DC/DC Converter Neutral-Point Voltage Balance Control
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Solution Overview
Problem
High-voltage DC/DC converters using 3-level circuits face challenges in neutral-point voltage balancing due to inconsistent hardware parameters, affecting device safety and operation, and existing control methods have poor regulation performance and uneven switching and conduction losses.
Innovation Solution
A control method for DC/DC converters that adjusts neutral-point voltage balance by selecting desired operating states of switches based on the voltage difference between capacitors and the direction of average current, using complementary square wave signals to reduce voltage differences and achieve symmetrical operating modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a 3-level circuit is used to achieve high-voltage input, then voltage levels are increased and wire loss is reduced, but neutral-point voltage becomes unbalanced due to inconsistent hardware parameters
Solution Approach 1:
The patent implements a control method that continuously monitors the neutral-point voltage and adjusts switching states based on detected voltage differences. The controller detects the voltage difference between the first and second capacitors and selects switching states to balance the neutral-point voltage, creating a closed-loop feedback system that maintains voltage balance despite hardware parameter inconsistencies
Solution Approach 2:
The patent dynamically selects switching states based on real-time voltage conditions rather than using fixed switching patterns. The controller adapts the switching strategy by detecting the voltage difference and current direction, then selecting appropriate switching states to balance the neutral-point voltage, making the system dynamically responsive to changing conditions
2Reliability
If existing control methods are used for neutral-point voltage regulation, then some regulation is achieved, but regulation performance is poor and switching losses are uneven
Solution Approach 1:
The patent applies asymmetric switching control where the switching states of the first and second bridge arms are not identical but are specifically selected to balance the neutral-point voltage. The controller selects different switching states for the two bridge arms based on the detected voltage difference and current direction, creating an asymmetric control strategy that achieves both voltage balance and reduced switching losses
Solution Approach 2:
The patent changes the switching parameters (switching states and duty cycles) based on real-time detection of voltage differences and current directions. The controller adjusts the switching strategy by selecting from different switching states depending on the operating conditions, dynamically changing parameters to optimize both voltage balance and energy efficiency
3Reliability
If neutral-point voltage is not balanced, then device safety and normal operation are affected, but implementing control adds system complexity
Solution Approach 1:
The patent makes the control system multi-functional by having the controller perform both power conversion control and neutral-point voltage balance control simultaneously. The same controller that manages the switching of the bridge arms also detects voltage differences and selects switching states for voltage balance, eliminating the need for separate control systems and reducing overall system complexity
Data Source
AI summary
The present disclosure provides a control method of a DC/DC converter and a related DC/DC converter. The control method allows for: detecting a difference between a first voltage and a second voltage; if an absolute value of the difference between the first voltage and the second voltage is greater than or equal to a preset value, reselecting desired operating states of respective switches in a 1-level state according to the difference between the first voltage and the second voltage and a direction of an average current from a fourth node to a first passive network in the 1-level state; and thus outputting a control signal to enable the voltage difference between the first capacitor and the second capacitor to be reduced, thereby effectively adjusting the neutral-point voltage balance of the DC/DC converter.