US-12620903-B2 - Systems and methods for stacked multi-level power converter implementations with linear scaling

US12620903B2US 12620903 B2US12620903 B2US 12620903B2US-12620903-B2

Abstract

Disclosed are methods, systems, devices, and other implementations, including a voltage converter system that includes a plurality of energy storage elements, a plurality of switching devices, each of which is in electrical communication with at least one of the plurality of the storage elements, with the plurality of storage elements and the plurality of switching devices being configured in a multi-level arrangement of multiple voltage converting cells. The system further includes a plurality of controllers to actuate one or more of the plurality of switching devices to independently control voltage levels of at least one energy storage element of the multiple voltage converting cells. In some embodiments, the cells may include an arrangement of two capacitors and an inductor that define a buck-boost converter circuit. Alternatively, the cells may have a Dual Active Half Bridge (DAHB) converter configuration with a primary side separated from a secondary side by a transformer.

Inventors

Matthias Preindl
Matthew Jahnes

Assignees

THE TRUSTEES OF COLUMBIA UNIVERSITY IN THE CITY OF NEW YORK

Dates

Publication Date: 20260505
Application Date: 20230831

Claims (20)

1 . A voltage converter system comprising: a plurality of energy storage elements; a plurality of switching devices, each in electrical communication with at least one of the plurality of the energy storage elements, wherein the plurality of energy storage elements and the plurality of switching devices are configured in a multi-level arrangement of multiple voltage converting cells; and a plurality of controllers to controllably actuate one or more of the plurality of switching devices to independently control voltage levels of at least one energy storage element of the multiple voltage converting cells.
2 . The voltage converter system of claim 1 , wherein each of the multiple voltage converting cells comprises an arrangement of two capacitors and an inductor that define a buck-boost converter circuit.
3 . The voltage converter system of claim 1 , wherein the multiple voltage converting cells are arranged as one or more stacked cascades of converting cells, with each voltage converting cell in the one or more stacked cascades of conversion cells sharing at least one capacitor element with a neighboring voltage converting cell.
4 . The voltage converter system of claim 1 , wherein the plurality of controllers configured to independently control the voltage levels of the at least one energy storage element of each of the multiple voltage converting cells is configured to achieve a voltage balance for the multiple voltage converting cells.
5 . The voltage converter system of claim 1 , wherein the plurality of controllers, configured to independently control the voltage levels of the at least one energy storage element of the each of the multiple voltage converting cells, is configured to determine and maintain at least one capacitor of the multiple voltage converting cells at a respective voltage level.
6 . The voltage converter system of claim 1 , wherein the plurality of controllers configured to controllably actuate the one or more of the plurality of switching devices is configured to controllably actuate the one or more of the plurality of switching devices based at least in part on measured electrical properties of at least one of the multiple voltage converting cells.
7 . The voltage converter system of claim 6 , wherein the plurality of controllers is configured to actuate the one or more of the plurality of switching devices according to a voltage level measured across at least one of the plurality energy storage elements.
8 . The voltage converter system of claim 1 , wherein the plurality of controllers configured to controllably actuate the one or more of the plurality of switching devices includes at least one controller configured to determine an adjustable duty cycle behavior for at least one of the multiple voltage converting cells.
9 . The voltage converter system of claim 8 , wherein the at least one controller configured to determine the adjustable duty cycle behavior for the at least one of the multiple voltage converting cells is configured to continually compute the duty cycle behavior for the at least one of the multiple voltage converting cells that achieves a pre-determined output voltage for the voltage converter system, with other of the multiple voltage converting cells, excluding the at least one of the multiple voltage converting cells, configured with respective substantially fixed duty cycle values.
10 . The voltage converter system of claim 8 , wherein the plurality of controllers configured to determine the adjustable duty cycle behavior for the at least one of the multiple voltage converting cells is configured to derive duty cycle characteristics for the multiple voltage converting cells to achieve a desired output voltage for the voltage converter system that optimizes one or more objective functions.
11 . The voltage converter system of claim 10 , wherein the one or more objective functions includes one or more of: a) 1-norm objective function of all inductor currents in the voltage converter system to minimize overall current rating of the voltage converter system, b) a 2-norm squared objective function of all the inductor currents of the voltage converter system to minimize overall power loss in the voltage converter system, or c) an inf-norm objective function of all the inductor currents of the voltage converter system to minimize maximum currents levels in all the inductor currents.
12 . The voltage converter system of claim 1 , wherein at least one of the multiple voltage converting cells comprises a Dual Active Half Bridge (DAHB) converter configuration cell that includes a primary side and a secondary side separated from the primary side by a transformer, with the primary side including one or more primary side energy storage elements and one or more primary side switches, and with the secondary side including one or more secondary side energy storage elements and one or more secondary side switching devices.
13 . The voltage converter system of claim 12 , wherein the at least one DAHB converter configuration cell includes two primary side capacitors, two primary side controllable switching devices, two secondary side capacitors, and two secondary side switching devices.
14 . The voltage converter system of claim 13 , wherein the plurality of controllers configured to independently control the voltage levels of the at least one energy storage element of each of the multiple voltage converting cells includes at least one dedicated controller for the at least one DAHB converter configuration cell, the at least one dedicated controller configured to controllably actuate the two primary side switching devices and the two secondary side switching devices according to one or more pre-determined switching sequences defined for a particular time interval.
15 . The voltage converter system of claim 14 , wherein the one or more switching sequences for the at least one DAHB converter configuration cell is defined by duty cycles for the primary side and for the secondary side, and by a phase shift, φ, between a primary side and a secondary side switching events.
16 . The voltage converter system of claim 12 , wherein the multiple voltage converting cells each includes a respective cell with the DAHB converter configuration cell, and wherein the multiple voltage converting cells are arranged as one or more stacked cascades of the cells with the DAHB converter configuration cell connected to a load.
17 . The voltage converter system of claim 1 , wherein the multi-level arrangement of the multiple voltage converting cells comprises a plurality of voltage converting cells arranged in multiple stacks of voltage converting cells connected to a load, and wherein the plurality of controllers comprises a central controller in electrical communication with the multiple stacks of voltage converting cells to control electrical currents produced by the multiple stacks to power the load.
18 . The voltage converter system of claim 17 , wherein the load comprises a multi-phase motor, with each of the multiple stacks of voltage converter cells providing a respective phased current for one of multi-phase inputs of the multi-phase motors, and wherein the central controller is configured to control duty cycles of one or more switching devices in the multiple stacks to produce the multi-phase currents that result in one or more of a specified motor speed or a specified motor torque.
19 . The voltage converter of claim 17 , wherein the plurality of controllers comprises an individual cell controller for each of the multiple voltage converting cells, with the each of the multiple voltage converting cells comprising two capacitors, two switching devices, and an inductor element arranged in a buck-boost converter configuration, and wherein the each individual cell controller for the each of the multiple voltage converting cells is configured to maintain a ratio between a first and second voltage levels of non-common terminals of the two capacitors at a specified level.
20 . A voltage conversion method comprising: obtaining electrical properties data representative of electrical properties of a voltage converter system comprising a plurality of energy storage elements and a plurality of switching devices, with each of the plurality of switching devices being electrically coupled to at least one of the plurality of the energy storage elements, wherein the plurality of energy storage elements and the plurality of switching devices are configured in a multi-level arrangement of multiple voltage converting cells; and controllably actuating by a plurality of controllers coupled to the multiple voltage converting cells, based at least in part on the electrical properties data, one or more of the plurality of the switching devices to independently control voltage levels of at least one energy storage element of the multiple voltage converting cells.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Application No. PCT/US2022/018940, filed Mar. 4, 2022, entitled “Systems and Methods for Stacked Multi-Level Power Converter Implementations with Linear Scaling,” which claims the benefit of, and priority to, U.S. Provisional Application No. 63/157,075, entitled “A Fully Balanced Vertically Stacked Multilevel Power Converter Topology with Linear Scaling,” filed Mar. 5, 2021, the contents of which is incorporated herein by reference in their entireties. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH This invention was made with government support under Grant No. 1653574 awarded by the National Science Foundation (NSF). The government has certain rights in the invention. BACKGROUND Multi-level power converters serve to bridge the gap between high-voltage systems and lower voltage components. The potential applications of multilevel power conversion are wide, ranging from high-voltage DC transmission (HVDC), to medical devices, and to automotive technology. HVDC transmission systems achieve notable efficiency when controlled through multilevel topologies over traditional 2-level topologies. Electric vehicles, an inevitable future, also stand to benefit from the use of multilevel topologies. Multilevel power converters have favorable advantages when compared to single-level power converters. For example, they can operate with higher voltages than individual converters and can also output higher quality waveform signals. Further, by distributing the full voltage across multiple discrete levels, a higher quality output waveform is achieved when switching between multiple discrete levels as opposed to a topology that has only one switched level. Multi-level converters, however, often have complicated circuit topologies and can have unstable voltage balancing (which refers to the ability of the circuit to maintain a constant desired voltage between levels or across capacitors) across their circuit components. Full-bridge modular multilevel converters (MMC) have improved implementation over half-bridge MMC with respect to flexibility in capacitor voltages and balancing, but come at the cost of increased switching devices and control complexity. Likewise, the diode-clamped, capacitor clamped, and general D-shaped topologies also require extra attention to keep capacitor voltages balanced, more so as the number of levels increases. Addressing these two common issues can greatly advance the integration of multilevel power converters into high power technologies, such as electric vehicle charging and electric grids. SUMMARY The present disclosure is directed to a simple and a highly efficient multi-level configurations of stackable voltage conversion. The stackable cells of the approaches described herein can be easily connected together with linear scaling and can also be individually controlled, lending the proposed topologies to a modular and readily expandable approach. The voltage conversion configurations of the present approaches provide a bidirectional and AC/DC or DC/DC capabilities that can be used for a variety of applications, ranging from electric vehicles to HVDC transmission. The ability to simultaneously sink or source current at any node along the center stack of energy storage elements (capacitors) can be beneficial for local power distribution systems. Also described herein are physical circuits implementations for the proposed topologies, procedures and techniques to control operation of the circuitry (e.g., through control of the duty cycles), and evaluation of the performance of the proposed topologies. The proposed implementations and topologies have marked benefits over existing multilevel power converter topologies, with their simplicity at the forefront. Stackable cells can be easily connected together with linear scaling and can also be individually controlled, lending the proposed topologies to a modular and readily expandable approach. The proposed topologies mitigate the various deficiencies of traditional multi-level converters through independently operable and stackable unit switching cells that can bidirectionally convert AC/DC or DC/DC while sustaining capacitor voltage balance. Neither the complexity of control nor circuit design of this topology increases with the number of levels. Component quantities scale linearly with number of levels. The proposed topologies described herein also include an arrangement of discrete, identical, and individually controlled switching cells that are dual active half bridges with three degrees of freedom (3D-DAHB). In the DAHB voltage converter configuration, the individual cells can move power between any of the connected capacitors. The proposed DAHB topology operates by balancing the voltage of all connected capacitors. Advantages of the topologies described herein is the reduced overhead (e.g., in terms of number of components) required to implement the p