Coordinated Control Method Research Articles

Формирование заданной траектории повышенной гладкости для применения метода согласованного управления

Формирование заданной траектории повышенной гладкости для применения метода согласованного управления

Active Power and DC Voltage Coordinative Control for Cascaded DC–AC Converter With Bidirectional Power Application

Two stage-cascaded converters are widely used in dc–ac hybrid systems to achieve the bidirectional power transmission. The topology of dual active bridge cascaded with inverter (DABCI) is commonly used in this application. This paper proposes a coordinative control method for DABCI and it is able to reduce the dc-link voltage fluctuation between the DAB and inverter, then reduce the stress on the switching devices, as well as improve the system dynamic performance. In the proposed control method, the DAB and inverter are coordinated to control the dc-link voltage and the power, and this responsibility sharing control can effectively suppress the impact of the power variation on the dc-link voltage, without sacrificing stability. The proposed control method is also effective for DABCI in unidirectional power transmission. The effectiveness of the propose control has been validated by both simulations and experiments.

Coordinated control strategy for doubly‐fed induction generator with DC connection topology

With the development of wind power generation system and requirement of large-scale and long-distance power transmission, it is greatly important for wind farm to achieve the high effective DC grid connection technology. This study presents a novel grid connection topology for doubly-fed induction generator (DFIG) connected to a DC-link, in which a stator side converter and rotor side converter fed by a common DC bus are employed. Coordinated control method for the converters is proposed to regulate the electromagnetic torque directly based on the air-gap flux orientation technique. Compared with the traditional grid connection system, the proposed system has a lot of advantages such as simpler structure, lower requirement for the converter capacity and higher power transmission efficiency. The power distribution between stator side converter and rotor side converter is analysed based on the proposed grid connection topology. Finally, DFIG-based experimental system is developed to validate the correctness and availability of the proposed DC grid connection topology and control strategy.

Control Method for Electromagnetic Unmanned Robot Applied to Automotive Test Based on Improved Smith Predictor Compensator

A new control method for an electromagnetic unmanned robot applied to automotive testing (URAT) and based on improved Smith predictor compensator, and considering a time delay, is proposed. The mechanical system structure and the control system structure are presented. The electromagnetic URAT adopts pulse width modulation (PWM) control, while the displacement and the current doubles as a closed-loop control strategy. The coordinated control method of multiple manipulators for the electromagnetic URAT, e.g., a skilled human driver with intelligent decision-making ability is provided, and the improved Smith predictor compensator controller for the electromagnetic URAT considering a time delay is designed. Experiments are conducted using a Ford FOCUS automobile. Comparisons between the PID control method and the proposed method are conducted. Experimental results show that the proposed method can achieve the accurate tracking of the target vehicle's speed and reduce the mileage derivation of autonomous driving, which meets the requirements of national test standards.

Control of virtual power plant in microgrids: a coordinated approach based on photovoltaic systems and controllable loads

Renewable energy sources (RESs) such as solar energy are cost-effective to meet part of the energy needs. However, the inherent fluctuation and intermittence of RESs may deteriorate the stability and security of power grids. Energy storage systems can mitigate the problem, but they are very expensive. For this reason, a coordinated control method of virtual power plant (VPP), which includes photovoltaic systems (PVs) and controllable loads, is proposed in this study so that the aggregated power output of the VPP can be flexibly adjusted in a wide range. To achieve this, power output of the PVs and operational modes of controllable loads are coordinated by solving a mixed integer programming (MIP) problem. Meanwhile, with a quadratic interpolation based active power control strategy, each PV can operate in a power dispatch mode and simultaneously estimate its maximum available power, which is an input to the MIP problem. Externally, the VPP can quickly adjust the aggregated power and achieve functions important to power systems with high penetration of distributed energy resources, such as primary frequency regulation. Simulation results validate the effectiveness of VPP in providing frequency support to an island microgrid.

직류형 마이크로그리드의 전운전영역을 고려한 협조제어

Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

비상상태 전압제어를 위한 무효전력보상설비의 최적 운용

This paper proposes a method for solving running cost problem by minimizing switching reactive power compensation devices. An objective function was modeled by calc ulating the weighting value of cost, and a solution was derived using ILP. This paper suggests optimal coordinative control method between FACTS, Shunt Reactors, Capacitors and OLTC. Therefore, it is valuable for decision maker in determini ng order and capacity of devices which gaining a voltage stabilization. As a result, the objectives of voltage stabiliza tion and cost minimization were achieved simultaneously. This realizes the economic efficiency of the system. We start by showing how to solve systems of linear equations using the language of pivots and tableaus. The effectiveness of this technique is demonstrated in modified PSS/E MIGUM 45 bus system. The simulation results show the effectiveness of this algorithm by comparing the outcome withseveral established methods.

Coordinated operation of wind power and other resources considering power system requirements

Wind power is inherently variable, and thus it brings significant challenges to the operation of electric power systems. Noting that there really exist many controllable and dispatchable resources in power systems, the coordination of wind power and these resources provides the possibility of overcoming the drawbacks of wind power. This paper discusses the determination of the coordination objectives of wind power and other resources. The key idea is that the coordination objectives should match with the operation requirements of real power systems. (1) For an integrated wind plant, the coordination objective is that the output of wind plant should meet the grid code requirement. In this regard, a coordinated control method of a wind-energy storage system to meet the ramp rate limit of grid code is proposed. (2) For an area with a high penetration of wind power, the coordination objective is that the output of regional hybrid system should contribute to the active power balance of the whole power system. In this regard, a coordinated dispatch method of wind-thermal-pumped hydro hybrid system (regional hybrid system) to make the combined output follow the trend of system load is established. Case studies are conducted to verify the feasibility of the proposed methods.

Coordinated Voltage Control of Weak Sub-transmission Networks Considering Wind Power Variability

In this paper, a novel coordinated control method is proposed to handle the negative voltage impacts on weak sub-transmission systems, which are caused by wind power fluctuations. Firstly, wind variations are divided into large and small fluctuations. Then, according to the different control characteristics of on-load tap changers (OLTCs) and static compensators (STATCOMs), the OLTCs are used to minimize the impacts caused by large fluctuations, while the STATCOMs are used to eliminate the impacts introduced by small fluctuations. The model predictive control (MPC) and a consensus based distributed control techniques are adopted to design the control schedules of OLTCs and STATCOMs, respectively. It is shown that by the coordination of OLTCs and STATCOMs, voltage violations of points of interconnection (POIs) are eliminated, and voltage fluctuations at unregulated load buses are mitigated. The effectiveness of our proposed control scheme is presented through a case study on the modified IEEE 14-bus test system with a real wind power profile. According to the simulation results, it turns out that the proposed approach can reduce the operation number of OLTCs significantly, and decrease the required capacity of STATCOMs dramatically by comparison with the existing control scheme.

Optimization Method of Intersection Signal Coordinated Control Based on Vehicle Actuated Model

Traditional timing green wave control with predetermined cycle, split, and offset cannot adapt for dynamic real-time traffic flow. This paper proposes a coordinated control method for variable cycle time green wave bandwidth optimization integrated with traffic-actuated control. In the coordinated control, green split is optimized in real time by the measured presence of arriving and/or standing vehicles in each intersection and simultaneously green waves along arterials are guaranteed. Specifically, the dynamic bound of green wave is firstly determined, and then green early-start and green late-start algorithms are presented respectively to accommodate the fluctuations in vehicle arrival rates in each phase. Numerical examples show that the proposed method improves green time, expands green wave bandwidth, and reduces queuing.

Vehicle stability and attitude improvement through the coordinated control of longitudinal, lateral and vertical tyre forces for electric vehicles

Advanced electric vehicles equipped with independent electric driving/braking, steering and active suspension systems provide potential for optimal vehicle performance by accurate and independent control of each longitudinal, lateral and vertical tyre force. However, the lack of an effective method for the optimisation and control of tyre forces has restricted the development of this research field. In this paper, a novel method for the coordinated control of longitudinal/lateral/vertical tyre forces is proposed by solving a non-convex optimisation problem. A unified objective function that combines the tyre workload and the dynamic ratio of the vertical forces is developed. Thirty-six constraints, including driving demands, electric actuator characteristics and tyre friction limitations, are considered. An optimisation algorithm that combines constrained optimisation and feasible region planning is proposed. Finally, simulations and experiments using a driver simulator are conducted, which demonstrate that the proposed coordinated control method simultaneously improves handling stability and controls vehicle attitude effectively.

Research on automatic loading & unloading technology for vertical hot ring rolling process

The automatic loading & unloading technology is the key to the automatic ring production line. In this paper, the automatic vertical hot ring rolling (VHRR) process is taken as the target, the method of the loading & unloading for VHRR is proposed, and the mechanical structure of loading & unloading system is designed, The virtual prototype model of VHRR mill and loading & unloading mechanism is established, and the coordinated control method of VHRR mill and loading & unloading auxiliaries is studied, the movement trace and dynamic characteristic of the critical components are obtained. Finally, a series of hot ring rolling tests are conducted on the VHRR mill, and the production rhythm and the formed rings' geometric precision are analysed. The tests results show that the loading & unloading technology can meet the high quality and high efficiency ring production requirement. The research conclusions have practical significance for the large-scale automatic ring production.

Coupling dynamics modelling and optimal coordinated control of tethered space robot

Tethered space robots use tethers to replace rigid arms and have more flexibility than a traditional space robot, which gives it wide application prospect in future on-orbit servicing missions. Before carrying out elaborate manipulations, tethered operation robots need to approach the target. In order to save fuel in the approaching phase, various coordinated control methods that employ tethers and thrusters together are investigated in the literature. However, the increasing mass of the tether and the distributed force acting on the tether will affect the position and attitude of the robot, which is neglected in previous studies and can degrade the performance of the control system. Here, in order to involve these factors, coupled dynamics and coordinated control theories are combined and applied. Firstly, a coupling dynamics model for the tethered space robot system is built based on the Hamilton principle and the linear assumption. Then, based on the dynamics model, we design an optimal coordinated controller which can minimize the fuel consumption by using the hp-adaptive pseudospectral method and the classical PD controller. Finally, the advantages of the proposed method and the performance of the designed controller are validated by the numerical simulation.

Coordinated control method of space-tethered robot system for tracking optimal trajectory

Space-tethered robot system is a new kind of space robot, which consists of a robot platform, space tether, and operation robot. This paper presents the coordinated control method in order to save thruster fuel of operation robot in the process of tracking the optimal approach trajectory. First, the optimal approach trajectory of an operation robot is designed using the Gauss pseudospectral method, which resulted in continuous optimal control force using the Lagrange interpolation scheme. The optimal control force is optimized and distributed to space tether and thrusters through simulated annealing algorithm in discrete points, which minimized fuel consumption of thrusters. The distributive continuous force is obtained via cubic polynomial fitting of optimal distributive force in 0.1s discrete time point. To tracking the optimal trajectory, Fuzzy Proportional-Derivative controller is designed with the help of optimal distribution force which come from optimization model. Simultaneously, the relative attitude of the operation robot is stabilized using attitude time-delay algorithm through the reaction wheels. Numerical results are presented, demonstrating the validity of saving thruster fuel and well performance in tracking the optimal trajectory.

Optimal coordinate operation control for wind–photovoltaic–battery storage power-generation units

An optimal coordinate operation control method for large-scale wind–photovoltaic (PV)–battery storage power generation units (WPB-PGUs) connected to a power grid with rated power output was proposed to address the challenges of poor stability, lack of decision-making, and low economic benefits. The “rainflow” calculation method was adopted to establish the battery cycle life model and to calculate quantitatively the life expectancy loss in the operation process. To minimize unit cost of power generation, this work optimized the output period of the equipment and strategy of battery charging and discharging with consideration of working conditions, generation equipment characteristics, and load demand by using the enhanced gravitational search algorithm (EGSA). A case study was conducted on the basis of data obtained using WPB-PGU in Zhangbei, China. Results showed that the proposed method could effectively minimize the unit cost of a WPB-PGU under different scenarios and diverse meteorological conditions. The proposed algorithm has high calculation accuracy and fast convergence speed.

Multi-Index Nonlinear Coordinated Control of TCBR and Hydro-Generator Excitation

As a new FACTS device, thyristor controlled braking resistor (TCBR) is one of the effective devices to enhance transient stability of generator. In this paper, a coordinated controller for TCBR and hydro-generator excitation system with the multi-index nonlinear coordinate control method based differential geometry theory is proposed. By means of Hartman-Grobman theorem, differential geometry multi-index nonlinear control (DGMINC) design method can reassign the closed-loop system eigenvalues of linear approximate system to the nonlinear system via appropriately selecting output function parameter matrix. Therefore, the system can get good control performance. The simulation results show that TCBR and generator excitation system controlled by this coordinate control strategy can decrease the generator acceleration area rapidly when the severe fault occurred and increase deceleration area significantly after the fault is cleared. So that, power system transient stability limitation improved significantly.

Distributed Model Predictive Control Method for Optimal Coordination of Signal Splits in Urban Traffic Networks

AbstractCoordination and control approaches based on model predictive control (MPC) have been widely investigated for traffic signal control in urban traffic networks. However, due to the complex non‐linear characters of traffic flows and the large scale of traffic networks, a basic challenge faced by these approaches is the high online computational complexity. In this paper, to reduce the computational complexity and improve the applicability of traffic signal control approaches based on MPC in practice, we propose a distributed MPC approach (DCA‐MPC) to coordinate and optimize the signal splits. Instead of describing the dynamics of traffic flow within each link of the traffic network with a simplified linear model, we present an improved nonlinear traffic model. Based on the nonlinear model, an MPC optimization framework for the signal splits control is developed, whereby the interactions between subsystems are accurately modeled by employing two interconnecting constraints. In addition, by designing a novel dual decomposition strategy, a distributed coordination algorithm is proposed. Finally, with a benchmark traffic network, experimental results are given to illustrate the effectiveness of the proposed method.

A Coordinative Steering Control Method Based on PID Compensation for an Electric Vehicle

This paper presents a coordinating steering control method in an Electric Vehicle with Four-in-Wheel-Motors Drive and Four-Wheel Independent Steering. This control method applied a PID compensation to solve the absonant steering problem. This research builds a mathematic model for the control system and uses the Matlab simulation to verify the feasibility and control effect. Then it is applied in a real car environment for further experiment in which the paper studies the control effect with varied control parameters. According to the analysis of the experiment, a practical solution for steering System is proposed with excellent control effect.

A Coordination Control Method of Generator Out-of-Step Protection Based on WAMS Transient Stability Prediction

The construction of ultra-high voltage grid and the input of large generating units make the out-of-step protection become increasingly important. Traditional out-of-step protection device can only judge from local perspective, no consideration to the global situation. In order to solve this problem, a coordination control method of generator out-of-step protection based on WAMS transient stability prediction is proposed, the coordination between grid side out-of-step protection and the generator out-of-step protection is achieved. Using the self-memory trajectory to predict the stability of grid, calculate excess energy of system based on EEAC theory, and utilize convexity-concavity of phase diagram method which is not affected by the change of network structure to judge the stability of system. Utilize double forecast strategy to improve the stability of the system further.

Modeling and Simulation of Urban Arterial Traffic Signal Coordinated Control

Traffic congestion is a major concern for many cities throughout the world. Developing a sophisticated traffic monitoring and control system would result in an effective solution to this problem. In order to reduce traffic delay, a novel urban arterial traffic signal coordinated control method is presented. The total delay of downstream and upstream vehicles is considered and the function describing the relationship between vehicles delay and signal offset among intersections is established. Finally, comparing the performance of traffic signal under method proposed in this paper with the traditional isolated traffic signal control method, the microscopic simulation results show that the method proposed in this paper has better performance in the aspect of reducing the vehicles delay. The offset model is tested in a simulation environment consisting of a core area of three intersections. It can be concluded that the proposed method is much more effective in relieving oversaturation in a network than the isolated intersection control strategy.