electronica 2014: Messeneuheiten rund ums Auto und Elektromobilität

Design & Implementation of Parallel Operation of Inverters with Instantaneous Current Sharing Scheme Using Multiloop Control Strategy on FPGA Platform by Shahil Shah -Department of Electrical Engineering Indian Institute of Technology, Kanpur

Abstract
 In these days of acute shortage of conventional energy resources, the harness of renewable energy has received considerable attention. In general, power obtained from Renewable Energy Sources(RES) is not of the form which is directly deliverable to the AC load or the utility grid. Voltage Controlled Voltage Source Inverters (VCVSI) forms the interface link which conditions power to the form deliverable to grid or load. To modularize the system, instead of a single inverter, the use of number of parallel inverters of reduced rating is proposed. The parallel operation of inverters in RES system o ers advantages like reliability and redundancy in addition to the low maintenance cost of a low power unit compared to that of high power unit. However there is a need of control strategy to strictly hold the amplitude, phase and frequency of output voltages of inverters at the same values in order to avoid circulating currents through inverter modules and make them share load currents equally even during transients. In this thesis work a control scheme is proposed and implemented for paralleling of three phase inverters which enables the inverters to share load currents equally even during transients (instantaneous current sharing), and also track the sinusoidal voltage reference. This voltage reference is either free running or is derived from grid voltage so as to feed AC load or to synchronize the module with any utility grid. The design issues for designing of multiloop control structure are analyzed at length with the discussion of active damping to increase the damping and relative stability of system. Design of outer current sharing controller has been done and its design intricacies are included in the work. FPGAs can be used to control power electronic systems. They have advantages like high speed, parallel processing capability, and rich digital I/O interface. In this thesis, basic modules required for development of controllers for power electronic systems are developed and tested with standard signals. The proposed control scheme for parallel operation is implemented for two 3-phase inverters using this FPGA platform.
 LINK ORIGINAL

http://shahilshah.weebly.com/uploads/4/4/6/5/4465384/shahil_report.pdf

David Perreault - Powerful Circuits: Developments in High Frequency Power Electronics

  Powerful Circuits: Developments in High Frequency Power Electronics Electrical energy is the cornerstone of our technological infrastructure, and its use pervades our society. Energy-processing circuits -- or power electronics -- are central to our ability to efficiently create, manipulate, and utilize electrical energy. Advances in this area are becoming vital, both for addressing the growing energy challenges we face and for extending our control over the world around us. A challenge of particular importance is the miniaturization of power circuits. Likewise, advances in the performance of power electronics -- including efficiency, control bandwidth, and operating range -- are essential to reducing energy consumption and increasing functionality in myriad applications.
 This talk describes ongoing research at MIT that seeks to address the twin challenges of miniaturization and performance of power electronics. New system architectures and circuit designs are introduced that enable dramatic increases in switching frequencies (e.g., into the 3-300 MHz range). Higher frequencies are desirable because they reduce energy storage requirements, but necessitate circuit designs that either compensate for or utilize device parasitics. Furthermore, design approaches for integrated power devices and magnetics are introduced that scale well to small sizes and high frequencies and enable improved integration. Experimental results from power converters operating at frequencies to beyond 100 MHz are presented to illustrate these emerging technologies.

DSP-Based Control for Parallelism of Three-Phase Voltage Source Inverter Telles B. Lazzarin, Member, IEEE, and Ivo Barbi, Fellow, IEEE Power Electronics Institute (INEP), Department of the Electrical Engineering (EEL), Federal University of Santa Catarina (UFSC), Florianópolis , Brazil

Abstract—This paper describes a theoretical and experimental study on a control strategy for the parallel operation of three-phase voltage source inverters (VSI), to be applied to UPS. The proposed control system for each inverter consists of two main loops, which both use instantaneous values. The first (parallelism control) employs the feedback of the inductor currents from the output filter to modify the input voltages of the same filter and thereby control the power flow of each VSI to the load. Additionally, the second loop (voltage control) is responsible for controlling the output voltages of the LC filter, which coincides with the output voltages of the VSI. The proposed control strategy ensures the proper sharing of the load current and avoids current circulation among the inverters during transient and steady-state operation. The VSI and the proposed control strategy are analyzed in an orthogonal stationary frame, and as a result, simple and effective models were achieved. The proposed control system was digitally implemented in a TMS320F2812 DSP and was verified through experimental results with a 10 kVA prototype, which has the parallel operation of two three-phase VSIs.

II. INTRODUCTION
 ININTERRUPTIBLE power supply (UPS) devices are employed to feed critical loads which, at high power values, utilize a three-phase system. Moreover, inmany applications the total load consists of a set of single and three-phase loads, which requires the employment of three-phase UPS, capable of feeding all types of load. In addition, critical loads also require a power supplywith high-reliability and redundancy that can be obtained with the parallel-connection ofUPSs.As iswell-known, the parallelism of UPS is a problem related to the parallel operation of voltage source inverters (VSIs). The parallel operation of three-phase VSIs has a greater complication due to the complexity and the greater number of variables involved in a three-phase system. Recent publications in the literature [1]–[3] broach this problem and they point out that there is still a need for new solutions to the parallelism of three-phase VSIs. It is also well-known that the parallel operation of VSIs requires a control system to ensure proper operation of the structure. A traditional solution is the strategy based on the frequency and voltage droop [4]–[18]. This strategy controls the average active and reactive power flow from the VSI to the load and it does not require communication among the inverters. It provides increased reliability and redundancy but it has errors associated with load sharing, poor transient response, reduced voltage regulation and it does not control the division of the harmonic currents [1], [3]. In the literature there are interesting studies reported [8], [9], [11], [18]–[22] which minimize the disadvantages, in most cases addressing single-phase systems. On the other hand, there are strategies related to communication, such as central control [23]–[25], master-slave control [26]–[29] and distributed control [2], [3], [30], [25]. These strategies are most effective in terms of load sharing, but high reliability and redundancy are not available due to the communication between units. In recent years, these strategies have been based on the instantaneous current control [2], [3], [24], [34], [35], in which the parallelism control receives information on the instantaneous current supplied by all units. Good transient response and the appropriate load sharing among VSIs, including the harmonics of load current, are advantages introduced by instantaneous control. The evolution of these strategies is associated with the use of microcontrollers, DSP and FPGA in power converters [36]–[44]. The digital control provides the means to propose new solutions to complex problems as in the parallel operation of three-phase voltage inverters. In this context, this paper proposes a distributed control strategy for the parallel operation of three-phase VSIs. Each VSI has its own control unit, responsible for regulating the output voltages and ensuring its parallel operation.

A Master and Slave Control Strategy for Parallel Operation of Three-Phase UPS Systems with Different Ratings Woo-Cheol Lee, Taeck-Ki Lee Sang-Hoon Lee, Kyung-Hwan Kim, Dong-Seok Hyun In-Young Suh-Department of Electrical Engineering HanKyong National University-Seoul, Korea