Position control is usually achieved using a position controller and a profile generator. The profile generator produces a desired position trajectory from a position reference and predefined profiles. The position controller forces the actual position to trace the generated position trajectory. A time-based profile generator is the most famous profile generator due to its capability of generating various profiles. However, time base difference in analysis and implementation causes a steady-state error. In order to remove the steady-state error, this paper proposes a novel profile generator for a trapezoidal velocity profile generation. The proposed generator is based on a cascaded P-PI position controller which is designed to trace the position reference. A dynamic range limiter is adopted to provide the acceleration and velocity restrictions which are basic functions for generating the trapezoidal profile. In spite of these restrictions, it cannot make a desired velocity profile only using the limiter because deceleration point is inaccurate. To adjust the deceleration point, a feedback compensator is designed which requires the velocity of the deceleration point. The velocity of the deceleration point is estimated from the initial position error. The compensator moves the deceleration point to the appropriate point which can generate the desired velocity profile. The proposed profile generator can remove the steady-state error, and the position response can be easily adjusted to be either overdamped or underdamped by selecting the two gains appropriately. Several experimental results are presented to verify the usefulness of the proposed generator.

This paper proposes an active damping control method to reduce the voltage fluctuation caused by using the reduced DC-link film capacitors instead of the conventional electrolytic capacitors. The motor drive system with the reduced DC-link capacitor has the problem of an unstable DC-link voltage. The ripple of the capacitor voltage is caused by the resonance of both the large input line filter and the reduced DC-link capacitor. To solve this problem, the active damping control method using the d-axis current injection is proposed in this paper. The virtual damping impedance is applied to the equivalent circuit of the system to suppress the voltage ripple of the DC-link. The damping impedance is generated by injecting the DC and AC components into the d-axis current. The relationship between the injected d-axis current and the damping impedance is analyzed through the equational analysis. The proposed method can decrease the DC-link capacitor voltage oscillation and minimize the torque ripple because the injection current is not q-axis but d-axis. The simulation results are presented to prove the validity of the proposed method.

This paper presents a rotation speed estimation and an indirect speed control method for a turbine-generator in a grid-connected 3-phase electrical power conversion system of an organic Rankine cycle (ORC) generation system. In addition to the general configuration mechanism and control techniques that are required in the grid-connected ORC power generation system, the indirect speed control method using the grid-side electric power control and the speed estimation method is proposed for the proper speed control of turbine-generators. The speed estimation method utilizes a digital phase-locked loop (PLL) method that uses a state observer to detect the positive-sequence voltages. A 10 kW system where a Motor-Generator set is used as a turbine simulator and a 23 kW actual system for the grid-connected ORC power generation were designed and manufactured, respectively. This paper includes various experimental results obtained from field tests conducted on actual installed ORC systems.

Advanced Maximum Power Point Tracking Method for the Series Operation Strategy of Grid-Connected Small Wind Turbines Grid connected inverter;MPPT(Maximum Power Point Tracking);Series operation strategy;Wind turbine system; Operating wind turbine generators at maximum power point requires maximum power point tracking (MPPT) control methods. However, conventional methods cannot track the appropriate maximum power point in situations involving wind turbine systems based on a series operation strategy. These systems comprise one or more local maximum power points, and conventional methods can detect only one local maximum power point closed by a current operation point. This study proposes an advanced MPPT method for the series operation strategy of a small, grid-connected wind turbine system. In determining the appropriate maximum point, operations at certain local maximum power points are analyzed. The results show one appropriate point, which is tracked by the proposed MPPT method. The effectiveness of the proposed method is verified by the experimental results.