Photovoltaic system is generally divided into ground power station-based centralized power generation system and small and medium-sized distributed power generation system, now mentioned distributed power generation, photovoltaic industry personnel think is distributed photovoltaic power generation, in fact, photovoltaic is only a branch of distributed, distributed power generation also contains other types of power generation forms, in the Development and Reform Commission promulgated the "Distributed Power Generation Management Interim Measures", the distributed photovoltaic power generation is so Distributed power generation is a power generation facility or a multi-coupling facility with power output that is installed at or near the user's site, operated mainly by self-generation at the user's end, with excess power going online and balanced regulation in the distribution grid system.
Article III of these measures apply to the following distributed generation methods.
Small hydropower plants with a total installed capacity of 50,000 kilowatts and below;
Wind, solar, biomass, ocean energy, geothermal energy and other new energy generation with various voltage levels connected to the distribution network;
In addition to direct coal combustion of a variety of waste power generation, a variety of complementary energy generation, waste heat and pressure, waste gas power generation, coal mine gas power generation and other comprehensive use of resources power generation;
Total installed capacity of 50,000 kilowatts and below of coal-bed methane power generation
Natural gas combined heat and power generation with a comprehensive energy utilization efficiency higher than 70% and local power consumption, etc.
From the above explanation, we can see that the scope of distributed power generation is still very wide, and basically includes all the current forms of power generation except nuclear power. Since various forms of power generation are very different, if a standard is rigidly adopted, it may result in a lot of wasted resources. As we can see in the "Design Code for Distributed Power Supply Access to Distribution Grid" published by the State Grid, some clauses do not match with PV projects.
3.1.2 Anti-islanding device
It can actively inject voltage or frequency disturbance signals into the distributed power supply network, eliminating the safety risks caused by the failure of anti-islanding detection of the inverter equipment itself.
5.6 C If the capacity of the inverter type distributed power connection exceeds 25% of the rated capacity of the station, the low-voltage side of the distribution substation should be transformed into a low-voltage main switch, and an anti-islanding device should be installed at the low-voltage busbar of the distribution substation; the low-voltage main switch should have an operation blocking function with the anti-islanding device, and when there is a contact between the busbars, the contact switch should also have an operation blocking function with the anti-islanding device.
The anti-islanding in the text, and the inverter standard anti-islanding, English is anti-islanding, and all the standards of photovoltaic system, China does not have the original, are translated from English, so it can be regarded as the same thing, anti-islanding function is the most basic one of the working mode of PV grid-connected inverter, there is no possibility of failure, so this article is not suitable for PV system.
5.4 Short-circuit current calculation: The short-circuit current provided by the distributed converter-type power generation system is calculated at 1.5 times the rated current.
The maximum short-circuit current of the module will not exceed 15% of the rated current, so this article is also not suitable.
It is recommended that a separate standard be built for distributed PV to avoid wasting resources.
