ABB Switzerland Ltd. Christoph Haederli Distributed Power Generation Units and Their Impact on the Power Network ABB Switzerland Ltd. Christoph Haederli

Large scale DG interconnection System parameters Protection Stability “Plug and Power” “Virtual DG” in small European town

Case Study with Small European Town Study in CALPOS Real network (ca. 1 km2) “random” placing of DG 5 MVA load / 7 MVA DG

Considered Network Configurations Meshed network configuration Three MV lines MV transformers connected on LV level (All LV lines connected in selected area). Redundancy for MV lines Station to station (non meshed) network configuration Three MV lines No connection between MV transformers on LV level No redundancy for MV lines

Voltage Profile All these nodes are LV-nodes. In the MV-network, the voltage profile is in the admissible range for all calculated cases. Load profiles applied Admissible range: -10 / +6 % (Germany)

Voltage Rise in Station to Station LV-grid

Voltage Rise in meshed LV grid

Voltage Rise in Station to Station LV-grid

Loading of LV Network All these lines are LV-lines.

Comparison of Network Configurations Meshed LV grid with multiple MV strands higher reliability more balanced voltage profile smaller voltage rise at load steps lower equipment loading (in normal operation) lower losses can handle more DG without alterations in grid Non-meshed LV grid with station to station supply higher capacity with the same amount of resources simple design, easier to plan and extend Cheaper No reverse power relays needed Lower short circuit power

Impact on Protection Qualitative Quantitative Reverse power flow Additional functionality required (Loss of mains detection, etc.) Quantitative Relay parameter settings Increased short circuit power Selective tripping schedule of distance protection relays with infeed effect

Reverse Power Relays MV Line 1 Reverse Power Relay Meshed LV grid DG may trip reverse power relay under normal operating conditions

Ik” Indicators on MV Line (Small Town Study) ( Ik” = short circuit current )

Stability: Inverter Based DG Configuration DG-power conditioner

Stability: Equivalent Network with Multiple DG Paralleling of inverters in LV grid Line parameters from small town case study

Robust Stability Analysis

Stability Analysis, Parallel Units Number of units allowed for stable operation (Generic 100kW DG model used for calculations) Stability depends very much on filter and control Other configurations may allow higher numbers of parallel units

Conclusions “Plug and power” for small units and small aggregated power. Limited “Plug and power” for intermediate Power No “Plug and power” for large units and a lot of aggregated power. Advanced planning Economical barriers Important factors Network configuration DG type Stability depends strongly on network impedance, filter design and control of DG A significant share of power can be supplied locally by DG without reverse power flow into the network