Inverter Voltage Modulator Selects PWM Based on Vector Position
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Solution Overview
Problem
Existing motor inverter control methods, such as SVPWM and DPWM, face inefficiencies due to increased switching losses and current ripples, necessitating a more effective pulse width modulation technique.
Innovation Solution
An apparatus and method that selectively apply modulation methods based on the position of a voltage reference in a hexagonal space voltage vector diagram, using a current controller to generate d/q-axis voltage references and a voltage modulator to choose between DPWM and SVPWM, reducing switching times and current ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If SVPWM method is used, then current ripple performance is improved, but switching losses increase due to increased number of switching times
Solution Approach 1:
The patent dynamically selects between SVPWM and DPWM methods based on the position of the voltage reference vector in the hexagonal space voltage vector diagram. When the voltage reference is near the center, DPWM is selected to reduce switching losses. When the voltage reference is far from the center, SVPWM is selected to maintain current ripple performance. This dynamic selection resolves the contradiction by adapting the modulation method to operating conditions.
Solution Approach 2:
The patent changes the modulation method parameter based on the voltage reference position. By calculating the distance of the voltage reference from the center of the hexagon and comparing it with a threshold, the system switches between DPWM and SVPWM methods. This parameter-based selection allows optimization of both switching losses and current ripple performance under different operating conditions.
2Loss of energy
If DPWM method is used, then switching losses are reduced, but current ripple magnitude increases
Solution Approach 1:
The system dynamically switches between DPWM and SVPWM based on voltage reference position. DPWM is applied when the voltage reference is near the center (within threshold distance), where it effectively reduces switching losses. When the voltage reference moves away from the center, the system transitions to SVPWM to maintain acceptable current ripple performance. This dynamic adaptation resolves the contradiction between switching loss reduction and current ripple control.
Solution Approach 2:
The patent uses the distance parameter of the voltage reference from the hexagon center as a decision criterion. When this distance parameter is below a threshold, DPWM is selected to minimize switching losses. When the distance exceeds the threshold, SVPWM is selected to maintain current ripple performance. This parameter-based switching resolves the contradiction by optimizing for different performance aspects under different operating conditions.
3Object-generated harmful factors
If SVPWM is used throughout, then current ripple is controlled, but inverter efficiency decreases due to increased switching times
Solution Approach 1:
The patent implements dynamic modulation method selection based on voltage reference position. Instead of using SVPWM universally, the system switches to DPWM when the voltage reference is near the center of the hexagon, where DPWM provides equivalent current ripple control with fewer switching times. This dynamic selection improves inverter efficiency while maintaining current ripple control where applicable.
Solution Approach 2:
The system changes the modulation method parameter based on the voltage reference position parameter. By calculating the distance from the hexagon center and comparing with a threshold, the system selects DPWM for central regions (improving efficiency) and SVPWM for outer regions (maintaining ripple control). This parameter-based approach resolves the contradiction between efficiency and ripple control.
4Productivity
If DPWM is used throughout, then switching times are reduced, but current ripple becomes larger than SVPWM
Solution Approach 1:
The patent dynamically adjusts the modulation method based on voltage reference position. DPWM is applied only in regions where it maintains acceptable current ripple performance (near the center). In regions where DPWM would cause excessive ripple (far from center), the system switches to SVPWM. This dynamic adjustment maintains inverter efficiency while preventing current ripple from becoming excessively large.
Solution Approach 2:
The system uses the voltage reference position parameter to determine the appropriate modulation method. When the position parameter indicates proximity to the hexagon center, DPWM is selected for efficiency. When the position parameter indicates distance from the center, SVPWM is selected to limit current ripple. This parameter-based switching resolves the contradiction between efficiency improvement and current ripple control.
Data Source
AI summary
An apparatus for controlling an inverter for a motor driving includes: a current controller configured to generate a d/q-axis voltage reference for allowing a d/q-axis current detection value, which is obtained by measuring a current supplied from the inverter to the motor, to converge on the d/q-axis current reference for driving the motor, and a voltage modulator configured to control switching of the inverter by selectively applying one among a plurality of predetermined pulse width modulations (PWM) based on a point at which the d/q-axis voltage reference is located in a hexagonal space voltage vector diagram.