Solid State Transformer Control for Decoupled Energy Balancing
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Solution Overview
Problem
Conventional control architectures for solid state transformers (SSTs) face challenges in managing multiple state variables, leading to interference between converters, requiring complex voltage balancing and power sharing mechanisms, and necessitating large capacitors and filtering, which complicates the control system.
Innovation Solution
A fully decoupled control system for SSTs, comprising a stored energy controller, power flow controller, and energy balancing controllers, each operating independently to manage energy and power flow, eliminating the need for voltage balancing and power sharing, and actively removing voltage ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional control architecture based on the actual power path is used, then the control system can manage power flow, but it creates interferences between converters and requires complex voltage balancing and power sharing mechanisms
Solution Approach 1:
The control system is segmented into three independent controllers: stored energy controller, power flow controller, and energy balancing controller. Each controller manages a specific function independently, eliminating the need for complex voltage balancing and power sharing mechanisms while maintaining control stability.
Solution Approach 2:
The patent introduces virtual power flow as an intermediary concept that decouples the control architecture from the actual power path. This allows controllers to operate independently without direct interference, simplifying the overall control system while maintaining reliability.
2Stability of the object's composition
If voltage balancing algorithms and current sharing mechanisms are implemented, then capacitor voltages can be balanced and power distributed equally, but the controller coupling increases system complexity
Solution Approach 1:
The control functions are segmented into independent modules: the stored energy controller manages total capacitor voltage, while energy balancing controllers handle individual DC-to-DC converter operations. This segmentation eliminates the need for complex voltage balancing algorithms and current sharing mechanisms, reducing controller coupling while maintaining voltage stability.
3Stability of the object's composition
If capacitor voltage ripple filtering is applied, then voltage ripples are removed before feedback, but capacitor size must be increased and filtering mechanism complexity increases
Solution Approach 1:
The patent extracts and removes the harmful voltage ripple component through the stored energy controller, which actively manages total stored energy in capacitors. This eliminates the need for additional filtering mechanisms while maintaining voltage stability, avoiding both capacitor size increase and filtering complexity.
Solution Approach 2:
The control system uses feedback from capacitor voltage measurements to adjust the stored energy controller's operation. By measuring actual capacitor voltages and adjusting power flow accordingly, the system maintains voltage stability without requiring complex filtering mechanisms or increased capacitor sizes.
Data Source
AI summary
A decoupled system for controlling a solid state transformer (SST), the SST comprising an AC-to-DC stage, a DC-to-AC stage, and a DC-to-DC stage, the DC-to-DC stage comprising one or more DC-to-DC converters. The system comprises a stored energy controller coupled to the AC-to-DC stage, the energy controller configured to control the total amount of stored energy within the capacitors of the SST; a power flow controller coupled to the DC-to-AC stage, the power flow controller configured to control power flow in the SST; and one or more energy balancing controllers each coupled to a corresponding DC-to-DC converter, each energy balancing controller configured to balance energy in the corresponding DC-to-DC converter.