Power Network Circuit Between Inverter and Motor
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Solution Overview
Problem
Existing motor driving systems face limitations in increasing motor speed without requiring additional switches or increasing the DC-link voltage, leading to constraints in output voltage and voltage stress on switching elements.
Innovation Solution
A motor driving system with a power network circuit configured as a T-type impedance model, incorporating passive elements such as capacitors and inductors between the inverter and the motor, allowing for enhanced motor speed without additional switches or increased DC-link voltage, with the power network circuit designed to optimize impedance values for improved output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a boost converter is connected in series to increase DC-link voltage, then the maximum output voltage of the inverter is improved, but the volume and switching loss increase due to additional inductor and switch
Solution Approach 1:
A power network circuit comprising passive elements (inductors and capacitors) is introduced as an intermediary component between the inverter and motor. This circuit modifies the impedance characteristics to enable higher output voltage without requiring additional active switching components, thereby avoiding the volume and switching loss penalties associated with conventional boost converters
2Speed
If the DC-link voltage is increased to increase base speed, then the base speed increases, but the voltage stress of switching elements increases requiring redesign of driving circuit
Solution Approach 1:
The impedance parameters of the power network circuit are specifically designed and adjusted to achieve voltage boosting effect. By changing the impedance characteristics (inductance and capacitance values) of the passive elements, the circuit enables higher output voltage and base speed while maintaining the original DC-link voltage level, thus avoiding increased voltage stress on switching elements
3Device complexity
If a Z-source inverter is used to boost DC-link voltage with passive elements, then additional switches are avoided, but the inverter cannot use the voltage to its maximum due to shoot-through time limitation
Solution Approach 1:
The voltage boosting function is segmented from the inverter switching operation and implemented by a separate power network circuit with passive elements. This segmentation allows the inverter to operate without shoot-through constraints, as the impedance modification occurs in the external power network rather than within the inverter bridge itself, enabling full utilization of available voltage
Data Source
AI summary
Embodiments relate to a motor driving system comprising a power network between an inverter and a motor and a method for designing such motor drive system, the motor drive system comprising: an AC motor; an inverter unit for applying a voltage to the AC motor; a controller configured for controlling an output voltage of the inverter unit; and a power network circuit disposed between the inverter unit and the AC motor, wherein the power network circuit is configured with passive element.