A simplified digital control method for active power filters

This paper deals with the design and implementation of cascaded H-bridge multilevel voltage source converter-based static synchronous compensator (STATCOM) for simultaneous active and reactive power compensation, voltage stability and damping of power oscillations. The main objective is to provide active power support and maintain the voltage stability by compensating the reactive power in the power system. In this paper, the multi pulse inverter-based STATCOM has been replaced by multilevel inverter-based STATCOM to overcome the drawbacks of the former. Cascaded H-bridge (CHB) MLI for implementation of STATCOM has been used as CHB MLI is considered the best for STATCOM applications due to its modular structure and requirement of lesser number of components. MLI-based STATCOM is used to provide simultaneous reactive power and active power compensation established by using super-capacitor. The super-capacitors are connected with each DC link capacitor of CHB MLI by using the DC-DC buck boost converter. The STATCOM is also used to provide voltage stability during the power quality problems such as voltage sag and voltage swell, it is established by injecting or absorbing reactive power. The STATCOM is also used for damping the power oscillations by controlled injection of reactive power hence enhancing transient stability. Nine-level cascaded H-bridge MLI-based STATCOM is designed for simultaneous reactive power and active power compensation, voltage stability and damping the power oscillations. Exhaustive simulations have been carried out using MATLAB/Simulink and SimPowerSystems software. The simulation results are presented to prove the effectiveness of MLI-based STATCOM for simultaneous active and reactive power compensation, voltage stability and damping of power oscillation.

This paper presents a simple control method for improvement of dynamic responses in a digitally controlled low-harmonic rectifier with power factor correction (PFC). The controller uses a fixed or self-adjusting dead zone in analog-to-digital conversion to eliminate the output capacitor ripple from the voltage control loop. The proposed control methods are tested in a completely digitally controlled 200 W boost PFC operating at 200 kHz switching frequency. Experimental results show that the simple controller implementation results in low current harmonics and significantly improved output voltage transient responses.

<span lang="EN-US">This article focuses on the control of STATCOM for the improvement of reactive power compensation during grid faults and unbalanced load. The problem encountered with convectional voltage source converter based STATCOM for reactive power management and capacitor voltage balancing during grid faults are analyzed and its operational limitations are studied. To remove the above problems, an adaptive low voltage ride through control technique based modular double star cascaded converter (DSCC) STATCOM is proposed. In this dynamic control, the positive reactive currents and negative reactive currents are separately controlled for reactive power management and a zero (Vo) sequence voltage is inserted for the management of active power. This advanced control method effectively balances the submodule capacitor voltage within its prescribed limits by managing the equal distribution of active power between converter legs and provides dynamic reactive power management during grid faults. The effectiveness of the DSCC-STATCOM, with proposed control method is verified using MATLAB/Simulink software-based simulations under single line to ground fault and unbalanced load.</span>

This paper proposes a simplified vector control method with output capacitor voltage balance for voltage oriented control of the three-level three-switch Vienna rectifier. The proposed control method makes use of a single carrier based pulse width modulated (PWM) switching technique instead of complex space vector method for the Vienna rectifier. The vector control method is comprehensively compared with the existing hysteresis control method in terms of transient response and input current total harmonic distortion (THD). This method is implemented to control the converter for wide range of load and unbalanced grid supply voltage conditions. A 1 kW prototype of the converter is built and tested in the laboratory environment using the proposed vector control method and compared with the conventional hysteresis control method. The proposed control method provides unity power factor operation with sinusoidal input currents at the input side and balanced output capacitor voltages at the output side.

Developed in this work, is a simple and innovative control method, by which a nonminimum-phase (NMP) process can be easily stabilized in a closed-loop setting. The method is named as the parallel feed-forward compensation with derivative effort (PFCD). Through use of a high order process, the control system designed by the PFCD method is shown to be less influenced by noise, disturbance, and model mismatch, compared to other methods. Moreover, the necessary data required for implementing the PFCD method are discussed. The proposed control method is illustrated on tip position control in a slewing beam as a flexible robot arm, in which the effectiveness of the PFCD method is demonstrated. In addition, the proposed control method is compared with the existing methods in terms of stability and performance. The paper is concluded with notes about the advantages.

Hopf bifurcation frequently results in periodical oscillation instability in the nonlinear system. For Hopf bifurcation at equilibrium point in the wind power system, Hopf bifurcation point of the wind power system with static var compensator is calculated based on the continuation method. The analysis shows that the increase of reactive power will lead to Hopf bifurcation, static var compensation can delay Hopf bifurcation and improve voltage stability region via reactive power compensation, in order to eliminate Hopf bifurcation, a unified and simple linear feedback control method is adopted. The results indicate that the method put forward in the research is effective to eliminate Hopf bifurcation in the wind power system

This paper proposes a novel and simple control method for an active power quality compensator (APQC) used in electrified railways. The proposed method consists of only constant do capacitor voltage control, which is generally used in APQCs. No detection method for harmonic, reactive and negative-sequence components is necessary. Thus we offer the simplest way to compensate the harmonic, reactive and negative-sequence currents on the primary side of the Scott transformer in the traction substation. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with unity power factor are obtained on the primary side with the proposed control method, which uses only constant do capacitor voltage control.

In this paper, a novel but simple control method using command feedforward and feedback PID control, or called two degrees-of-freedom (Two-DOF) control, is presented for temperature control of a stretch polyethylene terephthalate (PET) blow molding machine. To achieve required temperature control of PET bottle performs passing through both heating ovens, our proposed controller consists of a digital command-feedforward controller designed to improve the transient performance and track quickly temperature set-points, and a digital feedback proportional-integral-derivative (PID) controller proposed to eliminate temperature errors and accomplish disturbances rejection. Such a controller not only carries out precise temperature setpoint tracking under any arbitrary ambient environment, but also uses the practical expertise of the control practitioners working for PET blow molding machines. Excellent set-point tracking and disturbance rejection of the proposed control method are well illustrated by computer simulations and experimental results. The results also clearly show applicability and superiority of the proposed method in comparison with other existing controllers.

In this study, design and implementation of a shunt active power filter (APF) based on a simplified control method is given without load and filter current measurement. The proposed simplified control method is based on instantaneous reactive power theory (IRP) and requires only measuring the source currents to reduce the number of current sensors (CSs) required in the conventional control approach. The source currents are exactly in phase with the line voltages and approximately in sinusoidal waveform after reactive power and harmonic compensation. The proposed control technique has been tested under different load conditions using Matlab/Simulink simulations and validated with a 10 kVA/380 V experimental prototype based on digital signal processor (DSP) TMS320F2812. Both simulation and experimental test results demonstrate that the proposed method is feasible in meeting the IEEE 519-1992 recommended harmonic standard limits.

One of the simplest and most popular methods to design a model-based controller for a nonlinear dynamic system is to apply linear control theories to the linearized model of the nonlinear system. For linearization, first-order Taylor series expansion is a straightforward and widely used method. Although the related linearization method is fairly simple, unfortunately, it causes an error in the linearized model, especially in highly nonlinear systems. Different strategies have been proposed to increase the robustness of linearization-based control methods against the linearization error. All of the methods somehow look at the linearization error as uncertainty or disturbance, which has to be rejected. Generally speaking, the lack of the linearization technique reduces the quality of control. One area in which quality and simplicity of control can be necessary is spacecraft attitude control. For the purpose of spacecraft attitude control, this paper improves a well-known trajectory linearization control (TLC) method as a simple and practical nonlinear trajectory tracking control method using an error-less, fine linearization technique. The modified TLC is then used to develop a control law for spacecraft attitude control with only three tunable control parameters and an approximation of the spacecraft inertia matrix. Finally, due to the elimination of uncertainty caused by the linearization error, in a simple way, the novel attitude controller leads to better performance in comparison with the traditional method. The superiority of the new approach is illustrated in numerical simulations.

Taking the air conditioner cluster as the object, under the condition of individual perception and controllable state of the air conditioner, the cluster state is given a considerable and controllable function. In the analysis of the load model of a single air conditioner, considering the comfort of indoor temperature, the characteristics of on and off are given, that is, the cycle of on time and off time; on this basis, the air conditioning clusters are divided according to the same or similar switching cycles, thereby forming a switching strategy of series and parallel groups to achieve load balance. In the on state, if the adjustment of the power of the air conditioner itself is not considered, a simple aggregation control method is given. The analysis of numerical examples shows that this method is simple and reliable.

Nonsingular Fixed-time Sliding Mode Control (NFSMC) method is one of the nonlinear control methods which is robust against uncertainties and external disturbances. This paper presents an NFSMC method to synchronize two similar Willamowski–Rossler reaction chaotic systems. The proposed control method is robust against uncertainties and external disturbances; also, it is an accurate and fast control method. The proposed control method is compared with a Nonsingular Terminal Sliding Mode Control. The comparison results show that the proposed control method provides a better control solution for this system.

Aiming at the existing problems of conventional substation voltage and reactive power integrated control method, a new fuzzy logic based dynamic reactive power boundary voltage and reactive power integrated control method is proposed. Fuzzy logic control rules, membership function, dynamic reactive power boundary and system structure are introduced. In accordance with this fuzzy logic control strategies, decoupling control of voltage and reactive power in tight coupled zone can be obtained. Simulation results indicate that this approach shows better effect compared with the conventional nine-area control method, the adjust times of transformer tap and capacitors can be reduced effectively to increase the service life time of the transformer tap changer and capacitor switch. This fuzzy logic control method can improve the performance index of the substation voltage and reactive power integrated control device and also preferably adapted to the load characteristics through the dynamic reactive power boundary.

This work investigates the performance of a single-phase grid-connected photovoltaic (PV) system under non-ideal source voltage conditions using a fuzzy logic controller. The single-phase instantaneous reactive power theory has been modified to explore the harmonic and reactive power compensation with distorted grid voltage excitation while transferring active and reactive power to the grid and the non-linear load. Instead of a traditional Proportional-Integral (PI) controller, the proposed method implements a fuzzy logic controller for the extraction of the reference compensating current. This method is compared with the traditional single-phase instantaneous reactive power theory. The advantage associated with a fuzzy logic controller is that it does not need accurate mathematical modeling of the system, instead, it is based upon the linguistic characterization of the input and output variables. Besides, care has been taken to provide uninterrupted compensation throughout the variation of the solar irradiation level. The proposed method has also been verified through a laboratory-developed prototype using a DS1103 processor.

This study presents two improved designs of eccentric-shaped permanent magnets and teeth-shaped stators in radial-flux dual three-phase permanent magnet electric machines to reduce cogging torque and torque ripple. The finite element analysis (ANSYS Electromagnetics) has been adopted in simulation, and real radial-flux dual three-phase permanent magnet electric machines have been fabricated in experiment to verify the study. Using the radial-flux dual three-phase permanent magnet electric machines in electric machine systems can improve the reliability and obtain higher output torque. In electrical drives and control, a simplified model-free predictive current control method has been proposed and implemented to drive the radial-flux dual three-phase permanent magnet electric machines, and the control law has been achieved by a TMS320F28377S microcontroller of Texas Instruments. The simplified model-free predictive current control method is senseless to parameter variations and back electromotive force of the permanent magnet electric machines, and only needs current sensors to detect six-phase current. The optimal one has been chosen by 14 various switching modes, which has the minimum cost function, and then the converter can be directly driven and controlled in the next sampling period. The features of the simplified model-free predictive current control method can reduce the algorithm calculation and avoid the defect of conventional model-based predictive current control scheme. A proportional-integral speed controller has also been designed to achieve the speed response of the fixed-speed tracking effect. Finally, the feasibility and effectiveness of the proposed simplified model-free predictive current control method for the dual three-phase permanent magnet electric machines can be verified in the experimental and quantitative results.