WO2010021591A1

WO2010021591A1 - Power factor correcting arrangement and method of correcting power factor

Info

Publication number: WO2010021591A1
Application number: PCT/SG2008/000304
Authority: WO
Inventors: Hong Yew Mun; Wei Chong Low
Original assignee: Aztech Technologies Pte Ltd
Current assignee: Aztech Technologies Pte Ltd
Priority date: 2008-08-21
Filing date: 2008-08-21
Publication date: 2010-02-25
Anticipated expiration: 2011-02-21

Abstract

A power factor correcting arrangement and a method of correcting power factor are provided. The power factor correcting arrangement includes a first module configured to be coupled to a power supply line, the first module including: a current sensor for measuring a supply current provided by the power supply line; and a transmitter for transmitting wirelessly a parameter of the measured supply current; and a second module configured to be coupled to a power supply and to measure a supply voltage provided by the power supply, the second module including: a receiver for receiving wirelessly the parameter of the measured supply current from the first module; a plurality of electrical components configured to correct the power factor; a processor for determining a phase difference between the measured supply voltage and the measured supply current, and determining the electrical components of the plurality of electrical components to be used for correcting the power factor based on the measured supply current and the determined phase difference between the measured supply voltage and the measured supply current.

Description

Power Factor Correcting Arrangement and Method of Correcting Power Factor

Technical Field

[0001] Embodiments relate generally to a power factor correcting arrangement and a method of correcting power factor.

Background

[0002] Electrical power is a main source of energy. Alternating current electrical power is characterized by a phase relationship between a current and a voltage. Current lagging the voltage results from inductive loads, while current leading the voltage results from capacitive loads. [0003] Generally, power factor is used to measure the phase relationship between the current and the voltage. Power factor is a ratio of real power to apparent power. Real power is associated with power consumed by the loads in the power circuit. Apparent power is the product of voltage and current, but apparent power does not transfer electrical power to the loads. [0004] The power factor is usually less than one for a circuit having capacitive or inductive loads. In such cases, there is a possibility that apparent power may be higher than real power. Since the costs of delivering power determine power utility rates, delivering higher apparent power can increase the power utility rates and can lead to a higher utility cost. [0005] Further, in a circuit having capacitive or inductive loads, power lines may carry more current than necessary to provide power to portions of a power distribution network having capacitive or inductive loads. The additional current may result in additional real power loss. [0006] Therefore, it is desirable to provide a power factor correcting arrangement and a method of correcting power factor to correct the power factor to an optimum value (e.g. unity or a user-defined value), which can reduce apparent power and minimize power consumption.

Summary

[0007] hi an embodiment, there is provided a power factor correcting arrangement, including: a first module configured to be coupled to a power supply line, the first module including: a current sensor for measuring a supply current provided by the power supply line; and a transmitter for transmitting wirelessly a parameter of the measured supply current; and a second module configured to be coupled to a power supply and to measure a supply voltage provided by the power supply, the second module including: a receiver for receiving wirelessly the parameter of the measured supply current from the first module; a plurality of electrical components configured to correct the power factor; a processor for determining a phase difference between the measured supply voltage and the measured supply current, and determining the electrical components of the plurality of electrical components to be used for correcting the power factor based on the measured supply current and the determined phase difference between the measured supply voltage and the measured supply current.

[0008] In another embodiment, there is provided a method of correcting power factor, the method including: measuring a supply current and a supply voltage of a power supply; determining a phase difference between the measured supply voltage and the measured supply current; connecting an electrical component of a plurality of electrical components to the power supply; determining if a value of the supply current is reduced and if the phase difference is in a same direction; disconnecting the electrical component if the value of the supply current is not reduced or if the phase difference is not in the same direction; and connecting a next electrical component of the plurality of electrical component and determining if the value of the supply current is reduced and if the phase difference is in the same direction for the next electrical component to determine if the next electrical component is to be connected or disconnected.

Brief Description of the Drawings

[0009] hi the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention, hi the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0010] Figure 1 shows a schematic diagram of an exemplary installation of a power factor correcting arrangement. [0011] Figure 2 shows a schematic diagram of a Current Sensing Part (CSP). [0012] Figure 3 shows a schematic diagram of a Mains Plug-in Part (MPP). [0013] Figure 4 shows a flowchart of an exemplary process of correcting power factor.

Detailed Description

[0014] Exemplary embodiments of a power factor correcting arrangement and a method of correcting power factor are described in detail below with reference to the accompanying figures. It will be appreciated that the exemplary embodiments described below can be modified in various aspects without changing the essence of the invention. [0015] The power factor correcting arrangement attempts to save power consumption of the premises by performing a power factor correction of the premises by monitoring the phase difference between an incoming current and a line voltage, and then correcting the phase difference with selective electrical components. The power factor correcting arrangement attempts to bring the power factor to an optimum value, thus minimizing unnecessary power loss. The optimum value of the power factor may include unity or a user-defined value. [0016] Figure 1 shows a schematic diagram of an exemplary installation of the power factor correcting arrangement 100. The power factor correcting arrangement 100 may be installed in premises such as an office space, a residential unit, and etc. The power factor correcting arrangement 100 may include two modules. The first module 102 is termed as a Current Sensing Part (CSP) and the second module 104 is termed as a Mains Plug-in Part (MPP). The CSP 102 may be coupled to a power supply line 106. For example, the CSP 102 can be hooked around an incoming live cable or a neutral cable. The MPP 104 may be configured to be coupled to a power supply. The power supply may be an AC Mains supply. For example, the MPP 104 can be plugged into a wall outlet 108 which is closest to an incoming power point. Alternatively, the MPP 104 may be installed permanently near a circuit breaker 110. Installing the MPP 104 as close as possible to the incoming power point or the circuit breaker 110 may ensure that the power factor is corrected accurately for the whole premise. [0017] Figure 2 shows a schematic diagram of the Current Sensing Part (CSP) 102. The CSP 102 may include a current sensor 202 for measuring a supply current (e.g. AC current) provided by the power supply line. The current sensor 202 may be in the form of a sensing coil in one embodiment. The current sensor 202 may be hooked around the power supply line 106, e.g. an incoming live cable or a neutral cable. The current sensor 202 may measure a zero crossover point of the supply current and/or a value of the supply current from time to time. The amount of voltage from the current sensor 202 may be used to gauge the value of the supply current running through the power supply line 106, and the waveform of the supply current may be used to detect the zero crossover point of the supply current. The zero crossover point of the supply current may include a zero crossover timing of the supply current. [0018] The current sensor 202 may include at least two parts 204. The at least two parts 204 of the current sensor 202 may form a ring-shaped structure. Each part 204 of the current sensor may be wound around with wire 206. The at least two parts 204 of the current sensor 202 maybe made of electrically conductive material, e.g. metal. [0019] The CSP 102 may also include a transmitter 208 for transmitting wirelessly a parameter of the measured supply current. The parameter of the measured supply current may include the zero crossover point of the measured supply current and/or the value of the measured supply current. The transmitter 208 of the CSP 102 may include a radio frequency (RF) module 209 and an antenna 210. The parameter of the measured current may be transmitted wirelessly from the CSP 102 to the MPP 104 in real-time but at a predetermined time interval.

[0020] The CSP 102 may further include operational amplifiers 211, 212 coupled to the current sensor 202. The operational amplifier 211 may receive an analog electrical signal representing the supply current from the current sensor 202. The operational amplifiers 211, 212 may amplify the analog electrical signal and convert the analog electrical signal to square wave for extracting the zero crossover timing of the supply current. [0021] The CSP 102 may include a processor 214 coupled to the transmitter 208 and the operational amplifiers 211, 212. The processor 214 may be a microprocessor or a microcontroller. The extracted zero crossover timing may be sent from the operational amplifier 212 to the processor 214. The processor 214 may digitize the zero crossover timing of the supply current and the value of the supply current. The processor 214 may also perform packeting of the digital data having the zero crossover timing of the supply current and the value of the supply current. The processor 214 may then send an instruction signal to the transmitter 208 to transmit wirelessly the digital data to the MPP 104. [0022] The CSP may include a rectifying and decoupling module 215 coupled to the operational amplifier 211 and the processor 214. The CSP 102 may also include a memory 216. The memory 216 may be non-volatile. The memory 216 may be an EEPROM (electrically erasable programmable read-only memory), a flash memory, and etc. The memory 216 may store a digital identification of the CSP 102. The memory 216 may also store a digital identification of the MPP 104. The memory 216 may be coupled to the processor 214.

[0023] The CSP 102 may further include rechargeable batteries (not shown) which provide power to the CSP 102. The current sensor 202 of the CSP 102 may convert electromagnetic field from the power supply line 106 into power to charge the rechargeable batteries (not shown) and/or to provide power to the CSP 102. [0024] The CSP 102 may also include a solar panel (not shown) for absorbing light and converting light energy into power to charge the batteries and to provide power to the CSP 102. [0025] Figure 3 shows a schematic diagram of the Mains Plug-in Part (MPP) 104. The MPP 104 may measure a supply voltage (e.g. AC line voltage) provided by the power supply (e.g. AC Mains supply) 302. The MPP 104 may monitor a zero crossover point of the supply voltage and/or a value of the supply voltage from time to time. The zero crossover point of the measured supply voltage may include a zero crossover timing of the measured supply voltage.

[0026] The MPP 104 may include a receiver 304 for receiving wirelessly the parameter of the measured supply current from the transmitter 208 of the CSP 102. The receiver 304 of the MPP 104 may include a RF module 305 and an antenna 306. [0027] The MPP 104 may include a plurality of electrical components 308 configured to correct the power factor. For inductive loads, the plurality of electrical components 308 may be capacitors. For capacitive loads, the plurality of electrical components 308 may be inductors. In other embodiments, the plurality of electrical components 308 may be a combination of inductors and capacitors. For illustration purposes, capacitors are shown as the electrical components 308 in Figure 3.

[0028] The MPP 104 may also include a processor 310 for determining a phase difference between the measured supply voltage and the measured supply current, and for determining the electrical components 308 of the plurality of electrical components 308 to be used for correcting the power factor based on the measured supply current and the determined phase difference between the measured supply voltage and the measured supply current. A parameter of the measured voltage may include the zero crossover point of the measured supply voltage and/or the value of the measured supply voltage. The processor 310 may be coupled to the receiver 304. The processor 310 may be a microprocessor or a microcontroller

[0029] The MPP 104 may further include a switch 312 for each of the plurality of electrical components 308 for selectively coupling each of the plurality of electrical components 308 to the power supply 302. The switch 312 for each of the plurality of electrical components 308 may be coupled to the processor 310 and to the power supply 302. The switch 312 may couple the respective electrical component 308 to the power supply 302 in response to an instruction signal received from the processor 310. [0030] Each of the plurality of electrical components 308 may have a different value. The different values of the plurality of electrical components 308 may be powers of a base value. Alternatively, the different values of the plurality of electrical components 308 may be multiples of a base value.

[0031] The MPP 104 may also include a memory 314. The memory 314 may be nonvolatile. The memory 314 may be an EEPROM (electrically erasable programmable read- only memory), a flash memory, and etc. The memory 314 may store a digital identification of the MPP 104. The memory 314 may also store a digital identification of the CSP 102. The memory 314 may be coupled to the processor 310. The MPP 104 may further include a transformer 316 coupled to the power supply 302 and the processor 310. The transformer 316 may be a step-down transformer. [0032] The MPP 104 may include a plurality of light emitting diodes (LEDs) 318. A voltage V_cc 320 may be supplied to the LEDs 318. The LEDs 318 may indicate that the CSP 102 is within a communication range of the MPP 104. The LEDs 318 may also indicate that the power factor reaches an optimum value. The optimum value of the power factor may include unity or a user-defined value. The LEDs 318 may be coupled to the processor 310 via a respective resistor 322.

[0033] During the operation of the power factor correcting arrangement 100, as shown in Figure 1, the CSP 102 when in operation may send a beacon signal wirelessly to the MPP 104 with the transmitter 210. The MPP 104 when in operation may detect the beacon signal from the CSP 102 with the receiver 306. Upon receiving wirelessly the beacon signal from the CSP 102, the MPP 104 may update a status to display "Link Up" using the LEDs 318, which indicates that the CSP 102 is in a communication range of the MPP 104 and that the beacon signal from the CSP 102 is successfully detected. 8 000304

[0034] The CSP 102 may be configured that the transmitter 210 sends a beacon signal for a predetermined 'X' amount of time interval (e.g. 10 seconds) in order to keep the "Link Up" status on the MPP 104. The MPP 104 may be configured to keep the "Link Up" status for a period longer than the predetermined 'X' amount of time interval, e.g. more than twice of the predetermined 'X' amount of time interval, since the last received beacon signal. Failure to receive the beacon signal from CSP 102 within this time frame, the MPP 104 may change and display the status as "Link Down" using the LEDs 318. [0035] During normal operation, the current sensor 202 of the CSP 102 may measure the zero crossover point of the supply current (e.g. AC line current) in real-time to determine a zero crossover timing of the supply current. The current sensor 202 of the CSP 102 may also measure the value of the supply current. The CSP 102 may then send the zero crossover point of the supply current and/or the value of the measured supply current wirelessly to the MPP 104 with the transmitter 210. The zero crossover point of the supply current may include the zero crossover timing of the supply current. [0036] During normal operation, the MPP 104 may measure the zero crossover point of the supply voltage (e.g. AC line voltage) in real-time to determine a zero crossover timing of the supply voltage. The MPP 104 may measure the value of the supply voltage. The MPP 104 may also monitor a periodic cycle time at the power outlet 108 the MPP 104 may be plugged into or at the location the MPP 104 may be permanently installed. [0037] After receiving the zero crossover timing of the supply current from the CSP 102 with the receiver 306, the processor 310 of the MPP 104 may compare the zero crossover timing of the supply current with the zero crossover timing of the supply voltage. Using the periodic cycle time, the processor 310 of MPP 104 may calculate and determine the phase difference between the supply current and the supply voltage. [0038] After determining the phase difference between the supply current and the supply voltage, the processor 310 of the MPP 104 may determine the electrical component(s) of the plurality of the electrical components to be connected across the power supply line 106 either through calculation or some search algorithms, one of which will be described in the following. The processor 310 of the MPP 104 may determine the electrical component(s) of the plurality of the electrical components to correct the power factor to an optimum value and/or to minimize power consumption. When the optimum power factor is achieved, the LEDs 318 of the MPP 104 may light-up to indicate that the power factor reaches an optimum value. The optimum value of the power factor may include unity or a user-defined value. The MPP 104 may monitor the supply current from time to time and may adjust the electrical component(s) of the plurality of the electrical components to be connected across the power supply line 106 to correct the power factor, if necessary.

[0039] Figure 4 shows a flowchart 400 of an exemplary process of correcting the power factor. At 402, a supply current and a supply voltage of a power supply may be measured. At 404, a phase difference between the measured supply voltage and the measured supply current may be determined. At 406, an electrical component of a plurality of electrical components may be connected to the power supply.

[0040] At 408, it may be determined if a value of the supply current is reduced and if the phase difference is in a same direction. If the plurality of electrical components is capacitors, it may be determined at 408 if the phase difference is in a same lagging 00304

direction. If the plurality of electrical components is inductors, it may be determined at 408 if the phase difference is in a same leading direction. If the plurality of electrical components is a combination of capacitors and inductors, the direction of the phase difference may depend on the type of electrical component connected to the power supply at 406.

[0041 ] At 410, if the value of the supply current is reduced and if the phase difference is in a same direction, the electrical component may remain connected. At 412, if the value of the supply current is not reduced or if the phase difference is not in the same direction, the electrical component may be disconnected. [0042] After 410 or 412, the process returns to 406, whereby a next electrical component of the plurality of electrical components may be connected and it may be determined if the value of the supply current is reduced and if the phase difference is in the same direction for the next capacitor to determine if the next electrical component is to be connected or disconnected. The process may repeat 406-410 or 406-412 for all the electrical components to determine an optimum combination of the electrical component(s) for correcting the power factor to an optimum value. The optimum value of the power factor may include unity or a user-defined value.

[0043] Whenever there is a change in the supply current or there is a current phase change, the process of correcting the power factor may be carried out to determine the optimum load for correcting the power factor.

[0044] While embodiments of the invention have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

ClaimsWhat is claimed is:

1. A power factor correcting arrangement, comprising: a first module configured to be coupled to a power supply line, the first module comprising: a current sensor for measuring a supply current provided by the power supply line; and a transmitter for transmitting wirelessly a parameter of the measured supply current; and a second module configured to be coupled to a power supply and to measure a supply voltage provided by the power supply, the second module comprising: a receiver for receiving wirelessly the parameter of the measured supply current from the transmitter of the first module; a plurality of electrical components configured to correct the power factor; a processor for determining a phase difference between the measured supply voltage and the measured supply current, and determining the electrical components of the plurality of electrical components to be used for correcting the power factor based on the measured supply current and the determined phase difference between the measured supply voltage and the measured supply current.

2. The power factor correcting arrangement of claim 1, wherein the parameter of the measured supply current comprises a zero crossover point of the measured supply current and/or a value of the measured supply current.

3. The power factor correcting arrangement of claim 2, wherein the zero crossover point of the measured supply current comprises a zero crossover timing of the measured supply current.

4. The power factor correcting arrangement of any one of claims 1 to 3, wherein a parameter of the measured supply voltage comprises a zero crossover point of the measured voltage and/or a value of the measured supply voltage.

5. The power factor correcting arrangement of claim 4, wherein the zero crossover point of the measured supply voltage comprises a zero crossover timing of the measured supply voltage.

6. The power factor correcting arrangement of any one of claims 1 to 5, wherein the second module further comprises a switch for each of the plurality of electrical components of the second module for selectively coupling each of the plurality of electrical components to the power supply.

7. The power factor correcting arrangement of claim 6, wherein the switch for each of the plurality of electrical components is coupled to the processor of the second module and to the power supply.

8. The power factor correcting arrangement of claims 6 or 7, wherein the switch couples the respective electrical component to the power supply in response to an instruction signal received from the processor of the second module.

9. The power factor correcting arrangement of any one of claims 1 to 8, wherein each of the plurality of electrical components of the second module has a different value.

10. The power factor correcting arrangement of claim 9, wherein the different values of the plurality of electrical components are powers of a base value.

11. The power factor correcting arrangement of claim 9, wherein the different values of the plurality of electrical components are multiples of a base value.

12. The power factor correcting arrangement of any one of claims 1 to 11, wherein the plurality of electrical components comprise capacitors.

13. The power factor correcting arrangement of any one of claims 1 to 11, wherein the plurality of electrical components comprise inductors.

14. The power factor correcting arrangement of any one of claims 1 to 11₅ wherein the plurality of electrical components comprise capacitors and inductors.

15. The power factor correcting arrangement of any one of claims 1 to 14, wherein the second module further comprises a transformer coupled to the power supply and the processor of the second module.

16. The power factor correcting arrangement of any one of claims 1 to 15, wherein the second module further comprises a plurality of light emitting diodes

(LEDs).

17. The power factor correcting arrangement of claim 16, wherein the LEDs indicate that the first module is within a communication range of the second module.

18. The power factor correcting arrangement of claims 16 or 17, wherein the LEDs indicate that the power factor reaches an optimum value.

19. The power factor correcting arrangement of claim 18 , wherein the optimum value of the power factor comprises unity or a user-defined value.

20. The power factor correcting arrangement of any one of claims 1 to 19, wherein the transmitter of the first module comprises a radio frequency module and an antenna.

21. The power factor correcting arrangement of any one of claims 1 to 20, wherein the receiver of the second module comprises a radio frequency module and an antenna.

22. The power factor correcting arrangement of any one of claims 1 to 21 , wherein the first module has a digital identification.

23. The power factor correcting arrangement of any one of claims 1 to 22, wherein the second module has a digital identification.

24. The power factor correcting arrangement of claims 22 or 23 , wherein the digital identification of the first module and the digital identification of the second module are stored in a memory of the first module and a memory of the second module.

25. The power factor correcting arrangement of any one of claims 1 to 24, wherein the first module further comprises rechargeable batteries.

26. The power factor correcting arrangement of any one of claims 1 to 25, wherein the current sensor of the first module converts electromagnetic field from the power supply line into power to charge the rechargeable batteries and to provide power to the first module.

27. The power factor correcting arrangement of any one of claims 1 to 26, wherein the current sensor of the first module comprises at least two parts, each part being wound around with wire.

28. The power factor correcting arrangement of claim 27, wherein the at least two parts of the current sensor form a ring-shaped structure.

29. The power factor correcting arrangement of claims 27 or 28, wherein the at least two parts of the current sensor comprise metal.

30. The power factor correcting arrangement of any one of claims 1 to 29, wherein the first module further comprises operational amplifiers coupled to the current sensor.

31. The power factor correcting arrangement of claim 30, wherein the first module further comprises a processor coupled to the operational amplifiers.

32. The power factor correcting arrangement of claims 30 or 31 , 8 000304

wherein the first module further comprises a rectifying and decoupling module coupled to the operational amplifiers and the processor.

33. The power factor correcting arrangement of any one of claims 1 to 32, wherein the first module further comprises a solar panel for absorbing light and converting light energy into power to charge the rechargeable batteries and to provide power to the first module.

34. A method of correcting power factor, the method comprising: measuring a supply current and a supply voltage of a power supply; determining a phase difference between the measured supply voltage and the measured supply current; connecting an electrical component of a plurality of electrical components to the power supply; determining if a value of the supply current is reduced and if the phase difference is in a same direction; disconnecting the electrical component if the value of the supply current is not reduced or if the phase difference is not in the same direction; and connecting a next electrical component of the plurality of electrical components and determining if the value of the supply current is reduced and if the phase difference is in the same direction for the next capacitor to determine if the next electrical component is to be connected or disconnected.

35. The method of claim 34, further comprising: transmitting wirelessly a parameter of the measured current from a first module to a second module; and receiving wirelessly the parameter of the measured current.

36. The method of claim 35, wherein the parameter of the measured current comprises a zero crossover point of the measured current and/or a value of the measured current.

37. The method of claim 36, wherein the zero crossover point of the measured supply current comprises a zero crossover timing of the measured supply current.

38. The method of any one of claims 34 to 37, wherein a parameter of the measured voltage comprise a zero crossover point of the measured voltage and/or a value of the measured voltage.

39. The method of claim 38, wherein the zero crossover point of the measured supply voltage comprises a zero crossover timing of the measured supply voltage.

40. The method of any one of claims 34 to 39, wherein each of the plurality of electrical components is selectively connected to the power supply via a respective switch.

41. The method of claim 40, wherein the switch for each of the plurality of electrical components is coupled to a processor of the second module and to the power supply.

42. The method of any one of claims 34 to 41 , wherein connecting each of the plurality of electrical components to the power supply comprises sending an instruction signal from the processor of the second module to the respective switch.

43. The method of any one of claims 34 to 42, wherein each of the plurality of electrical components has a different value.

44. The method of claim 43 , wherein the different values of the plurality of electrical components are powers of a base value.

45. The method of claim 44, wherein the different values of the plurality of electrical components are multiples of a base value.

46. The method of any one of claims 34 to 45, wherein the plurality of electrical components comprise capacitors.

47. The method of any one of claims 34 to 45, wherein the plurality of electrical components comprise inductors.

48. The method of any one of claims 34 to 45, wherein the plurality of electrical components comprise capacitors and inductors.