ANPC Three-Level Converter Switching Sequence for Voltage Stress Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Active neutral-point clamped (ANPC) three-level converters face issues with excessive voltage stress on switches during startup and shutdown, leading to potential damage due to parasitic parameters and turned-off time differences, which existing control methods fail to adequately address.
Innovation Solution
A method and controller for ANPC three-level converters that control the sequential turning on and off of switches, including clamp switches, internal, and external switches, with specific delay times to manage voltage stress, ensuring safe operation and reducing switch damage by shortening the commutation loop path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If all switches are turned off at the same time when the converter stops operating, then the shutdown process is simple and fast, but the voltage stress on switches exceeds sustainable levels due to turned-off time differences and parasitic parameters
Solution Approach 1:
Before turning off all switches simultaneously, the method first turns off a subset of switches (first group) in advance, then after a predetermined time delay, turns off the remaining switches (second group). This preliminary action prevents excessive voltage stress by ensuring that not all switches are in the vulnerable turned-off state at the same time during shutdown.
Solution Approach 2:
The shutdown process segments the switch group into two subsets: first group switches and second group switches. These segments are turned off at different times with a predetermined delay between them, dividing the simultaneous switching action into sequential stages to reduce voltage stress on individual switches.
2Loss of time
If normal control signals of all switches are recovered at the same time when the converter starts operating, then the startup process is simple and fast, but the voltage stress on switches exceeds sustainable levels due to turned-off time differences and parasitic parameters
Solution Approach 1:
Before recovering normal control signals to all switches simultaneously, the method first recovers signals to a subset of switches (first group) in advance, then after a predetermined time delay, recovers signals to the remaining switches (second group). This preliminary action allows gradual buildup of switch conduction states, preventing excessive voltage stress during startup.
Solution Approach 2:
The startup process segments the switch group into two subsets: first group switches and second group switches. These segments have their control signals recovered at different times with a predetermined delay, dividing the simultaneous signal recovery into sequential stages to protect switches from voltage stress.
3Device complexity
If the commutation loop path is long during switching operations, then the circuit design is simpler, but the parasitic parameters cause excessive voltage stress on switches
Solution Approach 1:
The method optimizes the local quality of the commutation loop by ensuring that during switching operations, the current path passes through a shortened commutation loop with reduced parasitic inductance. This local optimization at critical switching nodes reduces voltage stress on switches without requiring complete redesign of the entire circuit.
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5d
AI summary
The present disclosure relates to an active neutral-point clamped (ANPC) three-level converter, and a method and controller for controlling thereof. The ANPC three-level converter includes at least one bridge leg, and a controller. Each of the at least one bridge leg includes multiple input terminals, an output terminal, and multiple switches connected between the multiple input terminals and the output terminal. The multiple input terminals include a first input terminal, a second input terminal, and a third input terminal. The multiple switches comprise a first external switch, a first internal switch, a first clamp switch, a second external switch, a second internal switch, and a second clamp switch. The method for controlling the NPC three-level converter includes a method for controlling the ANPC three-level converter to stop operating, and a method for controlling the ANPC three-level converter to start to operate.