Inverter is a power electronic device, its main role is to convert direct current (DC) to alternating current (AC) power supply. Inverter is widely used in solar panel power system, wind power generation, UPS uninterruptible power supply, variable frequency air conditioning, electric vehicles and permanent magnet synchronous motor and other fields.
Inverter is composed of some semiconductor materials, capacitors, inductors and other electronic components, it is processed through the output of alternating current has high frequency and modulation wave, making it more suitable for some special loads and power equipment. The inverter can provide the required AC power when the power supply of the grid is unavailable, so as to ensure the continuous operation of some important power equipment.
First, the working principle of photovoltaic inverter
The inverter is mainly composed of switching components such as transistors, which turn the DC input into the AC output by repeatedly turning the switching components on and off regularly. Of course, such a pure inverter output waveform generated by the on and off loop is not practical. It is generally necessary to use high-frequency pulse width modulation to narrow the voltage width near the two ends of the sine wave and widen the voltage width in the center of the sine wave, and to always make the switching element act in a certain frequency direction in half a cycle, so as to form a pulse wave train. The pulse wave is then passed through a simple filter to form a sine wave.
Second, the role of photovoltaic inverter
Photovoltaic inverter not only has the function of direct AC conversion, but also has the function of maximizing the development of solar cell function and system fault maintenance function. It comes down to active operation and shutdown function, maximum power tracking control function, anti-independent operation function, active voltage adjustment function, DC detection function, DC ground detection function.
1, active operation and shutdown function
After sunrise in the morning, the intensity of solar radiation gradually increases, the output of solar cells also increases, when the output power required by the inverter task is reached, the inverter actively starts to operate, after entering the operation, the inverter will watch the output of the solar module every moment, as long as the output power of the solar module is greater than the output power required by the inverter task. The inverter continues to operate; Until sunset shut down, even in rainy days the inverter can run. When the output of the solar module becomes smaller and the output of the inverter is close to 0, the inverter constitutes a standby state.
2, maximum power tracking MPPT function
When the sunshine intensity and ambient temperature change, the input power of the photovoltaic module shows nonlinear changes, the photovoltaic module is neither a constant voltage source, nor a constant current source, its power changes with the output voltage change, and the load has no relationship. Its output current is initially a horizontal line as the voltage rises, when it reaches a certain power, it decreases as the voltage rises, and when it reaches the open circuit voltage of the component, the current drops to zero.
3. Detection and control of island effect
In normal power generation, the photovoltaic grid-connected power generation system is connected to the grid and delivers effective power to the grid, but when the grid loses power, the photovoltaic grid-connected power generation system may continue to work and operate independently of the local load, which is known as the island effect. When the inverter island effect, it will cause great security risks to personal safety, power grid operation, and the inverter itself, so the inverter access standard stipulates that the photovoltaic grid-connected inverter must have the detection and control function of the island effect.
4, power grid detection and grid connection function
Before the grid-connected inverter is connected to the grid, it needs to take power from the grid, detect the voltage, frequency, phase sequence and other parameters of the grid transmission, and then adjust the parameters of its own power generation to synchronize with the grid parameters, and it will be connected to the grid after completion.
5, low voltage through function
When a power system accident or disturbance causes a voltage dip in the voltage of the connecting point of the photovoltaic power station, within a certain voltage drop range and time interval, the photovoltaic power station can ensure continuous operation without off-grid.
Post time: Jan-16-2024