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Abstract

Contents

Introduction

The reason for writing this work was the necessity to improve the efficiency of heating systems. Greater efficiency is achieved in several ways, one of which - the rational use of resources. Automatic control of heat supply allows to use resources more efficiently. It allows to reduce overuse to a minimum, and often to zero.

Cost-effective heating systems is an important task, since it has a significant impact on the cost of every medium and large enterprises, and therefore has an impact on the economic situation of the state.

1. Review and analysis of the known solutions for automation of heating systems

Automation of heating systems - using a complex of automated equipment to control process in heating systems. Automation systems include heat regulation (in particular, stabilization) of the parameters, management of equipment and components (remote, local), and blocking their protection, control and measurement, metering and consumed resources, telemetry management, control and measurement. AHS provides high quality management and performance of individual objects throughout the system as a whole, increases the reliability and level of operation of heating systems, helps to save energy, material and labor resources[1]. 

To date, the problem of automation of heating systems are solved effectively through:

- integrated Automation;

- Quality implementation of technological process;;

- The rational organization of technological regimes with optimal loading of process equipment;

- Applicating technology of frequency control of pump and forced draft units performance with management on energy-and resource-efficient algorithms[2]. 

2. Analysis of the automation object

Through the pipes of heat supply system circulates a heat transfer fluid. Over time, the heat transfer fluid gives up its heat to the air in heated rooms. Necessary to increase the temperature of the coolant to the original level. Raising the temperature of the heating system occurs due to heat exchange with the hot water circulating through the pipeline. Heating of this hot water occurs in the heat exchanger, which are connected to a water pipe from the power center. Water from the energy center and pipeline thus do not mix. The control valve adjusts the amount of heat transferred by changing the water flow through the heat exchanger - it is either opened or closed by a certain percentage.

The coolant with the water temperature, which shows a temperature sensor is supplied through a control valve into the heat exchanger where the heat transfer part of its energy to the heated water and then returnes to the power plant with low water temperature. Temperature of the water coming from the energy center is independent from the control system and is large enough to carry out its tasks - heating the coolant.

The movement of water is carried out by circulating pumps, the management of which is advantageously carried out by proportional-integral-derivative (PID) control law. This allows to have a short time transients and maintain the system pressure at the desired level. For this problemcan be used standard motors with integrated frequency converter, incorporating a PI controller, and can be customized to fit an external sensor that ensures adjusting the pressure. The amount of heat transmitted from the and pipeline to the heating circuit is also regulated by valves.

To control the operation of the pump and detect its emergency situation installed differential pressure sensor. If pump inlet formed airbag tube, the pressure difference between the inlet and outlet increases, and the sensor signal is received by the remote operator. The pressure in the system shows a pressure sensor. The temperature in the heating circuit is also taken from a sensor.

Based on the above, you can select the control-driven values and disturbances.

The parameters by which the control system can influence the OS may be:

- speed of pumps;

- The percentage of the valve's opening to the heating circuit.

At the same time the parameters of the OS, the system should adjust are:

- Water pressure in the heating system;

- The temperature of the water in the heating system.

As disturbing effects in this work will be considered:

- The influence of the ambient temperature (room temperature);

- Change by users of the heating system configuration(on / off radiators).

3. Statement of the objectives of the research

To create an automatic control system is necessary to solve the following tasks:

- Stabilization at a given level of pressure by controlling the rotational speed of the pump shaft.;

- The distribution of the load between two pumps;

- Stabilization at a given level of coolant temperature in the radiator circuit. Stabilization performed by controlled valves, which opens / closes the drive;

- Stabilization at a given level of the flow temperature in the heating coil. It comes from the outside heat exchanger hot water fixed temperature (energy center). Stabilization performed by controlled valves, which open / close the drive.

4. Solution of tasks and research results

Since the pump in this system is to slow, the transfer function of the pump can take a transfer function of a first-order delay element. Pipe system selected length can be modeled as an inertial element of the first order with a time constant of about 25 seconds. To manage the system controller is selected with PID control law, which combines the quality of the PI and PD controllers. This control has zero static error due to the integral term.

On the basis of the recommended values and by experimental verification was obtained setting Kp = 15 Td = 35, td = 1.5, Ki = 20 Ti = 35. With these values, it is possible to build a model using ACS PID control law. Synthesis of temperature ACS in the heating coil is made similarly to the above synthesis [3-5].

Conclusions

In this work was developed a block diagram of the object model and, quite accurately described system of sports complex heating.

Speed control of the pump rotor by PID Law gave good results in the simulation and has proven effective in comparison with other laws.

Use as a regulator controlled valves for automatic control circuits of temperature in heating system and heating coil led to good performance of the system, ease of implementation and low operating costs.

At the present day master's work is not yet complete. In the future several major sub-systems (ventilation, water supply) will be developed, and they will be combined into a comprehensive system of life support. Terms of completing the work - in December 2013.

References

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