Reactive Power Control Method Research Articles

Performance Comparison of Reactive Power Control Methods of Photovoltaic Micro-inverter

Photovoltaic power generation becomes an important technology in recent year, because of its advantages such as clean energy, pollution reduction, no gas emissions, maintenance and operation requirements are low. So it is a new path for generating electric power. This paper will study the performance comparison of two photovoltaic systems of three-phase grid-connected micro-inverter and study their design methods of reactive power control. The first design is suggested that the photovoltaic PV system based on an interleaved DC-DC boost type converter with its maximum power point tracking control (MPPT) for each boost converter. A voltage source inverter type (VSI) is used as a three-phase micro-inverter. By controlling the direct and quadrature components of inverter output currents, reactive power controlling is achieved at 90.76% efficiency. The second design is suggested that the photovoltaic panel is connected DC-DC converter of an interleaved flyback type. Each sub-converter is controlled by an individual (MPPT). The circuit of active third-harmonic current injection in recent years have received much interest, this technique contributed to get better quality of current injected into the utility grid and to control the reactive power with good efficiency 95.07%. A line-commutate current source inverter type (CSI) with filter is used. The developed micro-inverter of (1000W) offers an expanded range of reactive power control with balanced three-phase output power. Each system design in this study has proven its effectiveness in obtaining control of reactive power and nearly sinusoidal three-phase output currents. The effectiveness of the suggested systems are clarified by using the MATLAB Simulink program and the results of the simulation show the validity of the suggested micro-inverter system.

Nodal Sensitivity-Based Smart Inverter Control for Voltage Regulation in Distribution Feeder

Overvoltage is one of the issues in distribution grids with high penetration of photovoltaics (PVs). Centralized or droop-based methods of active power curtailment (APC) and/or reactive power control of PVs are viable solutions to prevent overvoltage. This article proposes two distributed methods to control PV inverters, which are based on nodal sensitivities. Then, the performance of the proposed methods is compared with two commonly used control methods, i.e., a distributed method that follows IEEE-1547 but uses arbitrarily chosen droops and a centralized optimal power flow (OPF) based method. Performance is evaluated using a 730-node feeder with up to 100% penetration of inverters. Based on the case studies, the key findings are: first, local droop setting as per IEEE-1547, whether the droops are arbitrarily chosen or systematically calculated using sensitivities, can eliminate overvoltage if reactive power control and APC are coordinated, second, the proposed sensitivity-based approach yields the best voltage performance index computed based on voltage profile compared to the maximum allowed upper bound, and third, OPF-based method is desirable if communication infrastructure exists and minimum energy curtailment is sought.

Two-stage ADMM-based distributed optimal reactive power control method for wind farms considering wake effects

Since the connection of small-scale wind farms to distribution networks, power grid voltage stability has been reduced with increasing wind penetration in recent years, owing to the variable reactive power consumption of wind generators. In this study, a two-stage reactive power optimization method based on the alternating direction method of multipliers (ADMM) algorithm is proposed for achieving optimal reactive power dispatch in wind farm-integrated distribution systems. Unlike existing optimal reactive power control methods, the proposed method enables distributed reactive power flow optimization with a two-stage optimization structure. Furthermore, under the partition concept, the consensus protocol is not needed to solve the optimization problems. In this method, the influence of the wake effect of each wind turbine is also considered in the control design. Simulation results for a mid-voltage distribution system based on MATLAB verified the effectiveness of the proposed method.

Islanding detection method for distributed generation with wavelet based nuisance tripping suppression

This paper deals with modified reactive power control (RPC) for islanding detection. The RPC approach is an effective technique for detecting islanding in distributed generation (DG). However, existing RPC methods have limitations of injecting/drawing unnecessary reactive power into/from the grid. Furthermore, RPC methods may be affected by disturbances such as power system transients resulting in false islanding detection. This paper proposes a new controller’s reference reactive power based on the positive sequence voltage of the point of common coupling (PCC) and a reactive mismatch coefficient to overcome the aforementioned drawbacks. Furthermore, the Discrete Wavelet Transform (DWT) of the difference between the amplitude of actual and nominal PCC voltages is incorporated in the decision criteria. An entropy function based on DWT is defined to improve the reliability of the RPC method under disturbances. The proposed islanding detection method (IDM) is evaluated under various load and disturbance conditions to show its performance. Simulation and experimental finding indicate that the proposed IDM can detect islanding quickly and with a negligible Non-Detection Zone. Moreover, the DG and load reactive powers are nearby matched during the normal operation, and non-islanding events are effectively prevented.

Islanding Detection Method With Load Power Factor Improvement and High Frequency Transient Suppressing

Reactive power control (RPC) strategy is a promising option for islanding detection in distributed generation (DG) systems. Existing RPC methods have drawbacks of not providing the reactive power to improve the load power factor and are not robust against high-frequency transient disturbances. This paper presents a modified RPC method to overcome these limitations in a 220/380 V distribution network. In this method, the reference of reactive power of the DG is designed to improve the load power factor and ensure a fast islanding detection. In addition, the proposed method incorporates a second decision-making criterion based on discrete wavelet transform (DWT) to avoid false islanding detection due to non-islanding events. The proposed islanding detection method (IDM) is tested under various conditions. Simulation and experimental results show that the proposed IDM can detect islanding rapidly and with zero Non-Detection Zone (NDZ) in the situation of load power factor improvement. Moreover, non-islanding events such as capacitor switching are effectively avoided.

A Novel Direct Active and Reactive Power Control Method Using Fuzzy Super Twisting Algorithms and Modified Space Vector Modulation Technique for an Asynchronous Generator-based Dual-rotor Wind Powers

This work presents a novel direct active and reactive powers command (DARPC) scheme based on fuzzy super twisting algorithms (FSTAs) of an asynchronous generator (ASG) integrated into dual-rotor wind power (DRWP) systems. The DRWP has two sets of blades. So it is more efficient for collecting power from wind in comparison to a traditional wind turbine. The scientific works indicate that a DRWP could extract additional 20-30% power compared to a traditional wind turbine. The conventional DARPC control scheme using the conventional integral-proportional (PI) regulators (DARPC-PI) has considerable reactive and active power oscillations. In order to guarantee an effective DARPC technique for the ASG-based DRWP system and minimize these oscillations, FSTAs are used in this work. Both DARPC strategies are presented and simulated from two tests using Matlab software. Simulation results showed the effectiveness of the designed DARPC control technique especially on the quality of the provided active and reactive power comparatively to the traditional DARPC control scheme with PI controllers.

A Cooperative Voltage Control Method for Distribution Network Based on DSTATCOM and ES

In recent years, with the large‐scale access of distributed generation (DG), the line voltage of the distribution network will be offset, which will adversely affect users. This paper aims at the voltage adjustment of the distribution network. Firstly, the reactive power control methods of distributed static synchronous compensator (DSTATCOM) and electric spring (ES) are studied separately, and then a layered cooperative control strategy based on them is proposed, which combines centralized compensation and distributed compensation to stabilize the entire line voltage. The upper layer aims at optimizing the comprehensive factors including voltage offset, user comfort and cost, and applies the dynamic adaptive particle swarm optimization (DAPSO) algorithm to study the optimal scheme of voltage adjustment. The lower layer designs the control loops of the compensation devices in response to the reactive power instruction. Finally, simulation results show that the voltage of the distribution network is effectively controlled. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Anti-Disturbance Finite-Time Adaptive Sliding Mode Backstepping Control for PV Inverter in Master–Slave-Organized Islanded Microgrid

With the aim to solve the problem related to the power chattering and anti-disturbance performance of a photovoltaic (PV) inverter in master–slave-organized islanded microgrid, an anti-disturbance finite-time adaptive sliding mode backstepping (DFA-SMB) controller is designed in this paper. First, the topology and the second-order dynamic model of PV inverter are established based on constant DC voltage and constant reactive power control method. Subsequently, the backstepping method is adopted to perform the control of a high-order system. Moreover, a second-order sliding mode differentiator is used to realize the function of command-filter, solving the differential expansion problem caused by the derivation of virtual controller. Besides, the terminal sliding mode control (TSMC) is introduced into the q-axis controller and d-axis inner loop controller, increasing the robustness and reducing the convergence time of the system. Adaptive control and disturbance-observer (DO) are used to perform the adaptive estimation of model parameters and the observation of lumped disturbances, respectively, enhancing the dynamic characteristics of the controller. Finally, a master–slave-organized islanded microgrid with 100 kW PV array is established in MATLAB/Simulink. The results demonstrate that the proposed control method can effectively reduce power chattering and improve the anti-disturbance ability of the PV system.

Reactive Power Control Method for Enhancing the Transient Stability Total Transfer Capability of Transmission Lines for a System with Large-Scale Renewable Energy Sources

With the increased proportion of intermittent renewable energy sources (RES) integrated into the sending-end, the total transfer capability of transmission lines is not sufficient during the peak periods of renewable primary energy (e.g., the wind force), causing severe RES power curtailment. The total transfer capability of transmission lines is generally restricted by the transient stability total transfer capability (TSTTC). This paper presents a reactive power control method to enhance the TSTTC of transmission lines. The key is to obtain the sensitivity between TSTTC and reactive power, while the Thevenin equivalent voltage is the link connecting TSTTC and reactive power. The Thevenin theorem states that an active circuit between two load terminals can be considered as an individual voltage source. The voltage of this source would be open-circuit voltage across the terminals, and the internal impedance of the source is the equivalent impedance of the circuit across the terminals. The Thevenin voltage used in Thevenin’s theorem is an ideal voltage source equal to the open-circuit voltage at the terminals. Thus, the sensitivities between TSTTC and the Thevenin equivalent voltages of the sending-end and receiving-end were firstly derived using the equal area criterion. Secondly, the sensitivity between the Thevenin equivalent voltage and reactive power was derived using the total differentiation method. By connecting the above sensitivities together with the relevant parameters calculated from Thevenin equivalent parameter identification and power flow equation, the sensitivity between TSTTC and reactive power was obtained, which was used as the control priority in the proposed reactive power control method. At last, the method was applied to the Gansu Province Power Grid in China to demonstrate its effectiveness, and the accuracy of the sensitivity between TSTTC and reactive power was verified.

A Hybrid Reactive Power Control Method of Distributed Generation to Mitigate Voltage Rise in Low-Voltage Grid

A high penetration of distributed generators, such as solar and wind power generators in low voltage network systems, impose voltage rise problems. Reactive power control of distributed generators can contribute to mitigating the voltage rise. In the existing reactive power control, reactive power was controlled using only one local variable, such as voltage at point of connection or the active power output of distributed generator. In case of PF(P) method, which provides certain power factors, depending on the active power of distributed generator, the voltage regulation ability is strong, but network losses are large. Q(V) method, which provides a certain amount of reactive power depending on the local voltage, has few network losses, but the voltage regulation ability is weak. In this paper, a reactive power control method that combines the PF(P) method and Q(V) method was proposed. The proposed method determines the reactive power output by using the active power of the distributed generator and local voltage variables together. The proposed method improves the voltage regulation ability of the reactive power control, while reducing the network losses, as compared to the existing method. The low voltage network system was modeled and simulated to evaluate the performance of the proposed method, in terms of voltage regulation ability and network losses, and the performance of the proposed method and the existing method were compared and analyzed.

A Cyber-Physical Cooperative Hierarchical Control Strategy for Islanded Microgrid Facing With Random Communication Failure

At present, more and more communication-based methods are proposed for reactive power adjustment in islanded microgrid (IMG). However, the use of communication data will inevitably cause communication problems, for e.g., delay, packet loss, and communication failure. Among them, the random communication failure (RCF) is common and harmful. To realize the stable operation of IMG and the rational sharing of reactive power under the consideration of this problem, a cyber-physical cooperative hierarchical control strategy is proposed in this article, which include cyber and physical layers in control structure. In these two layers, the main designs are as follows. In the cyber layer, to solve the RCF problem, we have designed the corresponding observer, controller, and prediction compensation part; and to improve the frequency stability, a secondary control method is designed. In the physical layer, to share reactive power reasonably, a reactive power control method based on synchronous voltage regulation is proposed; to suppress the possible disturbance in the data used in the physical layer, a novel sliding-mode controller is designed; and to improve the voltage stability during adjusting power, a voltage compensation strategy is proposed. The effectiveness of proposed methods is finally verified by experiments.

Multi‐mode adaptive local reactive power control method based on PV inverters in low voltage distribution networks

Low voltage distribution networks with the high penetration of photovoltaic (PV) units are facing four types of challenges, including over-voltage issues, under-voltage issues, voltage fluctuation issues and high power losses. In order to mitigate the above issues, this study proposes a multi-mode adaptive local reactive power control method based on Q(P) characteristics. A new concept, node virtual injection active power (NVIP), is developed to take the PV active power, load active power and load reactive power as a whole and as the basis to regulate the PV reactive power. Then, an NVIP-based multi-mode local Q(P) framework is proposed to consider the four types of challenges based on four operation modes, respectively, that can be adaptively switched according to the NVIP value and the NVIP variation. In addition, a systematic parameter design for the Q(P) framework is proposed based on an optimisation model to further enhance the effectiveness of the proposed multi-mode control. The simulation results demonstrate the effectiveness of the proposed method in mitigating voltage violations and voltage fluctuations, and improving the power losses and power factor.

Tracking technique for the sudden change of PV inverter load

Many power electronics applications require a power calculation in the control system. To get a suitable output, engineers need to control the process and regulate the power exchange with the grid. Since real and reactive power calculations are so crucial a topic, a novel control strategy for a single-phase photovoltaic (PV) inverter has been developed. Therefore, Direct power control (DPC) and a single-phase three-level space vector pulse width modulation (SVPWM) combine as a control and modulation system. In this paper, predictive real and reactive power control and SVPWM method are conferred in the inner loop. A voltage controller based on a proportionalintegral (PI) scheme is used in the outer loop to acquire constant output voltage and provide power refers to the DPC. The performance of the proposed method is verified by using MATLAB/SIMULINK.

Reactive Power Control Method for the LCC Rectifier Side of a Hybrid HVDC System Exploiting DC Voltage Adjustment and Switched Shunt Device Control

We present a new reactive power control method for hybrid high-voltage direct-current (HVDC) systems that features a line-commutated converter-based (LCC) rectifier and a voltage-sourced converter-based (VSC) inverter. Our principal objective is to regulate the reactive power of the LCC rectifier side via co-operative control of the DC voltage and switched shunt devices (SSDs) such as capacitors and reactors. To achieve these objectives, we used three operative modes: reactive power, voltage, and power factor control. For each mode, we show how to determine the DC reference voltage. Also, to maintain the voltage within operational bounds and enhance the range over which reactive power is controllable, our method features the cooperation of SSDs. Furthermore, we show how to determine the required SSD capacities. MATLAB and PSCAD simulations confirmed that our method improves reactive power controllability at the LCC rectifier side of a hybrid HVDC system.

A review of wind power generation utilizing statcom technology

This paper provides overview of wind energy development from ancient period to present and focus on grid power generation as well as wind power generation. By comparing wind power generation, it has increased trice compared to last 3 dotages. Due to rapid requirement of wind power, power converter technology placed a major role in developing the wind power generation. Since the wind energy technology is very complex for developing wind energy effectively so in this paper we are focusing for an reactive power control method due to which the output power can be control very effectively by using Static Synchronous Compensator called COM.Since in wind power generation it is very essential to get variable output. And STATCOM can vary the output according the requirement by absorbing or generating the reactive power in the system. For recognizing the potential issues and planning a system to reduce them, an exhaustive know-how is required. Coordinating elevated amounts of wind control calls for additionally control and remunerating types of gear to encourage recuperation from framework unsettling influences with high level of seriousness. This paper tosses light into utilizing adequately, a Static Synchronous Compensator (STATCOM) for settling the matrix voltage following network side unsettling influences.

Grid-Synchronization Stability Analysis and Loop Shaping for PLL-Based Power Converters With Different Reactive Power Control

Power converters may lose synchronization with the remaining network when integrated in a weak power grid. Such an instability phenomenon [known as grid-synchronization instability (GSI)] features the frequency divergence of phase-locked loop (PLL) and oscillations of the converter’s power output. In this paper, we focus on the influences of reactive power control (RPC) methods on GSI. We develop a single-input–single-output model to explicitly reveal how the PLL interacts with the other parts of the converter system in terms of grid synchronization. Then, after deriving the open-loop transfer function and sensitivity function of the entire converter system, we compare the stability margins for different RPC methods. Furthermore, we elaborate on the interactions among RPC, PLL, and voltage feedforward (VFF), and then demonstrate that different design methods of RPC and VFF will lead to different stability margins. The subsequent stability analysis provides insightful guidelines for coordinating the design of multiple control loops, i.e., RPC, VFF, and PLL. In particular, we demonstrate how the loop shaping of PLL takes effect in increasing the stability margin and eventually preventing the converter from GSI. The validity of the stability analysis is verified through simulations in MATLAB/Simulink.

An Efficient Hybrid AC Metro Power Supply System Integrating PV With Grid

Metro is integral to the urban rail transit with the expansion of the city. Due to the tremendous power consuming of the traction load which is generally considered to be megawatt class, the attendant problems concerning energy-saving and emission-reduction cannot be neglected. An approach wherein the photovoltaic plants are connected into the metro traction power supply system to provide electrical energy is proposed in this paper. Given the deterioration of power quality brought about by PV connection, the photovoltaic inverter adopts output reactive power control method.

Static Operational Impacts of Residential Solar PV Plants on the Medium Voltage Distribution Grids—A Case Study Based on the Danish Island Bornholm

Driven by the Energy Strategy 2050 of Denmark, renewable energy sources (RESs) are increasingly integrated into the Danish power grid. Solar photovoltaic (PV) plants play an important role in this process. This paper conducted a study to investigate the impacts of residential solar PV integration in the distribution grid on voltage security and grid loss based on the 10 kV distribution grid in Bornholm. Three case studies are performed to test three different reactive power control methods, i.e., PF(P), constant PF and constant Q, at different penetration levels. The assessment of the impacts of PV integration and different control methods are done in the DIgSILENT PowerFactory. It was found that PV integration can contribute to reducing the loss of the system, increased overvoltage in buses and overload in transformers, and 40% penetration at the low voltage is considered to be an optimal level based on the result. PF(P) control gives the best performance among all three methods under the current grid codes. With constant PF control, it was found that the system loss can be significantly reduced if the PV systems operate with a power factor of 0.9 leading, which is not the norm of the current Danish grid code.

Reactive Power Control Method for Grid-Tie Inverters Using Current Measurement of DG Output

The penetration ratio of distributed generation (DG) has increased due to the depletion of fossil fuels and the impacts of global warming. Thus, overvoltage at the point of common coupling may occur since reverse current flows with the installment of DG. To solve this problem, this paper presents a reactive power control method based on the measured current at the point of common coupling of DG. The purpose of this paper is not to provide methods to improve the voltage profiles of distribution lines through the reactive power control, but to maintain the voltage after the DG connection as before the connection. By applying the proposed method in this paper, it is possible to significantly improve the penetration ratio of DG by restricting the voltage rise. Case studies, using MATLAB simulation, are performed to verify the feasibility of the new reactive power control method.

Distributed Reactive Power Control and SOC Sharing Method for Battery Energy Storage System in Microgrids

Battery energy storage system (BESS) is a pivotal component to increase the penetration of renewable generation and to strengthen the stability and reliability of the power system. In this paper, for the purpose of the state of charge (SOC) balancing and reactive power sharing, a multiagent system (MAS)-based distributed control model, which contains a top layer communication network built by agents and a bottom-layer microgrid composed of BESSs, distributed generators (DGs), and Loads, is provided. Next, a systematic method is designed to build the control laws for agents from any given network, where each agent on the top communication network collects the states of BESSs, DGs it connects and exchanges information with its neighboring agents. Moreover, two theorems, which provide guidelines to design distributed control laws for SOC balancing and reactive power sharing between BESSs, are proposed to show the convergent property of the proposed control laws. Furthermore, several simulation cases are employed to validate the effectiveness of the proposed control model when environmental conditions and time-varying load demands are considered. Finally, the simulation results verify the effectiveness of the proposed control model, i.e., the SOC balancing and proportional reactive power sharing are achieved as expected. Furthermore, our approach has the fast convergent speed of SOC balancing of BESSs, compared to the existed method.