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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 the 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:

• Configuration

• Controller

• Rate Limiter

Configuration Tab

Open

Controller Tab

Rate Limiter Tab

Inputs, Outputs, and Signals Available for Monitoring

Inputs

Outputs

Description

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:

1. 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).

2. 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).

3. 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.

Limitations

The Primary Control block is intended to be used with balanced three-phase systems.

References

• T. Krein, J. Bentsman, R. M. Bass and B. L. Lesieutre, “On the Use of Averaging for the Analysis of Power Electronics Systems,” IEEE Transactions on Power Electronics, vol. 5, pp. 182–190, Apr 1990.

• Timbus, M. Liserre, R. Teodorescu, P. Rodriguez and F. Blaabjerg, “Evaluation of Current Controllers for Distributed Power Generation Systems,” IEEE Transactions on Power Electronics, vol. 24, no. 3, pp. 654–664, Mar 2009.

• IEEE Std. 1547-2003, IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems, 2003.

• A. Ninad and L. A. C. Lopes, “A Low Power Utility Interactive Inverter for Residential PV generation with Small DC Link Capacitor,” in Proceeding of 3rd Canadian Solar Building Conference, Fredericton, Canada, pp. 28-36, Augt 2008.

• Bower and M. Ropp, “Evaluation of Islanding Detection Methods for Utility-Interactive Inverters in Photovoltaic Systems” SANDIA Report SAND2002-3591, Albuquerque, NM: Sandia National Labs, Nov 2002.

• Ye, A. Kolwalkar, Y. Zhang, P. Du and R. Walling, “Evaluation of Anti-islanding Schemes Based on Non-detection Zone Concept,” IEEE Transactions on Power Electronics, vol. 19, no. 5, pp. 1171–1176, Sep 2004.

• Ropp, M. Begovic and A. Rohatgi, “Analysis and Performance Assessment of the Active Frequency Drift Method of Islanding Prevention,” IEEE Transaction on Energy Conversion, vol. 14, no. 3, pp. 810–816, Sep1999.

• A. C. Lopes and H. Sun, “Performance Assessment of Active Frequency Drifting Islanding Detection Methods,” IEEE Transactions on Energy Conversion, vol. 21, no. 1, pp. 171–180, Mar 2006 .

• Ye, R. Walling, L. Garces, R. Zhou, L. Li and T. Wang, “Study and Development of Anti-Islanding Control for Grid-Connected Inverters,” Report NREL/SR-560-36243, Golden, CO: National Renewable Energy Laboratory, May 2004.

• Yafaoui, B. Wu, and S. Kouro, “Improved Active Frequency Drift Anti-islanding Detection Method for Grid Connected Photovoltaic Systems,” IEEE Transactions on Power Electronics, vol. 27, no. 5, pp. 2367-2375, May 2012.

• Stevens, R. Bonn, J. Ginn, S. Gonzalez and G. Kern, “Development and Testing of an Approach to Anti-Islanding in Utility-Interconnected Photovoltaic Systems,” Sandia National Laboratories, Tech. Rep. SAND2000-1939, Aug 2000.

• Mulhausen, J. Schaefer, M. Mynam, A. Guzman and M. Donolo, “Anti-Islanding Today, Successful Islanding in the Future,” in 63rd Annual Conference for Protective Relay Engineers, pp. 1–8, Mar 2010.

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