US-12627294-B1 - Heterogeneous solid state transformers with hierarchical control

Abstract

Structural modularity is critical to solid-state transformer (SST) and solid-state power substation (SSPS) concepts, but operational aspects related to this modularity are not yet fully understood. Previous studies and demonstrations of modular power conversion systems assume identical module compositions, but dependence on module uniformity undercuts the value of the modular framework. A hierarchical control approach for modular SSTs achieves system-level objectives while ensuring equitable power sharing between nonuniform building block modules. This enables module replacements and upgrades which leverage circuit and device technology advancements to improve system-level performance.

Inventors

• Jack D. Flicker
• Jacob Mueller

Assignees

• NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA, LLC

Dates

Publication Date

20260512

Application Date

20240930

Claims (11)

1. 1 . A solid state transformer, comprising: a system controller; and a module controller; wherein the system controller generates a module operational setpoint that is provided to the module controller to derive switching signals for a switching module; and wherein the switching module uses a low bandwidth signal, the low bandwidth signal is between 10-300 Hz.
2. 2 . The transformer of claim 1 , wherein the switching frequency of the switching module operating between 10-100 kHz.
3. 3 . The transformer of claim 1 , wherein the switching module comprises a collection of switches, passive components and a high frequency transformer.
4. 4 . The transformer of claim 1 , wherein the module operational setpoint is selected from voltage, power, current, reactive power.
5. 5 . The transformer of claim 1 , wherein the transformer comprises a hierarchical control architecture that enables stable operation of paralleled and/or series-connected heterogeneous modules in a common system.
6. 6 . The transformer of claim 1 , wherein the transformer achieves flexibility in voltage and current rating by interconnection of multiple lower rated modules cascaded in series for higher voltage operation or in parallel for higher current operation.
7. 7 . The transformer of claim 1 , wherein there are two or more module controllers.
8. 8 . A solid-state substation comprising the solid state transformer of claim 1 .
9. 9 . A method of controlling power distribution within a power distribution system, comprising: distributing at one or more nodes in the power distribution system a solid state transformer comprising a hierarchical control architecture that enables the stable operation of paralleled and/or series-connected heterogeneous modules in a common system by distributing module-specific (fast-time) controls to individual modules while system-level behavior (slow-time) response is centralized.
10. 10 . The method of claim 8 , wherein distributing module-specific controls is at 10-100 kHz.
11. 11 . The method of claim 8 , wherein system-level behavior response is at 10-300 Hz.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63/541,109, filed on Sep. 28, 2023, entitled “Systems, Methods and Tools for Hierarchical Control for Heterogeneous Solid State Transformers,” the entirety of which is incorporated herein by reference. STATEMENT OF GOVERNMENT INTEREST This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. FIELD The present disclosure is generally directed to transformers and more particularly directed to modular solid state transformers utilizing a hierarchical control approach to achieve system-level objectives while ensuring equitable power sharing between nonuniform building block modules. BACKGROUND Power grids are undergoing historically unprecedented change. Previously consistent load profiles are being significantly altered by the rapid electrification of transportation systems. Generation is becoming more distributed and intermittent. The rate of utility-scale storage deployment is increasing. All of these changes stem from a common factor: the availability of power electronic devices and systems robust enough to withstand the stresses of utility applications. Power electronics are at the core of the electric drives disrupting aggregate load behavior, the inverters interfacing renewable and distributed energy resources, and the DC power supplies behind all modern telecommunications infrastructure. The emergence of grid-capable power electronics has led to a more dynamic electrical system. Power flow is less predictable, and without the inertia of traditional electromechanical generation, system protection is more challenging. Power electronics are not the only forces changing the grid. Electrical infrastructure is aging and ill-equipped to support the rapid changes in energy utilization. Simultaneously, power systems are under increasing threat of cyber and physical attack, the effects of electromagnetic pulse (EMP) and geomagnetic disturbance (GMD) events, and increasingly frequent severe weather events. Energy infrastructure is subject to a changing set of stressors, and new tools are needed to ensure the resiliency of tomorrow's energy infrastructure. Traditionally, control over utility systems has been applied either at the point of generation in large rotating machines, or through binary switching decisions distributed throughout the power system (e.g., relays, transformer tap changers). While this approach was suitable for unidirectional power flow between generation and load, it is strained by the increasing complexity of power flow in modern electrical networks. What is needed are devices and controls that address the limitations of the prior art. SUMMARY OF THE DISCLOSURE The present disclosure is directed to Solid-State Power Substations (SSPS) that leverage power electronics' ability to control the flow of electrical energy. It is specifically focused on utilization of hierarchical control of heterogeneous solid state transformers. SSPS embed points of control throughout distribution systems. The SSPS acts as a hub for interconnection between transmission systems, AC and DC distribution networks, local distributed energy resources, and energy storage assets. SSPS are a flexible and scalable framework for implementation of new power conversion and control functions and are envisioned as the workhorse of grid modernization. SSPS are not only a solution to known challenges but provide a platform that streamlines the deployment of new solutions to emergent needs of evolving power systems. SSPS achieve this flexibility in voltage and current rating by the interconnection of multiple lower rated modules cascaded in series, for higher voltage operation, or in parallel for higher current operation. SSPS is typically thought to be composed of a homogenous interconnection of modules, where each module is identical. In this disclosure, a hierarchical control is split between the overarching system and the local, module control that allows for modular SST architectures composed of non-uniform modules in a cascaded configuration. Without this split in hierarchical control, SST modules are forced to be uniform in both device composition as well as circuit topology or the complexity of system increases exponentially with the number of modules. Cascading of SST modules is supremely important for fielded SST operation as this will allow for modular SST blocks to achieve higher voltage scalability for the system. According to an embodiment of the disclosure, a solid state transformer is disclosed that includes a system controller and a module controller. The system controller generates a module operational setpoint that is provided to the module controller to derive switching signals for a switching module, and the switching module uses a low bandwid