Power Conversion Device Surge Voltage Suppression
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Solution Overview
Problem
Conventional power conversion devices for motor driving face challenges in effectively reducing surge voltage generated by parasitic inductance in three-phase inverter circuits, as parasitic inductance varies by configuration and phase, making it difficult to improve efficiency and reduce heat and loss.
Innovation Solution
A power conversion device calculates the surge voltage value for each phase based on parasitic inductance and motor current, identifying the phase with the maximum surge voltage and adjusting the switching elements' ON/OFF states to suppress switching, using a combination of sinusoidal and discontinuous modulation methods to control the three-phase inverter circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional PWM control is used with detailed timing adjustment of switching elements, then some surge voltage reduction is achieved, but the improvement is limited because parasitic inductance varies by configuration and phase
Solution Approach 1:
The control device calculates surge voltage values for each phase in advance based on parasitic inductance and phase current, identifies the phase with maximum surge voltage, and determines the timing to fix switching elements before the surge occurs. This preliminary calculation and timing determination enables proactive surge voltage suppression rather than reactive adjustment.
Solution Approach 2:
The invention dynamically changes the switching timing parameters based on calculated surge voltage values. By adjusting when switching elements are fixed (held in ON or OFF state) according to the identified maximum surge voltage phase, the system adapts to varying parasitic inductance conditions across different phases and configurations, achieving effective surge suppression.
2Productivity
If switching elements are frequently switched to maintain motor control, then motor performance is maintained, but heat generation and loss increase
Solution Approach 1:
The control device applies discontinuous modulation by periodically fixing switching elements in ON or OFF states during specific PWM periods, particularly when surge voltage is expected. This periodic holding of switching states reduces the frequency of switching operations compared to continuous PWM control, thereby reducing heat generation and energy loss while maintaining motor control performance through calculated timing adjustments.
3Loss of energy
If discontinuous modulation is applied to reduce switching loss, then efficiency improves, but surge voltage may increase due to fixed switching states
Solution Approach 1:
The invention dynamically adjusts the timing and duration of fixed switching states based on calculated surge voltage values for each phase. By changing these parameters adaptively rather than using fixed discontinuous modulation, the system reduces switching loss while preventing surge voltage increase through intelligent timing control that accounts for parasitic inductance variations.
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 effectively suppresses surge voltage by anticipating and managing the phase with the highest surge voltage, improving efficiency and reducing heat generation, particularly in complex motor systems like electric compressors.
Implementation Method 1
a parasitic inductance exists in the circuit, a high surge voltage is generated with ON and OFF of the switching element
Implementation Method 2
a three-phase inverter circuit having a plurality of switching elements to drive a motor
Data Source
AI summary
There is provided a power conversion device capable of effectively reducing a surge voltage generated by a parasitic inductance of a circuit. The power conversion device 1 is configured to operate a motor 8 driving a compression mechanism 7 of an electric compressor 16 by means of a three-phase inverter circuit 28 having a plurality of switching elements 18A to 18F. The power conversion device calculates a surge voltage value of each phase from a parasitic inductance of the circuit and phase currents iu, iv, and iw of the motor 8 to derive a phase in which the surge voltage value becomes maximum, and suppresses the switching of the switching elements 18A-18F of the phase having the maximum surge voltage value by a discontinuous modulation method.