Application of Unified Power Flow Controller to Improve the Performance of Wind Energy Conversion System

This research introduces the unified power flow controller (UPFC) as a means to improve the overall performance of wind energy conversion system (WECS) through the development of an appropriate control algorithm. Also, application of the proposed UPFC control algorithm has been extended in this research to overcome some problems associated with the internal faults associated with WECS- voltage source converter (VSC), such as miss-fire, fire-through and dc-link faults

Performance up gradation of static VAR compensator with thyristor binary switched capacitor and reactor using model reference adaptive controller

There are various static var compensator configurations are available and listed in the literature. Their performances are evaluated based on their voltage support, dynamic response, losses, cost, and additional filter requirement, if any. In this paper, efforts are made to improve the dynamic performance parameter such as rise time, settling time, and peak overshoots. A new topology with an adaptive controller is presented, in which capacitor and reactor banks are divided in their binary values and connected in the shunt. Capacitor and reactor banks are operated by thyristorised switches. Both these banks are operated in closed-loop form as a cascade control. Amongst these, capacitor bank operates as coarse control, and reactor bank acts as fine control. For the performance enhancement, a model reference adaptive controller is used. The system identification toolbox is used to evaluate the mathematical model of the plant with Matlab. The model\u27s performance was analyzed deeply by the adaptive controller with different reference models such as critical, under, and overdamped. The performance parameters such as rise time, settling time, and peak overshoot in the form of reactive power swings, are evaluated and plotted for different adaptive gains using MIT rules

Novel adaptive stability enhancement strategy for power systems based on deep reinforcement learning

As the access rate of wind energy in a power system has significantly increased, stabilizing the power system has become challenging. Among these challenges, low-frequency oscillation is one of the most harmful problems, effectively resolved by adding a damping controller according to the relevant properties of the low-frequency oscillation. However, the controller often fails to adapt to the constantly changing wind energy system owing to the lack of a targeted dynamic change strategy. Thus, to address this issue, an adaptive stabilization strategy that uses a static var compensator with an additional damping controller structure is proposed. Specifically, the entire power system is equivalently represented as a generalized regression neural network, with a deep reinforcement learning algorithm called soft actor-critic introduced to train the agent based on the generalized regression neural network model. After the training process, the agent can provide additional efficient static var compensator damping controller parameters under different operating conditions, vastly improving the system stability. Simulation results verify the improved performance using the proposed strategy compared to other optimization methods, regardless of whether the low-frequency oscillations were suppressed in the time or frequency domains

A New Converter Station Topology to Improve the Overall Performance of a Doubly Fed Induction Generator-Based Wind Energy Conversion System

This thesis presents a reliable and cost effective technique that calls for reconfiguration of the existing converters of a typical Doubly Fed Induction Generator to include a coil of low internal resistance. A coil within the DC link is the only hardware component required to implement this technique. With a proper control scheme, activated during fault conditions, this coil can provide the same degree of performance as a superconducting magnetic energy storage unit during fault conditions

STATCOM and SVC with Wind Turbines

The large wind parks are the feasible solution in order to generate clean energy compared with conventional power plants. Therefore, the interest in the Wind Energy Conversion System (WECS) is quickly increasing to reduce the fossil fuels dependencies. While the penetration of the WECS increases into the grid, many of the technical challenges have appeared. Low voltage Ride Through (LVRT) is the new requirement which needs to be fulfill when the amount of wind power generation increases, to be able to guarantee the power system reliability and stability. The voltage dips that result from faults in the grid can lead to a loss generation unit. According to the LVRT, WTs are required to be always connect during the fault, and to support the power system by supplying reactive power to ensure grid stability. The main purpose of the thesis was to investigate that how the LVRT of Doubly Fed Induction Generator (DFIG) based Wind Turbine Generator (WTG) can be enhanced using shunt connected Flexible AC Transmission System (FACTS) devices Static Synchronous Compensator (STATCOM) and Static Var Compensator (SVC). The theoretical background related to the LVRT enhancement using STATCOM and SVC is performed, and results are verified by the simulation model. This thesis is constructed in 5 Chapters, Chapter 1 gives an overview about the problems related to wind power. Chapter 2 explains the different grid codes and different topologies of the wind turbine technologies. Chapter 3 explains the working principle, construction and applications of the STATCOM and SVC. A comprehensive comparison between the STATCOM and SVC is also explained in this chapter. The operation of DFIG wind turbine during voltage dip is analyzed by using the simulation model in the next Chapter. In the first case, the effect of a three-phase fault on the power system was analyzed without using any compensation device. The LVRT requirements were not fulfilled without any compensation device. Therefore, in the second case, SVC was added in the model. Some improvement was observed in this case, but it was not enough to fulfill very strict LVRT requirements such as German Grid Codes (GGCs).Therefore, in the third case, SVC is replaced by STATCOM to meet the LVRT requirement of GGCs. In the last case, three different ratings of STATCOM were utilized to see the effect on the grid voltage and reactive power support by STATCOMs. The key findings of this thesis work are reported by Chapter 5

Static reactive power compensator design, based on three-phase voltage converter

At present, electrical network stability is of the utmost importance because of the increase in electric demand and the integration of distributed generation deriving from renewable energy. In this paper, we proposed a static reactive power compensator model with common direct current voltage sources. Converter parameters were calculated and designed to fulfill specifications. In order to ascertain the device response for different operating modes as reactive power consumer and generator, we developed the model’s power and control circuits in Matlab Simulink. Simulations were performed for different conditions, and as a result, the current and voltage waveforms and the circular power chart were obtained. This paper has theoretically proven it is possible to achieve the consumption or generation of purely active or reactive power by implementing a static reactive power compensator with common DC voltage sources. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Role of FACTS devices in enhancing integration of renewable energy sources to the grid: a review

2018 Conference paper. Theme (Renewable Energy and Energy Efficiency)The modern power system is facing challenges such as exponential growth in demand, constrained infrastructure and deregulation of electricity markets. For a sustainable energy system, it is necessary to meet energy need by utilizing renewable energy sources (RES), which have minimum environmental impact. Over the last two decades, renewable energy generation and integration into the grid has received a lot of attention worldwide. In 2017 alone, more than half of all new electricity capacity installed globally was from RES. However, RES such as solar photovoltaic and wind energy are intermittent in nature. Integrating variable generating sources into the grid can cause problems such as voltage fluctuations and interruptions, which affect the performance of utility equipment as well as end user. Over the years, flexible AC transmission system (FACTS) device utilization in power systems has been on the rise. FACTS refer to the application of power semi-conductor devices to control electrical variables, thus influencing power flow and enhancing power system security. This paper investigates the role of FACTS devices in expediting renewable energy integration in power systems. Challenges associated with renewable energy injection into the grid, and how FACTS devices can mitigate these issues is presented. We conclude that the penetration rate of renewable energy will be accelerated if FACTS devices are incorporated in RES integration projects.Jomo Kenyatta University of Science and Technology, Kiambu, Keny