Variable Speed Drive Cell Activation for Power Loss Reduction
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Solution Overview
Problem
Variable speed drives supplying power to electric motors often operate suboptimally due to unnecessary activation of power cells, leading to increased losses, thermal issues, and imperfection impacts on output voltage, especially at low speeds or when high voltages are required, and there is a need to optimize the use of power cells to ensure continuous and full voltage supply.
Innovation Solution
A method that dynamically adjusts the number of active power cells based on the target voltage determined by the speed command, deactivating unnecessary cells to minimize losses and improve thermal management, while ensuring balanced voltages across phases and optimizing power cell usage by selecting cells based on operating time criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If all power cells are activated to supply high voltage, then the full voltage capability is maintained, but power losses increase and thermal state deteriorates at low speed operation
Solution Approach 1:
The patent implements dynamic adjustment of the number of active power cells based on real-time operating conditions. The control system continuously monitors speed commands and adjusts the count of active power cells accordingly - using fewer cells at low speeds and all cells at high speeds, making the system adaptable rather than static
Solution Approach 2:
The patent changes the operational parameters of the power cells by varying the number of active cells based on the speed command. This parameter adjustment allows the system to optimize performance across different operating ranges, reducing power losses when full voltage capability is not required
2Power
If all power cells are activated, then full voltage is supplied, but thermal state of the variable speed drive worsens
Solution Approach 1:
The system dynamically adjusts the number of active power cells based on operational requirements. When high voltage is needed, all cells are activated; when lower voltage suffices, fewer cells remain active, thereby dynamically managing thermal load
Solution Approach 2:
The patent varies the operational parameter of active cell count to manage thermal state. By reducing the number of active cells when full power is not required, the system reduces heat generation and improves thermal management
3Loss of energy
If power cells are deactivated to reduce losses, then power efficiency improves, but voltage supply capability may be insufficient
Solution Approach 1:
The control system uses feedback from the speed command to determine the appropriate number of active power cells. This closed-loop approach ensures that sufficient voltage capability is maintained while optimizing efficiency, as the system continuously adapts to operational requirements
Solution Approach 2:
The system dynamically adjusts power cell activation based on real-time speed commands, ensuring that the voltage supply capability matches the actual operational needs rather than operating at fixed capacity
4Reliability
If N+1 or N+2 configurations are used to ensure continuous supply, then reliability improves, but device complexity increases
Solution Approach 1:
The patent implements dynamic management of power cell activation states, allowing the system to adaptively respond to failures or operational requirements. This dynamic approach provides reliability flexibility without permanently increasing hardware complexity
Solution Approach 2:
The system changes operational parameters (active cell count) rather than hardware configuration, allowing flexible reliability management through control strategies rather than fixed N+1 or N+2 hardware arrangements
Data Source
AI summary
A method for controlling a variable speed drive supplying power to an electric motor, the variable speed drive comprising a plurality of at least Ni low-voltage power cells connected in series, comprising:upon reception of a speed command, determining a number Mi of cells sufficient to supply power to the motor at a target voltage V that is determined based on the speed command; andactivating the Mi power cells from among the Ni power cells, and deactivating the Ni-Mi other power cells in order to supply power to the motor in accordance with the speed command.