When it comes to the mixed expression of Chinese and English, people tend to be preconceived that they are installing a bigger. But in certain industries with certain technical threshold, such as photovoltaic industry, some professional terms in Chinese seem too academic and difficult to remember. At this time, throwing out its short English name can make it appear that our photovoltaic practitioners are both professional and concise. Let’s look at the following photovoltaic professional terms that must be mastered
1. Terms related to components
STC: Standard Test Conditions, i.e. ambient temperature 25 ℃, atmospheric quality AM1.5, wind speed=0m/s, 1000W/㎡. STC is a test condition, mainly for laboratory use.
NOCT: Normal Operating Cell Temperature refers to the temperature reached when the solar module or battery is in an open circuit state and at (surface light intensity of the battery=800W/㎡, ambient temperature=20 ℃, wind speed=1m/s). NOCT is a temperature, and the NOCT of normal components is 45 ℃± 2 ℃.
BIPV: Building Integrated Photovoltaic, which combines solar cells with building materials and is directly applied to the roof and wall of buildings and other enclosure structures. Photovoltaic materials used in photovoltaic buildings are reflected in the form of building materials, so photovoltaic building materials not only assume the power generation function, but also play the building function. The integrated application of building photovoltaic needs to meet the building safety requirements first, and then power generation.
PERC: emitter passivation and back contact battery, with a market share of about 90%, is the most mainstream type of battery in the current market.
TOPCON: Tunneling oxide passivation contact battery, N-type battery technology, high theoretical efficiency limit, and similar process to PECR.
HJT: The heterojunction battery with intrinsic amorphous layer adopts different semiconductor materials to form heterojunction PN nodes, with high theoretical efficiency and few processing steps, but extremely high technological requirements.
IBC: interdigital back contact battery.
2. Component parameters
Pmax: With the increase of voltage V, the output power will continue to rise, but it will decline after passing a certain point. This point corresponds to the maximum power output Pmax. At this time, the corresponding voltage Vmp (peak voltage) and the corresponding current is Imp (peak current). The module power characteristic curve is a 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 under the open-circuit condition 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 under the condition of positive and negative pole short circuit of the component, and the voltage value is “0” at this time.
Module efficiency: the efficiency of converting the radiant energy received by the PV module into output power per unit time under test conditions.
Operating temperature: the maximum and minimum temperature range of the component.
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 components under IEC/UL standards (involving the insulation, withstand voltage and other performance of components).
Maximum fuse rated current: overcurrent protection, which is greater than the maximum working current of the working point, used to protect components and cables.
Battery arrangement: the number of packages (72144) of batteries in series and parallel in the module.
Junction box: It is used to connect and protect solar photovoltaic modules, connect solar cells with external lines, and conduct the current generated by photovoltaic modules.
Module size: the radiation area of the module determines the conversion efficiency.
3. Terminology related to power station and system
Capacity ratio: refers to the ratio of the installed capacity of the photovoltaic system to the rated capacity (capacity ratio=the installed capacity of the photovoltaic system/the rated capacity of the photovoltaic system). If the capacity ratio is properly increased within a certain range, it can improve the utilization rate of other equipment, dilute the investment cost, reduce the cost of construction and power generation, and also make the output smoother and improve the grid friendliness.
1) Photovoltaic power stations generally balance the peak power generation and the reduction of equipment costs by setting a reasonable capacity-allocation ratio through active over-allocation.
2) Attention shall be paid to the power of the inverter, the number of accessible strings, and the overload capacity when increasing the capacity ratio.
AGC: Automatic generation control (AGC), i.e. active power control system, receives signals from telecontrol devices, responds to the telecontrol commands issued by the dispatcher, and makes the operation data meet the requirements of dispatching and grid connection through the optimization calculation of the AGC module total strategy.
AVC: Automatic Voltage Control (AVC), which means reactive voltage regulation. According to the grid voltage curve, it can quickly respond to the dispatching command, automatically adjust the reactive power, reactive compensation device and other control strategies and response time to achieve the voltage regulation goal and reduce the network loss.
Low Voltage Ride Through technology of photovoltaic power station: refers to that the photovoltaic power station can be connected to the grid uninterruptedly within a certain range when the voltage fluctuation of the grid connection point of the photovoltaic power station is caused by grid failure or disturbance.
PCC: Point of Common Coupling, where one or more user loads are connected in the power system.
POC: Point of Coupling, where no other customers are connected.
Collecting line: in the photovoltaic power generation system with decentralized inverter and centralized grid connection, the DC and AC transmission lines that collect the power output from each PV module string to the inverter through the combiner box and then to the generator bus through the output end of the inverter are called collecting lines. The collection line can be transmitted by overhead, direct burial or bridge laying.
Dedicated line access: dedicated switchgear (bay) for distributed power supply is set at the connection point of distributed power supply, such as direct access of distributed power supply to substation, switching station, distribution room bus, or ring network cabinet.
T connection: there is no special switchgear (bay) at the connection point of the distributed power supply, such as the direct connection of the distributed power supply to the overhead or cable line. (This method is applicable to less important loads (transformers).).
Combiner box: can be divided into DC combiner box and AC combiner box.
The DC combiner box is installed between the PV module and the inverter. It is a wiring device to ensure the orderly connection and confluence function of the PV module in the PV power generation system. The device can ensure that the photovoltaic system is easy to cut off the circuit during maintenance and inspection, and reduce the scope of power failure in case of failure of the photovoltaic system.
The AC combiner box is installed between the AC output side of the inverter and the grid-connected point/load. Its function is to collect the output current of multiple inverters and protect the inverter from the harm from the AC grid-connected side/load. As the output disconnection point of the inverter, it improves the safety of the system and protects the safety of the installation and maintenance personnel.
Photovoltaic grid-connected cabinet: as the total export of photovoltaic power station, it exists in the photovoltaic system. It is a device connecting the photovoltaic power station and the power 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. It has a full range of protection functions, such as loss of voltage opening, detection of voltage closing, overcurrent protection, overvoltage protection, island protection, anti-reverse current protection, harmonic control, reactive compensation, etc. It also has the ability to display the operating parameters and status indicators of photovoltaic power generation system, and is widely used in photovoltaic power generation systems. It can be used together with photovoltaic grid-connected inverters to form a complete set of photovoltaic power generation system solutions.
Full power generation hours: refers to the ratio of the final grid-connected AC power generation capacity of the grid-connected photovoltaic power generation system to the rated power of the photovoltaic system over a period of time, which is used to compare the power generation capacity (kWh/kW) of the photovoltaic system with different installed capacity.
In addition, there is the concept of theoretical full hours. The theoretical full hours is the ratio of the total radiation of the inclined plane of the photovoltaic array per unit area to the standard irradiance (1000W/㎡) of the photovoltaic cell under the standard test conditions, also known as the peak sunshine hours of the square array, reflecting the local radiation level.
Peak hours: a unit describing solar radiation, used to compare solar energy resources in different regions.
The calculation formula is peak hours H=total radiation on the inclined plane/(1000W/㎡).
Utilization hours of power generation equipment: refers to the operating hours of the average power generation equipment capacity in a region under the condition of full load operation in a certain period, 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 total number of available hours in a year. In the annual 8760h, the proportion of utilization hours of power generation equipment is also called “equipment utilization rate”.
High, medium and low voltage grid connection of photovoltaic power stations: generally, low voltage 380V grid connection can be carried out for industrial and commercial enterprises with 400kW and below, and low voltage grid connection can be carried out at multiple grid connection points between 400kW and 2MW. 10kV grid connection is required for those with more than 2MW, and 35kV grid connection is required for those with more than 6MW (refer to the requirements or suggestions of local grid companies for details).
AC and DC cables: The power supply is divided into AC and DC cables, so the cables for power transmission are also divided into AC cables and DC cables.
AC cables are used to connect AC power cables. AC cables are often used in power systems with power frequency (domestic 50HZ).
DC cable is used for power cable in DC transmission and distribution system. The structure of DC cable is basically the same as that of AC cable, except that the electrical characteristics of DC cable are different from that of AC cable. DC cables are mainly used in long-distance submarine cable lines. (PV cable refers to DC cable.)