The traditional fuel energy is reduced day by day, the damage to the environment have become increasingly prominent, while there are 20 billion people worldwide lack of normal energy supply. This time around the world are casting their eyes on renewable energy, renewable energy want to change the human energy structure, maintain long-term sustainable development. Advantage of its unique solar energy become the focus of attention, more and more countries have begun to implement the “Sunshine”, the development of solar energy resources, a new driving force for economic development. Therefore, the study and design of inverter has broad prospects and significance. Limit of PV systems are two main factors: 1. The initial investment is relatively large; 2. Solar conversion efficiency of photovoltaic cells is low.
PV maximum power point output
When the PV array output voltage comparator hours, as the voltage changes, the output current change is small, the PV array similar to that for a constant current source; when the voltage exceeds a certain critical value continues to rise, the current sharp decline in the light at this time V array similar to a constant voltage source [2]. The output power of the photovoltaic array output voltage increases with a maximum output power point. Maximum power tracker is the role of temperature and radiation intensity in the changing environment, by changing the equivalent load carried by solar arrays, solar array operating point adjustment, so photovoltaic arrays maximum power point in the output of work.
MPPT control algorithm
Currently, the commonly used methods of maximum power tracking a constant voltage tracking, perturbation and observation method and the incremental conductance method. Among them, the conductance increment method of tracking accuracy of the highest in the case of rapidly changing environment, has a good tracking performance, it is widely used. Incremental conductance method is by comparing the instantaneous array of photovoltaic cells and immittance immittance approach to the completion of the change in the maximum power point tracking.
Maximum power point condition that the change in conductance when the output is equal to the output conductance of the negative, the photovoltaic cell array working at maximum power point. Changes in radiation intensity and temperature, the photovoltaic cell array can smooth the output voltage to follow changes in the environment, and the output voltage fluctuation is small [3].
Conductance increment method by setting the threshold of some very small changes, so that stable PV array maximum power point in the neighborhood, not around the maximum power point before and after the fluctuations. When the external environment changes, the transition from one state to another steady state, the conductivity changes according to the current increment method can make the right judgments, and there will not be as wrong as the perturbation and observation to determine.
Figure 3 U (k), I (k) is detected by the PV array current voltage, current, U (k-1), I (k-1) is on a cycle of voltage and current sample value .
Boost circuit photovoltaic array and phase, assuming that the external load is still purely resistive load, and ignore the Boost circuit impedance of the situation itself, according to the circuit impedance transformation between Boost, Boost circuit is easy to reach the equivalent input impedance Req = (1-D) 2R. D for the Boost circuit switching duty cycle, R is the impedance resistive load.
Array of photovoltaic maximum power tracking process, the control of voltage boost circuit is completed by Boost. The larger the duty cycle D, Boost smaller input impedance of the circuit, the duty cycle D more hours, Boost the greater the input impedance of the circuit. Boost circuit by changing the duty cycle D, the equivalent input impedance to match the impedance of PV output to achieve the maximum power output of photovoltaic cells, which is the use of Boost circuit to achieve maximum power tracking of the theoretical basis.
Maximum power tracking problem
Incremental conductance method using maximum power point tracking process, by adjusting the duty cycle to achieve the Boost circuit PV array operating point voltage control, so as to achieve maximum power tracking. However, photovoltaic cells by voltage / current curves and voltage / power curve can be seen working in the constant voltage source and constant current source is to change the voltage phase synchronous long the power output of photovoltaic cells to change is different. In the current source area, the output current changes in the sensitivity of the low operating voltage, while in the constant impact on the current source is obvious. In order to faster and more accurate tracking to maximum power output of photovoltaic cells working voltage and current, the need for improved methods of tracking.
How to calculate the maximum power of solar cells?
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The traditional fuel energy is reduced day by day, the damage to the environment have become increasingly prominent, while there are 20 billion people worldwide lack of normal energy supply. This time around the world are casting their eyes on renewable energy, renewable energy want to change the human energy structure, maintain long-term sustainable development. Advantage of its unique solar energy become the focus of attention, more and more countries have begun to implement the “Sunshine”, the development of solar energy resources, a new driving force for economic development. Therefore, the study and design of inverter has broad prospects and significance. Limit of PV systems are two main factors: 1. The initial investment is relatively large; 2. Solar conversion efficiency of photovoltaic cells is low.
PV maximum power point output
When the PV array output voltage comparator hours, as the voltage changes, the output current change is small, the PV array similar to that for a constant current source; when the voltage exceeds a certain critical value continues to rise, the current sharp decline in the light at this time V array similar to a constant voltage source [2]. The output power of the photovoltaic array output voltage increases with a maximum output power point. Maximum power tracker is the role of temperature and radiation intensity in the changing environment, by changing the equivalent load carried by solar arrays, solar array operating point adjustment, so photovoltaic arrays maximum power point in the output of work.
MPPT control algorithm
Currently, the commonly used methods of maximum power tracking a constant voltage tracking, perturbation and observation method and the incremental conductance method. Among them, the conductance increment method of tracking accuracy of the highest in the case of rapidly changing environment, has a good tracking performance, it is widely used. Incremental conductance method is by comparing the instantaneous array of photovoltaic cells and immittance immittance approach to the completion of the change in the maximum power point tracking.
Maximum power point condition that the change in conductance when the output is equal to the output conductance of the negative, the photovoltaic cell array working at maximum power point. Changes in radiation intensity and temperature, the photovoltaic cell array can smooth the output voltage to follow changes in the environment, and the output voltage fluctuation is small [3].
Conductance increment method by setting the threshold of some very small changes, so that stable PV array maximum power point in the neighborhood, not around the maximum power point before and after the fluctuations. When the external environment changes, the transition from one state to another steady state, the conductivity changes according to the current increment method can make the right judgments, and there will not be as wrong as the perturbation and observation to determine.
Figure 3 U (k), I (k) is detected by the PV array current voltage, current, U (k-1), I (k-1) is on a cycle of voltage and current sample value .
Boost circuit photovoltaic array and phase, assuming that the external load is still purely resistive load, and ignore the Boost circuit impedance of the situation itself, according to the circuit impedance transformation between Boost, Boost circuit is easy to reach the equivalent input impedance Req = (1-D) 2R. D for the Boost circuit switching duty cycle, R is the impedance resistive load.
Array of photovoltaic maximum power tracking process, the control of voltage boost circuit is completed by Boost. The larger the duty cycle D, Boost smaller input impedance of the circuit, the duty cycle D more hours, Boost the greater the input impedance of the circuit. Boost circuit by changing the duty cycle D, the equivalent input impedance to match the impedance of PV output to achieve the maximum power output of photovoltaic cells, which is the use of Boost circuit to achieve maximum power tracking of the theoretical basis.
Maximum power tracking problem
Incremental conductance method using maximum power point tracking process, by adjusting the duty cycle to achieve the Boost circuit PV array operating point voltage control, so as to achieve maximum power tracking. However, photovoltaic cells by voltage / current curves and voltage / power curve can be seen working in the constant voltage source and constant current source is to change the voltage phase synchronous long the power output of photovoltaic cells to change is different. In the current source area, the output current changes in the sensitivity of the low operating voltage, while in the constant impact on the current source is obvious. In order to faster and more accurate tracking to maximum power output of photovoltaic cells working voltage and current, the need for improved methods of tracking.