Innovative Power Semiconductors for Your Application

To address the accelerating transition to renewable energy and the significant interest in semiconductors for photovoltaic (PV) applications, Hitachi Energy is introducing the 1200 V 600 A x 2 LoPak module, which joins the 900 A x 2 LoPak module introduced in 2021 and the original 1700 V LoPak family. This 600 A module takes advantage of the same upgraded LoPak package used for the 900 A x 2 version.

 

Renewable Energy Transformation - Photovoltaic Inverters

 

Hitachi Energy’s 1200 V LoPak	Temperature	VCE,sat	Vf	Eoff	Eon	Erec	IGBT short circuit SOA	Short circuit current
600 A x 2	175 °C	1.83 V	1.65 V	115 mJ	267 mJ	34 mJ	6 µS	2500 A
900 A x 2				178 mJ	171 mJ	46 mJ	6 µS	3350 A

Figure 1. 1200V module key parameters. Image used courtesy of Bodo’s Power Systems

 

The bond wire material has been changed to copper (Cu) for the DBC/DBC and DBC/power terminal to support the very high current levels. The number of wires was also increased and a coated Cu power terminal supports the increased power rating. The increased performance is delivered in a module with unchanged form and function unchanged from the other members of the LoPak family, and there is an option to have a pre-applied Thermal Interface Material (TIM) installed on the base plate to improve thermal conductivity (Rth).

 

Renewable Energy Transformation - Offshore Wind

To connect 15 MW offshore wind turbines as energy sources to the grid, Hitachi Energy offers a portfolio of reverse conducting and Asymmetric IGCTs. Hitachi's most recent products are the new 3rd generation 4.5 kV Reverse conducting- and Asymmetric IGCT in L size housing with a pole piece of 85 mm.

The new devices are available in two variants. One is optimized for converters with a medium switching frequency, which is often used in offshore wind turbines or medium voltage drives. A second variant optimized for low switching frequencies is intended for multi-level converters. The new Asymmetric IGCT has a turn-off current of 6500A, a record value for a device in this class, enabling the user to further optimize the converter design in terms of cost, size, efficiency and performance.

The mechanical design has a major influence on the performance and reliability of an IGCT device. By applying an outer gate ring structure, it was possible to use a monolithic cathode side moly. This allows for more efficient and homogeneous wafer cooling on the cathode side compared to previous generations of the IGCT. By applying an asymmetric anode and cathode-side pole piece, the total thermal impedance was lowered. The result is a device with significantly improved thermal performance and increased reliability.

A 10 kV device is the simplest and most cost-effective way to increase system voltage while using a familiar converter topology. Hitachi Energy has developed a new platform consisting of 10 kV RC- and Asymmetric IGCT and a companion diode, which allows users to design using compact, highly reliable and cost-optimized semiconductors tailored for their specific configuration and application.

 

Figure 2. Key device parameter comparison for 4.5 kV Asymmetric IGCT generations. Image used courtesy of Bodo’s Power Systems

 

Renewable Energy Transformation - HVDC & FACT

In HVDC and FACTS, converters are used that operate at dozens of kilovolts. To function at this very high voltage, many semiconductors need to be connected in series. The converters in the most common topology used today - the MMC - are required to have high blocking voltage capability; low on-state losses; high capability to deal with fault cases (SOA and Surge Current); and outstanding reliability to guarantee an operating lifetime of more than 30 years. To ensure these requirements are met, Hitachi Energy has developed a package specifically for HVDC & FACT applications, the StakPak. Importantly, the semiconductor chip inside, the Bimode IGBT (BIGT), best meets the requirement of high SOA and Surge Current. In the last year, Hitachi has launched the next generation of this chip, the BIGT2.

The BIGT2 improves on the previous generation by increasing current density by roughly 30%. This is achieved by redesigning the Termination (figure 3); optimizing the cell and the pitch; and optimizing the crucial design of the back side integration.

An important design criterion of the converters is - fault capability, and the - BIGT2 provides an improvement of over 30% versus the original BIGT. Even more impressive is the Surge Current Capability, with BIGT2 having a capability of 9 kA (10 ms pulse) in a module with the same footprint as the previous generation.

 

Figure 3. Schematic cross-section comparing the BIGT and BIGT2 chip with the improved areas highlighted accordingly. Image used courtesy of Bodo’s Power Systems

 

Moving People Across the World – E-Mobility and Charging

After ramping up the production of the LV LinPak platform during 2016, with the first products operating at 1700 V and 3300 V, Hitachi Energy now offers state-of-the-art 3.3 kV, 4.5 kV and 6.5 kV modules with 10.2 kV isolation voltage. For trains operating on 3 kV DC lines like those in Italy, Poland and parts of Czech Republic, a two-level converter with 6.5kV IGBT modules or three-level converter with 3.3 kV is available. Depending on the earthing scheme, 10.2 kV isolation for the three-level converter with 3.3 kV modules may be needed.

In designing these modules, great care was taken to optimize the electromagnetic behavior during switching and short circuiting. This ensures a smooth switching behavior with minimum oscillations, enabling high switching speeds. Moreover, since the modules are smaller than the standard HiPak modules used previously in Traction applications, the design was optimized for parallel operation. This enables converter designers to take a modular approach, selecting the number of devices to be paralleled based on the power level required. To meet the needs of the highest reliability Traction applications, a 10 us short circuit capability will be offered (figure 4a). By using the latest generations of chips, current ratings of 600 A, 450 A and 300 A are offered for the 3.3 kV, 4.5 kV and 6.5 kV respectively HV LinPak.

 

Figure 4a. Short circuit behavior for the 6.5kV 300A HV LinPak. Image used courtesy of Bodo’s Power Systems

 

Figure 4b. HV LinPak. Image used courtesy of Bodo’s Power Systems

 

RoadPak is a SiC and Si power module optimized for xEVs, e-busses and e-trucks. After the introduction of the 1200 V 580 A, 780 A and 980 A and the 750 V 660 A, 880 A, 1100 A modules with the lowest stray inductance of 5 nH and highest load cycling performance (up to 6’000’000 cycles), Hitachi is adding a smaller module with 1200 V 450 A and 1700 V 440 A to its RoadPak family. These products extend the superior behavior to a lower power range.

 

Increasing Productivity – Industrial Applications

Hitachi offers a complete thyristor product portfolio from small size low voltage to high voltage and 6” diameter.

Its latest product is a 6.5 kV thyristor in a 100 mm package. This is the first product based on the latest, next-generation industrial thyristor, which significantly improves device current performance. The 6.5 kV device offers more than 30% greater average current capability compared to other products in same voltage class. It achieves this, in part, by using the leading Snowflake gate design structure and latest backend technology features.

Along with the thyristor, Hitachi has developed a new rectifier diode with the same size and voltage rating that offers impressive performance at an increased voltage rating of 6.5 kV compared to previous generations that supported 5.5 kV.

 

Figure 5. Comparison of ratings for Thyristors and Rectifier Diodes. Image used courtesy of Bodo’s Power Systems

 

After successfully launching IGBT medium power modules in 2017, Hitachi is introducing a bipolar power module, the 60 Pak, which perfects the art of ultimate reliability. The first product to be launched is a diode device with a 60 mm industry standard housing.

For the best cycling performance and reliability, Hitachi's modules are based on pressure contact technology. The 60 mm housing is an industry standard that is footprint compatible with existing products in the market. Optimal heat transfer, highest insulation level and very low losses ensure the best performance in demanding applications.

 

Figure 6. BiPolar Module Portfolio. Image used courtesy of Bodo’s Power Systems

 

This article originally appeared in Bodo’s Power Systems magazine.