Three different interpretation of the grid-connected photovoltaic (pv) way

1, completely spontaneous private mode this mode commonly used in the user side load is bigger, and electricity load last, few year under the condition of production or BanTingChan, or, even during the holidays, the users of electricity to maintain load is sufficient

1, completely spontaneous private mode this mode generally apply to the user side load is big, continuous electricity load, little or no power off within a year, even during the holidays, users maintain electricity load is big enough to absorb most of photovoltaic power station to produce electricity. Because of the low voltage side of the interconnection, if the user's electricity consumption cannot be absorbed, this type of system will be sent back to the upper grid through the transformer. But, the design of distribution transformer are not allowed to reverse transmission power ( It can be back in a short time, such as debugging, but can't be in a long time) Initial power flow, and its design is fixed. Therefore, it is necessary to install the backflow devices, to avoid the reverse power transmission. Given some users can't make sure its power consumption can continue to consume photovoltaic power generation, or production can't guarantee the sustainability of the project, suggested that do not use this way of interconnection. This mode is recommended for a single unit power below 500 mw photovoltaic power station, and the client side of distribution transformer, by increasing the voltage needed to increase the investment accounts for a high proportion of investment. 2, spontaneous self-used remaining power online mode for most of distributed generation is optimistic about the users, the surplus electricity access to the Internet is an ideal choice for private use of the model, so that they can get higher rates of for private use of electricity, and in the case of don't run out of power to sell electricity to the grid. However, there are a lot of resistance in the process of actual operation. Reason is the pv practitioners and personnel information asymmetry between the local power grid company, and the lack of the understanding of each other professional knowledge. This is why this pattern has become a pv electricity price policy and not understand part of the new policy of the state grid. When photovoltaic power generation in self-use surplus energy online mode, the user ( Or 'investors') Hope the energy generated within the enterprise is consumed as much as possible, if really didn't have to run out of words, can feed into the grid, so as not to waste this part of photovoltaic power. However, power companies want the user to have a simple choice, or their own use, or increase the voltage on the Internet. This is because for local electric power company, spontaneous private surplus electricity access to the Internet need some extra workload: calculate regional distribution network capacity ( Allow reverse transmission load) , increasing the management power points ( Pure spontaneous self-use by lowering the standards to manage) , conversion, forward and reverse meters after user tedious power consumption measurement ( User's actual electricity load curve and power consumption by electric meter value conversion for 1 and 2) And increase meter reading work, etc. And, of course, in essence, power companies are unable to get users to buy and sell for electric power price difference, this is the actual loss of the local power company. This not only increased the workload, and there is no real benefits. Therefore, investors will have a variety of reasons not to choose the networking scheme. However, as long as technically fully explain this is state grid company allows the rest of the power plan, and has a reasonable design draft, the local power company can't easily refused to investors. Many photovoltaic power station owners think, as long as the power grid access 3 meters ( 400 v) , photovoltaic power users can't accept, can be directly back to 10 kv distribution transformer ( Or 35 kv side) 。 However, as a matter of fact, it is not allowed. This violated the trend of the distribution network design, and may lead to the abnormal voltage of 400 v side and power factor. At the same time, some protective equipment may lose its function.