Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the proposed MPPT system and other techniques used in the past is that the PV array output power is used to directly control the DC/DC converter, thus reducing the complexity of the system. The resulting system has high-efficiency, lower-cost and can be easily modified to handle more energy sources (e.g., wind-generators). The experimental results show that the use of the proposed MPPT control increases the PV output power by as much as 15% compared to the case where the DC/DC converter duty cycle is set such that the PV array produces the maximum power at 1 kW/m/sup 2/ and 25/spl deg/C.

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Development of a microcontroller-based, photovoltaic maximum power point tracking control system

This paper presents an overview of single-phase inverters developed for small distributed power generators. The functions of inverters in distributed power generation (DG) systems include dc-ac conversion, output power quality assurance, various protection mechanisms, and system controls. Unique requirements for small distributed power generation systems include low cost, high efficiency and tolerance for an extremely wide range of input voltage variations. These requirements have driven the inverter development toward simpler topologies and structures, lower component counts, and tighter modular design. Both single-stage and multiple-stage inverters have been developed for power conversion in DG systems. Single-stage inverters offer simple structure and low cost, but suffer from a limited range of input voltage variations and are often characterized by compromised system performance. On the other hand, multiple-stage inverters accept a wide range of input voltage variations, but suffer from high cost, complicated structure and low efficiency. Various circuit topologies are presented, compared, and evaluated against the requirements of power decoupling and dual-grounding, the capabilities for grid-connected or/and stand-alone operations, and specific DG applications in this paper, along with the identification of recent development trends of single-phase inverters for distributed power generators.

Topologies of single-phase inverters for small distributed power generators: an overview

This paper presents an overview of motor drive technologies used for safety-critical aerospace applications, with a particular focus placed on the choice of candidate machines and their drive topologies. Aircraft applications demand high reliability, high availability, and high power density while aiming to reduce weight, complexity, fuel consumption, operational costs, and environmental impact. New electric driven systems can meet these requirements and also provide significant technical and economic improvements over conventional mechanical, hydraulic, or pneumatic systems. Fault-tolerant motor drives can be achieved by partitioning and redundancy through the use of multichannel three-phase systems or multiple single-phase modules. Analytical methods are adopted to compare caged induction, reluctance, and PM motor technologies and their relative merits. The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure. The modular single-phase approach offers a good compromise between size and complexity but suffers from high total harmonic distortion of the supply and high torque ripple when faulted. For each specific aircraft application, a parametrical optimization of the suitable motor configuration is needed through a coupled electromagnetic and thermal analysis, and should be verified by finite-element analysis.

Overview of Electric Motor Technologies Used for More Electric Aircraft (MEA)

Photovoltaic systems normally use a maximum power point tracking (MPPT) technique to continuously deliver the highest possible power to the load when variations in the insulation and temperature occur. It overcomes the problem of mismatch between the solar arrays and the given load. A simple method of tracking the maximum power points (MPPs) and forcing the system to operate close to these points is presented. The principle of energy conservation is used to derive the large- and small-signal model and transfer function. By using the proposed model, the drawbacks of the state-space-averaging method can be overcome. The TI320C25 digital signal processor (DSP) was used to implement the proposed MPPT controller, which controls the DC/DC converter in the photovoltaic system. Simulations and experimental results show excellent performance.

Implementation of a DSP-controlled photovoltaic system with peak power tracking

A novel maximum-power-point-tracking (MPPT) controller for a photovoltaic (PV) energy conversion system is presented. Using the slope of power versus voltage of a PV array, the proposed MPPT controller allows the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single-stage configuration is implemented, resulting in size and weight reduction and increased efficiency. The proposed system acts as a solar generator on sunny days, in addition to working as an active power line conditioner on rainy days. Finally, computer simulations and experimental results demonstrate the superior performance of the proposed technique.

Novel maximum-power-point-tracking controller for photovoltaic energy conversion system

Microcomputer-based control of a residential photovoltaic power conditioning system is described. The microcomputer is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics. The control functions are implemented using Intel 8751 single-chip microcomputer-based hardware and software. The controller has been tested in the laboratory with the prototype power conditioner and shows excellent performance.

Microcomputer Control of a Residential Photovoltaic Power Conditioning System

A microcomputer-based four-quadrant control system of a switched reluctance motor is described. The control was implemented with a speed feedback loop, a torque feedback loop, and both the torque and speed feedback loops combined. In addition the controller incorporates a startup operation, sequencing, and synchronized angle steering control. The angle controller was designed using dedicated digital hardware, whereas the other functions were implemented using an Intel 8751 single-chip microcomputer. The complete control system was tested in the laboratory with a 5-hp drive, and the test results were found to be excellent.

Microcomputer Control of Switched Reluctance Motor

A novel drive system for a switched-reluctance (SR) motor is described. The system needs no position sensor and has no discrete current sensors for regulating phase currents. Instead, the drive uses power MOSFET transistors with integrated pilot devices for current feedback when the switches are 'off', a fixed off-time chopping strategy is used to control the phase currents. To eliminate the position sensor normally required for SR motor control, the controller estimates the rotor position using phase inductance measurements. This position estimation scheme is sufficiently precise to allow positioning of the phase firing pulses to within approximately two electrical degrees of the desired rotor angle, and full four-quadrant operation of the system is possible. A laboratory prototype system has been built and tested at speeds up to 3000 rpm. The system shows good performance in all four operating quadrants, including zero speed. The entire control for the system is implemented in a single low-cost microprocessor. >

Application of sensor integration techniques to switched reluctance motor drives

A microcomputer-based drive system for a switched reluctance motor requires no rotor position sensor and no discrete current sensors. Phase excitation is synchronized with rotor position by indirectly estimating rotor position according to instantaneous phase inductance. Current regulation is achieved by incorporating pilot devices for current sensing into the switching devices of the power converter and by employing a fixed off-time current chopping strategy. One application is for use in a laundering machine.

Switched reluctance motor drive system and laundering apparatus employing same

A commutator for a microcomputer based switched reluctance drive employs a selectively addressable non-volatile memory, e.g. a ROM, to store stator phase firing patterns and facilities selective adjustment of turn-on angle and pulsewidth of phase switching current pulses. Firing patterns differing only in pulsewidth of their respective pulses can be stored in different sections of the memory or in the same section where word bit width permits. The adjustment of pulse position and duration allows torque control of the motor over a very wide speed range.

Paul Michael Szczesny

Papers

Microcomputer Control of a Residential Photovoltaic Power Conditioning System

Microcomputer Control of Switched Reluctance Motor

Application of sensor integration techniques to switched reluctance motor drives

Switched reluctance motor drive system and laundering apparatus employing same

Commutator for switched reluctance drive