General distributed control method for multi-microgrids with PQ control and droop control

• US 10,644,506 B2
• Filed: 12/16/2016
• Issued: 05/05/2020
• Est. Priority Date: 09/27/2016
• Status: Active Grant

• Current Assignee: Southeast University
• Original Assignee: Southeast University
• Inventors: Gu, Wei, Cao, Ge, Liu, Wei, Wu, Zhi, Zhou, Suyang, Lou, Guannan
• Primary Examiner(s): Lee, James J
• Assistant Examiner(s): Choi, Michael W
• Application Number:
  US15/763,733
• Publication Number:
  US 20190074691A1
• Time in Patent Office: 1,236 Days
• Field of Search: 700287
• CPC Class Codes: G05B 17/02 electric
• CPC Class Codes: H02J 2310/10 The network having a local or delimited stationary reach
• CPC Class Codes: H02J 3/06 Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
• CPC Class Codes: H02J 3/381 Dispersed generators

Abstract

The invention discloses a general distributed control method for multi-microgrids with both PQ controlled and droop controlled distributed generators, which comprises the following steps of: step 10) conducting primary control to maintain the power balance of the multi-microgrids; step 20) determining predefined group consensus values of pinned agents; step 30) seeking group consensus among other agents and the pinned agents through communication coupling; and step 40) adjusting output powers to complete secondary control. Based on pinning control, the control method which adopts hierarchical control is a distributed control method for distributed power supply clusters with two control modes comprising PQ control and droop control. The method obviates the requirements for a central controller and complex communication topologies, reduces the number of the controllers, can be adapted to the communication topology changes in the multi-microgrids, and meets the plug-and-play requirement for the distributed power supply.

Claims

1. A general distributed control method for multi-microgrids with PQ control and droop control, wherein the multi-microgrids comprise m droop-controlled distributed power supply clusters and n PQ-controlled distributed power supply clusters;

a multi-agent system is responsible for the control and mutual information interaction of the distributed power supplies in the multi-microgrids, each distributed power supply is corresponding to one agent, and the number of the distributed power supplies is the same as the number of the agents corresponding to the distributed power supplies;

wherein, part of the agents are pinned and controlled, while other agents are tracked and synchronized in a distributed manner through communication coupling with the pinned agents; and

the control method comprises the following steps of;

step

     10) conducting primary control to maintain the power balance of the multi-microgrids;

step

     20) determining predefined group consensus values of the pinned agents;

wherein specifically comprises;

determining the predefined group consensus values of the pinned agents under uncertain communication topologies, which comprises the pre-defined group consensus values of the droop-controlled pinned agents and the pre-defined group consensus values of the PQ-controlled pinned agents;

determining the distribution coefficients of the droop-controlled distributed power supply clusters according to formula (2);

2. The general distributed control method for multi-microgrids with PQ control and droop control according to claim 1, wherein the step 10) specifically comprises:

automatically conducting primary control as shown in formula (1) by the droop-controlled distributed power supply clusters when the multi-microgrids are disturbed in an islanded mode, and operating the droop-controlled distributed power supplies in a peer-to-peer control mode to maintain the power balance of the multi-microgrids;

f_i=f_n,i−

m_P,i(P_i−

P_0,i)

U_i=U_n,i−

n_Q,i(Q_i−

Q_0,i) 

 

formula (1)

where, f_i indicates the frequency of the i-th droop-controlled distributed power supply, f_n,i indicates the initial value of the frequency of the i-th droop-controlled distributed power supply, m_P,i indicates the active droop coefficient of the i-th droop-controlled distributed power supply, P_i indicates the active power outputted by the i-th droop-controlled distributed power supply, P_0,i indicates the initial value of the active power of the i-th droop-controlled distributed power supply, and U_i indicates the voltage of the i-th droop-controlled distributed power supply;

U_n,i indicates the reference value of the i-th droop-controlled distributed power supply;

n_Q,i indicates the reactive droop coefficient of the i-th droop-controlled distributed power supply;

Q_i indicates the reactive power outputted by the i-th droop-controlled distributed power supply; and

Q_0,i indicates the initial value of the reactive power of the i-th droop-controlled distributed power supply.

3. The general distributed control method for multi-microgrids with PQ control and droop control according to claim 1, wherein the step 30) specifically comprises:

tracking and synchronizing other agents in and among the distributed power supply clusters with the pinned agents through pinning control, so as to seek and reach the pre-defined group consensus;

determining the control error e_fUk,i of the i-th droop-controlled distributed power supply agent according to formula (6);

4. The general distributed control method for multi-microgrids with PQ control and droop control according to claim 1, wherein the step 40) specifically comprises:

adjusting an output power by each distributed power supply agent according to the pre-defined group consensus values reached and based on the PQ-controlled distributed power supplies, and recovering the system frequency and voltage based on the droop-controlled distributed power supplies, so as to complete the secondary control over the multi-microgrids together;

conducting the secondary control over the droop-controlled distributed power supply agent i according to formula (10);

f_n,i^S=f_n,iΔ

f_n,i

U_n,i^S=U_n,i+Δ

U_n,i 

 

formula (10)

where, f_n,i^S indicates the reference frequency value of the droop-controlled distributed power supply agent i adjusted through the secondary control, f_n,i indicates the reference frequency value of the droop-controlled distributed power supply agent i in the primary control, Δ

f_n,i indicates the frequency correction of the droop-controlled distributed power supply agent i in the secondary control, U_n,i^S indicates the reference voltage value of the droop-controlled distributed power supply agent i adjusted through the secondary control, U_n,i indicates the reference voltage value of the droop-controlled distributed power supply agent i in the primary control, and Δ

U_n,i indicates the voltage correction of the droop-controlled distributed power supply agent i in the secondary control; and

conducting the secondary control over the PQ-controlled distributed power supply agent i according to formula (11);

P_ref,i^S=P_ref,i+Δ

P_ref,i

Q_ref,i^S=Q_ref,i+Δ

Q_ref,i 

 

formula (11)

where, P_ref,I^S indicates the active reference value of the PQ-controlled distributed power supply agent i adjusted through the secondary control, P_ref,i indicates the initial active reference value of the PQ-controlled distributed power supply agent i, Δ

P_ref,i indicates the active power correction of the PQ-controlled distributed power supply agent i in the secondary control, Q_ref,i^S indicates the reactive reference value of the PQ-controlled distributed power supply agent i adjusted through the secondary control, Q_ref,i indicates the initial reactive reference value of the PQ-controlled distributed power supply agent i, and Δ

Q_ref,I indicates the reactive power correction of the PQ-controlled distributed power supply agent i in secondary control.