MARS MV converter input plane design and implementation

Shuai Lu, Prof El-Sharkawi

EE, University of Washington

March 29, 2005

Outline

• Input plane components overview

• MV switching circuit topology

• Converter startup power supply

• Switching operation and AB selection logic

• MV voltage and current measurement

Input plane components

• Physically:– MV switching board, including MV switches,

voltage dividers, (isolation diodes), charging resistors, etc. Mostly HV parts

– MV logic board, including converter startup power supply, switching control logic circuit, and MV voltage sensing circuit. All LV parts.

Input plane components

• Logically:– MV switching circuit– Converter startup power supply– Switching operation logic– AB selection logic– MV voltage sensing

MV switching circuit

ConverterB

ConverterA

V_in_A

V_in_B

S1_AS2

(2)(1) (3) (4) (5)

-10kV in400V out

S1_B3k

Diodes: isolate positive voltage from converter input

S1_A and S1_B: 10kV isolation switches

3k ohm resistor: limits charging current when connecting converters to 10kV

S2: bypass 10kV isolation switch

MV switching circuit

• Rules behind switching operations:– Two converters, one in cold standby (means

when one is working, another is isolated from 10kV)

– When one converter has fault, it should be isolated so that the other one will work.

– Switches not close to a load or open with current flowing at voltage higher than 500V (means S1 and S2 have to be latching switches, and operated at low voltage)

Converter startup power supply

• Functions:– Supply power to logic circuit to operate switches– Supply power to converter gate signal for startup. Requires 20-

25W, 10V for at least 4ms.– Must be available when converter is not running. Therefore after

converter is shutdown for load fault, it can still be started.• The last two points mean that the startup power supply

has to be periodical pulse. Otherwise, it’ll consume too much energy. (25W constantly)

• Startup power supply has to be available both at low voltage for switching operations and high voltage for starting converter.

• A 12V voltage regulator with input from 100V to 10kV, positive or negative.

Converter startup power supply

Waveform at positive voltage (Sing_vin=0), switches are being opened:

1: VCC (inverted) 2: NAND gate output

Converter startup power supply

Waveform at positive voltage (Sing_vin=0), switches are already opened:

1: VCC (inverted) 2: NAND gate output

Converter startup power supply

Waveform at negative voltage (Sing_vin=1), when switches are being closed:

1: counter clock signal

2: fault detection circuit voltage sensing output (ignore the spikes, it can be seen as VCC inverted)

Switching operation logic

• Functions:– Open all switches (S1 and S2) at positive

voltage– Close S1 at negative voltage – Check fault at place (4), i.e., converter input. If

fault exists, open S1.

Switching operation logic

Voltage polarity sensing

Fault voltage detection

VCC low detection

30 Hz Counter

Logic functions

&0

0

0 0

Relay driving circuit

Switching operation logic circuit diagram

Switching operation logic

Open all switchesVflag=1

V_in=-500V

Close S1_A

Fault

No fault

Open S1_A,

A_Ok=1Close S1_B

Fault

No fault

Open S1_B,

t0 t1 t2 t3 t4 t5

Vflag=1

Vflag=0

A_Ok=0 B_Ok=0

B_Ok=1 Vflag=0

V_in=+500V

Logic sequence for switching operations

A_OK and B_OK are indicating the fault status of converter input. They are sent to node controller.

Switching operation logic

Vin = -500V. When S1_A has 250k fault, S1_B has 500k fault.

1: clock signal

2: LPF(CA3140) output in fault detection circuit

Switching operation logic

Vin = -500V. When S1_A has 250k fault, S1_B has no fault.

1: clock signal

2: LPF(CA3140) output in fault detection circuit

Switching operation logic

Vin = -500V. When S1_A no fault, S1_B has no fault.

1: clock signal

2: LPF(CA3140) output in fault detection circuit

Switching operation logic

Vin = -500V. When S1_A has 250k fault, S1_B has 500k fault. Whole process view.

1: clock signal2: LPF(CA3140) output in fault detection circuit

AB selection logic

• Functions:– Close S2 after Vin is higher than threshold

voltage(5.3kV).– Close S3 to give converter gate signal to start

it.– When converter A works, open S1_B to

isolate B from 10kV.– When converter A doesn’t work, open S1_A

and starts B.

AB selection logic

Vlotage sensing hysteresis circuit

400V_OK detection

Status memory(counter with cap)

Logic functions Relay driving circuit

clock

reset

AB selection logic circuit diagram

AB selection logic

When converter is successfully started:

1: S3_A closing signal

2: VCC (inverted)

AB selection logic

When converter is successfully started:

1: S3_A closing signal

2: S2 closing signal (inverted) 15ms earlier than S3_A closing signal

AB selection logic

When converter is not successfully started:

1: S3_A closing signal

2: VCC (inverted) (the drop at the end is caused by the 3.6 ohm resistor simulating converter gate driving circuit)

Voltage measurement result

Vin 6.03 6.53 7.03 7.53 8.04 9.04 9.54 10.04 10.55

Vmeas 6.015 6.515 7.017 7.529 8.037 9.045 9.551 10.046 10.573

1 2 3 4 5 6 7 8 96

6.5

7

7.5

8

8.5

9

9.5

10

10.5

11

Measurement

Cab

le V

olta

ge(k

V)

real valueVmeas