Single-Phase Converter Control Neutral-Point Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Single-phase converters face challenges with unbalanced system neutral-point potential due to capacitance errors and switch device inconsistencies, leading to increased voltage stress on switching transistors and reduced system response speed.
Innovation Solution
A control method that calculates a common-mode modulated wave based on initial modulated waves from two bridge arms of the single-phase converter, adjusting the magnitude and slope of the common-mode component to improve neutral-point potential balancing, and adaptively adjusts the DPWM method to reduce time delay and enhance system reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a time delay link is used to generate orthogonal voltage vector, then the single-phase converter control can be implemented, but the system response speed is reduced and system delay increases
Solution Approach 1:
The patent extracts and removes the time delay link from the control system. Instead of using a time delay link to generate the orthogonal voltage vector, the patent directly calculates the common-mode component from the initial modulated waves of the two bridge arms, thereby eliminating the source of system delay and improving response speed while maintaining control functionality
Solution Approach 2:
The patent inverts the conventional approach by not generating the orthogonal voltage vector through time delay, but rather directly computing the common-mode component from the available initial modulated waves. This inversion of the control strategy eliminates the need for time delay operations while achieving the same control objective
2Device complexity
If conventional DPWM method is used without common-mode component injection, then the control is simple, but the system neutral-point potential is unbalanced and voltage stress on switching transistors increases
Solution Approach 1:
The patent introduces feedback by calculating the common-mode component based on the initial modulated waves and injecting it into the modulation process. This feedback mechanism dynamically adjusts the modulation waves to balance the neutral-point potential and distribute voltage stress evenly across switching transistors, improving reliability without excessive complexity
Solution Approach 2:
The patent changes the modulation parameters by injecting a common-mode component into the initial modulated waves. This parameter adjustment transforms the modulation process to achieve balanced neutral-point potential and reduced voltage stress on switching devices, maintaining control simplicity while enhancing reliability
3Reliability
If virtual third phase algorithm is used to generate common-mode component, then neutral-point potential balancing is achieved, but time delay increases and response speed decreases
Solution Approach 1:
The patent extracts and eliminates the virtual third phase algorithm from the control process. Instead of generating a virtual third phase to calculate the common-mode component, the patent directly computes the common-mode component from the initial modulated waves of the two bridge arms, removing the unnecessary computational steps and associated time delays
Solution Approach 2:
The patent applies partial action by using only the necessary information from the two bridge arms to calculate the common-mode component, rather than implementing the complete virtual third phase algorithm. This partial approach achieves the required neutral-point potential balancing without the excessive computational overhead and time delay
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Embodiments of this application disclose a single-phase converter control method and apparatus. The method includes: calculating on a voltage corresponding to a first level output by a single-phase converter, a voltage corresponding to a second level output by the single-phase converter, and a voltage reference value about the voltage corresponding to the first level and the voltage corresponding to the second level, to obtain a common-mode modulated-wave change rate of the single-phase converter, where the first level is a direct-current-side positive-bus level, and the second level is a direct-current-side negative-bus level; calculating on a first-phase initial modulated wave of the single-phase converter, a second-phase initial modulated wave of the single-phase converter, and the common-mode modulated-wave change rate, to obtain a common-mode modulated wave of the single-phase converter; and calculating on the first-phase initial modulated wave, the second-phase initial modulated wave, and the common-mode modulated wave, to obtain a pulse width modulated wave of the single-phase converter. According to the embodiments of this application, a system neutral-point potential balancing capability, a system response speed, and system reliability can be improved.