Generator Line Drop and Reactive Current Compensation

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Note: This feature has been available since early versions of PowerWorld Simulator using only XLDC_RCC. The availability of RLDC_RCC was Added in Version 19.

Line Drop and Reactive Current Compensation represent an alternative method for performing generator voltage control. These options can be set through fields associated with the generator display and a special display exists with contingency analysis options that brings up these fields by default. The fields that must be modified to use line drop or reactive current compensation are Use LDC_RCC, XLDC_RCC, RLDC_RCC,and AVR. These will be described below.

While on LDC/RCC control, the generator will vary its MVAR output in a manner that maintains the bus voltage at a fictitious bus that is a user-specified electrical impedance of XLDC_RCC away from the generator. This is called Line Drop Compensation when the impedance specified is positive, and Reactive Current Drop Compensation when the impedance specified is negative. If the absolute value of XLDC_RCC is less than or equal to 2*10-6*MVA Base, the generator will regulate its terminal bus. (For a typical case with an MVA Base of 100 MVA, this value is 0.0002.)

The impedance is specified by entering a value for XLDC_RCC, RLDC_RCC,and the setpoint voltage is the same as used when regulating a generator in the more traditional manner. A generator will perform LDC/RCC control when it meets the following conditions:

If any generators at a bus are set to Use LDC_RCC, this action will disable all traditional AVR control for generators at that bus. Other generators operating on LDC/RCC control are allowed, but no traditional AVR.

When using LDC/RCC control with contingency analysis where this should only be used in the contingency solution, the field Use LDC_RCC must be set to PostCTG. When a generator is set to PostCTG while implementing the post-contingency power flow, the generator will change the Use LDC_RCC value to YESand set AVR to YES, thereby activating this new voltage control method for the generator. The AVR setting is also set to YES because the intent of using the PostCTG option is to force the generator to operate on LDC/RCC during the contingency solution. The AVR flag must be YES for a generator to be on any kind of AVR control, so this is a necessary change. After the reference state is restored in the contingency analysis, the generator will return back to a setting of PostCTGand its reference state AVR setting.

There is an option on the local menu of the generator display, Convert Voltage Setpoint for LDC_RCC, that will set the voltage setpoint of the selected generator(s) based on the specified XLDC_RCC and RLDC_RCC,. The voltage at the fictitious bus that is the specified impedance from the generator will be calculated and this is set at the setpoint voltage. If the impedance is less than the threshold specified above, the setpoint will be set to the voltage of the terminal bus. The Use LDC_RCC field will be set to YES.