A 100kV Switch Mode Series Resonant Power Supply for Industrial Electrostatic Precipitators

This paper considers the design of a high voltage high frequency power supply for Industrial Electrostatic Precipitator (EPS) applications. The supply is based on a series resonant series-loaded converter. The main aim of this, university-industry partnership work is to design and experimentally validate the capability of the proposed configuration in achieving higher efficiency and more flexible transient response when compared with a traditional line frequency based power supply. Closed-loop behaviour of the power supply, during sparking events, is also investigated with a non-linear precipitator.

�To control the tank current, hence the DC output voltage of the ESP, whilst minimizing the semiconductor losses, a combined phase-shift and frequency control has been adopted.

�The chosen topology and control allow for zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off of the IGBTs of the lagging leg.

�The IGBTs of the leading leg experience hard-switched turn-off commutations andrequire additional snubber capacitors to achieve low dissipation operation.

2. CONTROL STRATEGY

1. SERIES RESONANT SERIES-LOADED POWER SUPPLY

3. PLECS SIMULATION RESULTS

Fig.2-Theoretical waveforms using frequency and phase-shift control.

Fig.1-Schematic of the single-phase power supply and control platform.

�Initially the power supply operates in the normal condition; the current follows the reference current and the final 100kV output voltage is reached after 0.06s.

�In the presence of a spark between the EPS electrodes, the tank current is rapidly reduced to zero by the current controller, with a very limited current spike, avoiding possible damage to the precipitator as well as the power supply.

�When the short-circuit dies away the control returns to voltage regulation modeand the voltage recovers at the maximum rate.

C

Ltank

3-phase

Supply

x6

Lf

Cf

RL

Voltage

Multiplier

GATE DRIVE

VOLTAGE

TRANSDUCER

A/D

Programmable Control

Platform

VABVdc

V

I

S1

S2 GATE SIGNALS

PROTECTION AND CONTROL MEASUREMENTS

Input

Rectifier

Ctank

HVHF_TR

Cstack_1

Cstack_2

Cstack_3

Cstack_4

Itank

S3

S4

A/D

Nonlinear

load

A

B

PEAK DETECTOR

CURRENT

TRANSDUCER

VOLTAGE

TRANSDUCER

3) SBE, Inc, Barre, Vermont, 05641-4854, USAE-mail: fabio.carastro@nottingham.ac.uk

2) Castlet Ltd ,Lincoln, LN3 4NR, UK1) University of Nottingham, Nottingham, NG7 2RD, UK

J. Leach2) and T. Hosking3)F. Carastro1), J. Clare1), A. Goodman1) and P. Wheeler1)

Description Symbol Value Load voltage V 100kV Load voltage ripple Vr <3% Load current I 2A Output power P 200kW Load voltage recovery V 1.5kV/ms Quality Factor Q 3 Switching frequency fsw 20 kHz P

ower

sup

ply

spec

ific

atio

n DC-link Vdc 600 V Tank inductor Ltank 0.027 mH Tank capacitor Ctank 2.04 µF Natural frequency f0 21.2 kHz EPS filter inductor Lf 3 mH EPS capacitance Cf 0.5 µF DC-link capacitor C 7 mF Transformer turn ratio N 1:47 D

esig

n R

esul

ts

Voltage multiplier gain km 4

Tab.1-Power supply specifications and design results.

Fig.4-Representative circuit waveforms during the regulation.Fig.3-Power supply current control loop.

4. EXPERIMENTAL SETUP

5. CLOSED-LOOP EXPERIMENTAL RESULTS (without voltage multiplier )

Fig.5-Experimantal setup.

Fig.6-Closed-loop experimental results during tank current regulation. Fig.7-Full power closed-loop experimental results.

� The designed PI controller is capable of tracking the tank current demand and soft-switching is kept during both transient and steady state conditions as Figure 6 shows.

� A maximum output voltage of 27.8 kV has been obtained. During this condition the controller is following a peak tank current demand of 600A, delivering an output power of 220kW as Figure 7 shows.

� Soft-switching operation is maintained during steady state conditions also in the presence of the voltage multiplier as Figure 8 shows.

� These results confirm the correct operation of the power supply, in line with the electrical and control design.

6. EXPERIMENTAL RESULTS (with voltage multiplier )

7. CONCLUSIONS

This paper has presented the design of a high voltage, high frequency, series resonant series-loaded power supply for industrial electrostatic precipitator applications. The electrical design and control of the series resonant power supply has been provided and verified by simulation results. Full power closed-loop experimental results presented have also demonstrated the validity of the proposed scheme in controlling the output voltage while maintaining soft-switching by indirect control of the resonant tank current. Full DC output voltage experimental results, including on-site electrostatic precipitator test operation will be provided in future papers to further investigate the effectiveness and limitations of the technology used.

Fig.8-Reduced power closed-loop experimental results with voltage multiplier.