Bidirectional Power Conversion Circuit for Noise-Robust Switching
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Solution Overview
Problem
Noise superimposed on phase voltages in power conversion circuits can cause a shift in the timing of ON/OFF control of switch devices, leading to currents flowing through unintended paths.
Innovation Solution
A power conversion circuit with bidirectional switches and a controller that controls the switches to prevent overlap in ON/OFF states, ensuring current flow only through intended paths by using specific phase control periods and space vector pulse width modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ON/OFF control is performed based on magnitude relationship between three-phase voltages, then power conversion efficiency is improved, but noise superimposed on phase voltages causes timing shift leading to current flowing through unintended paths
Solution Approach 1:
The controller determines a specific period in advance based on the phase of the first voltage before performing ON/OFF control. By pre-defining the time window for switching operations, the controller ensures that even if noise causes voltage measurement fluctuations, the switching timing remains within the predetermined safe period, preventing current from flowing through unintended paths.
Solution Approach 2:
The patent introduces an intermediate control mechanism where the controller first determines a specific period based on phase voltage, then performs ON/OFF control within that period. This intermediate time-window determination acts as a mediator between the voltage magnitude detection and the actual switching action, filtering out the effect of noise on timing accuracy.
2Reliability
If switching timing is adjusted to compensate for noise, then current path accuracy is improved, but switching timing becomes complex requiring precise period determination
Solution Approach 1:
The controller changes the control parameter from direct instantaneous voltage comparison to a time-window-based approach. By determining a specific period based on the phase of the first voltage and confining switching operations within this period, the control method simplifies the timing logic while maintaining accuracy, avoiding complex real-time noise compensation calculations.
3Reliability
If bidirectional switches are controlled with precise timing, then unintended current flow is prevented, but control logic becomes more complex
Solution Approach 1:
The control period is segmented into a specifically determined time window based on the phase of the first voltage. By dividing the switching control into this predetermined period, the controller simplifies the logic for managing bidirectional switches, ensuring that switching operations only occur within the safe time window when the first voltage has the appropriate phase, thereby preventing unintended current flow without requiring complex inter-switch coordination logic.
Data Source
AI summary
A power conversion circuit includes first, second, and third input terminals for receiving three-phase AC voltages, a pair of output terminals, multiple bidirectional switches, and a control circuit. During a predetermined period proximate to a time when the magnitude relationship between the second and third voltages is transposing, the control circuit manages the second and third low-side bidirectional switches to prevent an overlap between specific conductive states. Concurrently, the control circuit controls the second and third high-side switches to also prevent an overlap between their respective conductive states. By preventing overlap between states, a short-circuit current does not flow through an unintended current path.