Traditional PI Control Method Research Articles

Design of sensorless permanent magnet synchronous motor controller based on improved sliding mode observer

Because PMSM needs to install a position sensor in practical application, and the buffeting issue in sensorless control stems from an old SMO (sliding mode observer), an improved SMO is proposed. Stemming from the improvement of the switching function and low-pass filter of the traditional SMO, the chattering problem of the conventional SMO is optimized. Considering the reality that the traditional PI control strategy unable to respond accurately and quickly in the case of current coupling, the current complete decoupling integrates the traditional PI control method is adopted. It can speed up system response and improve system performance. The experimental consequence demonstrates that the improved SMO can effectively restrain the chattering phenomenon and realize the fast and precise control of the PMSM.

Grid-Connected PV Inverter Control Strategy Based on the Sliding Mode

The Photovoltaic grid-connected inverter is an essential equipment of photovoltaic grid-connected system. Due to the disadvantages of the traditional PI control method for grid-connected photovoltaic inverters, this paper adopts the integral sliding mode variable structure to control grid-connected inverters. Grid inverter DC control mode was introduced in detail in the sliding mode variable structure control strategy. Using Matlab simulation platform to compare and analyze the traditional PI voltage compensation control strategy and sliding mode variable structure control strategy. From the waveform of the simulation output, the current harmonic at the output of the grid-connected inverter is reduced, and the power factor is increased, with the power factor is close to 1. The control precision, robustness and anti-interference ability of grid-connected system are improved. Which proved the feasibility and the superiority of the proposed control strategy.

Sliding Mode Control of Ship DC Microgrid Based on an Improved Reaching Law

The bus voltage of the ship DC microgrid is sensitive to the change of loads, which has an influence on the power supply quality. This paper introduces a hybrid energy storage system (HESS) that is composed of a battery set and a supercapacitor set, and further studied the control method of HESS. First of all, the topological structures of the ship DC microgrid and HESS are described. Second, combined with the frequency division droop control and voltage PI control, a sliding mode control (SMC) method is proposed to control the charge and discharge of HESS based on an improved reaching law. Finally, the simulation model of the ship DC microgrid is established for the verification of the control method. Simulation results show that: (1) HESS can overcome the shortage of the dynamic response ability of the diesel rectifier generator to the steep change of load power. The supercapacitor set and the battery set successfully respond to the high-frequency and low-frequency components of the differential power in the system, respectively. (2) Compared with the traditional PI control method, SMC can reduce the current chattering of HESS and the voltage fluctuation amplitude of the DC bus. The proposed SMC method can provide a reference for the stable and reliable operation of the ship DC microgrid.

Speed Control of a Multi-Motor System Based on Fuzzy Neural Model Reference Method

The direct-current (DC) motor has been widely utilized in many industrial applications, such as a multi-motor system, due to its excellent speed control features regardless of its greater maintenance costs. A synchronous regulator is utilized to verify the response of the speed control. The motor speed can be improved utilizing artificial intelligence techniques, for example fuzzy neural networks (FNNs). These networks can be learned and predicted, and they are useful when dealing with nonlinear systems or when severe turbulence occurs. This work aims to design an FNN based on a model reference controller for separately excited DC motor drive systems, which will be applied in a multi-machine system with two DC motors. The MATLAB/Simulink software package has been used to implement the FNMR and investigate the performance of the multi-DC motor. moreover, the online training based on the backpropagation algorithm has been utilized. The obtained results were good for improving the speed response, synchronizing the motors, and applying load during the work of the motors compared to the traditional PI control method. Finally, the multi-motor system that was controlled by the proposed method has been improved where its speed was not affected by the disturbance.

Model predictive control for the performance improvement of air source heat pump heating system via variable water temperature difference

The heat pump heating system has been widely accepted to provide space and water heating in commercial and residential buildings. However, the operating energy performance in practice conditions is limited due to the traditional control strategy. An efficient-cost advanced control strategy is desired to improve the overall operating performance. This paper presents a model predictive control (MPC) strategy for an air source heat pump (ASHP) heating system to optimize the overall operating performance. Based on the control-oriented model and objective function, MPC can provide the optimized compressor frequency and water mass flow rate in real-time, which can lead to the optimized real-time variable water temperature difference. Thus, the total power consumption can be minimized for the heating system by coordinating the compressor power consumption and water pump power consumption in the real-time operating condition. A high-fidelity physical model is first built to produce the required data source, and then the control-oriented model is derived based on the machine learning technique. MPC is designed to minimize the total power consumption providing that the heating capacity is well maintained. The MPC strategy is evaluated and compared with the traditional PI control method under three operating cases.

Self-optimizing Pitch Control for Large Scale Wind Turbine Based on ADRC

Since wind turbine is a complex nonlinear and strong coupling system, traditional PI control method can hardly achieve good control performance. A self-optimizing pitch control method based on the active-disturbance-rejection control theory is proposed in this paper. A linear model of the wind turbine is derived by linearizing the aerodynamic torque equation and the dynamic response of wind turbine is transformed into a first-order linear system. An expert system is designed to optimize the amplification coefficient according to the pitch rate and the speed deviation. The purpose of the proposed control method is to regulate the amplification coefficient automatically and keep the variations of pitch rate and rotor speed in proper ranges. Simulation results show that the proposed pitch control method has the ability to modify the amplification coefficient effectively, when it is not suitable, and keep the variations of pitch rate and rotor speed in proper ranges

An Improved Repetitive Control for Circulating Current Restraining in MMC-MTDC

The modular multilevel converter (MMC) is widely used in many important application fields such as high voltage DC transmission system. And the multi-terminal architecture of it attracts many attentions. However, the circulating current of MMC is an inherent problem which is mainly caused by the voltage mismatch between arms and DC bus. In this paper, an advanced repetitive control method is proposed. This method is based on the even-harmonic characteristic of the circulating current and the potential feature of repetitive control that it has an internal integration part. The pole diagram of the closed loop transform function of the proposed control system proves the stability of the proposed method. And according to the simulation results of a three-terminal MMC-MTDC model in PSCAD/EMTDC, the improved repetitive control presents better circulation repression ability and superior anti-interference capability by comparing with traditional PI control method. Additionally, the simulation results also indicate that the proposed repetitive controller can restrain the fluctuation of SM voltage more effectively than PI control.

SMC-DPC based active and reactive power control of grid-tied three phase inverter for PV systems

In this paper, sliding mode control (SMC) – direct power controller (DPC) based active and reactive power controller for three-phase grid-tied photovoltaic (PV) system is proposed. The proposed system consists of two main controllers: the DC/DC boost converter to track the possible maximum power from the PV panels and the grid-tied three-phase inverter. The Perturb and Observe (P&O) algorithm is used to transfer the maximum power from the PV panels. Control of the active and reactive powers is performed using the SMC-DPC strategy without any rotating coordinate transformations or phase angle tracking of the grid voltage. In addition, extra current control cycles are not used to simplify the system design and to increase transient performance. The fixed switching frequency is obtained by using space vector modulation (SVM). The proposed system provides very good results both in transient and steady states with the simple algorithms of P&O and SMC-DPC methods. Moreover, the results are evaluated by comparing the SMC-DPC method developed for MPPT and the traditional PI control method. The proposed controller method is achieved with TMS320F28335 DSP processor and the system is experimentally tested for 12 kW PV generation systems.

Study on the New Compound Control Method of Three-phase Voltage Source PWM Rectifier

Since the three-phase voltage source PWM commutator is hard to obtain favorable accommodation effect under larger disturbance and variational controlled objects when traditional PI control method is used. This paper comes up with a new type double closed-loop compound control method on the basis of traditional double closed loop control method, that is to say the combination of PI control and fuzzy control is applied to outer voltage control, and the load current is served as forward-feed compensation, inner current ring uses the PRcontrol method. By means of MATLAB/Simulink emulation, the results show that the system not only has a favorable steady-state performance, but also strong robustness to external disturbance, which could verify the feasibility of this control scheme.

Research on Speed Control of Brushless DC Motor Based On Predictive PI Control

The traditional PI control method is used to control the brushless DC motor with the disadvantage that the proportional and integral parameters are constant. So an advanced method of predictive PI control is proposed, which predicts the value of speed of next moment by multi-order incremental method based on the current and previous speed of brushless DC motor. And the simulation model is established by MATLAB. Then the results that the method is better than traditional PI control and fuzzy control in the speed modulation, specific performances: faster response, less overshoot, stable anti-disturbance and better stability.

Bandwidth Expansion Method for Circulating Current Control in Parallel Three-phase PWM Converter Connection System

The use of common dc-link parallel three-phase PWM converters without isolating transformers will cause zero-sequence circulating current problem. Previous works have proven that the circulating current is mainly affected by zero vectors employed in each PWM cycle. This paper proposes a novel method to suppress the circulating current. Detailed analysis is presented on the causes of zero-sequence circulating current based on a derived average model. A zero vectors feed-forward control strategy in combination with traditional PI control method is proposed to reject disturbances in zero-axis current system. In addition, a dual current sampling and dual PWM duty ratio update (DSDU) scheme is used to expand the bandwidth of zero-axis current loop. As a result, better circulating current suppression performance can be achieved in different filter inductance and converter output currents condition. Compared with the PI control method, the converters operated in parallel can be switched on and switched off separately with small current impact. Experimental results confirm the performance and effectiveness of the proposed method.

Researching of Speed Regulation System for AC Permanent Magnet Synchronous Motor

In order to improve the speed performance of permanent magnet synchronous motor(PMSM) speed control system, and increase system reliability and adaptability, PMSM current-speed double close loop speed control system based vector control was designed. Current loop adopted traditional PI controller, speed controller adopted adaptive fuzzy PI control method which was based on traditional PI control method and fuzzy control method. Space voltage pulse width modulation (SVPWM) technology was used to control working condition of the inverter. The system simulation model was established in MATLAB/SIMULINK environment, and ran this simulation model.The simulation results show that: This system is feasible, and adaptive fuzzy PI control system has better dynamic and static characteristics than traditional PI control method.