Series Resonant DC/DC Converter Control for Bidirectional Power Flow
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Solution Overview
Problem
Existing bidirectional DC/DC converters for UPS systems have limited operating ranges for high efficiency, particularly in zero voltage switching (ZVS) and zero current switching (ZCS), which restricts their effectiveness in varying load conditions and voltage ranges.
Innovation Solution
A method for controlling a series resonant DC/DC converter that defines specific switching periods and intervals for switches to achieve zero voltage switching at turn-on and nearly zero current switching at turn-off, with a fixed switching frequency close to the series resonant frequency, allowing for efficient power flow direction control and reduced component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate DC/DC converters are used for battery discharge and charging, then bidirectional power flow is achieved, but the number of components and system complexity increases
Solution Approach 1:
The patent designs a single DC/DC converter that performs both battery discharge and charging functions by controlling power flow direction through switching configuration. The same converter circuit handles both power transfer directions by adjusting the switching states of bridges and the polarity of voltage application to the tank circuit, eliminating the need for separate converters
Solution Approach 2:
The patent merges the battery discharge converter and battery charge converter into a single integrated DC/DC converter. The switching circuits and control logic are unified to handle both power flow directions, reducing component count and system complexity while maintaining full bidirectional functionality
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 enhances efficiency by maintaining ZVS and ZCS across a wide range of voltages and loads, reducing switching losses and improving overall performance, with efficiencies exceeding 96% in tested scenarios, compared to prior art.
Implementation Method 1
A resonant tank circuit is connected between the battery and the DC bus. The resonant tank circuit comprises a resonant inductor and a resonant capacitor
Implementation Method 2
controlling the switches of the first and second switching circuit to provide zero voltage switching at switch turn on
Implementation Method 3
provide nearly zero current switching at switch turn off
Data Source
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AI summary
The invention relates to a method for controlling a series resonant DC/DC converter. The method comprises the steps of: defining a switching period TP having a first half period TA and a second half period TB and defining a subsequent switching period TP+1 after the switching period TP. In a next step, a first set (S1sc1; S1sc1, S4sc1) of switches of a first switching circuit (SC1) is controlled to be ON from the beginning Tstart of the first half period TA minus a time interval ΔTAE1, where the time interval ΔTAE1 is provided at the end of the first half period TA and a second set(S2sc1; S2sc1, S3sc1) of switches of the first switching circuit (SC1) is controlled to be ON from the beginning Tcenter of the second half period TB minus a time interval ΔTBE1, where the time interval ΔTBE1 is provided at the end of the second half period TB. A first set (S1sc2; S1sc2, S4sc2) of switches of a second switching circuit (SC2) is controlled to be ON in the first half period TA minus a time interval ΔTAS1 and minus a time interval ΔTAE2, where the time interval ΔTAS1 is provided at the beginning of the first half period TA and where the time interval ΔTAE2 is provided at the end of the first half period TA and a second set (S2sc2; S2sc2, S3sc2) of switches of the second switching circuit (SC2) is controlled to be ON in the second half period TB minus time interval ΔTBS1 and minus time interval ΔTBE2, where the time interval ΔTBS1 is provided at the beginning of the second half period TB and where the time interval ΔTBE2 is provided in the end of the second half period TB. Time intervals Tsc1off1 and Tsc2off1, and time intervals Tsc1off2 and Tsc2off2, where the sets of the first and second switching circuits all are off, are at least partially overlapping.