1 Descriptions of Function Communication with Remote CB attached to Home appliances, and EV Normal...
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1 Descriptions of Function Hierarchical control of DMS and μDMS for local load/supply control to mitigate transformer/secondary feeder overload, and prevent voltage violations.
1.1 Function Name Control algorithms of DMS and μDMS are proprietary (non-publicly available).
1.2 Brief Description This use case describes how a DMS and μDMS can cooperatively control local loads (EV, water heater, water pump, battery), and local supply (battery) to reduce mitigate transformer / secondary feeder overload, and prevent voltage violations. There are four (4) levels of control in this use case:
1. EMS that monitors and controls generation units and DMS
2. EVECC that monitors and controls EV charging in the region
3. DMS controls a Bulk battery PCS and μDMS
4. μDMS monitors and controls a Local Battery, Home Gateway
There are three(3) scenarios in this use case:
1. Normal Operations This scenario shows how the system operates when there are no violations or overloads.
2. Transformer/secondary feeder overload This scenario shows how the DMS detects the possibility of a feeder overload and responds through the μDMS and Home Gateway to control the EV charger and home appliances as necessary to mitigate it.
3. Voltage violation event This scenario shows what happens when the μDMS detects the possibility of a voltage violation (over voltage condition) and responds through the μDMS and Home Gateway to control the battery to prevent voltage violations.
1.3 Narrative High penetration levels of variable generation from renewable energy resources and increased variability of demand caused by EV charging can have adverse impacts on the stability of distribution systems. The operations of distributed resources (DR) may significantly impact the voltages at different locations of the Maui grid. The impact on voltage-regulating devices of the Maui grid may have a potential of creating too high voltage; voltage imbalance; intermittent operations which may result in unacceptable voltage fluctuations; or impproper regulation during reverse power flow conditions. Hierarchical control schemes can be used to cordinate DR with voltage/var control devices and mitigate voltage fluctuations. This is a System Level Use Case that describes a hierarchical control scheme in which a DMS and μDMS can cooperatively control EV, home appliances, and local battery to mitigate transformer/secondary feeder overload and prevent voltage violations caused by PV intermittency and EV charging. This use case explains operation and control strategies that use a hierarchical control scheme that includes an EMS, EVECC, DMS, µDMS, and Home Gateway. The functions and operations of each of these are described below.
EMS, DMS, µDMS, and Home Gateway Functions
System that monitors/controls the real-time network; includes generation control and load forecast functions.
Monitors and controls transmission lines and substations via SCADA.
EVEMS (Energy Management System) function that makes EV charging schedules based on available capacity sent from DMS.
EVCMS (Car Management System) function that monitors EV status, such as state of charge, and sends EVs’ SOC data to DMS via EVEMS Function.
Monitors and controls distribution feeders via SCADA. .
Generation/Execution of Switching Procedures that automatically generate and execute switching procedures (after confirmation by DSO).
Load Forecasts that calculates load forecasts for distribution feeders or sections between switches under its control. [Note: The load of feeder or section is Gross load and includes PV output.].
Distribution Simulation System that simulates power flow for distribution feeders under its control.
Demand Response Management that controls demand-side appliances through Home Gateways.
Communications with µDMS for data exchange and to exercise cooperative control. (Exchanges data and exercises cooperative control with µDMS,)
Communications with EVECC, EMS, and MDMS for data exchange
μDMS Functions Monitors load and voltage of LV transformer.
Controls demand-side appliances directly through Home Gateways (in cooperation with the DMS and indirectly through the EMS). (Exchanges data and exercises cooperative control with the DMS and Home Gateway.)
Communication with Remote CB attached to Home appliances, and EV Normal charger to exchanges data and controls Home appliances, and EV Normal charger.
Communication with µDMS
Communication with Home Display (Customer Laptop PC or Cell phone)
Management Asset Inventory data via Home Display
Scenarios In each of the scenarios in this use case, the main control functions are conducted at the operations level of the distribution utility, namely the Maui grid EMS which controls dispatchable generation resources and the DMS. The distribution network is managed and controlled each level separately, as a subsystem. The μDMS manages at the local level, controlling EV, home appliances, and local batteries. The DMS manages at the substation level, controlling the μDMS and MV section switches. Then, global optimization is performed at the Maui grid level. 1-Normal operation During normal operations, the μDMS periodically monitors (i) EVs’ SOC (State of charge) through EVECC and the DMS, (ii) AMI meter data through ΜDMS and the DMS, (iii) SOC of local battery, (iv) transformer’s secondary voltage and current, (v) PV output and Home Gateway, and (vi) Home appliance status through Home Gateway. 2-Transformer/secondary feeder overload When the μDMS detects a violation (feeder overload), the μDMS sends control signal to the local batteries, and sends load shedding signal to EV normal charger in home, and Home Appliances via Home gateway. In case that Home gateway executes any load shedding, Home gateway sends information signal to EMS via the DMS and the μDMS. Then, the light on DMS’s DASH board changes to “red light” and the operator can recognize the load shedding execution. After the μDMS confirms that the violation situation has been corrected, it sends control signals in sequence to restore normal situation. The μDMS also periodically monitors transformer’s secondary current after the execution of load shedding to calculate the amount of shed load. If the amount of shed load is not enough, the μDMS implements an additional load shedding, if possible. If the μDMS detects the current achieves a target current and remains under it for an enough period, the μDMS starts restoring operation of Home Appliances, EV normal chargers, and Local Batteries. The amount of restored load is calculated from present current and restoring target in order to prevent transformer’s secondary feeder overload again. First, the μDMS restores Home Appliances. The order of restoring power is contrary to one of shedding. Second, the μDMS restores EV normal charger in home. The order of restoring is also contrary to one of shedding. Then, the μDMS tells Local Battery to recover. Finally, the μDMS informs the DMS of completion of restoring operation. 3-Voltage violation event When the μDMS detects a voltage violation event (over-voltage situation), the μDMS reports information of Middle voltage violation to the DMS, Then, the DMS sends this information to the EMS before starting control, to ask the EMS to decide whether Middle voltage violation is the EMS’s matter or not. If it is not the EMS’s problem, the DMS sends a control signal to local battery. After that, the μDMS sends information to the DMS. Then, the DMS transfers information to the EVECC.
The EVECC sends new charge schedule data to EV. The μDMS also periodically monitors transformer’s secondary voltage after control of voltage violation. If the μDMS detects the voltage achieves a target voltage and remains in the target range for an enough period, the μDMS starts restoring operation of EVs, Local Batteries. The amount of restored load is calculated from present voltage and restoring target voltage, in order to prevent transformer’s secondary feeder voltage violation again. First, the μDMS restores EVs by sending the new schedule via the DMS and EVECC. Then, the μDMS tells the Local Batteries to recover. Finally, the μDMS informs the DMS of completion of restoring operation.
1.4 Actor (Stakeholder) Roles
Actor Name Actor Type (person, organization, device, system, or subsystem)
EV Equipment Movable equipment that has a battery. Its battery can be charged by an EV charger in home, public EV charger or quick charger. It can send its information such as “SOC” to an EVECC via an EV network operation ce