分布式太阳能光伏离网系统设计步骤

分布式光伏离网发电系统主要由光伏组件、支架、控制器、逆变器、蓄电池以及配电系统组成，主要用于无电或者缺电地区，以解决生活基本需求为主。光伏离网系统没有标准的方案，但离网设备有很多种类，可以组合成不同的方案，适应不同的用户需求。

▲离网发电系统示意图

前期调研

离网系统设计之前，前期工作需做好。一是统计用户的用电负载的类型和功率的总和，像空调、洗风机、水泵、冰箱等电器，里面有电动机，是感性负载，启动功率大，电灯、电视、电磁炉、电脑等电器，是阻性负载；二是统计每天的平均用电量，高峰用电量，白天和晚上的用电量等；三是先了解用户安装地点的气候条件，平均峰值日照小时数据，一年中连续阴雨天数量等等；四是了解有没有市电，或者燃油发电机；五是了解清楚用户的预算和经济情况，对用电的紧急程度。了解这些情况后，就可对症下药，开始设计方案。

方案设计

离网系统的设计，主就是根据前期调研的数据，去确认系统逆变器、组件和蓄电的容量，这个设计方法和并网系统完全不同，不可照搬。这3个设备设计选型的依据各不相同，但相互之间也需互相配合。

离网逆变器的功率要根据用户的负载类型和功率来确认。逆变器的输出功率要大于实际负载的启动功率。洗衣机、空调、冰箱、水泵、抽油烟机等带有电动机的负载是感性负载，电动机启动功率是额定功率的5-7倍，在计算逆变器的功率时，要把这些负载的启动功率考虑进去。预算较高，对用电要求较高的用户，输出功率是按所有的负载功率之和来计算；预算不高的用户，考虑到所有的负载不可能同时开启，为了节省初始成本，输出功率可以在负载功率之和乘以0.7-0.9的系数。

组件功率要根据用户每天的用电量来确认。光伏是可再生能源，每天都有，因此组件平均每天的发电量要大于用户每天有用电量。至于大多少，要看当在地天气条件和用户的预算及对用电的需求。一般天气条件有低于和高于平均值的情况，大部分地区冬天的光照都比夏天差，有些地区相差一倍以上。预算较高，对用电要求较高的用户，组件功率设计的基本满足光照最差季节的需要，就是在光照最差的季节蓄电池也能够基本上天天充满电。预算不高的用户，如果按最差情况设计太阳能电池组件的功率，那么在一年中的其他时候发电量就会超过实际所需，造成浪费，这时组件功率按年平均光照即可，还可适当加大蓄电池的设计容量，增加电能储存，使蓄电池处于浅放电状态，弥补光照最差季节发电量的不足。

蓄电池容量根据用户的用电量来确定。在没有光伏时，由蓄电池提供电能给系统负载。对于重要的负载，有足够的预算，要考虑连续阴雨天数，对于一般的负载如太阳能路灯等可根据经验或需要在2～3天内选取，重要的负载如通信、导航、医院救治等则在3～7天内选取，要能在几天内保证系统的正常工作，对于一般贫困家庭而言，主要考虑价格，则不用考虑阴雨天，太阳好的时候多用；太阳不好的时候少用，没有太阳则不用。

设备选型

离网用户的需求是多种多样的，根据用户的要求设计光伏系统。这时候需要灵活处理，不要拘泥于固定的公式。

选择逆变器时，要看使用场合，如果只是简单的照明应用，建议选用PWM控制器和修正波逆变器，可以节省初始成本；如果有空调、洗衣机、水泵等含有电机的感性负载，建议选用MPPT控制器和工频逆变器，带负载能力强。如果是综合性负载，建议选用高频逆变器，兼顾成本和带负载能力。

小型光伏离网电站，投资有限，可以考虑选用铅酸胶体蓄电池；中小型光伏离网电站，投资有限，但又希望寿命长，可以考虑选用铅炭蓄电池；中大型光伏储能电站，有足够的预算，对投资回报要求高，可以考虑选用锂电池。

在有市电补充的地方，也可根据实际情况，选择不同的优先模式。市电电压稳定、价格便宜，但供电时间短的地方，建议选择电网优先用电模式；市电的电价较高，还经常停电的地方，用电要求不是特别高的用户，建议选择电池优先用电模式；市电的电价不是很高，经常停电的地方，对用电要求很高的用户，建议选择光伏优先用电模式。

Distributed off-grid pv system is mainly composed of pv module, bracket, controller, inverter, storage battery and power distribution system. It is mainly used in power-free or power-deficient areas to solve the basic needs of daily life. There is no standard scheme for Pv off-grid system, but there are many kinds of off-grid devices, which can be combined into different schemes to meet different user requirements. Off-grid power generation system schematic diagram, pictures, pre-research, off-grid system design, pre-work needs to be done. One is to count the types of electric load and the sum of the power used by users, such as electric appliances such as air conditioners, washing fans, water pumps, refrigerators, etc. . There are electric motors inside, which are inductive loads, with large starting power, electric lamps, televisions, induction cookers, computers and other electrical appliances, it is resistive load; second, the statistics of daily average electricity consumption, peak electricity consumption, day and night electricity consumption, etc. . Third, the first to understand the weather conditions of the user's installation site, the average peak hours of sunshine data, the number of consecutive cloudy and rainy days in a year, etc. The fourth is to know whether there is electricity, or oil-fired generators; the fifth is to know clearly the user's budget and economic situation, the degree of emergency power. Once you understand these things, you can begin to design the solution to the problem. Picture, scheme design, off-grid system design, the main is based on previous research data, to confirm the system inverter, components and storage capacity, this design method and grid-connected system is completely different, can not be copied. The three equipment design selection based on different, but also need to cooperate with each other. The power of off-grid inverter should be confirmed according to user's load type and power. The output power of the INVERTER is greater than the starting power of the actual load. Washing machine, air conditioning, refrigerator, water pump, exhaust hood with motor load is inductive load, motor starting power is rated power 5-7 times, in the calculation of inverter power, the starting power of these loads has to be taken into account. For users with a high budget and a high demand for electricity, the output power is calculated as the sum of all the loads; for users with a low budget, considering that all the loads can not be turned on at the same time, in order to save the initial cost, the output power can be multiplied by a factor of 0.7-0.9 over the sum of the load power. The power of the component is determined based on the user's Daily consumption of electricity. Photovoltaic is a renewable energy source, available on a daily basis, so the modules generate on average more electricity per day than the user uses. How much depends on the weather conditions on the ground and the user's budget and demand for electricity. General weather conditions are below and above average, with light in most areas being worse in winter than in summer, and in some areas more than double the difference. For users with a high budget and a high demand for electricity, the power design of the modules is basically designed to meet the needs of the worst lighting season, even in the worst lighting season the batteries can be charged almost every day. Low-budget users who design the power of solar panels for the worst-case scenario will generate more power than is actually needed at other times of the year, resulting in waste, when the power of the modules is illuminated on an annual average basis, the design capacity of the battery can be increased properly, and the electric energy can be stored, so that the battery is in the state of shallow discharge to make up for the shortage of power generation in the worst season. The capacity of a battery is determined by the amount of electricity consumed by the user. In the absence of photovoltaic, the battery provides power to the system load. For heavy loads, have an adequate budget, take into account the number of consecutive rainy days, and for general loads such as solar street light can be selected within 2 to 3 days depending on experience or need, important loads such as communications, navigation, and hospital care are selected within 3 to 7 days to ensure the normal operation of the system within a few days. For Poor families, price is the main consideration, but rainy days are not, when the sun is good, use more; when the sun is bad, use less, no sun is not used. Pictures, pictures, equipment selection, off-grid user needs are diverse, according to user requirements design photovoltaic system. At this time need to be flexible, do not stick to a fixed formula. When selecting inverters, it is necessary to look at the situation of use. If it is only a simple lighting application, it is recommended to select a PWM controller and a modified wave inverter, which can save the initial cost, it is suggested that MPPT controller and power frequency inverter should be used, which has strong load capacity. If it is a comprehensive load, it is recommended to choose high-frequency INVERTER, taking into account both cost and load capacity. Photo: Small pv off-grid Power Station, limited investment, you can consider using lead-acid Gel battery; small and medium Pv off-grid power station, limited investment, but hope long life, you can consider using lead-carbon battery; large and medium Pv off-grid power station, with a budget and a high return on investment, consider lithium-ion batteries. In the city electricity supplement place, may also according to the actual situation, the choice different priority pattern. In places where the voltage is stable and the price is cheap, but the time of power supply is short, it is suggested that the preferred mode of power consumption should be the power grid; in places where the price of electricity for the market is high and the power supply is often cut off, the demand for power consumption is not particularly high among users, it is recommended to choose the battery-first mode; the market price is not very high, frequent power outages, on high demand for electricity users, it is recommended to choose photovoltaic-first mode.

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