Four-quadrant Power Supply Research Articles

Analysis and mitigation of errors in external quantum efficiency measurement of solar cells embedded in solar modules

Accurate measurement of external quantum efficiency(EQE) of cells embedded in PV modules is critical for reducing the uncertainty of the flash I-V measurements during secondary calibration of PV modules. This paper presents detailed analysis and quantification of possible sources of errors due to various factors such as shading of target cell, load point determination, variance in cell-to-cell electrical properties and use of AC probe light. Moreover, the technique is also extended for measuring EQE of cells in the degraded modules by changing different cell parameters, thus enabling use of this technique for non-destructive failure analysis. Separate analysis for biasing the module with a programmable load and a four-quadrant power supply is presented. Appropriate correction factors are obtained for accurate load point determination for the two cases with less than 3 % error in the absolute EQE.

Implementation of Power Operational Amplifier with Source-Sink Output Stage

The paper deals with the design and realization of the power operational amplifier. Its parameters are optimized for using in four-quadrant source, especially the frequency range, slew rate, wide range of output voltage, large output current, fast current limitation and low power losses. The power operational amplifier can find utilization in the output stage of the four-quadrant power supply, low-frequency amplifiers, supply sources of servomotors etc. Whole connection is divided into single blocks and they are described in detail. The experimental results that show important static and dynamic parameters of the realized power operational amplifier are presented in the paper.

The Wendelstein 7-X Trim Coil System

The magnet system of the fusion experimental device Wendelstein 7-X (W7-X) contains superconducting as well as normal conducting coils. Seventy superconducting coils are forming the steady state main field to confine the plasma. Inside of the plasma vessel, ten control coils, made of copper, will be placed to modify the strike points of the plasma at the divertor. In addition, a set of five normal conducting, water cooled trim coils will increase the experimental flexibility by providing a means to balance the divertor heat loads among the five field periods. The coils will be placed at the outer surface of the cryostat of W7-X. There are four coils (type A) with equal shape; the fifth coil (type B) has a slightly different shape due to space restrictions. The coils have dimensions of 3.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 3.3 m with 48 turns and will be operated with currents of up to 1.8 kA (type A). The other coil (type B) has a smaller size of 2.8 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\times$</tex></formula> 2.2 m, compensated by a higher number of turns and a higher operation current of 1.95 kA. Five independent power supplies are being fabricated to operate the coils with a maximum of flexibility. The concept is based on four-quadrant power supplies using Insulated-Gate-Bipolar-Transistors. The trim coil package consisting of the five coils plus the five power supplies is being designed and built in collaboration between IPP, Germany and PPPL, USA, partly funded by the Department of Energy.

The Trim Coils for the Wendelstein 7-X Magnet System

The magnet system of the fusion experiment Wendelstein 7-X (W7-X) consists of superconducting as well as normal conducting coils. 50 non planar superconducting coils are forming the main field, 20 planar superconducting coils allow varying the shape of the plasma. Inside of the plasma vessel 10 normal conducting control coils will be placed to modify the strike points of the plasma at the divertor. In addition a set of five normal conducting trim coils has been designed to allow the correction of error fields and to increase the experimental flexibility. The coils will be placed at the outer surface of the outer vessel of W7-X. Four out of five coils have identical size and shape. They have dimensions of 3.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 3.3 meters with 48 turns and will be operated with currents of up to 1.8 kA. The other coil type has a smaller size of 2.8 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex></formula> 2.2 meters, but a higher number of turns and a higher operating current of 1.95 kA. Both types of trim coils will be made of square copper hollow profile with an integrated cooling channel. Five independent power supplies will be used to energize the coils. The present concept is based on four-quadrant power supplies. The control system will allow the local control as well as the remote control of the five power supplies from an external control room.

Experimental setup for camera-based measurements of electrically and optically stimulated luminescence of silicon solar cells and wafers

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions.

A novel four-quadrant power supply for low-energy correction magnets

This paper describes an efficient power supply to feed low-energy correction magnets in particle accelerator applications, where a controlled current with trapezoidal profile and four-quadrant operation is needed. The selected design is based on an AC–DC matrix converter topology, which uses the Space Vector Modulation (SVM) technique to obtain a near unity power factor at the AC input and output DC current regulation. This topology allows performing high-frequency isolation, while four-quadrant operation is maintained, and reducing volume and weight as compared with the classical thyristor (SCR)-based technology. Control tasks are implemented on an all-digital control card: output current regulation is accomplished in a digital signal processor device and SVM is implemented in a Field-Programmable Gate-Array. Simulations and experimental results of a 1.2 kW prototype validate the design.