JP7009113B2 - AC signal generator - Google Patents

Description

The present invention relates to an AC signal generator capable of synchronous operation with a plurality of units.

In general, measuring instruments are periodically calibrated using instruments traceable to international standards in order to ensure reliability for the values indicated by the instruments. An AC signal generator is known as a device used for this work. As for AC signal generators, those that can construct a calibration system for wattmeters by connecting multiple AC signal generators and operating them synchronously have been put into practical use.

FIG. 3 is a block diagram showing the configuration of a conventional AC signal generator 500. The AC signal generator 500 is a device that outputs a single-phase AC voltage or AC current synchronized with a reference signal according to a setting such as a phase shift amount. As shown in this figure, the AC signal generator 500 includes an OSC_IN port and an OSC_OUT port. Both the OSC_IN port and the OSC_OUT port are provided with a signal I terminal and a signal Q terminal.

The AC signal generator 500 has a master function and a slave function. When operating as a master, a reference signal is generated and used for its own operation, and is output from the OSC_OUT port for supply to the slave.

When operating as a slave, a reference signal is input from the OSC_IN port and used for its own operation, and is output from the OSC_OUT port for supply to the next stage.

Here, the reference signal is composed of a signal I and a signal Q proportional to cos (ωt) and sin (ωt). The signal I and the signal Q are two-phase sinusoidal signals having an orthogonal phase relationship with a phase difference of π / 2. In the present specification, the amplitude of the reference signal is set to 1 for the sake of simplicity.

FIG. 4 shows an example of connection between an AC signal generator 500 operating as a master and an AC signal generator 500 operating as a slave. This figure is a connection example when the master 500a, the first slave 500b, and the second slave 500c are connected.

In the example of this figure, the signal I terminal and signal Q terminal of the OSC_OUT port of the master 500a are connected to the signal I terminal and signal Q terminal of the OSC_IN port of the first slave 500b, respectively, and the OSC_OUT port of the first slave 500b is connected. The signal I terminal and the signal Q terminal are connected to the signal I terminal and the signal Q terminal of the OSC_IN port of the second slave 500c, respectively. This connection is a so-called "daisy chain connection", and a larger number of slave machines can be connected.

In the master 500a, the frequency f0 of the reference signal, the designation of whether the master 500a is to be a voltage output or a current output, and the amplitude A0 of the output signal are set. In the first slave 500b, the phase shift amount θ1 with respect to the reference signal, the designation of whether the first slave 500b is to be a voltage output or a current output, and the amplitude A1 of the output signal are set. In the second slave 500c, a phase shift amount θ2 with respect to the reference signal, designation of whether the second slave 500c is to be a voltage output or a current output, and an amplitude A2 of the output signal are set.

Returning to the description of FIG. 3, the AC signal generator 500 includes SW1 and SW2 in which two systems of signal I and signal Q are interlocked and switched, and DAC1 to DAC3, SW3, SW4 and adder which are multiplication type DA converters. ADD1, control unit 510, two-phase sine wave generation unit 520, voltage amplification unit 530, current amplification unit 540, voltage detection unit 550, current detection unit 560, ADC1, ADC2, SW5, amplitude detection unit 570, amplitude control unit 580. I have.

When operating as a master, the control unit 510 accepts settings of the reference signal frequency, voltage output / current output, and amplitude of the output signal, and when operating as a slave, the phase shift amount and voltage output / with respect to the reference signal. Accepts current output and output signal amplitude settings.

SW1, SW2, and SW3 are switched between the ext side (external reference signal) and the int side (internal reference signal) by the control unit 510. The control unit 510 switches SW1, SW2, and SW3 to the int side when operating as a master, and switches SW1, SW2, and SW3 to the ext side when operating as a slave.

The ext side of SW1 is connected to the signal I terminal and the signal Q terminal of the OSC_IN port, respectively, and the int side is connected to the output side of DAC1 and DAC2, respectively. The common contact is connected to the signal I terminal and the signal Q terminal of the OSC_OUT port.

The ext side of SW2 is connected to the signal I terminal and the signal Q terminal of the OSC_IN port, respectively, and the int side is connected to the reference voltage source Vref. The common contact is connected to the input side of DAC1 and DAC2, respectively. The ext side of SW3 is connected to the output side of DAC2, and the int side is grounded. The common contact of SW3 is connected to the input side of ADD1.

The SW4 and SW5 are switched between the V side (voltage output) and the I side (current output) by the control unit 510. The control unit 510 switches SW4 and SW5 to the V side when outputting an AC voltage, and switches SW4 and SW5 to the I side when outputting an AC current.

The V side of the SW4 is connected to the voltage amplification unit 530, and the I side is connected to the current amplification unit 540. The common contact of SW4 is connected to the output side of DAC3. The V side of the SW 5 is connected to the output side of the voltage detection unit 550 via the ADC 1, and the I side is connected to the output side of the current detection unit 560 via the ADC 2 and is connected. The common contact of SW5 is connected to the input side of the amplitude detection unit 570.

First, the case of operating as a master will be described. When operating as a master, the two-phase sine wave generation unit 520 generates a reference signal according to the frequency set by the control unit 510. The two-phase sine wave generator 520 generates a reference signal by a technique known as DDS (Direct Digital Synthesizer).

Here, the DDS stores the instantaneous phase of the generated signal in a register called a "phase accumulator", and increases the value of the phase accumulator by a constant value (phase increment proportional to the generated frequency) for each sampling period. It is a technique to obtain the sequential phase and to obtain the instantaneous value of the generated signal from the phase by a method such as searching a function table.

The signal I: cos (ωt) and the signal Q: sin (ωt), which are the outputs of the two-phase sine wave generator 520, are input to the multiplication type DA converters DAC1 and DAC2, respectively.

When operating as a master, the reference voltage source Vref is input to the analog input terminals of DAC1 and DAC2 via SW2. Therefore, DAC1 and DAC2 operate as a normal DA converter and output a two-phase sine wave signal converted to analog.

Since this two-phase sine wave signal is guided to the OSC_OUT port via SW1, cos (ωt) is output from the signal I terminal of the OSC_OUT port, and sin (ωt) is output from the signal Q terminal.

The signal I: cos (ωt) output by the DAC1 is also input to the adder ADD1. Since 0 is input to the other input of the adder ADD1 via SW3, the adder ADD1 outputs the signal I: cos (ωt) to the DAC3 as it is.

The DAC 3 operates as a digitally controlled variable attenuator, and adjusts the input amplitude of the voltage amplification unit 530 or the current amplification unit 540 in the subsequent stage according to the control of the amplitude control unit 580. Hereinafter, it is assumed that the voltage output is set in the control unit 510, and the SW4 and SW5 are switched to the V side. The basic operation is the same when the current output is set.

The output of the voltage amplification unit 530 is isolated and transmitted by the output transformer, is transformed according to the turns ratio, and is output as an AC voltage signal from the voltage output terminal. In the AC voltage signal output from the voltage output terminal, the voltage between the terminals is detected by the voltage detection unit 550, and the AC voltage signal is converted into an instantaneous value of a digital value by ADC1.

The amplitude detection unit 570 obtains an amplitude value proportional to the output voltage value by rectifying and smoothing the instantaneous value of the voltage, and outputs the amplitude value to the amplitude control unit 580. The amplitude control unit 580 obtains the ratio of this amplitude value to the amplitude value for which the control unit 510 has received the setting, and adjusts the digital value to be input to the multiplication type DAC3 based on the ratio.

に基づき、入力された基準信号である信号Ｉ：ｃｏｓ（ωｔ）、信号Ｑ：ｓｉｎ（ωｔ）に、それぞれｃｏｓ（θ）、－ｓｉｎ（θ）を掛けて、それらを加算することにより、任意の位相シフト量θの信号ｃｏｓ（ωｔ＋θ）が得られることを利用する。 Next, a case of operating as a slave will be described. Phase shift in slaves is the addition theorem of trigonometric functions

By multiplying the input reference signals I: cos (ωt) and Q: sin (ωt) by cos (θ) and −sin (θ), respectively, and adding them, it is arbitrary. It is utilized that the signal cos (ωt + θ) of the phase shift amount θ of is obtained.

Therefore, when operating as a slave, the two-phase sine wave generator 520 stops the DDS operation and fixes the value of the phase accumulator to −θ. Here, −θ is the inversion of the sign of the phase shift amount θ that the control unit 510 has accepted the setting.

At this time, since cos (−θ) = cos (θ) and sin (−θ) = −sin (θ), the two-phase sine wave generator 520 outputs cos (θ) and −sin (θ). It is equivalent to what you are doing. Then, cos (θ) and −sin (θ) are input to the multiplication type DA converters DAC1 and DAC2, respectively.

When operating as a slave, the signal I: cos (ωt) and the signal Q: sin (ωt) input from the OSC_IN port are input to the analog input terminals of DAC1 and DAC2, respectively. The signals I and Q are reference signals generated by the master and are output from the OSC_OUT port via SW1.

The signal I: cos (ωt) is input to the analog input of the DAC1, and cos (θ) is input to the digital input. Therefore, the output of DAC1 is cos (ωt) · cos (θ).

The signal Q: sin (ωt) is input to the analog input of the DAC2, and −sin (θ) is input to the digital input. Therefore, the output of DAC2 is −sin (ωt) · sin (θ).

The cos (ωt) and cos (θ) output by the DAC1 and the −sin (ωt) and sin (θ) output by the DAC2 are input to the adder ADD1. Therefore, the output of the adder ADD1 is cos (ωt), cos (θ) -sin (ωt), sin (θ), that is, cos (ωt + θ) of the phase shift amount θ with respect to the reference signal. Subsequent operations are the same as for the master.

Japanese Unexamined Patent Publication No. 6-132730

"AC standard voltage / current generator 2558A pursuing calibration work efficiency" Yokogawa Giho Vol.57 No.1 (2014)

Since the AC signal generator is used for calibration of measuring equipment, high-precision output is required. In particular, when a plurality of units are used in synchronization, highly accurate phase control for a reference signal is required.

Therefore, an object of the present invention is to improve the phase control accuracy when a plurality of AC signal generators are used in synchronization.

In order to solve the above problems, the AC signal generator, which is one aspect of the present invention, accepts a frequency setting and generates a reference signal of the frequency and a reference signal generated by the reference signal generator. Alternatively, the AC signal output unit includes a phase synchronization unit that generates an operation reference signal that follows an externally input reference signal, and an AC signal output unit that outputs an AC signal that is synchronized with the operation reference signal. , The first phase rotation unit that accepts the setting of the phase shift amount and shifts the phase of the operation reference signal according to the phase shift amount, the output signal of the first phase rotation unit, and the output AC signal. It is provided with a phase difference detecting unit for detecting the phase difference between the above and the second phase rotating unit for correcting the phase of the output signal of the first phase rotating unit based on the phase difference detected by the phase difference detecting unit. It is characterized by that.
Here, the phase synchronization unit, the first phase rotation unit, and the second phase rotation unit can perform digital arithmetic processing on the complex sinusoidal wave signal.
The phase difference detection unit may include an orthogonal detection unit.
At this time, it is possible to provide an amplitude control unit that accepts the amplitude setting and controls the amplitude of the AC signal to be output based on the ratio of the amplitude calculated from the output signal of the orthogonal detection unit and the received amplitude.
Further, the AC signal output unit can include an AC voltage output unit that outputs an AC voltage signal and an AC current output unit that outputs an AC current signal.

According to the present invention, it is possible to improve the phase control accuracy when a plurality of AC signal generators are used in synchronization.

It is a block diagram explaining the structure of the AC signal generator of this embodiment. It is a figure explaining the connection example of a master and a slave. It is a block diagram explaining the structure of the conventional AC signal generator. It is a figure explaining the connection example of a master and a slave.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an AC signal generator 100 of the present embodiment. The AC signal generator 100 is a device that outputs an AC voltage signal and an AC current signal synchronized with a reference signal according to a setting such as a phase shift amount. This makes it possible to calibrate a single-phase wattmeter with one unit. Further, the calibration of the three-phase wattmeter can be performed with two or three units depending on the wiring method. However, either an AC voltage signal or an AC current signal may be output.

As shown in this figure, the AC signal generator 100 includes an OSC_IN port and an OSC_OUT port. Both the OSC_IN port and the OSC_OUT port are provided with a signal I terminal and a signal Q terminal.

The AC signal generator 100 has a master function and a slave function. When operating as a master, a reference signal is generated and used for its own operation, and is output from the OSC_OUT port for supply to the slave.

When operating as a slave, a reference signal is input from the OSC_IN port and used for its own operation, and is output from the OSC_OUT port for supply to the next stage.

Here, the reference signal is composed of a signal I and a signal Q proportional to cos (ωt) and sin (ωt). The signal I and the signal Q are two-phase sinusoidal signals having an orthogonal phase relationship with a phase difference of π / 2. In the present specification, the amplitude of the reference signal is set to 1 for the sake of simplicity. In this figure, the thick line shows a path for processing as a complex number with the signal I side as the real part and the signal Q side as the imaginary part.

FIG. 2 shows an example of connection between an AC signal generator 100 operating as a master and an AC signal generator 100 operating as a slave. In the example of this figure, the master 100a, the first slave 100b, and the second slave 100c are connected, and can be applied, for example, to output a three-phase four-wire calibration signal. In this case, the master 100a outputs the AC voltage and the AC current of the first phase, the first slave 100b outputs the AC voltage and the AC current of the second phase, and the third slave 100c outputs the AC voltage of the third phase. And alternating current are output.

Specifically, the signal I terminal and signal Q terminal of the OSC_OUT port of the master 100a are connected to the signal I terminal and signal Q terminal of the OSC_IN port of the first slave 100b, respectively, and the signal of the OSC_OUT port of the first slave 100b is connected. The I terminal and the signal Q terminal are connected to the signal I terminal and the signal Q terminal of the OSC_IN port of the second slave 100c, respectively. This connection is a so-called "daisy chain connection", and a larger number of slave machines can be connected.

In the master 100a, the frequency f0 of the reference signal, the current phase shift amount θi0 when the voltage phase is used as a reference, the voltage amplitude Av0, and the current amplitude Ai0 are set. However, instead of the current phase shift amount θi0, the voltage phase shift amount θv0 when the current phase is used as a reference may be set.

The first slave 100b is set with a voltage phase shift amount θv1 with respect to the reference signal, a current phase shift amount θi1 with respect to the reference signal, a voltage amplitude Av1 and a current amplitude Ai1, and the second slave 100c is set with a voltage phase shift amount with respect to the reference signal. θv2, the current phase shift amount θi2 with respect to the reference signal, the voltage amplitude Av2, and the current amplitude Ai2 are set. The slave setting value may be set by the master 100a according to a preset rule.

Returning to the description of FIG. 1, the AC signal generator 100 includes SW1, DAC1, DAC2, ADC1, ADC2, a control unit 110, and a two-phase sine wave generator 120 in which two systems of signal I and signal Q are switched in conjunction with each other. , PLL 130, AC voltage output unit 200, and AC current output 300.

The AC voltage output unit 200 outputs an AC voltage signal from the voltage output terminal, and the AC current output unit 300 outputs an AC current signal from the current output terminal.

When operating as a master, the control unit 110 accepts settings of a reference signal frequency, a current phase shift amount, a voltage amplitude, and a current amplitude, and when operating as a slave, the voltage phase shift amount and the current phase shift amount, Accepts voltage amplitude and current amplitude settings.

The control unit 110 that has received various settings sets the reference signal frequency in the two-phase sine wave generation unit 120, sets the voltage phase shift amount in the first phase rotation unit 201 described later, and sets the current phase shift amount in the first phase rotation unit 201 described later. It is set in the one-phase rotating unit 301, the voltage amplitude is set in the amplitude control unit 210 described later, and the current amplitude is set in the amplitude control unit 310 described later.

The SW1 is switched between the ext side (external reference signal) and the int side (internal reference signal) by the control unit 110. The control unit 110 switches SW1 to the int side when operating as a master, and switches SW1 to the ext side when operating as a slave.

In the signal I system of SW1, the ext side is connected to the signal I terminal of the OSC_IN port, and the int side is connected to the output side of the DAC1. The common contact of the signal I system of SW1 is connected to the signal I terminal of the OSC_OUT port and the input side of ADC1.

In the signal Q system of SW1, the ext side is connected to the signal Q terminal of the OSC_IN port, and the int side is connected to the output side of the DAC2. The common contact of the signal Q system of SW1 is connected to the signal Q terminal of the OSC_OUT port and the input side of ADC2.

When operating as a master, the two-phase sine wave generation unit 120 generates a reference signal according to the frequency set by the control unit 110. Here, the reference signal is a two-phase sine wave, that is, a complex sine wave, and is generated by using the DDS technique as in the conventional case. The two-phase sine wave generator 120 is not used when operating as a slave.

When operating as a master, the real part signal generated by the two-phase sine wave generation unit 120 is input to DAC1 and converted into an analog signal. Then, it is guided to the signal I terminal of the OSC_OUT port and the input side of the ADC1. Further, the imaginary part signal generated by the two-phase sine wave generation part 120 is input to the DAC2 and converted into an analog signal. Then, it is guided to the signal Q terminal of the OSC_OUT port and the input side of the ADC2.

When operating as a slave, the signal I input to the signal I terminal of the OSC_IN port is guided to the signal I terminal of the OSC_OUT port and the input side of the ADC1. Further, the signal Q input to the signal Q terminal of the OSC_IN port is guided to the signal Q terminal of the OSC_OUT port and the input side of the ADC2.

The PLL 130 includes a phase comparison unit 131, a loop filter 132, and a two-phase sine wave generation unit 133. The two-phase sine wave generator 133, like the two-phase sine wave generator 120, uses DDS technology to generate a complex sine wave. Specifically, it is provided with a generation frequency control input terminal and generates a complex sine wave having a frequency corresponding to the signal input to the generation frequency control input terminal.

The PLL 130, which is a phase-locked loop, compares the phase of the complex sine wave obtained by ADC1 and ADC2 with the phase of the output signal of the two-phase sine wave generator 133 by the phase comparison unit 131, and loops the output. It is input to the generation frequency control input terminal of the two-phase sine wave generation unit 133 via the filter 132 to control the generation frequency. The output of the PLL 130 serves as a reference signal for the AC signal generation operation.

When operating as a master, a reference signal generated by itself is input to the PLL 130, and when operating as a slave, a reference signal generated by the master is input. The operation after the reference signal is input to the PLL 130 is the same for both the master and the slave. Therefore, there is no difference in the delay time between the master and the slave, and the phase control accuracy can be improved. In the conventional AC signal generator 500 shown in FIG. 3, the slave has a phase delay corresponding to the delay time of one stage of the multiplication type DAC with respect to the master.

?ここで、ｔａｎ^－１（ｙ／ｘ）の値域は±π／２であるが、点（ｘ，ｙ）の存在する象限が、第２象限ならπ、第３象限なら－πを加算して補正することにより、容易に±πに拡張することができる。したがって、ｘ、ｙの正負により象限を判定し、象限に応じた補正を行なうことで、位相差（α－β）を正確に求めることができる。 Here, the operation of the phase comparison unit 131 in the PLL 130 will be described. Generally, when the angular frequency of the signal is ω, the phase difference (α-) of the complex sine wave ej ^{(ωt + α)} based on ej ^{(ωt + β)} is shown in [Equation 2] to [Equation 4]. β) is calculated as the argument (tan ^-1 (y / x)) of the product (x + jy) of the conjugate complex number (ej ^{(ωt + β)} ) ^* on the reference side and the input signal ej ^{(ωt + α)} . Can be done.

Here, the range of tan ^-1 (y / x) is ± π / 2, but if the quadrant where the point (x, y) exists is the second quadrant, π is added, and if it is the third quadrant, -π is added. It can be easily expanded to ± π by correcting it. Therefore, the phase difference (α-β) can be accurately obtained by determining the quadrant based on the positive and negative of x and y and performing correction according to the quadrant.

Further, by using an algorithm known as the CORDIC method, it is possible to obtain the phase difference (α-β) in the range of ± π by inputting two values (x, y) without performing division. ..

By the way, when the angular frequencies (ω ₁ , ω ₂ ) of the two signals to be phase-compared are different, the phase difference increases by (ω ₁ , ω ₂ ) t with time t. As a result, the range of ± π is exceeded, and the polarity is reversed with a large discontinuity (± 2π), so that normal PLL operation cannot be performed.

Therefore, in the phase comparison unit 131, for example, when the phase of the point (x, y) increases from the second quadrant and enters the third quadrant, 2π is added and the phase decreases from the third quadrant. When entering the second quadrant, the output value of the phase comparison unit 131 is linearized by subtracting 2π so that normal PLL operation can be performed.
In the phase comparison method using the "charge pump" used in many PLLs, the frequency of phase comparison is once per cycle of the signal, but in the phase comparison unit 131 that performs the above calculation, it is arbitrary. Since the phase difference can be obtained based on the instantaneous value of the time, it is possible to compare the phase a plurality of times in one cycle of the signal.

For example, when the operating frequencies of the ADC1, ADC2, and the two-phase sine wave generator 133 are set to a constant value of 375 kHz, the phase comparison is performed at 375 kHz for each sampling data even when the frequency of the reference signal is 50 Hz.

As a result, not only the responsiveness of the PLL 130 can be improved, but also the average of a large number of phase comparison results can be obtained by the loop filter 132, so that stable operation with respect to noise becomes possible.

The main characteristic of the loop filter 132 is the same proportional / integral characteristic as that of a normal PLL loop filter, except that the loop filter 132 is configured by using a digital filter technique.

Generally, the instantaneous phase is obtained by time-integrating the angular frequency ω of the two-phase sine wave generation unit 133, and the difference between the phase and the instantaneous phase of the input signal is obtained from the phase comparison unit 131. Here, the conversion ratio (that is, the gain) when the output of the phase comparison unit 131 is expressed by [rad] and the input of the two-phase sine wave generation unit 133 is expressed by [rad / s] is set to 1, and the loop filter 132 is used. If the control loop is constructed with the gain as the proportional characteristic of k, the round-trip gain of the control loop has the integral characteristic, and s is the operator of the Laplace transform.
Round gain = k / s
Is. Further, the gain crossing angle frequency, which is the angular frequency at which the magnitude of the round-trip gain becomes 1, is
Gain crossing angular frequency = k
The reciprocal 1 / k of the gain crossing angular frequency is the response time constant.

In this way, since the round-trip gain has an integral characteristic, the angular frequency ω of the two-phase sine wave generator 133 matches the input angular frequency without a steady deviation just by setting the loop filter 132 as a proportional characteristic. Produces a steady deviation proportional to the oscillation frequency.

Therefore, in order to suppress the steady phase deviation and obtain a stable PLL operation, the characteristics of the loop filter 132 are integrated in the low frequency range and proportional to the gain intersection frequency to secure the phase margin. However, in the high frequency region, the two-phase sine wave generation unit 133 is provided with an attenuation characteristic so as not to cause unnecessary shaking.

The operation reference signal, which is the output of the PLL 130, is input to the AC voltage output unit 200 and the AC current output 300.

The AC voltage output unit 200 includes a first phase rotation unit 201, a second phase rotation unit 202, a DAC 203, a multiplication type DAC 204, a voltage amplification unit 205, a voltage detection unit 206, an ADC 207, an orthogonal detection unit 208, and a phase correction value calculation unit 209. , The amplitude control unit 210 is provided.

The AC current output unit 300 includes a first phase rotation unit 301, a second phase rotation unit 302, a DAC 303, a multiplication type DAC 304, a current amplification unit 305, a current detection unit 306, an ADC 307, an orthogonal detection unit 308, and a phase correction value calculation unit 309. , The amplitude control unit 310 is provided.

Since the operations of the AC voltage output unit 200 and the AC current output unit 300 are almost the same, the operation will be described below using the AC voltage output unit 200 as an example.

The e ^jωt , which is the output of the two-phase sine wave generation unit 133 of the PLL 130, is input to the first phase rotation unit 201. The voltage phase shift amount θv set by the control unit 110 is set in the first phase rotation unit 201. In the case of a master, θv = 0 may be set.

The first phase rotation unit 201 generates a complex sinusoidal wave signal whose phase is rotated by θv by complexly multiplying the output e ^jωt of the PLL 130 by θv. That is, by complexly multiplying cos (θv) + jsin (θv) = e ^jθ ,
e ^jωt・ e ^jθv = e ^{j (ωt + θv)}
Is obtained.

The output of the first phase rotation unit 201, ej ^{(ωt + θv)} , is input to the second phase rotation unit 202 and the orthogonal detection unit 208. The second phase rotating unit 202 performs phase correction based on the difference between the output of the first phase rotating unit 201 and the phase of the AC voltage actually output from the AC voltage output unit 200.

In the conventional AC signal generator 500, no measure is taken for the phase error generated after the phase rotation calculation, but in the AC signal generator 100 of the present embodiment, the difference between the actually output phase and the target phase is measured. Since the correction is performed based on the above, the phase control accuracy can be improved.

That is, the actually output AC voltage is detected by the voltage detection unit 206, converted into a digital signal by the ADC 207, and input to the orthogonal detection unit 208.

In the orthogonal detection unit 208, the signal input from the ADC 207 is multiplied by ej ^{(ωt + θv)} , which is the conjugate complex number of ej ^{(ωt + θv)} , which is the output of the first phase rotation unit 201, and the smoothed complex number is output. do.

Here, it is assumed that θv = θ and the output of the ADC 207 is Acos (ωt + φ) when the output AC voltage of the AC voltage output unit 200 is the amplitude A and the phase φ.
Acos (ωt + φ) = A / 2 (ej ^{(ωt + φ)} + e- ^{j (ωt + φ)} )
Therefore, the multiplication result of the orthogonal detection unit 208 is
A / 2 (e ^{j (ωt + φ)} + e- ^{j (ωt + φ)} ) · e- ^{j (ωt + θ)} = A / 2 (e ^{j (φ-θ)} + e- ^{j (2ωt + θ-φ)} )
Will be.

By smoothing the multiplication result, the term of e ^{-j (2ωt + θ-φ)} that vibrates at 2ωt is removed, and the output of the orthogonal detection unit 208 is
A / 2 · e ^{j (φ-θ)} = A / 2 (cos (φ-θ) + jsin (φ-θ))
As a result, each value can be obtained for both the real part and the imaginary part.

In the settling state, (φ−θ) = 0, and at this time, the output of the orthogonal detection unit 208 is A / 2 + j0.

Here, the signal input from the ADC 207 is multiplied by ej ^{(ωt + θv)} , which is the conjugate complex number of ej ^{(ωt + θv)} , which is the output of the first phase rotating unit 201, but the complex conjugate is not taken. You may multiply by ej ^{(ωt + θv)} as it is. In this case, the polarity of the imaginary portion of the output of the orthogonal detection unit 208 is inverted, but the subsequent phase correction value calculation unit 209 and the second phase rotation unit 202 may perform an operation in consideration of the polarity.

The output of the orthogonal detection unit 208 is input to the phase correction value calculation unit 209 and the amplitude control unit 210.

Here, assuming that the output of the orthogonal detection unit 208 is x + jy, the phase correction value calculation unit 209 will use the phase correction value calculation unit 209.
Phase error (φ-θ) = tan ^-1 (y / x)
Is corrected by subtracting (φ−θ) from the current correction value θadj, and cos (θadj) + jsin (θadj) is calculated from the corrected correction value θadj to the second phase rotation unit 202. Output. In this way, the phase correction value is calculated by the processing in the orthogonal detection unit 208 and the processing in the phase correction value calculation unit 209.

The second phase rotation unit 202 calculates the real part of the product of this cos (θadj) + jsin (θadj) and the complex sine wave ej ^{(ωt + θv)} input from the first phase rotation unit 201, and inputs it to the DAC 203. And convert it to an analog sine wave signal.

On the other hand, the amplitude control unit 210 calculates the amplitude of the output AC voltage of the AC voltage output unit 200 from √ (x ² + y ² ), which is the absolute value of the output of the orthogonal detection unit 208. The voltage amplitude Av that the control unit 110 has accepted is set in the amplitude control unit 210, and a digital value based on the ratio of the calculated amplitude and the voltage amplitude Av is output to the multiplication type DAC 204.

The multiplication type DAC 204 adjusts the amplitude based on the output of the amplitude control unit 210 and outputs the amplitude to the voltage amplification unit 205, so that the AC voltage is output via the output transformer.

In this way, the orthogonal detection unit 208, which is less susceptible to noise, is used to detect and correct the phase difference between the output AC signal and the output value of the first phase rotation unit 201 of the target phase. The phase error can be reduced and the phase control accuracy can be improved.

Here, if the phase error (φ−θ) is small, the absolute value of the output of the orthogonal detection unit 208 can be approximated by the real part x, so that the calculation amount can be reduced by this approximation. However, since the amplitude is set after the phase is set, the set time is slightly deteriorated.

In the conventional AC signal generator 500, the control unit 510, the two-phase sine wave generator unit 520, the amplitude detection unit 570, and the amplitude control unit 580 perform processing by digital arithmetic processing, and the phase rotation arithmetic performs analog arithmetic processing. .. Therefore, there is a risk that the phase control accuracy may decrease due to an analog error such as a resistance error.

On the other hand, in the AC signal generator 100 of the present embodiment, the control unit 110, the two-phase sine wave generator 120, the PLL 130, the first phase rotation units 201 and 301, the second phase rotation units 202 and 302, and the orthogonal detection unit Various processes in 208, 308, phase correction value calculation units 209, 309, and amplitude control units 210, 310 are performed by digital arithmetic processing. Therefore, the required calculation resolution can be easily obtained, and the phase control accuracy can be improved.

100 ... AC signal generator, 110 ... Control unit, 120 ... Two-phase sine wave generator, 130 ... PLL, 131 ... Phase comparison unit, 132 ... Loop filter, 133 ... Two-phase sine wave generator, 200 ... AC voltage output Unit, 201 ... 1st phase rotating unit, 202 ... 2nd phase rotating unit, 203 ... DAC, 204 ... multiplying type DAC, 205 ... voltage amplification unit, 206 ... voltage detecting unit, 207 ... ADC, 208 ... orthogonal detection unit, 209 ... phase correction value calculation unit, 210 ... amplitude control unit, 300 ... AC current output, 300 ... AC current output unit, 301 ... first phase rotation unit, 302 ... second phase rotation unit, 303 ... DAC, 304 ... multiplication Type DAC, 305 ... current amplification unit, 306 ... current detection unit, 307 ... ADC, 308 ... orthogonal detection unit, 309 ... phase correction value calculation unit, 310 ... amplitude control unit

Claims (5)

A reference signal generator that accepts frequency settings and generates a reference signal for the frequency,
A phase-locked loop unit that generates an operation reference signal that follows the reference signal generated by the reference signal generation unit or the reference signal input from the outside.
It is equipped with an AC signal output unit that outputs an AC signal synchronized with the operation reference signal.
The AC signal output unit is
A first phase rotating unit that accepts the setting of the phase shift amount prior to the output of the AC signal and shifts the phase of the operation reference signal according to the phase shift amount.
A phase difference detection unit that detects the phase difference between the output signal of the first phase rotation unit and the output AC signal, and
An AC signal generator comprising a second phase rotating unit that corrects the phase of the output signal of the first phase rotating unit based on the phase difference detected by the phase difference detecting unit. A reference signal generator that accepts frequency settings and generates a reference signal for the frequency,
A phase-locked loop unit that generates an operation reference signal that follows the reference signal generated by the reference signal generation unit or the reference signal input from the outside.
It is equipped with an AC signal output unit that outputs an AC signal synchronized with the operation reference signal.
The AC signal output unit is
A first phase rotating unit that accepts the setting of the phase shift amount and shifts the phase of the operation reference signal according to the phase shift amount.
A phase difference detection unit that detects the phase difference between the output signal of the first phase rotation unit and the output AC signal, and
A second phase rotation unit that corrects the phase of the output signal of the first phase rotation unit based on the phase difference detected by the phase difference detection unit is provided .
The phase synchronization unit, the first phase rotation unit, and the second phase rotation unit are AC signal generators characterized in that digital arithmetic processing is performed on a complex sine wave signal . The AC signal generator according to claim 1 or 2, wherein the phase difference detection unit includes an orthogonal detection unit. The claim is characterized by comprising an amplitude control unit that accepts an amplitude setting and controls the amplitude of an AC signal that is output based on the ratio of the amplitude calculated from the output signal of the orthogonal detection unit and the received amplitude. 3. The AC signal generator according to 3. The AC signal output unit is
The AC signal generator according to any one of claims 1 to 4, further comprising an AC voltage output unit that outputs an AC voltage signal and an AC current output unit that outputs an AC current signal.

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