Technical Article

Efficient Inverters for PV Systems

October 20, 2015 by Andreas König

This article highlights Zeversolar that is a chinese manufacturer of PV inverters in the budget segment, making the solar energy available to everyone.

Chinese manufacturer Zeversolar is one of the leading manufacturers of PV inverters in the budget segment. Its goal is to make solar energy available to everyone through a combination of Chinese flexibility and German engineering. The Subsidary company of SMA is now launching new devices for residential and commercial roofs.

 

Inverters are the heart of a grid-connected PV system. Only when inverters run efficiently and reliably, does the PV system generate maximum yields. It is also helpful if the devices are easy to install and maintain. The Chinese inverter manufacturer Zeversolar has now developed new devices for residential and commercial roofs. These devices combine high efficiency with extremely low weight.

New string inverters for homeowners The six new string inverters in the Zeverlution series have nominal powers of between 1.0 and 3.68 kilowatts. Here, Zeversolar uses a patented topology that considerably reduces efficiency losses. An additional semiconductor switch prevents the energy from shuttling back and forth between the line choke and the input capacitor. This is because the switches inside the inverter that regulate the flow of current between the input and output open and close at high clock speeds, which means that inverters are constantly fluctuating between feeding and not feeding, resulting in oscillations in the feed-in current and conversion losses. On the Zeverlution devices, the new pulsing and the additional switches now ensure that the current cannot flow back to the input capacitor during the freewheeling period, which reduces losses and thereby increases efficiency.

 

Figure 1: Produktion of Zeversolar

Figure 1: Produktion of Zeversolar

 

Zeversolar Building

 

Because this design also calls for fewer power electronic components, reliability increases while at the same time the weight of the device is reduced considerably. At a maximum of 7.3 kilograms, the new devices only weigh half as much as their predecessors and can therefore be transported and installed very easily.

 

Zeversolar has installed a temperature sensor to control the temperature. Depending on the temperature, the DSP controls the output power of the inverter which is also referred to as derating. If the temperature is too high, the power of the inverter is decreased to protect temperature-sensitive components. Although the cooler can provide additional cooling capacity, maintenance costs and noise emissions increase.

 

Step-up converter for greater flexibility

In the Zeverlution 1000S, 1500S, 2000S and 3000S devices, a step-up converter converts the input voltage generated by the PV modules to a higher output voltage. In doing so, the window in which the inverter searches for the optimal operating point (MPP window) widens because the MPP min. value decreases as a result of low voltage, at which point a step-up converter runs while still increasing flexibility in the system design. The inverters achieve efficiency ratings of up to 97%.

 

Efficiency ratings of up to 97.8%

The two new Zeverlution 3000 SE and Zeverlution 3680 SE devices, however, work without a step-up converter and attain efficiency ratings of up to 97.8%. To ensure that the design is flexible regardless, the inverters, as well as devices with step-up converters, are compatible with smart modules and power optimizers (known as DC optimizers).

While the power optimizers are already integrated into the smart modules and replace the conventional socket, they can also be connected separately to any module. The power optimizers ensure that each individual PV module of a string is working at its Maximum Power Point (MPP) at all times. This prevents yield losses caused by partial shading, as individual shaded or defective modules do not affect the entire string.

 

New inverter for commercial applications

In July, Zeversolar launched the Zeverlution Pro 33K inverter for commercial applications. It has a nominal power of 33 kilowatts and a maximum efficiency rating of 98.5% and weighs only 58 kilograms. The device has two independent MPP trackers and works in a wide MPP range and with a maximum input voltage of 1,000 volts. It begins to operate even at a very low start voltage of 250 volts, which further increases yield. While the power optimizers are already integrated into the smart modules and replace the conventional socket, they can also be connected separately to any module. The power optimizers ensure that each individual PV module of a string is working at its Maximum Power Point (MPP) at all times. This prevents yield losses caused by partial shading, as individual shaded or defective modules do not affect the entire string.

those inverters without galvanic isolation, as even a single short circuit can cause considerable damage. For the plant safety, eliminating the risk of fatal ijury from electrical shock. Consequently, a patented method of measuring insulation resistance is already integrated into the Zeverlution Pro 33K.

 

About the Author

Andreas König worked as a global key account manager large scale storage at Zeversolar. He has a management skills that is in senior level with an international career in sales and marketing, strategy for new business development, turnaround business and remediation processes and market development within several international industries. Dynamic professional and strong team leader with demonstrated skills for intercultural management. Particularly interested in the sustainable energy sector and technology industries. 10 years of international operational experience in the solar industry and 12 years of consumer electronics with a proven track record in Europe. Since 2013 with the SMA Group, heading the European operations of the Zeversolar brand. Since 2009 in solar with manufacturers of systems for renewable energy production, heading the European sales organisations. From 1997-2009 in the consumer electronic branch with manufacturers of digital products, leading strong sales organisations and addressing the major chains in Europe on top decision level.