Three-phase to three-phase direct matrix converter

Abstract

A direct current (DC) fast charger for charging a battery of an electric vehicle (EV) includes a primary circuit having nine switches, electrically linked to a primary wire of a transformer, and configured to receive three-phase alternating current (AC) power and increase a frequency of the AC power; and a secondary circuit comprising six switches or diodes arranged to rectify the AC voltage into DC power, the secondary circuit being electrically linked to the secondary leads of the transformer.

Description

Government interests

[0001] This invention was made with government support under Contract DE-EE0009869 awarded by the U.S. Department of Energy, Directorate of Energy Efficiency and Renewable Energy EE-1. The U.S. Government has certain rights in this invention. Technical Field

[0002] The present application relates to electric vehicles (EVs), and more particularly to chargers for charging EVs. Background Art

[0003] Modern vehicles are increasingly propelled at least partially or entirely by electric motors. A vehicle, often referred to as an electric vehicle (EV), includes a vehicle battery and one or more electric motors that drive the vehicle wheels. The vehicle battery is periodically coupled to a battery charger. As drivers purchase an increasing number of EVs, they will want to be able to charge the vehicle battery relatively quickly. Therefore, faster and more efficient vehicle battery chargers are helpful. Summary of the invention

[0004] In one implementation, a direct current (DC) fast charger for charging a battery of an electric vehicle (EV) includes: a primary circuit having nine switches electrically linked to a primary conductor of a transformer and configured to receive three-phase alternating current (AC) power and increase the frequency of the AC power; and a secondary circuit including six switches or diodes arranged to rectify the AC power into DC power, the secondary circuit being electrically linked to the secondary conductor of the transformer.

[0005] In another implementation, a DC fast charger for charging a battery of an EV includes: a primary circuit electrically linked to a primary conductor of a transformer, configured to receive three-phase alternating current (AC) power and increase the frequency of the AC power; and a secondary circuit including six switches or diodes electrically linked to the secondary conductors of the transformer, the secondary circuit receiving the AC power and rectifying the AC power with increased frequency into DC power. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram depicting the implementation of an electric vehicle;

[0007] Figure 2 is a circuit diagram depicting the implementation of a DC fast charger AC / DC power converter;

[0008] Figure 3 is a circuit diagram depicting another implementation of a DC fast charger AC / DC power converter; and

[0009] Figure 4is a circuit diagram depicting yet another implementation of a DC fast charger AC / DC power converter. DETAILED DESCRIPTION

[0010] A three-phase to three-phase direct matrix converter may be used in an EV battery charger that supplies direct current (DC) electrical power to an electric vehicle (EV). In the past, a six-switch indirect matrix converter using six bidirectional switches in the primary circuit and four switches in the secondary circuit has received three-phase alternating current (AC) electrical power from the power grid as single-phase AC electrical power. The single-phase AC power may then be converted to DC electrical power. However, it is possible to implement an EV battery charger that receives three-phase AC electrical power from the grid and triples the amount of electrical power output from the EV battery charger while also reducing the number of switch devices used to do so.

[0011] The present EV battery charger (also referred to as a DC fast charger) may include a three-phase to three-phase direct matrix converter. The direct matrix converter uses nine bidirectional switches to transform low-frequency three-phase AC power into high-frequency three-phase AC power in the primary circuit. Six switches may then be used to convert the high-frequency three-phase AC power into DC electrical power in the secondary circuit. The switches in the primary and secondary circuits may be connected in a variety of configurations depending on the application. For example, in one implementation, the switches in the primary and secondary circuits may be arranged as a YY transformer. Or in another implementation, the switches may be arranged as a Δ-Δ transformer. Yet another implementation is a Y-Δ transformer.

[0012] Go to Figure 1 , shows an implementation of an electrical system 10, the electrical system includes a power grid 12 and an electric vehicle (EV) 14, the EV can receive electric power from the grid 12 or provide electric power to the grid 12. The power grid 12 may include any one of several electric power generators and electric transmission mechanisms. The generator (not shown) produces AC electric power, which can then be transmitted a considerable distance away from the generator for residential and commercial use. The generator can be coupled to the power grid 12, and the power grid transmits the AC electric power from the generator to an end user, such as a residence or a business. When the AC electric power is provided to the power grid 12, the electric power can exist at a relatively high voltage so that it can be transmitted over a relatively long distance. Once the electric power reaches the location where it is expected to be used, a power transformer (not shown) can be used to reduce the voltage level before it is finally provided to the residence or business. In one implementation, the voltage level of the AC electric power used is 360-510 volts (RMS AC three-phase) at a frequency of 50-60hz. However, the voltage can be a different value.

[0013] The EV charging station (referred to herein as a DC fast charger 16) may receive an AC voltage from the grid 12, convert the AC voltage to a higher frequency AC voltage, convert the higher frequency AC voltage to a DC voltage, and provide the DC voltage to the EV 14. Furthermore, the DC fast charger 16 may receive stored electrical power in the form of a DC voltage from the EV battery 22, convert the received DC voltage to an AC voltage, and transfer it to the grid 12. The DC fast charger 16 may be geographically fixed, such as a charging station located in a vehicle garage or in a vehicle parking lot. The DC fast charger 16 may include an input terminal that receives AC electrical power from the grid 12 and transfers the converted DC electrical power directly to the EV battery 22, thereby bypassing an onboard vehicle battery charger 18 included on the EV 14. The cable 20 may be detachably connected to an electrical socket on the EV 14 and electrically links the DC fast charger 16 with the EV 14 so that a DC voltage may be transferred between the DC fast charger 16 and the EV battery 22. The DC fast charger 16 can receive AC power from the grid 12 and has a rated power of 180-1100kW provided to the EV 14. This type of DC fast charging may be referred to as Level 3 megawatt EV charging. However, different standards may be used at EV charging stations. The term "electric vehicle" or "EV" may refer to a vehicle that is propelled in whole or in part by an electric motor. EV may refer to an electric vehicle, a plug-in electric vehicle, a hybrid electric vehicle, and a battery-powered vehicle. The EV battery 22 may supply DC electric power controlled by power electronics to the electric motor that propels the EV. One or more EV batteries 22 are rechargeable and may include lead-acid batteries, nickel-cadmium (NiCd), nickel-metal hydride, lithium-ion, and lithium-polymer batteries. The typical range of vehicle battery voltage may vary from 100 to 1000V of DC electric power (VDC).

[0014] The onboard vehicle battery charger 18 may include a power factor correction (PFC) module having a switching circuit that converts AC electrical power into DC electrical power. In addition, the switching circuit 26 may also act as an inverter that converts high frequency AC electrical power received from the DC electrical power through the secondary circuit 28 and the transformer into AC electrical power that may be transmitted outside the EV 14. A microprocessor (not shown) electrically linked to the gate of each switch may control the rectification of the incoming AC electrical power and the inversion of the outgoing DC electrical power. A control system implemented as computer-readable instructions executable by a microprocessor may be stored in a non-volatile memory and called to control the functionality of the DC fast charger 16. This will be discussed in more detail below.

[0015] Figure 2Depicting an implementation of a DC fast charger 16a. The DC fast charger 16a is a direct matrix converter that includes a primary circuit 26a and a secondary circuit 28a that are inductively coupled together via a plurality of transformers 30, 32, 34. The primary circuit 26a includes nine switches 36 electrically coupled to the grid 12. The first phase (PHA) includes three switches 36a-c, the second phase (PHB) includes three switches 36d-f, and the third phase (PHC) includes three switches 36g-i. The switches 36 may be implemented using bipolar junction transistors or field effect transistors (FETs), such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), or gallium nitride (GaN) transistors. The switches 36 may be bidirectional or reverse blocking, such that they are four-quadrant switches capable of conducting positive or negative on-state currents and blocking positive or negative off-state voltages. Such switches may be implemented using a number of different circuit configurations, any of which may be implemented in the DC fast chargers described herein. In one implementation, each switch 36 includes an A-side MOSFET and a B-side MOSFET having a gate that can be electrically connected to a microprocessor.

[0016] Nine switches 36a-i can be electrically coupled to three branches PHA, PHB, PHC of the power grid. The bulk capacitor 24 can be electrically connected to the branches PHA, PHB, PHC of the power grid 12. Each phase and the three switches electrically coupled to each phase can also be coupled to a transformer. The primary circuit 26a and the secondary circuit 28a are shown in a YY configuration. For example, the first phase (PHA) can be coupled to switches 36a, 36d and 36f. The second phase (PHB) can be coupled to switches 36b, 36e and 36h. The third phase (PHC) can be coupled to switches 36c, 36f and 36i. Switches 36a-c can also be electrically connected to the primary conductor of the first transformer 30. Switches 36d-f can also be electrically connected to the primary conductor of the second transformer 32. Switches 36g-i can also be electrically connected to the primary conductor of the third transformer 34. The primary conductors of the transformers 30, 32, and 34 can be electrically connected together so that a common neutral node (N1) exists within the primary circuit 26a.

[0017] The secondary circuit 28a is electrically connected to the secondary windings of the transformers 30, 32, 34. The secondary circuit 28a includes six switches 38a-f. The switch 38 can be implemented using a bipolar junction transistor or a field effect transistor (FET) (such as an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET)). The secondary circuit 28a may include a capacitor 40 that smoothes the output DC voltage. The EV battery 22 may be electrically connected to the switch 38 so that the secondary circuit 28a rectifies the AC voltage induced by the secondary windings of the transformers 30, 32, 34 into a DC voltage applied to the EV battery 22. The secondary circuit 28a may be implemented so that the secondary wires of the transformers 30, 32, 34 are electrically connected to have a common neutral node (N2).

[0018] Go to Figure 3 , another implementation of a DC fast charger 16b is shown. The DC fast charger 16b is a direct matrix converter that includes a primary circuit 26b and a secondary circuit 28b that are inductively coupled together via a plurality of transformers 30, 32, 34. The primary circuit 26b includes nine switches 36 electrically coupled to the grid 12. The primary circuit 26b and the secondary circuit 28b are arranged in a delta-delta configuration. The first phase (PHA) can be coupled to switches 36a, 36d, and 36f. The second phase (PHB) can be coupled to switches 36b, 36e, and 36h. The third phase (PHC) can be coupled to switches 36c, 36f, and 36i. Switches 36a-c can also be electrically connected to the primary conductor of the first transformer 30. Switches 36d-f can also be electrically connected to the primary conductor of the second transformer 32. Switches 36g-i can also be electrically connected to the primary conductor of the third transformer 34. The primary conductors of the transformers 30, 32, 34 can be electrically connected together in series. The secondary circuit 28b may be implemented such that the secondary conductors of the transformer may be wired in series to the switch 38. In other implementations, the switch 38 in the secondary circuit 28b may be replaced with a passive electrical component, such as a diode.

[0019] Figure 4 Another implementation of a DC fast charger 16c is depicted. The DC fast charger 16c includes a primary circuit 26a and a secondary circuit 28b arranged in a Y-delta configuration. The DC fast charger includes the primary circuit 26a and the secondary circuit 26b described above inductively linked via a plurality of transformers 30, 32, 34.

[0020] It is to be understood that the foregoing is a description of one or more embodiments of the present invention. The present invention is not limited to the (one or more) specific embodiments disclosed herein, but is instead defined only by the claims hereinafter. In addition, except where terms or phrases are clearly defined above, the statements contained in the foregoing description relate to specific embodiments and are not to be interpreted as limitations on the scope of the present invention or on the definition of the terms used in the claims. Various other embodiments and various changes and modifications to the disclosed (one or more) embodiments will become apparent to those skilled in the art. All such other embodiments, changes and modifications are intended to fall within the scope of the appended claims.

[0021] As used in this specification and claims, when used in conjunction with a list of one or more components or other items, the terms "for example," "for example," "such as," and "similar," and the verbs "comprise," "have," "include," and other verb forms thereof, are each to be interpreted as open-ended, meaning that the list is not to be construed to exclude other additional components or items. Other terms are to be interpreted using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

1. A direct current (DC) fast charger for charging a battery of an electric vehicle (EV), comprising: a primary circuit comprising nine switches electrically linked to the primary conductors of the transformer and configured to receive three-phase alternating current (AC) power from a power grid and to increase the frequency of the AC power; and A secondary circuit, comprising six switches or diodes arranged to rectify AC power to DC power, is electrically linked to the secondary conductors of the transformer.

2. The DC fast charger of claim 1 further comprising a control system electrically linked to the nine switches.

3. A DC fast charger as claimed in claim 1, wherein: The DC fast charger includes a plurality of transformers.

4. A DC fast charger as claimed in claim 1, wherein: The DC fast charger includes a single three-phase transformer.

5. A DC fast charger as claimed in claim 1, wherein: The nine switches in the primary circuit are bidirectional.

6. A DC fast charger as claimed in claim 5, wherein: The nine switches include A-side MOSFETs and B-side MOSFETs.

7. A DC fast charger as claimed in claim 1, wherein: The primary circuit and the secondary circuit are arranged in a YY orientation.

8. A DC fast charger as claimed in claim 1, wherein: The primary circuit and the secondary circuit are configured in a delta-delta configuration.

9. A DC fast charger as claimed in claim 1, wherein: The primary circuit and the secondary circuit are configured in a delta-Y configuration.

10. A direct current (DC) fast charger for charging a battery of an electric vehicle (EV), comprising: a primary circuit electrically linked to the primary conductor of the transformer and configured to receive three-phase alternating current (AC) power and increase the frequency of the AC power; and A secondary circuit, including six switches or diodes electrically linked to the secondary conductors of the transformer, receives three-phase AC power of increased frequency and rectifies the AC power into DC power.

11. A DC fast charger as claimed in claim 10, further comprising a control system electrically linked to the primary circuit.

12. A DC fast charger as claimed in claim 10, wherein: The fast charger includes a plurality of transformers.

13. A DC fast charger as claimed in claim 10, wherein: The primary circuit includes a plurality of bidirectional switches.

14. The DC fast charger as claimed in claim 10, wherein: The switch in the secondary circuit is bidirectional.

15. The DC fast charger as claimed in claim 10, wherein: The primary circuit and the secondary circuit are arranged in a YY orientation.

16. The DC fast charger as claimed in claim 10, wherein: The primary circuit and the secondary circuit are configured in a delta-delta configuration.

17. The DC fast charger as claimed in claim 10, wherein: The primary circuit and the secondary circuit are configured in a delta-Y configuration.

Images