Figure 2 dual flyback-type invertห้องสมุดไป่ตู้r
When it works,switch transistor Q1 and Q2 complementary conducts, and so do Q3 and Q4. And the drive signal of Q1 and Q4, Q2 and Q3 are the same. Also the model of transfer function is: V1 ND = Vdc 1 − D whereN is the variable ratio of the flyback transformer( N=n2/n1), and D isthe duty cycle of control signal. This circuit has two operational cycle, as shown inFigure 3 and Figure 4.
Figure 1 bidirectional flyback DC-DC converter
The relationship between input voltage and output voltage of a single inverter is: ������2 ������������ = ������1 1 − D where N is the variable ratio, and D is the duty cycle. The dual flyback-type inverter has two flyback DC-DC converters. The circuits of dual flyback-type PV inverter isasFigure 2.
2) Maximum Power Point Tracking(MPPT)
There is some ways to implement MPPT. These methods are used not only in flyback inverters, but in other kinds of inverters as well. perturbation and observation method:the controller adjusts the voltage by a small amount from the array and measures power; if the power increases, further adjustments in that direction are tried until power no longer increases. This is called the perturb and observe method and is
the Review of Dual-FlybackInverter
【Abstract】Along with the quick development of global economic, the world is facing energy crisis because of excessive traditional fossil energy consumption. Countries all over the world are devoting to development and utilization of new energy. Solar energy is resourceful, renewable, non-pollution and has become one of the most potential new energy. Moreover, solar photovoltaic (PV) power generation has got considerable development and become the mainstream of solar energy utilization based on the constant progress of solar cell and power electronic technique. In many kinds of solar PV configuration, solar AC module assembles single PV component and low power inverter and parallels with single-phase low voltage network. Thisconfiguration reduces power loss by shade sheltering of PV array and series connection of PV components, and realizes best fit of PV component and inverter easily. In this review, we will discuss the dual flyback-type inverter, namely the principle, the MPPT, , the advantages and the disadvantages of it. 【Key Word】 PV micro-inverter; dualflyback-type inverter; Maximum power point tracking; Voltage stress.
2. Principles
The basic structure of the dual flyback-type inverter is bidirectional flyback DC-DC converter, as Figure 1.Assume that V1 is the primary voltage, and V2 is the secondary voltage. S1 and S3 complementary conducts.The flyback transformer can transmit energy form the primary side to the secondary side just when S1 shutdowns and S3 conducts.
most common, although this method can result in oscillations of power output. Incremental conductance method: In the incremental conductance method, the controller measures incremental changes in array current and voltage to predict the effect of a voltage change. This method requires more computation in the controller, but can track changing conditions more rapidly than the perturb and observe method. Constant voltage:In the constant voltage method, the power delivered to the load is momentarily interrupted and the open-circuit voltage with zero current is measured. The controller then resumes operation with the voltage controlled at a fixed ratioof the open-circuit voltage, which has empirically been determined as the estimated maximum power point.The operating point of the PV array is kept near the MPP by regulating the array voltage and matching it to a fixed reference voltage Vref. The Vref value is set equal to the maximum power point voltage of the characteristic PV module or to another calculated best fixed voltage.
VQ2max = VQ3max =
Since the voltage of grid is always higher than the output voltage of PV, Q1 and Q4 will bear high voltage, while Q2 and Q3 will bear low voltage. Sometimes the voltage stress of Q1 and Q4 can be a restriction.
Figure 3 dual flyback circuit-model 1
Figure 4 dual flyback circuit-model 2
3. Hot topics 1) Voltage Stress
The voltage stress of this circuit is: VQ1max = VQ4max = Dmax 2Vgrid 2Dmax − 1 1 V 1 − Dmax dc
simple structure and easily controlled function. In this Review, we willmainly discuss the topology of dual-flyback type PV inverter, and the principle, hot topics such as MPPT, the advantages and disadvantages, and its comparisons with other circuits will be referenced.