電氣專業(yè)外文翻譯---分布式能源和微電網(wǎng)綜述

1、<p><b>　　中文5615字</b></p><p>　　出處：J Driesen, F Katiraei. A review on distributed energy resources and MicroGrid[J]. Renewable and Sustainable Energy Reviews, 2008, 12(9): 2472-2483</p>

2、<p>　　附錄1：外文資料翻譯</p><p>　　原文： A review on distributed energy resources</p><p>　　and Micro Grid</p><p>　　1. Introduction</p><p>　　Due to the technology developm

3、ent and environment protection, some distributed energy resources (DER), such as internal combustion (IC) engines, gas turbines, micro turbines, photovoltaic, fuel cells and wind-power [1], have emerged within the distri

4、bution system. However, application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation and associated loads is a subs

5、ystem called “Micro Grid” (MG)</p><p>　　In [2], the MG concept assumes a cluster of loads and Micro Sources (MS) operating as a single controllable system that provides both power and heat to its local area.

6、 Refs. [2,3] introduce the benefits of MG, such as, enhance local reliability, reduce feeder losses, support local voltages, provide increased efficiency through using waste heat combined heat and power (CHP), voltage sa

7、g correction or provide uninterruptible power supply functions.</p><p>　　The MG is intended to operate in the following two different operating conditions: normal interconnected mode and emergency mode (isla

8、nded mode) [4]. MostDERs that can be installed in an MG are not suitable for direct connection to the electrical network due to the characteristics of the energy produced. Therefore, power electronic interfaces (dc/ac or

9、 ac/dc/ac) are required. </p><p>　　Inverter control is thus the main concern in MG operation. The MG is centrally controlled and managed by a MG central controller (MGCC) installed at the medium voltage/low

10、voltage (MV/LV) substation. The MGCC includes several key functions, such as economic managing functions and control functionalities, and is the head of the hierarchical control systems [4].</p><p>　　The aim

11、 of this paper is to review the researches and studies on MG technology. In Section 2, it will introduce some current situations about MG, especially in Europe and Japan. In Section 3, MG architecture is described, inclu

12、ding MS, storage devices, and inverters. In Section 4, two approaches in the MG emergency operation is discussed in details. Also the fault detection and safely analysis is included in this section. Last section introduc

13、es the MG in the market environment. Multi-agent syst</p><p>　　2. Current situations about MG</p><p>　　“MICRO GRIDS”project is part of the European Research Project Cluster”Integration of RES+DG

14、 (distributed generation)”projects. It will investigate, develop and demonstrate the operation, control, protection, safety and telecommunication infrastructure of MG and will determine and quantify their economic benefi

15、ts. This project aims at the increase of penetration of micro-generation in electrical networks through the exploitation and extension of the MG concept, involving the investigation of alte</p><p>　　Amorim e

16、t al. [6] presents a brief characterization, to a Portuguese LV grid, developed in MICROGRIDS project. This project is being developed in Frielas, which is a residential zone, supplied by a LV feeder from a public distri

17、bution power station of 200kVA. The paper focuses some improvements in terms of efficiency and reliability. It gives several conclusions. The control and protection hardware must be upgraded to allow the</p><p

18、>　　supplying of the customers in island mode; the transition from grid-connected mode to island mode should be analyzed carefully in order to prevent voltage disturbances in the MG; the MG black-start is other importa

19、nt challenge. Some tests have demonstrated the incapacity of the microturbine to support the transient peak demand of a typical distribution MV/LV transformer during its initial magnetization.</p><p>　　In Ja

20、pan, the New Energy and Industrial Technology Development Organization(NEDO) started three research projects, which deal with new energy integration to local power system field test in 2004 [7]. The sites are in Aomori,

21、Aichi and Kyoto. In Aomori project, field tests were started to develop a distributed energy supply system, in which some loads in special districts are supplied by this supply system with private power lines and makes n

22、o influence to utility power system with which the ener</p><p>　　Besides the ordinary ac-grid (alternating current) system, [8] proposes a dc-grid (directcurrent) system having distribution power generators.

23、 It has designed and constructed an experimental system based on a 10 kWdc having a solar-cell generator unit, a wind turbine generator unit, an electric power storage unit, power-leveling unit, and an ac-grid connected

24、inverter unit. Experiment results show that there are no circulating current flows among the units. An appropriate amount of the generated</p><p>　　3. MG architecture</p><p>　　In a basic MG arch

25、itecture (Fig. 1), the electrical system is assumed to be radial with several feeders and a collection of loads. The radial system is connected to the distribution system through a separation device, usually a static swi

26、tch, called point of common coupling (PCC). Each feeder has circuit breaker and power flow controller. Developed within the EU R&D MG project, the MG concept adopted in this research involves an operational architect

27、ure (Fig. 2). It comprises an LV network, load</p><p>　　The head of the hierarchical control system is the MGCC. At a second hierarchical control level, load controllers (LC) and micro source controller (MC)

28、 exchange information with the MGCC that manages MG operation by providing set-points to both LC and MC.</p><p>　　The amount of data to be exchanged between network controllers is small, since it includes m

29、ainly messages containing set-points to LC and MC, information requests sent by the MGCC to LC and MC about active and reactive powers, and voltage levels and messages to control MG switches.</p><p>　　Fig. 1

30、. Basic MG architecture.</p><p>　　Fig. 2. MG architecture with MGCC.</p><p>　　3.1. Micro Sources</p><p>　　The MS of special interest for MGs are small (o100kW) units with power elec

31、tronic interfaces. These sources, including micro turbines, wind generators, photovoltaic arrays, PV panels and fuel cells, are placed at customers sites. They are low cost, low voltage andhave high reliable with few emi

32、ssion.</p><p>　　Despite this impressive list of benefits, [9] points out that DER penetration have not met expectations. Major drawbacks to increased DER utilization are high cost, the need for custom engine

33、ering, lack of plug and play integration methods and few successful business models. Many private and public organizations are aggressively addressing these drawbacks, including the Department of Energy and state organiz

34、ation.</p><p>　　In [1], some emerging generation technologies are introduced in details. Several MS models, able to describe their dynamic behavior, have been developed in [10]. Also in [11],a simple combina

35、tion control method for different kinds of DER to compensate load demand fluctuation in a MG is proposed.</p><p>　　3.2. Storage devices</p><p>　　The current power systems (can named as Macro Gri

36、d) have storage provided through the generators inertia When a new load comes on line, the initial energy balance is satisfied by the system’s inertia. This results in a slight reduction in system frequency. Lasseter [2]

37、points out that a system with clusters of MS designed to operate in an island mode must provide some form of storage to insure initial energy balance.</p><p>　　Due to the large time constants (from 10 to 200

38、 s) of the responses of some MS, such as fuel-cells and micro turbines, storage devices must be able to provide the amount of power required to balance the system following disturbances and/or significant load changes. T

39、hese devices act as controllable ac voltage sources to face sudden system changes such as in load-following situations. In spite of acting as voltage sources, these devices have physical limitations and thus a finite cap

40、acity for sto</p><p>　　The necessary MG storage can come several forms; batteries or super-capacitors on the dc bus for each MS; direct connection of ac storage devices (batteries, flywheels, etc.); or use o

41、f traditional generation with inertia with the MS.</p><p>　　Venkataramanan and Illindala [12] conducts that a lead–acid battery is considered the most suitable for MG applications. They are capable of provid

42、ing large currents for a very short interval of time.</p><p>　　3.3. Inverter controller</p><p>　　Most MS technologies that can be installed in an MG are not suitable for direct connection to the

43、 electrical network due to the characteristics of the energy produced.Therefore, power electronic interfaces (dc/ac or ac/dc/ac) are required (Fig. 3). Inverter control is thus the main concern in MG operation.</p>

44、<p>　　Pecas Lopes et al. [4] introduces two kinds of control strategies used to operate an inverter. The inverter model is derived according to the following control strategies. PQ inverter control: the inverter i

45、s used to supply a given active and reactive power set point .Voltage source inverter (VSI) control: the inverter is controlled to “feed” the load with predefined values for voltage and frequency.</p><p>　　F

46、ig. 3. Interface inverter system.</p><p>　　In [1], operation of the MG assumes that the power electronic controls of current MS are modified to provide a set of key functions. The critical system performance

47、 components are the voltage versus reactive power droop and power versus frequency droop.</p><p>　　Voltage vs. reactive power (Q) droop</p><p>　　Voltage regulation is necessary for local reliabi

48、lity and stability. Without local voltage control, systems with high penetrations of MS could experience voltage and/or reactive power oscillations. With small errors in voltage set points, the circulating current can ex

49、ceed the ratings of the MS. This situation requires a voltage vs. reactive power droop controller so that, as the reactive power generated by the MS becomes more capacitive, the local voltage set point is reduced. Conver

50、sely, as Q </p><p>　　Power vs. frequency droop</p><p>　　In island mode, problems from slight errors in frequency generation at each inverter and the need to change power-operating points to matc

51、h load changes need be addressed. Power vs. frequency droop functions at each MS can effectively solve these problems without a communication network. When the MG separates from the grid, the voltage phase angle at each

52、MS has a change, resulting in an apparent reduction in local frequency. This frequency reduction coupled with a power increase allows for each</p><p>　　proportional share of power.</p><p>　　Li e

53、t al. [13] presents the design and analysis of a controller for multi-bus MG system.The controller proposed for use with each distributed generation (DG) system in the MG contains inner voltage and current loops for regu

54、lating the three-phase grid-interfacing inverter, and external power control loops for controlling real and reactive power flow and for facilitating power sharing between the paralleled DG systems when a utility fault oc

55、curs and the MG islands.</p><p>　　Li et al. [14] proposes a grid-interfacing power quality compensator using two inverters(inverters A and B) to control both the sensitive lead voltages in the MG and the lin

56、e currents flowing between the MG and utility system. The main functions of shunt inverter A are to maintain a balanced set of sensitive load voltages in the MG under all grid and load operating conditions, while the mai

57、n functions of series inverter B are to inject</p><p>　　appropriate voltage components along the distribution feeder to balance the line currents and to limit the flow of large fault currents during utility

58、voltage sags.</p><p>　　4. Emergency operation, fault detection, and safety analysis of MG</p><p>　　MG flexibility can be achieved by allowing its operation under two different conditions.One is

59、normal interconnected mode, in which the MG is connected to a main MV grid being either partially supplied from it or injecting some amount of power into it. The other is emergency mode, in which the MG operates autonomo

60、usly (as in physical islands) when the disconnection from the upstream MV network occurs. The MG islanding process may result from an intentional disconnection from the MV grid (due to </p><p>　　4.1. Two app

61、roaches in emergency operation of MG</p><p>　　Pes Lopes et al. [15] describes two approaches to deal with MG islanded operation. In the first approach, the main concern is related to inverter control modes.

62、As the MG is an inverter-dominated grid, frequency and voltage control during islanded operation is performed through inverters. The other approach closely follows concepts related to conventional synchronous machine con

63、trol.</p><p>　　A. MG operation regarding inverters control modes</p><p>　　If a cluster of MS is operated within a MG and the main power supply (the MV network) is available, all the inverters ca

64、n be operated in PQ mode, because there are voltage and frequency references. However, a VSI can be used to provide a reference for frequency and it will be possible to operate the MG in islanded mode and to</p>&

65、lt;p>　　smoothly move to islanded operation without changing the control mode of any inverter. The combination of primary frequency regulation provided by storage devices, load-shedding schemes for less important loads

66、 and secondary load frequency control are the key for successful MG islanded operation. More details and specific information can be obtained from [12]. It gives the details of inverter internal control and relative simu

67、lations.</p><p>　　B. MG operation regarding primary energy source control</p><p>　　In this representation, the MS and storage device can be represented by synchronous generators or by STATCOM ba

68、ttery energy storage (STATCOM-BES). In grid connected mode, the frequency of the MG is maintained within a tight range. However, following a disturbance, the frequency of the MG may change rapidly due to the low inertia

69、present in the MG. The control of the MS and storage devices is very important in order to maintain the frequency of the MG during islanded operation (see [4,12]).With d</p><p>　　4.2. Fault detection in MG&l

70、t;/p><p>　　When the MG is operating as a self-contained power island, any fault current will have to be supplied by those generators still connected to it. These fault currents may have relatively low values. T

71、he difficulty caused by using generation that relies on converters is that these units are designed to limit their output current to protect their power devices. Typically this limit is set to about twice their rated out

72、put current (see [2,16]). This is insufficient to trip conventional over-current </p><p>　　Lasseter [2] concludes that the unique nature of the MG design and operation requires a fresh look into the fundamen

73、tals of relaying. One approach that is quite powerful is to develop a real-time fault location technique that will identify the exact location of the fault much more accurately that the classical relaying is capable of d

74、oing under any circumstances. These methods may prove too costly. Low cost approach such a current transformer (CT) based zero sequence detection, and differential </p><p>　　Hernandez-Gonzalez and Iravani [1

75、6] presents an active islanding detection technique for a DR unit at the distribution voltage level, which uses a three-phase, voltage-sourced converter (VSC) as the interface unit. The proposed method is based on inject

76、ing a disturbance signal into the system through either the direct axis (d-axis) or the quadrate axis (q-axis) current controllers of the interface voltage-sourced converter. Signal injection through the d-axis controlle

77、r modulates the amplitude o</p><p>　　AI-Nasseri et al. [17] introduces a new type of protection scheme which is able to protect against faults that are both internal and external to a set zone of protection

78、scheme, based on the abc-dq transformation for the voltage waveforms is able to identify the presence of a short circuit fault and to facilitate discrimination between faults which are either inside or outside a set zone

79、 of the MG.</p><p>　　Mahinda Vilathgamuwa et al. [18] presents the resistance–inductance (RL) feedforward and flux-charge model feedback algorithms for protecting utility-interfaced MG from large line curren

80、ts during utility-voltage sags. The RL algorithm functions by controlling a series inverter, connected between the micro and utility grids, to insert large virtual RL impedance along the distribution feeder to limit the

81、line currents and damp transient</p><p>　　oscillations with a finite amount of active power circulating through the series (and shunt) inverter.</p><p>　　4.3. Safely analysis of MG</p>&l

82、t;p>　　A fault in a MG may generate substantial ground potential rise, even if the energy sources operate at LV. Thus grounding of the distributed energy sources and the transformer connecting the MG to the utility net

83、work must be carefully analyzed and appropriate rules need to be developed.</p><p>　　LV earthing systems are defined according to the earthing techniques of the secondary of the MV/LV transformer (supply sou

84、rce) and the frame of the load equipment. LV neutral earthing is broadly categorized in to three types: TT, IT and TN (see [19]). The TN-C-S is the first choice for MG earthing and the second choice would be TT. Besides,

85、 a grounding system for a typical MG has been designed in [19] and its adequacy during fault conditions studied from an electrical safety point of view. The s</p><p>　　step voltage has been adopted.</p>

86、;<p>　　In [20], a method of small-signal stability analysis of power systems with MG is proposed. The small-signal stability of the system can be evaluated by computing the eigenvalues of the dynamic equations aro

87、und the operating steady state point.</p><p>　　5. MG using a multi-agent system (MAS)</p><p>　　The use of MAS technology can solve a number of specific operational problems. First of all, small

88、DER units have different owners, and several decisions should be taken locally so centralized control is difficult. Furthermore MGs operate in a liberalized market; therefore the decisions of the controller of each unit

89、concerning the market should have a certain degree of “intelligence”. Finally the local DER units besides selling power to the network have also other task: producing heat for local</p><p>　　locally at a cer

90、tain level or providing a backup system for local critical loads in case of a failure of the main system (see [21–23]). These tasks suggest the importance of the distributed control and autonomous operation.</p>&

91、lt;p>　　Dimeas and Hatziargyriou [21] describes four kinds of agents: production agent,consumption agent, power system agent and MGCC agent. The MGCC agent has only coordinating tasks and more specifically it announces

92、 the beginning and the end of a negotiation for a specific period and records final power exchanges between the agents in every period. In the market environment, three control levels are distinguished.</p><p&

93、gt;　　_ distribution network operator (DNO) and market operator (MO) at the level of the MV;</p><p><b>　　_ MGCC;</b></p><p>　　_ local controllers (LC), which could be either micro sou

94、rce controllers or load controllers.</p><p>　　The main interface between the DNS/MO and the MG is the MGCC. The MGCC is the main responsible for the optimization of the MG operation, or alternatively, it sim

95、ply coordinates the LC, which assume the main responsibility for this optimization. Ref. [22]describes the main functions required by the MGCC for the efficient MG participation in future real-time markets following diff

96、erent policies.</p><p>　　6. Conclusion</p><p>　　This paper makes a conclusion on the works and researches that make efforts on DER and MG. It introduces the current situations about MG and MG ar

97、chitecture. Furthermore, the operation in a MG is described in details. At last, the MG in market environment is also concluded in the paper.</p><p>　　MG is a new type of power system. The technique is still

98、 not mature nowadays. A lot of works have to be done until it can be put in the market. Japan and some Europe organization have put some efforts into it, although it is still under the research and experimental stage.<