Inverter system, method for controlling inverter system, and parallel inverter system

An inverter system, comprising:

• a pre-conversion circuit, a post-conversion circuit, and a control circuit, wherein:
• an input terminal of the pre-conversion circuit is configured to connect to a power supply, an output terminal of the pre-conversion circuit is connected to an input terminal of the post-conversion circuit, and a signal control terminal of the pre-conversion circuit is connected to an output terminal of the control circuit;
• an output terminal of the post-conversion circuit is configured to connect to an AC load, and a signal control terminal of the post-conversion circuit is connected to the output terminal of the control circuit;
• the pre-conversion circuit is configured to convert a voltage of the power supply into a DC voltage and output the DC voltage to the post-conversion circuit;
• the DC voltage between the pre-conversion circuit and the post-conversion circuit is a DC bus voltage;
• the post-conversion circuit is configured to convert the DC bus voltage into an AC voltage;
• the control circuit is configured to detect a DC component of the output terminal of the post-conversion circuit;
• the control circuit is configured to calculate a difference value of a zero value and the DC component to obtain a DC component deviation value, perform PI adjustment on the DC component deviation value to obtain a voltage compensation value, and adjust the DC bus voltage between the pre-conversion circuit and the post-conversion circuit according to a preset DC voltage reference value and the voltage compensation value;
• the control circuit comprises a pre-loop controller and a post-loop controller, and a signal terminal of the pre-loop controller and a signal terminal of the post-loop controller are communication connected through a serial port or a bus;
• the signal control terminal of the pre-conversion circuit is connected to an output terminal of the pre-loop controller, and the signal control terminal of the post-conversion circuit is connected to an output terminal of the post-loop controller;
• the pre-loop controller comprises a DC circulation control module, a first voltage loop, a first current loop, and a pre-PWM driving module;
• an input terminal of the DC circulation control module is connected to the post-loop controller, an input terminal of the first voltage loop is connected to an output terminal of the DC circulation control module, an input terminal of the first current loop is connected to an output terminal of the first voltage loop, an output terminal of the first current loop is connected to an input terminal of the pre-PWM driving module, and an output terminal of the pre-PWM driving module is connected to the signal control terminal of the pre-conversion circuit;
• the DC circulation control module is configured to obtain the DC component, calculate the difference value of the zero value and the DC component to obtain the DC component deviation value, and adjust the DC component deviation value through a preset PI adjustment coefficient to obtain the voltage compensation value;
• the first voltage loop is configured to calculate a corrected voltage value according to the preset DC voltage reference value and the voltage compensation value, and calculate a first voltage value according to a DC voltage value sampled at the output terminal of the pre-conversion circuit and the corrected voltage value;
• the first current loop is configured to calculate a pre-control signal quantity according to the first voltage value and a current value sampled in the pre-conversion circuit;
• and
• the pre-PWM driving module is configured to drive a switch transistor in the pre-conversion circuit according to the pre-control signal quantity to output the DC voltage.

A method for controlling an inverter system, the inverter system comprises a pre-conversion circuit, a post-conversion circuit, and a control circuit;

• an input terminal of the pre-conversion circuit is configured to connect to a power supply, an output terminal of the pre-conversion circuit is connected to an input terminal of the post-conversion circuit, and a signal control terminal of the pre-conversion circuit is connected to an output terminal of the control circuit;
• an output terminal of the post-conversion circuit is configured to connect to an AC load, and a signal control terminal of the post-conversion circuit is connected to the output terminal of the control circuit;
• the pre-conversion circuit is configured to convert a voltage of the power supply into a DC voltage and output the DC voltage to the post-conversion circuit;
• the DC voltage between the pre-conversion circuit and the post-conversion circuit is a DC bus voltage;
• the post-conversion circuit is configured to convert the DC bus voltage into an AC voltage;
• the control circuit implements a method as follows for inverter control, and the method comprises:
• detecting a DC component of the output terminal of the post-conversion circuit;
• calculating a difference value of a zero value and the DC component to obtain a DC component deviation value, and performing PI adjustment on the DC component deviation value to obtain a voltage compensation value;
• and
• adjusting the DC bus voltage between the pre-conversion circuit and the post-conversion circuit according to a preset DC voltage reference value and the voltage compensation value.

A parallel inverter system, comprising a plurality of inverter systems, wherein AC output terminals of the plurality of inverter systems are connected in parallel, and each of the inverter systems comprises a pre-conversion circuit, a post-conversion circuit, and a control circuit, wherein

• an input terminal of the pre-conversion circuit is configured to connect to a power supply, an output terminal of the pre-conversion circuit is connected to an input terminal of the post-conversion circuit, and a signal control terminal of the pre-conversion circuit is connected to an output terminal of the control circuit;
• an output terminal of the post-conversion circuit is configured to connect to an AC load, and a signal control terminal of the post-conversion circuit is connected to the output terminal of the control circuit;
• the pre-conversion circuit is configured to convert a voltage of the power supply into a DC voltage and output the DC voltage to the post-conversion circuit;
• the DC voltage between the pre-conversion circuit and the post-conversion circuit is a DC bus voltage;
• the post-conversion circuit is configured to convert the DC bus voltage into an AC voltage;
• the control circuit is configured to detect a DC component of the output terminal of the post-conversion circuit;
• and
• the control circuit is configured to calculate a difference value of a zero value and the DC component to obtain a DC component deviation value, perform PI adjustment on the DC component deviation value to obtain a voltage compensation value, and adjust the DC bus voltage between the pre-conversion circuit and the post-conversion circuit according to a preset DC voltage reference value and the voltage compensation value.