p o w e r i n g t o m o r r o w

PV Inverters Improvements in Industrial as well as Commercial Domains

The global generation of solar system has grown fast from 2010 because many countries have adapted advanced technologies. Recently, the main focus in distributed PV system, commercial solar system is, how to get rid of subsidy dependence and how to achieve grid parity have become the main problem and urgently require to be solved. Solar power grid parity for photovoltaic power station need further decrease in cost and increase in efficiency. Inverter is the key equipment of photovoltaic system, while the proportion in the whole system cost is not high but by improving the parameters and performance to optimize the system design, intelligent on-line service operations can play a vital role.

The cost reduction and efficiency increase method for inverter is shown below

MAC 50-70KTL3-X LV&MV series inverter

Adopt new high-efficiency, high-power module and use adaptable inverter The cost of photovoltaic modules accounts for more than 50% of the initial investment, which directly affects the cost of the project. However, the attenuation of solar panel efficiency leads to the increase of electrical cost. The attenuation rate of solar panel is calculated according to (10% in 10 years and 20% in 25 years). Due to the adoption of new high-efficiency high-power modules, the initial investment of photovoltaic system will drop more than 10%.The improvement of photovoltaic module conversion efficiency greatly reduces the parallel strings. Besides photovoltaic modules, inverters and other devices, including BUS boxes, DC cables, holder and foundations, will also be reduced.

ShineMaster

ShineServer PV Array MAC 60KTL3-X LV ShineMaster Router

485 BTS Cloud Server

PV Array MAC 60KTL3-X LV AC Combiner Box ACPD Grid ShinePhone

Medium and large scale commercial photovoltaic power station solution system diagram

1MW commercial solar plant (14 PCS 70KTL3-X MV inverter)

Solar panel Number of Number Number of Total power Ratio

panel per string of strings solar panel

275W 22 168 3696 1.0164MWp 1.037

305W 20 168 3360 1.0248MWp 1.045

350W 22 140 3080 1.078MWp 1.100

1MW unit commercial power station with different types of solar panel configuration table

For example a 1MW unit, adopt the same inverter and consider LONG JI brand 350W solar panel as an example, the number of solar panel can be reduced by 280~616 pieces, and the installation and transportation cost solar panel can be reduced by 7.6% to 16.6%.The number of strings can be reduced by 28 strings, saving more than 15% of the cost of holder and DC cables. According to the calculation of about 4800USD of DC cable materials and laying cost per MW and 50700 USD of holder materials and installation cost per MW, the whole system cost per MW can be saved by more than 8300USD.

The new high efficiency and high power solar panel can reduce the system cost, but due to the high power solar panel with high current puts new requirements for inverter and the inverter input current must meet the new efficient solar panel. Growatt new generation MAC and MAX series inverters were designed according to 12.5 A, it is new high- efficient and high-power solar panel gold partner and best match with the new advancements.

Solar panel Impp:11.01A Isc:11.81A

Inverter String current:12.5A Isc:13.75A

Inverter over-matched and over-load capacity

Due to solar panel loss, dust, shelter, line loss, series-parallel mismatch, insufficient sunshine factors, inverter actually receives the input power is often has reached around 87% - 92% of output power component, which cause the overall loss around 8% - 13%. As the industrial and commercial solar panel mostly use color steel tile roof installation, which cause loss of radiation, if solar panel and inverter according to 1:1 configuration, inverter with light load condition for a long time cause the utilization rate very low, so improve the system capacity ratio and appropriately over-match can improve the whole system benefits and reduce the electricity cost as well. This operation has been widely used, especially in areas such as the United States and Japan, where the ratio can exceed 1.5 times.

Solar radiation Dust , shelter, 3-5%

PV consistency, installation type, PV Strings wire loss 2-3%

Combiner box wire and component loss 1-2%

wire and component DC distributor System loss loss 1-2% 8-13% Inverter

Losses in the photovoltaic system

Different areas DC/AC recommendation

Installation type Class I areas Class II areas Class III areas

Optimal 1.1 1.2 1.3

installation angle

Lying flat install 1.2 1.3 1.4

Recommendation table for different installation methods based on different areas

Growatt commercial inverters MAC and MAX series have up to 1.3 times of DC over-matching capacity, and 1.1 times of overload capacity for AC, making over-matching easier and more secure.

Datasheet MAX
50KTL3
LV MAX
60KTL3
LV MAX
70KTL3
LV MAX
80KTL3
LV

Input Data Max.DC power 65000W 78000W 91000W 104000W

Max.DC voltage 1100V 1100V 1100V 1100V Start Voltage 250V 250V 250V 250V MPPT voltage range 200V-1000V 200V-1000V 200V-1000V 200V-1000V Nominal voltage 585V 585V 600V 600V

Max. input current per MPPT 25A 25A 25A 25A Number of MPP trackers / 6/2 6/2 7/2 7/2 strings per MPP tracker

Output (AC) Rated AC output power 50000W 60000W 70000W 80000W Max. AC apparent power 55500VA 66600VA 77700VA 88800VA Max. output current 80.5A 96.6A 112.7A 128.8A AC nominal voltage 230V/400V 230V/400V 230V/400V 230V/400V AC grid frequency 50Hz/60Hz 50Hz/60Hz 50Hz/60Hz 50Hz/60Hz

Power factor 0.8leading ...0.8lagging 0.8leading ...0.8lagging
0.8leading ...0.8lagging
0.8leading ...0.8lagging

THDi <3% <3% <3% <3% AC grid connection type 3W+N+PE 3W+N+PE 3W+N+PE 3W+N+PE Efficiency Max.efficiency 98.8% 98.8% 99% 99%

Adopt aluminum cable instead of copper cable Reduce the cost of cable investment In large commercial projects, cables account up to 10% of the system cost, higher than inverters cost. In fact as long as the design and installation are proper, under the condition of ensuring the normal operation and safety of the system, some AC cables are made of aluminum, which can reduce the investment cost of the system. Compared with the cost of copper cable, aluminum cable cost is lower, installation is more convenient, weight is lighter, and aluminum cable in the application of photovoltaic system has become more and more common.

However, under the same over current capacity, the diameter of aluminum wire is obviously larger than copper wire, and which need higher requirements for ac connection terminals of inverter and AC connector and waterproof terminals must be large enough to support aluminum cable with larger diameter. Currently, the MAC series of 50- 70kw inverters are compatible with up to 50 square mm aluminum wire, the MAX series of 60-70kw inverters are compatible with up to 70 square mm aluminum wire, and the MAX series of 80-100kw inverters are compatible with up to 95 square mm aluminum wire.

According to local conditions, select the appropriate MPPT strings inverter At present, there are many specification of MPPT inverter in the market. As the commercial 60kw inverter for an example, there are 1 ,3,4 or 6 strings number of MPPT inverter, Growatt 60KW inverter has three models: single MPPT Growatt 60KTL3 - HE, 3 MPPTs MAC 60KTL3 - X LV and 6 MPPTs MAX 60KTL3 LV model.

The choice of different MPPTs has influence on the power generation of the system. From the point of view of solving the mismatch problem, the fewer strings is best for one MPPT. In terms of stability and efficiency, it is better to have more strings for one MPPT, because the more MPPTs then higher the cost of the system, the worse stability, and the more losses. In the real-time application, the appropriate scheme should be selected according to the practical application scenario.

According to different application scenarios, Angle and orientation of solar array, shielding conditions of solar panel and consistency of the number of solar panel in each string, inverters with different MPPTs can reduce procurement and maintenance cost of power station, also improve economic benefits.

(1) In the case of flat roof without shelter, uniform orientation of solar array and complete consistency of group strings, it is recommended to choose one MPPT inverter, which can improve system reliability and reduce system cost;

(2) In the case of partial shelter, inconsistent orientation of solar array, and different number of solar array per strings, it is recommended to choose 3 MPPTs inverter, which can not only meet the design requirements, reduce the mismatch loss, but also reduce the cost;

(3) In the case of multiple orientations, multiple angles and large difference in number of solar array per strings, it is recommended to select 6-7 MPPTs inverters, which can maximize the mismatch loss and improve the design flexibility.

Intelligent, Reduced and Improved (service and maintenance efficiency)

It is known to all, photovoltaic power station is an up to 25 years of the life cycle of products, price bidding and grid parity. And the time has come, people more and more care about electricity cost, the investment of charge include construction costs and power plant generating cost, also there is a very important part is service and maintenance cost, thus how to reduce the service and maintenance cost of the power station and improve service efficiency to become the industry focus.

Solar inverter as the only intelligent devices in photovoltaic power station, in the process of power plant service intelligence plays an important role, it is not just an inverter, also a steward of the photovoltaic power station. It is not only realize intelligent diagnosis, warning ,remote parameter setting and the firmware upgrade, but also for photovoltaic modules intelligent IV curve scanning and accurate fault location, optimize the grid power quality , active and reactive power scheduling, Intelligent one-click diagnosis of the installation process and environment of the power station.

Growatt MAC and MAX series commercial inverters have the above intelligent service functions, which can improve service efficiency and reduce service cost for commercial photovoltaic power stations.

Intelligent IV curve scanning 3.5

3

2.5

2 R 1.5 S T 1

0.5

0 3 5 7 9 11 13 15 17 19

R S T 100% 100% 100% 0.32% 0.31% 0.34% 3.1% 3.02% 3.29% 1.11% 1.54% 1.14% 0.33% 0.47% 0.48% 1.54% 1.97% 2.14% 0.91% 0.82% 0.67% 0.17% 026% 0.31% 0.41% 0.47% 0.63% 0.26% 0.21% 0.23%

Power quality diagnosis

Conclusion

Solar power grid parity time has emanated, and trade of photovoltaic power station cost reduction become very critical. Solar inverter selection is particularly important, a smart and efficient inverter can help improve the efficiency of power generation, also to optimize the design of the system, improve life time cycle generating revenue, and reduce the construction cost of power plant. Intelligent service can save the cost of service in the complete life cycle. In order to regulate cost optimal, the selection of inverter become crucial.

Growatt New Energy Growatt New Energy Technology Co.,Ltd W:www.ginverter.com E:[email protected]