Harmonic Distorted Load Control in a Microgrid

The increase and decrease of non-linear load and impact load of power grid lead to lower and lower power quality, which has become a hot issue in reactive power compensation and harmonic suppression technology research. As one of the AC output equipments, the static synchronous compensator has strong compensation performance and can provide technical support for no power compensation. Therefore, based on the theory of instantaneous reactive power, the current detection method and related control technology of the static synchronous compensator are proposed, and finally the experimental simulation is carried out. The simulation results show that the improved detection algorithm can detect the reactive current of the system efficiently and accurately. Using STATCOM current detection method and control technology, it can adjust reactive power in time, compensate for actual power demand, further suppress system voltage fluctuations and improve system performance.

The most common reference current detection methods for shunt active power filters are optimized and compared in this article, theoretically and through experimental tests. One used discrete Fourier transform (DFT), d-q axes theory, p-q Instantaneous Reactive Power (IRP) theory and Sinusoidal Signal Integrators (SSI). MATLAB/Simulink software is used because it provides specialized tools in order to design, implement and simulate these algorithms. Afterward they are implemented in a real-time setup using a digital signal processor (DSP) based solution with dSPACE controller board. For the performance comparison one used criteria like total harmonic distortion (THD) and unbalance of detected fundamental current, run time for the DSP, settling time, transient performance and overshoot. This study contributes to the existing comparisons in specialized literature by testing the algorithms under distorted and non-symmetrical PCC voltages and may be useful for hardware implementations.

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

A generalized theory of instantaneous reactive power for three-phase power systems is proposed in this paper. This theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal, balanced or unbalanced, three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A three-phase harmonic distorted power system with zero-sequence components is then used as an example to show reactive power measurement and compensation using the proposed theory.

This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal, balanced or unbalanced, three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

Modular Multilevel Converter (MMC) provides promising features for medium/high voltage applications. In this paper, Shunt Active Power Filter (SAPF) with MMC is coupled to Medium Voltage (MV) non-linear load. The SAPF is controlled using instantaneous real and reactive power (p-q) theory to compensate the oscillating power and consequently the supply current harmonics resulting in supply current with acceptable Total Harmonic Distortion (THD). A MATLAB/ Simulink simulation model is used to investigate the performance of a 12-level MMC-SAPF compensating a MV diode converter.

Aiming at the unreasonable phenomenon that the different harmonic power will be cancelled out in the current harmonic background, a harmonic energy measurement algorithm is proposed to improve the instantaneous reactive power. First, the three-phase voltage and current signals are constructed by the delay of single-phase voltage and current signals. Then by changing the rotational speed of the p-q coordinate system in the instantaneous reactive power theory, the signals of different frequency harmonics in the voltage and current are obtained after filtering. Finally, the active power and reactive power of the system are obtained by the power conversion. This method can not only measure the power in positive and backward separately, but also avoid the unreasonable phenomenon of the positive and reverse power offset when the electric energy is measured, and can be used in the single phase system and the three-phase system. Finally, the simulation results of Matlab verify the effectiveness and accuracy of the proposed method.

The paper presents the structure of an active parallel filter for reducing harmonic pollution and reactive power. The active power filter control is based on instantaneous reactive power theory. The authors present the modelling of parallel active filter based on this theory and the simulation results in MATLAB-SIMULINK. The method is based on instantaneous reactive power (TPRI_P).

This paper proposed a cascaded H-bridge multilevel inverter based direct connected active power filter for medium/high voltage application without using the bulky transformer or passive filter. Due to the limited switching frequency (typically below 1 kHz) of high-power solid-state devices (GTO/IGCT), multiple synchronous/stationary reference frame current controller are reviewed and derived. To improve the dynamic performance, a hybrid frame structure based current controller is presented. Furthermore, a direct power controller is then proposed based on the understanding between the instantaneous reactive power (IRP) and synchronous reference frame (SRF) theory, ft has clear physical meaning and can be considered as a simplified version of the hybrid frame current controller. Simulations on a 4160 V/1.2 MVA system and experimental results on a 208 V/6 KVA laboratory prototype are presented to validate the proposed active power filter design.

Integrating Solid Oxide Fuel Cells (SOFCs) with the electrical grid and diesel generators at the point of common coupling forms a hybrid power system. However, power converters and nonlinear loads contribute to voltage drops and current distortions, especially under dynamic and imbalanced load conditions. Transient mismatches between supply and demand can lead to voltage instability, while the electrochemical response of SOFCs causes oxidant flow disturbances, accelerating H2 starvation, O2 imbalance, thermal stress, and efficiency loss. This study proposes a novel Adaptive Neuro-Fuzzy Inference System (ANFIS)-controlled Adaptive Tunable Shunt Active Power Filter (AT-SHAPF) to enhance power quality in Solid Oxide Fuel Cell (SOFC)-driven hybrid systems under unbalanced supply and nonlinear load conditions. The core contribution lies in employing ANFIS for intelligent real-time compensation of harmonics and reactive power, outperforming conventional Proportional-Integral (PI) and Fuzzy Logic Controllers (FLC). The system is evaluated using MATLAB/Simulink to analyze key performance metrics: Total Harmonic Distortion (THD), Current Distortion Factor (CDF), and true power factor. Without compensation, THD reaches 29.31% and 28.68% under steady and dynamic load conditions, respectively. With compensation, PI-based AT-SHAPF reduces THD to 5.88% and 5.46%, FLC-based to 3.22% and 4.03%, and ANFIS-based to 1.63% and 1.98%. Additionally, the Instantaneous Reactive Power Theory (IRPT) is applied for real-time reference current generation, enabling precise compensation. The proposed ANFIS-controlled AT-SHAPF demonstrates superior adaptability, power factor correction, and harmonic suppression compared to traditional methods.

In this paper, it uses PSCAD/EMTDC to build simulation system of STATCOM (Static Synchronous Compensator). According to the principle of coordinate transformation and the theory of instantaneous reactive power, it creates self-defined components in PSCAD/EMTDC. The working principle of the system is explained fistly.Then the theory of instantaneous reactive power and the diagram of simulation system is presented. Each functional module is also discussed in detail. Through the simulation test, it emphatically analyzes real-time tracking ability of the system when the capacitive and inductive loads are added. In this way, correctness and validity of the system has been proved.

This paper deals with the presentation of different terms of the powers presented in the Instantaneous Reactive Power Theory (IRPT) in the general case of a generic power system voltage. This presentation is based on the use of the symmetric components in the E. Clarke stationary frame, where the instantaneous real active power, the instantaneous imaginary reactive power and the instantaneous zero sequence power are divided into their DC components and AC components function of the symmetric components. The contributions of these terms in the transfer of the energy from the power supply to the load in four wire system are explained, hence, a good choice of the power to be compensated using shunt active power filter can be obtained. Finally, simulation results are presented under unbalanced and distorted generic power system voltages, where different terms of the instantaneous reactive power theory are clarified and presented based on symmetrical components.

The Unified Power Quality Conditioner (UPQC) is a technology that has successfully addressed power quality issues. In this paper, a photovoltaic system with battery storage powered Unified Power Quality Conditioner is presented. Total harmonic distortion of the grid current during extreme voltage sag and swell conditions is more than 5% when UPQC is controlled with synchronous reference frame theory (SRF) and instantaneous reactive power theory (PQ) control. The shunt active filter of the UPQC is controlled by the artificial neural network to overcome the above problem. The proposed artificial neural network controller helps to simplify the control complexity and mitigate power quality issues effectively. This study aims to use a neural network to control a shunt active filter of the UPQC to maximise the supply of active power loads and grid and also used to mitigate the harmonic problem due to non-linear loads in the grid. The performance of the model is tested under various case scenarios, including non-linear load conditions, unbalanced load conditions, and voltage sag and voltage swell conditions. The simulations were performed in MATLAB/Simulink software. The results showed excellent performance of the proposed approach and were compared with PQ and SRF control. The percent total harmonic distortion (%THD) of the grid current was measured and discussed for all cases. The results show that the %THD is within the acceptable limits of IEEE-519 (less than 5%) in all test case scenarios by the proposed controller.

The use of power electronic devices and their control find wide range application in domestic and industrial loads. These loads are highly nonlinear and when connected to the system, draw highly nonlinear current and inject harmonics into the system. Injected harmonics cause low system efficiency and reduced power quality. Harmonic currents are known to be reduced by using conventional passive filters. However, the disadvantage of these filters is their bulky size and fixed harmonic order compensation. In order to reduce current harmonics and improve power quality, a shunt active power filter (SAPF) is used in this study. It is based on instantaneous reactive power theory (p-q theory) and synchronous reference frame (SRF) theory. The simulation findings demonstrate that the SRF theory operates effectively in both balanced and unbalanced supply and load situations. In contrast, the p-q theory is unable to maintain the desired total harmonic distortion (THD) specified in IEEE Standard 519-2014 in case of unbalanced supply condition.

Distributed power generation has got its importance with the day to day increase of power generation from renewable energy sources and from domestic customers with small generation units connected to the grid.Distributed power generation systems mostly use Power electronic converters for the interface with power grid.Here in this paper a single-phase inverter for DG systems requiring power quality features, such as harmonic and reactive power compensation for grid-connected operation are discussed.The idea is to integrate the DG unit functions with shunt active power filter capabilities.With this approach, the inverter controls the active power flow from the renewable energy source to the grid and also performs the nonlinear load current harmonic compensation by keeping the grid current almost sinusoidal.The control scheme employs a current reference generator based on sinusoidal signal integrator and instantaneous reactive power (IRP) theory together with a dedicated repetitive current controller.Simulation results obtained with PI and fuzzy controllers demonstrate the feasibility of the proposed solution.