Efficient Maximum Power Point Tracking for a Distributed PV System under Rapidly Changing Environmental Conditions

Abstract—

When conventional maximum power point tracking (MPPT) techniques are required to operate fast under rapidly changing environmental conditions, a large power loss can be caused by slow tracking speed, output power fluctuation, or additionally required ad hoc parameters. This paper proposes a fast and efficient MPPT technique that minimizes the power loss with the adaptively binary-weighted step (ABWS) followed by the monotonically decreased step (MDS) without causing output power fluctuation or requiring additional ad hoc parameter. The proposed MPPT system for a photovoltaic (PV) module is implemented by a boost converter with a microcontroller unit. The theoretical analysis and the simulation results show that the proposed MPPT provides fast and accurate tracking under rapidly changing environmental conditions. The experimental results based on a distributed PV system demonstrate that the proposed MPPT technique is superior to the conventional perturb and observe (P&O) technique, which reduces the tracking time and the overall power loss by up to 82.95%, 91.51% and 82.46%, 97.71% for two PV modules, respectively.

Modeling of Electric Vehicle Loads for Power Flow Analysis based on PSAT

Abstract—

This paper proposes the modeling of electric vehicle(EV) loads for power flow analysis based on User Define Models (UDMs) in power system analysis toolbox (PSAT) programming, According to the development of EV technology especially motor controller and battery, the EV has totally designed and made for using in city area as small city cars. To study the performance of EV, this aims to present the model of EV loads for using to solve power flow analysis in the real power system. EV load is modeled as the function box equivalent on PSAT that can connect to the single line diagram of power system model. The IEEE 14 bus system is selected for simulating the performance of EV and charging station which compared between PQ load base case and EV load. The simulation result showed that the EV load was installed at bus No.14. The rated power of EV load was increased from 5.0 p.u. to 79 p.u. This proposed EV load model can be used to solve the power flow analysis with continuation power flow (CPF) method. The EV load model is directly effected to voltage stability margin when the EV load increased. This study can be verified that proposed EV load can use to study the EV load in the future works.

An Improved MPPT Method for PV system with Fast-Converging Speed and Zero Oscillation

Abstract—

Maximum power point (MPPT) tracking is essential for Photovoltaic (PV) systems to ensure the highest power output of PV arrays under any environmental condition. Comparing to other techniques, the Beta method shows advantages in terms of tracking speed, steady state performance, and simple implementation. However, the conventional Beta can be further improved by minimizing oscillations arounad the maximum power point (MPP) under steady state and increasing tracking speed in response to rapid changing of irradiance or temperature. An improved Beta-parameter based MPPT method is proposed in this paper to achieve the above objectives. An adaptive scaling factor is introduced and utilized in the MPPT mechanism, which enhances the tracking speed and is easily applied for any PV power system. Furthermore, the proposed method can identify and maintain the middle point of the three-level perturbations, which eliminate the oscillations at steady state. The control mechanism is not limited by specific operating conditions and illustrates superior performance over traditional methods with regards to transient response and steady state performance, which contributes to effective solar power harvesting. Followed by theoretical analysis, the simulation and experimental evaluation validate the claimed advantages of the proposed MPPT solution.

MATLAB/Simulink Model Of Wind Farm To Weak Grid Connection

Abstract

Wind Farms (WF) employing squirrel cage induction generator (SCIG) directly connected to the grid; represent a large percentage of the wind energy conversion systems around the world. In facilities with moderated power generation, the WF is connected through medium voltage (MV) distribution headlines. In this scheme, the power generated is comparable to the transport capacity of the grid. This case is known as Wind Farm to Weak Grid Connection, and its main problem is the poor voltage regulation at the point of common coupling (PCC). Thus, the combination of weak grids, wind power fluctuation and system load changes produce disturbances in the PCC voltage, worsening the Power Quality and WF stability. This situation can be improved using control methods at generator level, or compensation techniques at PCC. In case of wind farms based on SCIG directly connected to the grid, is necessary to employ the last alternative. Custom power devices technology (CUPS) results are very useful for this kind of application. In this paper is proposed a compensation strategy based on a particular CUPS device, the Unified Power Quality Compensator (UPQC). A customized internal control scheme of the UPQC device was developed to regulate the voltage in the WF terminals, and to mitigate voltage fluctuations at grid side. The internal control strategy is based on the management of active and reactive power in the series and shunt converters of the UPQC, and the exchange of power between converters through UPQC DC– Link. This approach increases the compensation capability of the UPQC with respect to other custom strategies that use reactive power only. MATLAB/Simulink ® Simulations results show the effectiveness of the proposed compensation strategy for the enhancement of Power Quality and Wind Farm stability.

Control of Wind Energy Conversion System with SOFC Based Fuel Cell at Variable Speed

Abstract -- 

In recent years the statistical data conveys that Doubly-fed Induction Generator (DFIG) based wind turbine with variable speed and variable pitch control is the most common wind turbine in the growing wind market. Due to the fluctuating nature of wind power, a dynamic model of Solid Oxide Fuel Cell energy source is integrated with the wind turbine for sudden load changes to ensure reliable and efficient operation of the power system. This paper deals with simulation of a wind turbine based on a doubly-fed induction machine hybrid with fuel cell energy system used in generating mode to produce electrical energy on a power network. Among the various renewable energy sources, fuel cell is gaining more popularity due to their higher efficiency, cleanliness and cost-effective supply of power demanded by the consumers. Wind Energy is gaining interest now-a-days as one of the most important renewable sources of energy due to its eco-friendly nature. But the major disadvantage lies in variable speed wind generation, so a vector control technique of Wind driven doubly fed Induction Generators is required. The speeds above and below Synchronous speeds are obtained using a bidirectional power flow converter. The wind energy conversion system (WECS) is equipped with a DFIG and two back-to-back Pulse Width Modulated (PWM) Insulated Gate Bipolar Transistors (IGBTs) based voltage source converters (VSCs) in the rotor circuit. A dynamic model of SOFC based fuel cell using Nernst equation and the response of the fuel cell for sudden load changes is analysed and simulated. Simulation results for different operating conditions are demonstrated to reveal the performance of the proposed technique.

A Robust DC-Link Voltage Control Strategy to Enhance the Performance of Shunt Active Power Filters Without Harmonic Detection Schemes

Abstract—

Shunt active power filters (SAP F s) implemented without harmonic detection schemes are susceptible to sudden load variations. This paper proposes a robust control strategy to reduce this drawback. In this strategy, the dc-link voltage is regulated by a hybrid control technique combining a standard proportional–integral PI and a sliding-mode (SM) controllers. The SM scheme continuously determines the gains of the PI controller based on the control loop error and its derivative. The chattering due to the SM scheme is reduced by a transition rule that fixes the controller gains when steady-state condition is reached. This controller is termed as dual-sliding-mode-proportional–integral. The phase currents of the power grid are indirectly regulated by double-sequence controllers with two degrees of freedom, where the internal model principle is employed to avoid reference frame transformation. The proposed control strategy ensures zero steady-state error and improves the performance under hard transients such as load variation. Additionally, it presents robustness when the SAP F is operating under unbalanced conditions. Experimental results demonstrate the performance of the proposed control scheme.

A Series-Parallel Current-Driven Full-Bridge DC/DC Converter

Abstract—

This paper presents a novel Series-Parallel Current-Driven (SPCD) full-bridge DC/DC converter, which is able to process and deliver power efficiently over a wide range of load variations. In order to guarantee reliable operation of high frequency DC/DC converters, the converter should be able to sustain soft-switching for a wide range of operating conditions. The SPCD full-bridge converter, proposed in this paper, is able to offer soft-switching for the input power semiconductors and smooth commutations for the output diodes. Also, the particular structure of the proposed converter eliminates the need for extra auxiliary circuits to provide reactive current for soft-switching at light loads. The proposed topology can fully eliminate voltage spikes across the output diodes by providing smooth and lossless commutations for the output diodes. Thus, the proposed converter can be a efficient and reliable solution for variety of applications with a high switching frequency and a high output voltage. The SPCD full-bridge converter has the ability to integrate all magnetic components into an integrated transformer in order to achieve a high power density. The integrated transformer is thoroughly analysed using ANSYS HFSS. Simulation and experimental results confirm the superior performance of the proposed SPCD full-bridge DC/DC converter.