regular
Solution Approach 1:
The patent introduces sampling timing coincidence with carrier wave extrema as an intermediary condition that ensures the switching state matrix remains regular. By forcing sampling to occur at maximum or minimum carrier values, the system guarantees that the resulting matrix has full rank and can be inverted, while still accurately representing the phase current states.
Solution Approach 2:
The patent applies preliminary anti-action by pre-preventing the formation of singular matrices through careful selection of sampling timing. By choosing sampling points at carrier wave extrema, the system proactively avoids the condition where the switching matrix becomes non-regular, eliminating the need for fallback estimation methods.
Data Source
AI summary
A PWM control unit generates signals for controlling switching elements in respective legs based on the magnitude relationship between individual Duty commands for the respective legs and triangular wave carriers having different initial phases and having a common cycle, a current estimation unit acquires detected values from a current detector at a sampling cycle different from the carrier cycle and estimates the phase currents, and a current control unit adjusts Duty commands so that the estimated phase currents coincide with target values for the phase currents.