Inverter Control Device Switching Timing Optimization
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Solution Overview
Problem
Inverters experience fluctuations in output power due to changes in switching patterns during an electrical angle period, leading to current offsets and torque fluctuations in motor generators.
Innovation Solution
An inverter control device that detects current and voltage patterns, selects appropriate switching timings within an electrical angle period to minimize current offsets by switching between upper and lower arm switches at optimal times, thereby reducing power fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the switching pattern is changed in the middle of one electrical angle period, then the inverter can adapt to different operating conditions, but current offsets and extremely low period fluctuation components occur in the output current
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple switching patterns in advance, each optimized for different operating conditions. The control device predicts future operating conditions and prepares the appropriate switching pattern beforehand, then smoothly transitions between patterns at predetermined timing points. This prevents current offsets and fluctuations by avoiding abrupt mid-period pattern changes.
Solution Approach 2:
The patent implements dynamics by making the switching pattern selection adaptive and time-varying. The control device dynamically selects which pre-calculated switching pattern to use based on real-time operating conditions (such as modulation ratio and frequency), and transitions between patterns at optimal timing points within each electrical angle period. This dynamic adaptation maintains output current stability while responding to changing conditions.
2Adaptability or versatility
If the switching pattern is changed to adapt to different conditions, then operational flexibility is improved, but fluctuations in output power increase due to current offsets
Solution Approach 1:
The control device pre-calculates switching patterns for various operating conditions and stores them in advance. When a pattern change is needed, the system transitions to a pre-prepared pattern at an optimal timing point within the electrical angle period, rather than making abrupt changes. This preliminary preparation ensures smooth transitions and prevents power fluctuations.
Solution Approach 2:
The patent changes the timing parameter of pattern transitions from arbitrary or mid-period points to specifically optimized timing points within the electrical angle period. By adjusting this timing parameter to optimal values, the system maintains output power stability while still adapting to different operating conditions through pattern changes.
3Ease of manufacture
If switching occurs at arbitrary timings, then implementation is simple, but current offsets occur and torque fluctuations increase in motor generators
Solution Approach 1:
The patent applies preliminary action by pre-calculating optimal switching timings and storing them in advance for different operating conditions. The control device simply retrieves and executes these pre-determined timings rather than calculating them in real-time, maintaining ease of implementation. The optimal timings are specifically designed to prevent current offsets and torque fluctuations.
Solution Approach 2:
The patent optimizes the switching timing parameter to specific values that eliminate torque fluctuations. Instead of using arbitrary timings, the system uses pre-determined optimal timing points within each electrical angle period. This parameter optimization maintains simplicity while eliminating harmful torque variations in motor generator applications.
Data Source
AI summary
A control device alternately turns on an upper arm switch and a lower arm switch constituting an inverter on the basis of an operation pattern that is a time-series pattern that defines a switching pattern for each of the upper arm switch and the lower arm switch. The control device detects each of a present pattern that is the operation pattern currently set and a next pattern that is the operation pattern to be set next time. A plurality of timings is set in the middle of the present pattern over one electrical angle period as candidates of switching from the present pattern to the next pattern, and the control device selects a command switching timing from among the plurality of timings. The control device switches the operation pattern from the present pattern to the next pattern at the selected command switching timing.