Browsing by Author "Quamruzzaman, Muhammad"

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Analysis and implementation of a look up table based hybrid PWM scheme for voltage source inverters
(Department of Electrical and Electronic Engineering, BUET, 2002-05-07) Quamruzzaman, Muhammad; Mujibur Rahman, Dr. Kazi
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Converter based Frequency Adjustment and Protection of Grid-tied Wind Farm
(EWU, 3-May-2019) Ahmad, Kanij; Mohammad, Nur; Quamruzzaman, Muhammad
Frequency adjustment and protection of a wind
Converter Based Frequency Adjustment and Protection of Grid-tied Wind Farm
(1st International Conference on Advances in Science, Engineering and Robotics Technology 2019, IEEE, 2019-12-19) Ahmad, Kanij; Mohammad, Nur; Quamruzzaman, Muhammad
Frequency adjustment and protection of a wind turbine due to wind gust is a salient aspect of the grid-tied wind farm. Both of them require conserving system stability. This paper presents an investigation of the converter based frequency adjusting method and wind turbine protection. A grid-tied wind power system model using the Doubly Fed Induction Generator in MATLAB is used. To regulate the active power output, synchronization between wind velocity and wind turbine speed is adjusted. Thus, wind farm operated at grid frequency and maximize turbine output. The control strategy of the converter based frequency synchronization of a grid-tied wind farm also includes protection subsystem. The protection system executed by receiving information from the logical block implemented in the wind farm model. It provides wind turbine protection by terminating wind turbine from a grid in abnormal wind conditions. The Simulation result validates the results and control methods.
Development of a high performance PV-Utility interface using phase angle control of PWM inverter
(Department of Electrical and Electronic Engineering (EEE), 2013-12) Quamruzzaman, Muhammad; Mujibur Rahman, Dr. Kazi
The goal of this thesis has been to develop a ‘only phase angle based’ control strategy for single stage grid-connected photovoltaic (GCPV) system. Existing control strategies for single-stage and two-stage GCPV systems are presented. The literature review shows that the control strategies of the GCPV inverters involve adjustment of the phase angle and modulation index of the switching signal which determines the angle and amplitude of the inverter output voltage respectively. The phase angle dominantly controls the real power supplied by the inverter, whereas, the amplitude controls the reactive power. To inject current into the grid at unity power factor, the reactive power injected into grid is reduced to zero by adjusting the modulation index. Due to variation of modulation index, computation increases as the PWM pattern has to be determined each time the modulation index is adjusted. Lower value of modulation index increases harmonics and current THD in the system. To overcome the drawbacks, a single pre-calculated PWM pattern with highest modulation index is used to operate the inverter so as to track maximum power point (MPP) by adjusting the phase angle of the inverter output voltage with respect to the reference grid. The proposed ‘only phase angle based’ control scheme is simulated in matlab and simulink. Maximum power point tracking (MPPT) is performed by adjusting the phase angle of the inverter switching signal and employing common perturb and observe (PO) method. A modification is proposed in PO algorithm for setting a suitable initial phase angle and adaptive step-size to reduce the tracking-oscillations tradeoff problem associated with this popular MPPT technique. Another modified PO method based on gradient ascent technique with variable step-size is also dealt with for setting a range of the permissible step-size. The setting of range of permissible step-size is necessary since unstable condition or inefficient tracking at different irradiance levels may occur due to improper selection of the step-size. Simulation results show that harmonics and current THD are less with the proposed phase angle based control scheme. The validity of the proposed modifications in the PO method is established through investigation by simulation. The proposed scheme is simulated for stiff and weak grids. Weak grid is modeled assuming constant voltage at the high tension (HT) side of the distribution transformer. Grid impedance is considered sufficiently large at the low tension (LT) side. The effect of reactive power injection into grid with the proposed technique is analyzed. It is found that at higher irradiance reactive power supplied by the PV inverter is higher, whereas, it is lower at the point of common coupling (PCC) due to larger amount of reactive power is consumed in filter and coupling inductances at higher irradiance. In case of weak grids, voltage rise due to injection of PV is found to be high which is a desirable feature. The proposed scheme having such feature improves grid voltage profile. The performance of the proposed technique has also been investigated in a three-phase system. The range of phase angle adjustment for a wide range of variation in solar irradiance is investigated. The proposed scheme features stable operation since it avoids the feedback control of current. Along with modeling and analysis, detail simulation results are presented that demonstrates the effectiveness of the proposed technique.
Development of Control Strategy for Load Sharing in Grid-Connected PV Power System
(IEEE, 20-Dec-2008) Quamruzzaman, Muhammad; Rahman, Kazi Mujibur
In a power system of conventional parallel connected generators, share of real power and reactive var of an incoming generator are controlled by adjusting shaft power input and field excitation. The scenario of load sharing by a grid connected PV system is however different since no prime mover or excitation source are present. Due to serious power crisis, there are needs for transfer of PV power to grid systems. However, this needs intensive analysis on the load sharing phenomena. In this paper, aspects of load sharing of a grid connected PV system are analyzed, and a strategy is proposed where the load sharing task can be undertaken controlling both modulation index and phase angle of the inverter. It is seen that both real power and reactive var are affected upon change in index of modulation and phase angle of the PV inverter. Analysis and simulation results are presented to demonstrate effectiveness of the proposed control technique.
Harmonic Mitigation in Transformers of Twelve-Pulse Rectifier Using Active Filter
(IEEE, 20-Dec-2008) Hossain, Mohammad Rubaiyat Tanvir; Quamruzzaman, Muhammad
Researchers proposed several techniques to reduce the harmonics present in the input current of 12 pulse rectifier. But the transformers used in the rectifier contain more low order harmonics in their input currents.
Review on Frequency Adjustment for Power Systems with Grid Connected Wind Farm
(1st International Conference on Robotics, Electrical and Signal Processing Techniques, ICREST 2019, IEEE, 2019-02-21) Ahmad, Kanij; Mohammad, Nur; Quamruzzaman, Muhammad
Continues expanding of wind power harnessing demands an effective control system to improve quality power delivered from wind turbine to grid. A stable power system fully depends on the synchronization that means matching of frequency between the source of power generation and existing power grid. The prime objective of a wind farm controller is to ensure effective operation of the wind farm in any wind speed condition. Frequency deviation between the wind system and grid can challenge the well-built operation of a power system and can imbalance the synchronization between wind farm and grid. The strategy of frequency adjustment is developing time to time which starts from using droop controller based Induction generator to converter based Double-fed Induction generator. This paper summarizes an analytical study on various frequency adjustment mechanisms for a grid-connected wind farm.