Converter State Transition Control for Power Systems
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Solution Overview
Problem
In electrical power systems with multiple converters, delays in command signal transmission between control apparatuses can cause undesired large electrical currents to flow when switching states, leading to heat resistance deterioration.
Innovation Solution
The system generates command signals to change the state of one converter to an upper/lower arm OFF state before changing the other converter to an upper arm ON or boosting state, ensuring that one converter is not in an upper arm ON state when the other is in a boosting state, thereby preventing large current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If command signals are transmitted between control apparatuses to control multiple converters, then system coordination is achieved, but transmission delay causes large current flow during state transitions
Solution Approach 1:
The patent applies preliminary action by having the first control apparatus generate the command signal for the second converter in advance, before the actual state transition occurs. This allows the second converter to be prepared for its state change (to upper/lower arm OFF state) before the first converter transitions to upper arm ON state, thereby preventing large current flow during the transition period.
Solution Approach 2:
The patent segments the state transition process into distinct phases: first, the second converter transitions to upper/lower arm OFF state under control of the first control apparatus; then, after a predetermined time period, the first converter transitions to upper arm ON state. This temporal segmentation ensures that both converters are never in states that would cause large current flow simultaneously.
2Loss of energy
If converters switch between boosting state and upper arm ON state to reduce switching loss, then efficiency is improved, but heat resistance deterioration occurs during state changes
Solution Approach 1:
The patent applies preliminary action by preparing the second converter in advance (transitioning to upper/lower arm OFF state) before the first converter transitions to upper arm ON state. This prevents large current flow during state changes, thereby protecting the converters from heat resistance deterioration while maintaining the efficiency benefits of reduced switching loss.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a predetermined time period between the state transition of the second converter and the state transition of the first converter. This time buffer acts as a cushion that prevents harmful large current flow from occurring, protecting the converters from thermal stress while allowing efficient operation.
3Device complexity
If one control apparatus generates both command signals to reduce device complexity, then system structure is simplified, but control delay increases
Solution Approach 1:
The patent applies preliminary action by having the first control apparatus generate the command signal for the second converter in advance, before the actual state transition occurs. This compensates for the communication delay by提前 preparing the control signal, ensuring that the second converter is ready for its state change before the first converter transitions, thereby maintaining coordinated control despite the time delay.
Data Source
AI summary
A power system has a first control apparatus configured to generating a first command signal and a second command signal, to control the first converter on the basis of the first command signal, and to transmit the second command signal to a second control apparatus and the second control apparatus configured to control the second converter on the basis of the received second command signal. When it is requested that a state of each of the first and second converters is changed from a first state to a second state, the first control apparatus generates the first and second command signals so that the state of the second converter is changed to a third state in which both of the upper arm and the lower arm keep being in the OFF state, then the state of the first converter is changed from the first state to the second state, and then the state of the second converter is changed from the third state to the second state.