PV Basic Lexicon and Terms
Module related terms
STC: Standard Test Conditions (Standard Test Conditions), that is, the ambient temperature is 25°C, the air quality is AM1.5, the wind speed is 0m/s, and 1000W/㎡. STC is a test condition, mainly for laboratory use.
NOCT: Rated battery operating temperature (Normal Operating Cell Temperature), refers to when the solar Module or battery is in an open circuit state, and (the surface light intensity of the battery = 800W/㎡, the ambient temperature = 20 ° C, the wind speed = 1m/s) temperature reached. NOCT is a temperature, and the NOCT of normal components is 45°C±2°C.
BIPV: Building Integrated Photovoltaic (Building Integrated Photovoltaic), which combines solar cells with building materials and directly applies them to building envelopes such as roofs and walls. Photovoltaic materials used in photovoltaic buildings are embodied in the form of building materials, so photovoltaic building materials not only undertake the function of power generation, but also play a building function. The application of building photovoltaic integration needs to meet the building safety requirements first, and then generate electricity.
PERC: Emitter passivation and back contact cells. PERC cells account for about 90% of the market and are the most mainstream cell type in the current market.
TOPCON: Tunneling oxide layer passivation contact cell, N-type cell technology, high theoretical efficiency limit, and the process is similar to PECR.
HJT: Heterojunction cells with intrinsic amorphous layers, using different semiconductor materials to form heterogeneous PN junctions, have high theoretical efficiency and fewer processing steps, but the process requirements are extremely high.
IBC: Interdigitated Back Contact Cell.
Module parameters
Pmax: As the voltage V keeps increasing, the output power will continue to rise, but it will drop after a certain point, which corresponds to the maximum power output Pmax, at this time the corresponding voltage Vmp (peak voltage), and the corresponding current Imp ( peak current). The Module power characteristic curve is a quasi-parabola, and the highest point is the working point to be found by the maximum power point tracking of the inverter MPPT.
Voc open circuit voltage: Voc is the voltage value measured in the open circuit state when the positive and negative poles of the Module are not connected to any load. At this time, the current value is "0".
Isc short-circuit current: Isc is the current value measured when the positive and negative terminals of the Module are short-circuited, and the voltage value at this time is "0".
Module efficiency: the efficiency of converting the radiation energy received by a photovoltaic Module per unit time into output power under test conditions.
Operating Temperature: The maximum and minimum temperature range in which the Module will operate.
Power tolerance: the maximum range in which the actual power is higher than the nominal maximum power.
Maximum system voltage: The maximum system voltage allowed by the components under the IEC/UL standard (involving Module insulation, withstand voltage, etc.).
Maximum fuse rated current: Overcurrent protection, this value is greater than the maximum operating point operating current, used to protect components and cables.
Battery arrangement: the number of batteries packaged in series and parallel in the Module (72, 144).
Junction box: The function is to connect and protect solar photovoltaic Module s, connect solar cells with external lines, and conduct current generated by photovoltaic Module s.
Module size: The radiation receiving area of the Module determines the conversion efficiency.
Terminology related to power station and system
Capacity ratio: It is the ratio of the installed capacity of the photovoltaic system to the rated capacity (capacity ratio = installed capacity of the photovoltaic system / rated capacity of the photovoltaic system). Properly increasing the capacity ratio within a certain range can improve the utilization rate of other equipment and dilute Investment cost, lower construction cost and power generation cost, smoother output and improved grid friendliness.
1) Photovoltaic power plants generally set a reasonable capacity ratio through active over-allocation to strike a balance between peak power generation and equipment cost reduction.
2) When increasing the capacity ratio, attention should be paid to the power of the inverter, the number of strings that can be connected, and the over-provisioning capability.
AGC: Automatic Generation Control (Automatic Generation Control), that is, the active power control system, receives the signal of the remote control device, responds to the remote adjustment command issued by the dispatcher, and optimizes the calculation of the overall strategy of the AGC Module to make the operating data meet the dispatching grid connection requirements.
AVC: Automatic Voltage Control (Automatic Voltage Control), that is, reactive voltage regulation, according to the grid voltage curve, quickly responds to dispatching instructions, automatically adjusts control strategies and response times such as reactive power and reactive power compensation devices, and achieves voltage regulation goals and reduces Network loss.
Low Voltage Ride Through technology of photovoltaic power station (Low Voltage Ride Through): It means that when the voltage fluctuation of the grid-connected point of the photovoltaic power station caused by grid failure or disturbance, within a certain range, the photovoltaic power station can operate uninterruptedly connected to the grid.
PCC: Point of Common Coupling, where one or more user loads are connected in the power system.
POC: Point of Coupling (Point of Coupling), usually no other customers are connected to this point.
Collector line: In the distributed inverter and centralized grid-connected photovoltaic power generation system, the electric energy output by each photovoltaic Module string is collected to the inverter through the combiner box, and then collected to the DC and DC of the power generation bus through the output terminal of the inverter. AC transmission lines are called collector lines. The collector line can be sent out by means of overhead, direct burial or bridge laying.
Dedicated line access: Distributed power supply dedicated switchgear (interval) is set at the distributed power supply access point, such as distributed power supply directly connected to the substation, switching station, busbar in the power distribution room, or ring network cabinet.
T connection: There is no dedicated switchgear (interval) at the access point of the distributed power supply, such as the way that the distributed power supply is directly connected to the overhead or cable line. (This method is suitable for less important loads (transformers)).
Combiner box: It can be divided into DC combiner box and AC combiner box.
The DC combiner box is installed between the photovoltaic Module s and the inverter. In the photovoltaic power generation system, it is a wiring device to ensure the orderly connection and confluence function of photovoltaic Module s. The device can ensure that the photovoltaic system is easy to cut off the circuit during maintenance and inspection, and reduces the scope of power failure when the photovoltaic system fails.
The AC combiner box is installed between the AC output side of the inverter and the grid-connected point/load. The output disconnect point of the inverter can improve the safety of the system and protect the safety of the installation and maintenance personnel.
Photovoltaic grid-connected cabinet: it exists in the photovoltaic system as the total outlet of the photovoltaic power station. It is a device that connects the photovoltaic power station and the grid. It can protect and measure the total amount of photovoltaic power generation, facilitate troubleshooting management, and improve the safety and economic benefits of the power generation system. . Possess all-round multiple protection functions such as voltage loss detection and opening, voltage detection and closing, overcurrent protection, overvoltage protection, island protection, anti-backflow protection, harmonic control, reactive power compensation, etc. Parameters and status indicators are widely used in photovoltaic power generation systems, and can be used together with photovoltaic grid-connected inverters to form a complete photovoltaic power generation system solution.
Full hours: Indicates the ratio of the final grid-connected AC power generation of the grid-connected photovoltaic power generation system to the rated power of the photovoltaic system within a period of time, and is used to compare the power generation capacity (kWh/kW) of photovoltaic systems with different installed capacities.
In addition, there is the concept of theoretical full-time hours. The theoretical full-time hours are the ratio of the total radiation of the inclined surface of the photovoltaic array per unit area to the standard irradiance (1000W/㎡) under the standard test conditions of photovoltaic cells, also known as the peak sunshine hours of the square array, which reflects the local radiation According to the level.
Peak hours: is a unit that describes solar radiation and is used to compare solar resources in different regions.
The calculation formula is peak hours H=total radiation on the inclined surface/(1000W/㎡).
Utilization hours of power generation equipment: It is the operating hours of the average power generation equipment capacity in a certain period of time under the condition of full load operation, that is, the ratio of power generation to the average installed capacity, reflecting the utilization rate of power generation equipment in the region.
Utilization hours = power generation / installed capacity, pay attention to the unit.
Annual Utilization Hours: Refers to the sum of the available hours in one year in units of one year. In the 8760h of each year, the proportion of the utilization hours of power generation equipment is also called "equipment utilization".
High, medium and low voltage grid connection of photovoltaic power stations: general industrial and commercial 400kW and below can be connected to low voltage 380V grid, and between 400kW and 2MW can be divided into multiple grid connection points for low voltage grid connection. More than 2MW needs to be connected to 10kV grid, and more than 6MW needs to be connected to 35kV grid Grid connection (specifically refer to the requirements or suggestions of the local power grid company).
AC and DC cables: The power supply is divided into AC and DC, so the cables for transmitting power are also divided into AC cables and DC cables.
AC cables are used to connect AC power cables, and AC cables are often used in industrial frequency (domestic 50HZ) power systems.
DC cables are used as power cables in DC transmission and distribution systems. Except that the electrical characteristics of the DC cable are different from those of the AC cable, its structure is basically the same as that of the AC cable. DC cables are mainly used in long-distance submarine cable lines. (Photovoltaic cables refer to DC cables.)
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