分布式光伏发电遵循因地制宜、清洁高效、分散布局和就近利用的原则，充分利用当地太阳能资源替  代和减少化石能源消费。分布式光伏发电一般是利  用企业既有建筑的屋顶资源，运行方式以用户侧自发  自用为主、多余电量上网。分布式光伏系统由光伏组  件、逆变器组成。逆变器跟踪光伏电池大功率点、 控制并网电流的波形和功率，将光伏电池所发出的电  能逆变成正弦电流并入电网中，使向电网传送的功率与光伏阵列所发的大功率电能相平衡。光伏并网系统的传输能量来源于光伏电池，由电池的特性决定其输出的电压和电流曲线为非线性，受光照和温度的影响，输出功率跟随变化。光伏系统通过电力电子变换器将直流电变换为交流电并入电网。
1   分布式光伏并网后对电网功率因数的影响
1.1  功率因数：功率因数是供电公司衡量用户电气设备效率 高低的一个系数，功率因数过低会降低电网的运行 效率 。功率因数的计算通过用户有功电量和无功 电量的数值取得，一般而言，无功电量比例越高则 功率因数越低，所以，提高功率因数的一个重要手 段就是加装无功补偿装置，以降低无功功率。
1.2  力调电费：为提高电能使用效率，原水利电力部、[敏感词]物价 局于 1983 年出台了《功率因数调整电费办法》(水电 财字215 号文件)，办法规定容量在100 kVA 及以上 的电力用户均须进行功率因数考核，未达到考核标 准将加收功率因数调节费(即力调电费)，超过考核标 准的按超过比例进行奖励。用户功率因数考核标准 为 0.85 或 0.90，若功率因数远低于标准，不仅会造 成电网运行负担 ，同时力调罚款数量也会十分巨 大。由于用户负荷与负荷性质在每天的不同时段不 一定一致，用户一般会加装带有自动投切功能的无 功补偿(多为电容性设备)装置，自动调整补偿力度。关于无功电能四象限测量的定义在《多功能电 能表通信协议》（DL/T645-2007）中做出了规定。
电能表的正 、反向与电能的受（送）相关，一般 情况用户接受系统的电能定义为正向；用户内部发 电向系统送电定义为反向。
( 1) 当系统向用户输送有功和无功时，电能表 工作在第 I 象限，电能表显示有功是正值，无功也是 正值；这是用户的正常用电模式，即有功电能和无 功电能全部来自电网；
(2) 当系统向用户输送无功，用户向系统反送有 功时，电能表工作在第Ⅱ象限，电能表显示有功是负 值（反向有功），无功是正值；这时用户负荷无法全部 消纳分布式光伏发电，余电上网的情况，有功电能倒 送回电网，而负载所需无功仍然来自电网；
(3) 当用户向系统反送有功和无功时，电能表 工作在第Ⅲ象限，电能表显示有功是负值，无功也 是负值；有些自发电的用户在内部没有负荷时，出 现和专业电厂一样，有功和无功全部向网上输送；
(4) 当系统向用户输送有功，用户向系统反送 无功时，电能表工作在第Ⅳ象限，电能表显示有功 是正值，无功是负值；这时用户从系统取有功，但用 户的电容补偿处于过补偿状态，向系统反送无功。；
《功率因数调整电费办法》中规定用户功率因 数的计算公式为：
                                  
式中容性无功 Qc 和感性无功 QL 的方向相反， 关口表在计算功率因数时采用正反向无功的[敏感词]  值相加 。而有功只取正向有功电能，反向有功电能  是不参与功率因数计算的 。 即当用户分布式光伏  向电网倒送有功时（电能表工作在第 II 或第 III 象  限），关口表的功率因数会降低。
供电电网功率因数降低的影响及后果
1）电力系统和用电企业的设备不能被充分利用。因为电力系统内的发电机和变压器等设备，在正常情况下，不允许长期超过额定电压和额定电流运行。所以当电压和电流都已达到额定值时，功率因数低便造成设备有功功率的输出较少。同样容量的设备，功率因数越低，其输出的有功功率就越少。
2）引起电力系统电能损耗增大和供电质量降低。对输电和配电线路来说，线路中的损耗与电流大小的平方成正比，当输送同样大小的有功功率P＝IUcosφ时，功率因数cosφ越低，输电线路中的电流I＝P／Ucos φ就越大，而线路的电能损耗是与电流的平方成正比增加的。
3）功率因数降低，线路电流增大时，势必造成线路中电压降增大，这将导致线路末端的电压降低。若要满足末端用户电压要求，则线路始端的电压就要升高，从而会使整个线路的供电质量降低。 
4）功率因数降低增加用电电费支出，根据[敏感词]水利电力两部要求，工业用户的供电功率因数反馈电网的cosφ不能低于0.90。凡达不到标准要求的企业用户，电业部门将根据《力率调整电费办法》对企业用户进行一定比例电费力率罚款。


 

Distributed photovoltaic power generation follows the principles of adapting to local conditions, clean and efficient, decentralized layout, and nearby utilization, fully utilizing local solar energy resources to replace and reduce fossil energy consumption. Distributed photovoltaic power generation generally utilizes the roof resources of existing buildings in enterprises, and operates mainly on the user side for self use, with excess electricity connected to the grid. A distributed photovoltaic system consists of photovoltaic modules and inverters. The inverter tracks the high-power point of the photovoltaic cell, controls the waveform and power of the grid connected current, inverts the electrical energy generated by the photovoltaic cell into a sine current and integrates it into the grid, so that the power transmitted to the grid is balanced with the high-power electrical energy generated by the photovoltaic array. The transmission energy of photovoltaic grid connected systems comes from photovoltaic cells, and the output voltage and current curves are determined by the characteristics of the cells to be nonlinear. The output power follows the changes due to the influence of light and temperature. Photovoltaic systems convert direct current into alternating current through power electronic converters and integrate it into the power grid.
1   The impact of distributed photovoltaic grid connection on power factor of the power grid
1.1 Power factor: Power factor is a coefficient used by power supply companies to measure the efficiency of users' electrical equipment. A low power factor can reduce the operational efficiency of the power grid. The calculation of power factor is obtained by the numerical values of active and reactive power of the user. Generally speaking, the higher the proportion of reactive power, the lower the power factor. Therefore, an important means to improve the power factor is to install reactive power compensation devices to reduce reactive power.
1.2 Power factor adjustment electricity fee: In order to improve the efficiency of electricity use, the former Ministry of Water Resources and Electric Power and the National Price Bureau issued the "Power Factor Adjustment Electricity Fee Method" (Water and Electricity Finance Document No. 215) in 1983. The method stipulates that power users with a capacity of 100 kVA or above must undergo power factor assessment. If they fail to meet the assessment standards, a power factor adjustment fee (i.e. power factor adjustment electricity fee) will be charged. Those who exceed the assessment standards will be rewarded proportionally. The assessment standard for user power factor is 0.85 or 0.90. If the power factor is much lower than the standard, it will not only cause a burden on the operation of the power grid, but also result in a huge amount of fines for power regulation. Due to the fact that user load and load nature may not be consistent at different times of the day, users generally install reactive power compensation devices (mostly capacitive devices) with automatic switching functions to automatically adjust the compensation intensity. The definition of reactive energy four quadrant measurement is specified in the "Multi functional Energy Meter Communication Protocol" (DL/T645-2007).
The forward and reverse directions of an electric energy meter are related to the reception (transmission) of electrical energy. Generally, the user's acceptance of the system's electrical energy is defined as positive; Internal power generation by users to supply power to the system is defined as reverse.
When the system delivers active and reactive power to the user, the energy meter operates in quadrant I and displays positive values for active and reactive power; This is the normal electricity consumption mode of the user, where both active and reactive energy come from the power grid;
(2) When the system delivers reactive power to the user and the user sends active power back to the system, the energy meter operates in quadrant II and displays negative active power (reverse active power) and positive reactive power; At this point, the user load cannot fully absorb the distributed photovoltaic power generation. In the case of surplus electricity being connected to the grid, active energy is sent back to the grid, while the reactive power required by the load still comes from the grid;
(3) When the user sends active and reactive power back to the system, the energy meter operates in quadrant III and displays negative values for active and reactive power; Some self generating users, like professional power plants, transmit both active and reactive power to the grid when there is no internal load;
(4) When the system delivers active power to the user and the user sends reactive power back to the system, the energy meter operates in quadrant IV and displays positive active power and negative reactive power; At this point, the user retrieves active power from the system, but the user's capacitor compensation is in an overcompensation state and sends reactive power back to the system.;
The calculation formula for user power factor as stipulated in the "Electricity Fee Method for Power Factor Adjustment" is:
                                  
In the formula, the directions of capacitive reactive power Qc and inductive reactive power QL are opposite, and the gateway meter calculates the power factor by adding the absolute values of forward and reverse reactive power. And active power only takes forward active energy, and reverse active energy does not participate in power factor calculation. When users transfer active power from distributed photovoltaics to the grid (with the energy meter operating in quadrant II or III), the power factor of the gateway meter will decrease.
The impact and consequences of power factor reduction in power supply grid
1) The equipment of the power system and electricity consuming enterprises cannot be fully utilized. Because equipment such as generators and transformers in the power system are not allowed to operate beyond their rated voltage and current for a long time under normal circumstances. So when both voltage and current have reached their rated values, a low power factor results in less active power output from the equipment. The lower the power factor of a device with the same capacity, the less active power it outputs.
2) Causing an increase in energy loss and a decrease in power supply quality in the power system. For transmission and distribution lines, the loss in the line is proportional to the square of the current. When transmitting the same amount of active power P=IUcos φ, the lower the power factor cos φ, the larger the current I=P/Ucos φ in the transmission line. The energy loss in the line increases proportionally to the square of the current.
3) When the power factor decreases and the line current increases, it will inevitably cause an increase in voltage drop in the line, which will lead to a decrease in voltage at the end of the line. To meet the voltage requirements of end users, the voltage at the beginning of the line needs to increase, which will reduce the power supply quality of the entire line.
4) The decrease in power factor increases the cost of electricity consumption. According to the requirements of the Ministry of Water Resources and Electric Power, the cos φ of the power factor feedback grid for industrial users cannot be lower than 0.90. For enterprise users who fail to meet the standard requirements, the power department will impose a certain proportion of electricity consumption rate fines on enterprise users in accordance with the "Measures for Adjusting Electricity Charges with Power Rates".