**3.1.3 Smart dispatch**

78 Renewable Energy – Trends and Applications

Smart dispatch (SD) represents a new era of economic dispatch. In general, economic dispatch is about the operation of generation facilities to produce energy at the lowest cost to reliably serve consumers, recognizing any operational limits of generation and transmission facilities. The problem of economic dispatch and its solutions have evolved

The evolution timeline of economic dispatch could be divided into the following three major

2. Market-based dispatch [1990's – 2010's] (Schweppe et al., 1998; Ma et al., 1999; Chow et

Since the birth of control center's energy management system, classical dispatch monitors load, generation and interchange (imports/exports) to ensure balance of supply and demand. It also maintains system frequency during dispatch according to some regulatory standards, using Automatic Generation Control (AGC) to change generation dispatch as needed. It monitors hourly dispatch schedules to ensure that dispatch for the next hour will be in balance. Classical dispatch also monitors flows on transmission system. It keeps transmission flows within reliability limits, keeps voltage levels within reliability ranges and takes corrective action, when needed, by limiting new power flow schedules, curtailing existing power flow schedules, changing the dispatch or shedding load. The latter set of monitoring and control functions is typically performed by the transmission operator. Traditionally, generation scheduling/dispatch and grid security are separate independent tasks within control centers. Other than some ad hoc analysis, classical dispatch typical only addresses the real-time condition without much consideration of scenarios in the past or the

Ensuring reliability of the physical power system is no longer the only responsibility for the RTO/ISOs. A lot of the RTOs/ISOs are also responsible for operating wholesale electricity markets. An electricity market in which the ISO or RTO functions both as the "system operator" for reliability coordination and the "market operator" for establishing market prices allows commercial freedom and centralized economic and reliability coordination to co-exist harmoniously (Figure 2). To facilitate market transparency and to ensure reliability of the physical power system, an optimization-based framework is used to provide an Taking advantage of the mathematical rigor contained in formal optimization methodology, the rules are likely to be more consistent, and thus more defensible against challenges that effective context for defining comprehensive rules for scheduling, pricing, and dispatching.

Congestion management via the mechanism of locational marginal pricing (LMP) becomes an integral part of design of many wholesale electricity markets throughout the world and

1. Classical dispatch [1970's – 1990's] (Wood & Wollenberg, 1996)

**3. Smart dispatch of generation resources** 

3. Smart dispatch [2010's – ] (Cheung et al., 2009)

**3.1 Evolution of economic dispatch** 

over the years.

al., 2005)

**3.1.1 Classical dispatch** 

**3.1.2 Market-based dispatch** 

invariably arise in any market.

periods:

future.

Smart dispatch (SD) is envisioned to be the next generation of resource dispatch solution particularly designed for operating in the smart grid environment (Cheung et al., 2009). The "smartness" of this new era of dispatch is to be able to manage highly distributed and active generation/demand resources in a direct or indirect manner. With the introduction of distributed energy resources such as renewable generations, PHEVs (Plug-in Hybrid Electric Vehicles) and demand response, the power grid will need to face the extra challenges in the following areas:


A lot of the new challenges are due to the uncertainties associated with the new resources/devices that will ultimately impact both system reliability and power economics. When compared to the classical dispatch which only deals with a particular scenario for a single time point, smart dispatch addresses a spectrum of scenarios for a specified time period (Figure 3). Thus the expansion in time and scenarios for SD makes the problem of SD itself pretty challenging from both a computational perspective and a user interface perspective. For example, effective presentation of multi-dimensional data to help system operators better visualize the system is very important. Beside a forward-looking view for system operators, SD should also allow after-the-fact analysis. System analysts should be able to analyze historical data systematically and efficiently, establish dispatch performance measures, perform root-cause analysis and evaluate corrective actions, if necessary. SD will become an evolving platform to allow RTOs/ISOs to make sound dispatch decisions.

Fig. 3. Time and Scenario Dimensions in Smart Dispatch
