Photovoltaic inverter

This invention relates to a photovoltaic inverter, capable of connecting a plurality of photovoltaic modules to each input port of a multi-string photovoltaic inverter through a single booster. The photovoltaic inverter disclosed herein includes a plurality of input portions connected in series to a plurality of photovoltaic modules, respectively, a plurality of reactors connected in series to the plurality of input portions, respectively, a first capacitor configured to charge DC voltages of the plurality of photovoltaic modules, respectively, transferred through the plurality of input portions, a first resistor connected in parallel to the first capacitor, a booster unit connected in parallel to the first capacitor and the first resistor connected in parallel to each other, and configured to boost the voltages charged in the first capacitor, and an inverter unit configured to convert the voltage boosted by the booster unit into an AC voltage to provide to a grid.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0105043, filed on Sep. 2, 2013, the contents of which are all hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

This specification relates to a photovoltaic inverter, and particularly, to a photovoltaic inverter, capable of connecting a plurality of photovoltaic modules to an input port of a multi-string photovoltaic inverter through a single booster.

2. Background of the Disclosure

In general, a photovoltaic inverter (or a grid-connected inverter) is an electric power conversion system, namely, a system by which an input photovoltaic electric power grid and a commercial electric power grid are connected to each other so as to transmit the electric power of the input photovoltaic power grid to the commercial power grid.

A topology of the photovoltaic inverter may include a multi-string method.

The multi-string method refers to a method of receiving photovoltaic power inputs from two (or plural) photovoltaic modules. The multi-string method may be distinguished from the conventional method of receiving an input from a single photovoltaic module. In the photovoltaic inverter having type of multi-string, it is more efficient to connect two or more photovoltaic modules with the photovoltaic inverter than to connect a single photovoltaic module with the photovoltaic inverter.

However, the multi-string type photovoltaic inverter according to the conventional art should have a booster for each input port depending on the number of photovoltaic modules when connecting the plurality of photovoltaic modules to the single photovoltaic inverter, which may bring about an increase in fabricating costs of a product.

SUMMARY OF THE DISCLOSURE

Therefore, an aspect of the disclosure is to provide a photovoltaic inverter, capable of connecting a plurality of photovoltaic modules through a single booster to a multi-string type photovoltaic inverter, without employing a booster for each input port of the photovoltaic inverter.

To achieve these and other advantages and in accordance with the purpose of this disclosure, as embodied and broadly described herein, there is provided a photovoltaic inverter comprising:a plurality of input portions connected in series to a plurality of photovoltaic modules, respectively;a plurality of reactors connected in series to the plurality of input portions, respectively;a first capacitor configured to store DC voltages of the plurality of photovoltaic modules, respectively, transferred through the plurality of input portions;a first resistor connected in parallel to the first capacitor;a booster unit connected in parallel to the first capacitor and the first resistor connected in parallel to each other, and configured to boost the voltages charged in the first capacitor; andan inverter unit configured to convert the voltage boosted by the booster unit into an AC voltage to provide to a grid.

According to one aspect of this disclosure, the first capacitor is configured to charge (in other words “store”) an average value of the DC voltages of the plurality of photovoltaic modules.

According to another aspect of this disclosure, the first resistor is configured to consume the voltage charged in the first capacitor.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1is a block diagram illustrating a configuration of a photovoltaic inverter10in accordance with a preferred embodiment of this invention.

As illustrated inFIG. 1, a photovoltaic inverter10may include an input unit100, a reactor200, a first capacitor300, a first resistor400, a booster unit500and an inverter unit600. However, it will be understood that implementing all of the illustrated components of the photovoltaic inverter10illustrated inFIG. 1is not a requirement. Greater or fewer components may alternatively be implemented.

The input unit100, as illustrated inFIG. 2, may include a plurality of input portions, for example, a first input portion110, a second input portion120, . . . , and an Nthinput portion1N0.

Also, the plurality of input portions included in the input unit100may be connected to a plurality of photovoltaic modules in series, respectively.

For example, the first input portion110may receive a first DC voltage (or power/current/energy) transferred from a first photovoltaic module1connected thereto in series, and the second input portion (not shown) may receive a second DC voltage transferred from a second photovoltaic module (not shown) connected thereto in series. Here, the first DC voltage and the second DC voltage may have the same value or different values.

The reactor200may be provided as many as the number of the input portions included in the input unit100.

That is, the reactor200may include a plurality of reactors, for example, a first reactor210, a second reactor (not shown), . . . , and an Nthreactor2N0.

Also, the reactor200may be connected to the input unit100in parallel.

The first capacitor300may be connected to the reactor200(or the input unit100) in series.

The first capacitor300may store (in other words “charge”) DC voltages (in other words DC electric power or DC current or DC electric energy) of the plurality of photovoltaic modules (1-N), which are transferred through the input unit100. Here, the first capacitor300may charge (in other words “store”) an average value of the DC voltages of the plurality of photovoltaic modules (1-N).

For example, the first capacitor300may store an average value of the first DC voltage, which is transferred (in other words “outputted”) from the first photovoltaic module1through the first input portion110, and the second DC voltage, which is transferred from the second photovoltaic module through the second input portion.

The first resistor400may be connected in parallel to the reactor200and the first capacitor300.

Also, the first resistor400may consume the voltages charged in the first capacitor300.

That is, since a small quantity of currents flows through the first resistor400, the first resistor400may serve to facilitate the average value of the plurality of DC voltages to be charged in the first capacitor300.

The booster unit500may be connected in parallel to the first capacitor300and the first resistor400which are connected in parallel to each other.

The booster unit500, as illustrated inFIG. 2, may include a switch510, a diode520, and a second capacitor530.

The booster unit500may also raise (in other words “boost” or “increase”) the voltage charged in the first capacitor300.

The inverter unit600may convert the voltage (in other words “electric energy” or “a regulated DC electric power”) boosted by the booster unit500into an AC voltage (in other words “AC energy” or “AC electric power” or “3-phases AC electric power”), to provide (in other words “output”) to an electric power grid, such as an induction motor (not illustrated).

That is, the inverter unit600may receive the DC voltage (in other words “DC electric energy”) from each of the plurality of photovoltaic modules through the input unit100, convert the corresponding DC voltage into an AC voltage (in other words AC electric energy), and provide the converted AC voltage to the electric power grid.

The exemplary embodiment disclosed herein, as aforementioned, illustrates that the plurality of photovoltaic modules are connected through the single booster, without employing the booster for each input port of the multi-string photovoltaic inverter. This may result in a reduction of fabricating costs and a volume of the photovoltaic inverter.