Sliding-Mode Observer Based Voltage-Sensorless Model Predictive Power Control of PWM Rectifier under Unbalanced Grid Conditions

© 1982-2012 IEEE. A sliding-mode grid voltage observer (SMGVO) is proposed and experimentally verified in this paper for voltage-sensorless operation under an unbalanced network. The fundamental positive sequence component (FPSC) and fundamental negative sequence component (FNSC) are inherently separated in the observer without employing any additional filters. Due to embedded filtering effect, high frequency chattering and harmonic ripples can be well suppressed. Additionally, dc components can be completely rejected. As a result, dc offset would not cause fundamental frequency oscillations in magnitude and frequency of the estimated FPSC and FNSC. Owing to the predictive ability of SMGVO, one-step delay can be directly compensated using state variables in the observer. By combining estimation and prediction into one stage, the designed SMGVO turns out to be a compact solution for finite-control-set model predictive power control without voltage sensors. Theoretical proof is derived to verify that FPSC and FNSC can be accurately estimated and separated. Experimental results obtained from a two-level PWM rectifier confirm the effectiveness of the whole control system

Design and control of a novel uninterrupted dual input powertrain system for electric vehicles

University of Technology Sydney. Faculty of Engineering and Information Technology.The automotive powertrain is one of the most important subsystems of any vehicle whose major function is to convert the stored energy to kinetic energy and deliver it as tractive load to the road. In order to reduce the harmful emissions and the dependence on fossil fuels, the development. The new technology will improve the overall efficiency, the drivability and the driving comfort, and reduce the tailpipe emissions. However, the inclusion of electric machines alone does not guarantee these improvements, proper transmission structure design and adequate control strategy should be designed to fully exploit the potential of the whole system, thereby maximizing the benefits to end users. In order to achieve the aforesaid benefits of electric vehicle, a novel dual input clutchless transmission configuration is proposed which consists of an automated manual transmission (AMT) and a fixed gear pair. It has the merits of low manufacturing cost, robustness and easy implementation. With the proposed gear shift control strategy, the novel configuration could eliminate the torque interruption of conventional AMT systems, improving the drivability and driving comfort. To fully exploit the efficiency improvements of the proposed system, a real time power sharing control strategy is proposed to balance the load distribution between the two motors. By adequately choosing the gear position and distributing the power demand, the overall efficiency could be improved by more than 10%. The proposed power sharing strategy has the disadvantage encountered by many other energy-oriented energy management strategies which is high gear shifting frequency. To keep a high overall efficiency and at the same time significantly reduce the shift frequency, a shifting stabilizer is proposed and embedded in to the control strategy. At last, a modified hybrid configuration based on the proposed concept is developed for mining trucks. The hybrid system could satisfy the specific requirements of mining trucks and present high overall efficiency and drivability. To evaluate the effectiveness of the proposed approaches, various detail mathematical models have been built and tested in sets of driving conditions which could reflect the practical implementations

Analysis of direct power control AC-DC converter under unbalance voltage supply for steady-state and dynamic response

This paper presents an analysis of Direct Power Control (DPC) technique for the Three-Phase Pulse Width Modulation (PWM) AC-DC converter under unbalanced supply condition. Unbalance condition will cause the presence of unbalanced current and voltages thus produce the negative components on the grid voltage as well as severe performance degradation of a grid connected Voltage Source Inverter (VSI). The input structures for conventional DPC has been modified with a three simpler sequence networks instead of coupled by a detailed Three-Phase system method. The imbalance voltage can be resolved by separating from the individual elements of voltage and current into symmetrical components called Sequence Network. Consequently, the input power relatively improved during unbalanced condition almost 70% through the measurement of Total Harmonic Distortion (THD) from the conventional Direct Power Control (DPC) in individual elements which is higher compared to separate components. Hence, several analyses are performed in order to analyze the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations

Improved DC-Link Voltage Regulation Strategy for Grid-Connected Converters

In this article, an improved dc-link voltage regulation strategy is proposed for grid-connected converters applied in dc microgrids. For the inner loop of the grid-connected converter, a voltage modulated direct power control is employed to obtain two second-order linear time-invariant systems, which guarantees that the closed-loop system is globally exponentially stable. For the outer loop, a sliding mode control strategy with a load current sensor is employed to maintain a constant dc-link voltage even in the presence of constant power loads at the dc-side, which adversely affect the system stability. Furthermore, an observer for the dc-link current is designed to remove the dc current sensor at the same time improving the reliability and decreasing the cost. From both simulation and experimental results obtained from a 15-kVA prototype setup, the proposed method is demonstrated to improve the transient performance of the system and has robustness properties to handle parameter mismatches compared with the input-output linearization method

Finite Control Set Model Predictive Control for an LCL-Filtered Grid-Tied Inverter with Full Status Estimations under Unbalanced Grid Voltage

This paper proposes a novel finite control set model predictive control (FCS-MPC) strategy with merely grid-injected current sensors for an inductance-capacitance-inductance (LCL)-filtered grid-tied inverter, which can obtain a sinusoidal grid-injected current whether three-phase grid voltages are balanced or not. Compared with the conventional FCS-MPC method, four compositions are added in the proposed FCS-MPC algorithm, where the grid voltage observer (GVO) and Luenberger observer are combined together to achieve full status estimations (including grid voltage, capacitor voltage, inverter-side current, and grid-injected current), while the sequence extractor and the reference generator are applied to eliminate the double frequency ripples of the active or reactive power, or the negative sequence component (NSC) of the grid-injected current caused by the unbalanced grid voltage. Simulation model and experimental platform are established to verify the effectiveness of the proposed FCS-MPC strategy, with full status estimations under both balanced and unbalanced grid voltage conditions