Inverter operation modes
Disclosed herein is a three-phase, grid interactive inverter capable of multiple modes of operation including: a normal mode for transferring DC power to a utility grid, a constant AC current mode for limiting inverter output, a constant DC voltage mode used for DC testing, and a PV array simulation mode for testing of other inverters in the manufacturing process.
1 . A three-phase inverter that connects a photovoltaic panel to an AC utility grid comprising:
a set of transistors that convert DC power to AC power;
a digital signal processor that controls said transistors; and
a control algorithm that controls said transistors to operate in normal operation mode as well as at least one user selectable test mode.
2 . The inverter of claim 1 wherein said at least one test mode comprises a constant DC voltage mode in which power is allowed to flow either from a DC side of said inverter to an AC side or said inverter or from said AC side to said DC side as required to maintain a substantially constant voltage on said DC side of said inverter.
3 . The inverter of claim 2 wherein said constant DC voltage mode is used to test for proper installation of a photovoltaic panel that is electrically connected to the DC side of said inverter.
4 . The inverter of claim 1 wherein said at least one test mode comprises a PV simulation mode.
5 . The inverter of claim 4 wherein said inverter maintains voltage and limits current at the DC side of said inverter in a way that is substantially similar to the voltage-current characteristics of a PV array.
6 . The inverter of claim 2 wherein said at least one test mode comprises a PV simulation mode.
7 . The inverter of claim 6 wherein said inverter maintains voltage and limits current at the DC side of said inverter in a way that is substantially similar to the voltage-current characteristics of a PV array.
8 . A method of operating a three phase inverter for a batteryless photovoltaic system comprising the steps of:
providing a set of transistors that convert DC power to AC power;
providing a digital signal processor that controls said transistors; and
controlling said transistors to operate in normal operation mode as well as at least one user selectable test mode.
9 . The method of claim 8 wherein controlling said transistors to operate in said at least one of said test modes comprises controlling said transistors to operate in a constant DC voltage mode which comprises allowing power to flow either from a DC side of said inverter to an AC side or said inverter or from said AC side to said DC side as required to maintain a substantially constant voltage on said DC side of said inverter.
10 . The inverter of claim 9 wherein said transistors are controlled to operate in said constant DC voltage mode to test for proper installation of a photovoltaic panel that is electrically connected to the DC side of said inverter.
11 . The inverter of claim 8 wherein controlling said transistors to operate in said at least one of said test modes comprises controlling said transistors to operate in a PV simulation mode.
12 . The inverter of claim 11 wherein controlling said transistors to operate in said PV simulation mode comprises maintaining voltage and limiting current at the DC side of said inverter in a way that is substantially similar to the voltage-current characteristics of a PV array.
13 . The inverter of claim 9 wherein controlling said transistors to operate in said at least one of said test modes comprises controlling said transistors to operate in a PV simulation mode.
14 . The inverter of claim 13 wherein controlling said transistors to operate in said PV simulation mode comprises maintaining voltage and limiting current at the DC side of said inverter in a way that is substantially similar to the voltage-current characteristics of a PV array.