Auxiliary resonant DC tank converter
First Claim
1. An auxiliary resonant dc tank converter, comprising:
- an ac power supply and an ac bus;
a dc power supply for providing dc current to a dc bus;
an inverter having at least one phase leg connected to said ac bus and connected across said dc bus, said inverter having at least one main switching device per phase leg; and
a resonant dc tank circuit coupled in parallel with said dc power supply for generating a resonant voltage across said dc bus, said resonant dc tank circuit including;
an upper resonant capacitor and a lower resonant capacitor connected in series as a resonant leg,a first dc tank capacitor and a second dc tank capacitor connected in series as a tank leg, andan auxiliary resonant circuit, said auxiliary resonant circuit being coupled across the junction of said upper and lower resonant capacitors and the junction of said first and second dc tank capacitors, said lower resonant capacitor being coupled across said dc bus, said resonant leg being coupled across said tank leg.
1 Assignment
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Accused Products
Abstract
An auxiliary resonant dc tank (ARDCT) converter is provided for achieving soft-switching in a power converter. An ARDCT circuit is coupled directly across a dc bus to the inverter to generate a resonant dc bus voltage, including upper and lower resonant capacitors connected in series as a resonant leg, first and second dc tank capacitors connected in series as a tank leg, and an auxiliary resonant circuit comprising a series combination of a resonant inductor and a pair of auxiliary switching devices. The ARDCT circuit further includes first clamping means for holding the resonant dc bus voltage to the dc tank voltage of the tank leg, and second clamping means for clamping the resonant dc bus voltage to zero during a resonant period. The ARDCT circuit resonantly brings the dc bus voltage to zero in order to provide a zero-voltage switching opportunity for the inverter, then quickly rebounds the dc bus voltage back to the dc tank voltage after the inverter changes state. The auxiliary switching devices are turned on and off under zero-current conditions. The ARDCT circuit only absorbs ripples of the inverter dc bus current, thus having less current stress. In addition, since the ARDCT circuit is coupled in parallel with the dc power supply and the inverter for merely assisting soft-switching of the inverter without participating in real dc power transmission and power conversion, malfunction and failure of the tank circuit will not affect the functional operation of the inverter; thus a highly reliable converter system is expected.
35 Citations
19 Claims
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1. An auxiliary resonant dc tank converter, comprising:
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an ac power supply and an ac bus; a dc power supply for providing dc current to a dc bus; an inverter having at least one phase leg connected to said ac bus and connected across said dc bus, said inverter having at least one main switching device per phase leg; and a resonant dc tank circuit coupled in parallel with said dc power supply for generating a resonant voltage across said dc bus, said resonant dc tank circuit including; an upper resonant capacitor and a lower resonant capacitor connected in series as a resonant leg, a first dc tank capacitor and a second dc tank capacitor connected in series as a tank leg, and an auxiliary resonant circuit, said auxiliary resonant circuit being coupled across the junction of said upper and lower resonant capacitors and the junction of said first and second dc tank capacitors, said lower resonant capacitor being coupled across said dc bus, said resonant leg being coupled across said tank leg. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. In a resonant dc tank converter having a resonant dc tank circuit for generating a resonant voltage across a dc bus, said resonant dc tank circuit including upper and lower resonant capacitors connected in series as a resonant leg, first and second dc tank capacitors connected in series as a tank leg, and an auxiliary resonant circuit comprising a series combination of a resonant inductor and auxiliary switching means, said auxiliary resonant circuit being coupled across the junction of said upper and lower resonant capacitors and the junction of said first and second dc tank capacitors, said lower resonant capacitor being coupled across said dc bus, said resonant leg being coupled across said tank leg, said resonant dc tank circuit further including first clamping means for limiting the dc bus voltage to the tank voltage of said tank capacitors and second clamping means for clamping the resonant dc bus voltage to zero during a resonant period, said first clamping means comprising a clamp switching device with an anti-parallel clamping diode, a control method comprising the steps of:
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turning on said auxiliary resonant circuit to establish a resonant current to a specific level for assisting resonance of said dc bus from the dc tank voltage of said dc tank leg to zero when said clamping diode conducts or when a relatively low current flows through said clamp switching device; gating off said clamp switching device when said resonant current reaches a specific level or when a high current flows through said clamp switching device to start a resonance on said dc bus; clamping said dc bus to zero voltage using said second clamping means; turning on main switching devices of said inverter when a reverse resonant current is needed to boost the resonant dc bus voltage back to the dc tank voltage; maintaining said auxiliary resonant circuit on until said reverse resonant current reaches a specific level; changing state of said inverter to a predetermined setting; allowing said dc bus to resonate back to the tank voltage of said dc tank leg; turning on said clamp switching device after the voltage of said dc bus reaches the tank voltage of said dc tank leg; and turning off said auxiliary resonant circuit when the resonant current through said resonant inductor is substantially zero.
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Specification