Abstract
This paper presents new findings on phenomena contributing to flicker and voltage variations caused by grid-connected photovoltaic (PV) inverters. The voltage variations caused by two different 6 kW single-phase grid-connected PV inverters were studied during climatic variations by varying their grid-coupling impedance. Two different methods for characterizing the PV-plant induced voltage variations were studied: the short-term flicker index (Pst) and the 10 minute very-short voltage variation value (VSV). The results clearly indicate that PV inverter power fluctuations induced by cloud shading and enhancement have a significant effect on the VSV value, but not on Pst. PV inverters have a clear effect on the Pst as well, but the main contributors are related to the inverter design rather than the power fluctuations caused by clouds. The main contributor in the elevated Pst values could be traced back to the poor design of the maximum power point tracking (MPPT) of the inverters. The MPPT caused subharmonic current variations at a frequency of approximately 8 Hz which is close to the most sensitive frequency of human eye. Another factor causing rapid voltage variations in low irradiance conditions was the current transients related to the inverter start-up and shut-down. Harmonic current distortion is also a potential PV inverter related power quality (PQ) issue. This study indicates that although the current total harmonic distortion (THD) may be very large at low power levels the total demand distortion (TDD) of the PV inverters is almost constant regardless of the output power and the harmonic current had only a very limited effect on the voltage quality even at the weakest network having a short-circuit current of Isc=250 A. Thus, voltage variations caused by the PV inverters were the main PQ issue in the studied networks. The investigations also clearly show that a part of the power quality problems found i- the PV plants are caused by the poor design of the PV inverters.
| Original language | English |
|---|---|
| Title of host publication | 2016 18th European Conference on Power Electronics and Applications (EPE'16 ECCE Europe) |
| Publisher | IEEE |
| Pages | 1-10 |
| Number of pages | 10 |
| ISBN (Electronic) | 978-9-0758-1524-5 |
| DOIs | |
| Publication status | Published - 27 Oct 2016 |
| Publication type | A4 Article in conference proceedings |
| Event | EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS - Duration: 1 Jan 1900 → … |
Publication series
| Name | |
|---|---|
| ISSN (Print) | 2325-0313 |
Conference
| Conference | EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS |
|---|---|
| Period | 1/01/00 → … |
Keywords
- harmonic distortion
- invertors
- maximum power point trackers
- photovoltaic power systems
- power supply quality
- MPPT
- cloud shading
- grid-connected PV power plant
- grid-connected photovoltaic inverters
- grid-coupling impedance
- harmonic current distortion
- maximum power point tracking
- power quality
- short-term flicker index
- total demand distortion
- total harmonic distortion
- voltage variation value
- Clouds
- Current measurement
- Fluctuations
- Inverters
- Power quality
- Short-circuit currents
- Voltage fluctuations
- Flicker
- Harmonics
- Photovoltaic
- Renewable energy systems
Publication forum classification
- Publication forum level 1
Access to Document
- Pakonen_et_al_EPE_2016
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