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In this paper, main different grid-connected photovoltaic (PV) standard systems, included IEC system, western country system, American system and China system have been summarized, analyzed and compared. Based on comparison between different standard systems, relative merits, existing difference, and reasons of difference have been analyzed in gird-connected PV standard system. Furthermore, combined with relevant PV generation policy and technology developing status, the prospect analyze has been proposed for future grid-connected PV standard system development in each system.

With the rapid increasing of solar power installed capacity, the utility has higher requirement to the Low voltage ride-through (LVRT) capability of grid-connected PV power station. The PV power station is expected to continue operation during the fault, especially the voltage drop of the grid. Therefore, the effective on-site test platform has been desired and needed thereby matching latest standards not only in China but also in the worldwide. In this paper, based on latest standards, one suitable and convenience on-site test platform and one on-site testing technique for Medium and large PV power plant is proposed and introduced. Meanwhile, the corresponding simulation result is verified the effectiveness and practicality.

This article provides a specially designed low voltage ride-through (LVRT) detection device, which uses the transformer tap switch to not only switch the taps of the reactors but also change the structure of the main circuit structure. The cost of this set of design solutions is only 10% of traditional testing device. This set of design can reduce the using number of reactors, increase testing device reliability, and improve the detection efficiency.

This article is a comparative assessment of grid-connected PV system standards between China, the U.S and Europe, analysis of the difference between the various standards. On the one hand, to provide a reference with the standards preparation and improvement of grid-connected PV system in China; on the other hand, to increase the understanding of Chinese grid-connected PV system standards, and to promote the common progress of the international PV standards.

For large-scale photovoltaic power station connected to medium-voltage grid, it is not proper to evaluate its power quality by traditional limitation in China. In this paper, it proposes testing technology and research in order to evaluate the power quality for large-scale photovoltaic power station according to latest photovoltaic standards. The tests will focus on flicker, harmonics, inter-harmonics and high frequency components. For voltage flicker under either continuous operation or switching operation, it gives one method which simulates the voltage fluctuation imposed by photovoltaic power station and calculates flicker emission on a fictitious grid, thereby avoiding the direct influence of the real voltage fluctuation of the grid at the measurement point on flicker. For current harmonics, interharmonics and high frequency components over continuous operation, it specifies the individual current components as sub grouped values in accordance with IEC 61000-4-7][1]. For the purpose of including the effect of voltage fluctuations during actual measurement, the choice of sub grouping method is applied.

A new type LVRT test device, basing on power electronics technology, has been developed. Compared with traditional reactor VGS, this device overcomes many drawbacks, such as bulky size, difficult to control precision, and difficult to continuously testing. Considering the characteristics of distributed system accessing to the grid by photovoltaic power station, the designed testing platform has the capability of flexible and mobile performance. In this paper, working principle, hardware and software structures, and features have been introduced. Meanwhile, Testing verification and data analysis also have been conducted in laboratory. Based on those procedures, the device has been verified for having excellent effectiveness and practicality. Over that period, the device has been applied and tested on site in the Qinghai, which had got the ideal result as well as in laboratory.

In recent years, Chinese government has published many subsidy policies for photovoltaic power, such as "BIPV" "Golden Sun Demonstration Projecti" and "Bidding for Concession". Meanwhile, several local governments also published their own subsidy policies to increase the investment subsidies or to publish electricity price in tariff for photovoltaic power projects. The publishing of these policies have been promoting the rapid growth in total amount of installed photovoltaic power. Furthermore, PV power permeability has reached an upper value in some region. The instability, random city, and upper permeability acting on PV power, bring serious influence to safe and stable operation of the grid in China. Therefore, State Grid Corporation of China (SGCC) has published two enterprise standards, Q/GDW 617-2011 "Technical specifications for photovoltaic power station connected to the grid" and Q/GDW 618-2011 "Testing procedures for photovoltaic power station connected to the grid", which specifies the prospective technical parameters at different voltage rating, capacity and grid-connected types, and required testing items and methods. Focused on grid connected PV power station, the standards specifies the requirement of testing parameters, including active power control, voltage/reactive power regulation, response to abnormal voltage/frequency, power quality, low voltage ride through (LVRT), anti-islanding protection, back-feed protection, reconnection, lightening & ear thing protection, electromagnetic compatibility, surge immunity, electric energy metering, and communication & signal. In this article, it will describe those two standards in details, and analyse specific parameter and established basis required by each technical clause.