Three-phase Active Power Filter Research Articles

A Paralleled Current and Voltage Control Strategy With Compound PI Controllers for Three-Phase Active Power Filters

A Paralleled Current and Voltage Control Strategy With Compound PI Controllers for Three-Phase Active Power Filters

Adaptive PI + VPI Harmonic Current Compensation Strategy under Weak Grid Conditions

With the increase of the penetration rate of renewable energy power generation in the power system, the power grid gradually tends to be weak. Under the scenario of nonlinear load connecting to weak power grid, the grid-side voltage will produce unbalance, distortion and frequency deviation due to the influence of large internal impedance, insufficient inertia, three-phase current unbalance and harmonics of weak power grid. The operation of active power filters (APF) under above conditions can lead to significant degradation in harmonic compensation performance. An adaptive proportional integral (PI) + vector PI (VPI) harmonic compensation strategy for a three-phase APF is proposed for use in complex conditions of weak grid. The strategy consists of an adaptive notch filter based synchronous phase-locked loop (ANF-PLL) and an adaptive PI + VPI current control method. In this strategy, a series of adaptive lattice notch filters are introduced to improve the accuracy of grid phase and frequency estimation under the condition of voltage unbalance, distortion and a large range of frequency deviation. Then the phase and frequency information are used in the Park transformation of harmonic detection and current compensation control and the update of PI + VPI current control law parameters. A VPI current tracking controller with adaptive resonant frequency is constructed, which can improve the gain of the resonant frequency point and ensure that the APF can maintain the best compensation performance under the above weak grid conditions. Finally, the simulation and experimental results indicate that the ANF-PLL shows a better phase and frequency estimation performance under complex conditions of weak grid than the conventional and notch filter based methods, and the harmonic compensation strategy presented in this paper achieves a significant performance improvement under complex conditions of weak grid compared with Fixed VPI/SRF-PLL strategy and adaptive VPI/NF-PLL strategy.

A novel Algorithm Adaptive Autarchoglossans Lizard Foraging (AALF) in a shunt active power filter connected to MPPT-based photovoltaic array

Power quality issues often involve harmonics. Harmonics may harm capacitors, overheat equipment, cause motor instability, and increase neutral currents. A shunt filter is used as a harmonic compensation device. The world is moving towards more alternative energy due to its reduced cost. Nevertheless, because conventional energy has downsides of more pollution and higher cost, renewable energy is free of these problems and has higher demands nowadays. There are various conventional control techniques like constant instantaneous power control, Sinusoidal current control, synchronous reference frame and many more. But they lack in areas like less harmonic reduction, accuracy, speed and many more. This paper's main aim is to optimize the common constant instantaneous power control technique using a new adaptive autarchoglossans lizard foraging algorithm (AALF) to control a three-phase active power filter with a solar photovoltaic array installed at its DC-bus. The conventional and optimized control technique will be compared based on the source current THD and voltage THD under balanced supply conditions. The comparison method will be simulation done using MATLAB. In this paper, two key performance aspects will be discussed. They are THD and compensation time.

Harmonic Compensation of APF Three-phase Three-line System Based on Quasi-PR Control

The Active power filter (APF) plays an important role in reducing the harmonic distortion rate of grid current and improving grid stability. However, the APF based on traditional methods such as deadbeat control and hysteresis control has poor tracking accuracy for the load harmonic current, and it is difficult to achieve efficient compensation. In this regard, this paper proposes a current inner loop quasi-proportional resonant (PR) control method to achieve fast-tracking of the compensation current and high control precision. Then, according to the equivalent mathematical model of the three-phase APF in the continuous domain, the parameters of the quasi-PR control method are designed. Finally, the effectiveness of the proposed method is verified by simulation.

Nonlinear control of grid-connected PV systems using active power filter with three-phase three-level NPC inverter

Grid-connected photovoltaic (PV) systems have become a significant area of interest for research scientists. Given this, this article presents a nonlinear control of grid-connected PV systems using active power filter (APF) with three-phase three-level neutral point clamped (NPC) inverter. The control objectives involve: (1) Forcing the PV output voltage to track a reference signal provided by the MPPT block in order to produce their maximum power, (2) Regulating the DC link voltage to satisfy a correct operation mode of the three-phase active power filter, and (3) Satisfying power factor correction (PFC) objective at the point of common coupling, PCC. Therefore, the suggested control strategy includes a cascade structure of two loops. The inner-loop regulator is designed using the sliding mode control technique and Lyapunov approaches to ensure the PFC objective by forcing the grid current to follow a given reference signal. The Outer-loop consists mainly of a proportional-integral (PI) regulator so that to regulate the output voltage. Further, the theory of instantaneous real power is used to calculate reference harmonics. The effectiveness of the proposed controller is demonstrated through simulation results using MATLAB/Simulink.

Digital controller for active power filter based on P-Q theory under non-ideal main voltages

<span>This paper proposes a control strategy active power filter under non-ideal main voltages. The P-Q Theory is used to generate three-phase active power filter reference currents, but the P-Q Theory has a weakness when implemented under non ideal main voltages. This paper proposes a reference current generation method using modified P-Q Theory under non-ideal main voltages conditions. Before calculating the P-Q Theory, the non-ideal voltage at the source is normalized by using PLL to determine the phase angle which is then carried out by generating an ideal three-phase signal. The proposed method is simulated and implemented in a three-phase active power filter controller. The test results show the improvement in the performance of the P-Q Theory under non ideal main voltages with THD 7.21% to THD 3.29%.</span>

A Comparison of Finite Control Set and Continuous Control Set Model Predictive Control Schemes for Model Parameter Mismatch in Three-Phase APF

Model predictive control (MPC) methods are widely used in the power electronic control field, including finite control set model predictive control (FCS-MPC) and continuous control set model predictive control (CCS-MPC). The degree of parameter uncertainty influence on the two methods is the key to evaluate the feasibility of the two methods in power electronic application. This paper proposes a research method to analyze FCS-MPC and CCS-MPC’s influence on the current prediction error of three-phase active power filter (APF) under parameter uncertainty. It compares the performance of the two model predictive control methods under parameters uncertainty. In each sampling period of the prediction algorithm, different prediction error conditions will be produced when FCS-MPC cycles the candidate vectors. Different pulse width modulation (PWM) results will be produced when CCS-MPC solves the quadratic programming (QP) problem. This paper presents the simulation results and discusses the influence of inaccurate modeling of load resistance and inductance parameters on the control performance of the two MPC algorithms, the influence of reference value and state value on prediction error is also compared. The prediction error caused by resistance mismatch is lower than that caused by inductance mismatch, more errors are caused by underestimating inductance values than by overestimating inductance values. The CCS-MPC has a better control effect and dynamic performance in parameter mismatch, and the influence of parameter mismatch is relatively tiny.

A Novel Multilevel Controller

Active power filter is an important means to improve power quality, and power topology is an important part of active power filter. Therefore, the research on power topology has important practical value. This paper proposes a simple-structure topology that employs eight switching power devices, two capacitors, and eight diodes to realize nine-level voltage output. The proposed topology can effectively reduce the volume and weight of the device and achieve multilevel output. Simultaneously, a compound control strategy, consisting of integrated phase voltage control and cell capacitance voltage control, is proposed for unit voltage equalization control. Finally, taking the three-phase active power filter as the research object, simulation and experimental verification are carried out with the proposed topology. The results show that the proposed topology and control scheme are feasible, and in the case of sudden load change, the fluctuation of capacitor voltage V1 is less than 3 V, the fluctuation of capacitor voltage V2 is less than 1 V, and the THD (Total Harmonic Distortion) of the phase current is well suppressed to 3.84%.

A Novel Multi-vector Model Predictive Current Control of Three-Phase Active Power Filter

This paper proposes the application of a novel finite control set model predictive control (FCS-MPC) strategy in active power filter (APF). In the process of APF compensating harmonic and reactive power, the traditional single vector model predictive current control (MPCC) has low tracking accuracy to harmonic current, while the multi-vector MPCC has the problems of complex calculation and long calculation time, a new multi-vector MPCC control method has proposed in this paper. Firstly, the harmonic reference value is transformed into d-q coordinate system, according to the sector, the slope is calculated and the action time is obtained. Six new expected vectors are synthesized from six effective vectors and zero vectors. The value function is established to loop and calculate the optimal virtual vector, which is applied to APF. Compared with single vector control and traditional multi-vector control, it has a wider vector action area and faster calculation speed. The compensation results and dynamic performance are improved. The simulation results show that the total harmonic distortion (THD) is low.

Current model predictive control for three-phase active power filter using cascaded H-bridge multilevel converter

Current model predictive control for three-phase active power filter using cascaded H-bridge multilevel converter

Harmonic compensation of APF based on unconstrained CCS-MPC

Active power filter (APF) is a device that can suppress harmonics and compensate reactive power. In order to improve the ability of three-phase active power filter (APF) to track and compensate harmonics in real time, an unconstrained CCS-MPC method based on state space model is proposed. Compared with variable constraint, it has faster response speed and less computation. Firstly, the time domain model of APF is established, and the discrete space state model is changed. The system state and output prediction equations are established iteratively to solve the objective function. The closed-loop solution of APF following harmonic is solved by using the open-loop objective function to achieve the purpose of feedforward and feedback. Finally, the simulation model is established, and the results show that the method has better dynamic response, steady-state characteristics and robustness.

Nonlinear control of active power filter based on LQR control

In order to improve the ability of real-time tracking and compensating harmonic of three-phase active power filter (APF), a nonlinear sliding mode control strategy of APF is proposed based on the state feedback linearization theory. In order to improve the dynamic performance and tracking ability of APF system, the affine nonlinear model of APF system is established, and the nonlinear control strategy of current inner loop is designed. The control parameters are adjusted by LQR method. In order to adjust and stabilize the DC voltage of the system, the slip mode control (SMC) is used to design the voltage outer loop. The simulation and experimental platform are built. The experimental results show that the method has good dynamic response, steady-state characteristics and robustness.

The influence of nonlinear load on the autonomous electrical network at parallel work of the active power filter

Purpose. The purpose of the article is to investigate the modes of operation of a three-phase active power filter in the composition of an autonomous electrical network when connected to a network of three-phase nonlinear load of different spectral character.Methodology. For the research, the provisions of the pq-theory of power, the theory of electrical circuits, the theory of automatic control, mathematical modeling in the Matlab package were used.Findings. The graphs and spectral composition of the mains voltage and load current have been obtained, which makes it possible to evaluate the effectiveness of using a power active filter in the filtration mode as part of an autonomous electrical network, which is a synchronous generator. Originality. The efficiency of the parallel operation of a power active filter in the filtration mode with a synchronous generator at an abruptly variable nonlinear load is proved.Practical value. The use of the proposed technique will make it possible to create a three-phase power active filter for its use in autonomous electrical networks, represented by a synchronous generator with automatic regulation of the excitation voltage.

Multistep finite-control-set model predictive control of active power filter

The traditional finite-control-set model predictive control (FCS-MPC) of three-phase active power filter (APF) has the problems of low compensation precision and long control delay. In order to address this problem, this paper proposes a multistep prediction compensation control method for the FCS-MPC of APF, it does not require modulation of PWM link. By utilizing the discrete mathematic model of three-phase parallel APF and keeping the advantages of traditional FCS-MPC, the prediction model is established based on the structural model of traditional FCS-MPC, the predictive controller is designed for predictive control of DC-side voltage. AC-side current and fixed switching frequency, and simulation study is also conducted. The simulation results show that the multi-step predictive control method can effectively track and compensate harmonic, reduce the harmonic component of power grid, and increase the compensation precision of parallel APF.

An Improved Control Method Based on Source Current Sampled for Shunt Active Power Filters

Active power filters (APFs) are dynamic power electronic devices that suppress harmonics and reactive power. To simplify the detection and extraction of traditional APF harmonics and reactive current, this paper proposes a direct source current control based on a three-phase three-wire shunt APF. The compensation principle and control method of the source current are analyzed systematically. The currents can be controlled without static errors by a proportional-integral (PI) controller in d-q rotating coordinates. Therefore, the compensation accuracy and dynamic performance of the system can be improved by the control strategy. Moreover, considering the grid voltage fluctuations, a droop regulator is proposed to address the impact of DC-link voltages on APF power losses and compensation performance. The regulator is combined with a traditional voltage outer loop PI control to achieve a comprehensive optimization between the power loss and compensation performance of the APF system. Finally, the inner current loop and the outer voltage loop form a double closed-loop cascade PI control structure to achieve the control effect of the APF. Simulation and experimental results verified the validity and feasibility of the APF control approach.

Adaptive Nonlinear Control of Three-Phase Series Active Power Filters with Magnetic Saturation

The problem of controlling three-phase series active power filters (series APF) is addressed in the presence of nonlinear loads. In previous works, the control design for series APF is generally based on standard models that assume the involved magnetic coil to be linear. In reality, the magnetic characteristics of these components are nonlinear. In this paper, a new model for series APF load system, taking into account for the nonlinearity of coil characteristics, is developed. Based on the new model, a nonlinear adaptive controller is developed, using the backstepping design. The control objectives is twofold: (i) compensating for the harmonic and disturbed voltages components at the point of common coupling, this objective is referred to network voltage quality; and (ii) regulating the inverter DC capacitor voltage. Moreover, the controller is made adaptive for compensating the uncertainty on the switching loss power. The performances of the proposed adaptive controller are formally analyzed using tools from the Lyapunov stability and average theory. The supremacy of the proposed controller with respect to standard control solution is illustrated through simulation.

Adaptive RBF neural network based on sliding mode controller for active power filter

In this paper, an adaptive radical basis function neural network (RBFNN) is proposed to deal with dynamic tracking error problems which are the mathematic model uncertain or complex for the three-phase active power filter (APF). The adaptive RBFNN systems are employed to approximate the system function term f^(x) in the sliding mode controller. Different from back propagation neural network (BPNN), RBFNN is local uniformly convergence so that it enhances the convergence speed of weights. According to Lyapunov stability analysis guarantee the control algorithm stable implementing that is working out the adaptive law and dragging the states onto the sliding surface and sliding along it. This approach is almost model-free requiring a minimal amount of a priori knowledge and is robust in the face of parameter changes. The simulation results of APF demonstrate the outstanding compensation performance and strong robustness.

Adaptive RBF neural network based on sliding mode controller for active power filter

In this paper, an adaptive radical basis function neural network (RBFNN) is proposed to deal with dynamic tracking error problems which are the mathematic model uncertain or complex for the three-phase active power filter (APF). The adaptive RBFNN systems are employed to approximate the system function term f^(x) in the sliding mode controller. Different from back propagation neural network (BPNN), RBFNN is local uniformly convergence so that it enhances the convergence speed of weights. According to Lyapunov stability analysis guarantee the control algorithm stable implementing that is working out the adaptive law and dragging the states onto the sliding surface and sliding along it. This approach is almost model-free requiring a minimal amount of a priori knowledge and is robust in the face of parameter changes. The simulation results of APF demonstrate the outstanding compensation performance and strong robustness.

Adaptive backstepping second-order sliding mode fuzzy control for three-phase active power filter

Because of the heavy use of electrical equipment, harmonic pollution is becoming more and more serious, which brings potential safety risks to our lives. In view of the fact that active power filters can effectively eliminate harmonics, an adaptive second-order sliding mode fuzzy control based on the backstepping method is proposed to eliminate harmonics in this article. The second-order sliding mode control can eliminate chattering in the system and results in a smoother controller. The uncertainties in the system are approximated by a fuzzy control system, and the adaptive laws are designed to ensure the stability of the system. Backstepping control can improve the stability and robustness of closed-loop systems. Simulation results show that the proposed method has better tracking effect, strong robustness, and stability and can effectively eliminate harmonics.

THD Reduction Using Shunt Active Power Filter: A Real Case Study

Harmonic pollution in the industrial field causes extra heat dissipation and increased rms (root mean square) values of both voltage and current waveforms, which hence increase losses, decrease the overall efficiency, and increase the energy cost in power plants. Moreover, harmonic pollution results in a decline in industrial investment. A solution to mitigate harmonic pollution is proposed using an active power filter by identifying both the phase current and the voltage and then providing a compensation current the same in magnitude and negative in direction to the distorted current. In this paper, a three-phase active power filter for current harmonic compensation in power distribution lines is adopted. Practical measurements performed on the United Iron and Steel Manufacturing Company bus bar for different factory and Jordanian national power system grid loads demonstrate the validity of the proposed approach using a shunt active power filter (SAPF). Using p-q theory, the results show that the proposed SAPF is convenient for suppressing harmonic current. Hence, the overall power quality of the grid is improved, and the reliability is enhanced. Finally, this work is implemented using simulink/Matlab.