ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ПОБУТОВОЇ АВТОНОМНОЇ СОНЯЧНОЇ ЕЛЕКТРОСТАНЦІЇ ПОТУЖНІСТЮ 5 КВТ БЕЗ ОКРЕМОГО ЗАРЯДНОГО КОНВЕРТОРА

The assessment of the parameters of the power section of the converter as part of an autonomous PV plant installation with a rated power of 5000 W, designed to supply consumers with single-phase sinusoidal voltage of 220 V 50 Hz using a transformerless circuit is provided. The structure of the proposed PV plant differs from traditional structures. In the proposed structure, the DC voltage converter is connected with its input to the series connection of solar panels and performs the function of maximizing the output power and its output is connected to the DC link – the battery. The voltage-source inverter with sin pulse-width modulation is also connected to this link, its output voltage is the supply voltage of consumers. The minimum battery voltage is slightly higher than the output voltage amplitude of the DC/AC inverter. In this structure, unlike common systems with a 48V battery, there is no need for a separate bidirectional DC/DC converter with the functions of ensuring the coordination of the battery voltages and the internal DC voltage link (about 400 V, from which the voltage-source inverter is powered) and ensuring the charge – discharge of the battery with a set power from half the nominal power and above. The absence of a separate DC/DC converter simplifies the system and allows to significantly increase its efficiency in the battery load power supply mode. In the article evaluates the parameters of the PV plant of the proposed structure: the required number of serial solar panels with a nominal power of 500 W is determined, the use of a step-down DC-DC converter circuit is justified, its PWM frequency (25 kHz) is selected and the capacitance of the input storage capacitor is estimated. For the switches of the DC-DC converter, it is proposed to use modern field-effect transistors with an insulated gate and Schottky diodes based on silicon carbide (SiC); the types of semiconductor devices are selected and the power loss estimate in them (about 12 W) is provided. The required number of series-connected accumulator battery cells is determined. For the DC/AC inverter using the bridge circuit, the MOSFET type and the PWM frequency of 25 kHz are selected. The use of a three-level (unipolar) PWM algorithm is proposed, which allows doubling the output current ripple frequency. Estimates of power losses in the DC/AC inverter switches are provided: about 50 W. It is proposed to use a sendust ring core for the output filter choke, the choke parameters are determined, including an estimate of power losses: about 7 W. An estimate of the efficiency of an autonomous PV plant is provided: in the solar panel power mode 98.3% versus 97.6% for the analog and 98.8% when powered by an accumulator battery versus 94% for the analog, which corresponds to a reduction in power losses of 1.4 – 5 times.