Coordinated Control Method Research Articles

Interacting multiple model state observer-based coordination control of electro-hydraulic composite electronic stability program

In this paper, an electro-hydraulic electronic stability program composite control method is proposed for electric wheeled vehicles based on interacting multiple model state observer. Hydraulic system model, electric-driving wheel model, 2-degrees-of-freedom vehicle reference model and 7-degrees-of-freedom vehicle model are established at the beginning. The necessary state estimations and calculations are also accomplished utilising interacting multiple model unscented Kalman filter. Then, the proposed upper controller calculates the additional yaw moment by fuzzy sliding mode control, and the lower controller distributes the longitudinal force and additional yaw moment based on the quadratic programming optimisation allocation to improve the vehicle handling stability. Finally, using Simulink and CarSim, a joint simulation test platform is established. The simulation results show that the state observer can estimate the driving state parameters accurately enough under various conditions, and coordination control method mentioned in this paper can significantly improve the electric wheeled vehicle's handling stability under extreme conditions.

Enhanced Low-Voltage Ride-Through Coordinated Control for PMSG Wind Turbines and Energy Storage Systems Considering Pitch and Inertia Response

Low-voltage ride-through (LVRT) requirements are defined by grid operators, and they vary based on power system characteristics. Coordinated LVRT control methods have been proposed for wind turbines (WTs) and energy storage systems (ESSs). ESSs can successfully help achieve LVRT by regulating DC-link voltage during a grid fault. During LVRT, WTs cannot transfer power to a grid because of their low voltage and current limit. Moreover, as grid operators typically require reactive power support during a grid fault, active power cannot be properly transferred to the grid. This results in fluctuation in the DC-link voltage in wind power generators and it can induce significant damage in the systems. ESS have been used for achieving better LVRT response to protect WT systems and meet LVRT grid requirements. Previous coordinated control methods have mainly focused on DC-link voltage regulation based on ESS charging and discharging control. As ESSs have high installation cost and limited charging capacity, it is better to coordinate the LVRT response properly considering the state of charge of ESSs and the rotor speed and pitch angle of WTs. In this work, an enhanced coordinated LVRT control method is proposed based on a fuzzy-logic algorithm. Fixed torque of the rotor control and a fixed ramp rate of the pitch control are employed for power analysis which is used in formulating fuzzy-logic controller. The effectiveness of the proposed method is validated by modeling a WT and an ESS topologically and performing simulations using the MATLAB/Simulink SimPowerSystems toolbox.

Research on Reactive Power and Voltage Control for Wind Farm Based on coordinate control of DFIGs and SVG

Abstract Wind farm generally uses long-distance transmission mode to transmit electricity, because the grid can not fully support the grid voltage of wind farm. When the wind speed changes, there is a problem of voltage instability at the grid-connection point. However, the reactive power compensation device of the power grid can not meet the requirements of fast reactive power response and compensation. Although doubly-fed induction generators (DFIGs) have fast power decoupling control, its reactive power is limited by active power output. In order to meet the reactive power demand of the power grid, the instability of the voltage at the grid-connection point is solved by coordinating the reactive power output capacity of DFIGs and the Static Var Generator (SVG). This paper proposes a coordinated control method of reactive voltage in wind power plant based on Starsim, which uses the upper computer to send voltage control instructions to control the reactive output of the simulation model in Starsim. The simulation model is built in MATLAB, and the simulation model is put into Starsim. Through the simulation, it is concluded that the control method could stabilize the grid voltage of wind farm.

Coordinated Optimal Control of Multiple Reactive Power Devices at Different Voltage Levels in UHVDC Near Zone

Affected by different steady-state reactive power output ratios among generators, capacitors and other reactive devices in the end-to-end power grid, voltage collapse may occur due to the failure of the receiving-end AC system, and the problem of voltage stabilization in multi-DC feed systems is particularly common. For suppressing voltage collapse, sufficient dynamic reactive power support is an effective measure, and there are some differences in the dynamic support effect of different reactive power sources. The dynamic reactive power response of the generator and its reactive power margin are two important factors affecting the coordination and optimization of the reactive power of the generator. The comprehensive evaluation index is adopted to optimize the sequencing of the reactive power output of the generator near the DC drop point. A coordinated control method of dynamic and static reactive power for DC near-point systems at different voltage levels is proposed. By controlling the steady-state reactive power output ratio between multiple reactive devices, the node voltage is maintained near the target value, and reactive power control schemes at different voltage levels can be given to meet load changes. Finally, taking the actual situation of Central China Power Grid as an example, the results of different reactive voltage control strategies are compared and analyzed, which proves that the coordinated control strategy of multiple reactive power devices can significantly improve the stability of the receiving grid voltage.

Research on Hybrid Energy Hierarchical Coordination Control Method for Grid-connected Micro-Grid

In order to effectively solve the problem that it is difficult to coordinate the operation state of grid-connected micro-grid, a hierarchical coordinated control method of hybrid energy in grid-connected micro-grid is proposed. The mathematical model of the relationship between system power and cost function and the hierarchical model of micro-grid are established. As optimisation objectives are provided by constructing objective functions, the information exchange and energy control between the systems are used to realise the grid connection. Simulation results show that the frequency of the proposed method is always around 50HZ, which is the closest to the planned value. The difference between the power value and the planned value is less than 1 kW, which is more in line with the actual needs than other methods. It is proved that this method can effectively control energy and ensure the smooth operation of micro-grid.

Coordinated Fuzzy-Based Low-Voltage Ride-Through Control for PMSG Wind Turbines and Energy Storage Systems

Coordinated control methods involving a wind turbine (WT) and an energy storage system (ESS) have been proposed to meet several objectives, such as smoothing wind power (WP) fluctuations, shaving peaks, enabling power scheduling, and allowing low-voltage ride-through (LVRT). LVRT requirement is defined by grid operators, and it should be satisfied whenever grid faults occur. Several methodologies have been proposed for the LVRT both with or without the use of an ESS. Furthermore, using an ESS is more advantageous for several WP applications. By using an ESS, WTs can be operated in a more economic and reliable way. However, the installation cost of an ESS is high and it has operation range constraints for charging and discharging. Moreover, the WT operation condition and ESS state-of-charge (SoC) can be different when a grid fault occurs. Therefore, it is necessary to coordinate both units, WT and ESS, for reliable and economic operation during a grid fault. Thus, we propose a coordinated fuzzy-based LVRT method that considers the different operation conditions of a WT and an ESS. From the proposed method, the effective reference powers of a WT and an ESS are evaluated by considering the rotor speed and SoC in the fuzzy control algorithm. The effectiveness of the proposed method is validated by considering two case studies on ESS SoC and WT rotor speed violations.

Trajectory planning and robust tracking control for a class of active articulated tractor-trailer vehicle with on-axle structure

Traditional articulated vehicles exhibit poor steering performance since there exist no direct rotating moment for the underactuated trailers, which cause such vehicles nearly cannot work well in the narrow space. To overcome this shortcoming associated with the traditional articulated vehicles, an active articulated structure is proposed, in which a steering motor is introduced at the articulated joint of tractor and trailer, in addition to utilizing mecanum wheels as trailer wheels. On the basis of this structure, a coordinated control method is designed to ensure the vehicle kinematics constraints and dynamic maneuverability. The coordination control consists of two level controllers. On the level of kinematics, model predictive control (MPC) is adopted as posture controller, which can solve the non-holonomic problem of the whole active articulated tractor-trailer vehicle system; On the dynamic level, a sliding mode control (SMC) is introduced to design a dynamic controller to track the desired velocities generated online, which can increase the robustness of the system. The simulation results show that the proposed active articulated tractor-trailer vehicle system has better maneuverability compared with the traditional one, and the proposed control strategy can ensure the required control effect.

Inverter-Based Voltage Control of Distribution Networks: A Three-Level Coordinated Method and Power Hardware-in-the-Loop Validation

The reactive power of the photovoltaic (PV) inverters has great potential for voltage regulation of distribution networks. In this paper, a new three-level coordinated control method for PV inverters is proposed to address network voltage fluctuation and violation issues. In Level I, a ramp-rate control is designed to smooth the network voltage fluctuations, while in Level II, a droop control is designed to alleviate the network voltage deviations. If the local compensation provided by Level I and II is not enough to regulate the network voltages within the required limits, the Level III control based on dynamic average consensus can respond and share the reactive power requirement among other inverters in a distributed way. The proposed control method can smooth the voltage profiles, restrain the voltage rise/drop problem, and coordinate all PV inverters in real-time when there is no feasible local solution. The stability analysis of the proposed three-level coordinated control for network voltage regulation is provided. The power hardware-in-the-loop (PHIL) experiment has been conducted for validating the proposed control method under various scenarios.

An improved coordination method of multi-terminal MMC-HVDC system suitable for wind farm clusters integration

With the continuous expansion of wind farm clusters, the multi-terminal modular multilevel converter based high voltage direct current (MMC-HVDC) transmission has been employed for wind power delivery. To improve the control flexibility, dynamic voltage adjustment speed and rationality of power allocation, various coordination control methods have been recently investigated in multi-terminal MMC-HVDC transmission system. An attempt is made in this paper to contribute to the optimization of coordination control in the multi-terminal MMC-HVDC system connected to wind farms. Based on the analysis of DC voltage, power deviation and droop coefficient, an improved droop control strategy with adjustable coefficients is first proposed and thereby applied to multi-terminal MMC-HVDC transmission system with wind farm clusters. Arguably, the droop coefficient correction should be an effective method for optimizing power allocation and reducing DC voltage deviation between the receiving converters. In addition, a lag compensator is introduced to improve the response speed of the inner loop controller when the improved droop control is adopted. Furthermore, the influence of droop coefficients on the stability of the control system is discussed, and the dynamic response of the improved control system is also analyzed under the different droop and time coefficients, which can provide guidelines for the control optimization of multi-terminal MMC-HVDC system. Finally, a model of a five-terminal MMC-HVDC transmission system is built based on the RT-LAB simulator, and the simulation results show that the proposed method can not only optimize the voltage control and power allocation, but also improve the system response speed.

A Robust Optimal Coordinated Droop Control Method for Multiple VSCs in AC–DC Distribution Network

AC–DC hybrid distribution network is viewed as a featured system to efficiently connect to all kinds of power sources and loads. In order to improve the system robustness, adapting to random fluctuations of renewable energy sources, this paper proposed a robust optimal coordinated control method for multiple voltage source converters (VSCs) in AC–DC distribution network. A robust optimization model was established to co-optimize the slopes of active and reactive power droop control of VSCs with the aim to minimize the total network loss, while ensuring the system security. VSC capacity coupling and power flow constraints were both considered. Then, to enhance the computational tractability of the problem, based on the column-and-constraint generation algorithm, ${V^2} - P$ and ${V^2} - Q$ were implemented in the droop control schemes holding the linear feedback characteristic so that the non-convex max–min sub-problem can be transformed into a mixed integer second-order cone (SOC) programming problem. Furthermore, to increase the accuracy of SOC relaxation in the sub-problem, a current limit strategy was designed where the maximum possible network loss was pre-identified to restrain the feasible range of branch current. Numerical experiments suggest that the proposed coordinated control method can improve the system security with little extra economic cost, and the reliability of the results is enhanced by the proposed current limit strategy.

Improved Coordinated Control of Standalone Brushless Doubly Fed Induction Generator Supplying Nonlinear Loads

This paper proposes an improved coordinated control of standalone brushless doubly fed induction generator (BDFIG) supplying nonlinear loads. Due to the existence of nonlinear loads, the voltage at the point of common coupling becomes distorted with a large number of low-order harmonics, which severely degrades the performance of power generation systems. In order to eliminate the included low-order harmonics, a coordinated control method of harmonic mitigation has been presented in this paper for the control of both machine side and load side converters. Then, a weight factor is introduced to the proposed control method for distributing the contribution of harmonic mitigation between the two converters. Comprehensive experimental results on a 30 kVA BDFIG are presented to verify the proposed control method.

Coordination and Optimization of Urban Traffic Control and Path Guidance Based on Multi-Agent

With the development of society, the urbanization process is accelerating, the urban population is growing rapidly, and the traffic problems are becoming more and more prominent, which seriously affects the normal operation of the city. Transportation is the lifeblood of the city. Scientific management and control is an important way to improve the efficiency of urban traffic operation, and it is also an important symbol of urban transportation modernization, informationization and intelligence. This paper aims to study the new coordinated control method of traffic signals. Different from the traditional coordinated control method of centralized control and hierarchical control, a multi-agent distributed traffic signal coordination control system is established, which distributes the main functions of signal control to Signal control agents at various intersections reduce to the complexity of the control algorithm and improve the reliability and intelligence of the system.

Coordinated control of stability and economy based on torque distribution of distributed drive electric vehicle

The torque distribution strategy of distributed drive electric vehicle is only aimed at safety or economy. A multi-target coordinated control method considering stability and economy is proposed to solve the problem of single torque distribution target, which consists of a coordination decision controller, a high-level motion controller, and a low-level allocation controller. The coordination decision controller based on the phase plane method determines whether to adopt a stability or economic control strategy. The high-level motion controller consists of a bicycle model with 2 degree of freedom, a speed tracking controller, a stability controller, and an economic controller to calculate the desired direct yaw moment of the four in-wheel motors. The stability controller based on the fuzzy algorithm tracks the desired vehicle side slip angle and yaw rate calculated by the bicycle model with 2 degree of freedom to control vehicle stability. The economical controller based on a multi-motor loss model optimizes the efficiency of the vehicle’s drive system. The low-level allocation controller is presented to provide optimally distributed torques for each wheel. Finally, the simulation and hardware-in-the-loop testing show that the coordinated control strategy can effectively improve the stability and economy of the distributed drive electric vehicle.

Coordinated control method of active and reactive power for voltage regulation in distribution systems with high-penetration PV

Owing to the intermittent and randomness of solar radiation, high-penetration photovoltaic (PV) energy injected into power distribution systems will inevitably change the magnitude and direction of the power flow, thus causing problems such as voltage violation of the point of common coupling (PCC) and further having a hazardous influence on consumers’ electricity quality. And the communication construction of China’s distribution systems is now relatively weak, difficultly integrating multiple voltage regulation equipment. To improve consumers’ voltage quality at the PCC, a coordinated control method based on active and reactive power of local inverter is proposed. This method can realize the economic regulation of the voltage at the PCC through reactive compensation and active reduction, which can maximumly assure the voltage magnitude at the PCC within limits (including upper and lower limits) and maximize the utilization capacity of PV inverter. Based on Matlab/Simulink, simulation results in different scenarios show the effectiveness of the proposed method.

Coordinated flight control of miniature fixed-wing UAV swarms: methods and experiments

In this paper, we present our recent advances in both theoretical methods and field experiments for the coordinated control of miniature fixed-wing unmanned aerial vehicle (UAV) swarms. We propose a multi-layered group-based architecture, which is modularized, mission-oriented, and can implement large-scale swarms. To accomplish the desired coordinated formation flight, we present a novel distributed coordinated-control scheme comprising a consensus-based circling rendezvous, a coordinated path-following control for the leader UAVs, and a leader-follower coordinated control for the follower UAVs. The current framework embeds a formation pattern reconfiguration technique. Moreover, we discuss two security solutions (inter-UAV collision avoidance and obstacle avoidance) in the swarm flight problem. The effectiveness of the proposed coordinated control methods was demonstrated in field experiments by deploying up to 21 fixed-wing UAVs.

Coordinated control method of intersection traffic light in one-way road based on V2X

One-way roads have potential for improving vehicle speed and reducing traffic delay. Suffering from dense road network, most of adjacent intersections' distance on one-way roads becomes relatively close, which makes isolated control of intersections inefficient in this scene. Thus, it is significant to develop coordinated control of multiple intersection signals on the one-way roads. This paper proposes a signal coordination control method that is suitable for one-way arterial roads. This method uses the cooperation technology of the vehicle infrastructure to collect intersection traffic information and share information among the intersections. Adaptive signal control system is adopted for each intersection in the coordination system, and the green light time is adjusted in real time based on the number of vehicles in queue. The offset and clearance time can be calculated according to the real-time traffic volume. The proposed method was verified with simulation results by VISSiM traffic simulation software. The results compared with other methods show that the coordinated control method proposed in this paper can effectively reduce the average delay of vehicles on the arterial roads and improve the traffic efficiency.

Research on the Coordinated Control of the True Bipolar VSC-HVdc Grid Based on Operating Point Optimization

The voltage source converter based high voltage direct current transmission system with the true bipolar wiring mode features higher flexibility and reliability, yet it cannot be without a proper and effective coordinated control strategy, which is the key to the safe and reliable operation of the system as well as the effective and full utilization of renewable energy on a large scale. A step further from the conventional droop control strategy, the coordinated control strategy based on operating point optimization is proposed in this paper. This paper first illustrates and examines the coordinated control method at the system level in view of special wiring and control modes; it then looks into the method of operating point optimization seeking to achieve both safe and cost-effective operation; and the paper finally demonstrates the effectiveness of the coordinated control strategy verified by MATLAB and PSCAD simulations from the perspective of system operating point deviation, security, and cost-effectiveness.

Study on Coordination Control of Subcritical Circulating Fluidized Bed Units with Win-Win Source Network

Aiming at the large delay and inertia characteristics of circulating fluidized bed units, a coordinated control method of circulating fluidized bed units under the CPS evaluation system of power grid is proposed. Firstly, starting from the power grid performance evaluation index CPS, the formation characteristics of regional control error ACE in the CPS index are analyzed. Then, according to the operation characteristics of circulating fluidized bed units, the feasibility of realizing the boiler-turbine-grid coordinated control system is revealed. Then, the switch controller based on the energy state of the boiler and the optimal controller based on CPS standard are designed to realize the boiler network. Finally, through simulation experiments, it is verified that the proposed control methods not only meets the requirements of power grid for unit evaluation better, but also takes into account the overall energy state of the boiler to improve the control performance of main steam pressure, and achieves the win-win control effect of circulating fluidized bed units and power grid.

Large Scale Renewable Energy Integration: Issues and Solutions

In recent years, many applications have been developed for the integration of renewable energy sources (RES) into the grid in order to satisfy the demand requirement of a clean and reliable electricity generation. Increasing the number of RES creates uncertainty in load and power supply generation, which also presents an additional strain on the system. These uncertainties will affect the voltage and frequency variation, stability, protection, and safety issues at fault levels. RES present non-linear characteristics, which requires effective coordination control methods. This paper presents the stability issues and solutions associated with the integration of RES within the grid.

A Coupled Virtual Impedance for Parallel AC/DC Converter Based Power Electronics System

In this paper, a coordinated control method is proposed for three-phase ac/dc hybrid microgrid power electronic interlinking unit with dual converters sharing both dc and ac links. Unlike the conventional dual converters-based system where the same control strategy is applied to both converters, converter1 in this proposed system is controlled by a closed-loop current regulation algorithm while converter2 employs voltage controller with coupled adaptive virtual impedance. With the flexible control of the coupled virtual impedance, the system performance is enhanced in the following three aspects. First, in grid-tied operation mode, the output power difference between dual converters is used as an input to tune the coupled virtual impedance of converter2 for a rapid dynamic power response. Second, the proposed coordinated control with inherent voltage support is able to achieve a seamless transfer without additional efforts. Third, during system islanded operation, a generalized power sharing and an active PCC voltage harmonic and unbalanced components mitigation are achieved via the adjustment of the coupled virtual impedance. Finally, the scalability of the proposed method in a system with more converters is briefly discussed and verified.