Dual mode control of inverter to integrate solar-wind hybrid fed DC-grid with distributed AC grid

Abstract: This paper presents integration of solar-wind hybrid fed DC-grid to distributed AC grid. Generally, the renewable hybrid energy systems use two or more energy sources to supply power to the dc grid. In case of insufficient power generation or excessive load demand, in order to supply power to DC loads, it must integrate with AC grid. As dc loads increase in number, complexity increases and tighter voltage regulation is required. This paper presents dual mode control operation of inverter which integrates the solar and wind power fed dc bus to the single phase ac distribution system. The inverter can be operated in hysteresis current control when power is fed from DC grid to AC distributed grid and in AC-DC boost rectifier mode otherwise. The detailed operation of dual mode control of inverter is described in this paper. The effectiveness of the proposed system has been verified through simulation studies using MATLAB/SIMULINK

Boost Interleaved Converter Integrated Voltage Multiplier Module for Renewable Energy System

This document presents a high step-up converter, which is apt for renewable energy system. Through a voltage multiplier unit composed of switched capacitors and coupled inductors, a conventional interleaved boost converter obtains high step-up gain without operating at extreme duty ratio. The design of the proposed converter not only reduces the current stress but also constrains the input current ripple, which decreases the conduction losses and lengthens the lifetime of the input source. In addition, due to the lossless passive clamp performance, leakage energy is recycled to the output terminal. Hence, large voltage spikes across the main switches are alleviated, and the efficiency is improved. Even the low voltage stress makes the low-voltage-rated MOSFETs be adopted for reductions of conduction losses and cost. Finally, the prototype circuit with 40-V input voltage, 380-V output, and 1000-W output power is operated to verify its performance. The highest efficiency is 97.1%. Index Terms - Voltage multiplier module. Boost–flyback converter, high step-up, photovoltaic (PV) system

On the Analysis and Design of Disturbance Rejecter

In this thesis, the impact of the disturbance rejecter concept and the enforced plant has been explored. In order for the active disturbance rejection controller (ADRC) to provide a reasonable alternative to the industry standard PID controller, it is necessary to develop tuning procedures capable of providing adequate performance with reasonable stability margins. A focus should be placed upon the disturbance rejecter, as it is the heart and soul of ADRC. In this thesis, transfer function analysis of the enforced plant has been performed to connect ADRC with the tools from classical control. The relationship between the gain parameter and observer bandwidth is studied to understand why higher bandwidths are attainable with smaller gains. A root locus technique demonstrates how the enforced plant poles change with observer bandwidth. The Nyquist stability criterion is used to offer tuning methods that satisfy gain and phase margins and ensures a transient that satisfies a given damping requirement. A technique is offered to display the infinite radius encirclements of the Nyquist plot within a finite graph. Analysis is performed on why the controlled response is typically slower than desired and how to correct i

On the Analysis and Design of Disturbance Rejecter

In this thesis, the impact of the disturbance rejecter concept and the enforced plant has been explored. In order for the active disturbance rejection controller (ADRC) to provide a reasonable alternative to the industry standard PID controller, it is necessary to develop tuning procedures capable of providing adequate performance with reasonable stability margins. A focus should be placed upon the disturbance rejecter, as it is the heart and soul of ADRC. In this thesis, transfer function analysis of the enforced plant has been performed to connect ADRC with the tools from classical control. The relationship between the gain parameter and observer bandwidth is studied to understand why higher bandwidths are attainable with smaller gains. A root locus technique demonstrates how the enforced plant poles change with observer bandwidth. The Nyquist stability criterion is used to offer tuning methods that satisfy gain and phase margins and ensures a transient that satisfies a given damping requirement. A technique is offered to display the infinite radius encirclements of the Nyquist plot within a finite graph. Analysis is performed on why the controlled response is typically slower than desired and how to correct i

On the Analysis and Design of Disturbance Rejecter

In this thesis, the impact of the disturbance rejecter concept and the enforced plant has been explored. In order for the active disturbance rejection controller (ADRC) to provide a reasonable alternative to the industry standard PID controller, it is necessary to develop tuning procedures capable of providing adequate performance with reasonable stability margins. A focus should be placed upon the disturbance rejecter, as it is the heart and soul of ADRC. In this thesis, transfer function analysis of the enforced plant has been performed to connect ADRC with the tools from classical control. The relationship between the gain parameter and observer bandwidth is studied to understand why higher bandwidths are attainable with smaller gains. A root locus technique demonstrates how the enforced plant poles change with observer bandwidth. The Nyquist stability criterion is used to offer tuning methods that satisfy gain and phase margins and ensures a transient that satisfies a given damping requirement. A technique is offered to display the infinite radius encirclements of the Nyquist plot within a finite graph. Analysis is performed on why the controlled response is typically slower than desired and how to correct i

Model predictive control: an effective control approach for high performance induction machine drives

Induction machine drives with various configurations are getting a lot of attention in several industrial applications. Due to this increasing demand in industrial applications, the significance of developing effective control approaches for obtaining a high dynamic performance from the induction machine drives became essential. Up to the present time, the control of induction machine drives using power converters has been based on the principle of mean value, using pulse width modulation with linear controllers in a cascaded structure. Recent research works have demonstrated that it is possible to use Predictive Control to control induction machine drives with the use of power converters, without using modulators and linear controllers. This new approach will have a strong impact on control in power electronics in coming decades. The advantages of Predictive Control are noticed through the ability to consider a multi-objective case within the model, easy inclusion of non-linearities within the model, simple treatment of system constraints, easy of digital implementation, and flexibility of including modifications and extension of control horizons according to the required applications. Upon this, the research presented in this thesis concerns with developing different control topologies for various configurations of induction machine drives based on finite control set model predictive control (FCS-MPC) principle, which actuates directly the switch states of the voltage source inverter (VSI). In addition, for enhancing the robustness of the induction machine drives, different sensorless approaches are utilized and tested for validations. The first topology of induction machine drives that has been studied is the induction motor (IM) drive. An effective model predictive direct torque control (MP DTC) approach is used to control the torque and stator flux of the motor through the utilization of an effective cost function, through which the understanding and comparing implementation variants and studying convergence and stability issues can be easily investigated. The speed sample effect on the control variants and overall performance of the proposed MP DTC is analyzed, which enables the understanding of the real base principle of DTC, as well as why and when it works well. Two different sensorless procedures for estimating the speed and rotor position are used by the proposed MP DTC approach; the first utilizes a model reference adaptive system (MRAS) observer, while the other exploits the prediction step during the implementation of proposed MP DTC to get the speed information through performing a linear extrapolation of the speed values starting from the last two estimated samples. Extensive simulation and experimental tests have been carried out to validate the effectiveness of both sensorless approaches in achieving precise tracking of speed commands for a wide range of variations. For enhancing the robustness of proposed MP DTC, the stator flux as a control variable is replaced with controlling the flow of the reactive power through the induction motor drive. As the reactive power is a measured quantity compared with the estimated value of stator flux, thus, the sensitivity of the control against parameters variation is limited, and this confirmed through the obtained results from both simulation and experimental tests. In addition, an effective alternative approach to the MP DTC is presented, which based on controlling the instantaneous values of the active and reactive powers of the IM drive based on model predictive principle, instead of controlling the torque and flux as in MP DTC. This technique has the advantage that all controlled variables are became measured quantities (active and reactive powers), thus the estimation problems that commonly present in classic DTC schemes are effectively limited. For the last two control approaches (MP DTC reactive power control, and MP IPCactive and reactive power control), the sensorless that utilizes the predictive feature is also adopted. Obtained results via simulation and experiments confirm the feasibility of the two alternatives control procedures in obtaining a robust dynamic response of IM drive. To limit the accompanied ripple contents in the controlled values of electromagnetic torque and stator flux of induction motor, an effective ripple reduction technique has been presented. The technique is based on the derivation of the optimal value for the weighting factor (w_f) used in the cost function. A detailed mathematical derivation of the optimal value of w_f is introduced based on the analysis of torque and flux ripples behaviors. The proposed ripple reduction technique has been validated via simulation utilizing Matlab/Simulink software, and experimentally tested using a fast control prototyping dSpace 1104 board. In addition, the prediction step based sensorless approach is adopted during implementation. The performance of the IM drive using the proposed approach is compared with the results obtained from MP DTC approach that uses an arbitrary value of w_f. The comparison confirms the validity of the proposed ripple reduction procedure in reducing the ripple contents in the controlled variables while preserving the permissible computation burdens during the implementation. The FCS-MPC principle is also utilized to control the current of induction motor as an alternative to classic field oriented control (FOC), the proposed model predictive current control (MPCC) approach belongs to the class of the hysteresis predictive control (for limiting the switching frequency) as the MPCC is triggered by the exceeding of the error of a given threshold. In addition, a sensorless drive is achieved by including an effective Luenberger observer (LO) for precise estimation of rotor flux vector together with stator current, speed and load torque. The stator currents are estimated to eliminate the accompanied noise in their values when they are directly measured, thus the currents noise during prediction is limited. An effective pole placement procedure for the selection of observer gains has been adopted. The procedure is based on shifting the poles of the observer to the left of the motor poles in the complex (s-plane) with low imaginary part, so that the stability of the observer is enhanced for wide speed range. The feasibility of the sensorless MPCC for IM drive is confirmed through the obtained simulation and experimental results. The second topology of induction machine drives that has been studied is the doubly fed induction motor (DFIM) drive. An effective model predictive direct torque control (MP DTC) algorithm is developed for controlling the torque and rotor flux of DFIM drive. In addition, an effective sensorless approach is presented, which estimates the speed and rotor position in an explicit way without the need for involving the flux in the estimation process, thus the effect of parameters variation on the overall performance of the sensorless observer is effectively limited, this has been approved through the obtained results that are performed for a wide speed range from sub-synchronous to super-synchronous speed operation. During the operation, the stator resistance and magnetizing inductance values are changed from their original values to study the variation effect on the observer performance. Matlab/Simulink software and a prototyping dSpace 1104 control board are used to validate the effectiveness of proposed sensorless MP DTC approach through simulation and experiments, respectively. The results proof the robustness of the proposed sensorless approach and its ability to achieve precise estimation of the speed and rotor position. The third topology of induction machine drives that has been studied is the doubly fed induction generator (DFIG). A detailed analytical derivation for the proposed model predictive direct power control (MP DPC) approach for DFIG is presented, which as a sequence considered as a transposed control approach from the MP DTC used before for doubly fed induction motor (DFIM). A sensorless approach based on model reference adaptive system (MRAS) observer is adopted for estimating the speed and rotor position. Both simulation using Matlab/Simulink software and experimental test using a prototyping dSpace 1104 control board have tested the dynamic performance of the drive. Obtained results affirm the feasibility of the proposed MP DPC approach in achieving a decoupled control of active and reactive powers for DFIG. In summary, it can be said that the proposed model predictive control approaches have proved their ability in achieving high dynamic performance for different topologies of induction machine drives. In addition, the proposed sensorless techniques have confirmed their effectiveness for a wide range of speed variations. All of this are approved and validated through extensive simulation and experimental tests