HIGH FREQUENCY HIGH POWER CONVERTER SYSTEM
A high frequency high power converter system comprises: a plurality of resonant tank circuits arranged in parallel, a plurality of transformers, each transformer having a single primary winding and a plurality of secondary windings, and a vacuum electronic device, the output of each resonant tank circuit being applied to a respective different transformer and the outputs of the transformers being arranged to drive the vacuum electronic device.
1 . A high frequency high power converter system comprises: a plurality of resonant tank circuits arranged in parallel, a plurality of transformers, each transformer having a single primary winding and a plurality of secondary windings, and a vacuum electronic device, the output of each resonant tank circuit being applied to a respective different transformer and the outputs of the transformers being arranged to drive the vacuum electronic device.
2 . The system as claimed in claim 1 , wherein the vacuum electronic device is a magnetron.
3 . The system as claimed in claim 2 , wherein the magnetron has a continuous wave output.
4 . The system as claimed in claim 1 , wherein each of the plurality of resonant tank circuits is a series resonant, series loaded resonant tank.
5 . The system as claimed in claim 1 , including a plurality of inverter circuits, each inverter circuit comprising a plurality of semiconductor switches, and a respective different inverter of said plurality being connected to the input of each of the plurality of resonant tank circuits.
6 . The system as claimed in claim 5 , wherein each of the plurality of inverter circuits comprises four semiconductor switches connected as an H-bridge.
7 . The system of claim 5 , wherein the semiconductor switches are IGBT switches.
8 . The system as claimed in any of claim 5 , wherein the inverter circuits are controlled to provide substantially zero current soft switching of the semiconductor switches.
9 . The system of claim 8 , and including combined frequency and phase shift modulation, CFPM, to control the inverter circuits to provide substantially zero current soft switching.
10 . The system of claim 9 , and including a modulation index calculator to calculate the modulation index, MI, used to apply CFPM where
MI
=
F
2
(
F
4
Q
2
+
F
2
+
Q
2
-
2
F
2
Q
2
)
where Q is the tank quality factor and F is the ratio between the switching frequency and the tank resonant frequency.
11 . The system as claimed in claim 8 , and including a tracking arrangement to counteract any deviation from substantially zero current soft switching of the semiconductor switches.
12 . The system as claimed in claim 11 , wherein the tracking arrangement generates a correction frequency to provide substantially zero current soft switching of the semiconductor switches.
13 . The system as claimed in claim 1 , and including a respective high voltage rectifier connected to the each secondary winding of the plurality of secondary windings.
14 . The system as claimed in claim 13 , wherein a capacitance is connected across the output of each high voltage rectifier and the capacitances are connected in series with one another.
15 . The system as claimed in claim 1 , wherein three transformers are included and the voltage applied to the primary windings of the three transformers is mutually phase shifted by 120 degrees.
16 . The system as claimed in claim 1 , and including a utility interface power converter having an input for receiving primary power and an output for applying power to the plurality of resonant circuits via a common dc link.
17 . The system as claimed in claim 16 , wherein the utility interface power converter includes a plurality of solid state switches and including a controller for controlling the state of the switches using pulse width modulation.
18 . The system as claimed in claim 1 , wherein the power level is about 100 kW, the switching frequency is some tens of kHz, and the tank quality factor at full power is about 2.5.