An Improved Maximum Power Point Tracking for Photovoltaic Grid-Connected Inverter Based on Voltage-Oriented Control

Abstract—

In this paper, an improved maximum power point (MPP) tracking (MPPT) with better performance based on voltage-oriented control (VOC) is proposed to solve a fast-changing irradiation problem. In VOC, a cascaded control structure with an outer dc link voltage control loop and an inner current control loop is used. The currents are controlled in a synchronous orthogonal d, q frame using a decoupled feedback control. The reference current of proportional–integral (PI) d-axis controller is extracted from the dc-side voltage regulator by applying the energy-balancing control. Furthermore, in order to achieve a unity power factor, the q-axis reference is set to zero. The MPPT controller is applied to the reference of the outer loop control dc voltage photovoltaic (PV). Without PV array power measurement, the proposed MPPT identifies the correct direction of the MPP by processing the d-axis current reflecting the power grid side and the signal error of the PI outer loop designed to only represent the change in power due to the changing atmospheric conditions. The robust tracking capability under rapidly increasing and decreasing irradiance is verified experimentally with a PV array emulator. Simulations and experimental results demonstrate that the proposed method provides effective, fast, and perfect tracking.

Versatile DC-DC Converter

Here is a versatile power coupler that connects a device to 5V-19V DC generated from AC mains by a power adaptor. Power adaptors come in different voltage outputs like 5V (for mobile phones), 12V (for external hard drives) and 19V (for laptops). Sometimes the power adaptor may have a voltage rating higher than the required voltage. With the converter circuit given here, the adaptor can be used to power any device at a lower voltage. 

For instance, by using a 19V laptop adaptor, you can power a TTL circuit at 5V. There can also be other instances when one needs a 3V or 6V supply. All these and many other intermediate voltages are easily possible with this versatile converter circuit when used together with any off-hand power adaptor. 

Adjusting variable resistor VR1 gives the desired output voltage. The output voltage is read using a 0-100µA ammeter, whose series resistance R* is chosen such that the maximum desired voltage could be covered. For instance, if full-scale deflection (FSD) current of the meter is 100 µA and you need an output voltage of up to 15V, then R* = 15/0.0001 = 150 kΩ. The desired value of R* is obtained by using 150-kilo-ohm preset VR2. 

Use of a variable resistor which also has an on/off switch like the one in old radios is recommended. It will cut off the coupler from the input power supply without having to accomodate an additional switch. Also, use a heat-sink with LM317 to handle the desired amount of power. 

Assemble the circuit on a small general-purpose PCB and enclose in a suitable case. Fit the entire PCB inside a glue stick tube as shown in Fig. 2. Affix the female and male connectors on the opposite ends and place the ammeter in between the stick tube. You can directly read the output voltage on the ammeter after due calibration.

Note. You can use a suitable VU meter instead of 0-100µA ammeter and calibrate accordingly.

A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

Abstract—

Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATic COMpensator (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. The effectiveness of the proposed scheme relives the main supply source from the reactive power demand of the load and the induction generator. The development of the grid co-ordination rule and the scheme for improvement in power quality norms as per IEC-standard on the grid has been presented.

A Photovoltaic Array Simulation Model for Matlab-Simulink GUI Environment

A photovoltaic array (PVA) simulation model to be
used in Matlab-Simulink GUI environment is developed and
presented in this paper. The model is developed using basic
circuit equations of the photovoltaic (PV) solar cells including the
effects of solar irradiation and temperature changes. The new
model was tested using a directly coupled dc load as well as ac
load via an inverter. Test and validation studies with proper load
matching circuits are simulated and results are presented here.

SECOND-ORDER SLIDING MODE POWER CONTROL AND GRID FAULT-TOLERANCE OF A DFIG-BASED WIND TURBINE

Abstract--

 This paper deals with power extraction
maximization and grid fault-tolerance of a doubly-fed induction generator-based wind turbine. These variable speed systems have several advantages over the traditional wind turbine operating methods, such as the reduction of the mechanical stress and an increase in the energy capture. To fully exploit this latest advantage, many efforts have been made to develop maximum power point tracking control schemes. In this context, this paper proposes a second-order sliding mode control. This control strategy presents attractive features such as chattering-free behavior (no extra mechanical stress), finite reaching time, and robustness with respect to external disturbances (grid) and unmodeled dynamics (generator and turbine). It seems also well adapted for grid disturbance tolerance.
Simulations using the wind turbine simulator FAST and experiments on a 7.5-kW real-time simulator are carried out for the validation of the proposed high-order sliding mode control approach.

Voltage Controlled PFC Forward Converter Fed PMBLDCM Drive for Air,Conditioner

Abstract—

 In this paper, a permanent magnet brushless DC motor (PMBLDCM) fed through a three-phase voltage source inverter (VSI) is used to drive a compressor load of an air conditioner. The PMBLDCM drive is fed through a diode bridge rectifier (DBR) from single-phase AC mains using a buck forward DC-DC converter as a single-stage power factor correction (PFC) converter. The speed of the compressor is controlled using a concept of the voltage control at DC link proportional to the desired speed of the PMBLDCM. Therefore the VSI performs only as an electronic commutator for the PMBLDCM. The stator current of the PMBLDCM during step change of the reference speed is controlled within the specified limits by an addition of a rate limiter in the reference DC link voltage. The proposed PMBLDCM drive with the voltage control is designed, modeled and its performance is simulated in Matlab-Simulink environment for an air conditioner driven through a PMBLDC motor. The obtained results of the proposed speed control scheme are presented to demonstrate an improved efficiency of the PMBLDCM drive system with PFC feature in wide range of the speed and the input AC voltage.

Three-Phase Soft-Switching Inverter With Minimum Components

Abstract—

 In this paper, a novel three-phase soft-switching inverter is presented. The inverter-switch turn on and turn off are performed under zero-voltage switching condition. This inverter has only one auxiliary switch, which is also soft switched. Having one auxiliary switch simplifies the control circuit considerably. The proposed inverter is analyzed, and its operating modes are explained in details. The design considerations of the proposed inverter are presented. The experimental results of the prototype inverter confirm the theoretical analysis.