Advanced Control Design for Grid-Connected Photovoltaic System and Electric Drives by Kamran Zeb-Department of Electrical and Computer Engineering The Graduate School Pusan National University

 Advanced Control Design for Grid-Connected Photovoltaic System and Electric Drives

 By Kamran Zeb August 2020 Department of Electrical and Computer Engineering The Graduate School Pusan National University 

 Abstract 

The application of Photovoltaic (PV) in the distributed generation system is acquiring more consideration with the developments in power electronics technology and global environmental concerns. Solar PV is playing a key role in consuming the solar energy for the generation of electric power. The use of solar PV is growing exponentially due to its clean, pollution-free, abundant, and inexhaustible nature. In grid-connected PV systems, significant attention is required in the design and operation of the inverter to achieve high efficiency for diverse power structures. The requirements for the grid-connected inverter include; low total harmonic distortion of the currents injected into the grid, maximum power point tracking, high efficiency, and controlled power injected into the grid. The performance of the inverters connected to the grid depends mainly on the control scheme applied. In this thesis, the global status of the PV market, classification of the PV system, configurations of the grid-connected PV inverter, classification of various inverter types, and topologies are discussed, described and presented in a schematic manner. A concise summary of the control methods for single- and three-phase inverters has also been presented. Finally, the criteria for the selection of inverters and the future trends are comprehensively presented. In addition, Grid-Connected PVS required advance DC-link controllers to overcome second harmonic ripple and current controllers to feed-in high-quality current to the grid. This thesis successfully presents the design of a Fuzzy-Logic Based PI (F-PI) and Fuzzy-Logic based Sliding Mode Controller (F-SMC) for the DC-link voltage controller and Proportional Resonant (PR) with Resonant Harmonic Compensator (RHC) as a current controller for a Single-Phase Two-Stages Grid-connected Transformerless (STGT) PV Inverter. The current controller is designed with and without a feedforward PV power loop to improve dynamics and control. A Second Order General Integral (SOGI)-based Phase Lock Loop (PLL) is also designed that has a fast-dynamic response, fast-tracking accuracy, and harmonic immunity. A 3 kW STGT-PV system is used for simulation in Matlab/Simulink. A comparative assessment of designed controllers is carried out with a conventionally well-tuned PI controller. The designed controllers improve the steady-state and dynamic performance of the grid-connected PV system. In addition, the results, performance measure analysis, and harmonics contents authenticate the robustness, fastness, and effectiveness of the designed controllers, related to former works. In this thesis, Smart Grid Initiative of the U.S department of energy based Single Phase Voltage-Source Smart Inverter (SPV-SSI) 5 kVA is designed and analyzed in detail that has the combined capability of supplying power to local load, injecting power into grid, supplying power to the utility load up to rated capacity of the inverter, store energy in lead acid battery bank, the ability to control voltage at the Point of Common Coupling (PCC) during voltage sags/faults, and decision making capability on real time pricing information obtained from the utility grid through advance metering. This thesis also includes complete design of Smart Inverter in dq synchronous reference frame, bidirectional DC-DC Buck-Boost converter, IEEE standard 1547 based islanding and recloser, and STATCOM functionalities. Moreover, optimal and advance controllers i.e. F-PI and F-SMC are designed. The performance of F-PI and Fxvi SMC is superior, stable, and robust in comparison to that of conventionally tuned PI controllers both for voltage control loop (islanded mode) and current control loop (grid connected mode). The simulation results effectively validate the efficacy of the proposed controllers. This thesis also presents modeling and design of a digital PR with RHC to feed-in high quality current. The novelty is on designing the control in a different approach than the conventional methods. As a result, practical engineers find an easy, fast and accurate way to design the control strategy. The proposed system has the capability to inject both active and reactive power in an effective manner. Synchronous reference frame-based phase lock loop that works well under nonideal and distorted grids, is used for synchronization. The platform used for simulation and auto code generation is PSIM 9.1 while code composer studio 6.2.0 is used for debugging. The feasibility and effectiveness of the design controller is also validated using Typhoon (Hardware in Loop) HIL 402 device for real time testing on the DSP board TMS32F28335 from Texas Instruments. The designed controller is tested under various distortion, disturbance, and non-ideal condition. The simulation and HIL results authenticate the robustness, fastness, and efficacy of the designed controller. Recently, the Indirect Field Oriented Control (IFOC) scheme for Induction Motors (IM) has gained wide acceptance in high performance applications. The IFOC has remarkable characteristics of decoupling torque and flux along with an easy hardware implementation. However, the detuning limits the performance of drives due to uncertainties of parameters. Conventionally, the use of a PID controller has been very frequent in variable speed drive applications. However, it does not allow for the operation of an IM in a wide range of speeds. In order to tackle these problems, optimal, robust, and adaptive control algorithms are mostly in use. The work presented in this thesis is based on new optimal, robust, and adaptive control strategies, including an Adaptive PI controller, sliding mode control, Fuzzy Logic (FL) control based on Steepest Descent (SD), Levenberg-Marquardt (LM) algorithms, FL based on Newton Algorithm (NA), FL based on Gauss Newton Algorithm (GNA) and Hybrid Control (HC) or adaptive sliding mode controller to overcome the deficiency of conventional control strategies. In addition, The main theme is to design a robust control scheme having faster dynamic response, reliable operation for parameter uncertainties and speed variation, and maximized torque and efficiency of the IM. The test bench of the IM control has three main parts: IM model, Inverter Model, and control structure. The IM is modelled in synchronous frame using 𝑑𝑞 modelling while the Space Vector Pulse Width Modulation (SVPWM) technique is used for modulation of the inverter. Our proposed controllers are critically analyzed and compared with the PI controller considering different conditions: parameter uncertainties, speed variation, load disturbances, and under electrical faults. In addition, the results validate the effectiveness of the designed controllers and are then related to former works.

LINK:

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