Siemens

Types Of Power Converters In A PV System

SolarInvertersNA1One of the most important parts in PV system architecture is the power converters. The reason is that they play an important role in transforming the different types of electricity, to make the electricity convenient to the end users. Since the solar cell produces a DC type of electricity, there’s room for various types of power converters. Here, some of the most commonly used power converter types are briefly describe according to their topology, function, efficiency, and the major global manufacturers.

1. Power optimizer: Commonly known as a DC-DC power optimizer in solar PV markets, a power optimizer is a module-level power converter. It takes DC input from the solar module and gives either higher or lower DC output voltage. Such a converter is equipped with an MPPT technology to optimize the power conversion from the solar panel to the DC load or a battery or central inverter. It is also considered one of the most efficient power converters, delivering up to 99.5% efficiency. However, it needs DC cabling from the array. Some of the major players in this power converter market are SolarEdge and Tigo Energy.

2. Module inverter/micro-inverter: This is also a module-level power converter. It takes DC input from the solar module and converts it into AC electricity, which is then ready to be connected to the load or single-phase main grid or to a central inverter. It is also equipped with MPPT technology to detect the maximum power point of each module. Even though it doesn’t requires any DC cabling, it is more expensive than the power optimizer due to its advanced design. The efficiency of such a power converter is about 96%. The important players in this power converter market are Enecsys and Enphase.

3. String inverter: As an extension of a module-level power converter is the string inverter, which is suitable for a string or parallel strings of modules connected in series. Such a power converter is used for small PV systems up to 10 kW in capacity and are usually connected to the main grid. The output of such a power converter is 3 phase lines which are ready to be connected to a low voltage main grid. Even though it is incorporated with MPPT technology, due to the connection of a large PV array, it has a global maximum power point (MPP) which then degrades the efficiency of the PV system. In order to improve the efficiency, it would be wise to use a module inverter first and then the string inverter. However such configurations are more expensive. Apparently, one of the cons in such power converters is that the PV system is highly affected by shadowing on PV modules, thereby pulling down the system efficiency as low as possible. Meanwhile, many researchers are investigating a new MPPT algorithm to get the most efficient global MPP to overcome the shadowing affect. Players include SMA, Power One, Fronius, and Delta Energy Systems.

4. Central inverter: In large PV power plants (10 kW and higher), central inverters are used instead of string inverters. However, the central inverters’ functionality remains the same (i.e, to produce a 3-phase high voltage output for grid integration), which is why this power converter is considered essential for connecting with the main grid. In many large PV power plants, central inverters are inevitable. But there are many losses within the PV system due to their large and complex configuration. However, to mitigate such losses, some of the manufacturers, like Siemens, have developed a master-slave arrangement, such that at low irradiance the system efficiency will increase. 

This report from Solarpraxis AG allows a deeper dive into these solar PV technologies. In my next article, I’ll provide a comparative analysis of power optimizers and module inverters, focusing in more depth their pros and cons.

Image Credit: Delta Products Corporation

Types Of Power Converters In A PV System was originally published on Solar Love!.

USA High-Speed Rail Gets Boost — 32-Train Order For Siemens Trains


Originally published by the ECOreport.

Rendering of Siemens "Charger" diesel-electric locomotives - courtesy Siemens

Rendering of Siemens “Charger” diesel-electric locomotives – courtesy Siemens

Siemens has obtained a $225 million contract to build 32 “Charger” diesel-electric locomotives in its Sacramento rail manufacturing facility for US high-speed rail projects.


Five states are ordering locomotives. The Illinois Department of Transportation’s order is connected to an overhaul of its Chicago to St Louis route. California, Washington, Michigan, and Missouri have joined the deal, which includes options for an additional 75 locomotives for regional use and another 150 locomotives for mainline transportation. The locomotives are scheduled to be delivered between fall of 2016 and mid-2017.

“For Siemens this order marks our entry into the US diesel-electric locomotive market and strongly underscores our long-term vision for the US passenger rail market,” Jochen Eickholt, CEO of the Siemens Rail Systems Division, emphasized.

“The new Charger locomotives represent the next-generation of equipment advancing high performance intercity passenger rail in the Midwest, California and Pacific Northwest,” said Federal Railroad Administrator Joseph C. Szabo. “This state of the art equipment will accelerate and brake more quickly, reducing trip times for passengers, as well as being more fuel efficient and burning cleaner than previous locomotives for the benefit of the environment.”

The lighter weight locomotives can operate at speeds up to 125 mph. A diesel version of the “Charger” is currently pulling some 1,600 passenger and freight trains through-out Europe. The electric version was introduced in the US last year and already at work in the Northeast.

Train passing through a railway crossing against a blue sky with an interesting cloudscape. Motion blur is used to show the movement of the train. - Courtesy Siemens

Train passing through a railway crossing against a blue sky with an interesting cloudscape. Motion blur is used to show the movement of the train. – Courtesy Siemens

Some of the other features described in the Siemens press release include:

A state-of-the-art microprocessor control system manages the performance of the locomotive and performs self-diagnosis of technical issues, takes self-corrective action and notifies the locomotive engineer and the remote maintenance facility of any required corrective action. In addition, there are redundant systems to ensure optimal performance and availability such as a totally redundant auxiliary power supply for the passenger coaches to keep primary systems such as lighting, communications, heating and cooling systems working. The locomotives meet the latest federal rail safety regulations, including enhanced carbody structure safety with crash energy management components.

In total, this new rail equipment can help operators achieve cost savings by enabling reduced trip times, while improving reliability and efficiency for its passenger rail service. The lighter weight of these locomotives ensures the ability to safely operate the locomotives at speeds of up to 125 mph more efficiently, requiring less maintenance for both the locomotive and the infrastructure.

All the locomotives main components will be produced in Siemens plants in the United States.

USA High-Speed Rail Gets Boost — 32-Train Order For Siemens Trains was originally published on CleanTechnica. To read more from CleanTechnica, join over 50,000 other subscribers: Google+ | Email | Facebook | RSS | Twitter.