1.An Embedded System in Smart Inverters for Power Quality and Safety Functionality:
The electricity sector is undergoing an evolution that demands the development of a network model with a high level of intelligence, known as a Smart Grid. One of the factors accelerating these changes is the development and implementation of renewable energy. In particular, increased photovoltaic generation can affect the network’s stability.
One line of action is to provide inverters with a management capacity that enables them to act upon the grid in order to compensate for these problems. This paper describes the design and development of a prototype embedded system able to integrate with a photovoltaic inverter and provide it with multifunctional ability in order to analyze power quality and operate with protection. The most important subsystems of this prototype are described, indicating their operating fundamentals. This prototype has been tested with class A protocols according to IEC 61000-4-30 and IEC 62586-2. Tests have also been carried out to validate the response time in generating orders and alarm signals for protections. The highlights of these experimental results are discussed. Some descriptive aspects of the integration of the prototype in an experimental smart inverter are also commented upon.
The design has focused upon the appropriate timing requirements for measurements defined in IEC 61000-4-30. These requirements have led to a data architecture design based on a set of critical temporary loops, where the various groups of equipment functions are processed: A half-cycle loop that directly processes the data acquisition for transient events or those of a highly random nature.
A two-cycle loop, which has been implemented on this equipment in an original manner, which the team has termed quasi-stationary is used for rapid measurements with some stationarity, where the protection functions are processed. Finally, a 10-cycle loop dedicated to processing functions of purely stationary power quality parameters. The data exchange is carried out by two deterministic FIFO stacks, managed from the fastest half-cycle loop, and synchronized to two and ten cycles. It is important to emphasis the great functional capacity of the prototype at the Power Quality level, where it is able to endow the inverter with great added value, transforming it Power Quality Analyzer (PQA). In order to do this, ultimate-generation event-detection algorithms, such as those based on Higher-order statistics (HOS), have been incorporated, as well as other, original algorithms for passively detecting is landing, based upon multiple-method weighting. The equipment has been subjected to Class A and Class S testing procedures, according to standard IEC 62586-2, obtaining good results in all of the tests whose conditions were within the limitations of our laboratory resources.
Unfortunately, due to these limitations it was impossible to address all test scenarios, so it cannot be concluded that the equipment can be considered Class A, but everything indicates that it could pass a rigorous certification of this kind. In addition, based on the tests of uncertainty in measurements and temporary response to alarms, a positive validation in system behavior can be concluded. Furthermore, its proper functioning under the SIDER project, sponsored by the Ministry of Science and Innovation of Spain and supervised by companies in the electricity sector, where the prototype’s suitability for being integrated into the power electronics of a photovoltaic inverter has been proven.
Project: Electrical Projects, Microcontroller Projects, Microprocessor Projects, Power Electronics Projects, Security Projects, Sensor Projects, Signal Processing Projects, Telecommunications Projects, Wireless Projects
2.Earth Fault Location Based on Evaluation of Voltage Sag at Secondary Side of Medium Voltage/low Voltage Transformers:
The main reasons for installation of power quality meters in distribution transformer substations are power quality monitoring and global evolution of electrical network towards the `smart grid’. In case that all measurements from the meters are properly synchronized and centralized, new possibilities of control or evaluation of the network are enabled.
This contribution proposes the possibility for an earth fault localization with the aid of synchronized data recorded on the low-voltage side of the medium voltage/low voltage transformers in compensated neutral distribution networks which are equipped with auxiliary resistor for short-time increasing of the active part of the fault current. The described method uses voltage sags evoked by connecting of the auxiliary resistor for locating the faulty section. The proposed method is tested with the help of numerical model which presents a part of the distribution network. Based on the simulation results, it is confirmed that the principle of the described method is useful for delimiting of faulty section in compensated networks during solid and low-impedance EFs. Since the sensitivity of the method strongly depends on the fault current level and thus on a fault resistance, the sensitivity of faulty section definition during high-impedance EF is very low.
Project: Electrical Projects, Energy Saving Projects, IEEE Electrical Projects, Power Electronics Projects
3.FPGA Implementation of an Interpolator for PWM applications:
To obtain the required oversampling ratio, five separate interpolator stages were designed and implemented. Each interpolator stage performed up sampling by a factor of two followed by an image-rejection lowpass FIR filter. Since, each individual interpolator stage up samples the input signal by a factor of two, interpolation filters were realized as a half-band FIR filters.
This kind of linear-phase FIR filters have a nice property of having every other filter coefficient equal to zero except for the middle one which equals 0.5. By utilizing the half-band FIR filters for the actual realization of the interpolation filters, the overall computational complexity was substantially reduced. In addition, several multidate techniques have been utilized for deriving more efficient interpolator structures.
Hence, the impulse response of individual interpolator filters was rewritten into its corresponding polyphase form. This further simplifies the interpolator realization. To eliminate multiplication by 0.5 in one of two polyphase sub filters, the filter gain was deliberately increased by a factor of two. Thus, one polyphase path only contained delay elements. In addition, for the realization of filter multipliers, a multiple constant multiplication, (MCM), algorithm was utilized. The idea behind the MCM algorithm, was to perform multiplication operations as a number of addition operations and appropriate input signal shifts. As a result, less hardware was needed for the actual interpolation chain implementation. For the correct functionality of the interpolator chain, scaling coefficients were introduced into each interpolation stage. This is done in order to reduce the possibility of overflow. For the scaling process, a safe scaling method was used. The actual quantization noise generated by the interpolator chain was also estimated and appropriate system adjustments were performed.
Project: Electrical Projects, MATLAB Projects, Power Electronics Projects
4.Short-Circuit Contributions from Fully-Rated Converter Wind Turbines: Modeling and Simulation of Steady-State Short-Circuit Contributions from FRC Wind Turbines in Offshore Wind Power Plants:
In recent years there has been an increase in wind power plants installed out at sea. The generated power of wind turbine generators (WTGs) is collected through numerous cables into a single hub, the offshore platform. Subsequently, this platform is interconnected with the onshore main grid through a further stretch of cable. In this project, a method has been developed in order to determine the steady-state short-circuit contribution from multiple FRC WTGs. This methodology is based on an iterative algorithm, and has been implemented in the simulation tool Power Factory In the event of a fault, a sudden increase in current, so called short-circuit current, will occur somewhere in the system. The short-circuit current will, depending on the duration and location of the fault, potentially harm the power system.
In order to accurately determine the dimensions and rating of the equipment installed in the offshore wind power plant (OWPP), the magnitude of this current needs to be studied. Furthermore, depending on the country in which the OWPP is installed, the transmission system operator (TSO) might pose different low-voltage-ride-through (LVRT) requirements on the system. One such requirement is that the installed turbines should provide voltage regulation through injection of reactive current. A type of generator able to achieve this is a so-called fully-rated converter wind turbine generator (FRC WTG). Through a power electronic interface, the reactive and active current components of the generator can be freely controlled. With a high level of reactive current injected during a fault in the OWPP, the short-circuit contribution from these FRC WTGs needs to be evaluated.
Project: Power Electronics Projects, Power Harvesting Projects, Robotics Projects