A Control Method of Droop Coefficient of Bidirectional DC/DC Variation in Microgrid

Abstract

The invention discloses a control method of a micro-grid bidirectional DC / DC (Direct Current / Direct Current) change drooping coefficient. The method comprises the following steps: detecting direct current bus voltage Udc and direct current bus current Idc on an output side; inputting the Udc, the Idc, a direct current bus voltage set value Udc<*> and a drooping coefficient initial value k0 into a direct current bus drooping controller; comparing the direct current bus voltage Udc with the direct current bus voltage set value Udc<*> to determine a DC / DC working region and regulating the drooping coefficient of each region; calculating a DC / DC output voltage reference value Udc-ref; transmitting a difference value of the DC / DC output voltage reference value Udc-ref and the direct current bus voltage Udc into a direct current voltage PI (Proportional Integral) regulator, and outputting a given value Idc<*> of a current ring; comparing the Idc<*> with the direct current bus current Idc, inputting the difference value into the direct current PI regulator, and taking the output as a given value of PWM (Pulse Width Modulation); generating PWM wave for controlling switch-on and switch-off of an IGBT (Insulated Gate Bipolar Transistor) to realize constant voltage control of DC / DC. The problem that the DC / DC output power cannot be regulated on line in the drooping control is effectively solved, the dynamic performance and the steady state performance of a direct current converging system are improved, and loop current between energy storage units is reduced.

Description

technical field [0001] The invention relates to a control method, in particular to a control method for a microgrid bidirectional DC / DC change droop coefficient. Background technique [0002] With the depletion of global fossil energy supply and the severe climate situation, all countries in the world have realized the importance of developing new energy sources. It is estimated that in 2014, the new installed capacity of photovoltaics in the world will reach 43GW, my country will reach 14GW, and distributed power generation will be about 8GW. [0003] Most of the new energy power generation adopts the AC collection scheme, that is, the new energy power generation is collected into the low-voltage AC bus through power electronic equipment, and finally connected to the AC distribution network through the step-up transformer. However, there are the following problems with this scheme: (1) During the process of converting the DC voltage of new energy power generation into AC v...

AI Technical Summary

Problems solved by technology

[0007] In order to overcome the above defects, the present invention proposes a microgrid bidirectional DC / DC variable droop coefficient control method, which adopts a variable coefficient droop control strategy to keep the bus voltage constant; on the basis of traditional droop control, according to the bus voltage deviation and energy storage The system's own capacity continuously adjusts the droop coefficient. When the bus voltage deviation is small, that is, the power flow in the system is small, the droop coefficient is increased to improve the system dynamic performance. When the bus voltage deviation is large, that is, the power flow in the system is large, the droop control coefficient is reduced. To reduce the bus voltage deviation; through the adjustment of the droop coefficient of each energy storage unit to control its charge and discharge power, to improve the utilization rate of each energy storage unit, so that the whole system can run safely and stably for a long time; effectively solve the droop control The problem that the DC / DC output power cannot be adjusted online improves the dynamic performance and steady-state performance of the DC collection system and reduces the circulation between energy storage units

Images