• Title, Summary, Keyword: SoC error elimination

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Elimination of the State-of-Charge Errors for Distributed Battery Energy Storage Devices in Islanded Droop-controlled Microgrids

  • Wang, Weixin;Wu, Fengjiang;Zhao, Ke;Sun, Li;Duan, Jiandong;Sun, Dongyang
    • Journal of Power Electronics
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    • v.15 no.4
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    • pp.1105-1118
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    • 2015
  • Battery energy storage devices (ESDs) have become more and more commonplace to maintain the stability of islanded power systems. Considering the limitation in inverter capacity and the requirement of flexibility in the ESD, the droop control was implemented in paralleled ESDs for higher capacity and autonomous operation. Under the conventional droop control, state-of-charge (SoC) errors between paralleled ESDs is inevitable in the discharging operation. Thus, some ESDs cease operation earlier than expected. This paper proposes an adaptive accelerating parameter to improve the performance of the SoC error eliminating droop controller under the constraints of a microgrid. The SoC of a battery ESD is employed in the active power droop coefficient, which could eliminate the SoC error during the discharging process. In addition, to expedite the process of SoC error elimination, an adaptive accelerating parameter is dedicated to weaken the adverse effect of the constraints due to the requirement of the system running. Moreover, the stability and feasibility of the proposed control strategy are confirmed by small-signal analysis. The effectiveness of the control scheme is validated by simulation and experiment results.

Compiler triggered C level error check (컴파일러에 의한 C레벨 에러 체크)

  • Zheng, Zhiwen;Youn, Jong-Hee M.;Lee, Jong-Won;Paek, Yun-Heung
    • The KIPS Transactions:PartA
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    • v.18A no.3
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    • pp.109-114
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    • 2011
  • We describe a technique for automatically proving compiler optimizations sound, meaning that their transformations are always semantics-preserving. As is well known, IR (Intermediate Representation) optimization is an important step in a compiler backend. But unfortunately, it is difficult to detect and debug the IR optimization errors for compiler developers. So, we introduce a C level error check system for detecting the correctness of these IR transformation techniques. In our system, we first create an IR-to-C converter to translate IR to C code before and after each compiler optimization phase, respectively, since our technique is based on the Memory Comparison-based Clone(MeCC) detector which is a tool of detecting semantic equivalency in C level. MeCC accepts only C codes as its input and it uses a path-sensitive semantic-based static analyzer to estimate the memory states at exit point of each procedure, and compares memory states to determine whether the procedures are equal or not. But MeCC cannot guarantee two semantic-equivalency codes always have 100% similarity or two codes with different semantics does not get the result of 100% similarity. To increase the reliability of the results, we describe a technique which comprises how to generate C codes in IR-to-C transformation phase and how to send the optimization information to MeCC to avoid the occurrence of these unexpected problems. Our methodology is illustrated by three familiar optimizations, dead code elimination, instruction scheduling and common sub-expression elimination and our experimental results show that the C level error check system is highly reliable.

A Basic Study on Control Algorithm for Car HVAC (승용차 공기조화 제어 알고리즘 기초연구)

  • Shin, Young-Gy
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.5
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    • pp.275-281
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    • 2010
  • Car HVAC is one of main factors influencing a potential customer's first impression. It should be fault-free, which requires the most stable control performance. So, the control algorithm consists of a proportional feedback only, not with an integral action needed for elimination of steady-state errors. To reduce the errors and make the response faster, feedforward algorithm based on predicted thermal load is added. To evaluate the performance, car HVAC is dynamically modelled and its control logic is simulated. The results shows that the proportional feedback leads to about $4^{\circ}C$ of steady-state error. When the feedback is combined with the feedforward algorithm and with a set value update based on disturbances, it predicts less than $1^{\circ}C$ of control error and improved thermal comfort.

Real-Time Forward Kinematics of the 6-6 Stewart Platform with One Extra Linear Sensor (한 개의 선형 여유센서를 갖는 스튜어트 플랫폼의 실시간 순기구학)

  • Lee, Tae-Young;Shim, Jae-Kyung
    • Proceedings of the KSME Conference
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    • pp.541-547
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    • 2000
  • This paper presents the closed-form forward kinematics of the 6-6 Stewart platform of planar base and moving platform. Based on algebraic elimination method and with one extra linear sensor, it first derives an 8th-degree univariate equation and then finds tentative solution sets out of which the actual solution is to be selected. In order to provide more exact solution despite the error between measured sensor value and the theoretical one, a correction method is also used. The overall procedure requires so little computation time that it can be efficiently used for realtime applications. In addition, unlike the iterative schemes e.g. Newton-Raphson, the algorithm does not require initial estimates of solution and is free of the problems that it does not converge to actual solution within limited time. The presented method has been implemented in C language and a numerical example is given to confirm the effectiveness and accuracy of the developed algorithm.

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Real-Time Forward Kinematics of the 6-6 Stewart Platform with One Extra Linear Sensor (한 개의 선형 여유센서를 갖는 스튜어트 플랫폼의 실시간 순기구학)

  • Sim, Jae-Gyeong;Lee, Tae-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.9
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    • pp.1384-1390
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    • 2001
  • This paper deals with the forward kinematics of the 6-6 Stewart platform of planar base and moving platform using one extra linear sensor. Based on algebraic elimination method, it first derives an 8th-degree univariate equation and then finds tentative solution sets out of which the actual solution is to be selected. In order to provide more exact solution despite the error between measured sensor value and the theoretic alone, a correction method is also used in this paper. The overall procedure requires so little computation time that it can be efficiently used for real-time applications. In addition, unlike the iterative scheme e.g. Newton-Raphson, the algorithm does not require initial estimates of solution and is free of the problems that it does not converge to actual solution within limited time. The presented method has been implemented in C language and a numerical example is given to confirm the effectiveness and accuracy of the developed algorithm.