Dual Capacitive Circuit Voltage Stabilization for Electric Machine Torque Control
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Solution Overview
Problem
The variation of direct voltage in capacitive circuits within electromechanical power transmission chains complicates the control of electric machines, leading to decreased operating efficiencies and maximum torques, especially when direct voltage is low.
Innovation Solution
A system comprising a first and second capacitive circuit with a direct voltage converter and a control system that maintains the first direct voltage constant while allowing the second direct voltage to fluctuate, using a control system to determine torque references based on the second direct voltage, power control signals, and rotational speed, thereby stabilizing the electric machine's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the capacitive circuit is used as an energy buffer to charge when low mechanical output power is needed and discharge when high mechanical output power is needed, then fuel costs are saved through improved combustion engine efficiency, but the direct voltage of the capacitive circuit varies which complicates control of electric machines and decreases operating efficiencies and maximum torques
Solution Approach 1:
The system divides the single capacitive circuit into two separate capacitive circuits: a first capacitive circuit whose voltage is maintained substantially constant for stable electric machine control, and a second capacitive circuit that fluctuates in voltage to serve as the energy buffer for peak power needs. This segmentation resolves the contradiction by assigning different functional roles to different capacitive circuits.
Solution Approach 2:
A direct voltage converter is introduced as an intermediary device between the first and second capacitive circuits. This converter transfers electric energy between the two circuits, allowing the second circuit to buffer energy while the first circuit maintains stable voltage. The intermediary enables the decoupling of the energy buffering function from the voltage stabilization function.
2Quantity of substance
If the direct voltage of the capacitive circuit is allowed to vary to buffer energy, then energy buffering capability is improved, but the magnetic fluxes in the electric machines become small which decreases operating efficiencies and maximum torques
Solution Approach 1:
The system segments the energy buffering function from the torque generation function by using two separate capacitive circuits. The second capacitive circuit handles energy buffering with voltage fluctuations, while the first capacitive circuit maintains constant voltage to ensure adequate magnetic fluxes and maximum torque in the electric machines.
Solution Approach 2:
The direct voltage converter acts as an intermediary that transfers energy from the second capacitive circuit to the first capacitive circuit when needed. This allows the system to utilize the energy buffer capacity of the second circuit while maintaining the voltage level required for maximum torque in the first circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach maintains stable direct voltage in the first capacitive circuit, preventing decreases in operating efficiency and maximum torque, and effectively uses the second capacitive circuit as an energy buffer to respond to peak power needs.
Implementation Method 1
converter equipment for transferring electric power between the first capacitive circuit and an electric machine, the converter equipment being configured to convert a first direct voltage of the first capacitive circuit into an output voltage
Implementation Method 2
a direct voltage converter for transferring electric energy between the first and the second capacitive circuits
Implementation Method 3
a second capacitive circuit comprising at least one second capacitor
Data Source
AI summary
An electric system of an electromechanical power transmission chain is provided that includes a first capacitive circuit, converter equipment between the first capacitive circuit and an electric machine, a second capacitive circuit, and a direct voltage converter between the first and second capacitive circuits. The electromechanical power transmission chain is a parallel transmission chain where the electric machine is mechanically connected to a combustion engine and to one or more actuators. The electric system includes a control system for controlling the direct voltage converter in response to changes in a first direct voltage of the first capacitive circuit and for controlling the converter equipment in response to changes in a second direct voltage of the second capacitive circuit. The first direct voltage is kept on a predetermined voltage range whereas the second direct voltage is allowed to fluctuate in order to respond to peak power needs.