Showing papers by "Hans Ertl published in 2009"

Digital Current Controller for a 1 MHz, 10 kW Three-Phase VIENNA Rectifier

Abstract: Active three-phase rectifiers operated at switching frequencies of 500 kHz and above, in order to increase their power density, require high-speed current controllers. If these current controllers are implemented purely digitally, which is well established today for 20-200 kHz converter systems, then very high numerical data processing demands result. In this paper, two different types of field-programmable gate arrays (FPGAs) are evaluated for realizing high-speed converter current control. For the implementation of such controllers, not only the FPGA has to be considered but rather the entire signal chain. Two alternative A/D interfaces (including high-speed low-voltage differential signaling data transmission) that are able to handle data sampling rates up to 25 MSa/s are verified. Subsequently, a digital current controller is designed and it is shown how hardware multiplier blocks of modern FPGAs can be used advantageously. Furthermore, the FPGA implementation of high-resolution pulsewidth modulation providing symmetrical pulse patterns for high switching frequencies is described. Measurements taken from a 10 kW VIENNA rectifier laboratory prototype finally demonstrate the high performance of the proposed control concept and show that a low mains current total harmonic distortion of 1.4% can be achieved for such ultrahigh switching frequency converters.

Novel Three-Phase CM/DM Conducted Emission Separator

Abstract: This paper presents two novel three-phase common-mode (CM)/differential-mode (DM) noise separation networks, which are passive and active networks, to be used in electromagnetic compatibility conducted emission (CE) measurements of three-phase equipment. The passive network is analyzed theoretically, and a prototype is constructed and tested. Its evaluation is presented through frequency response measurements and CE tests performed on a three-phase motor drive and verifies that the network is capable of separating the CM and DM information in a CE measurement condition.

Wideband Current Transducer for Measuring AC Signals With Limited DC Offset

Abstract: In many applications, a current measurement that can measure AC currents with DC offset is required. This is not possible using conventional current transformers (CTs) due to the core saturation because of the DC offset. In this paper, a new sensor concept is presented, which consists of a wideband CT and a demagnetizing circuit. The sensor concept is capable of measuring AC currents with DC offset, which have periodic zero crossings, as given in power-factor-corrected (PFC) circuits. Using the demagnetization circuit, the core is actively reset during the zero crossing intervals. The operation principle and design equations are discussed in detail in this paper. For validating the presented concept, three sensors have been built using different core materials, and measurements of the transfer functions as well as operation in a PFC system are presented. A bandwidth from DC up to 20 MHz has been achieved.

Basic linear-mode solar-cell simulators

Abstract: The paper describes basic types of linear-mode power systems for simulating voltage/current characteristics of solar cells modules Starting from a current source with a chain of diodes arranged in parallel (being the most simple equivalent circuit diagram of a solar power module) a very basic solar module simulator using a bipolar power transistor and based on the “amplified diode” concept is developed Furthermore, this principle is modified utilizing a linear-mode series regulator in order to reduce the dissipated power at no-load condition The paper includes a detailed description of the different operating principles, gives dimensioning guidelines and presents also measurement results taken from laboratory prototype systems