BACKGROUND

Power conversion systems are used to interface a variety of different electrical loads with a power system and any associated energy storage. Power conversion systems with transformers provide galvanic isolation and allow loads to be decoupled from distribution systems and to operate at different voltages and frequencies. However, space and energy is limited in many conversion systems.

One power conversion system of current interest is a charger that can be used to charge an electric vehicle (EV). As EVs become more prevalent and are provisioned with varying charge capabilities, there is much interest in EV charging systems. Currently, such charging systems are rather bulky and expensive, and can be somewhat inflexible in charge capabilities. For wide adoption of electric vehicles, higher power fast charging stations are needed.

SUMMARY OF INVENTION

In one aspect, an electric vehicle (EV) charging system includes: a plurality of first converters to receive grid power at a distribution grid voltage and convert the distribution grid voltage to at least one second voltage; at least one high frequency transformer coupled to the plurality of first converters to receive the at least one second voltage and to electrically isolate a plurality of second converters coupled to an output of the at least one high frequency transformer; and the plurality of second converters coupled to the output of the at least one high frequency transformer to receive the at least one second voltage and convert the at least one second voltage to a third DC voltage. At least some of the plurality of second converters are to couple to one or more EV charging dispensers to provide the third DC voltage as a charging voltage or a charging current.

In an example, the plurality of first converters are to receive the distribution grid voltage directly from a distribution grid network without an intervening power transformer. In one case, at least two of the plurality of second converters are to provide the charging voltage to a first EV charging dispenser. The at least two of the plurality of second converters can be connected in series. The at least one high frequency transformer may have a single primary winding and a plurality of secondary windings, where each of the plurality of secondary windings is to provide the at least one second voltage to one of the plurality of second converters.

In an example, the EV charging system further comprises a grid-tie module having the plurality of first converters, the grid-tie module directly coupled to a distribution grid network to receive the distribution grid voltage. The EV charging system may further comprise at least one solar converter coupled to the at least one high frequency transformer and at least one photovoltaic array.

In an example, the EV charging system further includes a controller, in a generation mode, to cause energy from the at least one photovoltaic array to be provided to the distribution grid network via the EV charging system. The controller, in a charging mode, may cause at least some of the energy from the at least one photovoltaic array to be provided to the one or more EV charging dispensers. The controller, in a reverse power mode, is to cause stored energy from an energy storage of an EV coupled to the one or more EV charging dispensers to be provided to the distribution grid network.

In an example, the at least one high frequency transformer is to operate at 5 kilohertz or more. At least one of the plurality of second converters may receive a low voltage from a power generator coupled to the EV charging system, the power generator to generate the low voltage from an ammonia-based source. At least one other of the plurality of second converters may receive the low voltage from the at least one high frequency transformer and provide the third DC voltage to the one or more EV dispensers using the low voltage.

In an example, the EV charging system further includes a controller to obtain power telemetry information from a distribution grid network that provides the grid power, and based at least in part thereon, to cause the EV charging system to compensate the distribution grid network for at least one of reactive power, harmonic current, or voltage sag. The EV charging system may integrate the one or more EV charging dispensers to enable one or more EVs to directly couple to the EV charging system.

In another aspect, an EV charging system comprises: a grid-tie module to directly couple to a distribution grid network at a grid connection and convert a grid voltage to a plurality of high frequency AC voltages; at least one high frequency transformer coupled to the grid-tie module to receive the plurality of high frequency AC voltages and to output a plurality of electrically isolated high frequency AC voltages; and a plurality of EV chargers coupled to the at least one high frequency transformer. Each of the plurality of EV chargers may receive one of the plurality of electrically isolated high frequency AC voltages and provide a DC voltage to at least one EV charging dispenser.

In an example, each of the plurality of EV chargers comprises at least one output stage comprising: an AC-DC converter coupled to the at least one high frequency transformer to receive one of the plurality of electrically isolated high frequency AC voltages and output a first DC voltage; and a DC-DC converter coupled to the AC-DC converter to receive the first DC voltage and output the DC voltage. The grid-tie module may include a plurality of input stages. Each of the plurality of input stages may comprise: an AC-DC converter to receive the grid voltage and output a second DC voltage; and a DC-AC converter coupled to the AC-DC converter to receive the second DC voltage and output the high frequency AC voltage. A first EV charger may comprise a plurality of output stages. A controller may configure the first EV charger to cascade the plurality of output stages to provide the DC voltage comprising a charging voltage.

In an example, the at least one high frequency transformer comprises a single transformer having a single primary winding coupled to the grid-tie module and a plurality of secondary windings, where each of the plurality of secondary windings is coupled to one of the plurality of EV chargers.

In an example, the EV charging system further comprises a controller to control a first EV charger to provide a first DC voltage at a charging voltage level to a first EV charging dispenser in a first mode and to provide a second DC voltage at a charging current level to the first EV charging dispenser in a second mode. The controller may select one of the first mode and the second mode based at least in part on status information of an EV coupled to the first EV charging dispenser. The controller may control the grid-tie module to compensate for one or more of reactive power, harmonic current, or voltage sag.

In an example, the EV charging system further comprises a storage converter coupled to the at least one high frequency transformer. The storage converter may receive energy from a storage device coupled to the EV charging system and convert the energy to a second high frequency AC voltage, and provide the second high frequency AC voltage to the at least one high frequency transformer.

In yet another aspect, a method includes: receiving, in an EV charging system directly coupled to a distribution grid network, a grid voltage at a grid frequency; converting, in a first input stage of the EV charging system, the grid voltage to a first high frequency AC voltage; transforming the first high frequency AC voltage to a second high frequency AC voltage; converting, in a first output stage of the EV charging system, the second high frequency AC voltage to a first DC voltage; and providing the first DC voltage to at least one EV charging station coupled to the EV charging system.

In an example, the method further comprises providing the first DC voltage to a plurality of EV charging stations coupled to the EV charging system. The method may further include: in a first mode, providing the first DC voltage at a charging voltage level to the at least one EV charging station based at least in part on status information of a first EV coupled to the at least one EV charging station; and in a second mode, providing the first DC voltage at a charging current level to the at least one EV charging station based at least in part on status information of a second EV coupled to the at least one EV charging station.

In yet a further aspect, a method includes: receiving, in an EV charging system directly coupled to a distribution grid network, EV power from an EV coupled to the EV charging system; converting, in a first output stage of the EV charging system coupled to the EV, a DC voltage of the EV power to a second high frequency AC voltage; transforming the second high frequency AC voltage to a first high frequency AC voltage; converting, in a first input stage of the EV charging system coupled to the distribution grid network, the first high frequency AC voltage to a grid voltage and a grid frequency; and providing power to the distribution grid network from the first input stage, the power at the grid voltage and the grid frequency.

In an example, the method further comprises: providing the power to the distribution grid network in a reverse mode; and receiving grid power from the distribution grid network and using the grid power to provide a DC voltage to at least one other EV in a forward mode.

In an example, the method further comprises: communicating information between a controller of the EV charging system and the EV; based at least in part on the information, determining that the EV is capable of providing the EV power; and configuring circuitry of the EV charging system for the reverse mode in response to the determining.

