CN110554242A - Impedance measuring device for grid-connected inverter - Google Patents
Impedance measuring device for grid-connected inverter Download PDFInfo
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- CN110554242A CN110554242A CN201910971823.1A CN201910971823A CN110554242A CN 110554242 A CN110554242 A CN 110554242A CN 201910971823 A CN201910971823 A CN 201910971823A CN 110554242 A CN110554242 A CN 110554242A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
Abstract
The invention provides a grid-connected inverter impedance measuring device, comprising: the harmonic voltage signal generating circuit is used for generating a reference harmonic voltage signal with preset communication frequency; the voltage transformation isolator transforms the voltage of the reference harmonic voltage signal to obtain an injection harmonic voltage signal which is electrically isolated from the reference harmonic voltage signal and is applied to two line ends of the inverter; the state switch is used for conducting the injection harmonic voltage signal in the measuring state; the voltage sampling conditioning circuit is used for acquiring the voltages of two line ends of the inverter to obtain voltage information containing harmonic voltage content information and corresponding harmonic voltage phase information; the current sampling conditioning circuit is used for acquiring current flowing through two line ends of the inverter to obtain current information containing harmonic current content information and corresponding harmonic current phase information; and the microprocessor is used for processing the voltage information and the current information to obtain the equivalent impedance of the inverter and the corresponding pure impedance and capacitive reactance.
Description
Technical Field
the invention belongs to the technical field of inverter performance detection, and particularly relates to a grid-connected inverter impedance measuring device.
Background
the inverter is used as important equipment of new energy and widely applied to the fields of wind power, solar energy and the like; power Line Communication (PLC) has the advantages of simple and fast networking, wide frequency range, no need of rewiring, low cost, and the like, and is widely used in inverter Communication systems.
As is known, the PLC communication requires impedance matching at the terminals, otherwise the decoupling data is prone to be abnormal and unstable, and the impedance of the inverter during operation is changed by injecting harmonic voltage signals of different frequencies. Therefore, it is very important to effectively and accurately provide the impedance at the communication frequency required by the PLC when the inverter is connected to the grid.
Disclosure of Invention
The present invention has been made to solve the above problems, and an object of the present invention is to provide a grid-connected inverter impedance measuring device capable of accurately measuring an equivalent impedance of an inverter connected to a power line communication system, a pure impedance and a capacitance reactance corresponding thereto at a predetermined communication frequency of the power line communication system on line.
in order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a grid-connected inverter impedance measuring device, which is used for measuring the equivalent impedance of an inverter which is connected with a power line communication system in a preset communication frequency of the power line communication system, and corresponding pure impedance and capacitive reactance, and is characterized by comprising the following steps: the harmonic voltage signal generating circuit is used for generating a reference harmonic voltage signal with preset communication frequency; the voltage transformation isolator transforms the voltage of the reference harmonic voltage signal to obtain an injection harmonic voltage signal which is electrically isolated from the reference harmonic voltage signal and is applied to two line ends of the inverter; the state switch is connected in series between the voltage transformation isolator and the inverter and used for conducting the injected harmonic voltage signal in the measuring state; the voltage sampling conditioning circuit is used for acquiring the voltages of two line ends of the inverter to obtain voltage information containing harmonic voltage content information and corresponding harmonic voltage phase information; the current sampling conditioning circuit is used for acquiring current flowing through two line ends of the inverter to obtain current information containing harmonic current content information and corresponding harmonic current phase information; and the microprocessor is used for processing the harmonic voltage content information and the corresponding harmonic voltage phase information, and the harmonic current content information and the corresponding harmonic current phase information to obtain the equivalent impedance of the inverter and the corresponding pure impedance and capacitive reactance.
The grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: wherein, harmonic voltage signal generation circuit has: the first voltage supply module and the second voltage supply module are independent of each other and are respectively used for supplying a first reference voltage and a second reference voltage; the square wave signal generating module is used for generating a square wave voltage signal with a preset communication frequency according to the first reference voltage; the signal waveform conversion module is used for converting the square wave voltage signal into a sine wave voltage signal; and the band-pass filtering module raises the voltage of the sine wave voltage signal based on the second reference voltage and performs band-pass filtering on the sine wave voltage signal after the voltage is raised to obtain a reference harmonic voltage signal.
the grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: the square wave signal generating module comprises a standard clock oscillator and a first resistor, the input end of the standard clock oscillator receives a first reference voltage, the frequency setting end of the standard clock oscillator is connected with one end of the first resistor, the signal waveform converting module comprises a second resistor and a first capacitor, one end of the second resistor is connected with the output end of the standard clock oscillator, the other end of the second resistor is connected with one end of the first capacitor, the band-pass filtering module comprises a third resistor, a fourth resistor, a second capacitor, a third capacitor, a first operational amplifier and a fifth resistor, one end of the third resistor is connected between the second resistor and the first capacitor, and the other end of the third resistor is connected with one end of the fourth resistor, one end of the second capacitor and one end of the third capacitor respectively; the positive phase input end of the first operational amplifier receives a second reference voltage, the negative phase input end of the first operational amplifier is connected with the other end of the third capacitor and one end of the fifth resistor respectively, the output end of the first operational amplifier is connected with the other ends of the second capacitor and the fifth resistor respectively, and the other end of the fourth resistor, the other end of the first capacitor and the other end of the first resistor are grounded together.
The grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: the band-pass filtering module further comprises a voltage division unit, the voltage division unit comprises a sixth resistor, a seventh resistor and a fourth capacitor, one end of the sixth resistor, one end of the seventh resistor and one end of the fourth capacitor are respectively connected with the positive phase input end of the first operational amplifier, the other end of the sixth resistor receives a second reference voltage, and the other end of the seventh resistor and the other end of the fourth capacitor are grounded together.
The grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: and the resistance values of the sixth resistor and the seventh resistor are equal.
the grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: the first voltage supply module and the second voltage supply module respectively comprise a reference voltage source.
the grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: the positive phase input end of the voltage transformation isolator is connected with the output end of the first operational amplifier, the negative phase input end of the voltage transformation isolator is grounded, and the positive phase output end and the negative phase output end of the voltage transformation isolator are respectively and correspondingly connected with the two line ends of the inverter.
The grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: wherein the second reference voltage is greater than the first reference voltage.
the grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: the sampling conditioning circuit comprises an eighth resistor, a ninth resistor, a second operational amplifier, a tenth resistor, an eleventh resistor, a twelfth resistor and a fifth capacitor, wherein one end of the eighth resistor is connected with the L-line end of the inverter, the other end of the eighth resistor and one end of the tenth resistor are connected with the positive-phase input end of the second operational amplifier, the other end of the tenth resistor is grounded, one end of the ninth resistor is connected with the N-line end of the inverter, the other end of the ninth resistor and one end of the eleventh resistor are connected with the negative-phase input end of the second operational amplifier, the other end of the eleventh resistor and one end of the twelfth resistor are connected with the output end of the second operational amplifier, the other end of the twelfth resistor and one end of the fifth capacitor are connected with the microprocessor, and the other end of the fifth capacitor is grounded.
The grid-connected inverter impedance measuring device provided by the invention can also have the following characteristics: wherein, the current sampling conditioning module comprises a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a third operational amplifier, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor and a sixth capacitor, one end of the thirteenth resistor and one end of the fourteenth resistor are connected with the L-line end of the inverter, the other end of the fourteenth resistor and one end of the sixteenth resistor are connected with the positive-phase input end of the third operational amplifier, the other end of the sixteenth resistor is grounded, the other end of the thirteenth resistor and one end of the fifteenth resistor are connected with the N-line end of the inverter, the other end of the fifteenth resistor and one end of the seventeenth resistor are connected with the negative-phase input end of the third operational amplifier, the other end of the seventeenth resistor and one end of the eighteenth resistor are connected with the output end of the third operational amplifier, the other end of the eighteenth resistor and one end of the sixth capacitor are connected, the other end of the sixth capacitor is grounded.
Action and Effect of the invention
According to the grid-connected inverter impedance measuring device of the invention, because of the harmonic voltage signal generating circuit, the transforming isolator, the voltage sampling conditioning circuit, the current sampling conditioning circuit and the microprocessor, the harmonic voltage signal generating circuit can generate the reference harmonic voltage signal with the preset communication frequency, the transforming isolator transforms the reference harmonic voltage signal to obtain the injected harmonic voltage signal which is electrically isolated with the reference harmonic voltage signal and is applied to the two line ends of the inverter, the voltage sampling conditioning circuit can collect the voltage of the two line ends of the inverter to obtain the voltage information containing the harmonic voltage content information and the corresponding harmonic voltage phase information, the current sampling conditioning circuit can collect the current flowing through the two line ends of the inverter to obtain the battery current information containing the harmonic current content information and the corresponding harmonic current phase information, the microprocessor can process the harmonic voltage content information and the corresponding harmonic voltage phase information, the harmonic current content information and the corresponding harmonic current phase information to obtain the equivalent impedance of the inverter and the corresponding pure impedance and capacitive reactance, so that the method can measure the equivalent impedance of the inverter connected with the power line communication system and the corresponding pure impedance and capacitive reactance. In addition, because the transformation isolator enables the injected harmonic voltage signal to be electrically isolated from the reference harmonic voltage signal, even if the inverter is in a grid-connected state with a power line communication system, the reference sine wave voltage signal is not affected, and therefore the accuracy and the reliability of the measurement result are ensured.
Drawings
fig. 1 is a block diagram of a configuration of a grid-connected inverter impedance measuring apparatus according to an embodiment of the present invention;
Fig. 2 is a circuit diagram of a grid-connected inverter impedance measuring device in the embodiment of the invention;
fig. 3 is a waveform diagram of a square wave voltage signal and a reference harmonic voltage signal in an embodiment of the invention.
FIG. 4 is a circuit diagram of a voltage sampling conditioning circuit in an embodiment of the invention; and
fig. 5 is a circuit diagram of a current sampling conditioning circuit in an embodiment of the invention.
Detailed Description
In order to make the technical means, the creation features, the achievement purposes and the effects of the invention easy to understand, the following embodiments specifically describe the impedance measuring device of the grid-connected inverter provided by the invention with reference to the accompanying drawings.
< example >
Fig. 1 is a block diagram showing a configuration of a grid-connected inverter impedance measuring device according to an embodiment of the present invention.
As shown in fig. 1, in the present embodiment, the grid-connected inverter impedance measuring apparatus 100 is configured to measure impedance information of an inverter 200, which is connected to a power line communication system (not shown in the figure) in a grid, at a preset communication frequency of the power line communication system, where the impedance information includes an equivalent impedance of the inverter and a corresponding pure impedance and a capacitive reactance. The inverter impedance measuring device 100 includes a harmonic voltage signal generating circuit 10, a transforming isolator 20, a state switch 30, a voltage sampling conditioning circuit 40, a current sampling conditioning circuit 50 and a microprocessor 60.
The harmonic voltage signal generating circuit 10 is used for generating a harmonic sine wave voltage signal AC of a preset communication frequencyrefThe device comprises a first voltage supply module 11, a second voltage supply module 12, a square wave signal generation module 13, a signal waveform conversion module 14 and a band-pass filter module 15.
The first voltage supply module 11 is used for supplying a first reference voltage Vref1。
the second voltage supply module 12 is independent from the first voltage supply module 11, and is used for supplying a second reference voltage Vref2。
The square wave signal generating module 13 is configured to generate a square wave voltage signal with a preset communication frequency according to the first reference voltage.
The signal waveform conversion module 14 is configured to convert the square wave voltage signal into a sine wave voltage signal.
The band-pass filtering module 15 is based on the second reference voltage Vref2raising the voltage of the sine wave voltage signal, and performing band-pass filtering on the sine wave voltage signal after raising the voltage to obtain a reference harmonic voltage signal ACref。
The voltage transformation isolator 20 converts the reference harmonic voltage signal ACrefTransforming to obtain a voltage signal AC with the reference harmonicrefPhase-electrically isolated injection harmonic voltage signal AC for application to L-line terminal and N-line terminal of inverter 200out。
A state-switching switch 20 connected in series between the transformer isolator 20 and the inverter 200 for switching on the injection harmonic voltage signal AC in the measuring stateoutOr cutting off the injected harmonic voltage signal AC in the non-measuring stateout。
The voltage sampling and conditioning circuit 40 is configured to acquire voltages at two terminals of the inverter 200 to obtain voltage information including harmonic voltage content information and corresponding harmonic voltage phase information.
The current sampling and conditioning circuit 50 is configured to acquire currents flowing through two terminals of the inverter 200 to obtain battery current information including harmonic current content information and corresponding harmonic current phase information.
The microprocessor 60 is used for controlling the on/off of the state switching switch 20; and is further configured to process the harmonic voltage content information and the corresponding harmonic voltage phase information of all inverters, and the harmonic current content information and the corresponding harmonic current phase information to obtain the equivalent impedance of the inverter 200 at the predetermined communication frequency, and the corresponding pure impedance and capacitive reactance.
Fig. 2 is a circuit diagram of the grid-connected inverter impedance measuring apparatus in the embodiment of the present invention.
As shown in fig. 2, the first voltage supply module 11 includes a reference voltage source U1, a capacitor C1, and a capacitor C2. The input end of the reference voltage source U1 is used for receiving an external high potential voltage and is grounded through a capacitor C1; the output terminal of the reference voltage source U1 is connected to ground through a capacitor C2. In the present embodiment, the reference voltage source U1 is a LM4040a25 type reference voltage source.
The second voltage supply module 12 includes a reference voltage source U2, a capacitor C3, and a capacitor C4. The input end of the reference voltage source U2 is used for receiving an external high potential voltage and is grounded through a capacitor C3; the output terminal of the reference voltage source U2 is connected to ground through a capacitor C4. In the present embodiment, the reference voltage source U2 is a LM4040a30 type reference voltage source.
in the present embodiment, the external high voltage received by the reference voltage source U1 and the reference voltage source U2 are both 5V, and the reference voltage source U1 outputs the first reference voltage Vref12.5V, and a second reference voltage V output by the reference voltage source U2ref2is 3V, Vref2-Vref10.5V. Designing a second reference voltage Vref2greater than a first reference voltage Vref1To ensure a reference harmonic voltage signal ACrefis above the reference 0V.
the square wave signal generating module 13 includes a standard clockOscillator U3 and resistor R1. In this embodiment, the standard clock oscillator U3 is a model LTC6906 standard clock oscillator. The input terminal of the standard clock oscillator U3 is connected to the output terminal of the reference voltage source U1, thereby receiving a first reference voltage Vref 1; the frequency setting terminal of the standard clock oscillator U3 is connected to one terminal of the resistor R1, the other terminal of the resistor R1 is grounded, and the output frequency of the square wave voltage signal can be adjusted by adjusting the resistance of the resistor R1, for example, when the standard clock oscillator U3 receives the first reference voltage Vref1When the resistance of 2.5V, R1 is 1000k Ω, the output frequency f of the square wave voltage signal is 100kHz × (100k Ω/1000k Ω) 10 kHz.
The signal waveform conversion module 14 includes a resistor R2 and a capacitor C5. One end of the resistor R2 is connected with the output end of the standard clock oscillator U3, and the other end of the resistor R2 is connected with one end of the capacitor C5; the other end of the capacitor C5 and the other end of the resistor R1 are commonly grounded. The resistor R2 and the capacitor C5 form an RC filter circuit to convert the square wave voltage signal into a sine wave voltage signal, the RC filter frequency cut-off frequency is set to be 0.3f to 1/2 pi to RC to 0.5f, so that the resistance value of the resistor R2 is 7500 omega, the capacity of the capacitor C5 is 680pF, and 1/2 pi to RC is 3.22 kHz.
The band-pass filtering module 15 includes a resistor R3, a resistor R4, a capacitor C6, a capacitor C7, an operational amplifier U4, a resistor R5, and a voltage dividing unit 15 a. In the present embodiment, the operational amplifier U4 is an OPA2330aid type operational amplifier.
One end of the resistor R3 is connected between the resistor R2 and the capacitor C5, so as to receive a sine wave voltage signal; the other end of the resistor R3 is connected with one end of a resistor R4, one end of a capacitor C6 and one end of a capacitor C7 respectively; the other end of the resistor R4, the other end of the capacitor C5 and the other end of the resistor R1 are grounded together; the negative phase input end of the operational amplifier U4 is connected to the other end of the capacitor C7 and one end of the resistor R5, respectively, and the output end of the operational amplifier U4 is connected to the other end of the capacitor C6 and the other end of the resistor R5, respectively.
the voltage dividing unit 15a includes a resistor R6, a resistor R7, and a capacitor C8. One end of the resistor R6, one end of the resistor R7 and one end of the capacitor C8 are respectively connected with the non-inverting input end of the operational amplifier U4; the other end of the resistor R6 and the baseThe output terminal of the quasi-voltage source U2 is connected to receive the second reference voltage Vref2(ii) a The other end of the resistor R7 and the other end of the capacitor C8 are commonly grounded. The reference voltage V ═ V received by the non-inverting input terminal of the operational amplifier U4ref2xr 7/(R7+ R6), in this embodiment, the resistances of the resistor R6 and the resistor R7 are equal, and the reference voltage V is 1/2Vref2thereby causing the operational amplifier U4 to be in accordance with 1/2Vref2Performing band-pass filtering on the sine wave voltage signal after the voltage is raised as a reference voltage to obtain a reference harmonic voltage signal ACref。
fig. 3 is a waveform diagram of a square wave voltage signal and a reference harmonic voltage signal in an embodiment of the invention.
in the present embodiment, the bandpass center frequency of the bandpass filter module 15 is set to beThe resistances of the resistor R3, the resistor R4 and the resistor R5 are set to be 75k omega, 2.49k omega and 200k omega respectively, and the capacitance of the capacitor C6 is 680pF, so fd is 10.666 kHz. FIG. 3 shows a square wave voltage signal and a reference harmonic voltage signal AC in the present embodimentrefa waveform diagram of (a).
As shown in FIG. 2, the transformer isolator 20 includes a transformer T1, and a non-inverting input terminal of the transformer T1 is connected to an output terminal of an operational amplifier U4 to receive the reference harmonic voltage signal ACref(ii) a The negative phase input end of the transformer T1 is grounded; the positive phase output terminal and the negative phase output terminal of the transformer T1 are correspondingly connected to the L line terminal and the N line terminal of the inverter 200, respectively.
As shown in fig. 2, the state-switching switch 30, i.e., K1 shown in fig. 2, is connected in series between the non-inverting output terminal of the transformer T1 and the L terminal of the inverter 200. When the impedance information of the inverter 200 needs to be measured, the state-switching switch 30 is closed under the control of the microprocessor 60, so that the injection harmonic voltage signal AC output by the transformer isolator 20 is transmittedoutAnd into inverter 200.
Fig. 4 is a circuit diagram of a voltage sampling conditioning circuit in an embodiment of the invention.
As shown in fig. 2 and 4, the voltage sampling conditioning circuit 40 includes a resistor R8, a resistor R9, an operational amplifier U5, a capacitor C9, a resistor R10, a capacitor C10, a resistor R11, a resistor R12, and a capacitor C11.
One end of the resistor R8 is connected with the L-terminal of the corresponding inverter 200, the other end of the resistor R8, one end of the capacitor C9 and one end of the resistor R10 are connected with the non-inverting input end of the operational amplifier U5 in common, and the other end of the capacitor C9 and the other end of the resistor R10 are connected with the sampling ground AGND in common; one end of the resistor R9 is connected with the N-line end of the corresponding inverter 200, the other end of the resistor R9, one end of the capacitor C10 and one end of the resistor R11 are connected with the negative phase input end of the operational amplifier U5, and the other end of the capacitor C10, the other end of the resistor R11 and one end of the resistor R12 are connected with the output end of the operational amplifier U5; the other end of the resistor R12 and one end of the capacitor C11 are commonly connected to the microprocessor 60, and the other end of the capacitor C11 is connected to AGND.
Fig. 5 is a circuit diagram of a current sampling conditioning circuit in an embodiment of the invention.
As shown in fig. 2 and 5, the current sampling and conditioning circuit 50 includes a resistor R13, a resistor R14, a resistor R15, an operational amplifier U6, a capacitor C12, a resistor R16, a capacitor C13, a resistor R17, a resistor R18, and a capacitor C14. In the present embodiment, the operational amplifier U6 is an OPA2330aid type operational amplifier.
One end of the resistor R13 and one end of the resistor R14 are commonly connected with the L-terminal of the inverter 200, the other end of the resistor R14, one end of the capacitor C12 and one end of the resistor R15 are commonly connected with the non-inverting input end of the operational amplifier U6, and the other end of the capacitor C12 and the other end of the resistor R16 are commonly connected with the sampling ground AGND; the other end of the resistor R13 and one end of the resistor R15 are commonly connected with the N-wire end of the inverter 200, the other end of the resistor R15, one end of the capacitor C13 and one end of the resistor R17 are commonly connected with the negative-phase input end of the operational amplifier U6, and the other end of the capacitor C13, the other end of the resistor R17 and one end of the resistor R18 are commonly connected with the output end of the operational amplifier U6; the other end of the resistor R18 and one end of the capacitor C14 are commonly connected to the microprocessor, and the other end of the capacitor C14 is connected to AGND.
The microprocessor 60 includes a switch control unit, a storage unit, an analysis unit, a processing unit, a judgment unit, and an alarm unit. In this embodiment, the microprocessor 50 is a TMS320F28377DPTPT type microprocessor.
The switch control unit is used for controlling the on/off of the state changeover switch 30.
The storage unit is used for storing the voltage information acquired by the voltage sampling conditioning circuit 40; and is also used for storing the current information collected by the current sampling and conditioning circuit 50.
the analysis unit is used for analyzing the harmonic voltage content V of the inverter 200 under the injection harmonic voltage signal of the preset communication frequency from the voltage information stored in the storage unitfAnd harmonic voltage phase angle thetaf(ii) a And is also used for analyzing the harmonic current content I of the inverter 200 under the injection harmonic voltage signal of the preset communication frequency from the current information stored in the storage unitfharmonic current phase angle phif。
The processing unit calculates to obtain the equivalent impedance Z of the inverter 200 under the preset communication frequency according to the harmonic voltage content, the harmonic voltage phase angle, the harmonic current content and the harmonic current phase angle of the inverter 200f＝Vf/IfPure impedance ZRf＝Zf×cos(θf-Φf) And capacitive reactance Zcf＝Zf×sin(θf-Φf)。
The judging unit is used for judging whether the equivalent impedance is larger than a corresponding preset equivalent impedance range or not; and is also used for judging whether the pure impedance is larger than the corresponding preset pure impedance range; and the capacitive reactance judging module is also used for judging whether the capacitive reactance is larger than a corresponding preset capacitive reactance range or not.
The alarm unit is used for sending an alarm prompt when the judging unit judges that the equivalent impedance is larger than the corresponding preset equivalent impedance range, or judges that the pure impedance is larger than the corresponding preset pure impedance range, or judges that the capacitive reactance is larger than the corresponding preset capacitive reactance range.
The operation process of the grid-connected inverter impedance measuring apparatus 100 in the present embodiment is as follows:
The microprocessor 60 controls the state switch 30 to be closed, and the harmonic voltage signal generating circuit 10 generates the reference harmonic voltage signal AC of the predetermined communication frequencyreftransformed by a transformation isolator 20Post-compression forming of injected harmonic voltage signal ACoutApplied to the L line terminal and the N line terminal of the inverter 200, the voltage acquisition conditioning circuit 40 acquires the voltage information of the inverter 200 and transmits the voltage information to the microprocessor 60; meanwhile, the current collecting and conditioning circuit 50 collects current information flowing through both terminals of the inverter group 200 and transmits the current information to the microprocessor 60. The microprocessor 60 processes the received voltage information and current information to obtain the equivalent impedance of the inverter 200 and the corresponding pure impedance and capacitive reactance, thereby implementing online measurement of the impedance information of the inverter 200.
Effects and effects of the embodiments
According to the grid-connected inverter impedance measuring apparatus of the present embodiment, since the harmonic voltage signal generating circuit, the transforming isolator, the voltage sampling conditioning circuit, the current sampling conditioning circuit and the microprocessor are provided, the harmonic voltage signal generating circuit can generate the reference harmonic voltage signal of the preset communication frequency, the transforming isolator transforms the reference harmonic voltage signal to obtain the injection harmonic voltage signal electrically isolated from the reference harmonic voltage signal and applied to the two terminals of the inverter, the voltage sampling conditioning circuit can collect the voltages at the two terminals of the inverter to obtain the voltage information including the harmonic voltage content information and the corresponding harmonic voltage phase information, the current sampling conditioning circuit can collect the currents flowing through the two terminals of the inverter to obtain the battery current information including the harmonic current content information and the corresponding harmonic current phase information, the microprocessor can process the harmonic voltage content information and the corresponding harmonic voltage phase information, the harmonic current content information and the corresponding harmonic current phase information to obtain the equivalent impedance of the inverter and the corresponding pure impedance and capacitive reactance, so that the embodiment can measure the equivalent impedance of the inverter connected with the power line communication system and the corresponding pure impedance and capacitive reactance. In addition, because the transformation isolator enables the injected harmonic voltage signal to be electrically isolated from the reference harmonic voltage signal, even if the inverter is in a grid-connected state with a power line communication system, the reference sine wave voltage signal is not affected, and therefore the accuracy and the reliability of the measurement result are ensured.
In addition, because the first voltage supply module and the second voltage supply module both contain reference voltage sources, the performance of the square wave signal generation module and the performance of the band-pass filtering module are more stable, and the performance stability of the reference harmonic voltage signal is improved.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (10)
1. A grid-connected inverter impedance measuring device is used for measuring equivalent impedance, corresponding pure impedance and capacitive reactance of an inverter which is connected with a power line communication system in a grid mode under a preset communication frequency of the power line communication system, and is characterized by comprising the following components:
The harmonic voltage signal generating circuit is used for generating a reference harmonic voltage signal of the preset communication frequency;
The transformation isolator transforms the voltage of the reference harmonic voltage signal to obtain an injection harmonic voltage signal which is electrically isolated from the reference harmonic voltage signal and is applied to two line ends of the inverter;
The state switch is connected between the transformation isolator and the inverter in series and used for conducting the injected harmonic voltage signal in a measuring state;
The voltage sampling conditioning circuit is used for acquiring the voltages of two line ends of the inverter to obtain voltage information containing harmonic voltage content information and corresponding harmonic voltage phase information;
The current sampling conditioning circuit is used for acquiring the current flowing through two line ends of the inverter to obtain current information containing harmonic current content information and corresponding harmonic current phase information; and
And the microprocessor is used for processing the harmonic voltage content information and the corresponding harmonic voltage phase information as well as the harmonic current content information and the corresponding harmonic current phase information to obtain the equivalent impedance of the inverter, the corresponding pure impedance and the capacitive reactance.
2. The grid-connected inverter impedance measuring apparatus according to claim 1, characterized in that:
wherein the harmonic voltage signal generation circuit has:
The first voltage supply module and the second voltage supply module are independent of each other and are respectively used for supplying a first reference voltage and a second reference voltage;
the square wave signal generating module is used for generating a square wave voltage signal of the preset communication frequency according to the first reference voltage;
The signal waveform conversion module is used for converting the square wave voltage signal into a sine wave voltage signal;
And the band-pass filtering module raises the voltage of the sine wave voltage signal based on the second reference voltage, and performs band-pass filtering on the raised voltage sine wave voltage signal to obtain the reference harmonic voltage signal.
3. the grid-connected inverter impedance measuring apparatus according to claim 2, characterized in that:
wherein the square wave signal generating module comprises a standard clock oscillator and a first resistor, the input end of the standard clock oscillator receives the first reference voltage, the frequency setting end of the standard clock oscillator is connected with one end of the first resistor,
The signal waveform conversion module comprises a second resistor and a first capacitor, one end of the second resistor is connected with the output end of the standard clock oscillator, the other end of the second resistor is connected with one end of the first capacitor,
The band-pass filtering module comprises a third resistor, a fourth resistor, a second capacitor, a third capacitor, a first operational amplifier and a fifth resistor, wherein one end of the third resistor is connected between the second resistor and the first capacitor, and the other end of the third resistor is respectively connected with one end of the fourth resistor, one end of the second capacitor and one end of the third capacitor; a positive phase input end of the first operational amplifier receives the second reference voltage, a negative phase input end of the first operational amplifier is respectively connected with the other end of the third capacitor and one end of the fifth resistor, an output end of the first operational amplifier is respectively connected with the other end of the second capacitor and the other end of the fifth resistor,
The other end of the fourth resistor, the other end of the first capacitor and the other end of the first resistor are grounded together.
4. The grid-connected inverter impedance measuring apparatus according to claim 3, characterized in that:
Wherein, the band-pass filtering module also comprises a voltage dividing unit which comprises a sixth resistor, a seventh resistor and a fourth capacitor,
One end of the sixth resistor, one end of the seventh resistor and one end of the fourth capacitor are respectively connected with the non-inverting input end of the first operational amplifier,
The other end of the sixth resistor receives the second reference voltage,
the other end of the seventh resistor and the other end of the fourth capacitor are grounded together.
5. The grid-connected inverter impedance measuring apparatus according to claim 4, characterized in that:
And the resistance values of the sixth resistor and the seventh resistor are equal.
6. The grid-connected inverter impedance measuring apparatus according to claim 2, characterized in that:
The first voltage supply module and the second voltage supply module respectively comprise a reference voltage source.
7. The grid-connected inverter impedance measuring apparatus according to claim 2, characterized in that:
wherein the positive phase input end of the transformation isolator is connected with the output end of the first operational amplifier, the negative phase input end of the transformation isolator is grounded,
And the positive phase output end and the negative phase output end of the voltage transformation isolator are respectively and correspondingly connected with the two wire ends of the inverter.
8. The grid-connected inverter impedance measuring apparatus according to claim 1, characterized in that:
Wherein the second reference voltage is greater than the first reference voltage.
9. The grid-connected inverter impedance measuring apparatus according to claim 1, characterized in that:
Wherein the sampling conditioning circuit comprises an eighth resistor, a ninth resistor, a second operational amplifier, a tenth resistor, an eleventh resistor, a twelfth resistor and a fifth capacitor,
One end of the eighth resistor is connected with the L-line end of the inverter, the other end of the eighth resistor and one end of the tenth resistor are connected with the non-inverting input end of the second operational amplifier together, the other end of the tenth resistor is grounded,
one end of the ninth resistor is connected with the N line end of the inverter, the other end of the ninth resistor and one end of the eleventh resistor are connected with the negative phase input end of the second operational amplifier, the other end of the eleventh resistor and one end of the twelfth resistor are connected with the output end of the second operational amplifier,
The other end of the twelfth resistor and one end of the fifth capacitor are connected with the microprocessor together, and the other end of the fifth capacitor is grounded.
10. The grid-connected inverter impedance measuring apparatus according to claim 1, characterized in that:
Wherein the current sampling conditioning module comprises a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a third operational amplifier, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor and a sixth capacitor,
One end of the thirteenth resistor and one end of the fourteenth resistor are commonly connected to an L-line terminal of the inverter, the other end of the fourteenth resistor and one end of the sixteenth resistor are commonly connected to a positive-phase input terminal of the third operational amplifier, the other end of the sixteenth resistor is grounded,
The other end of the thirteenth resistor and one end of the fifteenth resistor are connected to the N-line end of the inverter, the other end of the fifteenth resistor and one end of the seventeenth resistor are connected to the negative-phase input end of the third operational amplifier, the other end of the seventeenth resistor and one end of the eighteenth resistor are connected to the output end of the third operational amplifier,
the other end of the eighteenth resistor and one end of the sixth capacitor are connected with the microprocessor together, and the other end of the sixth capacitor is grounded.
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