• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.3
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• pp.154-161
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• 2005

This paper proposes a speed-sensorless induction motor control system using a rotor speed compensation. To explain the proposed system, this paper describes an induction motor model in the synchronous reference frame for the vector control. The rotor flux is estimated by the rotor flux observer using the reduced-dimensional state estimator technique. The estimated rotor speed is directly obtained from the electrical frequency, the slip frequency, and the rotor speed compensation with the estimated q-axis rotor flux. The error of the rotor time constant is indirectly reflected in the rotor speed compensation using the compensation of the flux error angle. To precisely estimate the rotor flux, the actual value of the stator resistance, whose actual variation is reflected, is derived. An implementation of pulse-width modulation (PWM) pulses using an effective space vector modulation (SVM) is briefly mentioned. For fast calculation and improved performance of the proposed algorithm, all control functions are implemented in software using a digital signal processor (DSP) with its environmental circuits. Also, it is shown through experimental results that the proposed system gives good performance for the speed-sensorless induction motor control.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1137-1145
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• 2017

This paper proposes the dead time effect compensation algorithm using proportional resonant controller in pulse width modulation inverter of motor drive. To avoid a short circuit in the dc link, the dead time of the switch device is surely required. However, the dead time effect causes the phase current distortions, torque pulsations, and degradations of control performance. To solve these problems, the output current including ripple components on the synchronous reference frame and stationary reference frame are analyzed in detail. As a results, the distorted synchronous d-and q-axis currents contain the 6th, 12th, and the higher harmonic components due to the influence of dead time effect. In this paper, a new dead time effect compensation algorithm using proportional resonant controller is also proposed to reduce the output current harmonics due to the dead time and nonlinear characteristics of the switching devices. The proposed compensation algorithm does not require any additional hardware and the offline experimental measurements. The experimental results are presented to demonstrate the effectiveness of the proposed dead time effect compensation algorithm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.35-43
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• 2011

In this paper, an analysis on I/Q mismatch characteristics of a quadrature LC VCO(Voltage controlled oscillator) is presented. Based on this analysis, a new I/Q mismatch compensator is proposed. The proposed I/Q mismatch compensator utilizes an amplitude mismatch detector rather than the conventional phase mismatch detector requiring much more wide frequency bandwidth. To verify the proposed circuit, a 2.5GHz quadrature LC VCO was designed in a $0.18{\mu}m$ CMOS process and tested. Test results show that an amplitude mismatch detector achieves similar I/Q mismatch compensation performance as that of the conventional phase mismatch detector. The I/Q mismatch compensator consumes 0.4mA from 1.8V supply voltage and occupies $0.04mm^2$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.50-55
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• 2021

Multi-path system is a system in which utilizes various networks simultaneously. It is expected that multi-path system can enhance communication speed, reliability, security of network. In this paper, we focus on path selection in multi-path system. To select optimal path, we propose deep reinforcement learning algorithm which is rewarded by the round-trip-time (RTT) of each networks. Unlike multi-armed bandit model, deep Q learning is applied to consider rapidly changing situations. Due to the delay of RTT data, we also suggest compensation algorithm of the delayed reward. Moreover, we implement testbed learning server to evaluate the performance of proposed algorithm. The learning server contains distributed database and tensorflow module to efficiently operate deep learning algorithm. By means of simulation, we showed that the proposed algorithm has better performance than lowest RTT about 20%.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.517-523
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• 2002

A sensorless control of a PM synchronous motor with the compensation of the motor parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and motor model of the position estimator. The stator resistance is measured at low speeds when the motor changes its rotating direction and the variation of the stator resistance and back emf constant caused by the temperature variation is compensated. The gains in the position estimator are also adapted according to the motor speeds.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1310-1319
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• 2013

Resolvers are transducers that are used to sense the angular position of rotational machines. The analog resolver is necessary to use resolver to digital converter. Among the RDC software method, angle tracking observer (ATO) is the most popular method. In an actual resolver-based position sensing system, amplitude imbalance dominantly distorts the estimate position information of ATO. Minority papers have reported position error compensation of resolver's output signal with amplitude imbalance. This paper proposes new ATO algorithm in order to compensate position errors caused by the amplitude imbalance. There is no need premeasured off line data. This is easy, simple, cost-effective, and able to work on line compensation. To verify feasibility of the proposed algorithm, simulation and experiments are carried out.

• Journal of Power Electronics
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• v.13 no.1
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• pp.77-85
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• 2013

This paper proposes a new dead time compensation method of independent six-phase permanent magnet synchronous motors (IS-PMSM). The current of the independent phase machines contains odd-numbered harmonics because of the dead time and the nonlinear characteristics of the switching devices. By using the d-q-n three-dimensional vector analysis, these harmonics can be extracted at the n-axis current. Thus, the current distortion can be compensated by controlling the n-axis current of the IS-PMSM to zero. The proposed method is simple and can be easily implemented without additional hardware setup. The validity of the proposed compensation method is verified with simulations and several experiments.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.72-77
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• 2022

Among the techniques of reinforcement learning, Q-Learning means learning optimal policies by learning Q functions that perform actionsin a given state and predict future efficient expectations. Q-Learning is widely used as a basic algorithm for reinforcement learning. In this paper, we studied the effectiveness of selecting and learning efficient paths by designing policies and rewards based on Q-Learning. In addition, the results of the existing algorithm and punishment compensation policy and the proposed punishment reinforcement policy were compared by applying the same number of times of learning to the 8x8 grid environment of the Frozen Lake game. Through this comparison, it was analyzed that the Q-Learning punishment reinforcement policy proposed in this paper can significantly increase the learning speed compared to the application of conventional algorithms.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.6
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• pp.445-454
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• 2002

Torque ripple control of brushless DC motors has been the persisting issue of the servo drive systems in which the speed fluctuation, vibration and acoustic noise should be minimized. In this paper, a novel approach to achieve the ripple-free torque control with maximum efficiency based on the d-q reference frame is presented and analyzed. The proposed approach can provide the optimized phase current waveforms over wide speed range incorporating cogging torque compensation without an access to the neutral point of the motor windings. Moreover, the undesirable errors caused by the assumptions such as 3 phase balance or symmetry of the phase back EMF between electrical cycles, which are related with the manufacturing imperfections, can be also eliminated. As a result, the proposed approach provides a simple and clear way to obtain the optimal motor excitation currents. A hysteresis current control system is employed to produce high-frequency electromagnetic torque ripples for compensation. The validity and applicability of the proposed control scheme to real situations are verified through the simulations and experimental results.

• Journal of Wind Energy
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• v.9 no.4
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• pp.47-56
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• 2018

This paper introduces an active power dependent standard characteristic curve, Q(P) to compensate for voltage variations due to the output of distributed generation. This paper presents an efficient control method of grid-connected inverters by comparing and analyzing voltage variation magnitude and line loss according to the compensation method. Voltage variations are caused not only by active power, but also by the change of reactive power flowing in the line. In particular, the system is in a relatively remote place in a coastal area compared with existing power plants, so it is relatively weak and may not be suitable for voltage control. So, since it is very important to keep the voltage below the normal voltage limit within the specified inverter capacity and to minimize line loss due to the reactive power. we describe the active power dependent standard characteristic curve, Q(P) method and verify the magnitude of voltage variation by simulation. Finally, the characteristics of each control method and line loss are compared and analyzed.