Efficient switching for converter circuit
An apparatus may include a first switch leg connected between a first input terminal and an output terminal, the first switch leg comprising a first switch. The apparatus may also include a second switch leg connected between a second input terminal and the output terminal, the second switch leg comprising a second switch. The apparatus may further include a third switch leg connected between an input voltage midpoint node and the output terminal. A control circuit may control the first switch leg, the second switch leg, and the third switch leg.
1. A power system comprising:
a plurality of power sources configured to be connected in one of a series connection, a parallel connection, or a combination of series and parallel connections, wherein the plurality of power sources are further configured to generate direct current (DC) power;
a storage device configured to store the DC power and discharge the stored DC power;
an inverter comprising:
a first input terminal;
a second input terminal;
an output terminal;
an input voltage midpoint node;
a first switch leg connected between the first input terminal and the output terminal, wherein the first switch leg comprises a first switch;
a second switch leg connected between the second input terminal and the output terminal, wherein the second switch leg comprises a second switch;
a third switch leg connected between the input voltage midpoint node and the output terminal; and
a controller configured to control the inverter to convert at least one of the DC power, generated by the plurality of power sources, or the stored DC power, discharged by the storage device, to an alternating current (AC) voltage, by:
during a first time period, disabling the second switch leg, and alternately enabling the first switch leg and the third switch leg; and
during a second time period, disabling the first switch leg, and alternately enabling the second switch leg and the third switch leg; and
a link unit connected between the plurality of power sources and the inverter and further connected to the storage device, wherein the link unit is configured to cause the storage device to be charged by the DC power from the plurality of power sources, and wherein the link unit is further configured to cause the storage device to discharge the stored DC power to the inverter.
2. The power system of claim 1 , wherein the link unit is connected to the first input terminal and the second input terminal, and
wherein the link unit comprises a converter configured to perform at least one of:
converting power from the storage device to the inverter;
converting power from the plurality of power sources to the storage device; or
converting power from the inverter to the storage device.
3. The power system of claim 1 , wherein the plurality of power sources comprise at least one of:
photovoltaic panels connected in at least one of the series connection or the parallel connection, or
a bank of batteries.
4. The power system of claim 1 , wherein the first switch and the second switch comprise:
a metal-oxide semiconductor field effect transistor (MOSFET);
a bipolar junction transistor (BJT);
a silicon-carbide switch (SiC);
a gallium nitride (GaN) switch; or
a super-junction transistor.
5. The power system of claim 1 , wherein the third switch leg comprises two serially connected switches,
wherein each switch of the of the two serially connected switches comprises a diode, and
wherein anodes or cathodes of the two serially connected switches are connected to each other.
6. The power system of claim 5 , wherein each of the two serially connected switches is an insulated gate bipolar transistor (IGBT).
7. The power system of claim 1 , wherein the first input terminal and the second input terminal are connected to the plurality of power sources and to the storage device.
8. The power system of claim 1 , wherein the first time period corresponds to a first half of a period of a grid frequency, and
wherein the second time period corresponds to a second half of the period of the grid frequency.
9. The power system of claim 8 , wherein the controller is configured to, during the first time period, alternately enable the first switch leg and the third switch leg at a higher frequency than the grid frequency.
10. The power system of claim 8 , wherein the controller is configured to, during the second time period, alternately enable the second switch leg and the third switch leg at a higher frequency than the grid frequency.
11. The power system of claim 1 , wherein the controller is configured to alternately enable the first switch leg by controlling the first switch to alternate between an ON state and an OFF state.
12. The power system of claim 1 , wherein the controller is configured to alternately enable the second switch leg by controlling the second switch to alternate between an ON state and an OFF state.
13. The power system of claim 1 , further comprising:
a first capacitor connected between the first input terminal and the input voltage midpoint node, and
a second capacitor connected between the second input terminal and the input voltage midpoint node,
wherein each of the first switch leg and the second switch leg is configured to statically block a total voltage across the first capacitor and the second capacitor.
14. A method comprising:
controlling a link unit to discharge power from a storage device to an inverter connected to a plurality of power sources; and
converting, by the inverter and to the link unit, power from the plurality of power sources or the storage device,
wherein the inverter comprises:
a first input terminal, a second input terminal, an output terminal, and an input voltage midpoint node;
a first switch leg connected between the first input terminal and the output terminal,
wherein the first switch leg comprises a first switch;
a second switch leg connected between the second input terminal, and the output terminal, wherein the second switch leg comprises a second switch;
a third switch leg connected between the input voltage midpoint node and the output terminal, and
wherein the converting the power comprises:
during a first time period, disabling the second switch leg, and alternately enabling the first switch leg and the third switch leg; and
during a second time period, disabling the first switch leg, and alternately enabling the second switch leg and the third switch leg.
15. The method of claim 14 , wherein the converting the power further comprises converting, by the inverter, alternating current (AC) power from a grid to direct current (DC) power.
16. The method of claim 14 , wherein the alternately enabling the first switch leg comprises controlling the first switch to alternate between an ON state and an OFF state.
17. The method of claim 14 , wherein the alternately enabling the second switch leg comprises controlling the second switch to alternate between an ON state and an OFF state.
18. The method of claim 14 , wherein the first time period corresponds to a first half of a period of a grid frequency, and
wherein the second time period corresponds to a second half of the period of the grid frequency.
19. The method of claim 14 , wherein the alternately enabling the first switch leg and the third switch leg during the first time period comprises alternately enabling the first switch leg and the third switch leg at a frequency than a grid frequency.
20. The method of claim 14 , wherein the alternately enabling the second switch leg and the third switch leg during the second time period comprises alternately enabling the second switch leg and the third switch leg at a frequency higher than a grid frequency.