Smooth Mode Transition Research Articles

Power Control for Household Energy Storage Inverter With Smooth Mode Transition

Power Control for Household Energy Storage Inverter With Smooth Mode Transition

Simple model of turbine-based combined cycle propulsion system and smooth mode transition

Abstract Turbine-based combined cycle (TBCC) propulsion system is becoming one of the most promising propulsion systems for two-stage-to-orbit reusable launch vehicle. Mathematic model of this combined cycle engine is helpful for the basic understanding of performance analysis of this propulsion system. We developed mathematic model of TBCC propulsion system based on C++ platform in this paper. Firstly, turbojet engine was built on component level and ramjet engine was calculated through stream thrust function. Then, performance of turbine-based combined cycle propulsion system along a specific flight trajectory was investigated. According to the thrust of this combined cycle engine, mode transition point was suggested at Ma 2.5, which may achieve smooth mode transition from turbine mode to ramjet mode. Finally, mode transition based on smooth mass flow and smooth thrust criteria were studied. The thrust gap arises during smooth mass flow mode transition, particularly when the turbojet engine afterburner is powered off at the start of the mode transition, and it meets 34 % of the total thrust. Smooth thrust mode transition may be achieved by delaying the turbojet engine afterburner power off and injecting additional fuel into ramjet burner.

Generalized control for distributed energy inverter in community microgrid system: Off-grid and grid-connected operation

With the increasing penetration of distributed energy resources (DER) in microgrids, DER power inverters have become a critical asset for providing power support to these microgrids. Meanwhile, the grid-forming (GFM) inverters, among these DER inverters, have gained significant attention in microgrid applications for their capability to enable the DERs to operate in different microgrid conditions and various operation modes. Moreover, with the implementation of these GFM inverters, smooth operation mode transition, GFM functions as well as black start functions can be obtained to improve the operation of the microgrid systems. In this article, a generalized control method for a single-phase GFM inverter is developed for community microgrid applications, facilitating smooth operation behavior in both operation modes with grid support functions and stable transition for different microgrid conditions. The control design procedure and function analysis of the proposed control method are explained in detail based on the community microgrid system. The effectiveness of the method in this paper is demonstrated on a 10 kW single-phase GFM inverter prototype with comparison to a model predictive method in recent literature.

Smooth Transition Control Strategy for Operation Modes of Optical Storage Microgrid based on VSG

Addressing the challenge of suppressing voltage and frequency oscillations during mode transitions and achieving smooth transitions between grid-connected and islanded operation modes in peer-to-peer structured optical storage microgrids, is an urgent technical issue. This paper proposes a control strategy for smooth mode transitions based on numerical soft starters, focusing on the dynamic characteristics of voltage and frequency in optical storage microgrids during grid-connected and islanded operation modes. The numerical soft starter smoothens the input reference value of the current inner loop, reducing the impact of transient surge current on the current inner loop during transitions, thus ensuring the oscillations of bus voltage and frequency during microgrid mode transitions. In islanded operation mode, a VSG control strategy is introduced by constructing a small signal model to analyze the frequency response characteristics of the system under different inertia and damping characteristics, setting appropriate control parameters to provide strong frequency support for the system during islanded operation. Finally, an optical storage microgrid system is established using Matlab/Simulink to conduct simulation experiments under conditions such as grid-connected/islanded mode transitions, load fluctuations, and sudden changes in photovoltaic output power, validating the effectiveness of the proposed smoothing strategy.

Research on Adaptive Cycle Engine Mode Transition Control Method

Mode transition is an important dynamic process of an adaptive cycle engine (ACE). In order to obtain a smooth mode transition process, the closed-loop controller is designed based on the strong robust augmented linear quadric regulator (ALQR) method, and with the objective of minimizing the thrust fluctuation in the process of mode transition, an open-loop geometrical mechanism control schedules optimization method based on Bézier curves is proposed, so that the closed-loop control and the open-loop control can work in coordination. The simulation results at the subsonic cruise operating point and supersonic cruise operating point show that based on the optimized open-loop geometrical mechanism control schedules and the designed closed-loop ALQR control system, the ACE achieves fast and smooth geometrical mechanisms and engine output transition during the mode transition process with a maximum thrust fluctuation of 2.58%, which is much smaller than that of the traditional linear variation geometric mechanisms with a maximum 4.64% thrust fluctuation, which verifies the effectiveness of the proposed control method.

Research on the design method of mode transition control law for Ma6 external parallel TBCC engine

Abstract To achieve a fast and reliable mode transition of the Ma 0–6 external parallel TBCC engine, a design method for the transition state control law is developed. The design parameters of the TBCC engine are obtained based on the mission requirements of hypersonic aircraft. For the key mode transition process of the combination engine, a segmented mode transition strategy is formulated with the objectives of smooth thrust and continuous flow. The mode transition control law of the combination engine is designed and optimized using the Hooke-Jeeve Direct Search Method. The results demonstrate that the proposed design method for the mode transition control law can effectively enable a fast and smooth mode transition of the combination engine, with a total duration of 7 s. During the mode transition process, the total thrust fluctuation during the transition from the turbofan windmill state to the turbofan shutdown state is the largest, and the maximum relative error between the total thrust and the expected value during the mode transition process is 0.4 %.

Design and real-time implementation of wind–photovoltaic driven low voltage direct current microgrid integrated with hybrid energy storage system

Low-voltage direct current (LVDC) microgrid has emerged as a new trend and smart solution for the seamless integration of distributed energy resources (DERs) and energy storage systems (ESS). This paper presents a coordinated controlled power management scheme (PMS) for wind–solar fed LVDC microgrid equipped with an actively configured hybrid energy storage system (HESS). The comprehensive design, development, implementation and thorough result analysis is presented to validate the proposed PMS performance. It dynamically adapts to different operating modes based on the availability of DERs and load demand. By incorporating the HESS, the scheme effectively handles sudden and gradual power surges, leading to swift regulation of the DC bus voltage, effective power balance and reduced stress on the battery. A laboratory test bench is developed comprising a wind power generating unit (WPGU), solar power generating unit (SPGU), battery energy storage system (BESS), and supercapacitor energy storage system (SCESS). Moreover, the detailed design and testing of various converters, gate drivers, filters, signal conditioning along with calibration of sensors are discussed. The developed PMS is executed using a DS1103 digital controller confirming its effectiveness in facilitating smooth mode transition and proper power sharing among all DERs and loads.

Adaptive Control for Undisturbed Functioning and Smooth Mode Transition in Utility Interactive Wind–Solar Based AC/DC Microgrid

Adaptive Control for Undisturbed Functioning and Smooth Mode Transition in Utility Interactive Wind–Solar Based AC/DC Microgrid

High Efficiency Single-phase T-type LCL-filtered Inverter with Multimode Control and Smooth Mode Transition

High Efficiency Single-phase T-type LCL-filtered Inverter with Multimode Control and Smooth Mode Transition

A Bimodal Hydrostatic Actuator for Robotic Legs with Compliant Fast Motion and High Lifting Force

Robotic legs, such as for lower-limb exoskeletons and prostheses, have bimodal operation: (1) within a task, like for walking (high speed and low force for the swing phase and low speed and higher force when the leg bears the weight of the system); (2) between tasks, like between walking and sit–stand motions. Sizing a traditional single-ratio actuation system for such extremum operations leads to oversized heavy electric motor and poor energy efficiency at low speeds. This paper explores a bimodal actuation concept where a hydrostatic transmission is dynamically reconfigured using custom motorized ball valves to suit the requirements of a robotic leg with a smaller and more efficient actuation system. First, this paper presents an analysis of the mass and efficiency advantages of the bimodal solution over a baseline solution, for three operating points: high-speed, high-force, and braking modes. Second, an experimental demonstration with a custom-built actuation system and a robotic leg test bench is presented. Control challenges regarding dynamic transition between modes are discussed and a control scheme solution is proposed and tested. The results show the following findings: (1) The actuator prototype can meet the requirements of a leg bimodal operation in terms of force, speed, and compliance while using smaller motors than a baseline solution. (2) The proposed operating principle and control schemes allow for smooth and fast mode transitions. (3) Motorized ball valves exhibit a good trade-off between size, speed, and flow restriction. (4) Motorized ball valves are a promising way to dynamically reconfigure a hydrostatic transmission while allowing energy to be dissipated.

A Three-Level Boost Converter With Fully State-Based Phase Selection Technique for High-Speed VCF Calibration and Smooth Mode Transition

A Three-Level Boost Converter With Fully State-Based Phase Selection Technique for High-Speed V_CF Calibration and Smooth Mode Transition

Analysis and Design of a High Frequency Wireless Battery Charging System With Smooth Mode Transition Characteristics

Analysis and Design of a High Frequency Wireless Battery Charging System With Smooth Mode Transition Characteristics

Numerical study on the dynamic process of ramjet/scramjet mode transition in the integrated full flow path for RBCC engine

As the inflow velocity increases, rocket-based combined cycle(RBCC) engine typically require a ramjet/scramjet mode transition within the flight range Ma∞ = 5.5 to 6.0. However, during the mode transition process, the reduction of the fuel mass flow rate usually causes the combustion intensity in the engine to drop sharply in a very short time, which will further lead to severe thrust fluctuations. So some technical methods need to be applied in this process to realize smooth mode transition. In this paper, different throttling strategies (kerosene mass flow rate dominant and rocket mass flow rate dominant) were designed and employed to study the dynamic mode transition process in the integrated RBCC engine flow path through three-dimensional numerical simulation for flight Ma∞ = 5.5 and Ma∞ = 6.0, respectively. The results show that when RBCC engine operates under the condition of large mass flow rate of fuel, the wall flow separation zone caused by oblique shock wave and combustion cannot be effectively improved by the bleed block and the inlet is still in the limit working state. Under flight Ma∞ = 5.5 condition, with the reduction of fuel equivalence ratio, RBCC engine successfully transited from ramjet mode to scramjet mode, and the flow separation zone near the bleed block disappeared. At this time, the high temperature gas of the rocket has no obvious effect on the thrust gain of the engine. By adjusting fuel mass flow rate in a small range and rocket mass flow rate in a large range, stable mode transition can be achieved, with relatively small time consumption and minimum thrust fluctuation during mode transition. With the increase of flight altitude, under flight Ma∞ = 6.0, the incoming flow speed increases, but the air capture ability of the inlet decreases, which is not conducive to the mixing of fuel and air combustion. When Ma∞ = 5.5, the mode transition by reducing the fuel equivalence ratio will cause the RBCC engine to produce huge thrust fluctuations, and the range of the high-pressure zone in the combustor will be greatly reduced. In order to ensure the stable operation of the RBCC engine, the rocket needs to operate at a larger mass flow rate.

Numerical study on the dynamic process of ramjet/scramjet mode transition in the integrated RBCC full flow path through multistage fuel injection strategies

The rocket-based combined-cycle (RBCC) engine usually completes the transition process from ramjet to scramjet mode under the Ma∞ = 5.5–6.0. The dual-mode (ramjet/scramjet) transient process is an important technology for engine operation. CFD modeling based on Reynolds average Navier-Stokes was for studying the influence of fuel injection position, high-temperature rocket jet and fuel throttling time on the combustion flow structure and transient characteristics of RBCC engine during the mode transiton . The results showed that whether RBCC engine could successfully achieve stable mode transition was mainly influenced by flame stability in the combustor. When the rocket shuts down, it was more suitable to choose the fuel injection arrangement which distributed downstream of the combustor to realize relatively smooth mode transition. The analysis shows that in the mode transition process, using the synergistic combustion-supporting effect of the cavity and the strut is beneficial to improve the fuel combustion efficiency and reduce the thrust fluctuation. Although the high temperature rocket jet with low mass flow rate cannot maintain the fuel combustion in the isolator at high Mach number, it can expand the high temperature combustion area width in the central flow of RBCC engine and increase the secondary fuel combustion efficiency. Therefore, keeping the rocket running at low mass flow rate can reduce the thrust drop caused by insufficient fuel heat release. When adopting a mode transition strategy that throttles the fuel linearly over time, the engine can go through the thrust dip more smoothly, but this correspondingly increases the time required for the internal flow field to stabilize.

Composite Learning Adaptive Interaction Control for High-DoF Collaborative Robots*

Variable impedance control is essential for improving safety and naturalness during physical human-robot interaction. However, the robot target impedance is usually difficult to be realized for existing variable impedance control methods. This paper proposes a composite learning adaptive interaction control strategy for robots to achieve target impedance under parametric uncertainty. A multi-mode adaptive control scheme is defined based on weighting functions to ensure smooth mode transitions. A composite learning technique is applied for exact robot modeling online such that target impedance can be achieved under interval excitation that is much weaker than persistent excitation. The proposed method can achieve variable stiffness and damping with guaranteed stable and safe interaction. Experiments on a collaborative robot with 7 degrees of freedom named Franka Emika Panda have validated the effectiveness and superiority of the proposed method.

Model Predictive Control for Four-Switch Buck–Boost Converter Based on Tuning-Free Cost Function With Smooth Mode Transition

Four-switch buck-boost (FSBB) converter has the capability of bidirectional voltage step-down and step-up, which has attracted attentions in the fields of energy storage and solar energy. However, it faces the challenges in multimode operation and smooth mode transition, which rely on the complex mode detection scheme and cumbersome parameter tuning. In this article, the inherent limitation is analyzed through inconsistent frequency response and noncontinuous duty cycle operation region aspects. Then, a model predictive control (MPC) method characterized by tuning-free cost function is presented to achieve multimode control and smooth transition simultaneously. With the goal of ensuring the reference current tracking under inconsistent frequency response, a duty cycle and current ripples prediction are presented for all switching combinations. Then, a tuning-free cost function is utilized to overcome the gaps in noncontinuous duty cycle operation region and a smooth mode transition is achieved. Further, the robustness of the current tracking capability is analyzed mathematically considering the inductance variation and stray resistance variation. Finally, a comparative experiment proves the effectiveness. And it shows that the method can improve the efficiency by 0.4% compared with the traditional four-mode control.

Subject-Independent Continuous Locomotion Mode Classification for Robotic Hip Exoskeleton Applications.

Autonomous lower-limb exoskeletons must modulate assistance based on locomotion mode (e.g., ramp or stair ascent) to adapt to the corresponding changes in human biological joint dynamics. However, current mode classification strategies for exoskeletons often require user-specific tuning, have a slow update rate, and rely on additional sensors outside of the exoskeleton sensor suite. In this study, we introduce a deep convolutional neural network-based locomotion mode classifier for hip exoskeleton applications using an open-source gait biomechanics dataset with various wearable sensors. Our approach removed the limitations of previous systems as it is 1) subject-independent (i.e., no user-specific data), 2) capable of continuously classifying for smooth and seamless mode transitions, and 3) only utilizes minimal wearable sensors native to a conventional hip exoskeleton. We optimized our model, based on several important factors contributing to overall performance, such as transition label timing, model architecture, and sensor placement, which provides a holistic understanding of mode classifier design. Our optimized DL model showed a 3.13% classification error (steady-state: 0.80 ± 0.38% and transitional: 6.49 ± 1.42%), outperforming other machine learning-based benchmarks commonly practiced in the field (p<0.05). Furthermore, our multi-modal analysis indicated that our model can maintain high performance in different settings such as unseen slopes on stairs or ramps. Thus, our study presents a novel locomotion mode framework, capable of advancing robotic exoskeleton applications toward assisting community ambulation.

Understanding the combustion mode transition from CDC to RCCI and RCCI to CDC – An experimental approach

This article presents an experimental understanding of combustion mode transition from conventional diesel combustion (CDC) mode to reactivity-controlled compression ignition (RCCI) combustion mode. In the current study the variations in combustion, performance, and emissions during the mode transition were investigated and accordingly a dual fuel control algorithm for achieving smooth transition between CDC and RCCI combustion modes was developed. Experimental data are presented for CDC with diesel and RCCI with Gasoline/Diesel at 1600 rev/min, 25 N.m torque only, considering the data size and ease of understanding the mode transition. Nine steps have been adopted to switch from CDC to RCCI combustion mode. The operating variables such as number of diesel injections, injected diesel mass between the injections, gasoline energy fraction, diesel start of injection, and exhaust gas recirculation (EGR) flow rate have been altered to switch from CDC to RCCI. Changes in combustion, performance, and emissions have been recorded and analyzed at each operating variable to determine the optimal path for smooth combustion mode transition. A similar approach has been extended to medium and high loads to obtain the optimal path. Finally, all the optimal paths have been collated to develop calibrated maps for operating the chosen test engine from CDC to RCCI and RCCI to CDC modes smoothly.

Monopolar Fault Reconfiguration of Bipolar Half Bridge Converter for Reliable Load Supply in DC Distribution System

This article proposed the concept of monopolar fault reconfiguration for bipolar dc distribution system realized with Bipolar Half Bridge (BiHB) converter. Monopolar fault reconfiguration oriented from bipolar high voltage direct current (HVdc) transmission grid. For dc distribution, the operation aim is to provide uninterrupted power supply to critical load under monopolar fault. It requires interfacing circuit with fault-tolerant capability as well as control design considering both bipolar and monopolar working mode. The proposed BiHB converter achieves mode switching by reconfiguring the converter switching pattern. Considering both monopolar and bipolar working mode, a bipolar modulation method is proposed for coordinate circuit design. Key influence factors relating to the transient voltage spikes have been identified, including the fault detection delay and the modulation method. Besides, to suppress the voltage spikes caused by monopolar fault, feed-forward compensation is adopted for smooth mode transition. The proposed BiHB converter and control strategy have been comparatively evaluated under fault protection and restoration. Uninterrupted power supply of load has been attained, in validation of the proposed monopolar fault reconfiguration concept.

Control of Single-Phase Distributed PV-Battery Microgrid for Smooth Mode Transition With Improved Power Quality

In this article, multiple parallel photovoltaic (PV) inverters based microgrid is developed to enhance the reliability and accessibility of electricity in remote areas. A self-adaptive control strategy is presented for a microgrid to ensure a seamless transition between the islanded mode (IAM) and grid-connected mode (GCM) of operation with a proportional power sharing. This microgrid consists of two solar PV inverters based on local distributed generation (DG) units. Each PV-inverter unit feeds an active power to support local loads and the power demand of each local load is shared between respective DG units and microgrid. The PV-battery-interfaced main unit with a self-adaptive control strategy in parallel with a PV array supported unit-2 is considered to operate in the IAM and GCM of operation. The control strategy achieves transient free operation during load disturbances, power variation at the PV array side, and off-grid operation. Moreover, the microgrid ensures high-quality performance at the point of common coupling and provides the seamless transition between GCM and IAM to guarantee a continuous power to critical loads. The microgrid simulation and experimental results are presented under various operating conditions, such as load variation, intermittent power generation, and automated mode transition between GCM and IAM.