Double Loop Control Research Articles

The Model of Distributed Grid-Connected DC Micro Network Inverters and Double Loop Control Method

In this paper, for parallel operation of the three-phase PWM inverter control system, we put forward and set up the equivalent grid inverter mathematical model. In the process of grid inverter equivalent model is discussed, for the three-phase inverter system is a nonlinear system, in order to facilitate the performance of the system analysis and design of the control system, the transfer function of the system were analyzed to the linearized system. After the linearization control the theory system can be discussed using the method of classical. On the premise of system average model we get the static working point system, according to the law of small signal, we can obtain the small signal mathematical model .At the same time, discusses the three phase inverter design of double loop control system.

Application and Simulation of SVPWM Control Techniques in Three-Phase PV Grid-Connected Inverter

The space vector pulse width modulation (SVPWM), as a new kind of vector control technique, has the advantages of high voltage utilization, less distorted output, simple control method, etc. In this paper, the control technique is applied to three-phase photovoltaic (PV) grid-connected inverter system. It uses double loop control method combined with PI control technique. The simulation model of PV grid-connected inverter system is established in Matlab/Simulink. The simulation results show that the application of SVPWM technique effectively improves the dynamic performance of PV grid inverter system and the THD of grid-connected current is low.

Control Strategy for Shunt Active Power Filters with Selective Harmonic Compensation

To improve the flexibility of compensation and the precision of three-phase shunt active power filter (APF). A double-loop compound current controller was proposed, which repetitive controller as the outer loop, the PI controller as the inner loop. Design method in detail, dynamic response and steady-state characteristic in analysis. And put forward the compound control strategy, which combine selective harmonic detection based on multiple synchronous rotating coordinates with double-loop compound controller, achieved the compensation of zero steady-state error and selective harmonic currents. Both simulation and experimental results verify the effectiveness and correctness of the content.

Research on the Double-Loop Robust Control Technology for the Electric-Hydraulic Servo System

With the electro-hydraulic servo mechanism is more and more widely used in aerospace, manufacturing industry and agricultural machinery, its control performances are required by process environment with more and more expectations, which include increasing response speed and improving tracking accuracy. Because the traditional PID controller possesses large overshoot, long conversion time, bad robustness and other shortcomings, the double-loop robust control algorithm is proposed. Simulation results show that, compared with traditional PID control scheme, the proposed control scheme can achieve accurate tracking of electro-hydraulic servo system quickly. Therefore, it enhances product performance, optimizes the design process, and also possesses a high application value.

Research on TZSI Control Method

In transformer-Z-source inverters (TZSI), the impedance networks consist of a transformer and one capacitor. While maintaining the main features of traditional Z-source network, the new networks exhibit some unique advantages, such as the increased voltage gain and reduced voltage stress in the voltage-fed TZSI, when the turns ratio of the transformer windings is over 1. This paper contributes to the ac small signal modeling and analysis of TZSI in continuous conduction mode. The ac small signal model considers the dynamics introduced by network uniquely contained in TZSI. And a double loop control method which is impedance source network output dc voltage and current loop has been proposed to realize the control of TZSI. Results of simulations and experiments are used to validate the control method and show that this method is correct and feasible.

The Grid-Connected Inverter of Simulation on Direct-Drive Wind Power System Based on MATLAB

Based on working Principle of the direct-drive wind power systems grid-connected inverter was research, the mathematical model for inverter in Three-phase rotating coordinate was established and analyzed. A double-loop control strategy that based on feed forward decoupling were introduced, Meanwhile, combining the implementation effective control of the AC-side output current by the Space Vector Pulse Width Modulation method (SVPWM), it could generate sine wave current that had the same frequency and the same phase with network voltage. To a great degree, reduced harmonic pollution in power system, moreover, improved the Grid-connected wind power systems efficiency and reliability.

Design of the Double Loop Control Grid-Connected Filter Based on Virtual Resistance

An improved control algorithm of repetitive controller based on virtual resistance was proposed to solve the problem of the slow dynamic response and the high total harmonic distortion (THD). The proportional-integral controller (PI controller) can not only adjust rapidly but also eliminate residual error effectively and the repetitive controller can eliminate periodic interference signal effectively. The double loop control combined with PI control and repetitive control. The controller has been used to control the inverter in grid-connected section which can improve the regulating speed and system stability. It can also achieve fairly good control effect under the circumstances of mutations of voltage and load. By designing the parameters of the controller, THD of the grid-connected current is lower than 0.61%. The simulation result shows that the algorithm is correct and feasible.

Simulation Study of Permanent Magnet Synchronous Motors Energy Feedback Control System

Combined with the brake working principle of Permanent magnet synchronous motors, the three-phase PWM rectifier mathematical model and Simulink simulation model are set up. On this basis, according to the design requirements of energy feedback system, the voltage current double-loop control is applied in this system. The space voltage vector tracking is achieved by the use of space voltage vector PWM algorithm. The system modeling and simulation study is conducted in the MATLAB simulation environment, and the correctness of the proposed program is verified, which provides the corresponding theoretical basis for the future product design.

Study on Improvement Transient Stability of the Large-Scale Wind Farms Integration with STATCOM

In view of a serious threat for the transient stability of the power system being caused by the large-scale wind farms integration, and combining with advantages of STATCOM which can quickly restore the fault voltage and fastly, flexibly and smoothly compensate the reactive power, a method is proposed using STATCOM controller of to improve transient stability of the power system integrated by large-scale wind farms. The control strategy of the STATCOM controller uses adaptive double loop control. The role of the device to improvement transient stability of the power system is studied under the condition of serious fault. by simulation comparison with the condition without STATCOM controller installed at the same place. The simulation results show that the STATCOM controller can clearly improve transient stability of the power system integrated by large-scale wind farms.

Fault current contribution scenarios for grid-connected voltage source inverter-based distributed generation with an LCL filter

Inverter-based distributed generation (IBDG) is characterized by its negligible fault current contribution compared with synchronous generators due to its inherent non-overload capabilities. Thus, IBDG hardly affects the fault current level; this shadows the conventional protection schemes resulting in improper system protection especially with a high penetration of IBDGs at high power levels and/or in island operation mode. This paper presents an experimental investigation of two scenarios for IBDG fault current contribution under different fault conditions. In the first scenario, the inverter is controlled to produce zero output current or is disconnected upon fault occurrence, which is the case for most commercial grid-connected inverters. In the second scenario, the inverter contributes its rated current to the fault. The practical selection may be questionable and is affected by the fault level, employed protection scheme, and the penetration level of IBDGs. The introduction of double-loop proportional-resonant (PR) current controller is investigated using three case studies applying the previously described fault current contribution scenarios. The double-loop PR controller is found favorable when the inverter is designed to contribute its rated current to the fault. This conclusion is verified experimentally in this work.

An Improved Control Strategy of Triple Line-Voltage Cascaded Voltage Source Converter Based on Proportional–Resonant Controller

In this paper, the operation principle of a multiple converter, which is composed of the traditional two-level six-switch voltage source converter and constructed in line-voltage cascaded mode, is analyzed. The equivalent switching circuit model of the multiple converter is built based on its operation characteristic. By analyzing the feature of the multiple converter control, an improved voltage-current double-loop control strategy based on the proportional-resonant (PR) controller is proposed. The control strategy, which has the merit of the integrated control, can also realize the independent control of the transmission power of each unit of the multiple converter by adding the voltage-sharing compensation control. Meanwhile, a PR controller is adopted in the current loop. By giving a suitable current reference value for the controller, the problem of ac-side line-current asymmetry can be solved, and the effect of unbalanced grid voltages on the system can be avoided as well. The availability of the proposed control strategy is verified by the experimental results.

Power Feedward Strategy of Grid-Connected Inverter Based on Direct Power Decoupling

Take into account grid inverter that using direct power control is vulnerable to the disturbance of grid voltage, a control algorithm is proposed based on the relationship between the power and voltage, which is deduced according to the mathematic model of the inverter that using double-loop control strategy. The change amount of the output power of inverter is added to the reference of power closed-loop as power feedforward, which improves the dynamic response to the grid voltage change. Simulations with EMTDC/PSCAD are carried out and the comparison of output power response to grid voltage change between control with and without power feedforward verifies its effectiveness.

Design of the Vehicular Eletro-Optical Tracking Turntable Servo System and the Research on its Tracking Control Scheme

In order to realize the high precision tracking control of the vehicular eletro-optical tracking turntable with the car bodys vibration, it is necessary to design a high performance turntable servo system and a set of high precision eletro-optical tracking control scheme. In this paper, a digital servo system is designed, which has the control platform based on PC104 processor, has the torque motor as the actuator, has the gyro as the inertial velocity measurement tool and has the high precision encoder as the position measurement tool. Then, the gyrostabilized double speed loop control algorithm with disturbance observer compensating is designed to realize a good inertial velocity stability performace; and, a set of eletro-optical tracking compound position loop control scheme based on the target-missing quality data processing, the segmented PID control and the acceleration lag compensating control is proposed to enhance the eletro-optical tracking precision. The result shows that the tracking turntable based on the control technology designed in this paper is reliable, responses quickly, has a good speed stability performance and a high eletro-optical tracking precision performance.

Design of rail pressure tracking controller for novel fuel injection system

This paper proposes a rail pressure tracking controller based on a novel common rail system. A mathematical model, based on physical equations, is developed and used for feed forward control design. Rail pressure peak sampling mechanism is designed to remove the disturbance of rail pressure due to fuel injection. An enhanced tracking differentiator is designed to get smooth tracking signal and exact differential signal from signal with noise. Double loop control strategy is designed to decouple the system and to improve dynamic performance of the system. Experimental results indicate that fluctuation of rail pressure is within ±1MPa in steady condition, while within ±3 MPa in transient condition, which verifies the effectiveness of the proposed rail pressure control strategy.

Double-Loop Control of Inverter with LCL Filter in Electrical Power System Based on Improved Instantaneous Symmetrical Component

An improved instantaneous symmetrical component method is adopted to improve the performance of inverter with LCL filter under asymmetric voltage conditions in electrical power system. Positive and negative sequence components in voltage and current in electrical power system are calculated with fewer calculation time,which is suitable for pratical application.In addition,this paper analyses active and reactive power in the system.A double-loop control strategy is proposed to eliminate the influence of double frequency components in power and negative sequence current.The simulation results verify its feasibility and effectiveness.

Dynamic Simulation for Grid-Connected Inverters of Distributed Generation Based on DIgSILENT Software

This paper introduces some typical control methods for the grid-connected inverters in the distributed generation (DG) systems, the double-loop control strategy is focused on and analyzed in detail. The proposed outer-loop control strategies are summarized. Meanwhile, the inner-loop control method established on dq rotating frame is introduced. The simulation models of the inverters for DG in the DIgSILENT software are introduced, and the simulations for the proposed control strategies are realized.

A Simplified Power Conditioner Based on Half-Bridge Converter for High-Speed Railway System

With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively.

Force Loading Research on the Transfixion of High-Speed Train

To test the feasibility of proposed double-loop force loading control structure for the integrated testing system for high-speed train end relationship, it established the co-dynamics model of Stewart parallel manipulator and transfixion and developed the PID force controller. The sine force tracking simulation test was carried out in Simulink environment. The results show that, whether the input is in single dof or in 6 dofs, the output can meet the demand of amplitude attenuation and phase lag . This proved that this system has a good performance in force loading and the proposed control structure is feasible for the force loading test of transfixion.

Research of the Three-Phase PV Power Grid Inverter Based on PR Control Used in Biomedicine

In the process of Biomedicine PV Grid, in order not to affect the quality of the grid, must ensure that the output current of photovoltaic power generation system and grid voltage maintain a high degree of consistency in the frequency, phase and amplitude. In order to make the output current of PV Grid inverter to meet the relevant standard of the grid, the appropriate grid filter and control strategy is the key. In order to improve the quality of the grid current and reduce the pollution of the grid harmonic current on the grid, select the three-phase full-bridge inverter circuit with LCL filters. In the grid control strategy, select the double loop current control based on grid current and capacitance current, and introduce the PR control into the double loop control system, analyze that PR control can achieve zero steady state error tracking of grid sinusoidal reference current and anti-grid voltage disturbances. Make double loop current control and SVPWM control combined, and prove the stability of this method through the simulation experiment.

UGV Robust Path Following Control under Double Loop Structure with μ Synthesis

For the problem that the path following performance is degraded due to model uncertainty of the unmanned ground vehicle(UGV) during lateral maneuvering,a double loop control structure is designed,in which the path following control is the external loop and the yaw stability control is the inner loop respectively.A robust yaw stability control based on μ synthesis is proposed.Simulation results show that the UGV based on this method has better performance than PID(proportional-integral-derivative) and H∞ controller when model parameters are changed.In comparison experiments,the root mean square error of this method is 1/3 less than PID.The result shows that this method also has robust stability and robust performance with respect to uncertain vehicle parameters.