Power Converter Control for Unbalanced Short-Circuit Voltage Compensation
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Solution Overview
Problem
In power conversion systems, unbalanced short circuits can occur, necessitating effective voltage compensation to maintain system stability.
Innovation Solution
A control device for power conversion systems that includes conversion units for AC-side current and voltage conversion, a current command generator, and a limiter to set command values, ensuring the AC-side current does not exceed preset limits, with a controller to manage the power converter within these limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage compensation is performed during unbalanced short circuit, then system stability is improved, but AC-side current may exceed rated values
Solution Approach 1:
The control device dynamically adjusts control parameters based on the operating state. During unbalanced short circuit, the controller switches to a special control mode that dynamically modifies current command values and compensation amounts, allowing the system to adapt to changing conditions while preventing current from exceeding rated values
Solution Approach 2:
The invention changes control parameters based on the detected operating state. When unbalanced short circuit is detected, the system changes the voltage compensation amount and current control parameters to appropriate values, thereby maintaining system stability while preventing harmful current levels
2Reliability
If voltage compensation amount is increased to maintain system stability, then reliability is improved, but device complexity increases
Solution Approach 1:
The control device segments the control function into distinct operational modes. A determination unit identifies the operating state (normal or unbalanced short circuit), and different control strategies are applied accordingly. This segmentation allows effective voltage compensation without requiring a single complex control structure to handle all scenarios
Solution Approach 2:
The control device is designed with multi-functionality to handle both normal operation and unbalanced short circuit conditions using a unified control framework. The same control structure performs different functions based on the operating state, avoiding the need for separate complex control systems for each scenario
Data Source
AI summary
An elevator monitoring device that can compensate for system voltage when an unbalanced short circuit occurs. A control device for a power conversion device includes: a current command value generator configured to generate a provisional normal phase d-axis current command value, a provisional normal phase q-axis current command value, a provisional reversed phase d-axis current command value, and a provisional reversed phase q-axis current command value to compensate for an alternating current (AC)-side voltage of a power converter; a limiter configured to respectively set limit values of a provisional normal phase d-axis current command value, a provisional normal phase q-axis current command value, a provisional reversed phase d-axis current command value, and a provisional reversed phase q-axis current command value so that the AC-side current value of the power converter does not exceed a preset value; and a controller configured to control the power converter within the limit values.