Pengaturan Konverter DC-DC Bidirectional Dengan MPPT Berbasis Modified Perturbation And Observation Pada Sistem Turbin Angin

Sistem turbin angin sangat dipengaruhi oleh kondisi angin yang fluktuatif, sehingga menyebabkan daya keluaran pada sistem turbin angin pun juga mengalami fluktuasi dan daya pada DC Bus tidak akan konstan. Oleh karena itu, pada sistem turbin angin membutuhkan baterai sebagai penyimpan energi. Ketika daya keluaran pada sistem turbin angin dengan generator PMSG melebihi kebutuhan daya beban maka daya akan disimpan ke dalam baterai (mode pengisian). Begitu juga sebaliknya, ketika daya yang dibangkitkan sistem turbin angin-PMSG tidak mampu memenuhi kebutuhan beban maka baterai akan membantu menyuplai daya yang dibutuhkan (mode pengosongan). Operasi pengisian dan pengosongan baterai diatur dengan menggunakan konverter bidirectional. Konverter DC-DC bidirectional dapat bekerja dalam dua mode, yaitu mode pengisian baterai (mode buck) dan mode pengosongan baterai (mode boost). Metode pencarian daya maksimal dengan menggunakan metode berbasis Modified Perturbation and Observation (P&O) juga digunakan untuk mengatur pensaklaran pada konverter boost sehingga didapatkan Maximum Power Point (MPP) dari sistem turbin angin. Hasil dari penelitian ini mampu mempercepat kondisi tunak pencarian daya maksimal jika dibandingkan dengan metode P&O konvensional. Serta konverter bidirectional mampu mengatur proses pengisian dan pengosongan baterai dengan baik. ============================================================ Wind turbine system is influenced by wind conditions changing, causing the output power at the wind turbine system also fluctuated and power on the DC bus will not be constant. Therefore, the wind turbine system on a stand-alone condition requires a battery as energy storage. When the output power of Permanent Magnet Synchronous Generator (PMSG) on wind turbine system is greater than the required power load, it will be stored in the battery (charging mode). Likewise, when the power generated PMSG not able to serve the power requirements of the load, the battery will also supply the required power (discharge mode). Battery charge and discharge operation is set by using a converter. Bidirectional DC-DC converter can work in two modes, namely battery charging mode (buck mode) and a battery discharge mode (boost mode). Maximum power tracking method based on Modified Perturbation and Observation (P&O) is also used to set the switching boost converter to obtain the Maximum Power Point (MPP) of a wind turbine system. The results of this study could accelerate the steady conditions in the maximum power tracking compared to the conventional P&O method and bidirectional converter is able to regulate the process of charging and discharging the battery properly

Controlled Power Point Tracking for Grid Connected and Autonomous Operation of PMSG based Wind Energy Conversion System

With continuous depletion of conventional sources of energy, Wind Energy Conversion Systems (WECS) are turning out to be one of the major players with immense potential to meet the future energy demands. It is one of the most preferable source, as it can be installed onshore as well as offshore. But with the increasing penetration of wind energy into power system, wind energy conversion systems (WECSs) should be able to control the power flow for limited as well as maximum power point tracking. Apart from tracking desired power, there are some other issues which needs to be addressed for stable and reliable operation of WECS in grid connected as well as islanded mode. In the grid connected mode synchronization of the system to the grid and maintenance of dc-link voltage in absence of ESS are the main control requirements apart from controlled power extraction from the wind turbine. Unlike the grid connected mode, where most of the system level dynamics are imposed by the grid and hence load voltage magnitude an frequency are dictated by the grid itself, in the autonomous operation of WECS the load voltage magnitude and frequency control comes in as additional control requirements other than controlled power extraction from Wind Turbine. However the usage of batteries in the system is unavoidable due to stability and reliability issues. In contrast to the traditional pitch angle control, this work focusses on field oriented speed control of permanent magnet synchronous generator (PMSG) for controlling the active power flow based on the wind turbine characteristics. A back to back AC/DC/AC topology is implemented for interfacing the WECS to the distribution network with various power electronic interfaces providing the necessary control over the power flow. By maintaining the dclink voltage constant and by deploying PLL, power balance and grid v synchronization are attained respectively in grid connected operation of WECS. For the standalone operation of WECS, however the ideology for controlled power extraction from WECS remains same but the load voltage magnitude and frequency control are attained by carrying out the analysis and design exercise in synchronously rotating reference frame so that linear control techniques can be employed easily and sinusoidal command following problem gets transformed to an equivalent dc command tracking thus yielding desired performance with zero steady state error. The motive behind using batteries in the system is to facilitate transient stability and enhance reliability. Proper decoupling and feed forward techniques have been deployed to eliminate crosscoupling and mitigate the effect of load side disturbances. Simulations are carried out under varying load demand as well as changing weather conditions to demonstrate the applicability and effectiveness of the proposed control strategies for grid connected as well as standalone WECSs. Overall, the project work involves study, design, modelling and simulation of grid connected as well as standalone Wind Energy Conversion System

Control of a permanent magnet synchronous general-based wind energy conversion system.

Master of Science in Electrical Engineering. University of KwaZulu-Natal, Durban 2016.Wind energy has proven to be a competitive and an environmentally friendly renewable energy resource for generating electricity. Wind farms are usually located far from the load centers; hence the generated power has to be transmitted over long distances to load centers. High voltage direct current (HVDC) transmission system is the preferred means for transmitting bulk power over long distances when compared to high voltage alternating current (HVAC) transmission system. An HVDC transmission system increases the transmission capacity, improves the system stability, and possesses lower transmission losses. In this research investigation, a 690V, 2MW wind turbine-driven permanent magnet synchronous generator is modelled to be integrated into a local 33kV AC grid via a three- level neutral-point-clamped voltage source converter (VSC)-based HVDC transmission system. Three control schemes were implemented, namely: pitch-angle controller, generator-side converter controller, and a grid-side converter controller to optimize the system performance. The stability analysis and controller modeling was carried out in MATLAB using bode plots and step response curves. The proposed subsystems and the control schemes were implemented in PSIM software package to evaluate the overall system's performance. The simulations were carried out on the model and it was concluded that the grid-side converter controller ensured maximum power point tracking when the wind speed was lower than the wind turbine(WT)'s rated wind speed. Conversely, as the wind speed exceeded the WT's rated wind speed, the pitch-angle controller was activated. This increased the angle of attack thereby reducing the power coefficient in order to shed off the aerodynamic power. Furthermore, the DC-link voltage was stabilized within the allowable limits to ensure a continuous flow of active power from the WT to the grid and the reactive power transfer between the grid-side converter and the AC utility grid was maintained to a minimum to ensure a unity power factor. The comparison analysis of the new control approach to the traditional control approach illustrated that for the new control approach, the ability of the DC-link voltage controller to keep the DC-link voltage within the allowable limits does not get impaired during fault conditions. Therefore, the power continues flowing from the WT generator to the grid. Conversely, it was observed that for the traditional control approach, the ability of the DC-link voltage controller to stabilize the DC-link voltage gets impaired and therefore it can no longer effectively transfer as much active power from the WT generator to the grid. Therefore, the new control approach proved to be effective in terms of stabilizing the DC-link voltage during fault conditions thereby enhancing the WT’s fault-ride-through capability

Intelligent voltage dip mitigation in power networks with distributed generation

Includes bibliographical references.The need for ensuring good power quality (PQ) cannot be over-emphasized in electrical power system operation and management. PQ problem is associated with any electrical distribution and utilization system that experiences any voltage, current or frequency deviation from normal operation. In the current power and energy scenario, voltage-related PQ disturbances like voltage dips are a fact which cannot be eliminated from electrical power systems since electrical faults, and disturbances are stochastic in nature. Voltage dip tends to lead to malfunction or shut down of costly and mandatory equipment and appliances in consumers’ systems causing significant financial losses for domestic, commercial and industrial consumers. It accounts for the disruption of both the performance and operation of sensitive electrical and electronic equipment, which reduces the efficiency and the productivity of power utilities and consumers across the globe. Voltage dips are usually experienced as a result of short duration reduction in the r.m.s. (r.m.s.- root mean square) value of the declared or nominal voltage at the power frequency and is usually followed by recovery of the voltage dip after few seconds. The IEEE recommended practice for monitoring electric power quality (IEEE Std. 1159-2009, revised version of June 2009), provides definitions to label an r.m.s. voltage disturbance based upon its duration and voltage magnitude. These disturbances can be classified into transient events such as voltage dips, swells and spikes. Other long duration r.m.s. voltage variations are mains failures, interruption, harmonic voltage distortion and steady-state overvoltages and undervoltages. This PhD research work deals with voltage dip phenomena only. Initially, the present power network was not designed to accommodate renewable distributed generation (RDG) units. The advent and deployment of RDG over recent years and high penetration of RDG has made the power network more complex and vulnerable to PQ disturbances. It is a well-known fact that the degree of newly introduced RDG has increased rapidly and growing further because of several reasons, which include the need to reduce environmental pollution and global warming caused by emission of carbon particles and greenhouse gases, alleviating transmission congestion and loss reduction. RDG ancillary services support especially voltage and reactive power support in electricity networks are currently being recognized, researched and found to be quite useful in voltage dip mitigation