power inverter

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How to choose solar inverter power electronics

Solar photovoltaic systems and more extensive applications. Especially mobile system, without having to spend a penny, to benefit from solar energy. And because of the rising cost of conventional energy, solar energy for home applications has great appeal. Solar cell itself and the connection with the public grid or solar power solar inverter distribution of energy efficiency, this technology is the key to success lies. Today, the maximum output power of 5kW advanced solar inverter has two topologies. Figure 1 shows such a plurality of sets of solar inverter configuration.

Solar inverter multi-group configuration

Each group and its own power regulator connector, and then connect to a shared DC bus. Power adjuster to make working with maximum efficiency of solar cells. Solar inverter generates AC voltage electricity fed into the market. Note that Figure 1 shows a power supply network can be used for any dummy SUNGOLDPOWER inverter circuit topology, plus a mains transformer and an output filter, the transformer can prevent the DC component into the mains.

However, there are some systems that do not have a transformer, depending on the solar inverter sales law of the country background. Do not use a transformer to allow countries aims to improve the efficiency of the system, because the transformer causes reduced efficiency of 1 to 2 percentage points. On the other hand,
Inverter DC component necessary to avoid requiring current is less than 5mA. Although this is difficult to do, but in order to obtain higher efficiency, we successfully achieved. Table 1 shows the loss of each level of the system, the system size and system cost value of the contribution.

Every one pair of system losses, system size and value of the contribution system cost


It is easy to see that, the transformer system is a major contributor to loss and cost. However, the transformer must be used in many countries, and therefore, it does not reduce losses within the scope of consideration. Output filter can be reduced by the output current generated by the inverter stage ripple, the filter size and cost of the inverter switching frequency is inversely proportional. Higher the switching frequency, the smaller the filter size, the lower the price. However, this relationship is a hard transition state switching frequency and switching losses under the relationship between the formation of a compromise - the higher the switching frequency, the greater the loss, so the lower the efficiency. From 16kHz ~ 20kHz switching frequency, due to its low audio noise and high efficiency solar inverters meet the requirements. Therefore, the power circuit also needs further study.

The following applies to these two will compare several semiconductor technology advantages.

For DC TO AC converter power semiconductors boost

DC / DC converter is at 100kHz switching frequency and above running under. Converter running in continuous mode, which means that the boost inductor current at rated conditions will produce a continuous waveform. When the transistor is turned off, the diode is used as a freewheeling diode, transistor may be charged for the inductor. That is, when the transistor is turned on again, the diode can be active close. The following figure shows a typical common silicon diode reverse recovery characteristics (Figure 2 black and red curve).

Common silicon diode reverse recovery characteristics typical


Silicon diode reverse recovery characteristics, the boost transistors and the corresponding diode will produce higher loss. The SiC diode would be no problem (blue curve shown in Figure 2). Only because of capacitive diode produces a transient negative current, which is charged by the diode junction capacitance caused. SiC diodes can greatly reduce the transistor turn-on losses and diode turn-off losses, and can reduce electromagnetic interference, because the waveform is very smooth, no oscillation.

Many have reported previously avoided by the diode reverse recovery characteristics result in loss processes, such as zero-voltage switching zero current switch. All of which significantly increased the number of components and complexity of the system, often results in the decreased stability. It is particularly worth mentioning is that even in hard switching mode by using silicon carbide Schottky diode can also be used a minimum of components to achieve soft switching the same efficiency.

The high switching frequency also requires high-performance boost transistor. Super-junction transistors (such as CoolMOS) the introduction, in order to further reduce the MOSFET's on-resistance per unit area of RDS (on) brings hope,
  1. 2013/08/05(月) 10:30:24|
  2. DC TO AC
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