Photovoltaic module-mounted AC inverter
View Patent ↗A photovoltaic module-mounted AC inverter circuit uses one or more integrated circuits, several switches, solid dielectric capacitors for filtering and energy storage, inductors for power conversion and ancillary components to support the above elements in operation. The integrated circuit includes all monitoring, control, and communications circuitry needed to operate the inverter. The integrated circuit controls the switches in both an input boost converter and a single-phase or multi-phase output buck converter. The integrated circuit also monitors all power processing voltages and currents of the inverter and can take appropriate action to limit power dissipation in the inverter, maximize the available power from the associated PV module and shut down the inverter output if the grid conditions so warrant. The integrated circuit implements power line communications by monitoring the AC wiring for signals and generating communications signals via the same pulse-width modulation system used to generate the AC power.
1. An apparatus for communicating using power line communications comprising:
an inverter, comprising:
an input terminal for receiving DC input from a photovoltaic module;
an output terminal for coupling an AC output, converted from the DC input, to a power line;
a power conversion module for converting the DC input to the AC output;
a monitoring system for monitoring the DC input and the AC output and forming data representative of at least one of the DC input or AC output;
a control system for controlling the power conversion module; and
a communications system electrically connected to the power monitoring system and the control system; and
wherein:
(i.) the monitoring system detects an analog communication signal on the power line and converts the analog communication signal to a digital communication signal for processing by the communications system;
(ii.) the communications system encodes the data for external communication and sends the encoded data to the control system; and
(iii.) the control system, based on the encoded data, drives the power conversion module to modulate a carrier signal to communicate the encoded data via the power line.
2. The apparatus of claim 1 wherein the monitoring system, the control system, and the communications system are implemented on a single integrated circuit.
3. The apparatus of claim 1 where the analog communication signal comprises information for controlling the inverter, and the data for external communication comprises performance data for each of the photovoltaic module and the inverter.
4. The apparatus of claim 1 where the communications system (a) maintains a local address unique to the inverter, and (b) detects whether the digital communication signal comprises a message address that matches the local address, and (c) when the message address matches the local address, determines a control action based on message content for controlling the inverter.
5. The apparatus of claim 3 wherein (a) the carrier signal is generated by the inverter and the power conversion module generates a modulated carrier signal, or (b) the carrier signal is generated externally from the inverter and the power conversion module load modulates the carrier signal at the output terminal.
6. The apparatus of claim 1 wherein the power conversion module is a buck converter, and wherein the inverter further comprises a boost converter and a charge storage.
7. The apparatus of claim 1 where the monitoring system determines a required DC input voltage to extract maximum power from the photovoltaic module.
8. The apparatus of claim 1 where the monitoring system determines if both voltage and frequency of the AC output are within predetermined limits of operation, and if at least one of the voltage and the frequency is outside of the predetermined limits, the control system disables the inverter.
9. The apparatus of claim 4 where the monitoring system compares the phase of an AC output voltage to the phase of an AC output current at the output terminal.
10. The apparatus of claim 4 where the monitoring system determines if the inverter is connected to each of the photovoltaic module and the power line and, if the inverter is disconnected from at least one of the photovoltaic module or the power line, sends a signal to the control system to shut down the inverter.
11. The apparatus of claim 1 , wherein the communications system receives external commands including enabling or disabling the inverter, adjusting inverter performance parameters, changing maximum power-point tracking operating modes, and initiating inverter self-test functions.
12. The apparatus of claim 6 , wherein the booster converter is a single-inductor, bipolar-output boost converter or a tandem single-inductor, bipolar-output boost converter.
13. The apparatus of claim 6 , wherein the boost converter further comprises two parallel connected inductors operating in quadrature phase so that neither inductor is simultaneously discharged.
14. The apparatus of claim 1 , wherein the monitoring system comprises voltage and current sensors to determine if the inverter has been disconnected or connected to the photovoltaic module or an AC grid and communicating a status of the inverter using external communications.
15. The apparatus of claim 14 , further comprising hot-swap capability wherein upon sensing the inverter is disconnected or connected to the photovoltaic module or an AC grid, the control system generates corresponding timing signals for the power conversion module.