The three-phase primary control block generates the reference magnitudes (peak value) of the active and reactive components of current for the three-phase wave reference component to control the inverter's active and reactive power output. The primary active power control loop can generate the reference magnitude of the active power current component either in open loop condition, through a DC link voltage controller, or through an AC side closed-loop power control loop. Similarly, the primary reactive power control loop may generate the reference magnitude of reactive power current component in open-loop conditions or through an AC side closed-loop reactive power control loop. The input reference values for power quantities can be set directly to the desired value or they may be generated from the Secondary Control component.
Mask and Parameters
The configuration mask of the Primary Control block contains the following tabs:
- Rate Limiter
Primary Active Power Control Method
Select the primary active power control method of the inverter system: Open Loop, DC-Link, or Closed-Loop.
Primary Reactive Power Control Method
Select the primary reactive power control method of the inverter system: Open Loop or Closed Loop.
Current Limit (pu)
Maximum limit for the peak value of the inverter output current
Enable Rate Limiters
Select to apply rate limiters on DC-Link voltage, real and reactive power commands.
Enable Momentary Cessation (VRTm = 2)
Activate the input for the VRTm signal. This signal is generated by the Voltage Protection block. When VTRm = 2, the current reference is set to zero internally
Initial active power
Input initial active power
Initial reactive power
Input initial reactive power
Input sample time period
Proportional gain of the DC Link/active power/reactive power voltage PI controller.
Integral gain of the DC Link/active power/ reactive power voltage PI controller
Rate Limiter Tab
Maximum Increase Rate for Active Power/Reactive Power/DC-Link Voltage Reference
Limits the output active power and/or reactive power and/or DC Link voltage to the desired maximum increase rate.
Maximum Decrease Rate for Active Power/Reactive Power/DC-Link Voltage Reference
Limits the output active power and/or reactive power and/or DC Link voltage to the desired maximum decrease rate.
Inputs, Outputs and Signals Available for Monitoring
Reference value of active power (disabled when DC Link Control mode is activated)
Active power measurement
Reference value of reactive power (disabled when Closed Loop control is deactivated)
Reactive Power measurement (disabled when Closed Loop control is deactivated)
DC-link voltage reference (available in DC-Link control mode)
DC-link voltage measurement (available in DC-Link control mode)
Average of the RMS value of the three-phase grid voltages
Voltage ride-through input to enable momentary cessation (when VTRm = 2, the power reference is set to zero internally)
Signal used to reset the controller(s). When Reset = 1, the controller is reset
Signal that controls the output of the primary control block. When Disable = 1, the outputs are forced to 0
Peak value of the single-phase current component representing the real power (3x1 vector with identical values)
Peak value of the single-phase current component representing the reactive power (3x1 vector with identical values)
The following figure represents the schematic diagram of the inside of the primary control block:
The inputs of the primary control block are first passed through a signal conditioning subsystem, which limits the input power values inside the defined limits and limits the rate of change of the input voltage for DC link control.
Under the primary active control method, there are three different modes:
- Open-loop: When chosen, the active or reactive power reference signal is proportionally transformed into the reference active and/or reactive current components (Ipr or Iqr).
- DC-link: When chosen, a PI controller minimizes the error signal between the measured and reference DC link voltage to produce the reference active current component (Ipr).
- AC side (Closed-loop): When chosen, a PI controller minimizes the error signal between the measured and the reference active and/or reactive power to produce the reference active and/or reactive current components (Ipr and/or Iqr).
The active and reactive current component signals are passed through the rate limiters to limit their rate of increase/decrease for active power reference/reactive power reference/ DC link voltage reference.
The Primary Control block is intended to be used with balanced three-phase systems.
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