Concepts for LVDC microgrid

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2 Concepts for LVDC microgrid DSO TSO Aggregator Markets Power line signal 20 kv 20 kv Mains Protection r rectifier r +750 VDC N -750 VDC r Load Load Load Load Load Load m m Henri Makkonen Tero Kaipia

3 INCA in LVDC - Concepts for LV microgrid LVDC microgrid concept leans on the technology and functional concepts of LVDC power distribution and Interactive customer gateway (INCA) LVDC provides physical network and opportunity to actively control both the public network and end-customers installations INCA provides the human machine interface, communications with external information systems of service proders and intelligent decision making algorithms for controlling the system locally LVDC system concept ICT network components Rectifier PCs with PLC or fiber connects equipment to each other Optical fiber/adsl/@450 connects LVDC to backhaul network (IEC-101 SCADA) Customer interface (MHI) voltage control and measurements Customer inverter INCA concept voltage and load control, PQ-control and measurements Decision making and control algorithms for local system handling Interfaces to external information systems for remote system handling and data exhcange Internal information network for local controls and MHI

4 Objectives and requirements Objectives of market players and related requirements for the system development End-customer / Consumer TSO Safe use of electricity Continuous use of electricity Minimisation of energy costs Connection of own generators Connection and free use of energy storages Power balance management Power reserve management System security management Load profile management Elasticity (* profile management Electricity sales DSO Billing information management Trade optimisation Power demand management Load profile management Elasticity (* profile management Forecasting of distributed generation Billing information management Network capacity management Power demand management Load profile management Elasticity profile management Supply security management Voltage quality management Electrical safety *) How elastic is the power demand of a customer or a group of customers seen from the utility grid side of the customer interface with respect to market situation or electro-technical situation of the grid/power system.

5 Concept of LVDC microgrid

6 Concept of LVDC microgrid network protection DSO Informatio n systems measurements, LoM supervision and management Communication measurements Control system protection, supervision measurements, control TSO/DSO/ TSO/DSO/ Market players Marke t players measurements, control TSO/DSO/ TSO/D SO/ Market players Market players Infor mation system s measurements, control Grid Grid Control system Control system c ontr ol, measurements Home automation H om e autom ation INCA Grid Grid Data Da ta storage sto rage INCA Da ta Data s to rage stora ge Co mmunication n Communicatio Info rmatio n system s Co mmunication Communication Control system C ontrol system cont rol, meas ur ements Home automation Home automation y kwh log no gy ch hnolo r te we tec Po w er Po Storage Storage Generation Generation measurements, control measurements, cont rol Loads Loads Internal control Internal control measurements (contr ol ) y kwh ol og y hn log t ec ch no r we te Po er Pow Storage Storage Generation Generation meas urement s, c ontr ol meas ur ement s, c ontr ol DC Loads Loads Internal control Internal control meas ur ements (c ontrol) TSO/DSO/ TSO/DSO/ Market Marketplayers players Information systems TSO/DSO/ TSO/D SO/ Market players Market players Infor mation system s INCA Grid Grid Da ta Data s to rage stora ge Co mmunication Communicatio n Data Data storage storage Communication Communication Control system Control system c ontr ol, measurements Home automation H om e autom ation kwh ol ogygy hn olo ec hn rt we tec Po wer Po Storage Storage Generation Generation meas urement s, contr ol meas ur ement s, contr ol Loads Loads Internal control Internal control measurements, control Control system Control system INCA control, measurements Home automation Home automation Grid Grid y kwh olog gy hn lo e c hno r t ec we t P o owe r P Storage Storage Generation Generation measurements, control meas ur ements (c ontrol) measurements, control Loads Loads Internal control Internal control measurements (control)

7 DC-grid models a) b) DC-microgrid models by a) Brenna et al., 2006 and b) Nilson, 2005.

8 DC-grid LVDC-grid forms a natural microgrid where loads and microproduction can be installed. Because of the rectifier, it can be easily disconnected from and connected back to the MV network. Stability of the DC-network can be maintained by measuring the DC-voltage, applying voltage droop method, controlling generator units and loads Controlling the power of all generator units is not effective. Instead, demand control can be executed rapidly. The need of the load control can be reduced by installing energy storages in the microgrid. In addition to control of the each generator and load unit, DC-grid requires system stage control, which secures that the unit control will not make the grid oscillate. The information network in LVDC-system helps to carry out the control and protection system in microgrid operations.

9 Grid operator/ Aggregator ICT network structure Customer inverter Backhaul Network Measurements PLC/ Fiber PC Load control EV Heating Lights Rectifier PLC/ PC Fiber Customer inverter etc Measurements Measurements EV PLC/ Fiber PC Load control Heating Lights etc

10 Critical data transfers Measurement data LVDC-link data Phase voltages: RMS & Peak Voltage dip Phase currents: RMS & Peak On service Neutral current: RMS & Peak System on halt DC voltage System startup DC current Normal conditions Current linkage Interuptions IGBT temperature Measurement data Case temperature Harmonic voltages

11 Overall control structure Distribution system Power system Electricity markets Feedback Relevant measurements Customer behaviour Local measurements External control systems Market information System information Internal gateway control Direct control signals Direct control signals Internal device specific control Customer s priorities

12 Main controls Local actions Related with consumption and customer decicions Load control Lowering voltage Switching off loads (heating, sauna, etc) Energy storage control Intelligence charging of electric car Charging/discharging if necessary Voltage quality control Requires local optimistaion algorithm combining the external inputs and local information Adaptive load models Measurement data storaging Remote actions Related with grid owner/electricity seller Load control Direct signals possible (voltage level, load switching, etc.) Normally done by guiding the decision making internally in customer interfaces permission for EV charging/discharging Direct power intake limits Electric energy price information (hourly prices+15 min. prices) System supervision Electric safety

13 Control system 1/3 There are three main levels in the control system of the interactive customer gateway. The first and the highest level control is formed by the algorithms in the information systems of the DSO, TSO and the energy suppliers. The second level of control is the main control of the customer gateway. The third control level is formed by the individual control algorithms of the active devices in the customer s network, like building automation, generator interface converters, AMR meter, sensitive heating system control, active voltage controller, etc. The two upper level controls are the most important for achieving coordinated interoperation of the interactive customer gateway. The execution of the control signals given by the two upper levels are dependent from the operation of the third control level. The control algorithms are based on operations models that define the basic actions to in each situation. The control algorithms should be adaptive

14 Control system 2/3 The main tasks of the first (external) and second (internal) level control algorithms are: Recognition of active resources and creation of patterns for customer behaviour (internal) Classification of the resources according to their elasticity, applicability and random variation (internal and external) Creation of customer specific load and elasticity profiles (internal) Short-term estimation of loads and local generation (internal) Short-term estimation of market behaviour (external) Optimisation of system loads for different market players based on measurement data, short-term forecasts, and load and elasticity profiles (external) Optimisation of load profiles of individual customers based on given market information, direct control signals, customer behaviour and short-term forecasts (internal) Recognition and finding solutions for power quality problems (external and internal)

15 Control system 3/3 The main target of the third control level is to take care of the execution of the upper level control signals in boundaries of momentary state of the system locally. The third and second level controls have to work seamlessly together so that when the local situation changes, i.e. customer behaves unexpectedly or an disturbance occur somewhere in the system, the first operations are to stabilise the situation and to inform external actors of the situation and of the actions by the gateway due to it, so that the harm caused either to external market players and/or to the customer are minimised.

16 Case: EV control Plug-in Charge Permission Discharge Not full SOC SOC High Full Low User setup Do nothing Wait for charging User setup Charge now Charge later Do nothing Discharge

17 Case: Island operation Normal Grid Switch to grid Normalize voltage Connect loads Loss of Main LOM- signal dissapears Voltage drops Wait for grid Voltage measurement LOM-signal Switch off from grid Discharge User setup Lower voltage Disconnect loads User setup Case: Green Campus -