CN201129829Y - Central air-conditioning variable temperature difference energy-saving control system - Google Patents

Abstract

The utility model relates to a central air-conditioning variable temperature difference energy-saving control system. In order to solve the defects of the current constant temperature difference energy-saving control system, the utility model includes a temperature sensor, a water pump inverter, and a temperature difference calculation for calculating the corresponding supply and return water temperature difference. It is used to store the temperature difference set value memory of the time-temperature difference matrix table obtained according to the terminal load and electricity price in different periods, and is connected with the freezing temperature difference set value memory, and is used to select the temperature difference corresponding to the temperature difference set value according to the current time The set value selector, and the fuzzy controller which is connected with the temperature difference calculator, the temperature difference set value selector and the water pump inverter and can calculate and output the corresponding frequency given signal to the water pump inverter according to the current actual temperature difference and the temperature difference set value . The system of the utility model can ensure that the central air conditioner can not only achieve the best energy-saving operation state, but also reduce the electricity cost to the greatest extent under different load conditions.

Description

Central air-conditioning variable temperature difference energy-saving control system

technical field

The utility model relates to a central air-conditioning energy-saving control technology, in particular to a central air-conditioning variable temperature difference energy-saving control system.

Background technique

In traditional technology, when designing a central air-conditioning system, the maximum load is usually considered, and equipment with corresponding power is selected. The freezing/cooling water pumps also work in a constant flow (power frequency) mode, so that in actual operation, the system load is far away. less than the design load. At the same time, since the freezing/cooling water pump operates in a constant flow (power frequency) mode, the operating power is constant, so that the energy consumed per unit cooling capacity increases and the system efficiency decreases.

In order to improve system operation efficiency and reduce energy consumption, many energy-saving control systems with frequency conversion technology as the core have been proposed, among which the most commonly used one is the constant temperature difference energy-saving control system. The working principle of the system is to keep the temperature difference of the freezing/cooling water constant, and when the load changes, the flow rate of the freezing/cooling water pump is adjusted by the frequency converter, thereby reducing the energy consumption of the freezing/cooling water pump.

However, as the end load changes, the optimal temperature difference set point for central air-conditioning energy saving will also change. In the case of satisfying the comfort of the end, simple constant temperature difference control cannot achieve the best energy-saving operation state of the central air conditioner. In addition, the constant temperature difference control cannot effectively use the peak-to-peak-valley electricity price policy for peak-shift electricity consumption, so as to more effectively reduce electricity costs while saving energy.

Utility model content

Aiming at the above-mentioned defects of the prior art, the utility model solves the problem that the current constant temperature difference energy-saving control system cannot ensure that the central air conditioner can achieve the best energy-saving operation state and reduce the electricity cost to the greatest extent under different load conditions.

The technical scheme of the utility model is to provide a central air-conditioning variable temperature difference energy-saving control system, which includes: a chilled water supply temperature sensor installed on the chilled water supply main pipe; a chilled water return temperature sensor installed on the chilled water return main pipe; sensor; the cooling water supply temperature sensor installed on the cooling water supply main pipe; the cooling water supply temperature sensor installed on the cooling water supply main pipe; respectively connected with each temperature sensor, chilled water pump frequency converter and cooling water pump frequency converter, can A frequency controller that receives temperature signals from each temperature sensor, calculates and outputs corresponding frequency given signals to chilled water pump inverters and cooling water pump inverters respectively.

In the utility model, an IPC (industrial control computer) connected with the frequency controller is also included.

In the utility model, the frequency controller can be realized by a PLC (Programmable Logic Controller), and for the chilled water pump frequency converter, it includes: a chiller connected to the chilled water supply temperature sensor and the chilled water return temperature sensor The temperature difference calculator is used to store the freezing temperature difference setting value storage of the freezing temperature difference setting value that changes with the time period, and is connected with the freezing temperature difference setting value storage, and is used to select the freezing temperature difference corresponding to the freezing temperature difference setting value according to the current time The set value selector is connected with the freezing temperature difference calculator, the freezing temperature difference set value selector and the chilled water pump frequency converter and can be calculated according to the current freezing temperature difference and the freezing temperature difference set value and output to the chilled water pump frequency converter Fuzzy controller for given signal of corresponding frequency;

For the cooling water pump inverter, it includes a cooling temperature difference calculator connected to the cooling water supply temperature sensor and the cooling water return temperature sensor, and a cooling temperature difference setting value memory for storing the cooling temperature difference setting value that changes with time periods, It is connected with the cooling temperature difference setting value memory, and is used to select the cooling temperature difference setting value selector corresponding to the cooling temperature difference setting value according to the current time, and is connected with the cooling temperature difference calculator, the cooling temperature difference setting value selector and the cooling The water pump inverter is connected to a fuzzy controller that can calculate and output corresponding frequency given signals to the cooling water pump inverter according to the current cooling temperature difference and the set value of the cooling temperature difference.

In the central air-conditioning variable temperature difference energy-saving control system of the utility model, the energy-saving mode of variable temperature difference fuzzy control can be adopted. First, according to the terminal load and electricity price in different periods, the corresponding optimal temperature difference is set as the temperature difference setting value, and the time-temperature difference matrix is obtained. table, and then stored in the memory of the freezing/cooling temperature difference set value; during specific operation, on the one hand, the fuzzy control can be used to optimize the system operation and reduce the energy consumption of the central air-conditioning system under the condition of satisfying the end comfort; With a given temperature difference, while reducing energy consumption, make full use of the peak, flat and valley electricity price policy to reduce electricity costs. It can be seen that after adopting the variable temperature difference energy-saving control system of the central air-conditioning of the present utility model, the central air-conditioning can not only achieve the best energy-saving operation state, but also reduce the electricity cost to the greatest extent.

Description of drawings

The utility model will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the functional block diagram of the variable temperature difference energy-saving control system of the central air conditioner of the present invention;

Fig. 2 is a control program block diagram of the PLC (programmable logic controller) shown in Fig. 1 .

Detailed ways

A preferred embodiment of the utility model is shown in Fig. 1 and Fig. 2 . It can be seen from Figure 1 that in the central air-conditioning variable temperature difference energy-saving control system, it includes chilled water supply temperature sensor, chilled water return temperature sensor, cooling water supply temperature sensor, cooling water return temperature sensor, controlled by PLC (can Programmable logic controller), frequency controller, IPC (industrial control computer), chilled water pump frequency converter, cooling water frequency converter. During specific implementation, corresponding computer programs will be written in PLC and IPC.

Among them, four temperature sensors are successively installed on the chilled water supply main pipe, chilled water return main pipe, cooling water supply main pipe, and cooling water return water main pipe, and are responsible for collecting the corresponding water flow temperature. After these temperature signals are converted into digital signals, input PLC; based on the received temperature signal and combined with the internal preset data, the PLC outputs the corresponding frequency given signal to the chilled water pump inverter and the cooling water pump inverter; after the inverter receives the frequency given signal from the PLC, it This adjusts the output frequency to control the flow of chilled water pumps and cooling water pumps.

Among them, the IPC is connected with the PLC to display the running status of the system, accept the operator's operation, and perform functions such as remote Web publishing. It mainly has the following four functions:

(1) Acquisition of various status data of PLC and transmission of control information, including feedback and setting of inverter operating frequency, start-stop operation of various equipment, etc.;

(2) Various parameter status display and alarm processing, including animation display of running status of host, chilled water pump and other equipment, high temperature alarm of cooling water, etc.;

(3) Accident recall and trend analysis, including operation records, equipment operation records, energy consumption reports, load curves, temperature curves, etc.;

(4) Connection with other management information systems, such as seamless connection with other existing systems such as BA (Building Automation) systems through OPC (Object Linking and Embedding for Process Control) technology, or remote control through Web technology monitor.

As shown in Figure 2, inside the PLC, there are the following modules: temperature difference calculator, temperature difference preset value memory, temperature difference set value selector, and fuzzy controller. In fact, there are one set of such modules for chilled water pump frequency converter and cooling water pump frequency converter, and the functions of each module will be described in detail below.

The temperature difference calculator is used to receive the chilled water supply temperature and the chilled water return temperature to calculate the chilled water supply and return temperature difference, or receive the cooling water supply temperature and the cooling water return temperature to calculate the cooling water supply and return temperature difference.

The temperature difference predetermined value memory is used for storing the time-temperature difference matrix table. During specific implementation, one week (7 days) is taken as a set period, and two hours are taken as a set period, and the temperature difference set values of each period are stored. There are a total of 84 data items in the matrix table, which correspond to the temperature difference setting values of each period from 0:00 to 24:00 for each day of the week. The content of each value can be integrated through IPC to integrate the load change (forecast) situation in each day The peak and valley electricity price policy is set by the operator. For example, when the electricity price is flat, the temperature difference setting value is adjusted to be small, and the thermal inertia of water is used to store energy; when the electricity price is peak, the temperature difference setting value is increased to release energy. At the same time, in order to facilitate the actual operation adjustment, a service quality adjustment value QS based on the time-temperature difference matrix table is set separately. When QS<0, output temperature difference set value=(time-temperature difference matrix table temperature difference)+|QS|; when QS>0, output temperature difference set value=(time-temperature difference matrix table temperature difference)-QS.

The temperature difference set value selector in FIG. 2 is used to detect the PLC system time, and query the time-temperature difference matrix table from the temperature difference set value memory according to the time, so as to obtain the temperature difference set value of the corresponding time period. The PLC system time has automatic time synchronization function and can be manually set through IPC.

The fuzzy controller takes the temperature difference of supply and return water output by the temperature difference calculator as the process value input, and the temperature difference output by the temperature difference set value selector as the set value input, and calculates the temperature difference deviation value and the rate of change of the temperature difference deviation value (these are accurate quantities ), after fuzzifying it, get the fuzzy set, according to the fuzzy set, query the fuzzy control rule base, determine the fuzzy control rules, and then apply the fuzzy reasoning method corresponding to the fuzzy control rules to make fuzzy decision-making, and get the corresponding fuzzy control rules The control set is used to clarify the fuzzy control set to obtain the precise control quantity, and finally output the control quantity to the frequency converter to realize the frequency conversion control of the water pump.

In specific use, users can predict the load conditions in different periods according to the weather forecast and past operation records, and determine the corresponding optimal temperature difference according to the peak, flat and valley electricity price policies, and fill in the time-temperature difference matrix table through IPC. Therefore, at each time period, the fuzzy controller can obtain the best temperature difference setting value, and therefore the central air conditioner can achieve the best energy-saving operation state and minimize the electricity cost.

It can be seen that in the central air-conditioning variable temperature difference energy-saving control system of the present utility model, the time-temperature difference matrix table is set in the PLC, the system temperature difference setting value is variable at different time periods, and the system is variable temperature difference control; and the time-temperature difference The matrix table is set according to the forecasted load and the peak and valley electricity prices in different periods; the service quality adjustment value QS can also be set, and the time-temperature difference matrix table can be adjusted uniformly based on this value; the fuzzy control algorithm is also used to optimize the control of the system.

After adopting the central air-conditioning variable temperature difference energy-saving control system of the utility model, the user can predict the load value of each time period according to the weather forecast and previous operation records, and determine the best temperature difference value of each time period accordingly, and then use these temperature difference values to set the time -Temperature difference matrix table; based on this time-temperature difference matrix table, the system can operate with variable temperature difference in time intervals, so that the system can be in the best energy-saving operation state at each time period; at the same time, users can adjust the settings according to the peak, flat, and valley electricity price policies Time-temperature difference matrix table, staggered peak power consumption, so as to minimize power consumption while saving energy. Calculations show that the central air-conditioning system of the utility model has a comprehensive power-saving rate of 20%, is very flexible in operation, and also greatly improves the stability of environmental parameters.

Claims (4)

1. A central air-conditioning variable temperature difference energy-saving control system, characterized in that it includes: Chilled water supply temperature sensor installed on the chilled water supply main; Chilled water return temperature sensor installed on the chilled water return main pipe; Cooling water supply temperature sensor installed on the cooling water supply main pipe; Cooling water supply temperature sensor installed on the cooling water supply main pipe; They are respectively connected to the temperature sensors, chilled water pump inverters and cooling water pump inverters, can receive the temperature signals of the various temperature sensors, and output the frequency of the corresponding frequency given signal to the chilled water pump inverter and cooling water pump inverter respectively controller. 2. The central air-conditioning variable temperature difference energy-saving control system according to claim 1, further comprising an industrial control computer connected to the frequency controller. 3. The central air-conditioning variable temperature difference energy-saving control system according to claim 1, wherein the frequency controller includes: The freezing temperature difference calculator connected with the chilled water supply temperature sensor and the chilled water return temperature sensor is used to store the freezing temperature difference setting value storage of the freezing temperature difference setting value changing with time, and the freezing temperature difference setting value memory connection, a freezing temperature difference setting value selector for selecting the corresponding freezing temperature difference setting value according to the current time, and being connected with the freezing temperature difference calculator, freezing temperature difference setting A fuzzy controller that calculates the freezing temperature difference and the setting value of the freezing temperature difference and outputs a corresponding frequency given signal to the chilled water pump inverter; Also includes: a cooling temperature difference calculator connected to the cooling water supply temperature sensor and the cooling water return temperature sensor, a cooling temperature difference setting value memory for storing the cooling temperature difference setting value that changes with time, and the cooling temperature difference The set value memory is connected, the cooling temperature difference set value selector for selecting the corresponding cooling temperature difference set value according to the current time, and the cooling temperature difference calculator, the cooling temperature difference set value selector and the cooling water pump frequency converter are connected and A fuzzy controller that can calculate and output a corresponding frequency given signal to the cooling water pump inverter according to the current cooling temperature difference and the set value of the cooling temperature difference. 4. The central air-conditioning variable temperature difference energy-saving control system according to claim 1, wherein the frequency controller is realized by a programmable logic controller.

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