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Nowadays, zero-emission electric vehicles become more and more attractive personnel transport vehicles for mining industry. Owing to the special working environment and complex road conditions, a robust controller needs to be designed to achieve a stable and reliable vehicle system for underground mining electric vehicles (UMEVs). This paper first presents the UMEV model with system uncertainties. Then, a new controller based on the sliding mode control (SMC) is designed for UMEVs to track the longitudinal velocity while maintaining longitudinal slip ratio in a desired linear region in the presence of the bounded system uncertainties. The comparison of the simulation results for both the proposed SMC controller and a traditional SMC controller shows that the proposed SMC controller has a better performance for the long-distance up/down slopes with varying rolling resistance coefficients.

Comparing with conventional charging algorithm of constant current and constant voltage (CC/CV) for lithium ion batteries, many charging algorithms are proposed to improve charging time, charging efficiency and cycle life. However, the comparisons were conducted only between the charging algorithms and the CC/CV for different lithium ion batteries. In this paper, a new testing platform based on LabVIEW is developed to investigate various charging algorithms under the same battery with similar testing conditions, where the platform includes programmable power supply and electronic load. The experimental results of battery voltage, current and temperature are sampled to calculate the ampere hour and energy efficiencies and the times for charging up to 50%, 80% and 100% of normal capacity. The maximum temperature difference for all the charging algorithms during an entire charging period is less than 3 degree which indicates that all charging algorithms have similar effect on battery cycle life to the CC/CV.

This paper investigates the influence of electric vehicles (EVs) and renewable energy sources (RESs) on the cost and emission of electricity. Based on the data collected from Melbourne in Australia, the power system with EVs and the power system with both EVs and RESs have been simulated to compare with conventional power systems in terms of the cost and emission of electricity. The simulation results show that the integration of both EVs and RESs into the power system can reduce the cost and emission of electricity by intelligently managing the timings of charging/discharging EV batteries from/to the grid.

This paper presents the overview of charging algorithms for lithium-ion batteries, which include constant current-constant voltage (CC/CV), variants of the CC/CV, multistage constant current, pulse current and pulse voltage. The CC/CV charging algorithm is well developed and widely adopted in charging lithium-ion batteries. It is used as a benchmark to compare with other charging algorithms in terms of the charging time, the charging efficiency, the influences on battery life and other aspects, which can serve as a convenient reference for future work in developing a charger for lithium-ion battery.

A well-known Luenburger observer and two sliding mode observers (SMO) for battery state of charge (SOC) estimation based on an improved battery equivalent circuit are presented. The comparison of their SOC estimation results is discussed. The testing data under different discharge current profiles generated by DUALFOIL battery simulation program are used to extract the circuit model parameters and verify the effectiveness of the observers for the SOC estimation. It shows that two sliding mode based SOC observers have robust tracking performance and provide more accurate SOC estimation in electric vehicle driving conditions.

In this paper, the mathematical modelling of a front-wheel steer-by-wire (SBW) system is studied and a terminal sliding mode control scheme for the SBW system with uncertain dynamics is developed. It is shown that a front-wheel SBW system, from the hand-wheel to the steered front wheels, is equivalent to a second-order system. A terminal sliding mode controller can then be designed based on the information of the bounds of uncertain system dynamics, in the sense that not only a strong robustness with respect to system uncertainties and nonlinearities can be obtained, but also the front wheel steering angle can converge to the hand-wheel reference angle in a finite time. A simulation example is presented to verify the proposed control scheme.

A photovoltaic (PV) system consists of many solar panels, which are connected in series, parallel or a combination of both. Energy production for the PV system with various configurations is different. In this paper, a methodology is developed to evaluate and analyze the expected energy production of the PV system for feasible configurations.

Wind energy has been receiving more acceptance as a reproducible, resourceful and clean energy source since last decade. Wind power is not constant and can fluctuate below the rated wind power when the wind speeds are lower than the rated wind speed. This fact affects the grid the wind generators are connected to, which is becoming more significant with the increasing penetration of wind energy systems. Pitch angle control has been one of the most common methods for smoothing output power fluctuations during below rated wind incidents. In this paper, two methods of fuzzy logic system have been proposed for the pitch angle controller: the determination of the command output power based on Exponential Moving Average (EMA) with a proper selection of correction factor by fuzzy reasoning and the dynamic selections of target output power according to the current wind incident. Simulation results show the effectiveness of the proposed methods in smoothing wind power fluctuations with significantly small drop of output power.

This paper poses and solves a new problem of consensus control where the task is to make the fixed-topology multi-agent network, with each agent described by an uncertain nonlinear system in chained form, to reach consensus in a fast finite time. Our development starts with a set of new sliding mode surfaces. It is proven that, on these sliding mode surfaces, consensus can be achieved if the communication graph has the proposed directed spanning tree. Next, we introduce the multi-surface sliding mode control to drive the sliding variables to the sliding mode surfaces in a fast finite time. The control Lyapunov function for fast finite time stability, motivated by the fast terminal sliding mode control, is used to prove the reachability of the sliding mode surface. A recursive design procedure is provided, which guarantees the boundedness of the control input.

As VLSI technology scales into sub-65nm realm, the complexity of timing optimization is drastically increased by the consideration of power and variations. Even though designers make great efforts during physical design, they are often faced with still heavy timing violations in deep post-routing stages. For the entire design convergence and timing closure, especially under current multi-corner multi-mode design, some more efficient methods need to be invented. In this work, we propose to address such a kind of issue by exploiting useful clock skew, which can help reduce timing violations rapidly. We also add mode/corner metric balancing measurements to make this method more flexible and applicable especially in such deep stages while the CTS is ready. The results indicate that our method can achieve an average improvements of 33.16% on the worst slack (WS) and 75.56% on the total negative slack (TNS), respectively.

This paper presents a new approach of maximizing energy harvesting in photovoltaic (PV) systems using bisection search theorem (BST). The fundamental of the BST and its application into maximum power point tracker (MPPT) in PV systems are described. A microcontroller is used to control a DC/DC boost converter to realize the MPPT function. Experimental results from solar array simulator show that the proposed technique can track maximum power point very fast within a few steps. The feasibility of the proposed MPPT is also verified in natural environment condition with two solar modules in parallel. Since the proposed technique is simple in computation, cheap in implementation and fast in tracking, it is expected to be widely used to replace conventional MPPT techniques in PV systems.

This paper presents a new mathematical model of a solar module. Solar module temperature, solar radiation and its effect on series resistance are taken into account in the model. The experimental data of the solar module under natural environment condition have been obtained to determine the model parameters. Then, the developed model is used to simulate energy yield of the solar module. This energy yield is compared with those obtained from experimental data and conventional approach. The results indicate that the proposed approach can have more accurate energy yield than conventional approach. Thus, it can be useful for the design of PV systems.

With decreasing of feature size of VLSI designs, clock buffers are becoming quite huge. However, buffers often can't be placed at ideal places because that traditionally clock network construction is performed after place-ment and at this time all cells are fixed. As a result, wire length and buffer numbers of clock net are increased. In this paper, a procedure called Buffered Clock Tree Aware Placement is proposed to consider clock network design in placement stage. Through register clustering and virtual clock tree construction, pseudo buffers are inserted in placement and deleted after that, so that white spaces are left for clock buffer insertion. Besides, registers in the same cluster are brought closer so that the performances of clock net, such as skew, delay and wire length, improves. The experiment results indicate an average of 22.40% improvement in skew, 7.26% improvement in delay and 2.10% improvement in wire length. Besides, the total distances of clock buffer moving during overlap removing shows an average of 17.24% improvement because of reserved white spaces.

In this paper, a new terminal sliding mode tracking control scheme is developed for a class of nonminimum phase systems with uncertainties. It is shown that, unlike conventional linear or terminal sliding mode controls, the Lyapunov stability theory in this paper is used to determine the upper and the lower bounds of the control signal and its derivative. A dynamic control signal can then be designed, subject to the bounded conditions, to drive the terminal sliding variable to converge to zero, and, on the terminal sliding mode surface, the tracking error is guaranteed to converge to zero in a finite time. A simulation example is presented in support of the proposed robust tracking control scheme.

Leakage power soars quickly as VLSI technology advance and supply voltage scaling, in the near future, it will exceed the dynamic power to become the main contributor of power dissipation. Previous methods on leakage power minimization always notice the negative effect of increasing the gate's threshold voltage Vth and the power reduction is obtained based on power and speed (or performance) tradeoff. However, increasing the gate's Vth could be used to adjust the subtrees' imbalance for a clock tree. In this paper, for a gated clock tree, we analyze the bottom up merging segment generation process and conclude the conditions for increasing the gate's Vth. Our idea is trying to assign high Vth to the gates without total wirelength and performance overheads, and in some cases, it could even be used to get more balanced subtrees. Experimental results on a set of ISCAS89 benchmark circuits demonstrate that our algorithm could assign more than half of the gates with high Vth, the resultant leakage power reduction is more than 43% without any total wirelength and delay penalties.

Clock gating is one of the most effective techniques to reduce clock network power dissipation. Although it has already been studied considerably, most of the previous works are restricted to either logic level or clock routing stage. Due to the restriction, clock gating often meets the trouble of wirelength overhead and frequent control signal switching, both of which degrade its effectiveness. Furthermore, previous design flows which insert gate logics after placement introduce a lot of overlaps, especially when there are lots of gate logics inserted. In this work, we propose a new design flow for low power gated clock network construction, in order to minimize the clock wirelength and the activity of control signals, and to eliminate the overlaps incurred by the gate logics. Our method begins with a coarse placement followed by soft register clustering. Then, we perform clock tree topology construction and zero skew clock routing to further reduce the power and the clock skew. Last, the gated clock network is fed back to the placer for incremental placement. Experimental results on ISCAS89 benchmarks demonstrate that our method outperforms previous algorithm of activity aware register placement in clock wirelength and clock power reduction with signal nets wirelength and signal nets power increase within 5% and 3%, respectively

With its advantages in wirelength reduction and routing flexibility compared with Manhattan routing, X-architecture has been proposed and applied to modern IC design. As a critical part in high-performance integrated circuits, clock network design meets great challenges due to feature size decrease and clock frequency increase. In order to eliminate the delay and attenuation of clock signal introduced by the vias, and to make it more tolerant to process variations, in this paper, we propose an algorithm of a single-layer zero skew clock routing in X-architecture (Planar-CRX). Our method integrates the extended deferred-merge embedding algorithm (DME-X, which extends DME to X-architecture) with modified Ohtsuki's line-search algorithm to minimize the total wirelength and the bends. Compared with planar clock routing in the Manhattan plane, our method achieves a reduction of 6.81% in total wire-length on average, and fewer bends. Experimental results also indicate that our solution is comparable with previous non-planar zero skew clock routing algorithm

As power consumption of the clock tree dominates over 40% of the total power in modern high performance VLSI designs, measures must be taken to keep it under control. One of the most effective methods is based on clock gating to shut off the clock when the modules are idle. However, previous works on gated clock tree power minimization are most focused on clock routing and the improvements are often limited by the given registers placement. The purpose of this work is to navigate the registers during placement to further reduce the clock tree power based on clock gating. Our method simultaneously performs (1) activity-aware register clustering that reduces clock tree power not only by clumping registers into a smaller area, but pulling the registers with similar activity pattern close to shut off more time for the resultant subtrees; (2) timing and activity based net weighting that reduce net switching power by assigning a combination of activity and timing weights to the nets with higher switching rates or more critical timing; (3) gate control logic optimization that still set the gate enable signal high if a register is active for a number of consecutive clock cycles. Experimental results show that our approach is able to reduce the power and total wirelength of clock tree greatly with minimal overheads.

This paper presents a self-organising map (SOM) based classification of lithium iron phosphate cells for a battery pack in EVs. The experimental data of the cells have been obtained to train the SOM. The temperature variation, internal resistance and available capacity of the cells are used as the inputs of the SOM, and the output of the SOM classifies the cells into three groups with the similar characteristics in terms of its input parameters. Then, the cells in the same group are connected in series to build a sorted battery pack whereas the randomly chosen cells are connected in series to build an unsorted battery pack. The comparison of the consistency between these two battery packs under different discharging conditions has demonstrated the effectiveness of the proposed classification method. In addition, the experimental results show that state of charge based approaches for cell balancing are more effective than voltage based approaches.

This paper studies droop method based wireless parallel operation of inverters. With conventional droop method, the voltage deviation is usually quite severe to achieve good power sharing among the inverters connected in parallel. To overcome this problem, an adaptive droop method is developed by which the trade-off between voltage regulation and power sharing is relieved significantly. In addition, the second order filter rather than the first order filter that is adopted to obtain the average power drawn from each module improves the transient response. Experiment has been carried out on the system with two inverters in parallel. The results have validated the strategy developed.

The paper proposes a control strategy for three-phase pulse width modulated (PWM) voltage source converter (VSC) used in distributed grid-connected generation system. The key is to take the current of inductor in the filter as feedback to regulate the output current, with the addition of a feed-forward control scheme into the inner current loop. The paper explores the fundamental performance issues of the usage of inductor current feed-forward concerning their contributions to the transient system response and the power factor. The proposed control method is implemented in a digital signal processor (DSP) based system and tested on an experimental 30 kVA prototype unit. The results exhibit the effectiveness of the proposed control strategy

The paper proposes a novel boost battery charger in which a full-bridge zero-voltage and zero-current switching (ZVZCS) PWM DC/DC converter is included. For the sake of attaining output voltage up to 600 V, a dual-full-bridge rectifier is designed to reduce high voltage stress and solve the problem of dynamic voltage sharing of the diodes. A phase shift PWM controller UC3895 is used as voltage and current regulator, and a PIC16F716 based controller is adopted to perform automatic mode switching. Advantages such as intelligent control and no additional active switch and snubber make the proposed charger efficient and cost effective. Theoretical analysis and experimental results both confirm the validity of the proposed design

Based on the design of string inverters, a high performance gird-connected photovoltaic (PV) power plant is presented. The plant consists of grid-connected single phase inverters, intelligent cluster controllers (ICC) and user-friendly monitoring software. The feed-forward control strategy based on grid voltage and load current is proposed to improve inverter's dynamic response. With an optimal maximum power point tracking (MPPT) algorithm, the maximum power output of PV modules is achieved by using forth-back voltage increment perturbation. A Sandia frequency shift based strategy which increases the anti-islanding ability of grid-connected PV power system is also discussed. The proposed system can simultaneously monitor all the inverters on-site of PV modules. The verification has been made on the experimental units. The results show that the plant has excellent capability of high efficiency, intelligent maintenance and integrated management.

This paper presents the development and qualitative validation of a doubly-fed induction generator (DFIG) wind turbine model that is represented in terms of behaviour equations of each of the subsystems, mainly the turbine rotor, the drive train, the induction generator, the power converters and associated control systems and a protection system. Simulation results obtained from the models are compared to the field measurement data in a qualitative manner due to rotor wake and lack of ability of a single anemometer for adequate measurement of wind speed acting on the large surface of the rotor. It is concluded that the model is reasonably accurate and can hence be used for representing wind turbines in power system dynamics simulations.