Armin Dietz

Sensorless vector control of a permanent magnet synchronous generator for micro hydro power

In vector controlled operation of a permanent magnet synchronous generator (PMSG), the rotor position must be known at all times. As position sensors are expensive and vulnerable in harsh environment, sensorless strategies are becoming more and more popular. The paper gives a short overview over common sensorless position estimation strategies and shows a MATLAB/Simulink simulation for the sensorless methods Flux Estimation and Sliding Mode Observer. Furthermore, a vector control on a PMSG including a sliding mode observer model for sensorless rotor position estimation is implemented on a TI Concerto processor (Cortex M3 and C28x DSP dualcore) for a frequency inverter for micro hydro power generation. A new approach is the utilization of a dualcore processor in this application: the Cortex M3 runs communication and general system tasks in a micro hydro power generation site, whereas the C28x DSP focuses on the generator control task. TIs real-time operating system SYS/BIOS runs on both cores, guaranteeing easy extension of functionality.

Modeling and power flow analysis of cascaded doubly-fed induction machines

In this paper, a modeling approach for a brushless doubly-fed induction machine is proposed using an equivalent system of cascaded doubly-fed induction machines. A Steady-state and a transient model are developed and the results show a good agreement to measurements conducted on a set of two 1.5 kW doubly-fed induction machines. One main aspect of this work is the examination of the electrical and mechanical power flow of the combined machines with regard to the required inverter size.

Energetic Simulation of Complex Mechatronic Drive Systems over Complete Drive Cycles

This paper presents a simulation model, which enables the energetic simulation of complex mechatronic powertrains over complete drive cycles. One focus of this work is on reducing the simulation duration to enable the simulation of extended drive cycles on the one hand, and the possibility to optimize drive cycles on the other hand. Furthermore, the program allows the user to assemble an energetically optimized selection of propulsion components.

Methodical approach for designing electric propulsion systems containing two motors

To reduce the environmental impact of the petroleum-based transport, new safe, cost and energy optimized electric vehicle propulsion concepts are mandatory. Besides the activities for improving the battery and power electronics technologies, highly integrated units and new functional component operation strategies are of special interest. In this paper, a methodical approach for deriving electric motor design values for electric propulsion systems, especially usable for urban vehicles, including two electric machines, is shown. Considering the overall results a new highly integrated electric drive containing two different sized electric motors, two clutches and a compressor in one single unit is used as an example. The design led to a variety of functional motor modes presented in the paper. On upscaled measurement results, the efficiency tables for 50 kW and 10 kW PSM- and ASM-motors are used for a combined working strategy. Using the 10 kW motor on low torque and speed requests the traction energy demand of a urban vehicle could be reduced in the range up to 5% on several drive cycles.

The brushless doubly fed induction machine as generator for small hydro power - machine design and experimental verification

This paper presents the brushless doubly fed induction machine (BDFM) as an alternative choice as generator for small hydro power plants. Looking at this application, the BDFM offers many advantages, mainly the fact that a speed-variable operation in a convenient speed range is possible with a fractionally-rated inverter without the need for slip rings and brushes. An introduction to analytic modeling of the brushless doubly fed machine is given by using an equivalent circuit model, and a machine design process is shown. At first, the main dimensions of the machine and its rating are discussed considering the tangential stress in the air gap. Afterwards the parameters for the equivalent circuit are derived from the machines geometry. Because of the complex fields in the BDFM, the well-known calculation approaches for standard machines have to be extended. The model and the design process are verified using finite elements simulations and experimental tests with the implemented prototype machine on the test bench.

FPGA based finite-set model predictive current control for small PMSM drives with efficient resource streaming

This paper discusses the experimental implementation of a finite control set model predictive control (FCS-MPC) approach for small permanent magnet synchronous machines (PMSM) on a field programmable gate array (FPGA). The small drives investigated in this paper have electrical time constants in the range of microseconds. The main challenge of using FCS-MPC is the high calculation effort. By respecting each switching possibility, the calculation effort increases exponentially with the time horizon. Therefore, methods for limiting the calculations in order to reduce the switching possibilities (e.g. branch and bound) are useful. However, this paper presents an exhaustive search approach which respects every calculation possibility, while sharing the available resources on the FPGA. The presented implementation is characterized by using the HDL Coder from MathWorks with an automated workflow for implementing a long horizon FCS-MPC with an efficient resource streaming and sharing at the example of a PMSM. The used rapid control prototyping approach avoids manual coding and facilitates the implementation of the algorithm. The benefit of the presented implementation is the use of an application-oriented calculation platform instead of a high-performance solution, which is not useful for the transfer into industrial applications.

High voltage battery storage system for multiuse

Battery storage systems for data centers and telecommunication systems which are available nowadays are merely operated as emergency power systems. During stand-by modus these systems are without any commercial benefit. Furthermore lead-acid battery systems which are usually applied cause enormous additional maintenance costs. Due to the increasing share of volatile renewable energy sources, large energy storage systems are required to ensure the grid stability. This energy storage must be capable to provide short-term balancing power for the grid on demand. To meet the requirements stated above a distributed battery storage system based on lithium iron phosphate (LiFePO4) cells has been developed. This storage system has been designed being able to realize other possible uses in addition to the necessary emergency power supply. However, for all additional applications and use cases the emergency power supply is always prior-ranked. Additional uses are for example the provision of balancing power as a service to the power grid, the increase of internal consumption of self-generated renewable energy (electricity is generated by photovoltaic plants during the day can be consumed by night). Furthermore, the storage system can be used as a charging station for electric vehicles. This multiuse creates a huge economic advantage compared to conventional emergency power supply systems.

Evaluation of Model Based Predictive Control Algorithms for Fractional Horse Power Drives

Model based predictive control is a new promising control method in the field of powerelectronics and electrical drives. The main advantages of MPC are simplicity and intuitiveness of thecontrol method. Constraints and nonlinearities of the system can easily be included, which makes thelinearisation of the system unnecessary. By using MPC it is possible to avoid the cascaded structureof common linear control methods and to gain a fast dynamic performance. A disadvantage is theneed to calculate the optimal actuating variable multiple times in every single sampling cycle leadsto a huge requirement of computational power. So far the computational requirement was the greatestbarrier for the practical application of model based predictive control in the field of power electronicsand electrical drive systems. In addition the small time constants of fractional horse power drivescomplicate the application of predictive control algorithms. In this paper, the feasibility of hardwareimplementation of a cost function based Finite Control Set MPC (FCS-MPC) algorithm for directspeed control of fractional horse power drives is explored. The cost function allows to address variouscontrol goals like dynamics of transitions and energy efficiency – an advantage linear conventionalcontrol methods cannot offer. Hitherto there are very few publications for direct predictive speed. Thepresented approach for direct predictive speed control includes a finite number of possible switchingstates of the converter. This considers the discrete nature of power converters and avoids the need formodulation. The basic principle of the control method is presented and the performance is demonstratedby simulations and experimental results for an industrial brushed type DC-motor.

Evaluation of a new microcontroller based solution for sensorless control of electrical drives

Sensorless field oriented control has always been an area of study with many insecurities, parameter sensitivities and instabilities. In this paper, after giving a short overview of standard sensorless field oriented control algorithms, a new technology by Texas Instruments called “InstaSPIN” will be evaluated. InstaSPIN promises to solve all of the well-known problems of sensorless control as, weak low speed performance, restricted dynamic response and high parameter sensitivity. The performance will be compared with a standard drive based on a 5 kW permanent magnet synchronous machine.