Power Quality Improvement of a Grid Connected Wind

Energy Conversion System Using PID Controlled STATCOM

Sathish Kumar T

, Sathish Kumar M

, Sarath Kumar D

and Saravanan A

S A Engineering College, Anna University, Avadi-Poonamallee Road, Tamil Nadu, India

Keywords: Wind Energy Conversion System (WECS), Power Quality, STATCOM, Voltage Stability, Harmonics,

Reactive Power.

Abstract: This research focuses on using a PID-controlled static synchronous compensator (STATCOM) to improve the

power quality of grid-connected wind energy conversion systems (WECS). Because wind energy is

intermittent, integrating wind energy systems into the grid frequently results in power quality problems such

reactive power imbalance, voltage fluctuations, and harmonic distortions. With the help of a Proportional-

Integral-Derivative (PID) controller, the STATCOM successfully reduces these power quality problems. The

effectiveness of the suggested strategy in preserving grid stability and guaranteeing adherence to grid codes

is confirmed by simulation results.

1 INTRODUCTION

Power quality issues have grown significantly as a

result of the electrical grid's increasing incorporation

of renewable energy sources like wind. Because wind

is erratic, wind energy conversion systems (WECS)

are by their very nature variable. The overall quality

of the grid's electricity can be adversely affected by

this unpredictability, which can result in reactive

power imbalance, harmonic distortions, and voltage

instability. One popular method for enhancing power

quality in renewable energy systems is the

incorporation of a Static Synchronous Compensator

(STATCOM). In order to lessen power quality

problems, STATCOM offers voltage management

and reactive power support. However, the control

approach used determines how effective it is.

In order to improve dynamic responsiveness and

preserve power quality in the face of fluctuating wind

conditions, this study suggests using a Proportional-

Integral-Derivative (PID) controller for STATCOM

control. The MATLAB/Simulink simulations are

used to assess the suggested system.

https://orcid.org/0000-0002-7324-7106

https://orcid.org/0009-0004-4846-7416

https://orcid.org/0009-0002-1661-1669

https://orcid.org/0009-0007-9804-1183

2 WIND ENERGY CONVERSION

SYSTEM

This section provides an overview of the components

and operation of a typical wind energy conversion

system (WECS). It includes:

• Wind Turbine: Converts wind energy into

mechanical energy.

• Generator

Typically, an induction or

synchronous generator, which converts

mechanical energy into electrical energy.

• Power Electronics Interface: Converts the

generated electricity into a form suitable for

grid connection (DC to AC conversion).

• Grid Connection

Details the interface with

the grid, focusing on the power quality

challenges such as harmonics, voltage sags,

and reactive power management.

T, S. K., M, S. K., D, S. K. and A, S.

Power Quality Improvement of a Grid Connected Wind Energy Conversion System Using PID Controlled STATCOM.

DOI: 10.5220/0013575100004639

In Proceedings of the 2nd International Conference on Intelligent and Sustainable Power and Energy Systems (ISPES 2024), pages 22-28

ISBN: 978-989-758-756-6

3 QUALITY ISSUES IN WIND

POWER SYSTEMS

Because wind is erratic and intermittent, wind energy

systems present serious power quality issues when

they are incorporated into the grid. The main

problems are harmonic distortions brought on by

power electronic converters used in wind turbines and

voltage changes caused by fluctuating wind speeds.

Reactive power imbalance also happens, which

causes voltage instability and power system

inefficiencies. In order to preserve grid dependability,

compensating devices such as STATCOM for voltage

control, harmonic filtering, and reactive power

compensation are required because these power

quality issues can have a detrimental effect on the

grid's stability and performance. This section

highlights the primary power quality issues associated

with grid-connected WECS:

(i) Voltage Fluctuations: Caused by variable wind

speeds.

(ii) Harmonic Distortions: Introduced by power

electronic converters.

(iii) Reactive Power Imbalance: Results in voltage

instability and reduced grid efficiency.

The reactive power QQQ provided or absorbed by the

STATCOM is given by:

Q=Vbus⋅(Vref−Vmeasured)/X

(1)

A discussion on the impact of these issues on grid

stability and the importance of maintaining power

quality standards for grid compliance is included.

4 STATCOM FOR POWER

QUALITY IMPROVEMENT

A Static Synchronous Compensator (STATCOM) is

an advanced power electronics device used to

enhance power quality in grid-connected systems. It

provides reactive power compensation by either

absorbing or injecting reactive power, stabilizing grid

voltage levels under fluctuating load conditions. In

wind energy systems, STATCOM mitigates issues

like voltage fluctuations, harmonic distortions, and

reactive power imbalance caused by variable wind

speeds. With its fast response, STATCOM improves

voltage regulation, reduces total harmonic distortion

(THD), and enhances overall grid stability. When

controlled using strategies like PID control,

STATCOM becomes highly effective in maintaining

consistent power quality in renewable energy

integration.

The Total Harmonic Distortion (THD) is

calculated as:

𝑇𝐻𝐷 =



𝑉





𝑉





...+𝑉





𝑉



× 100%

(2)

Principle of Operation: STATCOM is a shunt

device that injects or absorbs reactive power to

stabilize voltage levels. The benefits of STATCOM:

Fast response, voltage stabilization, harmonic

filtering, and reactive power compensation.

This section explains how STATCOM can

improve the overall stability of the wind energy

system when connected to the grid.

5 DESIGNS OF STATCOM

The PID controller design for STATCOM enhances

its ability to stabilize grid voltage and improve power

quality by precisely regulating reactive power output.

The Proportional (P) component corrects the voltage

error based on the magnitude, the Integral (I)

component addresses accumulated past errors to

eliminate steady-state offset, and the Derivative (D)

component predicts future errors to improve system

stability. Proper tuning of these gains ensures fast

response and minimal overshoot. In wind energy

systems, PID-controlled STATCOM dynamically

adjusts reactive power compensation,

mitigating

voltage fluctuations and harmonics, resulting in

enhanced grid stability and improved power quality

under varying wind conditions.

Figure 1: STATCOM Diagram.

Power Quality Improvement of a Grid Connected Wind Energy Conversion System Using PID Controlled STATCOM

5.1 PID Controller Design for

STATCOM

Output of PID controller, u(t) for regulating reactive

power expressed

𝑢



𝑡



=𝐾







𝑡



+𝐾



 𝑒



𝑡



𝑑𝑡 + 𝐾



𝑑𝑒𝑡

𝑑𝑡

(3)

The design of the PID controller for the STATCOM

is discussed in this section:

5.2 PID Control Mechanism

Overview of how the PID controller adjusts the

reactive power output of the STATCOM to maintain

the desired voltage level and power quality.

5.3 Tuning of PID Parameters

Explanation of the tuning process for the proportional

(P), integral (I), and derivative (D) gains to optimize

system performance.

5.4 Methods for Tuning PID

Controllers:

There are several methods to tune the PID controller,

ranging from manual trial-and-error to more

systematic approaches.

5.4.1 Manual Tuning (Trial and Error)

This method is simple but requires a good

understanding of the system and a lot of

experimentation.

(i) Start with 𝐾



=0 and 𝐾



Increase 𝐾



until the system responds quickly without

excessive oscillation. When the system oscillates or

takes too long to reach the setpoint, reduce 𝐾



Add Integral Action (𝐾



Once the proportional gain is set, add a small amount

of to 𝐾



eliminate steady-state error. Increasing the

value of 𝐾



improves steady-state accuracy but may

induce oscillations if it's too large.

Adjust Derivative Action (Adjust 𝐾



Finally, adjust 𝐾



to reduce oscillations or overshoot.

A small amount of 𝐾



can smooth the response. The

method works for relatively simple systems but may

not give optimal performance in all cases.

5.4.2 Ziegler-Nichols Method

The Ziegler-Nichols method is a popular heuristic

approach based on the system's response to a step

input.

Set 𝐾



=0 and 𝐾



(4)

● Increase 𝐾



until the system oscillates

consistently with a constant amplitude (this is

called the ultimate gain, 𝐾



● Measure the period of oscillation (denoted

𝐾



)

1. Use the following empirical formulas to

calculate the PID parameters:

o For a P controller:

𝐾



=0.5.𝐾



(5)

For a PI controller:

𝐾



=0.45.𝐾



,𝐾



=1.2 .

𝐾



𝑃



(6)

o For a PID controller:

𝐾



=0.6.𝐾



,𝐾



=2.

𝐾



𝑃



.𝐾



=𝐾

 .

𝑃



(7)

Control Objectives:

Ensure voltage stability, minimize

harmonic distortions, and balance reactive power under

varying wind conditions.

6 SYSTEM REQUIREMENTS

Figure 2: Block Diagram.

The block diagram illustrates the interconnected

components essential for enhancing power quality in

renewable energy integration. At the core, the Wind

Energy Conversion System (WECS) consists of a

ISPES 2024 - International Conference on Intelligent and Sustainable Power and Energy Systems

wind turbine that converts kinetic energy from the

wind into mechanical energy, which is then

transformed into electrical energy by a generator,

typically a Doubly-Fed Induction Generator (DFIG)

or Permanent Magnet Synchronous Generator

(PMSG). This output is processed through power

electronics converters to stabilize the voltage and

frequency for grid compatibility. The electrical output

is connected to the utility grid, where it is

continuously monitored for power quality metrics,

such as voltage levels and Total Harmonic Distortion

(THD). The data from the grid is fed into a PID

controller, which adjusts the operation of a Static

Synchronous Compensator (STATCOM) to manage

reactive power. The STATCOM can either inject or

absorb reactive power as needed, ensuring voltage

stability and improving the overall power factor.

Through this feedback loop, the PID controller

optimizes the STATCOM's response to fluctuations

in wind energy generation and grid demand, leading

to improved power quality and a more reliable energy

supply for the grid.

Figure 3: Simulation setup.

The simulation is typically conducted using

MATLAB/Simulink, which provides a robust

platform for modeling dynamic systems in power

electronics and renewable energy applications. The

Wind Energy Conversion System (WECS) is

modeled to include a wind turbine that simulates the

relationship between wind speed and power output,

along with a generator (such as a Doubly-Fed

Induction Generator or Permanent Magnet

Synchronous Generator) that converts mechanical

energy into electrical energy. Power electronic

converters are incorporated to manage the conversion

of the variable output into a stable form suitable for

grid connection.

The grid model reflects the reference voltage and

load dynamics, while the Static Synchronous

Compensator (STATCOM) is modeled to inject or

absorb reactive power as needed. The PID controller

is integrated to regulate the STATCOM's output

based on grid voltage requirements, with tuning

parameters optimized during the simulation for

enhanced performance. Various scenarios are

simulated, such as changing wind speeds and sudden

load

fluctuations, to evaluate the system's response

and resilience to disturbances. Key power quality

indicators, including voltage levels and Total

Harmonic Distortion (THD), are monitored and

analyzed, leading to visualizations that illustrate the

effectiveness of the control strategies. Overall, the

simulation serves as a vital tool for understanding the

interactions within the system and preparing for

successful real-world deployment.

7 SIMULATION MODEL

DIAGRAM

The simulation model is shown in Fig. 4.

Figure 4: Simulation model.

7.1 Wind System

Figure 5: Simulation subsystem model.

7.2 Simulation and Results

The simulation results of the PID-controlled

STATCOM in a grid-connected wind energy

conversion system demonstrate significant

improvements in power quality. Voltage stability is

Power Quality Improvement of a Grid Connected Wind Energy Conversion System Using PID Controlled STATCOM

achieved as the STATCOM effectively compensates

for fluctuations caused by variable wind speeds,

maintaining voltage within desired limits. The

**Total Harmonic Distortion (THD)** is reduced,

ensuring compliance with grid standards. Reactive

power is balanced, minimizing voltage dips and

enhancing system efficiency. Comparative graphs

show the system’s performance with and without

STATCOM, where the PID-controlled STATCOM

leads to faster dynamic response, minimal

oscillations, and better overall power quality,

validating the effectiveness of the proposed control

strategy.

7.3 Voltage Waveforms

Stability: The simulation typically shows improved

voltage stability at the grid connection point. Voltage

waveforms exhibit reduced fluctuations compared to

scenarios without the STATCOM, demonstrating the

compensator’s effectiveness in maintaining voltage

levels. Response to Changes: During sudden changes

in load or wind speed, the voltage waveforms quickly

stabilize due to the reactive power support provided

by the STATCOM, showcasing the system's dynamic

response capabilities.

7.4 Reactive Power Profiles:

Reactive Power Compensation: The STATCOM is

observed to effectively inject or absorb reactive

power as needed, keeping the grid voltage within

acceptable limits. The reactive power profile

indicates the compensator's output in response to

varying load conditions, highlighting its role in

balancing reactive power demand.

Control Performance: The PID controller's ability

to adjust STATCOM output in real-time is evidenced

by smooth transitions in reactive power, leading to

minimal overshoot and oscillations. For reactive

power regulation in a STATCOM, a PID controller is

a common and efficient solution. PID controllers help

keep the power grid's voltage stable by modifying

reactive power injection or absorption in response to

voltage deviation. The stability and best performance

of the system depend on proper simulation and

adjustment.

Figure 6: Simulation output.

7.5 Power Factor Improvement:

Before and After Comparison: The simulation

results typically reveal a significant

improvement in

the power factor of the system. Without the

STATCOM, the power factor may fall below

acceptable levels, indicating poor utilization of

electrical power. With the STATCOM operational,

the power factor approaches unity, suggesting

enhanced efficiency in energy consumption.

Harmonic Distortion Reduction: The implementation

of the STATCOM also contributes to a reduction in

Total Harmonic Distortion (THD) in the current

waveforms, further improving the overall power

quality.

7.6 Harmonic Analysis:

THD Levels: The simulation may show a reduction in

THD levels of the voltage and current waveforms

after incorporating the STATCOM. This reduction

indicates improved harmonic compensation, leading

to cleaner power quality supplied to the grid.

Compliance with Standards: Results often

demonstrate that THD levels meet regulatory

standards, ensuring that the system can operate

reliably within the grid infrastructure.

Figure 7: Simulation output waveform.

ISPES 2024 - International Conference on Intelligent and Sustainable Power and Energy Systems

7.7 Transient Response

Dynamic Behavior: The simulation results provide

insight into the transient response of the system

during disturbances, such as sudden wind speed

variations or load changes. The STATCOM's quick

response time, facilitated by the PID controller, helps

mitigate voltage dips and surges effectively.

Settling Time: The settling time for voltage and

reactive power to stabilize after disturbances is

significantly reduced, showcasing the PID

controller's effectiveness in optimizing system

performance.

Simulation Setup: Description of the wind energy

conversion system model, the STATCOM with PID

controller, and the grid interface.

Performance Evaluation: The key metrics for

evaluating the system’s performance, such as voltage

stability, total harmonic distortion (THD), and

reactive power compensation. For voltage, the usual

Total Harmonic Distortion (THD) level is between

1% and less than 10%. If there are numerous

harmonics present, the THD value for current could

be greater than 100%. Thus, 5% for THD and 3% for

any single harmonic are the voltage harmonic

limitations. It is significant to remember that the

values and recommendations presented in this

standard are entirely optional. However, maintaining

low THD values on a system will also guarantee that

the equipment operates correctly and lasts longer.

Results: Graphical representation of the simulation

results, showing improvements in voltage regulation,

reduction in harmonics, and enhanced reactive power

control.

Table 1: Output Parameters.

Requirement Voltage Current

Inverter 1 311 16

Inverter 2 311 16

Grid 311 36

8 DISCUSSIONS

8.1 Impact of PID Controlled

STATCOM

Discussion on the observed improvements in power

quality, focusing on reduced voltage fluctuations,

better reactive power management, and lower

harmonic distortion.

8.2 Comparison with Other Controllers

Brief comparison with other control strategies (e.g.,

PI control, Fuzzy Logic control) and how the PID

controller provides a better dynamic response and

tuning simplicity.

9 CONCLUSIONS

This paper presents an effective solution for power

quality improvement in grid-connected wind energy

systems using a PID-controlled STATCOM. The

simulation results demonstrate that the proposed

system enhances voltage stability, reduces harmonics,

and improves overall grid compliance under varying

wind conditions. The PID controller offers a simple

yet efficient way to control the STATCOM, making

it suitable for integration into renewable energy

systems.

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