太阳能光伏系统的组成和原理

太阳能光伏系统由以下三部分组成：太阳电池组件;充、放电控制器、逆变器、测试仪表和电脑监控等电力电子设备和蓄电池或其他蓄能和辅助发电设备。

太阳能光伏系统具有以下的特点：

没有转动部件，不产生噪音;

没有空气污染、不排放废水;

没有燃烧过程，不需要燃料;

维修保养简单，维护费用低;

运行可靠性、稳定性好;

作为关键部件的太阳电池使用寿命长，晶体硅太阳电池寿命可达到25年以上;根据需要很容易扩大发电规模。

光伏系统应用非常广泛，光伏系统应用的基本形式可分为两大类：独立发电系统和并网发电系统。应用主要领域主要在太空航空器、通信系统、微波中继站、电视差转台、光伏水泵和无电缺电地区户用供电。随着技术发展和世界经济可持续发展的需要，发达国家已经开始有计划地推广城市光伏并网发电，主要是建设户用屋顶光伏发电系统和MW级集中型大型并网发电系统等，同时在交通工具和城市照明等方面大力推广太阳能光伏系统的应用。

光伏系统的规模和应用形式各异，如系统规模跨度很大，小到0.3～2W的太阳能庭院灯，大到MW级的太阳能光伏电站，如3.75kWp家用型屋顶发电设备、敦煌10MW专案。其应用形式也多种多样，在家用、交通、通信、空间应用等诸多领域都能得到广泛的应用。尽管光伏系统规模大小不一，但其组成结构和工作原理基本相同。图4-1是一个典型的供应直流负载的光伏系统示意图。其中包含了光伏系统中的几个主要部件：

光伏组件方阵：由太阳电池元件(也称光伏电池组件)按照系统需求串、并联而成，在太阳光照射下将太阳能转换成电能输出，它是太阳能光伏系统的核心部件。

蓄电池：将太阳电池元件产生的电能储存起来，当光照不足或晚上、或者负载需求大于太阳电池元件所发的电量时，将储存的电能释放以满足负载的能量需求，它是太阳能光伏系统的储能部件。目前太阳能光伏系统常用的是铅酸蓄电池，对于较高要求的系统，通常采用深放电阀控式密封铅酸蓄电池、深放电吸液式铅酸蓄电池等。

控制器：它对蓄电池的充、放电条件加以规定和控制，并按照负载的电源需求控制太阳电池元件和蓄电池对负载的电能输出，是整个系统的核心控制部分。随着太阳能光伏产业的发展，控制器的功能越来越强大，有将传统的控制部分、逆变器以及监测系统集成的趋势，如AES公司的SPP和SMD系列的控制器就集成了上述三种功能。

光伏逆变器：在太阳能光伏供电系统中，如果含有交流负载，那么就要使用逆变器设备，将太阳电池元件产生的直流电或者蓄电池释放的直流电转化为负载需要的交流电。

太阳能光伏供电系统的基本工作原理就是在太阳光的照射下，将太阳电池元件产生的电能通过控制器的控制给蓄电池充电或者在满足负载需求的情况下直接给负载供电，如果日照不足或者在夜间则由蓄电池在控制器的控制下给直流负载供电，对于含有交流负载的光伏系统而言，还需要增加逆变器将直流电转换成交流电。光伏系统的应用具有多种形式，但是其基本原理大同小异。对于其他类型的光伏系统只是在控制机理和系统部件上根据实际的需要有所不同，下面将对不同类型的光伏系统进行详细地描述。

光伏系统的分类与介绍

一般将光伏系统分为独立系统、并网系统和混合系统。如果根据光伏系统的应用形式、应用规模和负载的类型，对光伏供电系统进行比较细致的划分，可将光伏系统分为如下六种类型：小型太阳能供电系统(SmallDC);简单直流系统(SimpleDC);大型太阳能供电系统(LargeDC);交流、直流供电系统(AC/DC);并网系统(UtilityGridConnect);混合供电系统(Hybrid);并网混合系统。

光伏发电是利用半导体介面的光生伏特效应而将光能直接转变为电能的一种电子元件技术，这种技术的关键元件是太阳能电池。太阳能电池经过串联后进行封装保护可形成大面积的太阳电池元件，再配合上功率控制器等部件就形成了光伏发电装置。光伏发电的优点是较少受地域限制，因为阳光普照大地;光伏系统还具有安全可靠、无杂讯、低污染、无需消耗燃料和架设输电线路即可就地发电供电及建设同期短的优点。

光伏发电是根据光生伏特效应原理,利用太阳能电池将太阳光能直接转化为电能。不论是独立使用还是并网发电,光伏发电系统主要由太阳能电池板(元件)、控制器和逆变器三大部分组成，它们主要由电子元器件构成，不涉及机械部件,所以,光伏发电设备极为精炼,可靠稳定寿命长、安装维护简便。理论上讲,光伏发电技术可以用于任何需要电源的场合,上至航天器,下至家用电源,大到兆瓦级电站,小到玩具,光伏电源无处不在。太阳能光伏发电的最基本元件是太阳能电池(片)，有单晶硅、多晶硅、非晶硅和薄膜电池等。目前，单晶和多晶电池用量最大，非晶电池用于一些小系统和计算器辅助电源等。

Composition and principle of solar photovoltaic system
The solar photovoltaic system consists of the following three parts: solar cell module; Charge and discharge controllers, inverters, test instruments, computer monitoring and other power electronic equipment and batteries or other energy storage and auxiliary power generation equipment.
The solar photovoltaic system has the following characteristics:
No rotating parts, no noise;
No air pollution, no waste water discharge;
No combustion process, no fuel required;
Simple maintenance and low maintenance cost;
Good operation reliability and stability;
As a key component, the solar cell has a long service life, and the service life of crystalline silicon solar cell can reach more than 25 years; It is easy to expand the scale of power generation as required.
Composition, principle and characteristics of solar photovoltaic power generation
Photovoltaic systems are widely used. The basic forms of photovoltaic system applications can be divided into two categories: independent power generation systems and grid connected power generation systems. The main application fields are mainly in space aircraft, communication system, microwave relay station, TV turntable, photovoltaic water pump and household power supply in areas without electricity and power shortage. With the development of technology and the sustainable development of the world economy, developed countries have begun to promote urban photovoltaic grid connected power generation in a planned way, mainly building household roof photovoltaic power generation systems and MW level centralized large-scale grid connected power generation systems, and vigorously promoting the application of solar photovoltaic systems in transportation and urban lighting.
The scale and application forms of photovoltaic systems vary. For example, the scale span of the system is very large, ranging from 0.3 ~ 2W solar garden lamps to MW solar photovoltaic power plants, such as 3.75kwp household roof power generation equipment and Dunhuang 10MW project. Its application forms are also diverse, and it can be widely used in many fields, such as household, transportation, communication, space applications and so on. Although the scale of photovoltaic system varies, its composition structure and working principle are basically the same. Figure 4-1 is a schematic diagram of a typical photovoltaic system supplying DC load. It includes several main components in the photovoltaic system:
Photovoltaic module array: it is composed of solar cell elements (also known as photovoltaic cell modules) in series and parallel according to the system requirements. It converts solar energy into electric energy output under the sunlight. It is the core component of the solar photovoltaic system.
Storage battery: it stores the electric energy generated by the solar cell element. When the light is insufficient or at night, or the load demand is greater than the electric energy generated by the solar cell element, it releases the stored electric energy to meet the energy demand of the load. It is the energy storage component of the solar photovoltaic system. At present, lead-acid batteries are commonly used in solar photovoltaic systems. For systems with high requirements, deep discharge valve regulated sealed lead-acid batteries and deep discharge liquid absorption lead-acid batteries are usually used.
Controller: it regulates and controls the charging and discharging conditions of the battery, and controls the solar cell elements and the electric energy output of the battery to the load according to the power demand of the load. It is the core control part of the whole system. With the development of the solar photovoltaic industry, the functions of the controller are becoming more and more powerful. There is a trend to integrate the traditional control part, inverter and monitoring system. For example, the spp and SMD series controllers of AES company integrate the above three functions.
Photovoltaic inverter: in the solar photovoltaic power supply system, if there is an AC load, the inverter equipment shall be used to convert the DC generated by the solar cell elements or the DC released by the battery into the AC required by the load.
The basic working principle of the solar photovoltaic power supply system is to charge the battery through the control of the controller or directly supply power to the load when the load demand is met under the illumination of the sun. If the sunlight is insufficient or at night, the battery will supply power to the DC load under the control of the controller. For the photovoltaic system with AC load, It is also necessary to add an inverter to convert DC into AC. The application of photovoltaic system has many forms, but its basic principles are similar. For other types of photovoltaic systems, the control mechanism and system components are different according to actual needs. The following will describe different types of photovoltaic systems in detail.
Composition, principle and characteristics of solar photovoltaic power generation
Classification and introduction of photovoltaic system
Generally, photovoltaic system is divided into independent system, grid connected system and hybrid system. If the photovoltaic power supply system is carefully divided according to the application form, application scale and load type of the photovoltaic system, the photovoltaic system can be divided into the following six types: small solar power supply system (smalldc); Simple DC system (simpledc); Large solar power supply system (largedc); AC and DC power supply system (ac/dc); Utility grid connect; Hybrid power supply system; Grid connected hybrid system.
Photovoltaic power generation is an electronic component technology that directly converts light energy into electrical energy by using the photovoltaic effect at the semiconductor interface. The key component of this technology is the solar cell. After the solar cells are connected in series, they can be packaged and protected to form a large area of solar cell elements, and then combined with power controllers and other components to form a photovoltaic power generation device. The advantage of photovoltaic power generation is that it is less restricted by region, because the sun shines on the earth; The photovoltaic system also has the advantages of safety and reliability, no noise, low pollution, local power generation and power supply without fuel consumption and power transmission lines, and short construction period.
Photovoltaic power generation is based on the principle of photovoltaic effect, using solar cells to directly convert solar energy into electric energy. Whether it is used independently or connected to the grid for power generation, the photovoltaic power generation system is mainly composed of solar panels (components), controllers and inverters, which are mainly composed of electronic components and do not involve mechanical parts. Therefore, the photovoltaic power generation equipment is extremely refined, reliable, stable, long service life and easy to install and maintain. Theoretically, photovoltaic power generation technology can be used in any situation that requires power, from spacecraft to household power, from megawatt power stations to toys. Photovoltaic power is everywhere. The most basic components of solar photovoltaic power generation are solar cells (chips), including monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film cells. At present, single crystal and polycrystalline batteries are the most widely used. Amorphous batteries are used in some small systems and auxiliary power supplies for calculators.