TWI586983B - Apparatus and method for detecting the operation of power supply in an electric utility - Google Patents

Description

Device and method for detecting whether power supply of utility electric power is abnormal

The present invention relates to a technique for detecting power supply to a utility industry, and more particularly to an apparatus and method for detecting whether an electrical power supply to a utility industry in parallel with a microgrid is abnormal.

The microgrid is mostly a three-phase power system consisting of a regenerative power supply, a load, and an energy storage unit. Its operation can be divided into commercial power (or public electric utility) parallel and island operation. When the mains supply is stable, the regenerative power supply, load, and energy storage unit operate normally in the microgrid connected in parallel with the mains; when the mains is abnormal, the microgrid will be disconnected from the mains to perform island operation, which will be performed by the energy storage unit and regeneration. The power source (or generator set) provides a source of power for the load to operate.

At the moment when the microgrid is disconnected from the mains, it is necessary to switch from the current control of the mains to the voltage control of the island operation. In the process of this mode switching, the detection of the abnormality of the mains is very important, and the abnormal judgment must require a considerable speed and accuracy. Therefore, it is necessary to develop a new detection technology for whether the mains power supply is abnormal, so as to adapt to the demand of the micro grid to switch between the mains parallel and the island operation mode.

To achieve this object, in accordance with an aspect of the present invention, an embodiment provides a device for detecting whether a power supply to a utility is abnormal, the power supply having a normal voltage waveform under normal conditions, the device comprising: The first comparator compares a reference voltage waveform with an immediate voltage waveform of the power supply and generates a first difference waveform; a weighting function generator generates a weighting function; a multiplier, the first The difference waveform is multiplied by a weighting function to obtain a second difference waveform; and an accumulator obtains an absolute value of the amplitude of the second difference waveform every predetermined time interval, And accumulating the absolute values of the amplitudes to obtain an accumulated difference value; and a second comparator comparing the accumulated difference value with a predetermined threshold value, and when the accumulated difference value exceeds the predetermined threshold value, determining the public power The power supply of the industry has been abnormal.

According to another aspect of the present invention, another embodiment provides a method for detecting whether a power supply to a utility is abnormal, the power supply having a normal voltage waveform under normal conditions, the method comprising the steps of: providing a reference voltage waveform; measuring an instantaneous voltage waveform of the power supply; comparing the instantaneous voltage waveform with the reference voltage waveform, and generating a first difference waveform; multiplying the first difference waveform by a weighting function to obtain a second difference waveform; obtaining an absolute value of the amplitude of the second difference waveform every predetermined time interval, and accumulating the absolute values of the amplitudes to obtain an accumulated difference; and when the accumulated difference reaches a predetermined value When the threshold is reached, it is determined that the power supply of the utility is abnormal.

According to another aspect of the present invention, another embodiment provides a method for detecting whether a power supply of a utility power is abnormal, the power supply having a normal current waveform under normal conditions, the method comprising the steps of: providing a a reference current waveform having an amplitude, a frequency, and a phase respectively equal to an amplitude, a frequency, and a phase of the normal current waveform; measuring an instantaneous current waveform of the power supply; comparing the instantaneous current waveform with the reference current waveform, and generating a first difference a value waveform; multiplying the first difference waveform by a weighting function to obtain a second difference waveform; obtaining an absolute value of the amplitude of the second difference waveform every predetermined time interval, and obtaining the absolute amplitude The values are accumulated to obtain an accumulated difference; and when the accumulated difference reaches a predetermined threshold, it is determined that the power supply of the utility is abnormal.

In an embodiment, the weighting function Where t represents time, Represents the angular frequency and k represents the weighting constant.

In an embodiment, the weighting constant k is between 1 and 100.

100‧‧‧Detection device

110‧‧‧First comparator

120‧‧‧weighted function generator

130‧‧‧Multiplier

140‧‧‧ accumulator

150‧‧‧Second comparator

200‧‧‧Detection method

S210~S260‧‧‧Steps

300‧‧‧Detection method

S310~S360‧‧‧Steps

FIG. 1 is a block diagram of a detecting apparatus according to an embodiment of the present invention.

Figure 2 is a waveform diagram of the instantaneous voltage waveform and the reference voltage waveform when the utility power supply is abnormal.

FIG. 3 is a waveform diagram of the first difference waveform and the second difference waveform when the utility power supply is abnormal.

FIG. 4 is a block diagram of a detection method according to an embodiment of the present invention for detecting whether an abnormality occurs in a power supply of a utility.

FIG. 5 is a block diagram of a detection method according to an embodiment of the present invention for detecting whether an abnormality occurs in a power supply of a utility.

For a more detailed understanding and understanding of the features, objects and functions of the present invention, the present invention will be described in detail with reference to the drawings. In all of the specification and the drawings, the same component numbers will be used to designate the same or similar components.

In the description of the various embodiments, when an element is described as "above/on" or "below/under" another element, it is meant to be directly or indirectly above or below the other element. , which may contain other elements set in between; the so-called "directly" means that no other intermediary elements are set in between. The descriptions of "Upper/Upper" or "Bottom/Lower" are based on the schema, but also include other possible direction changes. The so-called "first", "second", and "third" are used to describe different elements that are not limited by such predicates. For the convenience and clarity of the description, the thickness or size of each element in the drawings is expressed in an exaggerated or omitted or schematic manner, and the size of each element is not completely the actual size.

FIG. 1 is a block diagram of a detecting apparatus 100 according to an embodiment of the present invention for detecting whether an abnormality occurs in a power supply of a utility industry (or a utility power). Since the utility industry has a normal voltage waveform under normal conditions, we will set a reference voltage waveform Vf to be the same as the normal voltage waveform; that is, the reference voltage waveform Vf is used to simulate The normal voltage waveform of the power supply of the utility industry, and its amplitude, frequency, and phase are equal to the amplitude, frequency, and phase of the normal voltage waveform, respectively. As shown in FIG. 1 , the detecting apparatus 100 includes a first comparator 110 , a weighting function generator 120 , a multiplier 130 , an accumulator 140 , and a second comparator 150 . In this embodiment, we will first use appropriate electrical measurements. The quantity means to obtain the instantaneous voltage waveform Vg of the power supply of the utility.

In the case that the utility power supply power normally, the instantaneous voltage waveform Vg will be the same as the reference voltage waveform Vf; however, when the power supply of the utility power is abnormal, the instantaneous voltage waveform Vg will be different from the reference voltage waveform. Vf. FIG. 2 is a waveform diagram of the instantaneous voltage waveform Vg and the reference voltage waveform Vf when the utility power supply is abnormal. As shown in FIG. 2, the difference between the instantaneous voltage waveform Vg and the reference voltage waveform Vf near its zero-crossing is relatively small, which means that if the utility power supply abnormality occurs in this area, Then this exception will not be easily detected, so we can call this area "not easy to detect". On the other hand, the difference between the immediate voltage waveform Vg and the reference voltage waveform Vf is relatively large near its peak, which means that if the utility power supply abnormality occurs in this region, the abnormality will be relatively easy to be detected. It can be called "easy detection area". However, please note that the present invention is not limited to the fact that the instantaneous voltage waveform Vg and the reference voltage waveform Vf must have the same frequency and phase, and can also be applied when the frequencies or phases of the two are different.

In order to prevent the abnormal power supply occurring in the "non-detectable area" from being neglected, the present embodiment proposes the detecting apparatus 100 as shown in FIG. Taking Fig. 2 as an example, if the instantaneous voltage waveform Vg(t)=A ₁ sin(ω ₁ t ), A ₁ ==1.5, ω _{1 is} its amplitude and angular frequency, respectively, the reference voltage waveform Vf(t) =A ₂ sin(ω ₂ t ), A ₂ =1, ω ₂ are their amplitudes and angular frequencies, respectively, the first comparator 110 is used to compare the instantaneous voltage waveform Vg with the reference voltage waveform Vf, and generate A first difference waveform Vd1 (Vd1(t) = Vg(t) - Vf(t) = A ₁ sin(ω ₁ t ) - A ₂ sin(ω ₂ t )). Assuming that both have the same frequency (60 Hz) and phase, the first difference waveform Vd1(t)=(A ₁ -A ₂ )sin(ω t ). . In addition, the weighting function generator 120 is configured to generate a weighting function g(ωt); in this embodiment, the weighting function

Where t represents time, ω represents angular frequency, k represents a weighting constant, and k may be between 1 and 100; and FIG. 3 is an example of k=10. The multiplier 130 is configured to multiply the first difference waveform Vd1 by the weighting function g(ωt) to obtain A second difference waveform Vd2 (Vd2 = Vd1 × g(ωt)). FIG. 3 is a waveform diagram of the first difference waveform Vd1 and the second difference waveform Vd2 when the utility power supply is abnormal. As described in the previous paragraph of the present specification, the difference of the first difference waveform Vd1 in the "non-detectable area" is relatively small, so that the power supply abnormality is not easily detected. As shown in FIG. 3, after the first difference waveform Vd1 is corrected by the above "weighting", the second difference waveform Vd2 can be obtained, and the expected value of the difference in the "non-detectable area" can be quite close to The expected value of the difference in the "easy detection zone". In this way, the reliability and stability of the abnormality detection of the utility power supply can be ensured, even if the abnormality occurs in the "undetectable area", except for the zero crossing point.

FIG. 4 is a block diagram of a detection method 200 according to an embodiment of the present invention for detecting whether an abnormality occurs in a power supply of a utility. The detection method 200 is exemplified by voltage detection of power supply, and may include the following steps S210 to S260. Since the utility power supply has a normal voltage waveform under normal conditions, step S210 first sets or provides a reference voltage waveform to be identical to the normal voltage waveform. Step S220: measuring the instantaneous voltage waveform of the power supply, thereby comparing with the reference voltage waveform. Step S230: comparing the instantaneous voltage waveform (Vg) with the reference voltage waveform (Vf), and generating a first difference waveform (Vd1=Vg-Vf). Step S240: setting a weighting function g(ωt) and applying to the first difference waveform (Vd1), that is, an operation of multiplying the first difference waveform (Vd1) by the weighting function g(ωt) Thereby, a second difference waveform (Vd2) is obtained. In other words, the second difference waveform (Vd2) is the difference between the weighted instantaneous voltage waveform (Vg) and the reference voltage waveform (Vf). Step S250: Acquire an absolute value of the amplitude of the second difference waveform (Vd2) every predetermined time interval, and accumulate the absolute values of the amplitudes to obtain an accumulated difference value. Step S260: When the accumulated difference reaches a predetermined threshold, it is determined that the power supply of the utility is abnormal. In the event that the invention is applied to a parallel mains supply of a microgrid, then the system can initiate operation to disconnect the microgrid from the mains. In this embodiment, the weighting function Where t represents time, ω represents angular frequency, k represents a weighting constant, and k can be between 1 and 100.

FIG. 5 is a block diagram of a detection method 300 according to an embodiment of the present invention for detecting whether an abnormality occurs in a power supply of a utility. The detection method 300 is exemplified by current detection of power supply, and may include the following steps S310 to S360. Since the utility power supply has a normal current waveform under normal conditions, step S310 first sets or provides a reference current waveform whose amplitude, frequency, and phase are the same as the amplitude, frequency, and phase of the normal current waveform, respectively. Step S320: measuring the instantaneous current waveform of the power supply, thereby comparing with the reference current waveform. Step S230: comparing the instantaneous current waveform (Ig) with the reference current waveform (If), and generating a first difference waveform (Id1=Ig-If). Step S340: setting a weighting function g(ωt) and applying to the first difference waveform (Id1), that is, the operation of multiplying the first difference waveform (Id1) by the weighting function g(ωt) Thereby, a second difference waveform (Id2) is obtained. In other words, the second difference waveform (Id2) is the difference between the weighted instantaneous current waveform (Ig) and the reference current waveform (If). Step S350: Acquire an absolute value of the amplitude of the second difference waveform (Id2) every predetermined time interval, and accumulate the absolute values of the amplitudes to obtain an accumulated difference value. Step S360: When the accumulated difference reaches a predetermined threshold, it is determined that the power supply of the utility is abnormal. In the event that the invention is applied to a parallel mains supply of a microgrid, then the system can initiate operation to disconnect the microgrid from the mains. In this embodiment, the weighting function Where t represents time, ω represents angular frequency, k represents a weighting constant, and k can be between 1 and 100.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto. It is to be understood that the scope of the present invention is not limited by the spirit and scope of the present invention, and should be considered as a further embodiment of the present invention.

100‧‧‧Detection device

110‧‧‧First comparator

120‧‧‧weighted function generator

130‧‧‧Multiplier

140‧‧‧ accumulator

150‧‧‧Second comparator

Claims (7)

A device for detecting whether a power supply of a utility power supply is abnormal, the power supply having a normal voltage waveform under normal conditions, the device comprising: a first comparator for comparing a reference voltage waveform with a power supply Instantly generating a voltage waveform, and generating a difference between the reference voltage waveform and the instantaneous voltage waveform as a first difference waveform, wherein the amplitude, frequency, and phase of the reference voltage waveform are the same as the amplitude and frequency of the normal voltage waveform, respectively And phase; a weighting function generator that produces a weighting function Where t represents time, ω represents angular frequency, k represents a weighting constant; a multiplier multiplies the first difference waveform by a weighting function to obtain a second difference waveform; an accumulator, every other Obtaining an absolute value of the amplitude of the second difference waveform at a predetermined time interval, and accumulating the absolute values of the amplitudes to obtain an accumulated difference value; and a second comparator comparing the accumulated difference value with a predetermined threshold value If the accumulated difference exceeds the predetermined threshold, it is determined that the power supply of the utility is abnormal. The device of claim 1, wherein the weighting constant k is between 1 and 100. A method for detecting whether a power supply of a utility power supply is abnormal, the power supply having a normal voltage waveform under normal conditions, the method comprising the steps of: providing a reference voltage waveform; measuring an instantaneous voltage waveform of the power supply; Comparing the instantaneous voltage waveform with the reference voltage waveform, and generating a difference between the reference voltage waveform and the instantaneous voltage waveform as a first difference waveform; multiplying the first difference waveform by a weighting function And obtaining a second difference waveform, wherein t represents time, ω represents an angular frequency, and k represents a weighting constant; an absolute value of the amplitude of the second difference waveform is obtained every predetermined time interval, and the amplitudes are absolute The values are accumulated to obtain an accumulated difference; and when the accumulated difference reaches a predetermined threshold, it is determined that the power supply of the utility is abnormal. The method of claim 3, wherein the amplitude, frequency, and phase of the reference voltage waveform are the same as the amplitude, frequency, and phase of the normal voltage waveform, respectively. The method of claim 3, wherein the weighting constant k is between 1 and 100. A method for detecting whether a power supply of a utility power supply is abnormal, the power supply having a normal current waveform under normal conditions, the method comprising the steps of: providing a reference current waveform having the same amplitude, frequency, and phase Amplitude, frequency and phase of the normal current waveform; measuring an instantaneous current waveform of the power supply; comparing the instantaneous current waveform with the reference current waveform, and generating a first difference waveform; multiplying the first difference waveform by one Weighting function And obtaining a second difference waveform, wherein t represents time, ω represents an angular frequency, and k represents a weighting constant; an absolute value of the amplitude of the second difference waveform is obtained every predetermined time interval, and the absolute value of the amplitude is obtained Accumulating, and obtaining an accumulated difference; and when the accumulated difference reaches a predetermined threshold, it is determined that the power supply of the utility is abnormal. The method of claim 6, wherein the weighting constant k is between 1 and 100.