AC Voltage Regulation with Auxiliary Switch for Spike Reduction
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Solution Overview
Problem
Existing AC-to-AC voltage regulators using bi-directional switches with SCRs or thyristors suffer from high total-harmonics-distortion and voltage spikes due to line inductance, leading to electromagnetic interference and potential device destruction.
Innovation Solution
A power converter system employing a main bi-directional switch and an auxiliary bi-directional switch to control AC output voltage, with the auxiliary switch circulating reactive current and reducing voltage spikes through PWM control, allowing for controlled harmonics and reduced filter size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PWM control is used to chop the AC input waveform to reduce THD, then total-harmonics-distortion is reduced, but voltage spikes are generated across the transistors due to line inductance
Solution Approach 1:
The patent introduces an auxiliary bi-directional switch as an intermediary component connected in parallel with the main bi-directional switch. This auxiliary switch acts as a mediator that provides an alternative current path during switching transitions, thereby reducing the voltage spikes generated across the main switch due to line inductance when PWM chopping is applied to reduce THD.
Solution Approach 2:
The patent divides the single bi-directional switch into two separate bi-directional switches: a main bi-directional switch for primary voltage regulation and an auxiliary bi-directional switch for handling reactive current and reducing voltage spikes. This segmentation allows each switch to be optimized for its specific function, enabling PWM control to reduce THD while the auxiliary switch mitigates the resulting voltage spikes.
2Device complexity
If SCRs or thyristors are used for the bi-directional switch, then the device structure is simpler, but the control scheme is limited to single pulse leading edge control which generates very high THD
Solution Approach 1:
The patent changes the control parameters from single pulse leading edge control to PWM (pulse width modulation) control. This parameter change enables much lower THD by allowing multiple chopping cycles within each half-cycle of the AC waveform, providing finer control over the output voltage waveform and harmonic content.
Solution Approach 2:
The patent segments the control function by introducing an auxiliary bi-directional switch that handles reactive current circulation, allowing the main switch to focus on PWM-based voltage regulation. This segmentation enables the use of advanced PWM control schemes that would otherwise generate excessive voltage spikes and device stress.
3Manufacturing precision
If transistors are used for the bi-directional switch to enable PWM control, then THD is reduced, but voltage spikes cause electromagnetic interference and can destroy the transistors
Solution Approach 1:
The auxiliary bi-directional switch serves as a protective intermediary that absorbs the voltage spike energy generated during PWM switching transitions. By providing an alternative current path through the auxiliary switch, the main transistor is protected from destructive voltage spikes, thereby improving device reliability while maintaining the low-THD benefits of PWM control.
Solution Approach 2:
The patent implements a protective arrangement where the auxiliary bi-directional switch is pre-configured in parallel with the main switch. This beforehand cushioning ensures that when voltage spikes occur during PWM operation, the auxiliary switch is already in position to capture and dissipate the spike energy, preventing damage to the main transistor before it can occur.
Data Source
AI summary
In an embodiment, a power converter system is provided for AC voltage regulation. The power converter system receives an AC input voltage at an input terminal and provides an AC output voltage to a load at an output terminal. A main bi-directional switch is coupled between the input terminal and the output terminal. The main bi-directional switch is operable to control the provision of the AC output voltage. A reactive current flows through the main bi-directional switch if the load is reactive. An auxiliary bi-directional switch is coupled to the output terminal. The auxiliary bi-directional switch is operable to circulate the reactive current due to the reactive load, thereby reducing any voltage spikes in the power converter system.