Evaluation of Residential PV‐EV System for Supply and Demand Balance of Power System

In recent years, there has been a growing interest in ecofriendly technologies such as residential photovoltaic (PV) systems and electric vehicles (EVs). PV systems and EVs will contribute to reducing CO₂ emissions in the residential sector and the transportation sector, respectively. In spite of that, high penetration of PV systems into the power grid can cause grid voltage and frequency stability problems. Also, the growth of the EV market will create an extra electricity load (for charging the EV fleet), leading to an increase in power utility fuel costs. In this research, we proposed the usage of the PV‐EV system as a method of mitigating the impact the spread of residential PV systems and EV on the power grid. We built an PV‐EV system simulation model and investigated the PV‐EV system contribution to the balance of power supply and demand and to reducing the total cost of the household under different electricity pricing scenarios. We also evaluated the effect of uncertainty in the forecasting of load and PV output on the performance of the PV‐EV system.     

Maximum potential of PV installation based on an energy system planning model considering a distribution voltage constraint

As the key solution for energy sustainability this decade, the growth of installing photovoltaic (PV) systems has dramatically increased. However, the high penetration of PV systems can cause a voltage variation problem in a distribution grid. This paper proposes a model for evaluating the maximum potential for installing PV systems in an urban area under a bus voltage constraint. A PV system is considered as an energy system alternative that replaces a conventional system. Regarding the power variation, it is necessary to add a parameter that is used to evaluate the variation of PV systems in terms of a standard deviation to the PV systems' electric load curve. The installations of PV and conventional systems are determined as share solutions for each load area along a distribution network. Total power loads and variations in each load area are input to a load flow calculation to obtain each bus voltage and confirm the voltage constraint. Finally, the total PV system installations over the whole network area is maximized. The alternative PV system with battery installation is introduced to validate the model evaluation when comparing with a typical PV system without a battery, which has larger power variation. Furthermore, adjusting the sending voltage at a substation to increase the PV installation is validated using the proposed model. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis of possible introduction of PV systems considering output power fluctuations and battery technology,employing an optimal power generation mix model

This paper presents an evaluation of the impact of extensive introduction of photovoltaic (PV) systems and stationary battery technology into the optimal power generation mix in the Kanto and Kinki regions. The introduction of solar PV systems is expected to be extensively deployed in the Japanese household sector and utility companies in order to address the concerns of energy security and climate change. Considering this expected large‐scale deployment of PV systems in electric power systems, it is necessary to investigate the optimal power generation mix which is technologically capable of controlling and accommodating the intermittent output‐power fluctuations inherent in PV systems. Against this background, we develop both a solar photovoltaic power generation model and an optimal power generation mix model, including stationary battery technology, which can be used to explicitly analyze the impact of PV output fluctuations at a detailed time interval resolution such as 10 minutes for 365 consecutive days. Simulation results reveal that PV introduction does not necessarily increase battery technology due to the cost competitiveness of thermal power plants in the load‐following requirement caused by PV systems. Additionally, on the basis of sensitivity analysis on PV system cost, dramatic cost reduction proves to be indispensable for PV to supply bulk electricity similarly to thermal and nuclear power plants. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(2): 9–19, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22329     

基于Non-MPPT算法的区域光伏消纳控制策略

基于两级式光伏发电系统环境自适应算法以及光伏阵列分布式结构,提出一种适用于区域光伏消纳控制的Non-MPPT（maximum power point tracking）算法,力主解决光伏发电系统出力过剩问题。该算法基于光伏模块分布式前级优化器,实现不同环境下光伏模块分散控制,并通过光伏模块输出电压、电流随机变量,导出光伏电池环境修正参数,进而实时修正区域光伏模块最大功率电压,使其最大功率电压实时跟随外部环境变化,并结合电导增量法,实现不同环境下光伏阵列全局最大功率跟踪。而后,若区域性电网光伏发电系统出力过剩,则将区域光伏按其实际出力情况进行分区管理,以区域电网对其出力分配额度为控制目标,推导出光伏阵列对应输出电压,并将其引入至光伏发电系统前级Boost电路,通过修正Boost电路占空比,使光伏发电系统输出功率快速跟随主网需求指令,解决了区域内光伏过剩出力的消纳问题。最后,通过Matlab/Simulink仿真软件搭建两级式三相光伏并网系统,验证该算法在电力系统应用中的有效性。     

光储系统功率波动平抑策略研究

光伏发电直接并网会对电网的安全稳定运行造成威胁,利用储能系统对光伏功率进行平抑可以减小功率波动对电网的冲击.文中提出了一种基于最小二乘法的平抑控制算法,根据发电曲线的波动程度自动调整算法参数,同时实现波形的平滑和跟踪.通过建立蓄电池寿命模型仿真验证了该方法的有效性.相较于传统滤波算法,该方法在满足平抑目标的同时,能够减...     

Phase‐Locked Loop Using Complex‐Coefficient Filters for Grid‐Connected Inverter

Recently, photovoltaic (PV) power systems have attracted considerable attention in attempts to mitigate global warming. In a PV power system, it is necessary to synchronize the grid voltage when a PV inverter is interconnected with a grid. This paper proposes a high‐speed and high‐precision phase‐locked loop (PLL) using complex‐coefficient filters for a single‐phase grid‐connected inverter. The proposed PLL can detect the phase of grid voltage that has superimposed harmonic components for grid fault. Moreover, numerical results show the effectiveness of the proposed method.     

A Two‐Stage Stochastic Mixed‐Integer Programming Approach to the Smart House Scheduling Problem

A “smart house” is a highly energy‐optimized house equipped with photovoltaic (PV) systems, electric battery systems, fuel cell (FC) cogeneration systems, electric vehicles (EVs), and so on. Smart houses are attracting much attention recently because of their enhanced ability to save energy by making full use of renewable energy and by achieving power grid stability despite an increased power draw for installed PV systems. Yet running a smart house's power system, with its multiple power sources and power storages, is no simple task. In this paper, we consider the problem of power scheduling for a smart house with a PV system, an FC cogeneration system, and an EV. We formulate the problem as a mixed‐integer programming problem, and then extend it to a stochastic programming problem involving recourse costs to cope with uncertain electricity demand, heat demand, and PV power generation. Using our method, we seek to achieve the optimal power schedule running at the minimum expected operation cost. We present some results of numerical experiments with data on real‐life demands and PV power generation to show the effectiveness of our method. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 48–58, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22336     

H‐infinity controller for frequency and voltage regulation in grid‐connected and islanded microgrid

This paper presents a study on a grid‐connected and islanded multiple distributed generation (DG) system for frequency and voltage regulation. The multiple DG system includes solar cells, wind turbine, fuel cell, and battery storage. The H‐infinity controller is used whose weighting parameters are optimized to minimize voltage and frequency deviation. The performance of the system is analyzed under different conditions for both grid‐connected and islanded modes of operation. In case of the load variations, the inner voltage and current loop react based on the H‐ infinity control strategies. The outer power loop uses the droop characteristic controller. The design is simulated using MATLAB/SIMULINK. The simulation results show that the multiple DG system can supply high‐quality power both in grid‐connected and islanded modes. Also, we show that the proposed control methodology will make the system to transit smoothly between the islanded mode and the grid‐connected mode. The results indicate that the frequency and voltage deviations meet the nominal values as per IEEE standard. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

光伏直流微网协调直流电压控制策略的研究

直流微电网是新能源发电接入常规公用电网的一种有效方式,并以其显著的优势成为微电网技术研究的一个新方向。本文以光伏发电系统、储能系统、交直流负荷组成的直流微电网为研究对象,在分析该直流微电网运行状态的基础上,提出了直流电压协调控制策略。该控制策略根据直流电压的变化量以及蓄电池的荷电状态SOC(State of Charge)自动协调各换流器的工作状态,从而实现了在各种运行工况下直流微电网内的有功功率平衡,达到了维持直流母线电压稳定的目的。最后,在Matlab/Simulink仿真环境下进行了仿真实验,结果验证了该控制策略的有效性。     

不平衡电网电压下光伏并网逆变器滑模直接电压/功率控制策略

不平衡电网电压下,光伏并网逆变器的输出功率和输出电流都将产生波动,给电力系统的稳定运行造成不利影响。根据光伏并网系统的数学模型,提出了光伏并网逆变器基于滑模控制的直接电压/功率控制策略。该控制策略可在电网电压不平衡时有效抑制并网逆变器输出有功功率和无功功率的波动。根据光伏并网逆变器输出功率和正、负序电流的关系,提出了以消除负序电流为控制目标的改进控制策略。此外,为提高系统的运行性能,提出了功率电流协调控制策略。最后,对所提出的控制策略进行了仿真分析,仿真结果验证了所提出控制策略的有效性。     

基于阻抗在线观测的光伏逆变器控制策略研究

光伏逆变器通常采用最大功率跟踪算法尽全力向电网注入有功功率,并不参与电网电压的控制。只有当电网电压超过了保护阈值,光伏逆变器才停止工作以避免引发过电压故障。提出一种光伏逆变器的电网电压控制策略,用以改善电网电压水平,使得光伏逆变器在非最优电网电压情况下依然可以向电网输送电能。根据电网电压控制效果由电网阻抗的阻抗比R/X决定的基本原理,所提出的控制策略在线观测电网阻抗比,实时控制光伏逆变器注入电网的有功功率和无功功率,改善光伏逆变器的电网电压控制效果。所提出的控制策略不仅适用于光伏逆变器,同样也适用于其他类型的分布式发电并网逆变器。     

基于PSASP的光伏并网系统建模与稳定性研究

在PSASP仿真环境下,开发了光伏并网发电系统中的光伏电池、MPPT控制器、蓄电池组、逆变器及DC-DC升压器的机电暂态模型,研究了光伏并网保护系统中的过/欠电压保护、过/欠频保护、过电流及短路电流保护、电压不平衡保护模型,应用这些模型建立了可用于电力系统稳定性分析的光伏电站仿真模型。最后,以接入光伏电站的某西部孤立电网为例,研究了光伏电源不同容量、不同功率因数接入方式对电网潮流的影响,以及故障扰动下的暂态稳定影响,验证了模型的正确性。     

Dynamic modeling of DC–DC converters with peak current control in double‐stage photovoltaic grid‐connected inverters

In photovoltaic (PV) double‐stage grid‐connected inverters a high‐frequency DC–DC isolation and voltage step‐up stage is commonly used between the panel and the grid‐connected inverter. This paper is focused on the modeling and control design of DC–DC converters with Peak Current mode Control (PCC) and an external control loop of the PV panel voltage, which works following a voltage reference provided by a maximum power point tracking (MPPT) algorithm. In the proposed overall control structure the output voltage of the DC–DC converter is regulated by the grid‐connected inverter. Therefore, the inverter may be considered as a constant voltage load for the development of the small‐signal model of the DC–DC converter, whereas the PV panel is considered as a negative resistance. The sensitivity of the control loops to variations of the power extracted from the PV panel and of its voltage is studied. The theoretical analysis is corroborated by frequency response measurements on a 230 W experimental inverter working from a single PV panel. The inverter is based on a Flyback DC–DC converter operating in discontinuous conduction mode (DCM) followed by a PWM full‐bridge single‐phase inverter. The time response of the whole system (DC–DC + inverter) is also shown to validate the concept. Copyright © 2011 John Wiley & Sons, Ltd.     

Applying control scheme function of PV inverter for minimizing voltage fluctuation and imbalance with consideration of maximum PV generation

At present, connections of photovoltaic (PV) systems to low‐voltage (LV) distribution systems are growing rapidly because of the compliance with government policies, drop in the prices of PV technologies, and environmental awareness. Unfortunately, the high penetration of solar PV systems, which suffers from the intermittence of sunlight, leads to voltage fluctuation and voltage imbalance, thereby deteriorating the power quality. To cope with this problem, this paper proposes a control strategy of the PV inverter to improve the limiting and balancing of voltage profiles in an unbalanced, three‐phase, four‐wire LV distribution system. The control strategy is based on the real power limitation and the reactive power adjustment through a control scheme function that is embedded in all PV inverters for supporting high penetration of PV systems. However, real power limitation leads to less utilization of solar energy. Then, the concern on PV generation (real power) regarding voltage fluctuation and imbalance is optimally analyzed by multi‐objective particle swarm optimization. The optimal solution of the control scheme function is numerically demonstrated in a modified 29‐node LV distribution system. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Voltage Control Using PV Power Factor,Static Capacitor,and Transformer Tap for Large PV Penetration

The Japanese government has set 53 GW as the target level of PV deployment by 2030. However, the large‐scale introduction of PV will cause several problems in power systems. One of these problems is the increase in voltage due to decreased load demands associated with large PV active power output. Another problem is voltage variations caused by fluctuations in PV system output. In this paper, we focus our attention on the voltage and reactive power control for large‐scale PV deployment and propose voltage control using the PF (PV power factor), SC (static capacitor), and TAP (transformer tap). In the proposed method, the SC and TAP controls consider voltage stability through the use of VMPI‐i and VMPI‐i sensitivity, and the PF control suppresses voltage variation and voltage spikes. Finally, we simulate these controls using the Ward–Hale system to verify the validity of the proposed method.     

Field test of a 70‐MW‐class superconducting generator in the mode of a synchronous condenser

In order to study the basic performance of the superconducting generator in an actual electric power system, a quick response excitation‐type generator was connected to the 77‐kV commercial power grid of Kansai Electric Power Co., Inc. In the test, the model machine was operated as a rotary condenser supplying about leading 40 M Var to the electric power system. In the tests, the model machine operated stably. The results show that the superconducting generator has effects for stabilizing voltage fluctuations of electric power systems and also for reducing shunt reactor. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 17–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10053     

Study of Low‐Voltage Ride‐Through Performance for Wind Power Generation with Doubly Fed Induction Generator

The introduction of wind power generation is increasing rapidly. The ratio of wind power generation to the total generation capacity is becoming higher and higher. When a phase‐to‐phase fault occurs in the power system, the frequency of the power system is lower due to disconnection of wind power generation with doubly fed induction generators (DFIG). Therefore, the power system might become unstable. This paper describes an LVRT (low‐voltage ride‐through) performance improvement scheme for wind power generation with DFIG. The wind power generator is disconnected from the grid in case of a power system fault. It is made to operate in isolation from the grid by controlling the inverters installed with the generators. After clearance of the power system fault, wind power generation is immediately reconnected to the grid. As a result, instability in the power system disappears. The performance of LVRT is confirmed by using the simulation software PSCAD/EMTDC. The simulation results show excellent results for the three‐phase short‐circuit fault with a voltage dip of 100%. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(1): 17–26, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22423     

Multi-input battery-integrated single-stage DC-DC converter for reliable operation of solar photovoltaic-based systems

Solar photovoltaic (PV) systems are emerging progressively due to their wide compatibility range, ease of installation, and environmental friendliness. The module mismatch (MM) losses and module open circuit (MOC) fault can cause the power mismatch between different PV modules. This significantly affects the energy output from the PV module. Also, the intermittent nature of solar PV power makes the solar PV systems unreliable; to compensate for this, conventional PV systems utilize a battery storage system (BSS) with separate bidirectional converter. These bidirectional converters require two-stage power conversion and massive battery bank connected at the DC link. This leads to the further reduction in overall efficiency. To address these issues, this paper proposed a multi-input PV battery system (MIPBS) that uses nonisolated buck and boost converter combinations. It requires single-stage power conversion to extract maximum power from each PV module along with BSS charging and discharging. Its modular design allows it to function across a wide range of voltage, power, and BSS choices. The proposed system is capable of mitigating the MM loss and sustaining the MOC fault. This paper discusses the operation, steady-state analysis, and dynamic analysis of the proposed MIPBS. The performance of the proposed MIPBS is validated using a state-of-the-art experimental setup with two PV modules, each having a rating of 60.53 W.     

大型并网光伏电站对电力系统影响的研究

光伏发电具有不确定性和波动性等特点,大型并网光伏电站对电力系统的稳定运行尤其对电网电压和发电机功角稳定产生一定的负面影响。以黑龙江省泰来县汤池9.9 MWp并网光伏电站为例,利用电力系统综合分析程序PSASP建立1个9.9 MWp光伏电站接入系统仿真模型,针对光伏电站接入系统后出现的电压和功角稳定问题进行深入分析。仿真结果表明,9.9 MWp并网光伏电站接入电网后不会对电力系统的电压和功角产生较大影响,为并网光伏电站的规模化开发提供有力依据。     

Multiple roles coordinated control of battery storage units in a large‐scale island microgrid application

In order to build a large‐scale island microgrid with 100% penetration intermittent photovoltaic power generation as the only power source, a structure with multiple role battery energy storage systems (BESSs) is proposed in this paper based on the analysis of energy storage demand in the island microgrid and performance comparison of two types of batteries. The storage system in the proposed structure is composed of three types of functional BESSs. In detail, the master control units (MCUs) with LiFePO4 batteries are responsible for the voltage and frequency stability and instantaneous power balance, slave storage units (SSUs) with lead‐acid batteries are responsible for daily energy storage, and multi‐function units (MFUs) with LiFePO4 batteries are used for short‐time energy regulation. A hierarchical control structure is adopted in the system. At the local level, the converters of the MCUs are controlled as the voltage sources in paralleled mode as grid‐forming units, and those of SSUs and MFUs are controlled in the current source mode as grid‐feeding units. At the system level, a real‐time power balance coordinated control strategy is proposed, which has the capability of efficient and orderly operation of different types of BESSs. Simulation and practical operation analysis of the Qumalai 7.023 MW microgrid demonstrate the practicality and effectiveness of the research methods of the island microgrid. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.