Hybrid inverter power control system for PV string, battery, grid and back-up loads
A string inverter for use with a photovoltaic array includes a string-level DC input channel for receiving DC power from a photovoltaic array. The input channel performs channel-level maximum power point tracking. An input-output channel connects the string inverter to a battery pack. A DC to DC buck-boost circuit between the at least one DC input channel and the at least one input-output channel prevents more than a predetermined amount of DC voltage from reaching the battery pack. A DC to AC inverter circuit having an AC output serving as an output of the string inverter. A revenue grade power meter is configured to measure the AC output of the string inverter.
1. A string inverter for use with a photovoltaic array and configured to supply power to one or more back-up loads, the string inverter comprising:
at least one string-level DC input channel for receiving DC power from a photovoltaic array, wherein the at least one input channel performs maximum power point tracking;
at least one input-output channel for connecting the string inverter to a battery pack;
a DC to DC buck-boost circuit coupled between the at least one string-level DC input channel and the at least one input-output channel for preventing more than a predetermined amount of DC voltage from reaching the battery pack;
a DC to AC inverter circuit having an output terminal;
a revenue grade power meter configured to measure an AC output of the string inverter provided on the output terminal; and
a switch controlling a flow of power from the string inverter to the one or more back-up loads, the switch being a three-position switch, wherein in a first position, AC power is permitted to flow from the string inverter to a load side of a customer utility meter and the one or more back-up loads, in a second position, power is permitted to flow from the load side of a customer utility meter to the one or more back-up loads bypassing the string inverter with inverter output disabled, and in a third position, all circuits tied to the string inverter's output are electrically disconnected from the string inverter.
2. The string inverter according to claim 1 , wherein the string inverter is operable to receive and rectify AC power into DC power, and to supply the DC power to the battery pack to charge it.
3. The string inverter according to claim 1 , further comprising a DC disconnect switch operable to interrupt all DC input sources from reaching the string inverter.
4. A string inverter for use with a photovoltaic array, comprising:
at least one string-level DC input channel for receiving DC power from a photovoltaic array, wherein the at least one input channel performs maximum power point tracking;
at least one input-output channel for connecting the string inverter to a battery pack;
a DC to DC buck-boost circuit coupled between the at least one string-level DC input channel and the at least one input-output channel for preventing more than a predetermined amount of DC voltage from reaching the battery pack;
a DC to AC inverter circuit having an output terminal;
a revenue grade power meter configured to measure an AC output of the string inverter provided on the output terminal;
a first circuit for metering a total DC power received at the at least one DC input channel from the photovoltaic array;
a second circuit for metering a total DC power received at the at least one input-output channel from the battery pack; and
a controller programmed to determine the portion of total AC output measured by the revenue grade power meter attributable to the at least one DC input channel and the at least one input-output channel respectively.
5. The string inverter according to claim 4 , further comprising a wireless transmitter that transmits the respective portions of total AC output attributable to the at least one DC input channel and the at least one input-output channel to a network-connected wireless gateway.
6. A string inverter for use with a photovoltaic array, comprising:
at least one string-level DC input channel for receiving DC power from a photovoltaic array;
at least one input-output channel for connecting the string inverter to a battery pack;
a DC to DC buck-boost circuit coupled between the at least one string-level DC input channel and the at least one input-output channel, the DC to DC buck-boost being configured to prevent more than a predetermined amount of DC voltage from reaching the battery pack;
a DC to AC inverter circuit having an output terminal;
a revenue grade power meter configured to measure an AC output of the string inverter provided on the output terminal;
a first circuit for metering a total DC power received at the at least one DC input channel from the photovoltaic array;
a second circuit for metering a total DC power received at the at least one input-output channel from the battery pack; and
a controller programmed to determine the portion of total AC output measured by the revenue grade power meter attributable to the at least one DC input channel and the at least one input-output channel respectively.
7. The string inverter according to claim 6 , wherein the DC to DC buck-boost circuit is coupled to the at least one string-level DC input channel.
8. The string inverter according to claim 6 , wherein the DC to DC buck-boost circuit is coupled to the at least one input-output channel.
9. The string inverter according to claim 6 configured to supply output power to one or more back-up loads.
10. The string inverter according to claim 9 , further comprising a switch controlling a flow of power from the string inverter to the one or more back-up loads.
11. The string inverter according to claim 6 , wherein the string inverter is operable to receive and rectify AC power to DC power, and to supply the DC power to the battery pack to charge it.
12. The string inverter according to claim 6 , further comprising a DC disconnect switch operable to interrupt all DC input sources from reaching the string inverter.
13. The string inverter according to claim 6 , further comprising a wireless transmitter that transmits the respective portions of total AC output attributable to the at least one DC input channel and the at least one input-output channel to a network-connected wireless gateway.
14. A string inverter for use with a photovoltaic array, comprising:
at least one string-level DC input channel for receiving DC power from a photovoltaic array;
at least one input-output channel for connecting the string inverter to a battery pack;
a DC to DC buck-boost circuit coupled between the at least one string-level DC input channel and the at least one input-output channel, the DC to DC buck-boost being configured to prevent more than a predetermined amount of DC voltage from reaching the battery pack;
a DC to AC inverter circuit having an output terminal;
a revenue grade power meter configured to measure an AC output of the string inverter provided on the output terminal; and
a three-position switch controlling a flow of power through the string inverter, wherein the switch is configured so that in a first state, AC power is permitted to flow from the string inverter to a load side of a customer utility meter and one or more back-up loads, in a second state, power is permitted to flow from the load side of a customer utility meter to the one or more back-up loads bypassing the string inverter with inverter output disabled, and in a third state, all circuits tied to the string inverter's output are electrically disconnected from the inverter.