Power quality compensation system and control method with bus voltage and current peak control

A control method for a power quality compensation system, the power quality compensation system being electrically coupled with a power grid and a nonlinear load, the power quality compensation system comprising a first peak current processing unit, a current control unit, a current threshold adjustment unit, a conversion unit, a second peak current processing unit, a subtractor, a voltage loop control unit, a third peak current processing unit and a driving circuit, the current threshold adjustment unit being electrically coupled between the first peak current processing unit and the second peak current processing unit, the first peak current processing unit being electrically coupled with the current control unit, the second peak current processing unit being electrically coupled with the conversion unit, the subtractor being electrically coupled between the conversion unit and the current threshold adjustment unit, the voltage loop control unit being electrically coupled between the subtractor and the current control unit, the third peak current processing unit being electrically coupled with the conversion unit, the driving circuit being electrically coupled with the current control unit, the second peak current processing unit, the third peak current processing unit and the conversion unit, the control method comprising steps of:

• S1:
• receiving a first instruction current and a first current threshold value, and outputting an instantaneous current instruction according to the first instruction current and the first current threshold value by the first peak current processing unit, wherein the instantaneous current instruction indicates that the first instruction current under control of the first peak current processing unit is lower than or equal to the first current threshold value;
• S2:
• outputting a first PWM driving signal according to the instantaneous current instruction and a second instruction current by the current control unit;
• S3:
• receiving a first comparison value and a second comparison value or receiving the second instruction current and the second comparison value, and outputting the first current threshold value by the current threshold adjustment unit, wherein the first current threshold value is dynamically adjusted;
• S4:
• receiving a sampled current and a second current threshold value, and outputting a second PWM driving signal and the second comparison value by the second peak current processing unit;
• S5:
• outputting an output current and a real DC bus voltage according to a main driving signal by the conversion unit;
• S6:
• receiving the real DC bus voltage and a reference DC bus voltage, and outputting the first comparison value by the subtractor;
• S7:
• receiving the first comparison value, and outputting the second instruction current by the voltage loop control unit;
• S8:
• receiving the sampled current and a third current threshold value, and outputting a third PWM driving signal according to a result of comparing the sampled current with a third current threshold value by the third peak current processing unit;
• and
• S9:
• receiving the first PWM driving signal, the second PWM driving signal and the third PWM driving signal, and outputting the main driving signal to the conversion unit by the driving circuit.