Mode Switching Control Research Articles

Control Strategy of Mode Transition with Engine Start in a Plug-in Hybrid Electric Bus

Torque coordinated control of the relevant power sources has an important impact on the vehicle dynamics and driving performance during the mode transition of the hybrid electric vehicles(HEVs). Considering the dynamic impact problem caused by mode transition, this paper, based upon the structural features of axially paralleled hybrid power system, introduces the bumpless mode switching control theory to analyze multi-mode transition. Firstly, the state transition process is abstracted as the state space transition problem of hybrid system. Secondly, the mode transition is divided into four sub-states, and the state model of each sub-state is established. Thirdly, taking the cost functions as the optimization objective, the state switching process is solved, and the control vectors of each switching process are obtained. Simulation and experimental results show that the proposed control strategy can effectively suppress torque fluctuation, avoid longitudinal acceleration impact, and improve driving performance.

Robust Switching Control of the Direct-Drive Servo Control Systems Based on Disturbance Observer for Switching Gain Reduction

Due to the existence of external disturbance which affects the systems’ robustness and stability, a robust sliding mode switching controller with disturbance observer method has been developed for the switching systems of the direct-drive servo control systems, which can eliminate the chatter and reduce the switching gain of the switching systems completely or alleviate it greatly. According to the Lyapunov stability method and the periodically switching law, the resulting closed-loop switched system is robustly stable such that all the signals in the resulting closed-loop switched system of the direct-drive servo control systems keep bounded and the sliding surface of the switching system can be well reached. Finally, the presented switching control scheme is easy to implement and simulation results illustrate the good control performance.

A comparative study of phase margin based digital and analog controlled synchronous buck with optimum LC filter

PurposeTraditionally, industrial power supplies have been exclusively controlled through analog control to sustain high reliability with low cost. However, with the perpetual decrement in cost of digital controllers, the feasibility of a digitally controlled switch mode power supply has elevated significantly. This paper aims to outline the challenges related to the design of digital proportional-integral (PI) controlled synchronous rectifier (SR) buck converter by comparing controller performance in continuous and discrete time. The trapezoidal approximation-based digital PI control is designed for low voltage and high-frequency SR buck converter operating under continuous conduction mode.Design/methodology/approachThe analog and digital controller are designed using a SISO tool of MATLAB. Here, zero-order hold transform is used to convert the transfer function from continuous to discrete time. Frequency and time domain analysis of continuous plant, discrete plant and close loop system is performed. The designed digital PI control is simulated in MATLAB Simulink. The simulated results is also verified on hardware designed around digital signal processing control.FindingsThe continuous and discrete control loops are validated with multiple tests in the time and frequency domain. The detailed steady state theoretical analysis and performance of the SR buck converter is presented and verified by simulation. It is found that the delay in digital control loop results in a low phase margin. This phase margin decreases with higher bandwidth. The hardware experiments with the digital control loop are carried out on a 10 W prototype. The chosen parameters for the SR buck converter are found to be optimum for steady and transient state response.Originality/valueThis paper compares the digital and analog control approach of compensator design. It focuses on the implications created at the time of transforming the control design from continuous to discrete time. Further, it also focuses on the selection of parameters such as phase margin, bandwidth and low pass filter.

Development of a Hybrid Electric Motorcycle that Accords Energy Efficiency and Controllability via an Inverse Differential Gear and Power Mode Switching Control

In this study, inverse differential gear and power mode switching control were used to develop a hybrid electric motorcycle (HEM). An inverse differential gear power splitter was installed to integrate or distribute the power of an internal combustion engine (ICE), thus achieving single/dual power output. In addition, the transmission system was configured with continuously variable transmission to adjust the transmission speed reduction ratio and stabilize the power output. As a result, three power modes (i.e., the motor drive mode, ICE drive/generator mode, and dual power drive mode) could be switched between each other smoothly. Finally, our HEM was tested by a chassis power gauge. The test results showed that the HEM consumed 41.1% less fuel and produced 58.6% less exhaust emissions compared with conventional ICE motorcycles. In terms of controllability, the acceleration time for 0–100 m was 2.4 s less than the Taiwan E-scooter Standard (TES). The fastest highest vehicle speed was 2.1 times greater than the test of the TES.

Analysis of Segment Parameters for Different Working Conditions on Mode Switching Control Strategy

Due to the requirements of global energy conservation and environmental protection, parallel hybrid electric buses have developed rapidly. The mode switching control strategy has great significance to the stability of the parallel hybrid electric bus. The principle of minimum value has achieved great development in the optimal control of the mode switching for parallel hybrid electric buses. Since the Hamilton function is a complex function of the control variable and the bus should traverse the entire control variable domain when searching for the optimal control variables. Therefore, the control strategy based on the principle of minimum value requires a large amount of computation time. Based on the principle of minimum value, this paper combines the mode switching control strategy with the identification and prediction of working conditions, and establishes a working condition segments library. The influence of segment parameters for different working conditions on mode switching control strategy is analyzed. The analysis results show that the prediction effect is better when the working condition segment size is 30s and the search range is specified as the actual trip time range, and the mileage range has little effect on SOC and fuel consumption.

Switching Performance Improvement Based on Model-Predictive Control for Wind Turbine Covering the Whole Wind Speed Range

A wind energy conversion system is mainly operated in a partial-load region and a full-load region. In the partial-load region, the primary objective is to maximize energy conversion efficiency, whereas the main goal is maintaining the output power at the rated level in the full-load region. The two control regions are switched in accordance with prevailing wind speed. However, steep and large changes of generator power, as well as mechanical loads, may be experienced during switching transient, which bring about negative impacts on power system reliability and turbine lifetime. This paper presented an advanced model-predictive control considering switching performance improvement. The proposed method not only achieved the control objectives in both two control regions, but also mitigated uncertain power fluctuations and mechanical loads during control mode switching. This high switching performance benefited from the presented dynamic switching transient process driven by the defined wind speed crossing events. During switching transient, system operating states were transferred along with the proposed dynamic vector. Small-signal analysis was employed to prove the good stability and dynamic performance of the system in switching transients. Simulation and hardware-in-the-loop experimental studies verified the effectiveness of the proposed method.

Research on Dynamic Coordination Active Mode Switching Control Strategy for Hybrid Electric Vehicle Based on Traffic Information

In traditional hybrid-vehicle mode switching, a switch when it changes in road conditions is sensed. Because of the delays in the control system, lags in switching and large impacts on the switching process occur, in what is referred to as “passive mode switching.” Via a combination of an intelligent networked hybrid vehicle with environmental sensing, “passive mode switching” can be converted into “active mode switching,” reducing the impact degree during the switching process and increasing ride comfort. Combined with the application of intelligent transportation system in current traffic, an intelligent traffic scene with optimal traffic-light control (OTLC) is established. The OTLC algorithm determines the future driving-state information of the hybrid vehicle in a built scenario and predicts the driving mode of the hybrid vehicle for the next moment. The current mode and future mode are compared, active control of key components, such as the engine, motor, clutch, and electric-mechanical continuously variable transmission (EMCVT), under the premise of different conditions, is made possible, and corresponding dynamic coordinate active-mode-switching control strategies are developed. The proposed control strategy is simulated and verified on a built-in hardware-in-the-loop (HIL) test platform based on traffic scenarios. The results show that the dynamic coordinated active-mode-switching control strategy presented in this paper is superior to the traditional mode-switching control strategy and that it can overcome the problem of switching lag due to delays in the control system and the large impact during the switching process, reducing the impact degree by about 21.2%, which improves ride comfort.

A Reconfigurable Hybrid Low Dropout Voltage Regulator for Wide-Range Power Supply Noise Rejection and Energy-Efficiency Trade-Off

A scan-reconfigurable hybrid low dropout (LDO) macro with four operating modes to support tuning across a wide range of power supply noise rejection and power efficiency is presented. The configurations include: 1) a full-digital LDO; 2) an analog loop in parallel with a digital loop in switched mode control; 3) an analog LDO in parallel with discrete current sources; and 4) discrete current sources with an analog LDO in shunt with the load. Measurements on a 130-nm CMOS test chip show a wide power supply noise rejection range of −9 dB to −34 dB and a corresponding power efficiency range of 87% to 56%.

A Uniform Control Strategy for the Interlinking Converter in Hierarchical Controlled Hybrid AC/DC Microgrids

This paper presents a uniform control strategy for the bidirectional ac/dc interlinking converter (BIC) in hierarchical controlled hybrid microgrid. The uniform control strategy unifies different control structures for multifunctional BIC in terms of power management, ac and dc voltage support. With the unified control structure, various triggering mechanisms for BIC mode-switch are not compulsory in response to the relevant scenario changes in the power network. Therefore, the negative consequences, such as unsmooth transition and system collapse due to the inaccurate or slower mode switch, can be avoided. Moreover, the uniform control strategy is also applicable for the hierarchical controlled hybrid microgrid, whose control architecture is typically comprised of the centralized and decentralized levels. This enables the communication fault ride-through capability and the impact from the communication failures can thus be mitigated. To sum up the above two features, the proposed control strategy is able to provide a smooth operation for the BIC without control mode switch in the event of unintentional scenario changes in power or communication network. To verify the validity of the proposed uniform control strategy, the controller hardware-in-the-loop experimental results have been provided in this paper.

Active nonreciprocal acoustic metamaterials using a switching controller.

A class of active acoustic diodes and metamaterials is developed to control the flow and distribution of acoustic energy in acoustic cavities and systems. Such development departs radically from the currently available approaches where the non-reciprocities are generated by hard-wired designs, favoring one transmission direction which is dictated by the arrangement of the hardware and hence it cannot be reversed, or without the presentation of rigorous control theory analysis. The proposed active nonreciprocal acoustic metamaterial (ANAM) cell consists of a one-dimensional acoustic cavity provided with active flexible boundaries. These boundaries are made from piezoelectric bimorphs interacting with the cavity to monitor the pressures of the propagating acoustic waves. The outer layers of the bimorphs provide the necessary control actions by direct application of the appropriate control voltage on each layer or by proper connection of nonlinearly activated shunted networks of switching resistors. The control of the switching is carried out using a Switching Mode Control (SMC) strategy. In this strategy, a lumped-parameter model of the ANAM cell is developed to predict the nonreciprocal characteristics of the cell by proper selection of the slope of the switching surfaces. Numerical examples are presented to demonstrate the merits of the proposed SMC.

Research on Integrated Control of Microgrid Operation Mode

The mode switching control of microgrid is the focus of its system control. According to the characteristics of different control, an integrated control system is put forward according to the detecting voltage and frequency deviation after switching of microgrid operating mode. This control system employs master-slave and peer-to-peer control. Wind turbine and photovoltaic(PV) adopt P/Q control, so the maximum power output can be achieved. The energy storage will work under the droop control if the system is grid-connected. When the system is off-grid, whether to employ droop control or P/f control is determined by system status. The simulation has been done and the system performance can meet the requirement.

Online Evaluation Method of Electrolytic Capacitor Degradation for Digitally Controlled SMPS Failure Prediction

In this paper, we propose a new capacitor degradation evaluation method aimed at failure prediction and suitable for digitally controlled switching mode power supply (SMPS) for servers. Electrolytic capacitors have one of the highest component failure rates in SMPS; therefore, we attempt to detect an equivalent series resistance degradation of the electrolytic capacitor directly from the data fetched to a digital controller of the SMPS. With a SPICE simulation and a rapid control prototyping evaluation, we confirm the degradation can be detected by the data at a transient response under a normal operation without additional circuits. Even only 10% of a load step change, which commonly occurs in SMPS for servers, causes detectable transient response degradation.

Switched-Mode-Control Based Hybrid LDO for Fine-Grain Power Management of Digital Load Circuits

Switched-mode-control (SMC) is a control methodology that allows instantaneous switching between controllers to extend the dynamic range of feedback circuits. A hybrid low dropout voltage regulator utilizing SMC is designed in 130 nm CMOS for fine-grain power management, fast droop recovery, and accurate voltage regulation of digital load circuits. The design provides an optimal tradeoff between performance and accuracy by switching between a digital and an analog control loop. Measurements from the test-chip show near-threshold-voltage operation, peak transient response of 0.71 ns/mA, and a peak current efficiency of 98.64%.

An assigned responsibility system for robotic teleoperation control

This paper proposes an architecture that explores a gap in the spectrum of existing strategies for robot control mode switching in adjustable autonomy. In situations where the environment is reasonably known and/or predictable, pre-planning these control changes could relieve robot operators of the additional task of deciding when and how to switch. Such a strategy provides a clear division of labour between the automation and the human operator(s) before the job even begins, allowing for individual responsibilities to be known ahead of time, limiting confusion and allowing rest breaks to be planned. Assigned Responsibility is a new form of adjustable autonomy-based teleoperation that allows the selective inclusion of automated control elements at key stages of a robot operation plan’s execution. Progression through these stages is controlled by automatic goal accomplishment tracking. An implementation is evaluated through engineering tests and a usability study, demonstrating the viability of this approach and offering insight into its potential applications.

Fast inrush voltage and current restraining method for droop controlled inverter during grid fault clearance in distribution network

Control mode switching strategy of droop controlled inverter can effectively avoid overcurrent during grid fault, but it is easy to cause inrush voltage and current during grid fault clearance, which leads to the failure of fault ride through process of the distribution network. In this study, a new control mode re-switching method is proposed on the basis of restricting the outputs of the off-line controllers, which can make sure that the inrush voltage and current are suppressed and return to the normal condition quickly. First, the dynamic characteristics of fault current of droop controlled inverter are analysed. Then, the instantaneous inrush voltage and current caused by the output saturations of voltage controller and power controller before the re-switching process are mainly discussed. This method takes full advantage of integration of the existing off-line controllers to limit the output saturations, which can make the inrush problems well solved, and reduce the influence on grid connected inverters and the distribution network. Simulation results verify the validity of the theoretical analysis.

A chattering-free adaptive second-order non-singular fast terminal sliding mode control scheme for a class of nonlinear uncertain systems

In this paper, an adaptive second-order non-singular fast terminal sliding mode (SONFTSM) control scheme is proposed so as to achieve finite-time stability with chattering-free control inputs for a class of nonlinear uncertain systems. Instead of the traditional control input in primitive sliding mode switching control design, the real control input is the time integration of the designed derivation of control input with discontinuous terms such that the chattering phenomenon can be reduced. An integral terminal sliding mode (ITSM) and a non-singular fast terminal sliding mode (NFTSM) are applied into the equivalent control design such that finite-time convergence of system states can be guaranteed when it moves on a sliding surface. Then, an adaptive method is utilised to estimate the unknown upper bound of the lumped uncertainty caused by modelling error and external disturbance. The stability analysis of closed-loop system can be demonstrated by constructing Lyapunov candidate function. Finally, the simulation results verify the effectiveness of proposed control scheme.

The Strategy of Inverter Seamless Mode Switching in Master-Slave Independent Micro-grid

In order to realize the uninterruptible power supply in the master-slave independent micro-grid system, the micro-grid inverter needs to realize the mode switching of the grid-connection/grid-disconnection. How to reduce the transient oscillation during switching, so as to effectively achieve seamless mode switching is a key issue to be solved. In this paper, a typical master-slave control independent micro-grid is used as an example, the strategy of mode switching is improved in two aspects. On the one hand, the state-following algorithm is adopted to improve the switching strategy of the outer loop. On the other hand, the current inner loop is taken by the H∞ robust controller to improve the robustness of the controller. Compared with the traditional PI control mode switching, this paper illustrates the feasibility of the proposed strategy through the simulation and experiment verification. The improvement strategy in this paper can effectively reduce the voltage and current oscillation during mode switching.

Optimal Switched Mode Control to Synthesize Dynamic Frequency Response from Virtual Synchronous Machine in Islanded Microgrid Operation

Abstract Islanded microgrids can experience severe frequency variation due to their inherently low inertia. Virtual inertia has been proposed in the literature to overcome this shortage. Virtual Synchronous Machine (VSM) concept has been the cornerstone of realizing virtual inertia from inverter connected energy sources. In this paper we propose and solve an optimal control problem to identify the optimal switching controls that achieve best dynamic frequency response from VSM. The results show that the optimal number of switching stages is independent of system parameters, and the optimal timing for switching between two control modes can be determined using local measurements alone, without having to perform complex computations.

Mode switching control for a multi-functional variable refrigerant flow system

The multi-functional variable refrigerant flow system enables simultaneous heating and cooling of the zones it serves by allowing the heat exchangers of both indoor units and outdoor units to operate as evaporators or condensers. To realize automatic and smooth switching between different modes, a mode switching strategy is proposed for a multi-functional variable refrigerant flow system. Whether to turn on or off an indoor unit is determined by the zone temperature and a preset hysteresis band about the temperature set-point. Based on a thermodynamic analysis, a decision variable for determining outdoor unit-heat exchangers mode switching is proposed as the outdoor unit-heat exchangers airside temperature differential normalized by the dimensionless outdoor unit fan speed. Two bumpless transfer strategies are applied to produce smooth mode switching. To evaluate the proposed strategy, a simulation study is performed with a Modelica-based dynamic simulation model of a four-zone multi-functional variable refrigerant flow system. Simulation results validate the effectiveness of the proposed strategy and the performance of the bumpless transfer strategies.

Hierarchical and Adaptive Neuro-Fuzzy Control for Intelligent Energy Management in Hybrid Electric Vehicles

This work is concerned with the minimization of total energy consumption (summation of electric battery and fuel) of hybrid hydraulic-electric vehicles through an energy management combined approach incorporating elements of fuzzy logic, neural network and rule-based algorithms. In this paper, the global vehicle effciency is calculated by considering electrical motor, battery, engine, hydraulic pump, hydraulic motor and the transmission. An adaptive fuzzy neural algorithm is embedded in the vehicle with a fuzzy mode-switching control strategy along with proposed fuzzy tuning controllers to achieve real time control. In addition, a new formula is developed to update the proposed fuzzy controller. An intelligent hierarchical hybrid controller strategy is employed with several advantages: (i) proposed strategy does not depend on the a priori knowledge of the driving event, which makes it suitable to be implemented online; (ii) it can be easily implemented in real time based on fuzzy rule-based strategy containing five operation modes; (iii) rate of charge of the battery is limited to minimize aging effects; (iv) engine is operated near its optimal range. The effectiveness of the overall proposed architecture is demonstrated under various conditions in MATLAB/Truckmaker simulations which show increased efficiency over Pontryagin’s minimum principle. Offline and online control performance of the proposed approach are tested.