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Analysis of Estimation Errors in Rotor Position for a Sensorless Control System Using a PMSM
Yongsoon Park,Seung-Ki Sul,Jun-Keun Ji,Young-Jae Park 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.5
In a sensorless control system with a Permanent Magnet Synchronous Motor (PMSM), the angular position of the rotor flux can be estimated by a voltage equation. However, the estimated angle may be inaccurate due to various causes. In this paper, it was comprehensively analyzed how various causes affect the angle error. As a result of the analysis, an error equation intuitively describing these relationships was derived. The parameter errors of a PMSM and the non-ideal properties of the driving system were identified as error-causing factors. To demonstrate the validity of the error equation, PMSMs were tested at various operating points. The variations in angle errors could be well explained with the error equation.
Phase-Locked Loop Based on an Observer for Grid Synchronization
Yongsoon Park,Seung-Ki Sul,Woo-Chull Kim,Hyun-Young Lee IEEE 2014 IEEE transactions on industry applications Vol.50 No.2
<P>A grid synchronization technique is essential for grid-connected power converters. Phase-locked loop (PLL) has been widely exploited as an implementation technique, but additional efforts are required to deal with severely distorted grid voltages. In this paper, an observer is proposed to enhance the performance of PLL. A state equation is newly formulated to construct the observer, which extracts positive-sequence voltage from the distorted grid voltage. Additionally, guidelines are suggested to set the observer gains by considering its internal transfer functions. The PLL and proposed observer have been tested in simulations and experiments in contrast to dual second-order generalized integrator frequency-locked loop. The results have shown that the proposed method reveals a better phase-tracking performance for grid synchronization.</P>
Frequency Adaptive Observer to Extract AC-Coupled Signals for Grid Synchronization
Yongsoon Park,Hyeon-Sik Kim,Seung-Ki Sul 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
For three-phase three-wire grid, a method to synchronize the converter to the grid voltage, which was distorted by low-order harmonics and unbalances, has been widely described. In addition to filtering them, the DC rejection can be achieved together with a frequency adaptive observer in order to eliminate DC bias in the voltage. The state equation for the observer is newly established, and the observer gains are examined in terms of their influences to the performance. The effectiveness of the proposed method is verified with simulations and experiments.
Double-Delta Sourced Winding for Dual Winding Induction Machine
Yongsoon Park,Jeong-Mock Yoo,Seung-Ki Sul 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The harmonic distortions of motor currents can be mitigated by the application of the double-delta sourced winding (DDSW), which implements multi-level operation with two-level converters. In practice, dual winding induction machine (DWIM) has been considered for this application due to its inherent compatibility to DDSW. The modeling of DWIM is discussed for the vector control, and a decoupling control method of each winding to the other is proposed to improve the dynamic response of the current regulation. The torque control is also discussed for the case where one of the converters is dropped out. The effectiveness of the proposed methods is assessed with experimental results. It has been confirmed that the total harmonic distortion of the converter currents was decreased by 67.7 % when DDSW was applied to an 11 kW DWIM. In addition, the bandwidth of the current regulation could be increased by 113.7 % thanks to the proposed decoupling control method.
A Novel Method to Compensate Non-Linearity of Inverter in Sensorless Operation of PMSM
Yongsoon Park,Seung-Ki Sul 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
The non-linearity of an inverter can be modeled as the distorted voltages. A novel method utilizing the trapezoidal voltages is proposed to cancel out the distorted voltages by the non-linearity. By modulating the shape of the trapezoid, the harmonic distortions in the output currents and the voltage references can be reduced. An integral controller is employed to modulate the trapezoid with simple signal processing. To evaluate the effectiveness of the propose method, the conventional methods are compared through the experimental results.
Implementation Schemes to Compensate for Inverter Nonlinearity Based on Trapezoidal Voltage
Yongsoon Park,Seung-Ki Sul IEEE 2014 IEEE transactions on industry applications Vol.50 No.2
<P>Trapezoidal voltages can be used to compensate for the inverter nonlinearity. In particular, the modulating shape of these voltages facilitates the adaptation of the compensation to various operating conditions. In this paper, practical implementation schemes are proposed to improve the performance of the compensation method based on the trapezoidal voltage. After the implementation schemes are detailed, their effectiveness is discussed with experimental results. It has been proved that the proposed schemes are useful for the robust compensation.</P>
A Resiliency Coordinator Against Malicious Attacks for Cyber-Physical Systems
Yongsoon Eun,Jaegeun Park,Yechan Jeong,Daehoon Kim,Kyung-Joon Park 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
Resiliency of cyber-physical systems (CPSs) against malicious attacks has been a topic of active research in the past decade due to widely recognized importance. Resilient CPS is capable of tolerating some attacks, operating at a reduced capacity with core functions maintained, and failing gracefully to avoid any catastrophic consequences. Existing work includes an architecture for hierarchical control systems, which is a subset of CPS with wide applicability, that is tailored for resiliency. Namely, the architecture consists of local, network and supervision layers and features such as simplex structure, resource isolation by hypervisors, redundant sensors/actuators, and software defined network capabilities. Existing work also includes methods of ensuring a level of resiliency at each one of the layers, respectively. However, for a holistic system level resiliency, individual methods at each layers must be coordinated in their deployment because all three layers interact for the operation of CPS. For this purpose, a resiliency coordinator for CPS is proposed in this work. The resiliency coordinator is the interconnection of central resiliency coordinator in the supervision layer, network resiliency coordinator in the network layer, and finally, local resiliency coordinators in multiple physical systems that compose the physical layer. We show, by examples, the operation of the resiliency coordinator and illustrate that RC accomplishes a level of attack resiliency greater than the sum of resiliency at each one of the layers separately.