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Use of the D-decomposition technique for gains selection of the Dual Active Bridge converter output voltage regulator DOI:10.15199/48.2019.11.61

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Frequently used power electronics converters are still somehow challenging objects to control. This is not in terms of the control structure selection but rather in terms of the controller gains selection. Gains which guarantee stability of the unit in predefined operation range and also satisfactory dynamic performance. The operation range is to be understood here not only as power or voltage but also as operating temperature or components tolerance. There is a number methods available for calculation of the gains in the continuous and the discrete domains [1, 2]. Nevertheless, the methods relay on numerous assumptions, simplifications and conversions. This sometimes does not reveal look of the complete set of stable solutions. The set from which one can choose intentionally subsets guaranteeing desired dynamic performance at certain stability margin. To overcome such limitation some rather non-standard techniques are to be used. One of them is the D-decomposition method proposed by Russian mathematician Yuri Isaakovich Neimark in 1948 [3]. The technique is relatively easy to use in the era of computers and is a subject to consideration in this article. The method determines asymptotically stable region (or regions if applicable) in space of parameters which can be the controller gains. Additionally, with some modifications it takes into account constrains related to desired phase and gain margins, PM and GM respectively [4]. The D-decomposition technique has been applied to gains selection of the Dual Active Bridge converter, DAB, output voltage PI regulator. The DAB topology, see Fig. 1, is commonly used in the electric power conversion chains where bidirectional power flow is required [5]. Mathematical derivation of the circuit transfer function for the control purpose is not straight forward. The model strongly depends on control scheme applied [6]. Therefore for purpose of this research the transfer function has bee[...]

Dual-Active-Bridge converter inductance DC-bias current compensation under low and high load conditions DOI:10.15199/48.2018.07.01

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Advanced power distribution grids are often considered as smart grids [1]. Generally speaking, such grids rely on various measurements, information exchange by communication means and advanced control actions in order to enable (bidirectional) electric energy flow between energy sources (including renewables and energy storage) and the end user. In addition, the electric energy can be in form of AC and/or DC - this for cost reduction and efficiency reasons [1],[2]. All that together creates challenging system environment in terms of ensuring its safe and stable operation. Such a system creates opportunities for technologies developments which will facilitate its operation. One of such technology area is energy transformation between two different DC voltage levels within a DC-grid. The solution could come with development of a so called Solid State Transformer, SST [3]. The SST concept, Fig.1, is already in use for same time and with certain assumptions could be considered as a mature technology for low voltage applications. It relies on the Dual Active Bridge, DAB, DCDC converter topology [4], Fig. 2. Nevertheless the SST, basing on the DAB, related to medium-to-low DC voltage conversion, Fig. 1, e.g. 10 kV to 380V and power of 1 MW, still calls for attention. Especially in area of its control at all functional levels. The functional levels can be defined as following: 1st) individual DAB converter as a SST Module, SSTM; 2nd) group of DAB converters creating single SST; 3rd) group of SSTs acting inside of a smart grid. In this paper, as the first step towards complete SST, authors concentrate on control of the 1st functional level, namely single DAB converter depicted in Fig. 2. Appropriate control solution must ensure, inter alia, a) steady-state operation of the DAB under light load (below 1% of the rated low voltage output power, 􀜲􀭈􀭅􀭆,􀭐􀭚 􀭰􀭲⤒[...]

Identification of Dual-Active-Bridge converter transfer function DOI:10.15199/48.2019.03.33

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Nowadays electric power conversion circuits are basing on power electronics, measurements and control solutions. All that combined together with widely available data exchange means creates foundation for advanced electric power conversion systems [1]. Such systems are complex and exposed to changing operating conditions. In addition they are quite often safety related. In such case there is a real need for trustworthy solutions for fast and relatively easy transfer function identification of selected power system components (circuits). Knowledge of the transfer function helps to develop tailored control solutions dedicated to the real world circuits [2]. In such case selection of the control mechanism relies on sufficient set of information in given range of the dynamics, without compromise on relevant gains and time constants which may have direct impact on dynamic performance and stability. There is a number of identification methods reported in literature [3], which could be used to identify miscellaneous systems. In this paper we concentrate on one of the fundamental methods basing on analysis in frequency domain [4]. The method is called Frequency Response Analysis, FRA, [3]. The sampled signal analyses are conducted with use of Matlab&Simulink environment. As the identification object the Dual Active Bridge DC/DC converter, DAB, is used [5]. The circuit, see Fig.1, is considered as a promising power electronics building block solution for the solid state transformers, SST, [6, 7]. The SST is one of the key components of the future smart grids. Despite of relatively long circuit existence, since 80’ties, it is still considered as significant challenge in terms of design, mathematical modelling and digital control [6, 8]. In order to simplify the control design of such a circuit the frequency domain transfer function identification method is used to estimate control-to-output transfer function. Basing on the fu[...]

Nieliniowy predykcyjny obserwator prądów dla silników elektrycznych z magnesami trwałymi

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W artykule przedstawiono zagadnienia związane z projektowaniem nieliniowych obserwatorów predykcyjnych prądu dla serwonapędu wyposażonego w silnik synchroniczny z magnesami trwałymi. Po krótkim wprowadzeniu przedstawiono model silnika PMSM i strukturę sterowania. Następnie opisano strukturę obserwatora prądu oraz scharakteryzowano jego właściwości dynamiczne. Kolejno zaproponowano modyfikacje obserwatora zapewniające redukcję błędów estymacji rozwiązania klasycznego. Pierwsza modyfikacja polega na zastosowaniu zmiennych współczynników wzmocnienia realizowanych przez funkcję nieliniową. Drugie rozwiązanie opiera się na zastosowaniu dodatkowego członu rozmytego. Rozważania teoretyczne poparte zostały badaniami symulacyjnymi. Abstract. In the paper issues related to design of the nonlinear predictive current observers for a servodrive system with a permanent magnet synchronous motor are described. After short introduction the mathematical model of the PMSM and the control structure are presented. Next, the structure of the classical current observer is presented and its features are analyzed. Next, two modifications of the classical structure are considered. The first approach relies on adaptation of the observer coefficients. Second framework uses fuzzy logic scheme. Theoretical considerations are supported by simulation study. (Design of the nonlinear predictive current observers for a servodrive system with a permanent magnet synchronous motor) Słowa kluczowe: napęd elektryczny, silnik PMSM, predykcja prądu, logika rozmyta Keywords: electric drives, PMSM motor, current prediction, gain scheduling, fuzzy logic Wstęp Od nowoczesnych serwonapędów oczekuje się osiągania zadanych sygnałów położenia lub prędkości w możliwie krótkim czasie. Żąda się również spełnienia dodatkowych wskaźników jakości regulacji takich jak: braku przeregulowania w położeniu czy minimalizacji zużytej energii. Silniki synchroniczne o magnesach trwałych (PMSM) są po[...]

Constant power operation of a PMSM drive taking into account the stator resistance and the nonlinear inductance

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Efficient field weakening algorithm for the PMSM drive with surface mounted rotor magnets is presented in this paper. Proposed solution has been implemented in a high performance multi-axis servodrive dedicated to the international industrial market. Topic of the PMSM drive control in a constant power region has been discussed in number of publications. Most frequently with neglected stator resistance and magnetic saturation not taken into account. Such assumptions are acceptable in solutions for rather low performance drives operated in the field weakening region. This paper contains details on the proposed solution, a simple example for possible control program sequence and some experimental results. Streszczenie. W tym artykule zaprezentowano wydajny algorytm osłabiania pola silnik[...]

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