172.

B. Krüger, S. Gruber and S. Soter, "Controlling of medium voltage power-factor of photovoltaic power plants from the low voltage side" in 2013 IEEE Energy Conversion Congress and Exposition, 2013, pp. 569--574.

Abstract:
The effort to make the production of electrical energy much more environmental-friendly, large conventional power plants will be replaced by several smaller regenerative power plants. In order to improve stability and controllability, these smaller power plants are supposed to control the active power, the reactive power and the power factor in the medium voltage grid like conventional power plants. This paper will discuss three different methods to control the medium-voltage power factor from the low voltage side in consideration of parasitic effects from cables and transformers to fulfill the guidelines at the grid connection point. A method with a self-learning-algorithm will be implemented and proven by simulations and measurements on a test bench with inverter and 400 V to 10 kV grid transformer. The self-learning-algorithm will give the opportunity to reach every required power factor at the grid connection point.

171.

A. Bartsch, F. Senicar, S. Kratz and S. Soter, "Enhanced FPGA based three level space vector pulse width modulation with active neutral point balancing" in 2013 IEEE Energy Conversion Congress and Exposition, 2013, pp. 1748--1753.

Abstract:
This paper presents an FPGA based implementation of an improved space vector pulse width modulation for neutral point clamped three-level topologies. For this purpose the flatspace modulation calculating the timings is used in combination with an optimized switching pattern to reduce the switching edges to a minimum. Additionally a combination of two methods for balancing the neutral point is developed which are both implemented without adding any additional harmonics to the modulated output.

170.

S. Gruber, B. Krüger and S. Soter, "High force tubular linear actuator with integrated eddy current brake for spring-loaded systems" in 2013 IEEE AFRICON, 2013, pp. 1--5.

Abstract:
In order to meet safety standards in manufacturing industry many production machines are equipped with safety stop functions based on spring-loaded systems. This paper deals with an integrated eddy current brake of a high force tubular permanent magnet linear actuator for hydraulic applications with small actuating pathes. An analytical description of different design criteria for the integrated eddy current brake are shown. The special not rotational symmetrical design of the tubular linear actuator is transferred to a 2D transient FEM simulation model to predict the braking behavior caused by the spring load in case of an emergency stop. Measurements on a test bench are in good agreement with the simulation results and are used to validate the model.

169.

F. Senicar, A. Bartsch, K. Klitzke and S. Soter, "Improved high bandwidth current controller for FPGA based inverter drives" in 2013 IEEE AFRICON, 2013, pp. 1--6.

Abstract:
This paper presents the improvement of the precision and bandwidth of the current control loop implemented in a field programmable gate array (FPGA) based inverter. By compensating the nonlinear effects of the IGBT power stage with a feed forward control, the current controller is relieved resulting in an output current with less harmonics and a better frequency response. In order to improve the current control loop even further, a current observer, based on a Luenberger observer is implemented.

168.

A. Uphues, K. Nötzold, R. Wegener, K. Fink, M. Bragard, R. Griessel and S. Soter, "Inverter based test setup for LVRT verification of a full-scale 2 MW wind power converter" in 2013 15th European Conference on Power Electronics and Applications (EPE), 2013, pp. 1--5.

Abstract:
With increased wind power penetration, grid codes of system operators require low voltage ride through (LVRT) capability for wind turbines (WT). This paper describes a full power test bench, designed to evaluate the functionality of grid connected converter in nominal operating mode and in case of LVRT. To verify the LVRT capability an inverter based voltage sag generator (VSG) is developed which emulates grid failures.

167.

A. Uphues, K. Nötzold, R. Wegener and S. Soter, "SOGI based grid fault detection for feeding asymmetrical reactive currents to fulfill LVRT requirements" in 2013 IEEE AFRICON, 2013, pp. 1--5.

Abstract:
Due to the increasing wind power penetration, grid codes of system operators require low voltage ride through (LVRT) capability for wind turbines (WT). Additionally the WT has to support the power system stability in LVRT cases by supporting the grid with reactive power. The amount of reactive power feed-in depends on the type of grid fault and the depth of the voltage dip. Therefore this paper shows a reliable grid voltage monitoring consisting on a second order generalized integrator (SOGI) structure. The resulting phase locked loop (PLL) is tolerant against grid faults and the amplitudes and phase angles of the individual phase voltages are detected.

166.

A. Uphues, K. Nötzold, R. Wegener, S. Soter and R. Griessel, "Support of grid voltages with asymmetrical reactive currents in case of grid errors" in 2013 IEEE International Conference on Industrial Technology (ICIT), 2013, pp. 1781--1786.

Abstract:
Due to the increasing wind power penetration, grid codes of system operators require low voltage ride through (LVRT) capability for wind turbines (WT). Additionally the WT has to support the power system stability in LVRT cases by supporting the grid with reactive power. By feeding symmetrical reactive currents in case of asymmetrical grid errors, as required in many actual grid codes, the phase voltage of the undistorted phase will increase above the upper voltage limit. This paper shows a strategy to feed asymmetrical reactive currents into the distorted grid without increasing the phase voltage in the undistorted phase.

165.

A. Uphues, K. Nötzold, R. Wegener, S. Soter and R. Griessel, "Inverter based voltage sag generator with PR-controller", 2012, pp. 1037--1042.

Abstract:
Due to the increasing wind power penetration, grid codes of system operators require low voltage ride through (LVRT) capability for wind turbines (WT). Additionally the WT has to support the power system stability in LVRT cases. To evaluate the LVRT capability of grid connected converter, a voltage sag generator (VSG) is required to emulate grid failures. This paper introduces a three phase programmable inverter based VSG, which is equipped with a cascaded control structure consisting of proportional resonant (PR) current controller and PR voltage controller. The described VSG is able to emulate all required voltage sags, propagated through a delta star connected transformer, very precisely. The control structure has been simulated and tested successfully on a 2MW full power testbench.

164.

A. Bartsch, F. Senicar and S. Soter, "Design of a scalable FPGA based inverter for complex drive systems" in 2012 IEEE International Conference on Industrial Technology, 2012, pp. 1086--1091.

Abstract:
This paper presents the design and implementation of motor control peripherals on a field programmable gate array (FPGA) in conjuction with a microcontroller, forming a powerful and flexible computing platform for inverter drives. The implementation of a vector controlled pulse width modulation, an encoder interface and a current measurement unit are described. Furthermore a current control unit is implemented on the FPGA in order to relieve the microcontroller from some high frequency real-time tasks. The FPGA and the microcontroller form a flexible control board which is used for different projects including high speed multi level inverters and four quadrant drive systems. Furthermore multi axes systems can be implement without any performance drawbacks and just a moderately increased effort optimizing the use of an FPGA.

163.

S. Gruber, R. Wegener and S. Soter, "Detent force reduction of a tubular linear drive by using a genetic algorithm and FEM - verification of simulation results" in IECON 2012 - 38th Annual Conference of the IEEE Industrial Electronics Society, 2012, pp. 1731--1736.

Abstract:
In order to meet industrial safety standards in eccentric presses, the detent force caused by the reluctance change between permanent magnet (PM) and stator teeth of the acting high force tubular permanent magnet linear synchronous machines (PMLSM) should be reduced. The detent force is generated by two components: the slot effect which is already decreased by the closing slot technique and proven in [3] and the end effect which will be optimized by using auxiliary poles at the end of the machine. Therefore a special genetic algorithm (GA) is developed which rates the simulation results of the FEM and produces new auxiliary poles. The combined simulation tries to find an optimal size and position for auxiliary poles to reduce the whole detent force. The numerical calculations propose a minimized detent force caused by the located poles, which is independent from the length of the machines (1 to 5 modules). The result will be proven by measurements.