### Abstract

In microgrids that are predominantly resistive, real and reactive power can be controlled by implementation of voltage and frequency droop laws respectively. However, the variable frequency displayed by such a system complicates analysis such that design approaches rely on approximations and linearized models. In this work, we present a modified form of droop control where only the voltage versus real power relationship is upheld and the frequency is held constant. Since the frequency is not explicitly controlled and the reactive power is not measured, the controller can be simplified. In such a setting, the only assumption we make is that all inverters have access to a common time-reference. Because fixed frequency operation is enforced by design, a variety of analytical tools can be leveraged to formulate a comprehensive analytical framework which facilitates a precise design methodology. In particular, closed-form expressions on the output current phase differences are obtained which yield practical selection guidelines on the voltage-power droop gains such that reactive flows between inverters are kept small. As a corollary, it is demonstrated that there are no reactive power flows in the presence of purely resistive loads. For the particular case of a single inverter, an almost exact solution describing the nonlinear dynamics of the inverter output voltage, current, and power are derived. Accompanying simulation results validate the analytical results and demonstrate the feasibility of the proposed control approach.

Original language | English (US) |
---|---|

Article number | 7039891 |

Pages (from-to) | 3246-3251 |

Number of pages | 6 |

Journal | Proceedings of the IEEE Conference on Decision and Control |

Volume | 2015-February |

Issue number | February |

DOIs | |

State | Published - Jan 1 2014 |

Event | 2014 53rd IEEE Annual Conference on Decision and Control, CDC 2014 - Los Angeles, United States Duration: Dec 15 2014 → Dec 17 2014 |

### Fingerprint

### ASJC Scopus subject areas

- Control and Systems Engineering
- Modeling and Simulation
- Control and Optimization

### Cite this

*Proceedings of the IEEE Conference on Decision and Control*,

*2015-February*(February), 3246-3251. [7039891]. https://doi.org/10.1109/CDC.2014.7039891

**Viability and analysis of implementing only voltage-power droop for parallel inverter systems.** / Salapaka, Srinivasa; Johnson, Brian; Lundstrom, Blake; Kim, Sangsun; Collyer, Scott; Salapaka, Murti.

Research output: Contribution to journal › Conference article

*Proceedings of the IEEE Conference on Decision and Control*, vol. 2015-February, no. February, 7039891, pp. 3246-3251. https://doi.org/10.1109/CDC.2014.7039891

}

TY - JOUR

T1 - Viability and analysis of implementing only voltage-power droop for parallel inverter systems

AU - Salapaka, Srinivasa

AU - Johnson, Brian

AU - Lundstrom, Blake

AU - Kim, Sangsun

AU - Collyer, Scott

AU - Salapaka, Murti

PY - 2014/1/1

Y1 - 2014/1/1

N2 - In microgrids that are predominantly resistive, real and reactive power can be controlled by implementation of voltage and frequency droop laws respectively. However, the variable frequency displayed by such a system complicates analysis such that design approaches rely on approximations and linearized models. In this work, we present a modified form of droop control where only the voltage versus real power relationship is upheld and the frequency is held constant. Since the frequency is not explicitly controlled and the reactive power is not measured, the controller can be simplified. In such a setting, the only assumption we make is that all inverters have access to a common time-reference. Because fixed frequency operation is enforced by design, a variety of analytical tools can be leveraged to formulate a comprehensive analytical framework which facilitates a precise design methodology. In particular, closed-form expressions on the output current phase differences are obtained which yield practical selection guidelines on the voltage-power droop gains such that reactive flows between inverters are kept small. As a corollary, it is demonstrated that there are no reactive power flows in the presence of purely resistive loads. For the particular case of a single inverter, an almost exact solution describing the nonlinear dynamics of the inverter output voltage, current, and power are derived. Accompanying simulation results validate the analytical results and demonstrate the feasibility of the proposed control approach.

AB - In microgrids that are predominantly resistive, real and reactive power can be controlled by implementation of voltage and frequency droop laws respectively. However, the variable frequency displayed by such a system complicates analysis such that design approaches rely on approximations and linearized models. In this work, we present a modified form of droop control where only the voltage versus real power relationship is upheld and the frequency is held constant. Since the frequency is not explicitly controlled and the reactive power is not measured, the controller can be simplified. In such a setting, the only assumption we make is that all inverters have access to a common time-reference. Because fixed frequency operation is enforced by design, a variety of analytical tools can be leveraged to formulate a comprehensive analytical framework which facilitates a precise design methodology. In particular, closed-form expressions on the output current phase differences are obtained which yield practical selection guidelines on the voltage-power droop gains such that reactive flows between inverters are kept small. As a corollary, it is demonstrated that there are no reactive power flows in the presence of purely resistive loads. For the particular case of a single inverter, an almost exact solution describing the nonlinear dynamics of the inverter output voltage, current, and power are derived. Accompanying simulation results validate the analytical results and demonstrate the feasibility of the proposed control approach.

UR - http://www.scopus.com/inward/record.url?scp=84982164803&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84982164803&partnerID=8YFLogxK

U2 - 10.1109/CDC.2014.7039891

DO - 10.1109/CDC.2014.7039891

M3 - Conference article

AN - SCOPUS:84982164803

VL - 2015-February

SP - 3246

EP - 3251

JO - Proceedings of the IEEE Conference on Decision and Control

JF - Proceedings of the IEEE Conference on Decision and Control

SN - 0191-2216

IS - February

M1 - 7039891

ER -