In view of concerns about energy sustainability and energy security, the current demand for energy storage systems is accelerating, especially in the area of residential solar installations. There are microreversers with power up to 2 kw and with integrated energy storage systems. When the system requires higher power, a serial reverser or a hybrid reverser that connects the energy system may also be used。
Figure 1 shows the box figure for the hybrid reversers. Common pressure straight-flow terminals connect the basic modules. Mixed string reversers contain the following sub-sections:
A one-way dc/dc converter to perform maximum power point tracking。
A two-way dc/dc converter for battery charging and discharge. Batteries can be supplied at night or during power outages。
The dc/ac converter is responsible for the conversion of direct currents to the power exchange and the maintenance of low current aggregate tuning (thd)。
Microcontrollers (mcu) for current and voltage measurement, power switches control, insulation monitoring, cavity detection and communication activation。
Power optimizationrs, which are used to maximize the power available for the photovoltaic panels and are not influenced by external variables such as irradiation and temperature。
Figure 1 principles of hybrid reversers connected to the grid figure
Comparison of igbt and gan fet
A serial reverser consists of a power switch, such as a bipolar transistor (igbt) of an insulation fence. This power plant has problems with tail currents and diode reverse recovery, which can lead to higher switch wear and tear. In addition, these phenomena are affected by temperature and lead to higher power losses, especially when static dispersion solutions are introduced. Therefore, these power units need to operate under low frequency and require larger passive components and radiators. The typical switch frequency ranges from 5 khz to 15 khz。
There are no few plumes of broadband pyrotechnic power switches such as nitrousium (gan) that can reduce switch losses. The reduction in switch losses allows the frequency of switches to be increased while system losses remain constant, thereby reducing the number of passive elements. On average, switch frequency can increase six times。
This paper proposes a 10kw serial reverser based on the gan field effect transistor (fet). We will also explore the advantages of gan and highlight the advantages of constructing such systems for residential solar applications。
Design attention for gan-based serial reversers
Figure 2 shows the 10kw single-phase reverser reference design, including all active and passive components, based on gan and with battery energy storage systems。
Figure 2 10kw single reference design based on the gan device
Figure 3 illustrates the rationale of the converter。
Figure 3 reference design box for single-string reversers figure
The reference design consists of four power conversion systems operating at different switch frequencies:
Two pressurizers for achieving two separate serial inputs with a rated power of 5 kw (134khz) per converter。
A two-way dc/dc converter with a rated power of 10kw (67khz)。
A two-way dc/ac converter with a rated power of 4. 6 kw (89khz)。
Power device
Thermal resistance is smaller than the bottom radiator because of the ability to disperse 30 m lmg3522r030 gan fet at the top with a rated voltage of 650v. These fets are integrated into a grid polar drive that reduces the cost of solutions and reduces design size。
Cmu
As shown in figure 3, the reference design is controlled by a single mmu. Tms320f28p550sj allows for real-time control of four power conversion stages, protection and multiple control loops. You can use the power source (gnd dc-) as a reference. Direct control of gan fet is also possible as a result of the integration of the grid's polar drive. There is no need at the bottom for isolation fence polar drivers (q1a, q1b, q2, q4, q6, q7)。
Electricity test
The system requires current measurement at different points at different converter levels. The voltage converter measures currents using a combination of solutions (e. G., the ina181 on negative power tracks) because the cmu uses the power source as a reference. In a staggered converter, you need to measure currents in batteries with high accuracy at different times and temperatures using high-precision current detection enhanced amplifier amc1302. Internal gan 5v voltage generated by low-pressure pressurers is used to power current detection amplifiers. In the reverse stage, the current of the grid can be measured using the hole effect current sensor (e. G. Tmcs 1123). This sensor has high bandwidth and high accuracy, which contributes to a significant reduction of current thd。
Test results
We run this reference design using the following system voltage:
Serial input voltage: 350v。
Name of battery voltage: 160v。
Network voltage: 230v。
Straight-link voltage: controlled at 400 v。
We collected the efficiency of the converters working in different settings:
Acquisition of electricity from serial inputs and transmission to the grid (see figure 4)。
Electricity is obtained from batteries and delivered to the grid (see figure 5)。
Power obtained from serial inputs and delivered to batteries (see figure 6)。
Figure 4 efficiency of pv output when converted to grid (350 vdc, 230 vac)
Figure 5 efficiency of electrical power output to the grid (160 vdc, 230 vac)
Figure 6 efficiency of pv panels when converted to batteries (350 vdc, 160 vdc)
These figures show that even if the switch speed is six times faster than the standard igbt solution, the overall efficiency is still comparable to the current igbt solution. When including auxiliary control power, efficiency remains around 98%. All three maps contain two power conversion stages。
Concluding remarks
Gan contributes to achieving higher power density, thereby reducing the weight of terminal equipment. The serial reverser reference design has a power density of nearly 98% overall system efficiency and 2. 3kw/l, showing superior performance. In addition, when considering the total cost of the system, the implementation of the integrated grid drive solution can reduce costs。
