Bidirectional energy meter

Abstract

The present application relates to a bidirectional electric energy meter. An electric energy meter (180) for a multi-phase power grid includes a power transformer (104) having a primary side and a secondary side, a first analog front end (AFE) unit coupled to the secondary side of the power transformer, and a microcontroller (102) coupled to the primary side of the power transformer. The first AFE unit is coupled to a first phase of the multi-phase power grid. The microcontroller is configured to transmit a digitized request signal to the first AFE unit via the power transformer and receive a measurement signal from the first AFE unit via the power transformer. More specifically, the first AFE unit extracts information from the digitized request signal after receiving the digitized request signal.

Description

[0001] This application is a divisional application of Chinese patent application 201480084362.1, entitled “Bidirectional Electricity Meter”, filed on December 25, 2014. Technical Field

[0002] The present application relates to a bidirectional electric energy meter. Background Art

[0003] An energy meter is used to measure how much electrical energy a load has consumed from a source. Typically, an energy meter is coupled to an electrical grid connected between the load and the source. Summary of the invention

[0004] The present invention discloses a system and method for measuring electric energy using an electric energy meter of the present invention. In one embodiment, an electric energy meter for a multi-phase power grid includes a power transformer having a primary side and a secondary side, a first analog front end (AFE) unit coupled to the secondary side of the power transformer, and a microcontroller coupled to the primary side of the power transformer. The first AFE unit is coupled to a first phase of the multi-phase power grid. The microcontroller is configured to transmit a digitized request signal to the first AFE unit via the power transformer and receive a measurement signal from the first AFE unit via the power transformer. More specifically, the first AFE unit extracts information from the digitized request signal after receiving the digitized request signal.

[0005] In another embodiment, an apparatus for a multiphase power grid includes a power transformer having a primary side and a secondary side, a first plurality of analog front end (AFE) units coupled to the secondary side of the power transformer, a second plurality of AFE units coupled to the secondary side of the power transformer, and a microcontroller coupled to the primary side of the power transformer. More specifically, each of the first plurality of AFE units will be coupled to a separate phase of the multiphase power distribution and configured to measure the current of the particular phase. Each of the second AFE units will be coupled to a separate phase of the multiphase power grid and configured to measure the voltage of the particular phase. The microcontroller is configured to transmit a digitized request signal to each of the first AFE unit and the second AFE unit via the power transformer and receive measurement data from the first AFE unit and the second AFE unit via the power transformer. One of the first plurality of AFE units and one of the second plurality of AFE units will be coupled to each phase.

[0006] In yet another embodiment, the method includes transmitting, by a microcontroller coupled to the primary side of a power transformer, a digitized request signal to a plurality of analog front end (AFE) units, wherein each AFE unit is coupled between the secondary side of the power transformer and a phase of a multi-phase power grid, activating the plurality of AFE units after receiving the digitized request signal, measuring, by a first AFE unit, a current of a first phase of multi-phase power distribution, by a second AFE unit, a voltage of the first phase of multi-phase power distribution, and transmitting, by the first AFE unit and the second AFE unit, the measured current and the measured voltage of the first phase of multi-phase power distribution to the microcontroller. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] To describe in detail exemplary embodiments of the present invention, reference will now be made to the accompanying drawings, in which:

[0008] Figure 1 shows a block diagram illustrating an electric energy meter coupled to a multi-phase electrical grid according to various embodiments;

[0009] Figure 2 An example of an analog front end (AFE) unit is shown to further illustrate various embodiments;

[0010] Figure 3 An example illustrating an electric energy meter coupled to a single-phase power grid according to various embodiments is shown; and

[0011] Figure 4 A flow chart illustrating a method of measuring electrical energy using the disclosed electrical energy meter according to various embodiments is shown.

[0012] Symbols and terminology

[0013] Certain terms are used throughout the following description and claims to refer to specific system components. As one skilled in the art will recognize, companies may refer to components by different names. This document is not intended to distinguish between components that differ in name but not function. In the following discussion and claims, the terms "include" and "comprising" are used in an open manner and should therefore be interpreted to mean "including but not limited to...", and the terms "couple" or "coupled" mean either an indirect connection or a direct connection. Thus, if a first device is coupled to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections. DETAILED DESCRIPTION

[0014] The following discussion relates to various embodiments of the present invention. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be interpreted or otherwise used as limitations on the scope of the present disclosure, including the claims. In addition, it will be understood by those skilled in the art that the following description has a wide range of applications, and the discussion of any embodiment is intended only to be exemplary of the embodiment, and is not intended to imply that the scope of the present disclosure, including the claims, is limited to the embodiment.

[0015] The energy meter receives a current input signal and a voltage input signal from the power grid. In a typical multi-phase (e.g., three-phase) energy meter, the current input signal for the three phases comes from the three-phase power grid via a current transformer, and the voltage input signal comes from the three phases of the power grid via a resistor divider. The current input signal and the voltage input signal are sampled by the meter, and the current sample is multiplied by the voltage sample to obtain an electrical power sample. Accumulating these energy samples over time provides an indication of the electrical power (energy) consumed.

[0016] Further, some electric energy meters convert current input signals and voltage input signals into digital input samples for further processing by a microcontroller. Typically, a separate input channel in the meter is used for each of the three current and voltage input signals, and each input channel includes its own analog front end (AFE) unit, a current transformer and / or a voltage divider. This method is generally referred to as a synchronous method because all input signals are processed in parallel and synchronously. Using this method, each AFE unit of each input channel (in the case where the AFE receives a current input) is coupled to the power grid via a dedicated current transformer to avoid mismatching problems. The AFE unit is typically integrated with a microcontroller, meaning that the microcontroller can have a dedicated input for each AFE unit. Dedicated AFE units and current transformers can lead to increased complexity in designing a microcontroller, and can then have a large die size. Since the die size may be expensive, this method may disadvantageously increase production costs.

[0017] The disclosed embodiments relate to an electric energy meter that eliminates the need to integrate an AFE unit with a microcontroller. The microcontroller of the disclosed meter communicates with the AFE unit via a communication medium, and thus each of the microcontroller and the AFE unit has a separate connection to the communication medium. Thus, the microcontroller does not have a separate connection to each of the various AFE units. In the examples disclosed herein, the communication medium is a single transformer. Implementing the disclosed meter to measure electric energy can advantageously provide a less complex design of the microcontroller, and thus reduce costs.

[0018] The disclosed energy meter may not be limited to use in a multi-phase grid. According to various embodiments, the meter may also be used in a single-phase grid.

[0019] Figure 1 A block diagram 100 illustrating a three-phase power meter 180 according to various embodiments is shown. The illustrative power meter 180 is connected to the three phases A, B, C of a three-phase power source 122, which supplies a three-phase load 120. As mentioned above, although Figure 1 The disclosed energy meter 180 is shown as a three-phase energy meter, but the disclosed energy meter 180 can be connected to a multi-phase power grid or a single-phase power grid. For clarity, the following discussion will be limited to implementing the energy meter 180 for a three-phase power grid. However, for an energy meter connected to a single-phase power grid, the operating principles will be discussed with respect to Figure 3 A block diagram is provided separately.

[0020] Still reference Figure 1 , the illustrative energy meter 180 further includes a microcontroller unit (MCU) 102, a transformer 104, and six AFE units 106, 108, 110, 112, 114, and 116. According to the illustrative embodiment, the transformer 104 includes a primary (P) side and a secondary (S) side. The MCU 102 is connected to the primary side, and the AFE units 106, 108, 110, 112, 114, and 116 are connected to the secondary side.

[0021] Since the electric energy meter 180 is configured to measure electric energy about three phases A, B, and C, in an embodiment, each phase includes a current signal and a voltage signal. For example, phase A includes a current signal I A , phase B includes the current signal I B , and phase C includes the current signal Ic. Further, the current signal and the voltage signal of each phase are respectively connected via a resistor element (e.g., 136, 138, and 140) and a voltage divider (e.g., V DA 、V DB and V DC ) is coupled to the AFE unit. More specifically, the current signal I corresponding to phase A A It is converted into a voltage signal V via the resistor element 136. IA , and the voltage signal is received by the AFE unit 106. The current signal I corresponding to phase B B It is converted into a voltage signal V via the resistor element 138. IB , and the voltage signal is received by the AFE unit 108. The current signal Ic corresponding to phase C is converted into a voltage signal V via the resistor element 140. IC , and the voltage signal is received by the AFE unit 110. Still more specifically, the voltage signal of each phase is converted via a voltage divider into a voltage (eg, V A 、V B and Vc). For example, the AFE unit 112 is configured to DAReceives V corresponding to phase A A The AFE unit 114 is configured to DB Receives V corresponding to phase B B The AFE unit 116 is configured to DC Vc corresponding to phase C is received.

[0022] continue Figure 1 According to various embodiments, the transformer 104 is a digital transformer configured to transmit digital signals between the primary side and the secondary side of the transformer. In addition, the transformer 104 is preferably implemented as a circuit integrated on a printed circuit board (PCB).

[0023] Figure 2 An example is shown to further illustrate the AFE unit 106 according to various embodiments. Figure 1 The other AFE units of the embodiment may share the same architecture and operating principle as the AFE unit 106. Figure 2 As shown, the AFE unit 106 further includes an analog-to-digital conversion (ADC) unit 202 , a recovery circuit 204 , and a transceiver 206 .

[0024] More specifically, the ADC unit 202 is coupled to the power grid and is configured to digitize an input voltage (V IA ). The transceiver 206 is coupled to the secondary side of the transformer 104 and is configured to receive a signal from the MCU 102 through the transformer 104 / transmit a signal to the MCU 102 through the transformer 104. The recovery circuit 204 coupled to the transceiver 206 is configured to recover the signal received by the transceiver 206. Further, the recovery circuit 204 extracts information such as clock information and data information from the recovered signal.

[0025] Typically, the clock information is used to synchronize each AFE unit. In some embodiments, the extracted data may include executed instructions. Such executed instructions, together with the clock information, may be used by the MCU 102 to specify which AFE unit will retrieve a current signal or voltage signal from the power grid and which AFE unit is operable to transmit the digitized current signal or voltage signal back to the MCU 102.

[0026] For example, based on the extracted clock information and data information (extracted by the recovery circuit 204), during the first minute, the AFE unit 106 is assigned by the MCU 102 to retrieve V IA And digitize the retrieved V IA During the next minute, the AFE unit 106 may be assigned by the MCU 102 to digitize V via the transformer 104 (by the transceiver 206). IAAccording to an illustrative embodiment, each of the AFE units 106, 108, 110, 112, 114, and 116 is operable to retrieve and digitize a current signal or a voltage signal or transmit the digitized signal to the MCU 102 via the transformer 104. The MCU 102 may sequentially communicate with each of the AFE units 106-116 through the transformer 104. Figure 4 Further details of the operation of the power meter 180 are discussed in the flowchart in FIG.

[0027] Figure 3 An alternative example is shown illustrating an electrical energy meter 300 to be coupled to a single-phase electrical grid. Figure 3 In the example, the energy meter 300 is connected to a single-phase grid in which a source 301 supplies power to a load 303 via a single-phase line 333 and a neutral line 335 .

[0028] The energy meter 300 is configured to estimate the single-phase energy consumption by measuring the current signal flowing through the line 333 and the line 335. The current signal flowing through the line 333 is I sp ; The current signal flowing through the neutral line is I neutral More specifically, the electric energy meter 300 receives the measured voltage signal V sp And the voltage signal V neutral , voltage signal V sp And the voltage signal V neutral The resistor elements 313 and 315 are respectively used to obtain the current signal I sp and the current signal I neutral Convert.

[0029] Still refer to Figure 3 , electric energy meter 300 and Figure 1 The architecture of the electric energy meter 180 is similar to that of the electric energy meter 180. Figure 3 As shown, power meter 300 includes MCU 102, transformer 104, and AFE units 302 and 304. In some demonstrative embodiments, AFE units 302 and 304 are connected to the secondary side of transformer 104, and MCU 102 is connected to the primary side of transformer 104.

[0030] The AFE unit 302 is configured to receive the converted voltage signal V sp (It represents the current I sp ) and further digitize the received voltage signal V sp The AFE unit 304 is configured to receive the converted voltage signal V neutral (Representative I neutral ) and further digitize the received voltage signal V neutralFor the purpose of clarity, only the circuit configured to receive the converted current signal (ie, I sp and I neutral ) of the AFE unit (ie, 302 and 304). That is, other AFE units may be included in the meter 300, but may not be used.

[0031] According to various embodiments, the operation of the power meter 300 is similar to the one of the power meter 180. The MCU 102 starts transmitting the digitized request signal via the transformer 104 to the AFE unit.

[0032] Figure 4 A flow chart of a method 400 for measuring electrical energy using the disclosed electrical energy meter according to various embodiments is shown. The operations may be performed in the order shown or in a different order. Further, two or more of the operations may be performed in parallel instead of being performed sequentially.

[0033] The method 400 begins in block 402 by transmitting a digitized request signal to one of the AFE units by the MCU 102. According to the illustrative embodiment, the digitized request signal transmitted via the transformer 104 includes power, as well as data and clock information. As mentioned above, the information may include various instructions for the AFE unit to execute, and the clock information is operable to synchronize the AFE unit with the MCU 102.

[0034] After the AFE unit receives the request signal, the method continues to activate the AFE unit in block 404. More specifically, once the AFE unit receives the request signal, the AFE unit is activated by the power of the request signal. The activated AFE unit is configured to recover the request signal in order to extract the information of the data and the clock. Preferably, the recovery and extraction are performed by the recovery circuit (e.g., 204) of the AFE unit.

[0035] Still refer to Figure 4 , after the AFE unit extracts the data and clock information, the AFE unit is synchronized with the MCU 102 based on the extracted clock information. Further, the AFE unit is configured to execute the extracted data information (instructions). The execution of the instructions directs the method 400 to box 406, where the current signal of the first phase is measured. Subsequently, the MCU 102 may transmit another digitized request signal to another AFE unit to activate the AFE unit. Then, the method 400 continues to measure the voltage signal of the first phase at box 408. More specifically, the measurement of the voltage signal and the current signal is performed by the AFE unit to receive the converted voltage signal (e.g., V IA 、V IB 、V IC 、V A 、V B and VC ).

[0036] For example, MCU 102 transmits the first digitized request signal to AFE unit 106 via transformer 104. AFE unit 106 receives and decodes the first digitized request signal and extracts instructions from the first digitized request signal. Then AFE unit 106 starts to receive V IA After the MCU 102 transmits the first digitized request signal, the MCU 102 may transmit the second digitized request signal to the AFE unit 112. Similarly, the AFE unit 112 is configured to start receiving V A .

[0037] The AFE unit receives the converted voltage signal (eg, V IA and V A ), the method 400 continues to digitize the voltage signal at block 410. In some embodiments, the ADC unit of each AFE unit is configured to digitize the received voltage signal. For example, the ADC unit 202 of the AFE unit 106 digitizes the received voltage signal V IA .

[0038] The method 400 continues in block 412 with the AFE unit transmitting the handshake signal to the MCU 102, and the AFE unit receiving the confirmation signal. More specifically, the handshake signal is transmitted from the AFE unit to the MCU 102 via the transformer 104. In an example, the handshake signal may enable the MCU 102 to determine whether the AFE unit transmitting the handshake signal has matching clock information. If the MCU 102 approves the handshake signal, the MCU 102 may transmit the confirmation signal to the AFE unit.

[0039] Still refer to Figure 4 After the AFE unit receives the confirmation signal, the method 400 continues at block 414 to transmit the digitized voltage signal to the MCU 102 via the transformer 104. In some embodiments, the transceiver of each AFE unit is configured to transmit the digitized voltage signal. For example, the transceiver 206 of the AFE unit 106 transmits the digitized voltage signal to the MCU 102 via the transformer 104.

[0040] After the MCU 102 receives the digitized voltage signal, the MCU 102 is configured to process the digitized voltage signal and estimate the amount of electrical energy of the first phase that has been consumed by the load 120 .

[0041] The above discussion is meant to be an illustration of the principles and various embodiments of the present invention. Once the above disclosure is fully understood, many changes and modifications will become apparent to those skilled in the art. The appended claims are intended to be interpreted as including all such changes and modifications.

Claims

1. A method for a multiphase power grid, comprising: transmitting, by a microcontroller coupled to a primary side of a power transformer, a digitized request signal, the digitized request signal comprising a first communication to a first analog front end unit, i.e., a first AFE unit, to obtain a measurement of a first phase current of a multi-phase power grid and a second communication to a second AFE unit to obtain a measurement of a first phase voltage of the multi-phase power grid, wherein the first AFE unit and the second AFE unit are adapted to be coupled between a secondary side of the power transformer and a first phase of the multi-phase power grid; receiving, by the microcontroller, the measured value of the first phase current of the multi-phase grid from the first AFE unit via the power transformer; as well as The measured value of the first phase voltage of the multi-phase power grid is received from the second AFE unit via the power transformer by the microcontroller, wherein the transmission of the first communication and the second communication occurs before receiving the measured value of the first phase current from the first AFE unit and before receiving the measured value of the first phase voltage from the second AFE unit. 2 . The method of claim 1 , wherein the measured value of the first phase current is digitized. The method of claim 1 , wherein the measured value of the first phase voltage is digitized. The method of claim 1 , wherein the digitized request signal includes clock information.

5. A device for a multiphase power grid, comprising: a power transformer having a primary side and a secondary side; a first analog front end unit, i.e., a first AFE unit, coupled to the secondary side of the power transformer and adapted to be coupled to a first phase of a multiphase power grid, the first AFE unit being configured to measure a current of the first phase; a second AFE unit coupled to the secondary side of the power transformer and adapted to be coupled to the first phase of the multi-phase grid, the second AFE unit being configured to measure a voltage of the first phase; as well as a microcontroller coupled to the primary side of the power transformer and configured to: transmitting a digitization request signal to the first AFE unit and the second AFE unit, the digitization request signal comprising a first communication to the first AFE unit to obtain a measurement value of a first phase current and a second communication to the second AFE unit to obtain a measurement value of a first phase voltage; receiving the measured value of the first phase current of the multi-phase grid from the first AFE unit via the power transformer; as well as The measured value of the first phase voltage of the multi-phase grid is received from the second AFE unit via the power transformer, wherein the microcontroller is configured to transmit the first communication and the second communication before receiving the measured value of the first phase current or the measured value of the first phase voltage. The apparatus of claim 5 , wherein the measured value of the first phase current is digitized.

7. The apparatus of claim 5, wherein the measured value of the first phase voltage is digitized.

8. The apparatus of claim 5, wherein the digitized request signal includes clock information.

9. The apparatus of claim 5, wherein the power transformer is included on a printed circuit board.

10. A non-transitory computer readable medium comprising instructions which, when executed by a microcontroller, cause the microcontroller to: transmitting, by the microcontroller coupled to the primary side of the power transformer, a digitized request signal, the digitized request signal comprising a first communication to a first analog front end unit (AFE) unit to obtain a measurement of a first phase current of a multi-phase power grid and a second communication to a second AFE unit to obtain a measurement of a first phase voltage of the multi-phase power grid, wherein the first AFE unit and the second AFE unit are coupled between the secondary side of the power transformer and the first phase of the multi-phase power grid; receiving the measured value of the first phase current of the multi-phase grid from the first AFE unit via the power transformer; as well as The measured value of the first phase voltage of the multi-phase grid is received from the second AFE unit via the power transformer, wherein the instructions cause the microcontroller to transmit the first communication and the second communication before receiving the measured value of the first phase current and receiving the measured value of the first phase voltage. 11 . The non-transitory computer readable medium of claim 10 , wherein the measured value of the first phase current is digitized. 12 . The non-transitory computer readable medium of claim 10 , wherein the measured value of the first phase voltage is digitized.

13. The non-transitory computer-readable medium of claim 10, wherein the digitized request signal includes clock information.

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