Abstract
This paper presents a modular grid-connected single-phase system based on series-connected current-source module integrated converters (MICs). The modular configuration improves the reliability, redundancy and scalability of photovoltaic (PV) distributed generators. In this system, each PV panel is connected to a dc/ac inverter to permit individual Maximum Power Point Tracking (MPPT) operation for each panel. Thus, the harvested power from the PV system will increase significantly. There are four different inverter topologies suitable to be used as MICs with different performances in terms of filtering elements size, power losses, efficiency, output voltage range, and high frequency transformers’ size. For the MPPT control, the oscillating even order harmonic components should be eliminated from the inverter’s input side otherwise the maximum power cannot be extracted. The proposed modulation scheme in this paper will ease the control of inverter’s input and output sides. Therefore, the 2nd order harmonic in the input current can be eliminated without adding new active semiconductor switches. A repetitive controller coupled with proportional-resonant controllers are employed to achieve accurate tracking for grid side as well as input side currents. Comparisons and performance evaluations for the proposed MICs are presented and validated with 1 kVA prototype controlled by TMS320F29335 DSP.
Highlights
The remarkable development in the installed capacity of distributed generators (DGs) increases the international aspiration for improving the performance of power inverters employed in renewable energy systems (RESs) such as photovoltaic (PV) systems [1]
This paper proposes modified modulation schemes for the single-phase inverters in Fig. 3 where the output bridge switches are operated independently with respect to the input side to provide an additional degree of freedom
The rectified voltage is generated across C3 with controlling the input switch S1 and this voltage is directed to the output load using the bridge switches S2 → S5
Summary
The remarkable development in the installed capacity of distributed generators (DGs) increases the international aspiration for improving the performance of power inverters employed in renewable energy systems (RESs) such as photovoltaic (PV) systems [1]. These four inverter modules can be employed in the modular PV system in Fig. 1b provided that the input power is decoupled from output. This paper proposes modified modulation schemes for the single-phase inverters in Fig. 3 where the output bridge switches are operated independently with respect to the input side to provide an additional degree of freedom. In this way, both input and output sides’ currents can be controlled together and the even harmonics in the input currents will be eliminated and the MPPT controller will be able to maximise the output power of the system.
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