Modeling, Integration and Simulation of the Photovoltaic Power Plant

Considering LVRT Capability and Transient Voltage Stability

ABDELAZIZ SALAH SAIDI1,2(Member, IEEE), OSAMA ALI ZEMI3, LINA ALHMOUD4,

and MUHAMMAD UMAR MALIK5

1Electrical Engineering Department, King Khalid University, Abha 61421, KINGDOM OF SAUDI ARABIA

2Laboratoire des Systèmes Electriques, Ecole Nationale d’Ingénieurs de Tunis,

Université de Tunis El Manar, TUNISIA

3National Grid company, Project Management Office, Central Operation Area, KINGDOM OF SAUDI ARABIA

4Electrical Power Engineering Department, Hijjawi Faculty for Engineering Technology, Yarmouk University, Irbid 21163, JORDAN

5Grid Studies Department, National Grid Company, KINGDOM OF SAUDI ARABIA

Abstract: - This paper investigates how high photovoltaic energy penetration impacts dynamic performance and

voltage regulation of the modified IEEE-9 bus grid. The transmission power system was modeled and simulated

using PSCAD-EMTDC software to conduct the study. Load flow analysis is implemented to explore the power

system’s capability to incorporate the desired photovoltaic power. Moreover, the study is based on time response

simulations to grid disturbances. The supply and control of reactive power from solar power generation plants are

becoming critical issues to study because they can facilitate the integration of PV in power grids under different

operating conditions. Network-related faults like a PV solar power plant event outage, a three-phase short-circuit

at a conventional bus, and a voltage dip at the PV solar power plant have been considered. The results will

help identify the protective devices and strategies needed to maintain the stability and reliability of the system

operation and transient analysis of the network under external power network fault and recovery operation. Thus,

it has practical significance for real utility studies. Moreover, this comprehensive study will be a valuable guide

for assessing and improving the grid’s performance under the study of any other grids, which also gives the vast

potential and need for solar energy penetration into the grid systems.

Key-Words: - Photovoltaic power plant, PSCAD, Static load, Modeling, Transient voltage stability, LVRT

capability.

Received: November 23, 2022. Revised: November 24, 2023. Accepted: December 27, 2023. Published: December 31, 2023.

1 Introduction

Voltage stability is the ability of the system to pre-

serve acceptable voltages at all buses in the system

under normal conditions, especially after being ex-

posed to a disturbance. Apower system is said to have

gotten into a state of voltage instability when a distur-

bance results in a progressive and uncontrollable very

low voltage. The power system may undergo voltage

collapse if the post-disturbance equilibrium voltages

near loads are below acceptable limits. Voltage col-

lapse is a process that leads to a decline in voltage pro-

file, causing voltage instability in a significant part of

the system. Voltage stability is sometimes called load

stability [1]. The present transmission systems are in-

creasingly stressed due to economic and environmen-

tal constraints. Voltage stability problems usually oc-

cur in heavily stressed systems. Thus, voltage secu-

rity means the ability of a system not only to operate

stable but also to remain stable following a contin-

gency or load increase. Voltage stability can be classi-

fied based on time frame: short-term voltage stability

and long-term voltage stability; and the type of dis-

turbance: small disturbance voltage stability and sig-

nificant disturbance voltage stability [2]. Short-term

voltage stability typically lasts for a few seconds. The

analysis requires a solution of appropriate differential

equations. It involves dynamics of fast-acting com-

ponents such as automatic voltage regulator (AVR),

turbine, and governor dynamics. Long-term voltage

stability is mainly due to the considerable distance

between the generator and the load. It involves the

dynamics of slow-acting equipment such as a tap-

changing transformer. The time frame is within a few

minutes to tens of minutes. This type of voltage insta-

bility may be prevented by load shedding and reactive

power compensation [3].

Large disturbance voltage stability measures the

system’s ability to control voltage at all buses follow-

ing significant disturbances such as generation loss,

load loss, and systems faults. This stability can be de-

termined by assessing the system’s dynamic perfor-

mance over sufficient time to capture device interac-

tions such as generator field current limiter and un-

load tap changing transformers. Meanwhile, in small-

distance voltage stability, following any minor distur-

bances at any given operating state, the voltage close

to the load remains fixed or near the pre-disturbance

values [4]. The load flow study is the first step in

analyzing the power system from the capacity stand-

point to investigate generation sources, transformers,

and cables that match the intended loads. In addi-

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Abdelaziz Salah Saidi, Osama Ali Zemi,

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tion, a load flow study points out locations in the

system where low-voltage or high-voltage conditions

may exist. The first step in a load flow study is to

create an accurate system model in a line diagram.

Computer programs like PSCAD can run simulations

on that power system to evaluate what-if scenarios for

load changes in contingent situations [5]. The itera-

tive process of a load flow simulation starts by us-

ing the load as a known quantity. Still, since current

flow is likely based on voltage and the voltage at a

particular node varies based on current flow, the pro-

gram needs to make an educated guess as to the total

power flowing from the source. Then, calculations

are performed until the mismatch of the estimation is

very close to the actual load specified. The load flow

simulation solves losses and voltage profiles [5], and

bold changes along the way are plotted on a single-

line diagram. Scenarios are created to determine if

new equipment is needed or if transformer tabs need

to be adjusted to compensate for the additional load.

The benefit of this study is that if the network size

is increased or new renewable generation sources are

added, starting from the base case model of the sys-

tem, Many alternative scenarios can be run until the

results are comfortable. At the end of this process, the

operator knows precisely the required changes needed

to optimize power flow and cost. Ways can be shown

to reduce energy bills or how to add more load to

the existing system for capacity reasons, voltage drop

consideration, or loss calculations to enhance tran-

sient voltage stability profile while improving voltage

levels throughout the system [6].

Power system stability and control are not con-

sidered new concerns. However, grid operators are

now paying extra attention to keeping the transmis-

sion systems stable to prevent the recurrence of large

blackouts that have affected many countries. Thus,

the power system network is under typical operating

conditions, and after being perturbed, it should be sus-

tained, stable, reliable, and secure, and the bus volt-

ages should be within limits. There are several ways

to approach voltage stability study [6]. However, it

can be helpful for operators to estimate the power

system’s closeness to voltage collapse before imple-

menting corrective measures and taking premedical

actions. Voltage stability analysis is still frequently

used in industries to calculate the P-V and Q-V curves

at specific load buses [7]. Numerous load flows often

produce these curves utilizing traditional techniques

and models. However, these techniques take a lot of

time and don’t offer enough valuable information to

address the stability issues. In [8], several reasons

electricity systems go through interruptions are listed.

Meanwhile, power system outages can be prevented

in several cases with sufficient system protection and

adequate awareness. Suppose the power system is

not equipped with suitable protection for the system

[9]. In that case, the power system is prone to unex-

pected factors such as external disturbances, compo-

nent failures, and parameter changes [9]. Hence, volt-

age instability is one of the problems causing power

interruptions and voltage collapse. The power sys-

tem utilized in this paper is the IEEE 9-bus test case.

The IEEE 9-bus test case represents a portion of the

Western System Coordinating Council (WSCC) [2],

[10]. Many researchers have studied it and a PV solar

power plant connected to bus 6. Integration of PV so-

lar power plants poses significant challenges. Thus, it

limits reactive power capability and causes a signifi-

cant voltage drop or rise in the system [11], [12].

The work assesses transient voltage stability in a

modified IEEE 9-bus in the presence of a photovoltaic

(PV) solar power plant and a three-phase short cir-

cuit at the most loaded bus in the system. The system

was modeled in PSCAD; a simulation study was per-

formed to investigate potential transient voltage sta-

bility based on the voltage profiles, active and reac-

tive power profiles, and system stability. The system

under different operating conditions is simulated and

analyzed. It aims to classify stability issues likely to

occur in the grid by identifying different scenarios to

enhance the industry’s understanding of the interac-

tion of PV solar power plants with other assets in the

system. In this work, the IEEE 9-bus is used to cre-

ate an equivalent standard test in PSCAD. The power

flow data system is available in [2]. After success-

fully validating the power flow, many scenarios are

simulated. (i) the pre-disturbance steady state is ob-

tained, (ii) a PV solar power plant is integrated into the

system at bus 8, and the dynamic performance is reg-

istered, (iii) the impact of a three-phase short circuit

takes place at the most loaded bus 8 while a sudden

disconnection of the PV solar power plant is simulated

and discussed. (iv) The impact of a three-phase short

circuit occurs at the most loaded bus 8 while recon-

nection of the PV solar power plant is analyzed.

The paper is organized such that Section 2 presents

the implementation of a PV solar power plant in

PSCAD. Section 3 describes the proposed system un-

derstudy of IEEE 9-bus before and after modifica-

tions. Section 4 presents the results of four scenarios:

base case, modified case with PV solar power plant,

modified case with PV solar power plant connected at

bus 6, and three-phase short circuit at bus 8 which is

the most loaded bus. Finally, the case after the sudden

disconnecting of the PV solar power plant in the pres-

ence of a fault of a three-phase short circuit. Section

5 presents the conclusion and future work.

2 PV plant model and control

PSCAD (Power Systems Computer Aided Design)

is a commercial international software for analyzing

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Abdelaziz Salah Saidi, Osama Ali Zemi,

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Figure 1: Grid-connected PV plant model using PSCAD software [13].

and simulating power and electrical systems. It was

officially developed by the engineering department

within Manitoba Hydro International Ltd. (MHI)

in 1983 in Canada. It is a comprehensive build-

ing, modeling, and simulating electromagnetic tran-

sient (EMT) studies. It includes an extensive li-

brary of power and energy models, including pas-

sive elements, control functions, and electrical ma-

chines. The integrated calculations and analysis soft-

ware, power flow calculation, short circuit calcula-

tion, motor starting, and transient stability. Models

include power system studies, HVDC and FACTS, re-

newable energy integration, electromagnetic transient

studies, and power equipment services. Thus, it intro-

duces a comprehensive and robust solution from sim-

ulation to real-time operational control for power gen-

eration, transmission systems, distribution, and uti-

lization. The functional expressions in each mod-

ule are very intuitive and easy to understand. Each

part’s simulation modules’ simulation results can also

be given as a report [13], [14].

Integrating PV solar power plants in PSCAD is

available under different operating conditions. There

are two switches, one to control the irradiation and the

other to control the temperature. The PV solar power

plant model mainly consists of arrays and converters

as shown in Figure 1. The PV Array is a PSCAD mod-

ule used to model the behavior of a solar photovoltaic

(PV) array. It typically contains a group of solar PV

panels connected in series and parallel to generate the

system’s required DC voltage and current. The main

function of the PV Array during the simulation of a

PV solar power plant is to model the behavior of the

solar PV array and its interaction with the other com-

ponents in the system, such as the boost converter,

voltage source converter, and LCL filter. Precisely,

the PV Array Box in PSCAD can model the behavior

of the solar PV array by generating DC power based

on the input irradiance and temperature values. The

DC power output is then sent to the boost converter

for voltage regulation. In addition, it can monitor the

DC voltage and current of the solar PV array to ensure

that they remain within the system’s operating range.

The PV Array Box can model the behavior of the indi-

vidual PV panels in the array by considering their tem-

perature coefficient, shading effects, and other factors

that affect their performance. The PV Array Box can

implement MPPT algorithms to optimize the power

output of the solar PV array by adjusting the input

voltage and current to ensure that the PV panels oper-

ate at their maximum power point [15], [16].

The specific settings and parameters of the voltage

source converter (VSC) in PSCAD may vary depend-

ing on the characteristics of the solar PV system and

the power grid. Therefore, it is essential to carefully

analyze the behavior of the solar PV system and adjust

the VSC settings accordingly to ensure proper perfor-

mance during the simulation. The boost converter is

a DC-DC converter commonly used in solar PV sys-

tems to step up the DC voltage produced by the PV

panels to a suitable level for the voltage source con-

verter (VSC) [17]. The main function of the boost

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converter during the simulation of a PV solar power

plant is to regulate the DC voltage to ensure that it

remains within the range required by the VSC. The

boost converter does this by adjusting the switch’s

duty cycle to control the current flow through an in-

ductor and a capacitor. The boost converter can also

provide other essential functions, such as maximum

power point tracking (MPPT), to optimize the power

output of the PV solar power plant by adjusting the

input voltage and current to ensure that the PV panels

operate at their maximum power point. Besides, the

boost converter can limit the input current to the VSC

or inverter to ensure that it remains within the rated

capacity of the device and does not cause overloading

or damage [18]. Also, the boost converter can detect

and protect against faults, such as overvoltage, under-

voltage, overcurrent, and short-circuit conditions, to

ensure that the PV solar power plant operates safely

and reliably. Besides, the VSC can adjust the phase

angle between the current and voltage waveforms to

improve the system’s power factor, reducing losses

and improving the system’s efficiency. Also, the VSC

can detect when the power grid is disconnected or ex-

periences a fault and automatically switch to islanding

mode to ensure that the PV solar power plant contin-

ues supplying power to critical loads. The VSC can

suppress the high-frequency harmonics generated to

ensure that the AC power injected into the grid meets

the relevant power quality standards [19].

3 System Under Study

The IEEE 9-bus system is a standard test case used

in power system analysis and research [1]. It consists

of nine buses, three generators, three loads, and trans-

mission lines and transformers, as shown in Figure 2.

Table 1,Table 2, and Table 3 summarize the per uni-

tized terminal conditions of each source, the transmis-

sion lines parameters, and PQ load model with 100

MVA, respectively. The base voltage levels are 16.5

kV, 13.8 kV, 18 kV, and 230 kV. The complex power

for each line is around hundreds of MVA each. The

generators are connected to Bus 1, Bus 2, and Bus 3.

Meanwhile, the loads at Bus 5, Bus 6, and Bus 8. This

system has a few voltage control devices. Thus, it is

easy to control. The purpose of the IEEE 9-bus sys-

tem is to provide a standard reference for researchers

to test and compare new power system analysis tech-

niques, such as load flow, transient stability, and fault

analysis. The system is also used for teaching pur-

poses in power system courses. Researchers use IEEE

9 bus systems to implement new ideas and concepts.

Indeed, the test was developed by the Western Sys-

tem Coordinating Council (WSCC). In transient sta-

bility studies, it is vital to have the pre-fault voltage

magnitude and phase angle at each bus and active and

reactive power on generation and transmission buses.

Table 1: Conditions of the IEEE 9-bus system.

Bus V (kV) δoActive power (pu) Reactive power (pu)

1 17.160 0.0 0.7163 0.2791

2 18.45 9.3507 1.63 0.049

3 14.145 5.142 0.85 -0.1145

Table 2: Transmission line characteristics of IEEE 9-

bus system.

From line To line R (pu/m) X (pu/m) B (pu/m)

4 5 0.0100 0.0680 0.1760

4 6 0.0170 0.0920 0.1580

5 7 0.0320 0.1610 0.3060

6 9 0.0390 0.1738 0.3580

7 8 0.0085 0.0576 0.1490

8 9 0.0119 0.1008 0.2090

Table 3: Load characteristics of IEEE 9-bus system.

Bus Active power (pu) Reactive power (pu)

5 1.25 0.50

6 0.90 0.30

8 1.00 0.35

A 25 MW PV system testbed is adopted to ob-

serve the LVRT dynamics. This model was developed

and posted by PSCAD [13]. The system topology is

shown in Figure 2. The solar farm consists of 100

PV arrays. Each unit generates a maximum power of

0.25 MW at the nominal irradiation of 1000W/m2

and nominal temperature of 28o. The MPPT, de-

tailed DC/DC boost converter, and detailed three-

phase switches are included, shown in Figure 1. The

system parameters are given in Table 4. The base volt-

age on the DC side is 1 kV. The DC voltage is con-

verted to 0.55 kV AC voltage through GSC.

4 Simulation results and discussions

4.1 Steady state voltage stability

In load flow analysis, PV solar power plants are usu-

ally integrated into the generator-type PV bus because

of their voltage control capability and due to the ac-

tive power generation [20]. On the other hand, they

are considered load buses after achieving their reac-

tive generation limits. Each PV solar power plant

has been characterized in the power system based on

the above hypothesis. The PV solar power plant is

synchronized with a grid by having inverters. They

do not provide voltage and frequency as a reference

by themselves when connected to the electrical in-

stallation. They measure the voltage and frequency

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Figure 2: IEEE 9- bus test systems [10].

Table 4: 25 MW PV solar power plant PSCAD testbed

parameters.

Description Parameters Value

Switching frequency 3 kHz (VSC) 5 kHz (DC-DC)

Power base Sb25 MW

Inverter power base S0

b250 kW

Inverter dc voltage base VDC,b 1 kV

PCC voltage base VP CC,b 0.55 kV

POC voltage base VP OC,b 33 kV

Power level PP OC,b 1 pu

System frequency fb60 Hz

LCL filter Lf ilter,Cfilter 0.32 mH, 54.80

Damper Ldamp,Cdamp,Rdamp 1.60 mH, 27.40

F, 7.65 Ω

Shunt capacitor BC10.2 pu

DC-link capacitor Cdc 10000

PV LC filter LP V ,CP V 2.5 mH, 100

Transformer impedance XT10.05 pu

Transmission line Xg,Rg0.45 pu, 0.05 pu

Current control loop Kpi,Kii (0.2, 20) pu

DC-link control loop Kpp,Kip (1,20) pu

VAC Control loop Kpv,Kiv (1,10) pu

PLL Kp,P LL,Ki,P LL (500,200) pu

at their connection point and deliver a power output

synchronized with this voltage and frequency of the

grid. Here, the inverters should be designed to have

no mismatches or instability in the electrical installa-

tion. In this work, the system voltage profile for peak

load conditions has been tested with and without con-

nection to a PV solar power plant. The characteristic

of the voltage profile at all IEEE 9-bus systems with

and without PV solar power plants are shown in Ta-

ble 5 and Figure 3. The bus voltage ranged from 0.995

to 1.028 pu at zero PV solar power plant connection

case. The voltage magnitude profile was improved

by integrating the PV solar power plant and injecting

the maximum power point tracking. It was observed

that the voltage magnitude was increased, but no over-

voltage was observed after integration for all busbars.

Remarkably, the grid voltage profile increased from

1.005 pu to 1.045 pu. In most of the buses in the sys-

tem, the voltage profile is within the 5% tolerance.

The terminal voltage phase angle at each connection

bus is measured in degrees for the system without and

with a PV solar power plant and presented in Table 5.

It can be perceived that the voltage angles of neigh-

boring buses are nearly identical, as demonstrated by

numerous references [6].

The base case results of load flow analysis of static

stability are given in Table 5 and Table 6, respectively.

The results show that MVAR losses are higher than

the MW losses. This is because the reactance val-

ues are greater than the resistive values, as shown in

Table 2. In the transmission lines, the active power

can transfer between the sending end and the receiv-

ing end in the transmission lines. The overloads on

highly loaded feeders and capacity release on these

feeders and substations are alleviated through the sig-

nificant penetration of PV solar power plants. There

is a minimization of total distribution power losses.

When connecting solar PV solar power plants, the

power losses moderately decrease compared with the

normal system power losses; thus, power losses ver-

sus the penetration rate of the solar PV system.

Figure 4, Figure 5, Figure 6, Figure 7, Figure 8,

Figure 9, Figure 10, Figure 11, Figure 12, and Fig-

ure 13 show the steady state analysis (base case) for

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Table 5: The busbar voltage (pu) for the IEEE 9-bus

system with & without PV power plant connected.

Bus Bus voltage(pu) Bus angle (o) Bus voltage (pu) Bus angle (o)

Bus 1 (swing) 1.036 4.1 1.045 5.1

Bus PV - - 1.032 -

Bus 2 1.02 8.5 1.032 11.0

Bus 3 1.02 4.9 1.029 6.3

Bus 4 1.021 -3.3 1.005 0.12

Bus 5 0.995 -5.0 1.012 -2.0

Bus 6 1.007 4.98 1.035 -0.12

Bus 7 1.022 -1.0 1.024 2.5

Bus 8 1.012 0.9 1.038 3.2

Bus 9 1.028 2.2 1.045 4.97

Table 6: The base case of load flow analysis for IEEE

9-bus system via. losses in transmission lines with &

without PV solar power plant connected.

From To Without PV With PV

Bus Bus Losses (MW) Losses (MVAR) Losses (MW) Losses (MVAR)

Bus 4 Bus 5 0.33 -15.94 0.3 -16.23

Bus 4 Bus 6 0.16 -15.458 0.09 -16.064

Bus 5 Bus 7 -2.19 0.643 1.98 5.382

Bus 7 Bus 8 0.51 -11.06 0.46 -12.6851

Bus 8 Bus 9 -0.08 21.148 -0.10 21.5601

Bus 9 Bus 6 1.52 4.4 1.14 -6.41

0.2

0.4

0.6

0.8

1.2

Bus 1 Bus

Bus 2 Bus 3 Bus 4 Bus 5 Bus 6 Bus 7 Bus 8 Bus 9

Without PV 1.036 0 1.02 1.02 1.021 0.995 1.007 1.002 1.012 1.028

With PV 1.045 1.032 1.032 1.029 1.005 1.012 1.035 1.024 1.038 1.045

Bus voltage (pu)

Bus No.

Figure 3: Bus bar voltage for the system under study

with & without PV solar power plant.

the system under study. Figure 4 shows the active

power generation at bus, Figure 5 shows the active

power generation at bus 2 & bus 3. Figure 6 shows the

reactive power generation at bus 1, Figure 7 shows the

reactive power generation at bus 2 & bus 3, Figure 8

shows the bus voltage at all buses, Figure 9 shows the

active power at load bus 5 & bus 8, Figure 10 shows

the active power at load bus 6, Figure 11 shows the

reactive power at load buses 5 & bus 8, Figure 12

shows the reactive power at load bus 6, Figure 13

shows the bus angle at all buses. The dynamic volt-

age stability of the studied power system was exam-

ined by assessing the behavior of the voltage at the

buses during the normal conditions. The simulation

results show that the solutions of the dynamic power

system model converge to the equilibrium character-

ized by the nominal voltage as well as active and re-

active power generation and consumed. The results

indicate also that the system is stable with respect to

the same voltage, reactive and active power solved by

the load flow analysis in the previous section.

Figure 4: Active power generation at bus 1- base case

(MW).

Figure 5: Active power generation at bus 2 & bus 3-

base case (MW).

Figure 6: Reactive power generation at bus 1- base

case (MVAR).

4.2 Dynamic performance

4.2.1 PV power plant disconnection

A base case scenario of PV solar power plants con-

nected to bus 6 in the IEEE 9-bus system is analyzed

as shown in Figure 14. Here, the initial conditions

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Abdelaziz Salah Saidi, Osama Ali Zemi,

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Volume 18, 2023

Figure 7: Reactive power generation at bus 2 & bus

3- base case (MVAR).

Figure 8: Bus voltage (pu) at all buses- base case

(MW).

Figure 9: Active power at load bus 5 & bus 8 base

case (MW).

Figure 10: Active power at load bus 6- base case

(MW).

have been set for 100% power output of the PV nom-

inal power at standard test condition (STC) at 25◦C

cell temperature, 1000W/m2solar radiation, and air

mass of 1.5. Figure 15, Figure 16, Figure 17, Fig-

ure 18, Figure 19, Figure 20, Figure 21, Figure 22,

Figure 23, and Figure 24 show the dynamic perfor-

Figure 11: Reactive power at load buses 5 & bus 8-

base case (MVAR).

Figure 12: Reactive power at load bus 6- base case

(MW).

Figure 13: Bus angle at all buses-base case.

mance analysis for the system under study with the

PV solar power plant connected to bus 6. During

this base case scenario, the voltage response at all

buses converges to the equilibrium nominal per-unit

values with and without a PV solar power plant con-

nection. Figure 15 and Figure 16 show the reactive

power generation at the synchronous generator power

plant swing bus 1 and the solar PV generator bus 2

equals 60 MW and 30 MW, respectively. Figure 17

and Figure 18 show the reactive power generation at

the synchronous generator power plant swing bus 1

and the solar PV generator bus 2, respectively. Fig-

ure 19 shows the bus voltage at all buses, Figure 20

shows the active power at load bus 5 & bus 8, Fig-

ure 21 shows the active power at load bus 6, Figure 22

shows the reactive power at light load buses 5 & bus

8, Figure 23 the reactive power at buses 6, Figure 24

shows the bus angle at all buses. Thus, there is a slight

improvement in the voltage profile in the PV solar

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Figure 14: IEEE 9-Bus test systems with PV solar power plant penetration.

power plant integration as seen in Figure 19. There-

fore, the system is in a state of stability, and all system

variables do not exceed the permissible limits. It can

be observed in Figure 15 that after the PV solar power

plant is connected online to the system, the active and

reactive power is no longer provided by the swing bus

only. Both the swing bus and the PV solar power plant

bus are contributed as shown in Figures 16 and Fig-

ure 18, respectively. It can be observed that PV so-

lar power plants supply the most active and reactive

power generation. Thus, the swing bus, bus 2, and

bus 3 decreased their power capabilities, and the PV

solar power plant helps the grid with power support

and voltage regulation to the overall system.

Figure 15: Active power generation at bus 1 (MW)

with PV solar power plant connected.

4.2.2 System short-circuit

The third scenario investigates the transient responses

of the sudden loss of the PV solar power plant con-

nected to bus 6, and a symmetrical three-phase fault

Figure 16: Active power generation at bus 2 & bus 3

(MW) with PV solar power plant connected.

Figure 17: Reactive power generation at bus 1 (MW)

with PV solar power plant connected.

was injected into the most loaded bus 8. The fault was

initiated at 3 s and cleared at 3.2 s, as shown in Fig-

ure 25 and Figure 26. It created a severe drop in the

active power synchronous generating system at the

swing bus 1, bus 2, and bus 3, respectively. After 10

s, the generation stations reached 78 MW, 1.7 MW,

and 0.9 MW, respectively. Figure 27 and Figure 28

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DOI: 10.37394/232016.2023.18.35

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Figure 18: Reactive power generation at bus 2 & bus

3 (MVAR) with PV solar power plant connected.

Figure 19: Voltage al all buses (pu) with PV solar

power plant connected.

Figure 20: Active power at light load buses 5 & bus

8 (MW) with PV solar power plant connected.

Figure 21: Active power at load bus 6- base case

(MW) with PV solar power plant connected.

illustrate the variation in reactive power generation.

The transient peaks of 100 MVAR, 1 MVAR, and 0.5

MVAR were detected at the swing bus and generator

buses 2 and 3. Later, the transitory was wiped off in

a short period. It was also observed that the active

power generation decreased, with the reactive power

Figure 22: Reactive power at light load buses 5 & bus

8 (MVAR) with PV solar power plant connected.

Figure 23: Reactive power at buses 6 (MVAR) with

PV solar power plant connected.

Figure 24: Buses angle with PV solar power plant

connected.

generation at buses 1, 2, and 3 reaching a transitory

peak of 4.12 pu. The voltage profile of the system’s

different buses is presented in Figure 29. A significant

voltage drop was observed at bus 8 and bus 7, where

the fault was injected. A declined voltage value of

0 p.u. was noted at the most loaded bus 8. Thus, an

overall voltage drop to 0.4 in the grid is recorded. The

changes in the real and reactive power values of load

buses 5 & 8 were recorded and shown in Figures 30

and Figure 31, where the real power can be seen to

have significantly dropped to 10 MW, 0.0 MW, and

0.1 MW, respectively. A severe oscillation in the re-

active power demand at bus 8, as shown in Figure 32,

reached 35 MVAR and damped within 1.2 sec. Reac-

tive power at buses 6 (MVAR) with 3-φSC at bas 8

and without PV solar power plant connected as shown

in Figure 33.

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Abdelaziz Salah Saidi, Osama Ali Zemi,

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Figure 25: Active power at bus 1 (MW) with 3-φSC

at bas 8 and without PV solar power plant connected.

Figure 26: Active power at bus 2 & bus 3 (MW) with

3-φSC at bas 8 and without PV solar power plant con-

nected.

Figure 27: Reactive power at bus 1 (MVAR) with 3-φ

SC at bas 8 and without PV solar power plant con-

nected.

Figure 28: Reactive power at bus 2 & bus 3 with 3-φ

SC at bas 8 and without PV solar power plant con-

nected.

4.2.3 Voltage dip faults at PV solar power plant

In this scenario, a three-phase short circuit was ap-

plied at t= 20 s and cleared in 120 ms. Figure 34

Figure 29: Voltage at all buses (pu) with 3-φSC at

bas 8 and without PV solar power plant connected.

Figure 30: Active power at load bus 5 & bus 8 (MW)

with 3-φSC at bas 8 and without PV solar power plant

connected.

Figure 31: Active power at load bus 6- base case

(MW) with 3-φSC at bas 8 and without PV solar

power plant connected.

Figure 32: Reactive power at light load buses 5 & bus

8 (MVAR) with 3-φSC at bas 8 and without PV solar

power plant connected.

shows the PV solar power plant bus voltage behav-

ior for all the terminal bus locations during the fault-

ride-through. Instantly after the occurrence of a fault,

WSEAS TRANSACTIONS on POWER SYSTEMS

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Abdelaziz Salah Saidi, Osama Ali Zemi,

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Volume 18, 2023

Figure 33: Reactive power at buses 6 (MVAR) with

3-φSC at bas 8 and without PV solar power plant con-

nected.

Figure 34: Voltage at all buses (pu) with 3-φSC at

bas 8 and without PV solar power plant connected.

the voltage at the PV bus drops from 1.0 p.u and at

buses 5 and 8, respectively, to 0.2 p.u and 0.0 p.u ac-

cording to the geographical distance of the respective

PV farm. During the fault rides through, this voltage

starts rising towards their rated values with an over-

shot in voltage at some buses: 5 and 8. These over-

shoots are because of the low capacity of those buses.

Immediately after the fault is cleared at 5.120 s, as the

PV farm begins a voltage regulation mode, the voltage

at the PV terminal starts to reach its rated values. As

demonstrated in Figures 35 and Figure 36, the active

power generation at the PV solar power plant, swing

bus 1, and generator buses 2 and 3 has experienced

a dip reaching down to 0.2 pu due to a three-phase

fault occurring at bus 8. Since a fast has protracted the

PV bus, continuously acting controller by the schema

of regulation. Thus, the voltage regulation at the PV

bus is guaranteed. Figure 37 and Figure 38 depict a

PV solar power plant bus’s reactive power production

pattern to provide voltage backing during the fault pe-

riod. It is observed that the PV bus has contributed

the most in supporting the system voltage regulation

because the PV bus is the geographically nearest gen-

erating bus to the faulted bus 8. The results also show

that the system is stable. Also, the power system has

a good transient performance with rapid recovery of

terminal voltage and reactive and active power during

and after the fault clearance.

Figure 39 shows the bus voltage at all buses, Fig-

ure 40 shows the active power at load bus 5 & bus 8,

Figure 35: Active power at bus 1 (MW) with 3-φSC

at bas 8 and PV solar power plant connected.

Figure 36: Active power at bus 2 & bus 3 (MW) with

3-φSC at bas 8 and PV solar power plant connected.

Figure 37: Reactive power at bus 1 (MVAR) with 3-φ

SC at bas 8 and PV solar power plant connected.

Figure 38: Reactive power at bus 2 & bus 3 with 3-φ

SC at bas 8 and PV solar power plant connected.

Figure 41 shows the active power at load bus 6, Fig-

ure 42 shows the reactive power at light load buses

5 & bus 8, Figure 43 the reactive power at buses 6,

Figure 44 shows the bus angle at all buses.

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2023.18.35

Abdelaziz Salah Saidi, Osama Ali Zemi,

Lina Alhmoud, Muhammad Umar Malik

E-ISSN: 2224-350X

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Volume 18, 2023

Figure 39: Voltage at all buses (pu) with 3-φSC at

bas 8 and PV solar power plant connected.

Figure 40: Active power at load bus 5 & bus 8 (MW)

with 3-φSC at bas 8 and PV solar power plant con-

nected.

Figure 41: Active power at load bus 6- base case

(MW) with 3-φSC at bas 8 and PV solar power plant

connected.

Figure 42: Reactive power at light load buses 5 & bus

8 (MVAR) with 3-φSC at bas 8 and PV solar power

plant connected.

5 Conclusion

This paper helped to create a test beds for transient

stability study. The uniqueness of the proposed test

Figure 43: Reactive power at buses 6 (MVAR) with

3-φSC at bas 8 and without PV solar power plant con-

nected.

Figure 44: Voltage at all buses (pu) with 3-φSC at

bas 8 and PV solar power plant connected.

bed helped to validate the modeling of the IEEE 9-bus

and the performance of a PV solar power plant for a

variety of applications and validate the dynamic per-

formance of the system. It demonstrated how the pro-

posed test bed can be beneficial in investigating the

impact of integrating the PV solar power plant. These

scenarios helped in understanding the issues related to

the increase of penetration of PV solar power plants

to maximize electrical energy capacity, especially in

weak systems, and increase the security and reliability

of the grid as the PV solar system penetration grows.

Thus, investigation of voltage stability demonstrates

that the dynamic comportment of the voltage depends

strangely on the short circuit capability of the trans-

mission system at the bus of integration with the PV

station. The dynamic performance of the grid has pre-

sented compliance with voltage ride-through capabil-

ities that can be improved using a supplementary re-

active supply. The extra generation of PV power has

been found to considerably improve the voltage reg-

ulation, even in the case of over-voltages. Due to the

additional reactive power absorption capacity offered

by solar generators, a significant improvement in the

system voltage regulation capability has been found.

Due to the importance of the reactive power value ob-

tained at the common coupling point with the grid, the

reactive power contributions of SPV are taken into ac-

count. Abrupt disconnection of PV farms results in a

voltage drop of 6% of the nominal voltage. Bus 8 has

been mostly affected by this disruption, for which a

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2023.18.35

Abdelaziz Salah Saidi, Osama Ali Zemi,

Lina Alhmoud, Muhammad Umar Malik

E-ISSN: 2224-350X

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Volume 18, 2023

secondary frequency regulation action is necessary.

Further research may be carried out to address

the following issues, such as developing detailed

inverter-based solar models and controls to study and

improve stability issues under fault conditions. Be-

sides, additional variations of the load model could

be considered. In particular, the mechanical torque

of the induction motor load can be modified to, e.g.,

quadratic or a combination of different torque charac-

teristics to form composite mechanical loads, which

would affect short-term voltage stability. The addi-

tional operating points in the test system should be

considered, e.g., PV systems that do not operate at

unity power factor. Moreover, higher PV penetra-

tion levels are also of interest. Moreover, the stud-

ied contingencies could be varied in terms of fault lo-

cation, fault impedance, fault type, or fault duration

to affect different PV systems, induction motors, and

synchronous generators in the test system. In contin-

uation to the presented study, an extension has been

intended to investigate the effects of different FACTS

devices and the effect of environment temperature and

irradiance on the dynamic voltage stability of the grid.

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Abdelaziz Salah Saidi, Osama Ali Zemi,

Lina Alhmoud, Muhammad Umar Malik

E-ISSN: 2224-350X

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Volume 18, 2023

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

Abdelaziz Salah Saidi: Formal analysis, In-

vestigation, Methodology, Software, Super-

vision, Visualization, Writing – original draft.

Osama Ali Zemi: Formal analysis, Investigation,

Methodology, Software, Supervision, Validation.

Lina Alhmoud: Methodology, Project ad-

ministration, Supervision, Validation, Vi-

sualization, Writing – review & editing.

Muhammad Umar Malik: Data cura-

tion, Formal analysis, Methodology,

Resources, Software, Supervision.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

Report potential sources of funding if there is any

No funding was received for conducting this study.

No Conflicts of Interest

The authors have no conflicts of interest to

declare that are relevant to the content of this

article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International , CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2023.18.35

Abdelaziz Salah Saidi, Osama Ali Zemi,

Lina Alhmoud, Muhammad Umar Malik

E-ISSN: 2224-350X

353

Volume 18, 2023