Operation_modes
There are three Control Types that are based on a common principle of Operation Modes. There three Control Types are:
- Operation Mode Based Control (OMBC)
- Fill Rate Based Control (FRBC)
- Demand Driven Based Control (DDBC)
Although these Control Types differ enough to separate them into three distinct Control Types, there are some common aspects that make them similar: Operation Modes, Transitions and Timers. These concepts are explained on this page.
The objective for a Control Type is basically for a CEM to understand what a device is capable of from an energy perspective, under which circumstances what things can be adjusted, and what the constraints are for these adjustments. And for many applications it is important that the CEM can make relatively good predictions of what will happen in certain situations. The three Operation Mode based Control Types do that in similar fashion: they model a virtual, abstract device.
Of course, in the end, it is all about controlling the real, physical device. But the virtual device is a helpful tool. The physical device contains a lot of details that are not relevant for a CEM. The control system of the physical device has all sorts of concerns, but the CEM is only concerned with utilizing energy flexibility. The virtual device ignores all details of the device that are not relevant to a CEM. In addition, physical devices have an enormous variety in parameters, sensors, control strategies, concerns, safeguards, and so on. It would be practically impossible to develop a CEM that can understand all the parameters of all the physical devices on the market. By making the virtual device more abstract, its concepts can be translated to all sorts of physical devices, even though internally the function very differently. As a consequence, it not always possible to make a 100% accurate description of all the behaviors and constraints in these abstractions. But the abstractions used in the control types are quite powerful, and should allow you to come pretty close.
The Control Types basically define how the virtual device can be described. It is the job of the RM to describe the behavior of the physical device as well as it can in the terms of the virtual device. The RM describes how the virtual device functions, what it can do and what kind of constraints it has. It also informs the CEM about the current state of the virtual device. Based on the description of this virtual device, the CEM can make predictions of that the virtual device will do in certain situations, and when it is allowed to send which instruction to the RM. When the CEM sends an instruction for the virtual device to the RM, it is the job of RM to translate this instruction for the virtual device into an instruction to the physical device that would yield the same result. Once the physical device has changed it behavior, the RM should inform the CEM that the virtual device has changed its state accordingly.
The system of Operation Modes is basically based on the idea of a state machine. A state machine is a concept where there any several possible states to be in, but at any point in time there can be only one active state. The state machine can go to another state only if there exists a transition from the current active state to the next one.
For example, see the simple example below:
@startuml
hide empty description
[*] --> Off
Off --> [*]
Off --> ReducedPower
ReducedPower --> FullPower
FullPower --> ReducedPower
ReducedPower --> Off
FullPower --> Off
@endumlA state machine always starts with the black circle, and ends with the white circle with the black circle in it. In this example you start in the state "Off". From there you can go to the state "ReducedPower", but not directly to "FullPower", since there is no transition from "Off" to "FullPower". In other words, you have to go through "ReducedPower" if you want to go to "FullPower".
| Current state | Allowed next states |
|---|---|
| Off | ReducedPower |
| ReducedPower | Off, FullPower |
| FullPower | ReducedPower, Off |
Within S2, Operation Modes are basically the states from the state machine. There can be only one Operation Mode active at a certain point in time. (Note: With FRBC and DDBC you could have multiple Actuators, which each have their own state machine. So for FRBC and DDBC, there is always one active Operation Mode for each Actuator). Each Operation Mode and Transition has certain information associated with it to inform the CEM about the behavior of the device.
Other than the typical state machine, Operation Modes don't have a start and end node, since the operation of a device is basically an ongoing process. When a Control Type is activated, you just start with whatever Operation Mode is currently active on the device. The RM tells the CEM which Operation Modes and Transitions exist. The RM informs the CEM about the active Operation Mode, and immediately notifies the CEM when the Operation Mode changes. The CEM can make a request (through an Instructions message) to make another Operation Mode active, but in the end it is always the RM (or the physical device) that decides which Operation Mode is active. Although not preferable, a RM can active another Operation Mode without the CEM requesting it, and it is even allowed to activate an Operation Mode even if there is no transition from the old one to the new one.
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