New technology of distributed photovoltaic power distribution network protection

( A) Over-current protection in the photovoltaic inverter, to track the sun the power point of pv arrays, but also the need for sampling, the sampling objects include three, respectively is dc voltage, dc current and ac current. As to whether circuit for

( A) Over-current protection in the photovoltaic inverter, need high power point tracking solar photovoltaic array, also need to sample. Sampling objects including three, that is, the DC side voltage, DC side and ac measuring current. This method is used to determine whether to over-current protection circuit, because of the characteristic of the photovoltaic inverter high resolution, high sensitivity to over-current protection circuit. For over current protection circuit, using the method of photovoltaic inverter, protection method by the over-current protection, over-current protection, drive circuit and main circuit over-current protection control circuit of three parts. ( 2) Over-voltage and under-voltage protection for small photovoltaic power station, when the grid voltage abnormal, overvoltage protection will play a role, according to the different situation in different time to stop to produce electricity. However, for large photovoltaic power station, should through the low voltage through the ability to improve the ability of power grid interference. To prevent lightning overvoltage and operating over-voltage, USES the photovoltaic power station overvoltage protection. Overpressure include two types: vertical and horizontal. Therefore, in the implementation of protection, should follow the principle of considering two kinds of over-voltage protection. Specifically, the photovoltaic power station there are two kinds of over-voltage protection measures: 1. Single stage protection mainly one-time to lightning and other transient voltage protection. Protection method is to use a rheostat and gas discharge tube. 2. Multistage protection is suitable for the single stage, single stage protection cannot have very good protection effect, inverter voltage level is low. ( 3) Frequency and low frequency protection in small photovoltaic power station, the specific frequency range for 49. 5 hz to 50. 2 hz. If the connection to the distribution network of distributed photovoltaic frequency exceeds the range, you may need to start over frequency protection. In large and medium-sized photovoltaic power station, must have the ability to resist abnormal system frequency interference. ( 4) The island protection when abnormal external power grid, will be a power outage. At this point, the connection to the distribution network of distributed photovoltaic power generation will continue to supply power to some of the power distribution system. This is called an island phenomenon, including planned and unplanned. Protection against the island is in an island phenomenon occurs, the photovoltaic power station and island system disconnection, eliminate the phenomenon of isolated operating conditions, prevent island endanger the user equipment and equipment maintenance.