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Expert knowledge-based peak current mode control of electrosurgical generators for improved output power regulation

Muhammad Mohsin Rafiq
Muhammad Mohsin Rafiq
, 
Asier Ibeas
Asier Ibeas
 and 
Nasim Ullah
Nasim Ullah
   | Nov 17, 2023
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Published Online: Nov 17, 2023
Page range: 32 - 46
Received: May 15, 2023
Accepted: Nov 13, 2023
DOI: https://doi.org/10.2478/joeb-2023-0005
Keywords
© 2023 Muhammad Mohsin Rafiq et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Desired output characteristic. Current in amperes and voltage in volts.
Desired output characteristic. Current in amperes and voltage in volts.

Figure 2

Circuit diagram of Electrosurgical generator.
Circuit diagram of Electrosurgical generator.

Figure 3

Buck converter.
Buck converter.

Figure 4

High frequency DC-AC Inverter.
High frequency DC-AC Inverter.

Figure 5

CMC buck output current waveform.
CMC buck output current waveform.

Figure 6:

Switch network terminal quantities of buck converter.
Switch network terminal quantities of buck converter.

Figure 7

Waveforms for circuit.
Waveforms for circuit.

Figure 8

Averaged switch network derived from equation (7).
Averaged switch network derived from equation (7).

Figure 9

Maximum voltage limit using duty cycle.
Maximum voltage limit using duty cycle.

Figure 10

Waveforms in PCM control.
Waveforms in PCM control.

Figure 11

Realization of Peak current mode controller.
Realization of Peak current mode controller.

Figure 12

PCM control waveforms showing instability
PCM control waveforms showing instability

Figure 13

PCM controller’s stability is improved by adding an artificial ramp.
PCM controller’s stability is improved by adding an artificial ramp.

Figure 14

Steady-state inductor current.
Steady-state inductor current.

Figure 15

Peak to average error in ideal curve using PCMC.
Peak to average error in ideal curve using PCMC.

Figure 16

PCM control with and without artificial ramp.
PCM control with and without artificial ramp.

Figure 17

Impact of PAE and artificial ramp error.
Impact of PAE and artificial ramp error.

Figure 18

Transient response under step load.
Transient response under step load.

Figure 19

Rules derivation from ideal curve.
Rules derivation from ideal curve.

Figure 20

Output curve using EK-PCMC.
Output curve using EK-PCMC.

Figure 21

Block diagram of ESU with EK-PCMC control.
Block diagram of ESU with EK-PCMC control.

Figure 22

Comparison of VI curves for Ideal, PCMC, and EK-PCMC.
Comparison of VI curves for Ideal, PCMC, and EK-PCMC.

Figure 23

Output current comparison under load variations.
Output current comparison under load variations.

Figure 24

Output voltage comparison under load variations.
Output voltage comparison under load variations.

Figure 26

Output Power for decreasing load steps.
Output Power for decreasing load steps.

Figure 27

Output power (zoomed).
Output power (zoomed).

Figure 28

Output Power for increasing load steps.
Output Power for increasing load steps.

Performance comparison between proposed and previous work for increasing load.

Performance criteria Previous work EK-PCMC
Step Response at 50W power at Impedance=90 ohm at time 0s
Power overshoot 4.20% 0.188%
Rise time of Power 0.89 ms 0.0047 ms
Settling time of power 2.1 ms 0.017 ms
Load step from Z1 to Z2(90 ohm to 120 ohm) at time 0.01s
Power overshoot 9% 3.2%
Load step from Z2 to Z3(120 ohm to 150 ohm) at time 0.02s
Power overshoot 10% 2.6%

Parameters of buck converter.

Parameter Value Unit
Input voltage (Vg) 50 Volt
Maximum output voltage (Vb) 45 Volt
Maximum average current (Iavg) 3 Ampere
Duty cycle (D) 46 Percent
Switching frequency (fs) 1 x 106 Hz
Inductance (L) 100 x 10−6 Henry

Parameters of inverter.

Parameter Value Unit
Maximum Input DC voltage (yfc) 45 Volt
Maximum output voltage (VRMS) 120 Volt
Maximum output current (IRMS) 1 Ampere
Switching frequency (fs) 500 x 103 Hz
Transformer turn ratio 1:3 -
Impedance range 10-340 Ohms
Reference power command 50 Watt

Performance comparison between proposed and previous work for decreasing load.

Performance criteria Previous work EK-PCMC
Step Response at 50W power at Impedance=90 ohm
Power overshoot 4.20% 0.188%
Rise time of Power 0.89 ms 0.0047 ms
Settling time of power 2.1 ms 0.017 ms
Load step from Z1 to Z2(90 ohm to 60 ohm) at time 0.01s
Power Undershoot NA 3.2%
Load step from Z2 to Z3(120 ohm to 30 ohm) at time 0.02s
Power Undershoot NA (In constant current mode)

Performance comparison between proposed and PCMC.

Controller Integral square error (ISE) Integral absolute error (IAE)
PCMC 0.3190 0.0175
EK-PCMC 0.0822 0.0036
eISSN:
1891-5469
Language:
English
Publication timeframe:
Volume Open
Journal Subjects:
Engineering, Bioengineering and Biomedical Engineering, Biomedical Electronics, Life Sciences, Biophysics, Medicine, Biomedical Engineering, Physics, Spectroscopy and Metrology
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