Design of PLCbased system for linearity output voltage of AC–DC converter

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ScienceDirect
Energy Reports 8 (2022) 972–978
www.elsevier.com/locate/egyr

2021 8th International Conference on Power and Energy Systems Engineering (CPESE 2021),
10–12 September 2021, Fukuoka, Japan

Design of PLC-based system for linearity output voltage of AC–DC
converter
Sawai Pongswatda , Krit Smerpitaka ,∗, Farzin Asadib , Teerawat Thepmaneea
a

School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Ladkrabang, Bangkok, 10520, Thailand
b Department of Electrical and Electronics Engineering, Maltepe University, Istanbul, Turkey
Received 26 October 2021; accepted 7 November 2021
Available online 26 November 2021

Abstract
This paper presents the PLC-Based system for controlling the SCR power module which is AC–DC converter proposes
to linearity output voltage with trigger signal. The technique converted the trigger signal by arccosine function and analog
module in the PLC. Converted signal from PLC system is fed to SCR power module instant the traditional signal. Proposed of
this paper describes the PLC hardware configuration, compute/math and trigonometric functions with Studio 5000 software. In
addition, the interfacing, parameters configuration, and monitoring are considered for testing. The technique with PLC-based,
devices configuration and experimental results have been presented will be useful for electric power supply in the industry
with more and more demand to apply the PLC system to develop the traditional industry to semi or automatic control in the
industry.
© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
( />Peer-review under responsibility of the scientific committee of the 2021 8th International Conference on Power and Energy Systems Engineering,
CPESE 2021.

Keywords: PLC-based; SCR; AC–DC converter; Trigger; Studio 5000

Nomenclature
PLC
SCR
IEC
PID

Programmable Logic Controller
Silicon Controlled Rectifier
International Electrotechnical Commission
Proportional–Integral–Derivative

1. Introduction
The electrical power supply, SCR power module, power factor control uses PLC act as the main or master
controller. In the industrial automation, the control signal is fed from controller. By the way, the standard signal is
∗ Corresponding author.

E-mail address: (K. Smerpitak).
/>2352-4847/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:
//creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the scientific committee of the 2021 8th International Conference on Power and Energy Systems
Engineering, CPESE 2021.


S. Pongswatd, K. Smerpitak, F. Asadi et al.

Energy Reports 8 (2022) 972–978

linearity with the trigger signal, but the output voltage is not proportional to the signal. In many applications, the

output voltage of thyristor module is applied to many kinds of load such as heating system, oven, electrical drive, so
on. The nonlinearity between trigger signal and SCR output voltage is a factor that impact for tuning the controller
to optimal control. New technology by hardware and software can support the tradition system modify to industrial
automation based on PLC system. The software standard based on IEC 61131-3 improves the design of industrial
control systems using commercial PLCs has been introduced [1]. Real time prototype design and implementation
of automatic control system for electricity power distribution to the load using Programmable Logic Controller has
been proposed [2]. In an industrial automation, PLC controllers have been used in the industry. Many applications
applied PLC based system to implement the industrial process for monitoring, controller tuning, devices diagnostics
have been presented [3–6]. The paper presents the application that apply the arc cosine function, compute/math
function of IEC 61131-3 to program by ladder language. The experiment performs with new engineering program
from Rockwell Automation that is Studio 5000. It is applied with Allen Bradley PLC to solve nonlinearity Vdc
output. In addition, the SCR power regulator is an important power module to convert AC to DC power for dc
drive.
2. Theorem
2.1. AC–DC converter
Topology of the AC–DC power module is shown in Fig. 1. The SCRs S1 and S2 will become forward-biased
when the source becomes positive but will not conduct until gate signals are applied. Similarly, S3 and S4 will
become forward-biased when the source becomes negative but will not conduct until they receive gate signals. The
waveform of load voltage is shown in Fig. 2. Frequency of the load voltage is two times bigger than the source
voltage. Angle α is the angle interval between the forward biasing of the SCR and the gate signal application.

Fig. 1. Topology of the AC–DC converter.

Fig. 2. Waveform of load voltage of AC–DC converter.

The average (dc component) of the waveform shown in Fig. 2 is:
∫
1 π
Vdc =
Vm sin(ωt)d(ωt)

π ∝
Vm
=
(1 + cos α)
π
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(1)


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Energy Reports 8 (2022) 972–978

Graph of 1 + cos α is shown in Fig. 3. As the trigger angle decreases, the average value of output voltage increases.
In addition, the output voltage is nonlinearity with trigger angle. The proposed technique to solve the condition by
generating trigger signal with PLC-Based for linearity output voltage.

Fig. 3. Graph of trigger angle in radian with output voltage.

)
Vm (
1 + cos(cos−1 xout)
π
Vm
=
(1 + xout)
π

Vdc =

(2)

√
In Thailand, the grid voltage is 220 Vrms, so Vm equals to 220 2 ≈ 311 V. The Vdc equation is expressed by
Vm
(1 + xout)
π
311
=
(1 + x)
π
Output voltage of proposed technique is equal to
Vdc =

Vdc = 99 (1 + xout)

(3)

where, xout is the synthesized signal from PLC to trig the SCR’s of AC–DC power module.
2.2. PLC-based system
The proposed system installs Allen-Bradley PLC which consists of CPU module, Digital Input module, Digital
Output module, Analog Input module, and Analog Output module. Hardware specification and catalog number can
be shown by Table 1.
2.3. Compute/math, trigonometric functions [7]
Sequence control and compute/math functions develop with Studio 5000 engineering program that apply
ladder language to execute arccosine function (ACS), subtract (SUB), divide (DIV), multiply (MUL), and so on.
Compute/Math and Trigonometry Function are available depend on controller model and engineering program. ACS
function computes the arc cosine of source and returns the real result. The ACS instruction takes the arc cosine of
the source value and stores the result in the destination (in radians).

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Energy Reports 8 (2022) 972–978

Table 1. I/O modules list and configuration data.
Module No.

Name

Catalog
number

0
1
2
3

CPU & Power Supply
Digital Input (DI)
Digital Output (DO)
Analog Input (AI)

1769-L30ER
1769-IQ16A
1769-OW8/B
1769-IF4B
(4 Ch)

4

Analog Output (AO)

1769-OF4/A
(4 Ch)

Available I/O Signal

Data format

Digital 16 Points
Digital 8 Points
−10. . . 10 Vdc
0. . . 5 Vdc
0. . . 10 Vdc
0. . . 5 Vdc
0. . . 20 mA
4. . . 20 mA
−10. . . 10 Vdc
0. . . 5 Vdc
0. . . 10 Vdc
0. . . 5 Vdc
0. . . 20 mA
4. . . 20 mA

Integer
Short Integer
RAW/Proportional

Engineering Unit
Scaled for PID
Percent Range
RAW/Proportional
Engineering Unit
Scaled for PID
Percent Range

2.4. AI/AO configuration
AI and AO configuration are used to select type and range. This selection lets configure each channel individually
and provides the means of designating signal of the input/output. This work selection configures each AI and AO
channel to accept digital data in percent range format that is shown by Fig. 4.

Fig. 4. Page of AO module properties.

3. Design of PLC-based system
PLC-Based system is designed with Allen-Bradley PLC and Studio 5000 software. The system uses software
language standard based on IEC-61131-3 that is Ladder language. Compute/Math and Arc Cosine function are
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Energy Reports 8 (2022) 972–978

applied to execute trigger signal feed to AO. The proposed technique uses the functions instead scaling function.
In addition, the trigger signal feed to SCR AC–DC power module in order to linearity output voltage.

Fig. 5. Block function to execute trigger signal of proposed and traditional technique.

Main program can be shown block function by Fig. 5. The Compute/Math functions calculate and scale the
value from control function fit to Arc Cosine function. Output value from Arc cosine function in radian is scaled
again then feed to AO module in percentage (0–10,000). AO module converts percentage between 0–10,000 to CV
voltage 0–10 V. Each function can be shown in detail of offline state by Fig. 6.

Fig. 6. Ladder diagram and initial value of offline state.

4. Testing and result
The testing performs by simulation the PV signal feed to AI module then executes the trigger signal with proposed
technique and feed out to AO module. Block diagram for testing can be shown by Fig. 7. Online screen of main
program by Studio 5000 and Allen-Bradley PLC shown by Fig. 8. For testing start by adjusts PV signal from 0–10 V
and feed to AI module. The module converts analog 0–10 V to digital 15 bits then move digital value every scan
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Energy Reports 8 (2022) 972–978

time to control function and DIV of Compute/Math function. The control function is configured in manual mode,
so that the AI value is directly move to DIV. The block function of proposed technique executes and synthesized
signal to trig the SCR’s of AC–DC power module. Synthesized signal is 0–10 V available trigger angle π -0 radian.

Fig. 7. Block diagram for Testing.

Fig. 8. Online screen of main program.

In Thailand, the grid voltage is 220 Vrms. The Vdc outputs of SCR’s of AC–DC power module with trig by
traditional and proposed technique are expressed by Fig. 9. The graph of output voltage shown the Vdc output
versus trigger signal that show linearity of output.

5. Conclusion
In this paper proposed technique to create a trigger signal for SCR AC–DC power converter by using PLCBased system. The system was implemented with Allen-Bradley PLC with Studio 5000 software. In addition, the
arc cosine function and Compute/Math function applied to fit scale the trigger signal. The synthesized trigger signal
in order to trig the SCR AC–DC power converter between π to 0 radian that supply output voltage min to max. The
output voltage linearity with assigned signal agrees well with designed. The technique with PLC-based, AI, AO
configuration and experimental results have been presented will be useful for electric power supply in the industry
with more and more demand to apply the PLC system to develop the traditional industry to semi or automatic
control in the industry.
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Energy Reports 8 (2022) 972–978

Fig. 9. Output value of SCR AC–DC power converter versus trigger signal.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could
have appeared to influence the work reported in this paper.
Acknowledgments
The software licenses and hardware of this work have been supported by Rockwell Automation Thai and Petro
Instrument Co., Ltd., respectively. Moreover, the authors would like to thank staffs of both companies that guideline
the technique for implementation and testing.
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