High power density universal charger

Abstract

A universal charging unit (100) is provided which can be deployed as a standard turnkey solution in dc fast charging stations operating off either three-phase or single-phase electric grids. The universal single-phase / three-phase charger functionally combines three-phase-to-dc and single phase-to-dc charging functions into a single, high power density unit. In both single-phase and three-phase configurations the universal charger operates at controllable power factor and feeds power into a dc bus, which is in turn interfaced with the battery system. While the unit operates as a conventional rectifier when in three-phase configuration, when deployed as single-phase charger the hardware not involved in the power factor correction process is reused and controlled as an active power decoupler (APD) to remove any line-frequency component from the dc bus current.

Description

HIGH POWER DENSITY UNIVERSAL CHARGERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is application claims priority to U.S. Provisional Patent Application Serial No. 63 / 677,542, filed on July 31, 2024, and entitled "HIGH POWER DENSITY UNIVERSAL CHARGER."BACKGROUND

[0002] Battery systems, such as those in electric vehicles, are typically charged from the AC power grid using either single-phase chargers or three-phase chargers. Single-phase chargers draw power from a single-phase AC power supply, commonly found in residential settings. In regions with standard household power, this is typically 120V or 240V AC, depending on the country. Three-phase chargers are designed to take advantage of three-phase AC power supplies, which are more common in industrial and commercial settings. Three-phase power systems provide higher power delivery compared to single-phase, which can significantly reduce charging times.

[0003] While each type of charger is associated with certain advantages and disadvantages, currently, when selecting a charger a user or entity must choose between one of the two types of chargers for an installation. Currently there exists no charger that can operate in both three-phase and single-phase environments.SUMMARY

[0004] A universal charging unit is provided which can be deployed as a standard turnkey solution in de fast charging stations operating off either three-phase or single-phase electric grids. The universal single-phase / three-phase charger functionally combines three-phase-to-dc and single phase-to-dc charging functions into a single, high power density unit. In both single-phase and three-phase configurations the universal charger operates at controllable power factor and feeds power into a de bus, which is in turn interfaced with the battery system. While the unit operates as a conventional rectifier when in three-phase configuration, when deployed as single-phase charger the hardware not involved in the power factor correction process is reused and controlled as an active power decoupler (APD) to remove any line-frequency component from the de bus current. Such active power decoupling is accomplished by routing the fluctuating power generated by the singlephase power factor corrector to a highly optimized, low-cost capacitive energy buffer. The system is bidirectional and can serve both as a rectifier, to achieve battery charging as described, and as an inverter, to offer grid-support functionality.Compared to separate three-phase and single-phase solutions, the proposed approach offers the advantages of a single universally applicable unit, together with reduced size and cost.

[0005] In some aspects, the techniques described herein relate to a universal charger including: a DC bus; at least three legs; a capacitive energy buffer; a DC bus capacitor; and a first operating mode and a second operating mode, wherein in the first operating mode each leg of the at least three legs is connected to adifferent phase of a three-phase electric grid and provide power to the DC bus, and in the second operating mode only two legs of the at least three legs are connected to a single phase electric grid and provide power to the DC bus.

[0006] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

[0007] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the non-connected leg operates as an active power decoupler.

[0008] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the non-connected leg operates as the active power decoupler by re-routing fluctuating power generated by the single-phase power factor corrector to a capacitive energy buffer.

[0009] In some aspects, the techniques described herein relate to a universal charger, wherein the capacitive energy buffer is an ac-film capacitor.

[0010] In some aspects, the techniques described herein relate to a universal charger, wherein the DC bus includes a bus capacitor.

[0011] In some aspects, the techniques described herein relate to a universal charger, wherein the bus capacitor is a dc-film capacitor.

[0012] In some aspects, the techniques described herein relate to a universal charger, wherein the universal charger is for an electric vehicle.

[0013] In some aspects, the techniques described herein relate to a universal charger including: a DC bus; three legs that provide power to the DC bus; acapacitive energy buffer a DC bus capacitor; and a selector component that is configured to operate the universal charger in a first operating mode when the legs are connected to a three-phase electric grid, and operate the universal charger in a second operating mode when the legs are connected to a single-phase grid.

[0014] In some aspects, the techniques described herein relate to an universal charger, wherein in the first operating mode each leg of the three legs is connected to a different phase of the three-phase electric grid and provide power to the DC bus, and in the second operating mode only two legs of the three legs are connected to the single-phase grid and provide power to the DC bus.

[0015] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

[0016] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the non-connected leg operates as an active power decoupler.

[0017] In some aspects, the techniques described herein relate to a universal charger, wherein in the second operating mode the non-connected leg operates as the active power decoupler by re-routing fluctuating power generated by the single-phase power factor corrector to a capacitive energy buffer.

[0018] In some aspects, the techniques described herein relate to a universal charger, wherein the capacitive energy buffer is an ac-film capacitor.

[0019] In some aspects, the techniques described herein relate to a universal charger including: a DC bus; three legs that provide power to the DC bus; acapacitive energy buffer a DC bus capacitor; and a selector component that is configured to operate the universal charger in a first operating mode when the legs are connected to a three-phase electric grid, and operate the universal charger in a second operating mode when the legs are connected to a single-phase grid, wherein in the first operating mode each leg of the three legs is connected to a different phase of the three-phase electric grid and provide power to the DC bus, wherein in the second operating mode only two legs of the three legs are connected to the singlephase grid and provide power to the DC bus, and wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

[0020] Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying figures, which are incorporated herein and form part of the specification, illustrate a universal charger. Together with the description, the figures further serve to explain the principles of the universal charger described herein and thereby enable a person skilled in the pertinent art to make and use the universal charger.

[0022] FIG. 1 is an illustration of an example high power density universal charger; and

[0023] FIGS. 2 and 3 are illustrations of simulated waveforms in a single-phase configuration.DETAILED DESCRIPTION

[0024] FIG. 1 is an illustration of a universal charging unit 100 which can be deployed as a standard turn- key solution in de fast charging stations operating off either three-phase or single-phase electric grids. The universal charger unit 100, also referred to herein as "universal lc[> / 3cj> charger", functionally combines three phase- to-dc and single phase-to-dc charging functions into a single, high power density unit.

[0025] As shown, the universal charger unit 100 include three legs 105 (i.e. the legs 105A, 105B, and 105C). Each leg 105 consists of two semiconductor devices such as, but not limited to, Silicon or Silicon Carbide MOSFETs or Gallium-Nitride High- Electron Mobility Transistors (GaN-HEMT) operating as electronic switches. The operation of each leg 105 is controlled by the selectors 130. In the example shown, the selectors comprise a plurality of switches or contactors that control the output and operation of each leg 105.

[0026] When the contactors of the selectors 130 are each in in the position labeled '3c|>', the legs 105A, 105B, and 105C connect to a 208-480 Vrms three-phase grid and provide charging towards a de bus with controllable power factor. When the contactors of the selectors 130 are each in the position labeled '1<|>', on the other hand, the legs 105A, 105B, and 105C connect with a 240 Vrms single-phase system. Insuch a configuration, the legs 150A and 150B connect to the utility grid and operate as a single-phase power factor corrector (PFC). Further, the leg 105C is controlled as an active power decoupler (APD) to remove any line-frequency components from the debus current.

[0027] In some embodiments, the active power decoupling by the leg 105C may be accomplished by re-routing the second-harmonic fluctuating power generated by the PFC to a highly optimized, low-volume capacitive energy buffer Cbuf. Suitable capacitors for the energy buffer Cbuf may include ac film capacitors because of their relatively higher ac rating. However, other types of capacitors may be used.

[0028] As shown, the universal charger unit 100 may further include capacitive energy buffer Cbus connected in parallel with the de bus. Suitable capacitors for the energy buffer Cbus may include dc-link film capacitors because only high- frequency switching ripple current may be handled by Cbus. However, other types of capacitors may be used.

[0029] In some embodiments, phase inductors are employed in the universal charger unit 100 to filter the grid and buffer capacitor currents. Example inductors may include traditionally wound inductors based on ferrite or distributed airgap cores, as well as low-profile, PCB-integrated planar inductors for ultra high- power density applications.... In both lcf> and 34> configurations the universal charger unit 100 feeds power into an 800 V de bus, which is in turn interfaced with a battery system 134 through a highly efficient isolated bidirectional dc-dc converter such as dual active bridge (DAB). The battery system 140 may be bidirectional and can serveboth as a rectifier, to achieve battery charging, and as an inverter, to offer gridsupport functionality.

[0030] In some embodiments, the universal charger unit 100 may further include an adaptive digital control and modulation layer 120 that self-configures according to the position of selectors 130, and controls the power factor correction, regulates the de bus voltage, and modulates the active power decoupler of the universal charger unit 100 when operating in the three-phase and single-phase operation. The adaptive digital control and modulation layer can be implemented on a general-purpose microprocessor or Field Programmable Gate Array (FPGA).

[0031] Compared to separate three-phase and single-phase solutions, the universal charger unit 100 offers the advantages of a single universally applicable unit, together with reduced size and cost. This is an advantage over prior art systems that require separate units for three-phase and single-phase operation.Table 1: System Specifications and Design Case Study

[0032] In some embodiments, the universal charger unit 100 is based on1200 V SiC MOSFET technology and provides a nominal charging power of 50 kW. The universal charger unit 100 may include a 800 V de bus, enabling compatibility towards480 Vrms (phase-to-phase) three-phase systems. Suitable values for components of the universal charger unit are summarized in Table 1.

[0033] FIGS. 2 and 3 are illustrations of simulated waveforms for the universal charging unit in single-phase configuration and nominal power 50kW. As shown in Fig. 2, by the graphs 205 and 210, the universal charge unit 100 draws power from the grid at unity or controllable power factor by modulating legs 105A and 105B via a wide-bandwidth current shaping control loop. At the same time, as illustrated in the graphs 305 and 310 of FIG. 3, PFC dc-side current ippc(t) is actively filtered by the leg 105C, resulting in a near-dc bus current Ibus- The energy buffer capacitor Cbuf is optimized to allow a wide swing of the voltage Vbuf(t) across it, reducing cost and volume. For comparison, a standard PFC energy buffer designed for a 50 kW system operating on a 800 V de bus with a 10% voltage ripple would require a 3.6x larger capacitance of 2.5 mF.

[0034] In general, the universal charger unit 100 described herein is designed and optimized around a target 1200 V SiC MOSFET technology, and with emphasis on size, cost, and volume reduction of the de bus capacitor, buffer capacitor, and phase inductors.

[0035] The universal charger unit 100 employs a co-designed PFC control loop, an APD control loop, and a de bus voltage regulation loop in order to enable stable and robust operation even with strongly optimized de bus capacitance and buffer capacitance. Such control strategies i) strongly reduce the de bus RMS current in three- phase configuration, and ii) guarantee system stability, robustness, and high-quality de bus current filtering in single- phase configuration through an ad-hoc APD control solution.

[0036] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A universal charger comprising: a DC bus; at least three legs; a capacitive energy buffer; a DC bus capacitor; and a first operating mode and a second operating mode, wherein in the first operating mode each leg of the at least three legs is connected to a different phase of a three-phase electric grid and provide power to the DC bus, and in the second operating mode only two legs of the at least three legs are connected to a single phase electric grid and provide power to the DC bus.

2. The universal charger of claim 1, wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

3. The universal charger of claim 2, wherein in the second operating mode the non-connected leg operates as an active power decoupler.

4. The universal charger of claim 3, wherein in the second operating mode the non-connected leg operates as the active power decoupler by re-routing fluctuating power generated by the single-phase power factor corrector to a capacitive energy buffer.

5. The universal charger of claim 4, wherein the capacitive energy buffer is an ac- film capacitor.

6. The universal charger of claim 1, wherein the DC bus includes a bus capacitor.

7. The universal charger of claim 10, wherein the bus capacitor is a dc-film capacitor.

8. The universal charger of claim 1, wherein the universal charger is for an electric vehicle.

9. A universal charger comprising: a DC bus; three legs that provide power to the DC bus; a capacitive energy buffer a DC bus capacitor; and a selector component that is configured to operate the universal charger in a first operating mode when the legs are connected to a three-phase electric grid, and operate the universal charger in a second operating mode when the legs are connected to a single-phase grid.

10. The universal charger of claim 9, wherein in the first operating mode each leg of the three legs is connected to a different phase of the three-phase electric grid and provide power to the DC bus, and in the second operating mode only two legs of the three legs are connected to the single-phase grid and provide power to the DC bus.

11. The universal charger of claim 10, wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

12. The universal charger of claim 11, wherein in the second operating mode the non-connected leg operates as an active power decoupler.

13. The universal charger of claim 12, wherein in the second operating mode the non-connected leg operates as the active power decoupler by re-routing fluctuating power generated by the single-phase power factor corrector to a capacitive energy buffer.

14. The universal charger of claim 13, wherein the capacitive energy buffer is an ac-film capacitor.

15. A universal charger comprising: a DC bus; three legs that provide power to the DC bus; a capacitive energy buffer a DC bus capacitor; and a selector component that is configured to operate the universal charger in a first operating mode when the legs are connected to a three-phase electric grid, and operate the universal charger in a second operating mode when the legs are connected to a single-phase grid, wherein in the first operating mode each leg of the three legs is connected to a different phase of the three-phase electric grid and provide power to the DC bus, wherein in the second operating mode only two legs of the three legs are connected to the single-phase grid and provide power to the DC bus, and wherein in the second operating mode the connected two legs operate as a single-phase power factor corrector.

Images