Inverter Control Minimizing Switching Loss Across Power Factors
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Solution Overview
Problem
Existing inverter control systems face challenges in achieving a trade-off between switching loss and current total harmonic distortion (THD), with conventional discontinuous pulse width modulation schemes resulting in increased THD and higher switching loss, especially at low power factors.
Innovation Solution
A device for controlling an inverter that adjusts the discontinuous modulation duration using a command voltage transform unit and controller, which generates control signals based on comparisons between pole command voltages and a triangular carrier wave, allowing for the calculation of offset command voltages and virtual phase command voltages to minimize switching loss regardless of the power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a discontinuous pulse width modulation scheme is used to reduce switching loss, then switching loss is reduced, but current total harmonic distortion increases
Solution Approach 1:
The patent applies dynamics by making the discontinuous modulation duration adjustable rather than fixed. The controller dynamically adjusts the duration of the discontinuous modulation period based on operating conditions, allowing optimization of the trade-off between switching loss reduction and current THD control at different operating points
Solution Approach 2:
The patent changes the parameter of modulation duration from a fixed value to an adjustable parameter. By freely adjusting the discontinuous modulation duration parameter, the system can achieve optimal current THD and loss at each operating point, resolving the contradiction between reducing switching loss and controlling current distortion
2Object-generated harmful factors
If the discontinuous modulation duration is adjusted to optimize current THD, then current total harmonic distortion is reduced, but switching loss increases
Solution Approach 1:
The system dynamically adjusts the discontinuous modulation duration based on real-time operating conditions. The controller can switch between different modulation strategies (continuous or discontinuous) and adjust the duration accordingly, allowing optimization of the trade-off between current THD and switching loss at different operating points
3Loss of energy
If conventional discontinuous pulse width modulation is used, then switching loss is reduced, but the system does not achieve minimum loss at all power factors
Solution Approach 1:
The patent implements a dynamic control strategy where the controller adjusts the discontinuous modulation duration based on the power factor and operating conditions. This allows the system to achieve minimum loss at each operating point regardless of power factor, enhancing adaptability across varying load conditions
Solution Approach 2:
The system changes the modulation duration parameter dynamically to adapt to different power factors. By adjusting this parameter based on operating conditions, the system achieves optimal performance across a wide range of power factors, not just at unity power factor
Data Source
AI summary
Disclosed is a device for controlling an inverter. The device achieves a minimum switching loss in a discontinuous modulation duration regardless of a power factor. The device includes: a command voltage transform unit configured for transforming each of 3 phases command voltages into each of pole command voltages using the DC stage voltage, a pulse width modulation index, a discontinuous modulation angle corresponding to a discontinuous modulation duration, and each phase difference between each of the 3 phase command voltages and each of 3 phases output currents of the inverting module; and a controller configured for generating a control signal based on a comparison between each pole command voltage and a triangular carrier wave, wherein the control signal controls upper and lower switching elements of each phase leg.