Double Closed-loop Control Method Research Articles

Harmonic Self-Compensation Control for Bidirectional Grid Tied Inverter Based on Crown Porcupine Optimization Algorithm

A self-compensating control strategy for harmonic parameters based on the crown porcupine optimization algorithm is proposed for the single-phase rectifier and two-phase inverter operation mode of the bidirectional converter. In order to improve the response speed of the inverter voltage, the instantaneous expressions of the phase angle coefficient and amplitude coefficient of the dc-side voltage doubling fluctuation are derived, and the third harmonic is calculated based on the crown porcupine optimization algorithm according to the Proportional Integral (PI) + Quasi-Proportional Resonance (QPR) double closed-loop control method and injected into the input voltage of the inverter side to offset the influence of the bus-doubling fluctuation on the output voltage of the two-phase inverters of B and C so that the total harmonic content of the two-phase output voltages of the two-phase inverters of B and C can be reduced. The total harmonic content of the B and C inverter output voltages is reduced. The effective control of the control method for single-phase rectifier two-phase inverter mode is verified through simulation. Finally, the effectiveness of the control strategy is verified by experimenting with a 15 kW LCL-type bi-directional converter prototype.

A Novel Double Closed Loop Control of Temperature and Rotational Speed for Integrated Multi-Parameter Hydro-Viscous Speed Control System (HSCS)

Hydro-viscous clutch has already become an inevitable choice for special vehicle transmission in the present and future. As a nonlinear system with a large hysteresis loop, its speed control performance is affected by input rotational speed, lubricating oil temperature, lubrication pressure, and other factors. The traditional control method cannot adjust the temperature and rotational speed, which will lead to problems of narrow speed range, poor rotational speed stability, and large dynamic load impact. In order to solve the above problems, this paper studies the control method of an integrated multi-parameter hydro-viscous speed control system (HSCS) in a controlled environment. Through the mechanism analysis of the law of HSCS, the influence law of speed and temperature during the system operation is found. The temperature closed loop based on model predictive control (MPC) is introduced to control the rotational speed, and then the traditional PID control results are compensated according to the speed closed loop. Next, a novel double closed loop control method of temperature and rotational speed for HSCS is formed. Finally, the simulating verification is carried out. Compared with the traditional control method, the design method in this paper can adjust the control parameters according to the temperature of the lubricating oil and the input rotational speed and effectively expand the domain of HSCS and the speed control stability. The effective transmission ratio is extended to 0.2~0.8, and the hydro-viscous torque and speed fluctuation under the engine rotational speed fluctuation are reduced by more than 30%. The novel control method of HSCS designed in this paper can effectively improve the influence of input rotational speed and lubricating oil temperature on the speed control performance of HSCS and can be widely used in nonlinear HSCS such as hydro-viscous clutch.

Research on harmonic suppression characteristics and control methods for low-frequency resonance suppressor

The problem of low-frequency harmonics and their resonance seriously threatens the safety of the fusion power supply system, and is one of the key issues that urgently need to be solved during high-power operation of fusion devices. The low-frequency resonance suppressor (LFRS) can compensate for the low frequency harmonic suppression effect of passive filter and active filter and the limitation of voltage and capacity, which is a new approach to solve the low frequency resonance problem of fusion power system. However, the performance of the LFRS is affected by the power grid parameters and the fundamental current circulation between the active filter and passive filter branches. The low frequency harmonic current and its resonance suppression characteristics are analyzed based on the multi-reference vector control strategy in this paper. On this foundation, a current double closed loop control method is proposed, which can ensure the safe and reliable operation of the LFRS system and the suppression effect of low frequency harmonic current. The correctness and effectiveness of the theoretical analysis are verified by RT-LAB Hardware-in-the-loop simulation.

Suppression Strategy of Starting Current Impulse in the Front Stage Rectifier of Electric Vehicle WPT System

The three-phase voltage type Pulse Width Modulation (PWM) rectifier is widely used in the front-end power factor of electric vehicle wireless charging systems due to its simple control structure and easy implementation. The system often adopts a double closed-loop PI control method based on voltage and current, which inevitably leads to a significant starting current surge and poses significant risks to the safe operation of the equipment. On the basis of establishing a mathematical model for PWM rectifiers, this article analyzes in detail the causes of starting over-current and designs a starting strategy with a voltage outer proportional and integral separated active current directly given. Simulation experiments show that this method can reduce the starting over-current of PWM rectifiers and the excessive DC voltage surge towards normal operation during the starting process.

Controller Design of a Novel Interleaved Parallel Bi-Directional DC-DC Converter

To improve the dynamic performance of the output voltage of the new interleaved shunt bi-directional DC-DC converter, a double closed-loop control method of voltage and current based on fuzzy PI control is proposed. Firstly, based on the study of the operating principle and steady-state performance of the new interleaved parallel DC-DC converter, a small-signal mathematical model of the interleaved parallel bidirectional DC-DC converter with different modes is established, and based on the model, the transfer functions from duty cycle to output voltage and inductor current are derived, and accordingly, the double-closed-loop controller of the bidirectional DC-DC converter is designed. Then the design method of the fuzzy PI controller is described in detail, and the fuzzy control is applied to the voltage outer loop of the double closed-loop control so that the system can adjust the PI parameters in real time. Simulation experiments are carried out by Matlab/Simulink to compare the simulation experimental waveforms using fuzzy PI control and conventional PI control, and it is verified that the fuzzy PI control improves the output voltage response speed of the new interleaved shunt bi-directional DC-DC converter, reduces the voltage peak of the system, and reduces the overshoot.

Model-Based Improved Advanced Adaptive Performance Recovery Control Method for a Commercial Turbofan Engine

In-service commercial aero-engine controls its thrust by controlling parameters such as speed/pressure ratio (Nf/EPR) characterized as measurable and indirectly related to the thrust. However, the mapping relationship between the Nf/EPR and the thrust would have unknown and nonlinear changes with the engine performance degrades, naturally causing it difficult to obtain the desired thrust by primarily designed Nf/EPR control and resulting in task degradation. Therefore, this paper proposes an improved double closed-loop self-adaptive performance recovery control method to yield the engine to maintain almost consistent performance in the whole life cycle. Firstly, the inner control loop of speed is designed based on the MPC algorithm to obtain the optimal fuel output through receding horizon optimization to improve the control performance. Secondly, the speed command from the inner control loop of the degraded engine is compensated by adding an outer control loop of thrust to maintain the desired thrust. In this control method, an improved high-precision parameter estimation method is present to estimate unmeasurable engine performance parameters. A steady-state identification algorithm therein is designed to judge the engine state to deal with the problem that the estimator might diverge due to the engine's strongly nonlinear performance changes under the circumstances of high dynamic operation. Finally, the simulation results show that, compared with the traditional method, the proposed method achieves the estimator's stable work, improves the control performance by 25.8%, and maintains the desired thrust in case of engine degradation.

A Driving Power Supply for Piezoelectric Transducers Based on an Improved LC Matching Network

In the ultrasonic welding system, the ultrasonic power supply drives the piezoelectric transducer to work in the resonant state to realize the conversion of electrical energy into mechanical energy. In order to obtain stable ultrasonic energy and ensure welding quality, this paper designs a driving power supply based on an improved LC matching network with two functions, frequency tracking and power regulation. First, in order to analyze the dynamic branch of the piezoelectric transducer, we propose an improved LC matching network, in which three voltage RMS values are used to analyze the dynamic branch and discriminate the series resonant frequency. Further, the driving power system is designed using the three RMS voltage values as feedback. A fuzzy control method is used for frequency tracking. The double closed-loop control method of the power outer loop and the current inner loop is used for power regulation. Through MATLAB software simulation and experimental testing, it is verified that the power supply can effectively track the series resonant frequency and control the power while being continuously adjustable. This study has promising applications in ultrasonic welding technology with complex loads.

Analysis and design of flexible arc suppression device based on proportional series lagging control

Flexible arc suppression technology can control zero-sequence voltage flexibly and realize arc suppression completely by injecting current to the neutral point of distribution network. However, in the existing control method, PI control cannot achieve zero steady-state error, and injecting current control needs to accurately measure the phase-to-ground parameters, so it is difficult to apply it in practice. For improvement, a new control method of the flexible arc suppression device is developed by using proportional controller and lagging network controller in this paper. The double closed-loop control method and the parameters of the controller are designed to improve the injecting current control performance. The zero-sequence voltage is set as the control target of the control system to realize arc suppression completely without measuring the phase-to-ground parameters. The effectiveness of the proposed control technology is verified by PSIM simulation and practical experiments. The simulation and experimental results show that the proportional series lagging control has better response speed and stability than the existing control method.

A single and double closed-loop compound anti-sway control method for double-pendulum bridge cranes locating at random position

In the assembly workshops of some heavy special equipment, the bridge cranes for payload lifting often needs to be located frequently. However, the locating position is often determined by the operator, which is random and results in significant payload oscillation and difficulties in trolley positioning. Furthermore, in practice, the bridge crane always exhibits more complicated double-pendulum dynamics compared with single-pendulum crane. To solve these problems, this paper establishes the double-pendulum model of bridge crane. Derived from the proportional-derivative (PD) control, the single closed-loop is designed based on the hook oscillation during acceleration and transporting; when locating, the double closed-loop is presented by utilizing the position and the hook oscillation. Combining the two control methods, a single and double closed-loop compound anti-sway control (SDCAC) method for the bridge crane is proposed. On this basis, to improve the performance of the SDCAC system, the sequential quadratic optimization (SQP) method is adopted to optimize PD parameters. Besides, a novel bumpless transfer control method is proposed to realize the smooth transition between the two control modes. Finally, the simulations and experiments are conducted. The results demonstrate the effectiveness of the proposed method.

Stability Improvement of Electric Ship Propulsion System Using Supercapacitor

Owing to the serious greenhouse gas emissions and inflexible control of traditional ship propulsion system, the electric ship propulsion system has been widely introduced into the ship’s power system. However, the variations of ship propellers will lead to the instability of electric propulsion system so this paper studied the transient characteristics of electric ship propulsion system by performing a series of experiments on a real electric ship propulsion system platform. Based on the experimental results, a detailed model of supercapacitor energy storage system (SCESS) is proposed to improve the voltage and frequency response for the electric ship propulsion system. To enhance the stability and reliability, a double closed-loop control method combined with Pulse-Width Modulation algorithm (PWM) is utilized to control the energy storage system for smoothing the power fluctuations caused by the electric propulsion system. The simulation results demonstrate the high efficiency of supercapacitor to improve the transient stability of the whole power system of the ship.

Modeling and simulation of three-phase 6/4 switched reluctance motor speed control system

To improve the response ability of the motor and reduce the torque ripple, we take the three-phase 6/4 SRM as the research object, according to the structure and characteristics of the SRM speed control system, the SRM speed and current double closed-loop control system are established and the current chopping control mode is adopted to change the motor speed. According to the mathematical model of SRM, then the model of each module of the speed control system is established by Matlab/Simulink. The simulation and performance analysis are carried out. The results show that the simulation model double closed loop control method can improve the system response ability, improve the stability of the motor and reduce the torque ripple.

Robust tracking control in the inertia phase for generalised disturbance

To solve the problem of shift shock during the inertia phase caused by generalized disturbances in wheel loaders and other construction instruments, a robust double closed-loop tracking control method based on an improved disturbance observer (DOB) has been proposed. In this method, the inner loop robustly suppresses disturbance and the outer loop realizes trajectory tracking. The improved DOB based on a nominal disturbance value (NDV) can enhance the disturbance suppression ability of the inner loop when a large part of the generalized disturbance is determinable. The model matching method transforms the outer loop into a transfer function to meet the expected performance. A disturbance compensation controller eliminates the nominal disturbance in the system. A feedforward compensation controller eliminates the influence of reference inputs in the system. Considering the inertia phase of a fixed-axis automatic transmission of a wheel loader, the proposed method was applied to the driveline simulation platform of a specific type of wheel loader. Random loads under actual working conditions were considered as the input load of the simulation platform. The simulation results indicated that the DOB based on the NDV method has better disturbance suppression capability, more accurate tracking capability and smaller shift shock than the conventional DOB method. The proposed control method exhibits robustness under 10%, 50% and 90% of the maximum load. The highest shift shock is 4.94% of the manual shift shock and it is effectively reduced. Thus, robust and smooth inertia phase shift control of the automatic transmission can be realized. This study presents an effective method for solving robust disturbance suppression control problems and tracking control problem under large generalized disturbances.

Design and application of double closed loop weight control system for cigarette maker

In order to solve the problem that the precision of cigarette weight control system is not high enough in cigarette machine production, a double closed loop weight control system of cigarette machine is designed according to the characteristics of cigarette machine control system. This system takes IPC as the control core. Firstly, the current cigarette weight is obtained, then the weight deviation is calculated, and then the distance to be moved by the actuator is calculated based on the deviation. Then the current position of the actuator is obtained, and the target position of the actuator is calculated. The results show that the long-term deviation of the weight control system using the double closed-loop control method can be reduced to less than 4.0mg during the production of the target weight of 490mg cigarette, which is 0.8mg lower than that of the single closed-loop control method. This technology can improve the quality of cigarette process and reduce the overall consumption.

Research on D-STATCOM Double Closed-Loop Control Method Based on Improved First-Order Linear Active Disturbance Rejection Technology

The application of a distribution static synchronous compensator (D-STATCOM) is the best technical means to solve the problem of reactive power compensation and harmonics. The D-STATCOM system has the characteristics of variable parameters, strong coupling, nonlinearity and multi-variability. In order to improve the speed of the dynamic tracking response and anti-disturbance capability of the D-STATCOM, the article proposes an improved Linear Active Disturbance Rejection Controller (LADRC) based on the total disturbance deviation control method. Combined with double closed-loop control, the inner loop takes the current as the state variable, and the outer loop uses the DC side output voltage as the state variable to achieve robust stability of the D-STATCOM and controller output. The simulation results show that the improved LADRC is more stable than the traditional LADRC in controlling the DC voltage waveform of the compensator, reactive current tracking and reactive power compensation waveform when it is disturbed, which verifies the superiority and feasibility of the improved LADRC.

The voltage response test of ITER PF converter bridge

As the key component of international thermonuclear experimental reactor (ITER) poloidal field (PF) converter units, converter bridges are supplied by converter transformer with two primary and two secondary three-phase windings, and output the on-load voltage (±1.05 kV) and the rated DC current (±27.5 kA). Moreover, the converter bridge should provide the symmetrical voltage response not more than 2 electrical cycles (40 ms) for full scale change (-1.05 kV to 1.05 kV) when the AC power is in the rage of 62 kV–72 kV. The voltage response test is essential to verify the voltage response performance of PF converter bridge meet ITER requirements or not. The double closed-loop control mode of inner current loop and outer voltage loop is usually adopted in the dynamic response test of low-power converter in other fields. ITER PF converter is a special high-power converter used in nuclear fusion field. According to its operation characteristics, the voltage step response of the converter only needs to be detected in the case of open-loop voltage, and the output current of the converter must reach the rated value in the process of voltage response. Therefore, the double closed-loop control method is not suitable for the voltage response test of ITER PF converter, and a new and reasonable test scheme need to be designed. This paper mainly presents the analysis and design of the voltage response test scheme, and the feasibility of test scheme is confirmed by the simulation results and test results, which will provide the method and reference for the voltage response test of high-power converter in nuclear fusion field.

A Novel Double Closed-loop Control Method for Single-phase PWM Rectifier

Abstract The research object is the single-phase PWM rectifier in this paper. The goal of DC voltage dynamic response speed improvement and unit power factor realization is the rectifier oriented. Based on current inner loop DQ decoupling control and voltage outer loop adaptive fuzzy PI control, a double closed-loop control method for single-phase PWM rectifier is proposed. Firstly, based on the second-order generalized integrator algorithm, the DQ current decoupling control mathematical model is established by analyzing the rectifier decoupling control. Secondly, fuzzy PI control algorithm is designed for voltage outer loop control. Finally, simulation verification is carried out. Simulation results prove that the proposed control strategy has good dynamic performance.

Geometric Analysis Based Double Closed-Loop Iterative Learning Control of Output PDF Shaping of Fiber Length Distribution in Refining Process

In order to improve the pulp quality and to reduce the energy consumption, the fiber length distribution (FLD) is generally employed as one of the important technological indexes in the refining process. Considering that the traditional mean and variance of fiber length are unable to adequately characterize the non-Gaussian distribution properties, this paper proposes a novel geometric analysis based double closed-loop iterative learning control (ILC) method for probability density function (PDF) shaping of output FLD in the refining process. Primarily, a radial basis function (RBF) neural network with Gaussian-type is utilized to approximate the square root PDF in the inner loop, where the RBF basis function parameters (center and width) are tuned between any two adjacent batches by using an ILC law, and the subspace identification method can be applied to establish the state-space model of weight vector. Then, for the sake of accelerating the convergence rate of the closed-loop system, a geometric analysis based ILC method is adopted in the outer loop. Finally, both simulation and experiments demonstrate the effectiveness and practicability of the proposed approach.

Research and Design of Rod Control Cabinet in Nuclear Power Plants Based on Digital Control

There are disadvantages such as poor applicability, slow dynamic response of load output and poor anti-interference ability of the rod control power supply cabinet in operation. This paper redesigns a new type of power cabinet based on programmable logic controller (PLC) and digital signal processing (DSP) technology which adopts fast energy absorption loop and double closed-loop control method in the main circuit. Then the coordination test in the cold and hot states between the designed cabinet and ACP1000 control rod drive mechanism(CRDM) is carried out. The test result proves that the function of the cabinet satisfies the application requirements of generation-III nuclear plants and effectively solves the disadvantages of the existing cabinet.

High-bandwidth fine tracking system for optical communication with double closed-loop control method

A fine tracking system is crucial for maintaining the accuracy of the optical communication terminals that aim at each other. To ensure the reliability of the communication link, the fine tracking system requires high bandwidth to mitigate the effect of arrival angle fluctuation caused by atmospheric turbulence. Traditionally, the fine tracking system includes only a single feedback loop; a high bandwidth is obtained by increasing the high gain of the fine tracking system, which usually suffers considerably from the time delay engendered by sampling and data processing, the hysteresis nonlinearity of a fast steering mirror (FSM), and the limitations of dynamic response of FSM. To track the beacon in real time and with high precision, a pioneering control method is presented in our paper, namely, double closed-loop control (DCC), which performs better in a tracking system compared with a traditional single-feedback loop. In the inner feedback loop, the response of FSM is measured by a strain gauge sensor (SGS) and used as the inner feedback signal. Thus, by co-operating with the outer CCD-based feedback loop, a DCC scheme is proposed for the fine tracking system. With the SGS signal, the inner loop controller is designed to obtain a rapid response without overshooting; meanwhile, the hysteresis nonlinearity is diminished. Experimental results indicate that the static hysteresis nonlinearity of FSM is reduced from 15.6% to 1.4% by an inner feedback loop, and the dynamic response and stability of FSM is greatly improved, thereby simplifying the outer loop controller design. Then, with the SGS signal, the time delay of the outer loop can be compensated accurately with a predicted signal compensation method. The experimental results show that the −3 dB error rejection bandwidth is increased from 76 to 85 Hz, and the coupling efficiency in our optical communication system is improved by 16.87% after using the DCC fine tracking method. These results indicate that the DCC method can effectively achieve the goal of fast and accurate tracking for optical communications systems.

Trajectory Tracking Control of AGV Based on Sliding Mode Control With the Improved Reaching Law

In order to quicken the response of the sliding mode control system, a novel reaching law with the dynamic coefficients, which could strengthen the role of the major term and weaken the role of the minor term, respectively, in the different stages, is proposed. The finite-time convergence of the improved reaching law is proved. The kinematical and the dynamic models of the automated guided vehicle are established, and a double closed-loop control is designed to perform the trajectory tracking. The sliding mode control method based on the improved reaching law is used to control the attitude of the automated guided vehicle, and the outer loop controller outputs the desired attitude. The simulation results show that the improved reaching law could make the system arrive at the sliding surface more rapidly than the conventional reaching laws, the automated guided vehicle could have faster attitude response speed, and the different given trajectories could be tracked effectively by the double closed-loop control method.