FR2966302A1 - CONTROL SYSTEMS AND METHODS - Google Patents

Abstract

A control system (1) comprising a management system (10) arranged to provide at least one control signal for at least one AC motor (13a-13d); a clock generator (15) arranged to generate first and second clock signals alternating between an inactive state and an active state; a power generator (12a-12d) arranged to receive the first and second clock signals and generate a power supply for the motor when the control signal indicates that the motor is to operate. The generated power supply is at a first voltage level when the first clock signal is active, at a second level when the first signal is inactive and the second signal is active, and at an intermediate level when the first and second signals are active. are inactive. Method of operating such a control system

Description

CONTROL SYSTEMS AND METHODS

The present invention relates to control systems. The invention is particularly, but not exclusively, applicable to building management systems (BMS), that is, systems for managing devices that control the environment inside a building. More particularly, but not exclusively, the invention relates to controlling actuators in a building management system. AC motors are commonly used in a building management system, such as actuators to control the position of valves, dampers and other small building management system elements. AC motors of 24 V 50/60 Hz are frequently used. Historically, commercial buildings, such as office buildings, include a transformer to provide a 24 V 50/60 Hz AC power supply to operate various devices such as electrical, exhaust, heating and electrical systems. cooling in the building. This power supply can be used by a building management system to operate AC motors, by controlling AC power to the motors using low cost triac switches.

However, in more recent building designs, such a transformer is no longer needed and therefore no 24 V 50/60 Hz AC power supply is available for use by the building management system. One solution is to provide a transformer specifically for use by the building management system to operate the motors. Nevertheless, this is expensive since additional parts are needed and this is also inefficient in terms of energy use. The present invention aims at alleviating the aforementioned problems.

According to a first aspect of the invention, there is provided a control system comprising: a management system arranged to provide at least one control signal for at least one AC motor; a clock generator arranged to generate first and second clock signals alternating between an inactive state and an active state, the first clock signal being in the inactive state when the second clock signal is in the state active; a power generator arranged to receive the first and second clock signals of the clock generator, and further arranged to generate a power supply for the AC motor when the control signal of the management system indicates that the motor AC power must work; wherein the power supply generated by the power generator is at a first voltage level when the first clock signal is in the active state; wherein the power supply generated by the power generator is at a second voltage level when the first clock signal is in the idle state and the second clock signal is in the active state; and wherein the power supply generated by the power generator is at an intermediate voltage level between the first and second voltage levels when the first and second clock signals are in the inactive state. The management system controls the building's internal environment by providing control signals for AC motors, which can be used, for example, as actuators in a building management system. A clock generator generates first and second clock signals, which are used by the power generator to create a power supply for the AC motor when the control system indicates that the motor is to operate. The first and second clock signals alternate between an active state and an inactive state (for example, a high state and a low state). When the first clock signal is in the active state, the power supply is supplied at the first voltage level (for example, a positive voltage level). On the other hand, if the second clock signal is in the active state and the first clock signal is in the inactive state, the power supply is supplied at the second voltage level (for example, a negative voltage level ). Finally, if the first clock signal and the second clock signal are in the inactive state, the power supply is supplied at the intermediate voltage level (for example, an electrical ground). In this manner, the power generator is capable of using the first and second clock signals to provide a power supply that changes between a negative voltage level, a ground voltage level, and a positive voltage level. This is very similar to a sinusoidal AC power supply, which allows in particular to provide an output torque of the AC motor, and a heating inside the AC motor, similar to what is generated by an AC power supply. A power supply can thus be provided to operate the AC motor, without the need for an AC transformer directly supplying AC power. Preferably, the AC motor is intended to use an AC power supply of 24 V 50/60 Hz. In this case, the first voltage level can be +28 V, the second voltage level can be -28 V and the intermediate voltage level can be 0 V. The AC motor can be for example a unidirectional motor or a bidirectional motor. In the case of a bidirectional motor, the first and second power supplies can be generated for example on the basis of the first and second control signals of the management system, or from a single control signal with multiple states. Preferably, the second clock signal is in the inactive state when the first clock signal is in the active state. More preferably, the first and second clock signals are offset by half a period.

Preferably, the first clock signal is in the active state for a period shorter than the period during which it is in the idle state. More preferably, the second clock signal is in the active state for a period shorter than the period in which it is in the idle state.

This allows the first and second clock signals to be simultaneously in the inactive state before and after one of them is in the active state. Preferably, the first and second clock signals are in the idle state for 55 to 65% of a period. More preferably, the first and second clock signals are in the idle state for 60% of a period.

Advantageously, the management system is arranged to provide a plurality of control signals which are each associated with a respective AC motor. Preferably, the system comprises a plurality of power generators which are each associated with a respective AC motor. This allows the management system to control a plurality of AC motors. Preferably, the system further comprises a signal generator arranged to receive the control signal or control signals of the management system and the first and second clock signals of the clock generator, and further arranged to transmit the first and second clock signals to a power generator when the control signal of the management system associated with the respective AC motor indicates that the motor is to operate. In particular, this makes it possible to use a single clock generator for controlling a plurality of motors. Advantageously, the control system is a system for controlling the internal environment of a building. This constitutes a particular field of application of the invention. According to a second aspect of the invention, there is provided a method of operating a control system comprising a management system arranged to provide at least one control signal for at least one AC motor, the method comprising the steps of: generating first and second clock signals alternating between an inactive state and an active state, the first clock signal being in the inactive state when the second clock signal is in the active state; generating a power supply for the AC motor based on the first and second clock signals when the control signal from the management system indicates that the AC motor is to operate; wherein the power supply is at a first voltage level when the first clock signal is in the active state; wherein the power supply is at a second voltage level when the first clock signal is in the idle state and the second clock signal is in the active state; and wherein the power supply is at an intermediate voltage level between the first voltage level and the second voltage level when the first and second clock signals are in the inactive state. Preferably, the second clock signal is in the inactive state when the first clock signal is in the active state. Preferably, the first clock signal is in the active state for a period shorter than that in which it is in the idle state. Advantageously, the management system is arranged to provide a plurality of control signals which are each associated with a respective AC motor. Advantageously, the method further comprises the steps of generating a power supply for each AC motor based on the first and second clock signals when the associated control signal indicates that the AC motor is to be powered. function. Advantageously, the control system is intended to control the internal environment of a building. It should be appreciated that features described with respect to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate features described with respect to the apparatus of the invention and vice versa. Embodiments of the present invention will be described hereinafter by way of example only, with reference to the appended figures in which: FIG. 1 is a diagram of a building management system according to a first embodiment of FIG. the invention; Figure 2 is a diagram of a building management system according to a second embodiment of the invention; Fig. 3a is a graph of a first clock signal provided by the clock generator of Fig. 1 or 2; Fig. 3b is a graph of a second clock signal provided by the signal generator of Fig. 1 or 2; Figure 4 is a circuit diagram of the signal generator of Figure 1 or 2; Fig. 5 is a circuit diagram of the power generator of Fig. 1 or 2; FIG. 6 is a graph of the output of the power generator of FIG. 3. A building management system (BMS) according to a first embodiment of the invention is represented in FIG. 1. The management system of FIG. Building 1 includes a management system 10. The management system 10 receives data relating to states in the building (e.g., temperature in different areas of the building), and control devices in the building (e.g. air conditioning units), in order to control the environment in the building on the basis of parameters set by a user. The building management system 1 further comprises a signal generator 11, which receives control signals from the management system 10. The signal generator 11 also receives clock signals from a clock generator 15. signal generator 11 generates drive signals and sends them to power generators 12a, 12b, 12c, 12d. The power generators 12a, 12b, 12c, 12d then supply power to the AC motors 13a, 13b, 13c and 13d, respectively. The AC motors 13a, 13b, 13c and 13d are unidirectional motors for using a 24 V 50/60 Hz AC power supply, each of the motors (and other elements of the building management system 1) also being connected to an electrical ground (not shown). In the embodiment of FIG. 1, the management system 10 provides control signals for respectively controlling the operation of each of the AC motors 13a, 13b, 13c and 13d. The control signals provided by the management system 10 are logic signals respectively comprising a low state of 0 V and a high state of 3.3 V. Those skilled in the art may realize that other logic employing different levels logic up and down may also be applicable to the invention. In addition, the clock generator 15 provides first and second clock signals, which are logic signals respectively having a low state of 0 V and a high state of 3.3 V. The four control signals of the control system management 10 are deployed by the signal generator 11, using the first and second clock signals provided by the clock generator 15, in four pairs of drive signals, as will be described in detail below. The drive signals are logic signals respectively having a low state of 0 V and a high state of 3.3 V. Each of the power generators 12a, 12b, 12c and 12d receives one of the signal pairs of drive signal generator 11, and uses it to create a power supply with a low level of -28 V and a high level of 28 V, as will be described in detail below. This power supply is supplied to the respective AC motor 13a, 13b, 13c or 13d of the power generator. The management system 10 is thus able to control the AC motors 13a, 13b, 13c and 13d through the signal generator 11 and the power supply generators 12a, 12b, 12c and 12d.

A building management system according to a second embodiment of the invention is shown in FIG. 2. Like the building management system 1 of FIG. 1, the building management system 2 of FIG. management system 10, a clock generator 15, a signal generator 11 which receives signals from the management system 10 and the clock generator 15, and the power supply generators 12a, 12b, 12c, 12d. Nevertheless, instead of the four AC unidirectional motors 13a, 13b, 13c and 13d, the building management system 2 of Figure 2 comprises two AC bidirectional motors 14a and 14b. Each of the AC motors 14a and 14b is intended to use a 24V 50/60 Hz power supply, and is also connected to an electrical ground (not shown). Nevertheless, since the AC motors 14a and 14b are bidirectional, each of them can use two power supplies to operate in any direction. As a result, the AC motor 14a receives power from the power generators 12a and 12b, and the AC motor 14b receives power from the power generators 12c and 12d. Thus, as for the building management system 1 of FIG. 1, the management system 10 of the building management system 2 of FIG. 2 is able to control the AC motors 14a and 14b by means of the generator of FIG. signal 11 and power generators 12a, 12b, 12c and 12d. The operation of the embodiment of Figure 1 will now be described in detail. The embodiment of Fig. 2 functions similarly, except that the power supply is supplied to the two AC bidirectional motors 14a and 14b instead of the four AC unidirectional motors 13a, 13b, 13c and 13d. As discussed above, the clock generator 15 provides first and second clock signals to the signal generator 11. The first and second clock signals are respectively shown in Figures 3a and 3b. (Although the clock signals are logic signals having a low state of 0 V, for the sake of clarity the x-axes of FIGS. 3a and 3b are positioned below 0 V.) Each clock signal has a frequency 50 Hz and a duty cycle of 40%; in other words, the signals are alternately high for a period of 12 ms and low for a period of 8 ms. The first and second signals are shifted by a period of 10 ms. Thus, as can be seen, each clock signal is in a high state while the other is in a low state, the two clock signals being in a low state simultaneously for a period of 2 ms of n '. whatever side of the high state. The signal generator 11 is shown in detail in FIG. 3. The signal generator 11 comprises a complex programmable logic device (CPLD) 20. The signal generator 11 uses the first and second clock signals of the clock generator 15 (PB4 and PB5 in Fig. 3) to deploy the four control signals (PBO to PB3) of the management system 10 into four pairs of control signals (Chop_11 and Chop_hl to Chop_14 and Chop_h4). The control signal PBO is deployed in drive signals Chop_11 and Chop_hl as follows: PBO Chop_ 11 Chop_hl Low Low Low High PB4 PB5 In other words, when the control signal PBO is low, the two power signals Chop_11 and Chop_hl are low. When the control signal PBO is high, the drive signal Chop_11 provides the first clock signal of PB4, while the drive signal Chop_hl provides the second clock signal of PB5. The other pairs of drive signals are generated similarly from the first and second clock signals, as follows: PB 1 Chop_ 12 Chop_h2 Low Low Low High PB4 PB5 PB2 Chop_13 Chop_h3 Low Low Low High PB4 PB5 PB3 Chop_14 Chop_h4 Low Low Low High PB4 PB5 The power generator 12a is shown in detail in Figure 5. The power generators 12b, 12c and 12c are of identical construction. The supply generator 12a comprises in particular complementary MOSFET transistors (N / P) 37 and 38. The supply generator 12a receives the pair of drive signals Chop_11 and Chop_hl (31 and 32 in FIG. The power generator 12a is also connected to a -28 VDC power supply 34 and +28 VDC power supply. The power supply generator 12a delivers a power supply 36 to the AC motor 13a. The gate of transistor 37 is connected (through some other components) to the Chop_11 drive signal 31 of signal generator 11. The drain of transistor 37 is connected to the -28 VDC supply 34. The source of transistor 37 is connected (through some other components) to the power supply 36. The gate of the transistor 38 is connected (through some other components) to the drive signal Chop_hl 32 of the signal generator 11. The drain of the Transistor 38 is connected (through some other components) to the power supply 36. The source of transistor 38 is connected to the +28 VDC power supply 35. The power generator 12a operates as follows. If the two drive signals Chop_11 31 and Chop_hl 32 are low, the transistors 37 and 38 are closed, and the power supply 36 does not deliver electricity. If the drive signal Chop_11 31 is high, the transistor 37 opens, by lowering the power supply 36 to the supply -28 VDC 34. Moreover, if the drive signal Chop_hl 32 is high, the transistor 38 opens, by raising the power supply 36 to the +28 VDC supply 35. (Due to the nature of the first and second clock signals PB4 and PB5, and the logic of the signal generator 11 it is not possible for the drive signals Chop_11 31 and Chop_hl 32 to be simultaneously high.) Thus, when the control signal PBO is low, the drive signals Chop_11 31 and Chop_hl 32 are low, and the power supply 36 does not deliver electricity. On the contrary, when the control signal PBO is high, the drive signals Chop_11 31 and Chop_hl 32 respectively provide the first and second clock signals PB4 and PB5. The power supply 36 when generated by the combination of the first and second clock signals PB4 and PB5 by the power generator 12a is shown in Figure 6. (For the sake of clarity, the x-axis of the FIG. 6 is positioned below -28 V.) As can be seen, the power supply 36 repeats the -28 V sequence for 8 ms (when the first clock signal PB4 is high and the second clock signal is clock PB5 is low), 0 V for 2 ms (when both clock signals PB4 and PB5 are low), +28 V for 8 ms (when the first clock signal PB4 is low and the second signal of PB5 clock is high), and 0 V for 2 ms (when both PB4 and PB5 clock signals are low). Although the power supply 36 does not accurately reflect a sinusoidal 24 VAC power supply, it is sufficiently similar to supply the AC motor 13a with electricity, providing output torque from the AC motor 13a, and heating at the same time. Inner of the AC motor 13a, as generated by a sinusoidal 24 VAC power supply. It can thus be seen that the clock generator 15, the signal generator 11 and the supply generators 12a, 12b, 12c and 12d in combination act on control signals of the management system 10 to supply power supplies intended for operating the AC motors 13a, 13b, 13c and 13d without the need for an AC transformer directly supplying a 24 VAC power supply. Although the present invention has been described and illustrated with reference to particular embodiments, one skilled in the art may realize that the invention lends itself to many different variations that are not specifically illustrated herein. For example, one skilled in the art may realize that the invention is equally applicable to embodiments providing power supplies to a larger number of motors. In addition, the invention applies to embodiments comprising a combination of unidirectional and bidirectional motors. Those skilled in the art may also realize that alternative forms of circuitry may be used. For example, MOSFET, P / P MOSFET, IGBT and / or bipolar N / N transistors, or any other class D output stage, may be used in place of the described N / P MOSFET transistors. Similarly, variations of an "H" bridge circuit may be used. In another example, the signal generator 11 and the clock generator 15 can be fully implemented using microprograms.

Claims (13)

REVENDICATIONS1. A control system (1) comprising: a management system (10) arranged to provide at least one control signal for at least one AC motor (13a, 13b, 13c, 13d); a clock generator (15) arranged to generate first and second clock signals alternating between an inactive state and an active state, the first clock signal being in the inactive state when the second clock signal is in the active state; a power generator (12a, 12b, 12c, 12d) arranged to receive the first and second clock signals of the clock generator, and further arranged to generate a power supply for the AC motor (13a, 13b) , 13c, 13d) when the control signal of the management system (10) indicates that the AC motor (13a, 13b, 13c, 13d) is to operate; wherein the power supply generated by the power generator (12a, 12b, 12c, 12d) is at a first voltage level when the first clock signal is in the active state; wherein the power supply generated by the power generator (12a, 12b, 12c, 12d) is at a second voltage level when the first clock signal is in the idle state and the second clock signal is in the active state; and wherein the power supply generated by the power generator (12a, 12b, 12c, 12d) is at an intermediate voltage level between the first and second voltage levels when the first and second clock signals are in the inactive state. 2. System (1) according to claim 1, wherein the second clock signal is in the inactive state when the first clock signal is in the active state. The system (1) of claim 1 or 2, wherein the first clock signal is in the active state for a period shorter than the period in which it is in the idle state. The system (1) according to any one of the preceding claims, wherein the management system (10) is arranged to provide a plurality of control signals which are each associated with an AC motor (13a, 13b, 13c). , 13d) respectively. 5. System (1) according to claim 4, comprising a plurality of power generators which are each associated with a respective AC motor (13a, 13b, 13c, 13d). The system (1) according to any one of the preceding claims, further comprising a signal generator (11) arranged to receive the control signal or control signals from the management system (10) and the first and second signals clock of the clock generator (15), and further arranged to transmit the first and second clock signals to a power generator (12a, 12b, 12c, 12d) when the control signal of the management system (10) associated with the respective AC motor (13a, 13b, 13c, 13d) indicates that the motor is to operate. 7. System (1) according to any one of the preceding claims, wherein the control system (1) is a system for controlling the internal environment of a building. 8. A method of operating a control system (1) comprising a management system (10) arranged to supply at least one control signal for at least one AC motor (13a, 13b, 13c, 13d), the method comprising the steps of: generating first and second clock signals alternating between an inactive state and an active state, the first clock signal being in the inactive state when the second clock signal is in the active state ; generating a power supply for the AC motor (13a, 13b, 13c, 13d) based on the first and second clock signals when the control signal of the management system (10) indicates that the alternating current (13a, 13b, 13c, 13d) shall operate; wherein the power supply is at a first voltage level when the first clock signal is in the active state, wherein the power supply is at a second voltage level when the first clock signal is in the inactive state and the second clock signal is in the active state; and wherein the power supply is at an intermediate voltage level between the first voltage level and the second voltage level when the first and second clock signals are in the inactive state. The method of claim 8, wherein the second clock signal is in the inactive state when the first clock signal is in the active state. The method of claim 8 or 9, wherein the first clock signal is in the active state for a period shorter than the period in which it is in the idle state. The method of any one of claims 8 to 10, wherein the management system (10) is arranged to provide a plurality of control signals each of which is associated with an AC motor (13a, 13b, 13c, 13d) respectively. The method of claim 11, further comprising the steps of generating a power supply for each AC motor (13a, 13b, 13c, 13d) based on the first and second clock signals when the signal associated control means that the AC motor (13a, 13b, 13c, 13d) must operate. 13. A method according to any one of claims 8 to 12, wherein the control system (1) is intended to control the internal environment of a building.