Patent Application
20240333130
The disclosure relates to a Direct Current (DC) distribution system, in particular a managed, grid integrated and/or self-contained DC distribution system, connected or connectable to an electrical power source.
Furthermore, the disclosure relates to a power convertor for use in a DC distribution system.
Such a distribution system is known from the prior art. The known distribution system includes a DC bus having a power source input electrically connected to the DC bus and configured for receiving an Alternating Current (AC) from an AC source, such as an AC grid. The distribution system is provided with an AC/DC converter for converting the AC from the AC grid to a DC to be provided to the DC bus. A number of electrical loads, such as an electric vehicle charger and/or building loads, are connected to the DC bus, which electrical loads are provided with electrical power by the DC bus. A DC/DC converter is provided between each of the electrical loads and the DC bus in order to convert the DC of the DC bus to a DC that is useable by the respective electrical load.
A disadvantage of the known DC distribution system is that it is fed by conventional AC/DC converters connected to a low voltage, LV, grid or a medium voltage, MV, grid via a MV substation. Conventional converters usually are connected to 50 or 60 Hz low voltage (LV) or medium voltage (MV) grids. For applications where a MV grid is needed a MV substation is likely to be used between the grid and the AC-DC converter. The MV substation is commonly composed by a MV stall, a MV/LV transformer, and LV breakers. The transformer operating at 50/60 Hz has a disadvantage as the size, since it applies that the lower the operating frequency, the larger the transformer has to be. Since the transformer has to be large, much material is needed.
It is an aspect of the present disclosure to ameliorate or to eliminate one or more disadvantages of the known prior art, to provide an improved DC distribution system or to at least provide an alternative DC distribution system.
According to a first aspect, the disclosure provides a Direct Current (DC) distribution system, including:
During operation of the DC distribution system according to the disclosure, at least one of the first power convertor and the second power convertor includes solid state transformer (SST) technology that contributes to converting an AC from an AC source to a DC voltage to be provided to the DC bus and/or to be provided to the electrical load electrically connected to the DC bus. Solid state transformer technology, at least in the context of the present disclosure, is working at a high operating frequency in comparison to the operating frequency of a conventional transformer, such as an AC/DC converter. The high operating frequency allows the power converter to be designed with a smaller core in comparison with the known power converter. Therefore, less wire and less magnetic material are required for the power converter based on SST technology in comparison to the known conventional converter. Therefore, the power converter based on the SST technology is smaller than the MV/LV transformer and the AC/DC converter as known in the prior art. Furthermore, due applying a load factor that is below 1 to the DC distribution system, the dimensions of the first power converter may be kept relatively small in comparison to the MV/LV transformer and the AC/DC converter as known in the prior art.
In an embodiment, the first power converter includes the converter based on SST technology. In an embodiment thereof, the first power converter includes, in series:
In the context of the present disclosure, low voltage (LV) may be understood as a voltage up to 1000 Vac and 1500 Vdc, and medium voltage may be understood as a voltage from 1000 Vac/1500 Vdc to 36 kVac/50 kVdc.
In an embodiment, the second power converter includes the converter based on SST technology. In an embodiment thereof, the second power converter includes, in series:
In an embodiment, the DC distribution system includes a controller communicatively connected to each of the first power converter and the second power converter, wherein the controller is configured for controlling each of the first power converter and the second power converter. During operation, the controller may collect and monitor operation of the first and second power converters, for example, in order to determine how much power is converted by each of the first and second power converters. As a result, the controller advantageously may be enabled to determine, for example, whether the electrical load is operating optimally, and/or to adjust power provided to or from the electrical load/the DC bus by adjusting operating parameters of the first and/or second power converter. This allows the DC distribution system according to this embodiment to achieve optimal operation.
In an embodiment, the DC distribution system includes a virtual power plant (VVP) connected to the controller and to an open power market, such as a frequency containment reserve (FCR) market, and configured for providing use information to the controller. The DC distribution system may include multiple electrical loads, such as one or more electric vehicle (EV) chargers and one or more batteries, connected to the DC bus. The VVP is connected to the open power market and, therefore, is enabled to determine, for example, whether the power prices on the AC grid are high or low and to provide this information to the controller. In the case of high power prices, the controller may determine to draw excess power from the DC bus and offer it for sale to the AC grid, and in the case of low power prices, the controller may determine to store additional power in the one or more batteries. An advantage of this embodiment, therefore, is that power may be bought and/or sold on appropriate moments such that the operating costs of the DC distribution system are controllable.
In an embodiment, the DC distribution system includes a fleet management controller connected to the controller and configured for managing charging of a fleet of electric vehicles. During use, the fleet management controller, for example, may determine which electric vehicles in a fleet have to be charged and communicate this information to the controller. Subsequently, the controller, for example, may control the first power converter to convert some additional power to provide additional power into the DC distribution system in advance, and/or the controller may decide to not sell any power as the power is required within the DC distribution system on a short notice. This is advantageous, as the fleet management controller allows the DC distribution system to be prepared for a power demand in the near future.
In an embodiment, the electric load is selected from a group including an electric vehicle charger, an electric trolley system, building loads, and the like.
In an embodiment, the power source input is connected to an AC grid, to an AC power generator and/or to a mechanical power source, and/or one or more additional power sources are electrically connected to the DC bus, wherein the one or more additional power sources are selected from a group including solar panels, wind turbines, energy storages, and the like.
According to a second aspect, the disclosure provides a power convertor for use in a DC distribution system according to the first aspect of the disclosure, wherein the power convertor includes, in series:
The power convertor according to the disclosure has at least the same technical advantages as described in relation to the DC distribution system according to the first aspect of the disclosure.
The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.
The disclosure will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:
The present disclosure is applicable to managed, grid integrated and/or self-contained DC distribution systems, which include both electrical power sources and sinks.
In one embodiment, the DC distribution system includes a (AC/DC or DC/DC) feeding or fed by DC or AC load/sources such as solar, storage, wind and the like. In this embodiment, DC distribution is connected to a MV AC grid via one or more converters based on solid state transformer technology (SST). DC distribution can be in medium voltage (MV) or low voltage (LV) in accordance with prevailing standards. For such use case, LV is most likely but depends on the intended application. Multiple SST connected in parallel on the same DC distribution can be used. The power of SST is lower than the power needed in the system. In accordance with a load factor principle, all the converters are connected to the site controller. The site controller manages power/energy flow keeping the entire DC distribution system operating within prescribed limits and in stable operative conditions. The site controller is connected to a back-end platform (VPP) acting as aggregator manager for one or more site controllers simultaneously. Based on operative conditions, the VPP sets a predefined or desired set point or limitations to the converters. The VPP, based on the current operating conditions and/or local requirements is configured and operates to sell or purchase electrical energy from or to a market, for example, the Frequency Containment Reserve (FCR) Market. The site controller is also connected to a fleet management instrumentality. Most of the converters are isolated, which helps to confine any failures. Each converter might be equipped with a switch and protection device such as a fuse or solid state breaker. In accordance with this first embodiment, SST multiple DC distributions are generated with different voltage levels for different consumers/sinks such as electric vehicles, building loads, and the like.
In a second embodiment, similar to the first embodiment, a DC distribution system is shown. Here, due to higher power than in the first embodiment, the DC distribution system includes a DC bus that is disposed at a medium voltage (MV) and the DC power distributed is generated by one or more AC/DC converters connected to a MV AC grid. MV DC/LV DC isolated converters (Part of SST technology) are connected to the MV distribution stepping down the voltage for low voltage applications. Additional converters are connected to the above converters on LV DC side or to supply local loads. The DC distribution system may include storage devices such as batteries, as well as power generation devices such as solar and wind generation systems. Power converters associated with the bus are configured and operate to also provide load regulation. If the load does not require or have wide power variations, the additional converters may be omitted and may be used. In the event a trolley (catenary) is present, the MVDC/LVDC converter can be used to feed directly the line, such that a converter in between may not be needed. Storage may also be included for peak shaving.
In a third embodiment, which uses the same general structure as the first and/or second embodiments for DC distribution systems, the DC bus may operate at a MV, for example, in the case of a mining truck or marine application. Compared to the first and second embodiments, in the third embodiment, MV DC distribution is generated by one or more AC/DC converters connected to a synchronous generator that is driven or powered by a prime mover, for example, an internal combustion or other type of engine, for example, a gas turbine. If the vessel or truck is full electric, only a storage battery is present. In the case of an electric truck, an energy dissipater can also be used to burn excess energy.
More specifically, two types of power converters will first be described, followed by a description of the three DC distribution system embodiments. In reference to the figures,
As is known, the SST 108 can be embodied in many forms. In general, a SST is a collection of high-powered semiconductor components, conventional high-frequency transformers, control circuitry and, additionally or alternatively, power electronics that are used to provide an elevated level of flexible control to power distribution networks. By adding some communication capability, the entire package is often referred to as a smart transformer. SST technology can step up or step-down AC voltage levels just like that of the traditional transformer, but it also offers several significant advantages. They use transistors and diodes and other semiconductor-based devices that, unlike the transistors used in computer chips, are engineered to handle high power levels and very fast switching. The SST 108 is of the step-down voltage type.
A second type of power converter 200 is shown in
A first embodiment of a distribution system 300 is shown in
The DC bus 304 can also be connected to battery arrays 312 through a power converter 310, which can be the same or similar to operation and function to the power converter 310 connected to the building 308. Additional sources connected to the bus 304 through power controllers can include solar arrays 314, wind turbines 316 and the like. The bus 304 may also be connected to EV charging stations 318, which may also be connected to the communication line 311. In the embodiment shown, the types of sources and sinks connected to each branch of the bus 304 are distributed in a balanced fashion, but it should be appreciated that other arrangements can be used. Importantly, a site controller 320 operates to balance the power on the bus 304 by monitoring, with the aid of sensors 322, the overall power flow direction on each branch and connected device on the bus, and also the power transferred overall into or out from the bus and also the power into and out from each of the connected devices 308, 312, 314, 316, 318, and the like.
During operation, the site controller 320, which may be implemented in software and/or hardware and includes programming ability to execute computer instructions selectively to control various devices or systems, is connected to the command line 311 and is configured to send and receive information and commands there through. For example, the site controller 320 may collect and monitor operation of all devices to determine whether each device is operating in an optimum fashion and adjust the power provided to/from each device to achieve optimum operation.
Moreover, the site controller 320 may monitor the total power in/out of the DC bus and adjust the operation of sources or sinks connected to the DC bus accordingly. In one example, the site controller 320 may adjust operating parameters of the AC/DC converters 102 to provide more or less power to the bus 304. Also, the site controller 320 can adjust the power input or output to the bus, and/or store or release power from the batteries 312, when more or less consumption is expected to be provided to the EV charging stations 318. In this respect, the site controller 320 may communicate with a fleet management controller 324 to determine which vehicles in a fleet will be needing power, and when, so that the site controller 320 can schedule production or input of power to the bus in advance.
The site controller 320 is also connected to a virtual power plant (VPP) 325, which communicates with the open power market such as the frequency containment reserve (FCR) market 326 via a broker 328, and thus provide information to the site controller 320 or one or more additional site controllers 330 in one or more different facilities that is indicative of the most beneficial use of power. For example, on a windy and sunny day when production is ample and grid demand dictates a high sale price for power, the site controller 320 may draw excess power generation in the bus and provide it for sale to the grid, provided the fleet management controller 324 indicates no excessive need in the near future by vehicles for charging that would exceed the power generation capacity. At times of low prices on the grid, the site controller 320 may instead opt to store power in the batteries 312 provided that the storage conditions are optimum for the life expectancy and operating conditions of the batteries 312.
A second embodiment of a distribution system 400 is shown in
More specifically, in reference to
Each source, for example, wind and battery 312 and 316, is connected to the bus via a respective DC/DC transformer 204 (also see
In a third embodiment, a self-contained distribution system 500 is shown in
In all described embodiments, the site controller 320 is configured to manage all power inputs and consumption on the bus 304, and do so in a way that optimizes use of the devices connected thereto. For example, power may be allocated to a sink, battery, or for sale back to the grid when excess capacity exists, even if such excess capacity could have been used by the sinks but would have caused them to operate in a sub-optimal fashion. The site controller thus sets limits in the electrical power can is delivered through any node connecting the bus to the grid and to each source/sink.
Example embodiments of this disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Variations of those example embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the disclosure to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
It is to be understood that the above description is included to illustrate the operation of the example embodiments and is not meant to limit the scope of the disclosure. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present disclosure.
This patent application is a National Stage Entry of PCT/EP2021/073800 filed on Aug. 27, 2021, which claims the benefit and priority of U.S. Provisional Patent Application No. 63/178,980 filed on Apr. 23, 2021, the disclosures of which are incorporated by reference herein in their entirety as part of the present application.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/073800 | 8/27/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63178980 | Apr 2021 | US |
