PQ CONSTANT mode diesel dg

Overview
This document describes GridLAB-D implementation of diesel generator in PQ constant mode.

A constant_P mode is implemented in the governor type P_CONSTANT: In the constant_P mode, a time delay is applied to the electric power output from the diesel generator. The delayed electric power output is compared with the constant real power reference, then applied to a PI controller, to get the actuator input. The actuator part and time delay part of the GGOV01 governor is used in constant_P mode. Output of the constant_P mode is the mechanical power of the diesel generator.

The constant_Q mode is implemented based on the existing exciter SEX_PTI:

Diesel Generator in PQ Constant mode example
This diesel generator object is implemented in both constant P and constant Q mode.

By selecting Governor_type as P_CONSTANT, the constant P mode is selected. This example sets Pref value as 0.5 p.u. The PI controller settings for the constant Pref mode are 0 for proportional control, and 0.05 for integral control. In addition, parameters of the actuator and time delay part of the P_CONSTANT are also defined in the example.

By selecting Exciter_Q_constant_mode as true, the constant Q mode is selected. This example sets Qref value as 0.6 p.u.. The PI controller settings for the constant Q mode are 0.01 for proportional control, and 0.05 for integral control.

Example of Diesel Generator in PQ Constant mode
module generators; object diesel_dg { flags DELTAMODE; parent 8; name Gen2; Rated_V 4156; //Line-to-Line value Rated_VA 1000000; // Defaults to 10 MVA Gen_type DYN_SYNCHRONOUS; rotor_speed_convergence ${rotor_convergence}; Exciter_type SEXS; Governor_type P_CONSTANT; // Actuator and time delay parameters for P_CONSTANT mode P_CONSTANT_Tpelec 1.0; // Electrical power transducer time constant, sec. (>0.) P_CONSTANT_Tact 0.05; //0.5; // Actuator time constant P_CONSTANT_Kturb 1.5; // Turbine gain (>0.) P_CONSTANT_wfnl 0.2; //0.2; // No load fuel flow, p.u     P_CONSTANT_Tb 0.01;//0.1; // Turbine lag time constant, sec. (>0.) P_CONSTANT_Tc 0.2; // Turbine lead time constant, sec.     P_CONSTANT_Teng 0.0; // Transport lag time constant for diesel engine P_CONSTANT_ropen 050; // Maximum valve opening rate, p.u./sec. P_CONSTANT_rclose -050; // Minimum valve closing rate, p.u./sec. P_CONSTANT_Kimw 0.0;//0.002; // Power controller (reset) gain inertia 2.5; // PI controller parameters of P_CONSTANT mode P_CONSTANT_Pref 0.5; // Set P reference, p.u.      P_CONSTANT_kp 0;  // ki for the PI controller implemented in P constant delta mode P_CONSTANT_ki 0.05; // kp for the PI controller implemented in P constant delta mode Exciter_Q_constant_Qref 0.6; // Set Q reference, p.u.      Exciter_Q_constant_mode true; // Flag indicating whether the diesel generator exciter is operating based on Qref given Exciter_Q_constant_kp 0.01; // ki for the PI controller implemented in Q constant delta mode }

Properties
This table lists the properties related to diesel generator in PQ constant mode. Some parameters used by diesel_dg can be found in the diesel_dg wiki page.

Test cases
In order to verify the implementation of PQ_CONSTANT mode diesel generator, a test case in 123-bus feeder with one isochronous mode diesel_dg Gen 1, and one PQ_CONSTANT mode diesel_dg Gen 2is applied. At 5.001 second, part of the feeder is disconnected. Gen 1 will reduce its generation, and Gen 2 will maintain its generation after the transient. Below diagram shows the generation from the two generators before and after the transient. To run this case, please find in the autotest in GridLAB-D generator module.