Power Conversion Device Voltage Control Coordination
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Solution Overview
Problem
Existing power conversion devices fail to prioritize fundamental wave control functions over harmonic control functions, leading to limited performance in voltage-source inverters due to excessive output voltage growth with frequency, which affects voltage utilization rates.
Innovation Solution
A power conversion device with a control system that coordinates fundamental wave control functions and harmonic control functions, using separate circuits for current command generation and voltage command generation, including a limiting mechanism to prevent output voltage exceeding limits by estimating voltage increases and applying gain correction coefficients to harmonic current commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fundamental wave control functions and harmonic control functions are limited uniformly when inverter output capacity is exceeded, then the inverter output voltage is controlled within limits, but the performance of fundamental wave control functions deteriorates
Solution Approach 1:
The control functions are segmented into fundamental wave control functions and harmonic control functions. The limiting mechanism selectively applies limits only to harmonic control functions when output capacity is exceeded, while fundamental wave control functions continue to operate at full capacity. This segmentation resolves the contradiction by differentiating treatment between function types based on their priority and impact on system stability.
2Productivity
If the inverter output voltage is increased to accommodate higher frequency current command values, then harmonic control effectiveness is improved, but the voltage limit is exceeded
Solution Approach 1:
The limiting mechanism performs preliminary anti-action by detecting when the inverter output voltage approaches its limit before actual violation occurs. When voltage limits are approached, the mechanism preemptively limits the harmonic control functions' current command values, preventing the voltage from exceeding limits while maintaining the highest possible harmonic control effectiveness within available capacity.
3Object-generated harmful factors
If the inverter output capacity is fully utilized for harmonic control, then harmonic suppression is improved, but fundamental wave control performance is compromised
Solution Approach 1:
The limiting mechanism applies local quality by differentiating the treatment of different control functions based on their nature and priority. Fundamental wave control functions, which are critical for stable operation and have higher priority, are exempt from limiting even when capacity is exceeded. Harmonic control functions, which address harmful but less critical issues, are subject to limiting. This local differentiation ensures optimal allocation of limited inverter capacity.
Data Source
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AI summary
The present invention is designed to provide a power conversion device that is capable of controlling a voltage-source inverter by allowing fundamental wave control functions and harmonic control functions to operate in a coordinated way, and, at the same time, allowing fundamental wave control functions to operate preferentially. A power conversion device, which is inter-connected with a power system, has a fundamental wave control function circuit, which generates a first current command value for controlling the fundamental wave of a system current flowing in the power system, a harmonic control function circuit, which generates a second current command value for controlling harmonics of the system current, and a limiting circuit, which limits the second current command value according to the increase in the output voltage based on the second current command value, which is the output voltage for the power system.