Power conversion system and operation method for the same

A power conversion system for converting a direct-current-input voltage to an alternating-current-output voltage, the power conversion system comprising:

• a first-converting circuit configured to receive the direct-current-input voltage;
• a second-converting circuit connected to the first-converting circuit in parallel;
• a first filter circuit comprising a first output inductor, a second output inductor, and a first freewheeling inductor;
• a second filter circuit comprising a third output inductor, a fourth output inductor, and a second freewheeling inductor;
• a third filter circuit connected to one side of the second output inductor and one side of the fourth output inductor;
• and
• a control circuit configured to generate a plurality of control signals to separately control the first-converting circuit and the second-converting circuit,
• wherein the one side of the first output inductor is connected to the first-converting circuit;
• the other side of the first output inductor is connected to one side of the first freewheeling inductor and the other side of the second output inductor;
• the other side of the first freewheeling inductor is connected to the second-converting circuit;
• one side of the third output inductor is connected to the second-converting circuit;
• the other side of the third output inductor is connected to one side of the second freewheeling inductor and the other side of the fourth output inductor;
• the other side of the second freewheeling inductor is connected to the first-converting circuit, and wherein
• an inductance value of the second output inductor is greater than an inductance value of the first output inductor and an inductance value of the first freewheeling inductor;
• and an inductance value of the fourth output inductor is greater than an inductance value of the third output inductor and an inductance value of the second freewheeling inductor;
• wherein the first-converting circuit comprises a first branch, a second branch, and a first auxiliary branch, wherein the first auxiliary branch is connected between the first branch and the second branch;
• the other side of the fourth output inductor is connected to the first auxiliary branch through the second freewheeling inductor;
• wherein the second-converting circuit comprises a third branch, a fourth branch, and a second auxiliary branch, wherein the second auxiliary branch is connected between the third branch and the fourth branch;
• the other side of the second output inductor is connected to the second auxiliary branch through the first freewheeling inductor.

An operation method for a power conversion system to convert a direct-current-input voltage into an alternating-current-output voltage, the power conversion system comprising a first-converting circuit, a second-converting circuit, a first filter circuit and a second filter circuit, the first filter circuit comprising a first output inductor and a second output inductor, the second filter circuit comprising a third output inductor and a fourth output inductor;

• the first-converting circuit receives the direct-current-input voltage and comprises a first branch, a second branch, and a first auxiliary branch, wherein the first auxiliary branch is connected between the first branch and the second branch;
• the fourth output inductor is connected to the first auxiliary branch;
• the second-converting circuit is connected to the first-converting circuit in parallel and comprises a third branch, a fourth branch, and a second auxiliary branch, wherein the second auxiliary branch is connected between the third branch and the fourth branch;
• the second output inductor is connected to the second auxiliary branch;
• the operation method comprising:
• (a) when the alternating-current-output voltage is in a positive half cycle, the direct-current-input voltage being electrically connected to or disconnected to the first output inductor, the second output inductor, the alternating-current-output voltage and the fourth output inductor to form a positive half cycle energy storage loop, and when the direct-current-input voltage is disconnected, the first output inductor, the second output inductor, the alternating-current-output voltage and the fourth output inductor forming a positive half cycle energy release loop;
• (b) when the alternating-current-output voltage is in a negative half cycle, the direct-current-input voltage being electrically connected to or disconnected to the second output inductor, the alternating-current-output voltage, the fourth output inductor and the third output inductor to form a negative half cycle energy storage loop, and when the direct-current-input voltage is disconnected, the second output inductor, the alternating-current-output voltage, the fourth output inductor and the third output inductor forming a negative half cycle energy release loop;
• (c) when the alternating-current-output voltage is a positive half cycle reactive power, the alternating-current-output voltage, the second output inductor, the third output inductor and the fourth output inductor forming a positive half cycle reactive power loop;
• and
• (d) when the alternating-current-output voltage is a negative half cycle reactive power, the alternating-current-output voltage, the fourth output inductor, the first output inductor and the second output inductor forming a negative half cycle reactive power loop,
• wherein an inductance value of the second output inductor is greater than an inductance value of the first output inductor, and wherein an inductance value of the fourth output inductor is greater than an inductance value of the third output inductor.

An operation method for a power conversion system to convert a direct-current-input voltage into an alternating-current-output voltage, the power conversion system comprising a first-converting circuit, a second-converting circuit, a first filter circuit and a second filter circuit, the first filter circuit comprising a first output inductor, a second output inductor and a first freewheeling inductor, the second filter circuit comprising a third output inductor, a fourth output inductor and a second freewheeling inductor;

• the first-converting circuit receives the direct-current-input voltage and comprises a first branch, a second branch, and a first auxiliary branch, wherein the first auxiliary branch is connected between the first branch and the second branch;
• the fourth output inductor is connected to the first auxiliary branch through the second freewheeling inductor;
• the second-converting circuit is connected to the first-converting circuit in parallel and comprises a third branch, a fourth branch, and a second auxiliary branch, wherein the second auxiliary branch is connected between the third branch and the fourth branch;
• the second output inductor is connected to the second auxiliary branch through the first freewheeling inductor;
• the operation method comprising:
• (a) when the alternating-current-output voltage is in a positive half cycle, the direct-current-input voltage being electrically connected to or disconnected to the first output inductor, the second output inductor, the alternating-current-output voltage, the fourth output inductor and the second freewheeling inductor to form a positive half cycle energy storage loop, and when the direct-current-input voltage is disconnected, the first output inductor, the second output inductor, the alternating-current-output voltage, the fourth output inductor and the second freewheeling inductor forming a positive half cycle energy release loop;
• (b) when the alternating-current-output voltage is in a negative half cycle, the direct-current-input voltage being electrically connected to or disconnected to the first freewheeling inductor, the second output inductor, the alternating-current-output voltage, the third output inductor and the fourth output inductor to form a negative half cycle energy storage loop, and when the direct-current-input voltage is disconnected, the first freewheeling inductor, the second output inductor, the alternating-current-output voltage, the fourth output inductor and the third output inductor forming a negative half cycle energy release loop;
• (c) when the alternating-current-output voltage is a positive half cycle reactive power, the alternating-current-output voltage, the second output inductor, the first freewheeling inductor, the third output inductor and the fourth output inductor forming a positive half cycle reactive power loop;
• and
• (d) when the alternating-current-output voltage is a negative half cycle reactive power, the alternating-current-output voltage, the fourth output inductor, the second freewheeling inductor, the first output inductor and the second output inductor forming a negative half cycle reactive power loop,
• wherein an inductance value of the second output inductor is greater than an inductance value of the first output inductor and an inductance value of the first freewheeling inductor, and wherein an inductance value of the fourth output inductor is greater than an inductance value of the third output inductor and an inductance value of the second freewheeling inductor.