Systems to connect multiple direct current energy sources to an alternating current system
View Patent ↗High voltage direct current systems to connect direct current energy sources to an alternating current system. In one aspect, a system includes a plurality of direct current modules having variable direct current inputs; an inverter; and a direct current bus to connect the direct current modules to the inverter, where the bus is configured to operate at a nominal voltage higher than 100 volts and to operate within 10 percent of the nominal operating voltage.
1. A system, comprising:
a plurality of direct current modules having variable direct current inputs and each module having a step up converter;
an inverter; and
a direct current bus connecting the direct current modules to the inverter, the modules and the bus together being configured to operate at a nominal operating voltage higher than 100 volts and to operate within 10 percent of the nominal operating voltage.
2. The system of claim 1 , wherein each of the direct current modules comprises a controller to control a voltage output to the bus.
3. The system of claim 2 , further comprising:
a management module coupled to the bus and the plurality of direct current modules, the management module being configured to communicate with the direct current modules to control the output voltage on the bus.
4. The system of claim 3 , wherein the management module is further coupled to the inverter to control the voltage on the bus.
5. The system of claim 4 , wherein the management module is further connected to a web site to receive instructions to control the voltage on the bus.
6. The system of claim 5 , wherein the direct current modules are coupled with photovoltaic panels to increase output voltages from the photovoltaic panels.
7. The system of claim 6 , wherein the inverter is coupled to a power grid.
8. The system of claim 1 , wherein the inverter has a Zener characteristic.
9. The system of claim 1 , wherein the inverter represents a shunt regulator toward the bus.
10. The system of claim 1 , wherein the direct current modules are connected to the bus in a daisy chain.
11. The system of claim 1 , wherein the direct current modules are connected to a vicinity of the inverter in a star form for connection to the inverter.
12. The system of claim 1 , wherein the step up converter in each of the direct current modules comprises:
a boost converter having a first inductor;
a second inductor paired on a core with the first inductor; and
a half bridge rectifier circuit coupled with the second inductor to generate a direct current output to the bus.
13. The system of claim 12 , wherein the boost converter further comprises a transistor to implement a switch in the boost converter and a controller coupled to the transistor to control the switch to adjust an output voltage of the step up converter.
14. The system of claim 12 , wherein the boost converter provides a first portion of a voltage output of the step-up converter; and the rectifier circuit provides a second portion of the voltage output of the step-up converter.
15. The system of claim 14 , wherein the first portion and the second portion of the voltage output of the step-up converter are proportional to a ratio between the first inductor and the second inductor.
16. The system of claim 14 , wherein the boost converter further comprises a transistor to implement a switch in the boost converter, the voltage output of the step-up converter being higher than 100 volts, and the transistor having a breakdown voltage lower than 100 volts.
17. The system of claim 16 , wherein resistance between drain source connection in the transistor is less than ten milliohms when the transistor is in a saturated on mode.
18. The system of claim 12 , wherein outputs of the boost converter and the rectifier circuit are connected in serial.
19. An energy system, comprising:
a direct current bus;
a plurality of photovoltaic panels;
a plurality of direct current modules each including a step up converter and wherein the modules are coupled between the plurality of photovoltaic panels and the bus; and
an inverter coupled between the bus and a power grid, wherein the direct current modules and the bus are configured together to operate at a nominal voltage higher than 200 volts and to operate within 4 percent of the nominal voltage of the bus even when a current supplied by the photovoltaic panels is reduced to a level to power the inverter without substantial output to the power grid.
20. The system of claim 19 , wherein the inverter has a characteristic that resembles a Zener diode.