Grid synchronisation
The invention relates to a grid synchroniser for connecting an AC output of a power converter to the AC grid mains. In one aspect the invention provides a grid synchroniser comprising an inverter controller to control an AC output of the inverter, the controller including a receiver to receive grid data from a grid sensor location remote from said inverter. In another aspect we describe techniques for rapid removal of charge from a control terminal of a power switching device such as a MOSFET, IGBT or Thyristor using a particular driver circuit.
1. A circuit for transferring power to an alternating current (AC) grid, the circuit comprising:
a semiconductor device having a first terminal coupled to a first side of the AC grid, a second terminal coupled to a power source node and a gate terminal coupled to a gate drive node;
a gate drive circuit comprising:
a diode coupled between a second side of the AC grid and the gate drive node;
a zener diode coupled between the power source node and the gate drive node; and
a resistor coupled between the power source node and the gate drive node; and
a voltage divider, comprising:
a first divider resistor coupled between the first side of the AC grid and the diode; and
a second divider resistor coupled between the second terminal and the diode.
2. The circuit of claim 1 , wherein a value of the resistor is less than one fifth a resistance value of the first divider resistor.
3. The circuit of claim 1 , wherein a resistance value of the first and the second divider resistors is one megaohm.
4. The circuit of claim 1 wherein the resistor has a resistance between 20 kiloohms and 100 kiloohms.
5. The circuit of claim 1 wherein the semiconductor device comprises a Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT) or a Thyristor.
6. The circuit of claim 1 wherein the semiconductor device has a breakdown voltage of at least 100 Volts.
7. The circuit of claim 1 wherein the zener diode has a breakdown voltage of 15 Volts.
8. The circuit of claim 1 further comprising a power generation circuit coupled to the power source node.
9. A system for generating and transferring power to an alternating current (AC) grid, the system comprising:
a power generation circuit having a power output; and
a power transfer circuit comprising:
a semiconductor switch having a gate terminal, an input terminal coupled to the power output and an output terminal coupled the AC grid;
a drive circuit coupled to the gate terminal and comprising:
a diode having an anode coupled to the AC grid and a cathode coupled to the gate terminal;
a zener diode having a zener anode coupled to the power output and a zener cathode coupled to the gate terminal; and
a resistor coupled between the gate terminal and the power output; and
a voltage divider including a first divider resistor coupled between the AC grid and the anode of the diode, and a second divider resistor coupled between the power output and the anode of the diode.
10. The system of claim 9 wherein the power transfer circuit is a first power transfer circuit for transferring power to the AC grid during a first half-cycle of the AC grid and the system comprises a second power transfer circuit for transferring power to the AC grid during a second half-cycle of the AC grid.
11. The system of claim 10 wherein the first and the second power transfer circuits are isolated from the power generation circuit by a transformer.
12. The system of claim 9 , wherein a resistance value of the first and the second divider resistors is one megaohm.
13. The system of claim 9 , wherein a value of the resistor is less than one fifth a resistance value of the first divider resistor.
14. The system of claim 9 wherein the resistor has a resistance between 20 kiloohms and 100 kiloohms.
15. The system of claim 9 wherein the semiconductor switch comprises a Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT) or a Thyristor.
16. The system of claim 9 wherein the semiconductor switch has a breakdown voltage of at least 100 Volts.
17. The system of claim 9 wherein the zener diode has a breakdown voltage of 15 Volts.
18. The system of claim 9 wherein the power generation circuit comprises a plurality solar cells.
19. A system for generating and transferring power to an alternating current (AC) grid, the system comprising:
a power generation circuit having a power output;
a first power transfer circuit for transferring power to the AC gird during a first half cycle of the AC Grid, the first power transfer circuit comprising:
a semiconductor switch having a gate terminal, an input terminal coupled to the power output and an output terminal coupled the AC grid;
a drive circuit coupled to the gate terminal and comprising:
a diode having an anode coupled to the AC grid and a cathode coupled to the gate terminal;
a zener diode having a zener anode coupled to the power output and a zener cathode coupled to the gate terminal; and
a resistor coupled between the gate terminal and the power output;
a second power transfer circuit for transferring power to the AC grid during a second half cycle of the AC grid; and
a transformer isolating the first power transfer circuit from the second power transfer circuit.