光伏储能系统关键设备之离网逆变器

高频逆变器应用场景

工频逆变器应用场景

古瑞瓦特高频隔离逆变器

古瑞瓦特工频隔离逆变器

离网逆变器的重要技术参数

5）切换时间：离网系统带负载，有光伏、蓄电池、市电三种模式，当蓄电池能量不足，切换到市电模式时，存在切换时间，有的离网逆变器采用电子开关切换，时间在10毫秒内，台式电脑不会关机，照明灯也不会闪烁。有的离网逆变器采用继电器切换，时间可能超过20毫秒，台式电脑可能会关机或者重启。

Modified wave and sine wave

Inverter output waveform is mainly divided into two categories, one is sine wave, the other is the correction wave. Repair sine wave inverter, using PWM pulse-width modulation to generate corrected wave output, due to the existence of about 20% harmonic distortion, can not take inductive load such as air conditioning, but can take resistive load such as lights. The repair sine wave inverter adopts the non - isolated coupling circuit, the device is simple and the efficiency is high. Pure sine wave inverter adopts isolated coupling circuit design, the circuit is more complex, high cost, can be connected to any common electrical equipment (including TV, LCD, especially the inductive load such as refrigerator) without interference.

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Power frequency isolation and high frequency isolation

Pure sine wave off-grid inverter input and output end has electrical isolation, according to the electrical structure is divided into high frequency isolation and power frequency isolation, high frequency isolation transformer in the DC boost end, the scheme is to first put the DC inverter high frequency alternating current, through the high frequency transformer boost, and then rectifier to DC, and finally inverter for power frequency alternating current, High frequency inverter is small volume, light weight of high frequency magnetic core material, can reduce the weight of the inverter, reduce the volume of the inverter, improve the efficiency of the inverter, but the circuit is more complex. The power frequency isolation transformer is placed in the AC end out of the end, the inverter circuit is simple, strong impact resistance, but the volume is larger, the weight is heavier.

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Application scenarios of high-frequency inverters

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Application scenario of power frequency inverter

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Guruwatt high frequency isolation inverter

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Agent Gureva has a frequency isolation inverter

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Split asanas versus uniasanas

Off-grid system due to more than a battery, so it must be configured with a controller, used for battery charging components, controller and inverter separate, make two devices, is split. The controller and inverter integrated together, is the integral, also known as the control inverter integral. Split system, controller and inverter can be selected separately, but the wiring is more complex, suitable for the component and inverter power difference is relatively large system, as well as the system power is very large. The integrated control inverter system has the advantages of simple structure, convenient connection, and is suitable for the system where the power difference between the component and the inverter is relatively small.

Important technical parameters of off-grid inverter

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In the selection of off-grid inverter, in addition to pay attention to the output waveform of the inverter, isolation type, there are several technical parameters are also very important, such as system voltage, output power, peak power, conversion efficiency, switching time and so on. The selection of these parameters has a greater impact on the power demand of the load.

1) System voltage: is the voltage of the battery. The input voltage of the off-grid inverter is consistent with the output voltage of the controller. In the design and selection, attention should be paid to keeping consistent with the controller.

2) Output power: The output power of off-grid inverter is expressed in two ways, one is apparent power representation, the unit is VA, this is a reference to the UPS label, the actual output active power needs to be multiplied by the power factor, such as 500VA off-grid inverter, the power factor is 0.8, the actual output active power is 400W, that is to say, can drive 400W resistance load, such as lights, Induction cooker, etc.; The second is active power representation, the unit is W, such as 5000W off-grid inverter, the actual output active power is 5000W.

3) Peak power: in the photovoltaic off-grid system, components, batteries, inverters and loads constitute the electrical system. The output power of the inverters is determined by the load. For some inductive loads, such as air conditioners and water pumps, the motor inside has a starting power 3-5 times of the rated power, so the off-grid inverters have special requirements for over-loading. Peak power is the overload capacity of the off-grid inverter.

The inverter provides the load with starting energy, part of which comes from the battery or photovoltaic module, and the excess part is provided by the energy storage components inside the inverter -- capacitors and inductors. Capacitors and inductors are both energy storage components. The difference is that capacitors store electric energy in the form of electric fields. The larger the capacity of capacitors, the more electricity they store. Inductors store energy in the form of magnetic fields. The larger the permeability of the inductor's magnetic core, the larger the inductance, and the more energy can be stored.

4) Conversion efficiency: off-grid system conversion efficiency includes two aspects, one is the efficiency of the machine itself, the off-grid inverter circuit is complex, after multistage transformation, so the overall efficiency is slightly lower than the grid-connected inverter, generally between 80-90%, the greater the inverter power efficiency is higher, high frequency isolation efficiency is higher than the power frequency isolation efficiency is higher, the higher the system voltage efficiency is higher. The second is the efficiency of battery charging and discharging. This is related to the type of battery. When photovoltaic power generation and load power consumption are synchronized, photovoltaic can directly supply the load, without the need for battery conversion.

5) Switching time: off-grid system with load, there are three modes of photovoltaic, battery, mains, when the battery energy is insufficient, switch to the mains mode, there is a switching time, some off-grid inverter using electronic switch, time within 10 milliseconds, desktop computer will not shut down, lights will not blink. Some off-grid inverters use relay switches that may take longer than 20 milliseconds, and the desktop computer may shut down or restart.