Voice of developers



PV Wireless String Monitoring System "solmivTM"
New Business Promotion Office
New Business Promotion Department
Akefumi Kosugi


PV Micro Converter "solhueruTM"
New Business Promotion Office
New Business Promotion Department
Tsutomu Masuda

What was the trigger for the development?

In 2010, we were given a mission to create new products for the renewable energy market. After conducting extensive research, we were convinced that photovoltaic power generation will continue to grow for a long time in this market. TAIYO YUDEN possesses the core technologies of power electronics and wireless communications. Our idea was to introduce a typical TAIYO YUDEN product into the photovoltaics market as an amalgam of these superior technologies.

The feed-in tariff (FIT) system commenced in July 2012. While the market is rapidly expanding, problems have gradually emerged―such as failure of PV modules and peripheral devices. It was not possible to ascertain the degree of such failures, so the amount of power lost could not be determined. In addition, the influence of shade was bigger than expected. Various problems arose.

Under this situation, we initially started to develop the String Monitoring System "solmivTM", which allows one to quickly grasp the detailed condition of a power plant. Following this, we also developed converter "solhueruTM", which can minimize the decline in the power generation caused by conditions such as shade.

Product concepts

There is a single common unifying concept for TAIYO YUDEN's solutions for photovoltaic power generation―easy installation. We designed our products in such a way that they can easily be installed by customers themselves regardless of whether a power plant is new or already established.

Advantages of "solmivTM" and "solhueruTM"


We studied various methods for the communications system between measurement master and slave units, such as differential wired systems and power line communication systems. We ultimately decided to use a noise-tolerant, low-loss wireless system since TAIYO YUDEN has a proven excellent track record over many years in wireless technologies. For high-precision failure diagnosis, we need to analyze and determine the failure both from current information and from voltage information. "solmivTM" is also equipped with a function to obtain voltage information from PV modules. Even if the measuring instrument is out of order, no impact on power generation will occur. In addition, since "solmivTM" supports coordinated operation with monitoring software from various host system vendors, it can be used in response to customer needs .


The biggest advantage of this system is that no host machine is required since individual "solhueruTM" devices can perform the control independently. They can be installed only to strings that generate a reduced amount of power due to shading, which means that they are cost effective. In addition, another advantage is that you don't have to choose a particular PCS.

Difficulties in development


Although photovoltaic power plants are thought to have a stationary environment, also making the wireless radio wave environment stable, it can in fact vary depending on the season, weather, and surrounding environment. Therefore, the wireless communication algorithm were so adapted as to be used for photovoltaic power generation. We had a difficult time achieving our expectations until such know-how was established.


We had a difficult time formulating a control algorithm that can run stably irrespective of the PCS combined.

In particular, we had a hard time with demonstration experiments that were conducted at actual power plants. We conducted demonstration experiments all over Japan to checked on the operation of the system. The development team members, who had previously been desk-bound workers, now were traveling throughout Japan with equipment such as a helmets, boots, and light shield belts. In some cases, we had to pay great attention to safety, wearing a life jacket occasionally. Although it was a quite tough job, we felt the greatest joy we had ever experienced when we were able to understood the actual sites, listened to needs directly, and fed information back the to product.


Compared to foreign countries, the status quo in Japan is that recognition of the necessity of string monitoring is quite low. There is always doubt about output, even when the expected amount of generation is attained. Owing to various defects, true profit potential might therefore not yet be attained. First, install "solmivTM" for string monitoring, and then improve diminished power output using "solhueruTM".
With the importance of service and maintenance increasing, we sincerely hope that TAIYO YUDEN products will be installed at many power stations, thus contributing to sound operations.

Development team (form the left, Kosugi, Masuda, Imai, and Ikeda)


For inquiries and consultations, PV Wireless String Monitoring System solmiv(TM) “PV Micro Converter solhueru(TM)” MPPT Control

Results of Adoption
Wireless Sensor Network