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PrimePACKTM Application in High Power Solar PV Inverters

Issuing time:2018-02-01 14:05
Keywords: solar inverter IGBT module Infineon

Source: Non-network

1 Introduction

With the ever-increasing use of electricity and the increasing demand for reducing greenhouse gas emissions, the new energy industry is experiencing unprecedented
Some speed development, of which solar energy is gaining more and more attention because of its convenient features. But solar energy
The floor space of the battery board is relatively large. If high-power grid-connected power generation is required, it only depends on the construction of high-power photovoltaic power stations. In recent years,
A large number of high-power photovoltaic power stations have been built in many countries, and high-power photovoltaic inverters, which are its core components, have also been developed.
Rapid development. The IGBT module has its own controllability, high voltage level, high current density, high switching frequency, etc.
Become a mainstream power device for high-power photovoltaic inverters. How current DC power generated by the panel is efficiently integrated into the grid
For people's research, efficiency is one of the most important indicators for evaluating photovoltaic inverters, and the topologies of high-power photovoltaic inverters are
Almost all three-phase full bridges, improving efficiency is mainly achieved by reducing the loss of IGBT modules. IGBT modules are used to improve inverters.

Efficiency is particularly important. PrimePACKTM is currently the latest generation of high power IGBT modules from Infineon.
Power applications are widely used.

2 High Power PV Inverter Working Principle
The direct current generated by the square array of the solar panel meets the grid through the sinusoidal pulse width modulation of the photovoltaic inverter to the grid
The power of the specified index, and the power fed to the grid by the inverter, is determined by the power of the photovoltaic array and the local sunshine conditions at that time. inverse
In addition to having the basic function of converting alternating current generated by solar panels into a specific voltage and frequency, inverters also provide
Must have MPPT (Maximum Power Tracking) capability to reliably monitor grid disturbances and fail in the grid
Disconnected from the grid.
Most of the high-power PV inverters are grid-connected, and the circuit topology is basically a three-phase full-bridge. Figure 1 shows high-power grid-connected photovoltaics.
Typical topology of the inverter (IGBT module as a full-bridge inverter power device). From this topology you can see the entire inverter
The loss mainly comes from IGBT modules and transformers, so how to select IGBT modules to improve inverter efficiency becomes a
Research hotspots.

Figure 1 Typical topology of high-power grid-connected PV inverters
3 PrimePACKTM Introduction
PrimePACKTM is the latest generation of IGBT modules from Infineon and is now widely used in wind power, solar power and other applications.
For high-end applications, it has the advantages of small parasitic inductance, low thermal resistance, and is equipped with a fourth-generation IGBT chip and anti-parallel two.
In the pole tube, the temperature and power cycle of the entire module are greatly increased.
3.1 Low parasitic inductance design
As shown in Figure 2, the positive and negative busbars in the PrimePACKTM module use a stacked busbar design with relatively low parasitic inductance.
The typical parasitic inductances of the half-bridge structures PrimePACKTM2 and PrimePACKTM3 are 18nH and 10nH, respectively.

The parasitic inductance of the entire half-bridge of the corresponding original IHM module will reach 45nH, and the parasitic inductance phase of PrimePACKTM
More than 50% lower than.
The no-load voltage of solar panels is relatively high, sometimes up to 900V, almost reaching the mother of 1200V modules.
Line voltage limit. In addition to the relatively small design requirement of the parasitic inductance of the busbar, the requirement for the internal parasitic inductance of the IGBT module
Higher, so PrimePACKTM is very suitable for photovoltaic inverter design. In addition due to the parasitic power of PrimePACKTM
A lower level of sense can drive the PrimePACKTM faster, reducing switching losses and increasing inverter efficiency.

a) PrimePACKTM2 b) PrimePACKTM3
Figure 2 The laminated busbar design of PrimePACKTM
3.2 Low Rthch (Shell to Radiator Thermal Resistance) Design
As shown in Figure 3 corresponding to the internal DCB substrate, PrimePACKTM2 and PrimePACKTM3 use 10 and
14 screws to secure the copper substrate and the heat sink, on the one hand it can better fit the PrimePACKTM slender package, and the other
The aspect can make the IGBT chip on each substrate get almost symmetrical heat dissipation conditions, so Rthch can be greatly reduced.

a) PrimePACK2 b) PrimePACK3
Figure 3 Screw position of PrimePACK

The result is very obvious: The copper substrate area of PrimePACKTM2 is 153cm, and the module's Rthch is 4K/kw.
The area of the copper substrate of the IHM module corresponding to the half-bridge structure is 182cm, but the typical value of the module's Rthch is 6K/kw.
It can be seen that PrimePACKTM2 achieves a smaller Rthch with a smaller copper substrate area, which is very beneficial for heat dissipation.
3.3 IGBT4 and Emcon4
3.3.1) IGBT4
Because PrimePACKTM is a new package, it contains the latest 4th generation IGBTs.
All are IGBT chips based on trench gate termination technology. Its biggest advantage is that its saturation pressure drop is very low and it is more suitable
Combined with high power applications to improve system efficiency. According to different applications, the first one is placed in the PrimePACKTM
Four generations of E4 chips and P4 chips.
The E4 chip is mainly aimed at mid-power applications. It deals with the chip's soft characteristics and switching losses in a guaranteed ratio.
With a smaller turn-off loss, better soft characteristics are obtained. The P4 chip is mainly optimized for high power applications.
The turn-off characteristics of the chip are very soft, but the corresponding turn-off losses also increase, making it suitable for high-current applications.
3.3.2) Emcon4
The anti-parallel diodes of all IGBTs in PrimePACKTM are the latest generation of Emcon4, and according to the
Diodes are also optimized for different IGBT chips. Emcon4 is mainly to make its reverse recovery softer, which makes IGBT
The turn-on characteristic becomes softer and reduces EMI, which allows faster turn-on resistance at the same softness
The IGBT is turned on to reduce the turn-on loss.
3.4 Power cycles and temperature weeks have been significantly improved
PrimePACKTM has optimized the coating of IGBT chips, and the parameters and connection technology of the connection lines have been greatly improved.
Therefore, the power cycle is significantly increased. From Figure 4, it can be seen that the power cycle of PrimePACKTM is at a working junction temperature of 125 degrees.
It is 4 times faster than IGBT2 and IGBT3. If the working junction temperature of PrimePACKTM is raised to 150 degrees, PrimePACKTM
The power cycle is twice that of the previous IGBT2 and IGBT3.

Fig. 4 Power cycles of 1200V and 1700V IGBT2, IGBT3 and IGBT4

PrimePACKTM has made many improvements in order to achieve higher temperature cycles: use enhanced as the substrate
Reducing the thermal expansion coefficient between the copper substrate and the substrate; adding a bracket between the copper substrate and the substrate so that the copper substrate and the substrate
The welding is more uniform; an ultrasonic welding process is used between the power terminals and the substrate. All of these make PrimePACKTM
The temperature cycle is significantly increased compared to the IHM (as shown in Figure 5), although its temperature cycle has not reached the traction level standard.
(AlSiC plus AlN substrates are expensive, but there is no question that PrimePACKTM is the best value for money.)

Figure 5 Temperature cycles of IHM, PrimePACKTM and traction IHM
Due to improvements in PrimePACKTM power cycles and temperature cycles, the lifetime of IGBT modules in photovoltaic inverters
It has reached 20 years or more (battery plate service life is 20 years) and can well cooperate with the long-term safe operation of the entire photovoltaic system.
4 PrimePACKTM Application in High Power PV Inverters
At present, PrimePACKTM has been widely used in high-power photovoltaic inverters with power of 100KW and above.
It has become the mainstream power device for photovoltaic inverters of this power class.
4. 1) Application of PrimePACKTM Package

PrimePACKTM is a relatively large package. PrimePACK is designed based on the current level.
And PrimePACKTM 3 package.
For the 1200V/450A IGBT module, we use two different packaged IGBT modules to compare (see Figure 6).
EconoDUAL3 package (copper substrate area 122*62mm) in FF450R12ME4 and PrimePACKTM2 packages (copper based
Board area 172*89mm) FF450R12IE4.

a) EconoDUAL3 package b) PrimePACK2 package

Figure 6 FF450R12KE4, FF450R12ME4, FF450R12IE4 Package Comparison
Take a 100kw PV inverter as an example, the operating parameters are: bus voltage Vdc=500V, effective current Irms=213A, switch
Frequency fsw = 5KHz, turn-on gate resistor Rgon/off = 2.5Ω/3.1Ω, heat from the EconoDUAL3 heat sink to the environment
The resistance was obtained using Infineon's loss and thermal simulation software IPOSIM as shown in Table 1 (all based on an IGBT
Loss simulation of the unit):
Obviously PrimePACKTM2 Due to the large copper substrate area, the thermal resistance Rthch from the case to the heat sink is EconoDUAL3
In half, so at the same loss and the same ambient temperature, the junction temperature of PrimePACKTM2 is low, which in turn makes IGBT
The saturation voltage drop and switching loss of the chip are reduced, so that the total loss is reduced and the same drive resistance can be found
The FF450R12IE4 is 0.15% more efficient than the FF450R12KE4.

Table 1 Simulation results of FF450R12ME4 and FF450R12IE4 in 100kW PV inverter

Note: IGBT conduction loss---- IGBT conduction loss; IGBT switching loss---- IGBT switching loss;

Rthjc(per IGBT)----The thermal resistance of the IGBT chip to the shell; Diode conduction loss----Diode conduction loss;

Diode switching loss—diode switching loss; Rthjc(per Diode)—the thermal resistance of the diode chip to the shell; Rth heatsink(per arm)—--- radiator pair

Thermal resistance of one IGBT and diode unit; Total loss----total loss; Tj----junction temperature

4.2) Application of High Current Level PrimePACKTM in PV Inverter
Photovoltaic inverters are different from ordinary inverters in that they pursue high efficiency, so they require less IGBT losses, as shown in Figure 7.
VS600R12IE4 and FF900R12IE4's Vcesat--Ic (saturation drop-current) graph, can be seen from the map
600A current at a junction temperature of 150°C, the saturation voltage drop of FF900R12IE4 is 1.6V, and the saturation voltage drop of FF600R12IE4 is
2.1V, so the conduction loss varies greatly.

a) FF900R12IE4 b) FF600R12IE4
Figure 7 Saturation voltage drop at 600A for FF600R12IE4 and FF900R12IE4, respectively
Take a 200kw PV inverter as an example. The operating parameters are: bus voltage Vdc=500v, effective current Irms=426A, switch
Frequency fsw=5KHz, turn-on gate resistor Rgon/off=1.8Ω/2.2Ω, using Infineon's loss and
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