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PrimePACK™在大功率太阳能光伏逆变器中的应用

2
发表时间:2018-02-01 14:05

Keywords: solar inverter, IGBT module, Infineon

Source: Yufei.com

1 Introduction

As electricity consumption increases year by year and calls for reducing greenhouse gas emissions are getting higher and higher, the new energy industry is undergoing an unprecedented
Some speed development, wherein solar energy is just more and more widely concerned by people because of the characteristics of easy access. but solar
The battery panel covers a relatively large area. If high-power grid-connected power generation is required, only rely on the construction of high-power photovoltaic power plants. In recent years
Many countries have built a large number of high-power photovoltaic power plants, and the high-power photovoltaic inverters as their core components have also received
Rapid development. Due to its own controllability, high voltage level, high current density and high switching frequency, the IGBT module has been
Become the mainstream power device of high-power photovoltaic inverter. How to efficiently integrate the DC power generated by the battery panels into the power grid?
As the focus of people's research, efficiency is one of the most important indicators for evaluating photovoltaic inverters, and the topology of high-power photovoltaic inverters is almost
Almost all of them are three-phase full bridges, and the improvement of efficiency is mainly achieved by reducing the loss of the IGBT module. The IGBT module is important for improving the inverter

Efficiency is particularly important. PrimePACK™, the latest generation of high-power IGBT modules from Infineon, is currently available
Power applications are widely used.
 


2 Working principle of high-power photovoltaic inverter
The direct current generated by the square array of solar panels is transmitted to the grid through the sinusoidal pulse width modulation photovoltaic inverter to meet the requirements of the grid.
The power of the specified index, the power fed by the inverter to the grid is determined by the power of the photovoltaic array and the local sunshine conditions at that time. inverse
In addition to the basic function of converting the direct current generated by the solar panel into alternating current of a specific voltage and frequency, the inverter also
It must have MPPT (Maximum Power Tracking) function, which can reliably monitor the disturbance of the power grid and
disconnect from the grid.
Most high-power photovoltaic inverters are grid-connected, and the circuit topology is basically a three-phase full-bridge. Figure 1 is a high-power grid-connected photovoltaic inverter.
Typical topology of an inverter (IGBT modules as power devices for a full-bridge inverter). From this topology it can be seen that the entire inverter
The loss mainly comes from the IGBT module and the transformer, so how to choose the IGBT module to improve the efficiency of the inverter becomes a
Research hotspots.

Figure 1 Typical topology of high-power grid-connected photovoltaic inverter
3 Introduction to PrimePACK™
PrimePACK™ is the latest generation of IGBT modules from Infineon, and has been widely used in wind energy, solar energy, etc.
It has the advantages of small parasitic inductance, low thermal resistance, etc., and is equipped with fourth-generation IGBT chips and anti-parallel two
The pole tube, the temperature cycle and power cycle of the whole module are greatly increased.
3.1 Low parasitic inductance design
As shown in Figure 2, the positive and negative busbars inside the PrimePACK™ module adopt a laminated busbar design, and the parasitic inductance is relatively low.
The typical parasitic inductance values ​​of PrimePACKTM2 and PrimePACKTM3 with half-bridge structure are 18nH and 10nH respectively, and

Correspondingly, the parasitic inductance of the entire half-bridge of the original IHM module will reach 45nH, and the parasitic inductance of PrimePACK™ is equivalent to
than a reduction of more than 50%.
The no-load voltage of solar panels is relatively high, sometimes reaching 900V, almost reaching the mother voltage that 1200V modules can apply.
line voltage limit. In addition to the relatively small design of the parasitic inductance of the busbar, the internal parasitic inductance of the IGBT module is required to be relatively small.
Higher, so PrimePACK™ is very suitable for photovoltaic inverter design. In addition due to the parasitic electricity of PrimePACK™
If the inductance is relatively low, the PrimePACK™ can be driven faster, thereby reducing switching losses and improving inverter efficiency.

            a)PrimePACK™2                                b)PrimePACK™3 
Fig. 2 Laminated busbar design of PrimePACK™
3.2 Low Rthch (case to heat sink thermal resistance) design
Corresponding to the internal DCB substrate as shown in Figure 3, PrimePACK™2 and PrimePACK™3 use 10 and
14 screws to fix the copper base plate and heat sink, on the one hand to better fit the PrimePACK™ slim package, on the other
On the one hand, the IGBT chips on each substrate can obtain almost symmetrical heat dissipation conditions, so Rthch can be greatly reduced.

              a)PrimePACK2                           b)PrimePACK3 
Figure 3 PrimePACK screw fixing position


The results are very clear: the copper substrate area of ​​PrimePACK™2 is 153cm, the Rthch typical value of the module is 4K/kw,
                                   
The copper substrate area of ​​the IHM module corresponding to the half-bridge structure is 182cm, but the typical value of Rthch of the module is 6K/kw, which can be
It can be seen that PrimePACK™ 2 has 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
Since PrimePACK™ is a new package, the chips inside it are all the latest fourth-generation IGBTs.
They are all IGBT chips developed based on trench gate field termination technology. Its biggest advantage is that the saturation pressure drop is very low, which is more suitable
It can be used in high-power occasions to improve system efficiency. According to the different application occasions, the PrimePACK™ is put into the first
Four generations of E4 chips and P4 chips.
The E4 chip is mainly aimed at medium power applications, and has made a compromise between the soft characteristics of the chip and the switching loss.
In the case of smaller turn-off loss, better soft characteristics are obtained. The P4 chip is mainly optimized for high power applications,
The turn-off characteristic of the chip is very soft, but the corresponding turn-off loss also increases, which is more suitable for high-current applications.
3.3.2) Emcon4 
The anti-parallel diodes of the IGBTs in all PrimePACK™ are the latest generation Emcon4 and are
Depending on the IGBT chip, the diode will also be optimized. Emcon4 is mainly to make the reverse recovery softer, so that the IGBT
The turn-on characteristic becomes softer, reducing EMI, which allows faster turn-on resistance with the same softness
The ground turns on the IGBT so that the turn-on loss is reduced.
3.4 Power cycles and temperature cycles have been significantly improved
PrimePACK™ has optimized the coating of IGBT chips, and the parameters and connection process of the connecting wires have been greatly improved.
Therefore, the power cycle is significantly improved. It can be seen from Figure 4 that at the working junction temperature of 125 degrees, the power cycle of PrimePACK™
It is 4 times that of the previous IGBT2 and IGBT3. If the working junction temperature of PrimePACK™ is increased to 150 degrees, PrimePACK™
The power cycles are twice that of the previous IGBT2 and IGBT3.

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

                                       
PrimePACK™ has made many improvements for higher temperature cycle: take advantage of the enhanced as a substrate
Reduce the thermal expansion coefficient between the copper substrate and the substrate; a bracket is added between the copper substrate and the substrate to make the gap between the copper substrate and the substrate
The welding is more uniform; the ultrasonic welding process is used between the power terminal and the substrate. All this makes the PrimePACK™
Compared with IHM, the temperature cycle is significantly higher (as shown in Figure 5), although its temperature cycle does not reach the traction level standard
(AlSiC plus AlN substrate is very expensive), but there is no doubt that PrimePACK™ has the best cost performance.

Figure 5 Temperature Cycles for IHM, PrimePACK™ and Traction Grade IHM
Improved lifetime of IGBT modules in PV inverters due to PrimePACK™ power cycle and temperature cycle improvements
It has reached more than 20 years (the service life of the battery panel is 20 years), which can well cooperate with the long-term and safe operation of the entire photovoltaic system.
4 Application of PrimePACK™ in High Power Photovoltaic Inverters
At present, PrimePACKTM has been widely used in high-power photovoltaic inverters of 100KW and above.
It has become the mainstream power device for photovoltaic inverters of this power level.
4. 1) Application of PrimePACK™ package

PrimePACK™ is a relatively large package, the PrimePACK is designed according to the size of the current level
and PrimePACK™ 3 packages.
For the 1200V/450A IGBT module, we use two different package IGBT modules for comparison (see Figure 6), namely
EconoDUAL3 package (copper base area 122*62mm ) of FF450R12ME4 and PrimePACK™2 package (copper base
Board area 172*89mm ) FF450R12IE4.

a)EconoDUAL3 package b)PrimePACK2 package

Figure 6 FF450R12KE4, FF450R12ME4, FF450R12IE4 package comparison
Take a 100kw photovoltaic inverter as an example, working parameters: bus voltage Vdc=500V, effective current Irms=213A, switch
Frequency fsw=5KHz, turn-on and turn-off gate resistance Rgon/off=2.5Ω/3.1Ω, the heat from the radiator of EconoDUAL3 to the environment
The resistance is obtained by using Infineon's loss and thermal simulation software IPOSIM to obtain the simulation results as shown in Table 1 (both are based on an IGBT
unit loss simulation):
It is obvious that PrimePACK™2 due to the large copper substrate area, the thermal resistance Rthch from case to heat sink is EconoDUAL3
Therefore, under the same loss and the same ambient temperature, the junction temperature of PrimePACK™ 2 is lower, which in turn makes the IGBT
The saturation voltage drop and switching loss of the chip are reduced, which reduces the total loss, and it can be found that using the same driving resistance
FF450R12IE4 is 0.15% more efficient than FF450R12KE4.

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

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

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

Diode switching loss----diode switching loss; Rthjc(per Diode)----the thermal resistance of the diode chip junction to the shell; Rth heatsink(per arm)----the heat sink for each

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

4.2) Application of PrimePACK™ of high current level in photovoltaic inverters
Photovoltaic inverters are different from ordinary inverters. They pursue high efficiency, so the IGBT requires less loss, as shown in Figure 7.
Vcesat--Ic (saturation voltage drop-current) curves of FF600R12IE4 and FF900R12IE4, it can be seen from the figure that the corresponding
At a junction temperature of 150°C and a current of 600A, 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 of FF600R12IE4 and FF900R12IE4 at 600A current
Take a 200kw photovoltaic inverter as an example, working parameters: bus voltage Vdc=500v, effective current Irms=426A, switch
Frequency fsw=5KHz, turn-on and turn-off gate resistance Rgon/off=1.8Ω/2.2Ω, using Infineon's loss and thermal simulation software
The simulation results obtained by IPOSIM are shown in Table 2 (all are based on the loss simulation of one IGBT unit):

                                   
5. The latest development of PrimePACK™
Due to the loss limitation of traditional IGBT and diode chips, the switching frequency of high-power photovoltaic inverters generally does not exceed
5KHz, the problem is that the filter inductance is large and the loss is large, so the switching loss of the IGBT and diode chip
It has become a bottleneck restricting the improvement of inverter switching frequency. In order to break through this bottleneck, Infineon has launched the KS4 IGBT core
chip and SiC diode chip, and packaged in PrimePACK™ 2, model FF600R12IS4F.
The KS4 chip is Infineon's fastest IGBT chip, with very small turn-off loss, suitable for high-frequency applications where switching losses account for the majority
In the case of partial loss, the reverse recovery loss of the SiC diode is zero, and there is only a small reverse loss of the parasitic capacitance, so
The combination of the two is especially suitable for high-frequency applications, and the higher the frequency, the more obvious the advantages.
We take FF600R12IE4 and FF600R12IS4F as examples for comparison, as shown in Table 3, FF600R12IS4F
Both the switching loss of the IGBT and the reverse recovery loss of the diode are significantly reduced.
Table 3 Parameter comparison between FF600R12IE4 and FF600R12IS4F

Eon—turn-on loss; Eoff—turn-off loss; Erec—reverse recovery loss; Qr—reverse recovery charge.

Still take the 100kW photovoltaic inverter as an example, the working parameters: bus voltage Vdc=500v, effective current Irms=213A, at
Using Infineon's loss and thermal simulation software IPOSIM for different switching frequencies, the simulation results are shown in Table 4 (both are based on
Loss simulation for one IGBT unit):

     
Table 4 Application comparison of FF600R12IE4 and FF600R12IS4F in 100kW photovoltaic inverter

fsw—switching frequency; Total Loss—total loss; Tvj—working junction temperature.

It can be seen that as the switching frequency increases, the total loss of FF600R12IS4F is significantly lower than that of FF600R12IE4,
At 20KHz switching frequency, the total loss is only 66% of FF600R12IE4. Therefore FF600R12IS4F is very suitable for high
frequency photovoltaic inverter applications.
6. Summary
PrimePACK™ is the latest generation of high-power IGBT modules launched by Infineon, which integrates the latest chips and packages
technology, very popular in high-power occasions. Photovoltaic inverters pursue high efficiency, PrimePACK™ chip and packaging technology can
Greatly reduce the total loss of IGBT to improve the efficiency of photovoltaic inverters, so it has been widely used in high-power photovoltaic inverters
It has become a mainstream power device for high-power photovoltaic inverters. Practice has shown that PrimePACK™ is a very suitable
Cost-effective IGBT modules for power photovoltaic inverter applications.


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