Reduce Bus Voltage Research Articles

Distributed power conditioning unit of large-scale space solar power station

In this paper, a multi-bus distributed Power Conditioning Unit (PCU) is proposed for the Space Solar Power Station with large scale photovoltaic (PV) array and power levels reaching MW level. In this unit, there are multiple independent PV arrays. In each PV array, there are multiple independent PV subarrays. In this paper, a V-P droop control method with adaptive droop coefficient is proposed, which modifies the droop intercept based on the bus voltage deviation and the power per unit value of the PV array. This method ensures the accuracy of bus voltage and achieves proportional distribution of power between PV arrays based on the proposed topology structure in this paper. When the load changes or the output power of the PV array fluctuates, this method can ensure that power is distributed proportionally. The principle and control method of the proposed droop control method is analyzed in this paper. The effectiveness of the method is verified through MATLAB/Simulink simulation and experiment. Simulation and experimental results show that the proposed method can achieve power distributed proportionally when load changes and PV output power fluctuates, reduce bus voltage error caused by line impedance and differences in rated power of different PV arrays, and improve the performance of PV power generation system applied to space.

A Novel Single-Stage AC/DC Converter Integrated Interleaved DCM Boost PFC and LLC DC–DC With Reduced Bus Voltage

Due to the applied pulse frequency modulation (PFM) control and switch integration, single-stage Boost-LLC AC/DC converters suffer from high bus voltage which makes them difficult to operate for high voltage input. To solve this issue, a novel single-stage AC/DC Converter by incorporating the interleaved DCM boost cell and an LLC cell is proposed. Different from the existing topology, in the proposed converter, two capacitors employed for splitting the ac input voltage into two parts are placed before the rectifier bridge. Thus, the voltage across each PFC cell is halved and the bus voltage can be significantly reduced. Furthermore, two high-frequency diodes and one filter capacitor are omitted, which helps improve the zero-crossing distortion of the input current. More importantly, the circuit efficiency is thus increased. Hence, low bus voltage, low component count, and high efficiency are the main advantages of the proposed converter. Simulations and experimental results are presented to prove the above features of the proposed converter.

PV integrated shipboard MVDC grid with reduced bus voltage ripple

Integration of renewable energy sources for power generation is a proven solution to reduce the increasing greenhouse gas emissions towards decarbonisation onboard ships. Also, it is easy to integrate a variety of energy sources in an all-electric ship under medium voltage direct current distribution system. In such distribution system, high frequency switching power converters are greatly involved on the source and the load sides, which are massive source of harmonics. In this paper, a grid connected photovoltaic module is designed and paralleled with the generator, as a step towards reducing greenhouse gas emissions. Additionally, to take care of the voltage ripple and noise created by the high frequency switching power converters in the system, a shunt direct current electric spring with a control strategy is incorporated. The proposed system eliminates the use of heavy passive filters, commonly used at the rectifier end. MATLAB/Simulink results substantiate that the increased voltage ripple with the inclusion of energy sources and loads, that goes around 10.91% under fully loaded condition, is reduced to 1.27% with the shunt direct current electric spring, hence well within the IEEE 1709 std., which is less than 5%.

Conditional-Extreme-Point Based Fault-Tolerant Predictive Control of Five-Phase PMSM With Low Switching Frequency

The virtual voltage vector (VVV) based fault-tolerant control has been widely concerned, but suffering from the increased switching frequency and the reduced bus voltage utilization at the faulty operation. Also, the harmonic space is uncontrollable. This paper proposes a conditional-extreme-point based fault-tolerant model predictive control for a five-phase permanent magnet synchronous motor. The conditional extreme point is used to predict the optimal reference voltage vector. Firstly, to suppress the harmonics, dual control sets are established without the sacrifice of bus voltage utilization. Then, the unconditional extreme point and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -axis voltage are predicted to select the appropriate control set, and two adjacent vectors are pre-selected for generating the optimal reference voltage vector. Subsequently, the conditional extreme point of the cost function is calculated to obtain the optimal reference voltage vector. Due to the unemployment of the null vector, the switching frequency is greatly reduced. Finally, the experimental results are presented to verify the proposed control scheme.

Research on improved linear auto-disturbance rejection control of hybrid energy storage in optical storage microgrid

Photovoltaic power generation has uncertainties such as randomness and volatility. In order to ensure the stable operation of the power system, hybrid energy storage technology is introduced to improve the voltage stability of the optical storage microgrid. Traditional PI control still needs some help in response speed and overshoot. Facing the hybrid energy storage microgrid system with nonlinear and strong coupling characteristics, in order to improve power quality and reduce bus voltage fluctuation and impact, this paper designs an improved active disturbance rejection control (ADRC) integrated energy storage control system based on a fuzzy algorithm, Based on the traditional double closed-loop PI control, the fuzzy LADRC is used to replace the voltage outer loop, and the system model is built on the MATLAB/Simulink platform for simulation. The results show that the proposed control strategy has a smaller overshoot, faster dynamic response time, and good anti-interference ability compared with the traditional PI and ADRC, which improves the dynamic performance of the photovoltaic energy storage system while stabilizing the bus voltage fluctuation and ensures the stable operation of the powergrid.

A Family of Single-Stage AC/DC Converters Integrated Interleaved PFC and Resonant DC/DC Circuits

To address the high bus issue of conventional boost or buck-boost PFC integrated resonant DC/DC type single-stage converters under high voltage input, a family of single-stage AC/DC converters integrated interleaved PFC and resonant DC/DC circuits is proposed in this paper. Unlike traditional solutions, the AC input voltage of the proposed three interleaved PFC structures is divided into two parts by two capacitors before the rectifier bridge. Thus, two high-frequency power diodes and one filter capacitor are omitted. Furthermore, the reduced bus voltage can be simultaneously obtained with fewer devices. Correspondingly, a better zero-crossing performance of input current can be achieved theoretically. Most importantly, the circuit efficiency also can be increased. Using the common LLC circuit as DC/DC stages, simulations in PSIM are performed to verify the improved zero-crossing of input current. To introduce the proposed converters, the operation principles, design considerations, experimental results, and related comparisons for the proposed structure II with LLC cell are presented comprehensively, achieving at least a 2.3% improvement in efficiency under 220Vac nominal input and 100W load conditions, while maintaining reduced bus voltage and similar PF values. In addition, the experimental results of the topology I and III are also given to prove the validity of the proposed family converters.

Coordinated active and reactive power control for distribution networks with high penetrations of photovoltaic systems

A primary concern of the large-scale application of photovoltaic (PV) power systems in distribution networks is nodal voltage fluctuations caused by active power fluctuations of PV. Therefore, this paper proposes a novel coordinated active and reactive power optimization method for distribution networks with high penetrations of PV systems, which can reduce bus voltage fluctuations, active power curtailments of PV, operating losses of distribution networks, and adjustments of conventional voltage regulation devices such as on-load tap changers (OLTCs) and capacitor banks (CBs). The proposed method coordinates the OLTC, CBs, and PV and BESS plants in two levels. The upper level establishes a mixed integer nonlinear programming (MINP) model based on the model predictive control (MPC), which can properly plan the operation of the OLTC, CBs, and PV, and a modified NSGA-II algorithm is developed to find the best solution of the MINP model. The lower level employs the leader–follower consensus algorithm (LFCA) to coordinate the charging power and reactive power of distributed battery energy storage systems (BESSs) to control real-time bus voltage fluctuations. The LFCA based control method can make BESSs fairly participate in the real-time voltage regulation of each feeder. Case studies are conducted on a modified IEEE 33-bus distribution network system, utilizing the actual active power data of a PV plant. Simulation results indicate that the proposed method can effectively control bus voltage variations of all feeders within the pre-defined range, and the distribution network can operate with higher penetrations of PV power systems, lower losses, and better economy.

Multilevel Energy Management of a DC Microgrid Based on Virtual-Battery Model Considering Voltage Regulation and Economic Optimization

This article presents a multilevel energy management framework for dc microgrids with multiple energy storage systems (ESSs) to ensure reliable power dispatch, stable voltage regulation, and daily economic operation. In the primary layer, an advanced virtual-battery drooped control is constructed for the ESSs, which can realize adaptive load sharing and state of charge (SOC) balancing. Decentralized bus-signaling control is proposed to prevent single point of failure, where the mode-switching voltages of the utility grid and photovoltaic system are adjustable based on the VirtualOCV curve of the virtual-battery model. A current feedforward control strategy is scheduled as the secondary control to reduce bus voltage deviation, which is verified through simulation. A small-signal model is developed to investigate the effects of the virtual-battery parameters, SOC value, and constant power load on system stability through root locus analysis. In the energy management level, an improved particle swarm optimization algorithm is applied to obtain the optimal setting of the virtual-battery model parameters for minimum daily operating costs. A discrete model is derived from calculating the capacity loss of the batteries. Finally, the proposed control hierarchy is verified in the MATLAB/Simulink environment and the simulation results prove the feasibility and priority of the proposed multilevel energy management.

Hierarchical control of DC microgrid with dynamical load power sharing

The hierarchical control strategy is proposed for DC microgrid with distributed generators, energy storage systems and loads. In order to maintain power balance and smooth bus voltage fluctuation during system operation due to dynamic load and resource variation, the designed hierarchical control is divided into two layers. In the primary layer, the novel adaptive droop controller with voltage feedback compensation is constructed for distributed generators and energy storage systems by taking advantage of local electrical parameters, which can realize the dynamic load power sharing and reduce bus voltage deviation. The distributed generators may operate between maximum power point tracking mode and droop control mode by bus regulation units when power supply is larger than the loads demand and the charging capacity of energy storage systems. The state of charge can also be adjusted for energy storage through the designed adaptive droop scheme. On the other hand, the secondary supervisory control is designed to reduce power exchange and improve the system stability. Using the designed hierarchical control, the DC microgrid can operate in four different modes according to which source responsible for the bus voltage stabilization. Simulation and comparison results validate that the proposed strategy may smooth the bus voltage fluctuation and realize the dynamic power sharing.

Multi-Objective Hybrid WIPSO–GSA Algorithm-Based DG and Capacitor Planning for Reduction of Power Loss and Voltage Deviation in Distribution System

In electric distribution system, majority of load connected are inductive in nature and it results in increased system power loss and reduced bus voltage profile. In this study, in order to overcome these issues, optimal planning of DG and capacitor are presented by optimizing multiple objectives such as minimization of total active power loss (Plosstotal) and reduction of voltage deviation (VD). Here, a hybrid configuration of weight improved particle swarm optimization (WIPSO) and gravitational search algorithm (GSA) called hybrid WIPSO–GSA algorithm is proposed to solve the optimization problem in multi-objective problem domain. In order to solve multi-objective optimization problem, the proposed hybrid WIPSO–GSA algorithm is integrated with two components. The first component is fixed-sized archive that is responsible for storing a set of non-dominated Pareto optimal solutions and the second component is a leader selection strategy that helps to update and identify the best compromised solution from the archive. The proposed methodology is tested on standard 33-bus and Indian 85-bus distribution system. Moreover, the total economic benefit due to optimal DG and capacitor planning are established and also the superiority of the proposed technique is illustrated by comparing the results with other existing optimization techniques.

Implementation of a low cost, compact single stage power converter with reduced bus voltage stress

Over the recent past, many methodologies to reduce DC bus voltage stress in the single stage single switch power quality converter have been proposed in the literature. The new development resulted in increased efficiency, reduced size and compactness. In this paper, a simple and inexpensive solution with a simple control for the reduction of DC bus voltage stress is proposed. This topology is the integration of discontinuous conduction mode (DCM) boost rectifier for the input current shaping and flyback converter for fast output voltage regulation. With a single active switch, this converter is capable of drawing high quality input current waveform, fast output voltage regulation with reduced bus voltage. No additional component is required to reduce DC bus voltage stress. A design solution and a simple controller is proposed to reduce DC bus voltage stress. As a result, this converter is best suited for universal line application (90-265 V AC). Performance of the converter, design guidelines, small signal analysis, and stability analysis are carried out.

Implementation of a low cost, compact single stage power converter with reduced bus voltage stress

Implementation of a low cost, compact single stage power converter with reduced bus voltage stress

Stability design for on‐board distributed power system

AbstractRecently, on‐board distributed power systems consisting of bus converter and POL have usually been used for IT infrastructure equipment. However, even if each converter has stable operation, the bus voltage may oscillate and the system may be unstable, depending on the bus converter design; this has been a serious problem in recent years. Solution of the issue is highly desirable, and in order to improve the system stability various techniques have been discussed. This paper investigates the improvement of the system stability by the control method. The availability of full‐regulated bus converter is especially examined. It is determined that the full‐regulated method is the optimal control method for the bus converter because a full‐regulated bus converter can reduce bus voltage oscillation and adjust to input voltage variations flexibly by regulation. A stability design process is proposed for an on‐board distributed power system using a full‐regulated bus converter. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(7): 18–25, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20356

Virtual instrument measures harmonic filter duty

Harmonic filters for a static VAr compensator (SVC) suppress power frequency harmonics generated by the nonlinear characteristic of the thyristor controlled reactors and electric arc furnace loads. SVC filters also provide the 60 Hz capacitive current needed by the SVC to reduce bus voltage flicker. Following reactor and capacitor failures the reliability of the SVC filter was improved. The first step was to measure the SVC filter stresses which was performed using a virtual instrument. The measurement equipment consisted of a personal computer equipped with two analog-to-digital (4/D) input boards, two signal conditioning input boards, and commercially available instrument and control software capable of configuring these basic hardware components for user defined instrumentation and analysis. Virtual instruments were used to sample, store, analyze, and display 32 channels of high speed data for 55 minutes of the combined furnace heat cycle. The author discusses the virtual instrument software, measurement and analysis technique, and statistical analysis. >