Simulation and Development of Unified Power Flow Controller Using Multilevel Inverter

Heavily loaded transmission lines and the inability to control the amount and direction of power flows have became major concerns to the power utilities. Some of the solutions taken by the power utilities are by expanding the size of power system network in terms of building new transmission lines, using higher rating equipments and installing more generating units. The power utilities also have improved the transmission lines capability and better utilizing of existing power system networks. The power flows in the transmission lines in accordance to their series impedance, voltage magnitude at the sending end and receiving end, and phase angle between these two voltage ends. Electromechanically controlled devices have been used to control the power flow which is now steadily being replaced with static devices. The problem with these electromechanically controlled devices is sometimes they do not react fast enough especially during disturbances. Furthermore, they are subjected to wear and tear which requires regular monitoring and servicing. The advancement in power electronics devices, which provide faster response compared to the electromechanical ones and require less maintenance as they do not wear and tear easily has attracted great interest from the researchers. Among these power electronics devices, Unified Power Flow Controller (UPFC) has gained a lot of attention due to its ability to control, simultaneously or selectively, all the three of power system parameters i.e. line impedance, voltage magnitude and phase angle. In this work, UPFC’s simulation model has been designed and developed as a power system device to investigate the behaviour of the system under normal and abnormal conditions. A small-scale laboratory model has also been constructed to validate the findings obtained from the simulation model. To avoid high frequency components produced in Pulse Width Modulation (PWM), a 3-level Neutral Point Clamped (NPC) multilevel inverter has been proposed as the series inverter for the UPFC using Space Vector Modulation (SVM). The shunt inverter for UPFC is composed of a 6-pulse diode bridge rectifier and a line commutating thyristor bridge. A triggering circuit for the simulation model for the SSSC has been improved for Matlab/Simulink module. For the laboratory model, a switching circuit consists of PIC, optocouplers, IGBTs drivers and monostable multivibrators has been successfully constructed. The proposed 3-level NPC inverter has been shown to have a better feature in terms of Total Harmonics Distortion (THD) with a simulation value of 13.36% VLL and experimental value of 15.65% VLL. The THD value is lower compared to a similar work of 16.46%. The additional voltage phase shift, φ produced by the SSSC has been shown to affect the phase shift between the sending end voltage and receiving end voltage. As the line impedance and both voltages are usually constant, any variation in phase shift between the two voltages will affect the amount of power flows in the transmission lines and its direction. The THDs of the voltage and current of the SSSC when connected between two busbars have been determined and a good agreement between the simulation and laboratory results has been achieved. From the simulation, the THD value of line voltage is approximately 1.3% which is lower compared to other work of 2.49% and 3.58%. A comprehensive controllable UPFC using real power transfer algorithm and reactive power compensation algorithm has been successfully designed and constructed as a simulation model that is able to stabilize voltage with required power for fast changing loads

Optimization of Pole Numbers and Rotor Size for a Single Phase Slot-Less Permanent Magnet Generator.

This paper discussed on the optimization of a permanent magnet generator (PMG). Generally, the PMG is a slot-less type topology, operated in a single-phase, and it was developed to energize the linear motor in pruner application. Due to this application, a compact generator that can produce up to 100W output power is required since the overall size of the PMG is important. Permeance Analysis Method (PAM) is used to analyzed the PMG performance characteristic. Finite Element Method (FEM) and measurement of the PMG prototype were used to verify the PAM result. Various numbers of poles and rotor size were considered during this analysis. The results show that the slot-less PMG with stator size of 104 mm will produce maximum power of 110 W when it has 6-poles with rotor radius is 37 mm. Based on the results, the calculation method using PAM shows good agreement with measurement and FEM simulation

DC-link capacitor voltage regulation with effort-reduction fuzzy logic control for three-level inverter-based shunt active power filter

Shunt active power filter (SAPF) is the most effective solution for current harmonics. In its controller, DC-link capacitor voltage regulation algorithm with either proportional-integral (PI) or fuzzy logic control (FLC) technique has played a significant role in maintaining a constant DC voltage across all the DC-link capacitors. However, PI technique performs poorly with high overshoot and significant time delay under dynamic state conditions, as its parameters are difficult to be tuned without requiring complete knowledge of the designated system. Although FLC technique has been developed to overcome limitations of PI technique, it is mostly developed with high complexity thereby increases computational burden of the designed controller. This paper presents a fuzzy-based DC-link capacitor voltage regulation algorithm with reduced computational efforts to enhance performance of three-phase three-level neutral-point diode clamped (NPC) inverter-based SAPF in overall DC-link voltage regulation. The proposed method is called effort-reduction FLC technique. The proposed algorithm is developed and evaluated in MATLAB-Simulink. Moreover, conventional algorithm with PI technique is tested for comparison purposes. Simulation results have confirmed improvement achieved by the proposed algorithm in comparison to the conventional algorithm

Development of a single-phase PWM AC controller

An AC chopper controller with symmetrical Pulse-Width Modulation (PWM) is proposed to achieve better performance for a single-phase induction motor compared to phase-angle control line-commutated voltage controllers and integral-cycle control of thyristors. Forced commutated device IGBT controlled by a microcontroller was used in the AC chopper which has the advantages of simplicity, ability to control large amounts of power and low waveform distortion. In this paper the simulation and hardware models of a simple single phase IGBT An AC controller has been developed which showed good results

Design and Development of Multilevel Inverter for Convert Direct Current to Alternating Current Using MATLAB Simulation

This paper presented the design and development of a multilevel inverter (MLI). The demand for better electronic devices increases rapidly. The multilevel inverter (MLI) which convert direct current (DC) to alternating current (AC) are widely used in the industry. The objective of this research is to design and simulate the 3-level and 3-level NPC MLI module using PLECS software. To develop the switching technique for each level of NPC MLI, and To analyse and validate the MLI in terms of harmonic. Although there is already an inverter in the market, the researcher still pursues to improve the efficiency, total harmonic distortion (THD), and reduce the size of the MLI. An THD can be improved using the suitable modulation technique and the size of the MLI can be reduced by designing better topologies. The modular NPC is using the three-level NPC as the main module and the number of levels can be increased by adding 2 level NPC modules to the main module. The switching technique was created to control the NPC MLI for each level

Transmission lines modelling based on RLC passive and active filter design

This paper presents a transmission line (TL) modelling which is based upon vector fitting algorithm and RLC passive filter design. Frequency Response Analysis (FRA) is utilised for behaviour prediction and fault diagnosis. The utilities of the measured FRA data points need to be enhanced with suitable modelling category to facilitate the modelling and analysis process. This research proposes a new method for modelling the transmission line based on a rational approximation function which can be extracted through the Vector Fitting (VF) method, based on the frequency response measured data points. A set of steps needs to be implemented to achieve this by setting up an extracted partial fraction approximation, which results from a least square RMS error via VF. Active and passive filter design circuits are used to construct the model of the Transmission line. The RLC design representation was implemented for modelling the system physically while MATLAB Simulink was used to verify the results

Simulation and construction of single phase flying capacitor multilevel inverter

This paper focuses on the simulation and construction of single phase, three level Flying Capacitor Multilevel Inverter (FCMI). For FCMI, there is several switching state for one DC level of the inverter, so the selection of switching state combination is important so that every IGBTs can be switched on equally. The design of the FCMI was successful done on the MATLAB/simulink simulation software including the triggering circuit. The small scale laboratory model of FCMI was also successfully constructed. A good agreement between simulation and hardware results has been obtained

Effects of high power converter on power line carrier signal

Power line carrier (PLC) systems are used in transmission of signals for teleprotection, teletripping, telecontrol and speech communication. The signal to noise ratio (SNR) of the PLC is based on the noise level at the input of the carrier's receiver. The interference due to large power converter will be superimposed on the background noise at lower level. It has reduced the SNR to an unacceptable value. This paper deals with analysis of high frequency (HF) harmonics (higher than 20 kHz) produced from the converters, and the methods used to reduce the noise imposed on the PLC communication signal. The experimental and simulation results have been obtained for both processes

Realization of single phase to three phase matrix converter using SVPWM algorithm

The direct AC to AC conversion techniques adopted in the implementation of the single phase to three phase converters do not yield the best output results due to the complexity of the segregation process and bidirectional nature of the input signal. Number of initiatives has been reported adopting a mid DC Link path for creating more appropriate results. However, none of them provides convincing results in producing the standard three phase output signals that are equal in magnitude and 120 degrees away from each other. This paper reports a novel attempt in implementing the space vector pulse width modulation based Matrix Converter system for direct single phase to three phase conversion using IGBT based bi-directional switches that produce convincing three phase output signals from a single phase voltage source

Analysis of AC - to - DC uncontrolled converters harmonics for electric vehicles applications

This paper discusses the harmonic analysis of the AC-to-DC uncontrolled converters commonly used in electric vehicles charging station. The aim of this paper is to model and simulate different rectifier models in addition to explaining the differences in input current harmonics, the total Harmonic Distortion (THD) as well as the power factor (pf). The converter configurations include single-phase bridge, 6-pulse and 12-pulse rectifier circuits. The single phase is normally used for electric scooter charging, while three-phase converters can be used for both electric bus and car charging. The circuit configurations of the rectifiers were modelled and simulated using Matlab R2014a to achieve the objective of the study. The results revealed that the THD levels were extremely high which is unacceptable if the system is connected to the utility grid