Scalable single-stage differential power converter
View Patent ↗An embodiment of the invention is a scalable single stage differential power converter. The inverter can be implemented in signal, split and multi-phases. A multiphase converter can be achieved with only three modules. Integrated magnetics used in preferred embodiments of the invention mitigate the DC component of the steady-state dynamics and can be extended to AC ripple mitigation. Control architectures in preferred embodiments can mitigate higher order harmonics in steady state dynamics. Embodiments of the invention also provide scalability for voltage and current source topologies.
1. A single-stage DC/AC power converter, comprising:
at least two bi-directional converter modules connected in differential configuration, each of said two bi-directional converter modules having primary and secondary sides separated by transformers and including inductors for current flow and energy storage, wherein each of the two bi-directional converter modules comprises transformers and inductors that are integrated on one or more cores;
switches controlling current flow in the primary and secondary sides to create positive and negative half cycle AC current to an output on said secondary side from a DC power source on said primary side or controlling current flow in the primary and secondary sides to create AC output on said primary/secondary side from an AC power source on said secondary/primary side;
a loop controller having an outer voltage loop and an inner current loop with a first modulator that controls modulation of said switches via a second modulator referenced by said inner current loop, wherein one or both of said outer voltage loop and said inner current loop include a fundamental frequency compensator and a plurality of harmonic frequency compensators, and further including different fundamental and harmonic voltage loop references for outer loop control.
2. The power converter of claim 1 , wherein said converter modules comprise isolated Ćuk converters.
3. The power converter of claim 1 , wherein said converter modules comprise a voltage-source topology.
4. The power converted of claim 1 , wherein said converter modules comprise a current-source topology.
5. The power converter of claim 1 , wherein said converter comprise two converter modules and said switches are controlled by said controller to output single-phase AC power.
6. The power converter of claim 1 , wherein said harmonic-voltage-loop control references are set to zero for sinusoidal output or set to desired reference values for non-sinusoidal output.
7. The power converter of claim 1 , wherein the fundamental and harmonic voltage loop references are compared with voltage feedback from said converter modules and resultant error signal provide current references to compensators of said inner current loop.
8. The power converter of claim 1 , wherein the control loop compensation can be linear and/or nonlinear and wherein control loop execution can be in time-varying and/or time-invariant reference frame(s).
9. The power converter of claim 1 , wherein said converter with each module having a transformer center tap and said switches being controlled by said controller to output split-phase AC power.
10. The power converter of claim 1 , wherein said converter comprise three converter modules and said switches are controlled by said controller to output three phase AC power.
11. The power converter of claim 1 , wherein said converter comprise N (with N>2) converter modules and said switches are controlled by said controller to output N-phase AC power.
12. The power converter of claim 1 , wherein the transformers and inductors of both of the converter modules are integrated on one or more core.
13. The power converter of claim 1 , further comprising a loss-mitigating snubbing network applied across the primary- and/or secondary-side switches to reduce device voltage stress and voltage spike and recover energy stored in transformer leakage inductance.
14. The power converter of claim 1 ,
wherein said outer voltage loop includes a DC compensator or includes a DC compensator and a plurality of harmonic frequency compensators and said inner current loop includes a fundamental frequency compensator and a plurality of harmonic frequency compensators.
15. A method of converting power, the method comprising:
inputting power to a plurality of separate converter modules from a power source;
generating an output across each of the plurality of separate converter modules, wherein one of the input and the output has a DC component and an AC component; and
controlling switching of the plurality of separate converter modules to be out of phase such that a difference of the outputs eliminates DC harmonics and retains a desired AC signal, wherein said controlling comprises compensating desired fundamental frequency with a fundamental frequency voltage reference and compensating harmonic frequency with a harmonic frequency reference set to zero by comparing to a voltage feedback from the converter modules, and then setting current references for a current compensators with the outputs from the voltage comparisons, and driving a modulator for switches in said converter modules from the current compensators.
16. The method of claim 14 ,
wherein the output and the input have a DC component and an AC component; and
wherein said controlling controls switching such that the input current is ensured to be sinusoidal or harmonic-specific.