Instantaneous Reactive Power Theory Research Articles

Compensating voltage waveform distortions using a practical topology of series active power filters

Addressing harmonics, voltage sags, voltage swells, and asymmetrical variations is essential to seamlessly integrate renewable energy sources, electric vehicle charging stations, and power electronics devices into electric power grids. These issues can significantly impact the sinusoidal symmetry of voltage waveforms. Series Active Power Filters (APFs) present a promising solution that can dramatically improve power quality (PQ) by effectively addressing voltage distortions. This paper first identifies several topology-related impracticalities in the existing literature on series APFs, such as using nonlinear loads or linear loads with a current source. Secondly, to understand the motivations behind these impracticalities, commonly used reference extraction methods, namely, Instantaneous Reactive Power Theory (IRPT) and Synchronous Reference Frame (SRF), are tested on a practical topology consisting of a distorted voltage source and a linear RL load. Results conducted in the MATLAB/Simulink environment show that IRPT fails to extract the reference signal under the practical topology, and SRF leads to unacceptable THDs surpassing the 5% threshold mandated by relevant standards set forth for such applications. Thirdly, the matrix pencil method (MPM), a model-based parameter estimation technique that exploits a voltage waveform's underlying exponential signal model to extract the series APF's reference voltage, is proposed. Extensive simulations showcase the superior performance of the MPM-based series APF. It successfully reduces voltage total harmonic distortion (THD) to below 1.13% across various scenarios, including situations involving harmonic-polluted voltage sources, incorporating nonlinear loads, sag and swell phenomenon, and capacitor utilization in DC link implementation.

A new harmonic detection strategy based on improved series repetitive controller

SummaryThe d‐q detection method based on instantaneous reactive power theory (IRPT) is one of the commonly used time‐domain analysis methods for harmonic detection. Due to the poor dynamic performance of the algorithm caused by the low pass filter (LPF) in the d‐q detection method, an improved series repetitive control (ISRC) structure is proposed in this paper. Using attenuation factor and correction factor to improve the series repetitive controller, the ISRC contains a negative resonance peak with a peak value of 150 dB at the 6 k harmonic frequency, and the amplitude gain is 0 dB at frequencies outside the 6 k harmonic frequency. Therefore, ISRC can achieve good attenuation effect on 6 k harmonics while maintaining the same gain at other frequencies. ISRC is used instead of LPF in the traditional d‐q detection and this strategy improves the dynamic response of the system while guaranteeing its steady state performance. Finally, simulations and experiments verify the feasibility of the strategy.

Comparison of APF and STATCOM for Current Harmonic Mitigation

The application of solid-state electronic devices has recorded a geometric increase in the last decade. Devices such as battery charging systems, inverters, switch mode power supplies and a host of electronic-based devices referred to as non-linear loads distort the source signal (particularly the current). Harmonics distortion imposes a severe impact on the well-being of the power system. They cause excessive device heating, reduced performance efficiency, early insulation failure, decreased dynamic torque in rotating systems, etc. This paper bases a study on Active Power Filter (APF) and Static Synchronous Compensator (STATCOM) for mitigation of these distortive harmonics in a system of 3-phase 11kV/400V, 400kVA feeding a system of non-linear loads. The study is based on the IEEE519 standard limits for current harmonics measured at the PCC. Therefore, the system short circuit ratio (SCR) is first determined. Using synchronous reference frame and instantaneous reactive power theories, the APF and STATCOM are respectively designed and run using MATLAB/Simulink software. The result analysis is obtained from the FFT signal processing toolbox of the software, and the device’s performances are evaluated based on the set standard. Results from the FFT spectra showed that the model system contains a considerable number of harmonics before filtering. However, when these devices are connected to the system, all higher-order harmonics have been minimized to the least fractions with respect to the standard, with STATCOM giving a comparatively better performance.

Simulation and real time implementation of shunt active power filter for power quality enhancement using adaptive neural network topology

With the rise in non-linear loads, the need for a veracious power filter to alleviate voltage and current harmonics for meeting power quality has been a challenging requirement of the existing power system. This paper presents a systematic approach to improve power quality with a shunt active power filter (SAPF). The controller consists of a neural network approach to enhance the switching control of SAPF under dynamic and non-linear loading conditions. DC link voltage has been regulated using proportional-Integral (PI) control. To extract reference current, instantaneous-reactive power (IRP) theory has been used. IRP theory employing indirect current control strategy provides reference source current signals as well as regulated PWM switching signals for hysteresis control. An ADALINE network has been devised to extract fundamental signals from the polluted supply voltage. The model has been simulated on the MATLAB®/Simulink platform and validated by SAPF prototype in the laboratory using the TMS320F28335 floating-point DSP controller.

The performance of a multilevel multifunctional solar inverter under various control methods

Photovoltaic (PV) inverters are now supposed to provide additional supporting services with more reliability and efficiency. This paper presents three different control methods for generating reference current in a multifunctional, multilevel grid-tied PV inverter for harmonic, reactive, and unbalance compensation. These methods are the synchronous reference frame (SRF) theory (d-q), the instantaneous reactive power (IRP) theory (p-q), and the conservative power theory (CPT). As a result, the primary goal is to propose a low-cost multifunctional solar invert for distributed generation, with an appropriate prototype developed in the laboratory for experimental validation of various modes of operation. Demonstrated results show that the presented inverter is capable of providing various ancillary services with all three types of control.

Power quality improvement in distributed generation system using intelligent control methods

Hybrid <span>electric power generation and its integration with the grid to supply consumer demand is main focus of this paper. The use of nonlinear load and advanced power electronic equipment-based devices at the consumer end introduces power quality issues in the power system network in terms of voltage and current. This paper explains the design of a control algorithm for a unified power quality conditioner used for mitigating both voltage and current-based power quality issues. The dynamic voltage restorer of unified power quality controller (UPQC) is designed with a unit vector control algorithm and the distribution static synchronous compensator (DSTATCOM) is designed with fuzzy logic and adaptive network-based fuzzy inference system based instantaneous reactive power theory control algorithm. The simulation model built using the MATLAB platform includes a three-phase voltage source along with hybrid electric power generation connected to linear and non-linear loads operating under different conditions. The result is analyzed in terms of voltage and current total harmonic distortion compared with IEEE 512 power quality standards and power factor improvement. The paper shows the adaptive neuro-fuzzy inference systems (ANFIS)-based control algorithm gives better results in terms of total harmonic distortion (THD) compared to the fuzzy-based control algorithm. The power factor is improved using ANFIS-based controller proving the efficiency of the controller</span>.

Reduced sensor based single stage charger with four quadrant capabilities using predictive control

Single stage battery chargers eliminate the DC link capacitor stage between two stage power conversion. In this work, a reduced sensor based four quadrant charger with single stage power conversion is realized with AC–DC matrix converter topology. Although, a small capacitor filter on DC side is used in this configuration, it is only required to supply or absorb high frequency ripple component of the battery current, to prevent the battery from being damaged. The grid current estimation is done using the converter switching model and AC side filter model, leading to the elimination of grid current sensor. The simple model predictive control used here in conjunction with instantaneous reactive power theory, avoids the use of any proportional integral controller, thus making the control scheme simpler. The single stage design increases power density, and the charger’s dependability is increased by the absence of a large electrolytic capacitor. While the battery charges and receives power from the grid, the AC–DC matrix converter used here, performs a voltage bucking function. The simulation results and experimental findings from a lab-developed hardware prototype are used to validate the design and control of the proposed charger.

An accurate power control strategy for electromagnetic rotary power controllers

AbstractWith the rapid development of active distribution networks, the “petal”‐type distribution network has become the mainstream power supply structure. Power control methods for active distribution networks should be further studied to ensure the safe and reliable power supply of a distribution system. An electromagnetic rotary power flow controller (RPFC) is a feasible solution for controlling power in active distribution networks. However, when testing the effectiveness of the PQ decoupled control method for RPFC based on instantaneous reactive power theory, difficulties were encountered with the synchronous control of the rotor position angle of two rotating‐phase transformers, and the accuracy of power control was unsatisfactory. Given this condition, PQ control is improved in three ways. First, the system's periodic oscillation problem is solved via variable speed control. Second, the servo motor‐rotary phase‐shifting transformer synchronous rotation scheme, which reduces power control error and improves stability, is designed. Third, the overshoot phenomenon in power control is improved using the variable‐domain fuzzy proportional‐integral adaptive method. Experimental results show that the proposed advanced control scheme exhibits good dynamic and static performance in power control scenarios and achieves effective improvement in RPFC.

Investigation of power quality problems and harmonic exclusion in the power system using frequency estimation techniques

This work aims to investigate a problem with power quality and the exclusion of harmonics in the power system using a method called frequency estimation. This study aims to explore the performance of several strategies for estimating phase and frequency under a variety of less-than-ideal situations, such as voltage imbalance, harmonics, dc-offset, and so on. When the grid signals are characterized by dc-offset, it has been shown that most of the approaches are incapable of calculating the frequency of the grid signals. This article introduces a frequency estimation method known as Modified Dual Second Order Generalized Integrator (MDSOGI). This method accurately guesses the frequency under all of the unideal scenarios. Experiments have shown that the findings are accurate. In order to build a control scheme for a shunt active power filter that is able to function under such circumstances, the scheme is further integrated with the theory of instantaneous reactive power. In order to demonstrate enhanced performance, the experimental prototype is being created.

Güç Elektroniği Sistemleri için HIL (Hardware In The Loop) Simülatör Kartı Tasarımı ve Aktif Güç Filtreleri için Uygulanması

In this study, firstly, a general-purpose test simulator circuit was developed that could test the response of the circuits used in power electronics on hardware under various operating conditions (hardware in the loop). In the next step, a control board to be used for Shunt Active Power Filters (SPAF) was designed. The control software for SPAF was prepared using CubeMX IDE compiler for two different harmonic extraction methods using instantaneous reactive power theory (IRPT) and synchronous rotating reference frame (SRF) methods. Finally, before connecting the prototype SPAF control board and software to the real system, it had been verified to work safely using the designed test system. With this study, both the SPAF prototype circuit was prepared and a cost-effective system that could be found in the market was designed.

Research on Harmonic Management of Single-Phase AC Charging Pile Based on Active Filtering

Nowadays, AC charging piles are widely used, and with the increasing number of charging piles, the harmonic pollution generated by them becomes more serious and affects the power quality of the grid. Aiming at the problem of harmonic control of the single-phase AC charging pile, it is decided to apply the active filter technology. The single-phase parallel active filter (PAPF) is selected according to the characteristics of the charging pile. The single harmonic detection method is studied based on instantaneous reactive power theory, and a new adaptive low-pass filter with fixed-step size is proposed to improve the performance of harmonic detection by combining the least mean square (LMS) and the least fourth-order moment (LMF) adaptive algorithms. The PAPF control part adopts the composite control strategy of inner and outer loop combined with repetitive control to complete the voltage stabilization control, harmonic tracking, and compensation. Based on MATLAB/SIMULINK, the output waveforms of the low-pass filter link are simulated and analyzed, and the prototype experiment is carried out. The results verify that the algorithm can improve the performance of harmonic detection. Finally, the single-phase PAPF system simulation is established and the harmonic compensation capability of system is analyzed by the Fast Fourier Transform (FFT). The results demonstrate that single-phase PAPF can effectively manage harmonics and the total harmonic distortion (THD) is reduced to less than 5%.

Instantaneous Reactive Power Theory in the Geometric Algebra Framework

In this paper, a new approach for instantaneous reactive power analysis in the geometric algebra (GA) environment is presented. The different formulations of the instantaneous reactive power theory (IRPT) proposed, to date, have been developed in three-phase systems. There, an instantaneous power variable, and two/three reactive power variables, all handled independently, were introduced. Thanks to GA, it is possible to carry out a global treatment where an instantaneous power multivector is defined. Thus, in the same multidimensional entity all the power variables are included. From the instantaneous power multivector, the instantaneous power current and the instantaneous reactive current are determined. It should be noted that in this mathematical framework there is no limitation on the number of phases, and the extension of the IRPT to the analysis of multi-phase systems appears in a natural manner. In this study, a systematic approach with the most relevant definitions and theorems corresponding to the proposed methodology has been established. Two practical cases of five-phase and three-phase systems have been included to apply the new established formulation.

Power Quality Enhancement of Grid-Connected Renewable Systems Using a Matrix-Pencil-Based Active Power Filter

Power electronic converters are used for integrating renewable energy sources such as wind and photovoltaic into the grid. This integration gives rise to many challenges in power systems, especially regarding power quality. Indeed, integrated systems generate a non-linear current full of harmonics, which degrades power quality. Active power filters are usually used to compensate for these harmonics at the point of common coupling. In the control of active power filters, harmonics need to be extracted from the non-linear current. In this paper, the matrix pencil method―a model-based technique for estimating parameters of exponentially damped or undamped sinusoids in noise―is proposed to extract the reference signal in shunt active power filter applications. The performance of the proposed matrix pencil method is studied for current harmonic compensation and power factor correction under different modulation schemes and two DC links: an external DC voltage source and a capacitor. Using a capacitor for the DC link requires not only including a proportional-plus-integral controller to maintain a constant capacitor voltage, but also accounting for the loss current in the formulation of the matrix pencil method. Compared with the instantaneous reactive power theory and synchronous reference frame, results obtained from simulated data using MATLAB/Simulink under different loading conditions show that the proposed method corrects the power factor and affords a lower source current total harmonic distortion and fast response.

Neural Network Controlled Solar PV Battery Powered Unified Power Quality Conditioner for Grid Connected Operation

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.

Research on novel var compensator based on dual-rotary phase-shifting transformers and its control strategy

With the continuous increase in the penetration of distributed power with random output, the acceleration of the urban cableization rate and the rapid development of supergrid, the active distribution network puts forward higher requirements for the performance of dynamic reactive power compensation. A topology of novel rotary VAR compensator (NRVC) is proposed by integrating the current source static synchronous compensator with the continuous regulation characteristics of dual rotary phase-shifting transformers. The NRVC compensation principle is analyzed by establishing the steady-state mathematical model of dual rotary phase-shifting transformers and NRVC. The dynamic response performance and universal applicability are improved by considering its compensation capacity constraints, applying the instantaneous reactive power theory, and constant power factor control. A dual closed-loop decoupling control strategy of power outer-loop and current inner-loop is also presented to prevent internal overcurrent. Finally, the simulation and experimental results are performed to verify the effectiveness of the proposed system and control strategy, which realized bidirectional and continuous regulation of compensated reactive power, and has manifold advantages: low cost, strong shock resistance, large heat capacity, simple control, and no harmonic pollution.

Modified symmetrical sinusoidal integrator and instantaneous reactive power theory-based control of shunt active filter

Instantaneous reactive power theory (IRPT) based control of shunt active filter (SAF) is designed to work with balanced load currents and balanced as well as undistorted supply voltages. This can be overcome by individually pre-processing the supply voltages and load currents through the modified symmetrical sinusoidal integrator (MSSI) for the extraction of the respective positive sequence fundamental components, which can be further processed by the IRPT for the reference current generation. MSSI can reject harmonics and dc offset and extract the fundamental component. For proper functioning of MSSI, it is important that the coefficients of its transfer function are properly selected. This paper presents IRPT based control of SAF with pre-processing of supply voltages and load currents by MSSI. In this work, the coefficients for the MSSI are determined by comparing its characteristic equation with that of the standard third order system. The coefficients are selected such that the real poles of MSSI are closer to imaginary axis as compared to the complex conjugate poles. This results in system operating as a first order system with reduced settling time and peak overshoot, which is evident from the steady state and dynamic performance of the MSSI with selected coefficients. SAF operation with this MSSI for pre-processing the input signals for the IRPT based control, results in improved dynamic and good steady state response of SAF even under non-ideal grid conditions.

An Electromagnetic Var Compensator Suitable for Wind Power Access and Its Control Strategy

As the proportion of large-scale wind farms and distributed wind power connected to the power grid increases annually, the effects of their intermittent and random characteristics on the active and reactive power fluctuations of the power grid are becoming increasingly evident, causing frequent voltage fluctuations at the grid-connected point. To solve these problems, this study proposes a new topology of an electromagnetic var compensator (EVC) based on a rotary phase-shifting transformer (RPST). The EVC can work under capacitive and inductive conditions to compensate for inductive and capacitive power, respectively. In accordance with the parallel steady-state mathematical model of the EVC, a double closed-loop control strategy with high precision and considerable robustness is proposed for the EVC on the basis of instantaneous reactive power theory. Finally, simulations show that the topology of the proposed EVC exhibits bidirectional and continuous adjustment capability that can meet the reactive power compensation requirements of power systems with a high percentage of wind power. Compared with the existing reactive power compensation device, the EVC exhibits the advantages of high voltage, large capacity, low cost, strong impact resistance, and good tolerance, imbuing it with great prospects for development.

Instantaneous Reactive Power Control Based on Five-Level Inverter for Grid Connected PV System Improvement

Grid-connected photovoltaic systems have become the most important and popular use of the solar energy. In this paper, a photovoltaic system connected to a three-phase network is presented. The system is connected in a single step using a five-stage voltage source inverter to improve the quality of the power in the distribution system. The control strategy applied for the optimal operation of the photovoltaic system is based on the theory of instantaneous reactive power. This strategy is simple and has the advantage of running the system all day without using Phase-Locked Loop (PLL). The multilevel inverter switching signals are derived from the Pulse Width Modulated Current Controller, which provides good dynamic performance in both steady state and transient conditions. The voltage of the continuous bus capacitors is controlled using the PI controller. The validation of this proposed system is carried out through simulation with different levels of irradiations and by a comparison with the performance of a two-level inverter used in the original configuration. This specific configuration shows good results regarding the waveforms of the voltages and the output currents as well as the level of the quality of the energy represented in this paper by the THD parameter that has been studied in comparison with the two-level converter.

A novel optimizing PI control of shunt active power filter for power quality enhancement

In this paper, shunt active power filter (SAPF) is designed to address the problem of current harmonics in the source current arising from a nonlinear load and improve the quality of electric power. That will be by compensating reactive power and harmonic currents. The PI controller responsible for DC-link energy storage tuning was developed using the Lévy flight distribution algorithm (LFA). It is a novel, previously unused optimization approach to suggest relative gain Kp and integration gain Ki gain values for the PI controller. This approach aims to get the best dynamic performance of SAPF, speed up the convergence rate, get the fastest best stability and bypass constant voltage advancement for DC-link. The model was tested and implemented in MATLAB simulation software. The result of total harmonic distortion THD showed the efficiency of this method compared with the results of traditional PI. The design of the model in the current reference frame was based on instantaneous reactive power (pq) theory.

Harmonic detection technology based on ant colony optimization BP neural network

At present, ip-iq algorithm based on instantaneous reactive power theory is the most widely used in the field of harmonic detection.However, the ip-iq algorithm based on instantaneous reactive power has coordinate transformation and inverse transformation, which leads to cumbersome calculation.the existence of low-pass filter leads to delay and poor dynamic performance of the algorithm.The harmonic detection based on BP neural network has the advantages of simple calculation, fast detection speed, strong adaptive ability and good dynamic performance.However, the initial weights and thresholds are random, so it is easy for the network to fall into local optimal solution during training, resulting in low detection accuracy. This paper presents a harmonic detection method based on ant colony algorithm optimized BP neural network. ACO-BP, BP and ip-iq algorithms are compared by Simulink simulation. The results show that ACO-BP harmonic detection algorithm is feasible and superior