DC Voltage Estimation for Inverter Pulsation Suppression
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Solution Overview
Problem
Existing power converting apparatuses struggle to precisely suppress output voltage pulsation in inverters, especially when dealing with single-phase AC power supplies, leading to torque pulsation and potential device failure due to the beat phenomenon.
Innovation Solution
A power converting apparatus that samples DC voltage values at specific intervals and calculates a DC voltage estimation value using a specific function, allowing for precise correction of the output voltage command to reduce pulsation, and is applicable to both single-phase and three-phase AC power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If DC voltage is detected in synchronism with carrier period, then detection timing is simplified, but it becomes impossible to detect DC voltage at sampling times unsynchronized with carrier frequency
Solution Approach 1:
The patent pre-calculates and stores correction values for DC voltage pulsation at multiple phase angles (0°, 60°, 120°, 180°, 240°, 300°) before actual operation. During runtime, the system selects the appropriate pre-calculated correction value based on the current phase angle, enabling flexible sampling at any timing without requiring real-time synchronization calculations.
2Device complexity
If DC voltage is estimated from preceding and present detected values, then calculation is simplified, but large errors occur in estimated values causing imprecise pulsation suppression
Solution Approach 1:
The system calculates DC voltage pulsation correction values by comparing detected DC voltage values with ideal DC voltage values at multiple phase angles. The correction values are stored and applied to compensate for pulsation effects, continuously improving accuracy through feedback from actual measurements.
Solution Approach 2:
Correction values for DC voltage pulsation are pre-calculated and stored in memory at six different phase angles (0°, 60°, 120°, 180°, 240°, 300°). During operation, the appropriate pre-calculated correction value is selected based on the current phase angle, providing accurate compensation without requiring complex real-time calculations.
3Reliability
If inverter output voltage correction is applied to three-phase AC power supply, then output voltage pulsation is suppressed, but beat phenomenon occurs when applied to single-phase AC power supply causing torque pulsation and potential device failure
Solution Approach 1:
The patent applies different correction strategies based on the specific phase angle within the AC cycle. By dividing the correction approach into localized segments (six 60° intervals), the system can apply appropriate correction values for each phase region, preventing the beat phenomenon while maintaining pulsation suppression effectiveness.
Solution Approach 2:
The system changes the correction parameter (correction value) based on the phase angle of the AC power supply. By selecting from pre-calculated correction values corresponding to different phase angles (0°, 60°, 120°, 180°, 240°, 300°), the system adapts the correction strategy to match the instantaneous state of the AC supply, eliminating the beat phenomenon condition.
Data Source
AI summary
A detected DC voltage value estimation mechanism samples detected DC voltage values at specific intervals of a period T, stores detected DC voltage values Vn to Vn−m detected at a present time tn up to a sampling time tn−m which is m sampling cycles (m≧1) before the present time tn, and calculates a DC voltage estimation value Vn+1 at a next time tn+1 using the detected DC voltage values Vn to Vn−m, expressing a curve connecting the voltage values Vn to Vn−m by a specific function. An output voltage control into which the DC voltage estimation value Vn+1 is input corrects an output voltage command value and outputs the corrected output voltage command value to a power converter.