Minimum-cost EVPV for vehicle-solar-grid integration
This invention consists of an apparatus to interface an electric vehicle battery with a solar photovoltaic system and a method of using the apparatus to provide back up power during grid outages and ancillary service revenue from the grid. The apparatus uses the solar PV inverter to provide bidirectional power flow from the battery during night-time hours, or whenever the solar array is producing insufficient power. The apparatus thus consists only of switches and control and measurement equipment. It relies on the otherwise underutilized inverter and the on-board vehicle battery charger as the power electronic components, thus minimizing cost.
1. An apparatus for bidirectional power conduction from and to an electric vehicle comprising:
connection, switching and control devices to permit the apparatus to provide ancillary services to the electric utility grid while also providing electric energy to recharge the electric vehicle comprising;
drawing DC power from a battery of the electric vehicle and passing the power through a DC connection and converting it to AC power by feeding it to an inverter of an existing photovoltaic power system whenever the photovoltaic array is producing power worth less that the ancillary services enabled by the apparatus, and
putting electric energy back into the vehicle battery through an AC connection to an existing onboard battery charger of the vehicle, both of said DC and AC connections being connected to the vehicle simultaneously and continuously while it is parked for charging.
2. The apparatus of claim 1 in which the output only AC connection to the vehicle is a standard AC charging plug allowing it to be connected to the on-board charger of the electric vehicle.
3. The apparatus of claim 1 in which the DC connection to the vehicle is a standard DC quick charge connector allowing it to be directly connected to the propulsion battery of the electric vehicle.
4. The apparatus of claim 1 containing a local site controller, to control the functions of vehicle charging and discharging to provide ancillary service to the grid and backup power in emergencies.
5. The apparatus of claim 1 in which a data acquisition and control system is included to permit control in response to requests from the relevant RTO/ISO delivered via an aggregator or curtailment service provider over the internet or wireless telephone of the output of the inverter in up regulation and the vehicle charger in down regulation.
6. The apparatus of claim 1 in which a resistor is are used to connect the input of the inverter to the DC power to keep a small current flowing with which to keep the inverter synchronized when it is turned off.
7. The apparatus of claim 1 containing one or more revenue-grade current transformer meters which are used to measure performance of ancillary services to the grid.
8. The apparatus of claim 1 containing communication means which permit ancillary service commands such as for frequency regulation and demand response to be supplied to the apparatus and the resulting data on the response of the apparatus to be supplied to the regulator of electric energy supply such as a grid independent system organization (ISO).
9. The apparatus of claim 1 which is connected to the inverter of an existing a photovoltaic (PV) power system via a switch which can provide for PV power flow during the day and ancillary power flow at night when no PV energy is produced.
10. The apparatus of claim 1 in which the AC and DC connections can be switched or manually ported back and forth from the vehicle to a stationary supplementary battery.
11. The apparatus of claim 10 in which the supplementary battery is permanently connected.
12. The apparatus of claim 1 which is connected to a building power wiring, which is equipped with an automatic or manual transfer switch to isolate the building and the apparatus from the grid in event of a power failure, so that the vehicle battery can provide back-up power to the building.
13. The apparatus of claim 12 to provide backup power to a photovoltaic system from an electric vehicle battery by interconnection of the DC quick charge port of the electric vehicle with the DC input to the inverter of the PV system to provide AC output from the PV system for general use.
14. The apparatus of claim 1 to provide ancillary services to the relevant grid Regional Transmission Operator/Independent System Operator (RTO/ISO) by providing power to the grid from the Electric Vehicle battery in response to frequency regulation requests from the ISO for “up Reg.” and taking power from the grid to recharge the battery in response to requests for “down Reg.” or other Demand Response services during those times when the photovoltaic array is not producing enough power to offset the revenue from ancillary services.