家用光伏离网系统设计

太阳能供电系统中的主要部分，也是太阳能供电系统中价值最高的部件，光伏组件是将太阳光能直接转变为直流电能的阳光发电装置。根据用户对功率和电压的不同要求，数个光伏组件经过串联（以满足电压要求）和并联（以满足电流要求），形成供电阵列提供更大的电功率。太阳电池的发电量随着日照强度的增加按比例增加。随着组件表面的温度升高而略有下降。随着温度的变化，电池组件的电流、电压、功率也将发生变化，组件串联设计时必须考虑电压负温度系数。

光伏组件有单晶硅组件、多晶硅组件、薄膜组件三种，目前单晶组件占据主流，效率较高，相同面积采用单晶组件总功率较大，但如果是相同功率，三种组件的发电量相差不多。三种组件各有其优缺点，可根据项目的特点选择，单晶效率高，但单价也高，可用于安装面积有限的场合，多晶效率稍低，但价格稍便宜，可用于经费有限的场合，薄膜组件形式多样，有柔情的、透光的，彩色的等多种，可用于BIPV等场合。

主要功能分为两部分，太阳能控制器和逆变器，其作用是对太阳能电池组件所发的电能进行调节和控制，最大限度地对蓄电池进行充电，并对蓄电池起到过充电保护、过放电保护的作用，同时把组件和蓄电池的直流电逆变成交流电，给交流负载使用。

控制器的作用是把光伏组件发出来的电，经过追踪和变换，存于蓄电池之中，除此之外，还有保护蓄电池，防止蓄电池过充过放等功能。控制器常用于离网系统、直流耦合的储能系统中。控制器输出是电流电，也可以单独给直流负载使用。

离网逆变器形式多样化，按输出波形分为修正波逆变器和正弦波逆变器；按电气隔离方式又分为高频正弦波逆变器和工频正弦波逆变器；把控制器和逆变器分开设计，各自单独接线，叫分体式，把控制器和逆变器合在一起，叫一体机，也叫逆控制一体机。

▲离网逆变器系列

其主要任务是储能，以便在没有光伏时间段保证负载用电。蓄电池是离网系统中的一个重要组成部分，它的优劣直接关系到整个系统的可靠程度，然而蓄电池却又是整个系统中平均无故障时间（MTBF）最短的一种器件。如果用户能够正常使用和维护，就能够延长其使用寿命，反之其使用寿命会显著缩短，目前光伏储能系统通常的蓄电池都是电化学储能，它是利用化学元素做储能介质，充放电过程伴随储能介质的化学反应或者变化。主要包括铅酸电池、液流电池、钠硫电池、锂离子电池等，目前应用以锂电池和铅蓄电池为主等，

Photovoltaic module

The main part of the solar power supply system is also the most valuable component of the solar power supply system. Photovoltaic modules are solar power generation devices that convert solar energy directly into direct current power. According to users' different requirements on power and voltage, several PV modules are connected in series (to meet voltage requirements) and in parallel (to meet current requirements) to form a power supply array to provide greater power. The amount of electricity produced by solar cells increases proportionally with the increase in sunlight intensity. It decreases slightly as the temperature of the component surface increases. With the change of temperature, the current, voltage and power of the battery module will also change. The negative voltage temperature coefficient must be considered when the module is designed in series.

There are three types of photovoltaic modules: monocrystal silicon module, polycrystalline silicon module and thin film module. At present, single crystal module occupies the mainstream with high efficiency. The total power of single crystal module is larger in the same area, but if it is the same power, the power generation of the three modules is similar. Each of the three components has its advantages and disadvantages, can be selected according to the characteristics of the project, single crystal efficiency is high, but the unit price is high, can be used for the installation area is limited occasions, polycrystal efficiency is a little lower, but the price is a little cheaper, can be used for the occasion of limited funds, thin film components in various forms, soft, transparent, color, etc., can be used for BIPV and other occasions.

02

Solar controller and inverter

The main function is divided into two parts, the solar controller and the inverter, its role is to adjust and control the solar cell module generated by the electric energy, the maximum charge of the battery, and the battery to play the role of over charge protection, over discharge protection, at the same time, the DC inverter module and battery into alternating current, to the AC load.

The role of the controller is to put the electricity emitted by the photovoltaic module, after tracking and transforming, stored in the battery. In addition, there are functions of protecting the battery, preventing the battery from overcharging and overdischarging. Controllers are often used in off-grid systems and DC coupled energy storage systems. The output of the controller is current, or can be used solely for DC loads.

Off-grid inverter forms are diversified, according to the output waveform can be divided into modified wave inverter and sine wave inverter; According to the electrical isolation mode is divided into high frequency sine wave inverter and power frequency sine wave inverter; The controller and inverter are designed separately and connected separately, which is called split type. The controller and inverter are combined together, which is called all-in-one machine, also called inverse control all-in-one machine.

The picture

▲ Off-grid inverter series

03

Storage battery bank

Its main task is to store energy in order to ensure the load of electricity in the absence of photovoltaic time. The battery is an important part of the off-grid system, its merits and disadvantages are directly related to the reliability of the whole system, but the battery is the whole system in the mean time to failure (MTBF) of a device shortest. If the user can use and maintain normally, its service life can be extended, on the contrary, its service life will be significantly shortened. At present, the usual battery of photovoltaic energy storage system is electrochemical energy storage, which uses chemical elements as the energy storage medium, and the charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. It mainly includes lead-acid battery, flow battery, sodium-sulfur battery, lithium-ion battery, etc. At present, lithium battery and lead battery are mainly used.