JP3505626B2 - Power converter and power converter controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter and a controller for a power converter, and more particularly to controlling power between alternating current systems using a power converter composed of power semiconductor switching elements. The present invention relates to a suitable power converter and a controller for a power converter.

[0002]

2. Description of the Related Art A power converter that converts AC power from an AC system into DC power operates equivalently as a voltage source. Therefore, when controlling such a power converter, when the system voltage suddenly changes at the time of a system fault, the voltage of the power converter must be changed accordingly, or an overcurrent will flow. Therefore, a current control system with fast response is required.

Further, in performing such control, the control device for the power converter controls the input current or the output current by controlling the amplitude and phase of the output voltage.
It is necessary to detect the phase of the voltage of the AC system.

Conventionally, PLL (Phase-Locked Loo) has been used as a method for detecting the phase of the voltage of the AC system.
The one using the p) circuit is known.

The PLL circuit is provided with an oscillator, detects the phase difference between the input signal and the output signal so that the frequency and phase of the oscillator always match the frequency and phase of the input signal, and the detected value becomes zero. Feedback control is performed. By using this PLL circuit, the firing angle can be determined with reference to the synchronization point (zero cross) of the AC system. An example of using a PLL circuit is described in Japanese Patent Laid-Open No. 3-45126.

[0006]

However, the conventional PLL
Since the circuit controls the phase based on the zero point of the system voltage, an unbalanced voltage occurs in the system due to a ground fault in the AC system, etc. When superposed on the phase voltage, the anti-phase voltage cannot be removed. When the negative phase voltage is superimposed on the positive phase voltage, the zero point cannot be detected accurately due to chattering when the system voltage passes through the zero point due to waveform distortion, and the phase of the positive phase voltage can be calculated accurately. There is a problem that you cannot do it.

It is an object of the present invention to detect an accurate phase angle of a positive phase voltage even if a negative phase voltage is superposed on an AC voltage from a grid and perform power conversion control based on the detected value. It is to provide a control device for a device and a power converter.

[0008]

In order to achieve the above object, the present invention provides a power conversion means for converting AC power from an AC system into DC power in response to a control signal, and an AC system.
Phase conversion means for converting a three-phase AC signal into a two-phase AC signal;
Upon receiving each output signal of the phase converting means, the phase of each output signal is set to 9
Phase shift means for shifting the phase by 0 degree and each output signal of the phase conversion means
Positive phase voltage calculating means for calculating only the positive phase voltage component of the two-phase AC signal from each output signal of the phase means, and phase angle calculating means for calculating the phase angle of the positive phase voltage from the calculation result of the positive phase voltage calculating means. And a control signal generating means for generating a control signal according to the calculation result of the phase angle calculating means and outputting the control signal to the power converting means.

[0009]

[0010]

When configuring the power conversion device
Instead of the phase shift means and the positive phase voltage calculation means,
It can be configured by the following.

( 1) From delay means for receiving each output signal of the phase conversion means and generating a signal delayed by 90 degrees in phase from each output signal, and each output signal of the phase conversion means and each output signal of the delay means And a positive phase voltage calculating means for calculating only the positive phase voltage component of the two-phase AC signal.

( 2) Fourier transform means for receiving each output signal of the phase transform means and Fourier transforming each output signal, and phase shift for shifting the phase of one output signal of the output signals of the Fourier transform means by 90 degrees. having means and, and a positive phase voltage calculating means for calculating only the positive phase voltage component of the two-phase AC signals from the output signal of the output signal and the phase shifting means and the output signal from the Fourier transform means of the phase converting means.

( 3) Fourier transforming means for receiving each output signal of the phase transforming means and performing Fourier transform of each output signal, and one output signal of the output signals of the Fourier transforming means, and receiving the output signal of 90 degree phase from this signal. Positive phase voltage calculation for calculating only the positive phase voltage component of the two-phase AC signal from the phase advancing means for generating the advanced signal, the output signal of the phase converting means, the output signal of the Fourier transforming means and the output signal of the phase advancing means. Having means.

Further, when constructing the power conversion device, it is desirable to provide a correction means for adding a correction value considering the delay time associated with the calculation of the phase angle to the calculation result of the phase angle calculation means.

Further, when the power converter is constructed by using each of the above means, the controller for the power converter can be constructed by using other means except the power converter.

[0017]

According to the above means, even if the system voltage becomes unbalanced and the negative phase voltage is superimposed on the positive phase voltage of the AC system, the negative phase voltage is removed and only the positive phase voltage component is extracted. For,
The exact phase angle of the positive phase voltage can be detected. Therefore, if the power conversion control is performed based on the accurate phase angle of the positive phase voltage, it is possible to prevent the power converter from being stopped by the eddy current even if the system voltage becomes unbalanced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the power conversion device comprises a power converter 3, an operation command device 30, and a control device 31, and the AC input side of the power converter 3 is connected to the AC system 1 via the conversion transformer 2. The DC output side is connected to the capacitor 4. The control device 31 generates a control signal based on the operation command from the operation command device 30 and the AC voltage from the AC system 1, and the power converter 3 according to the control signal.
Is configured to control the conversion power of the.

The power converter 3 includes GTOs ( gate turn-off thyristors) 1 to 6 and diodes D1 to D6 having a self-extinguishing function as a self-excited power converter, and each GTO 1 has a three-phase bridge connection configuration. ~ GTO
6 and the diodes D1 to D6 are connected in antiparallel.
The power converter 3 may be a separately excited power converter using a semiconductor switching element such as a thyristor.

Here, the present invention is characterized in that when the negative phase voltage is superimposed on the positive phase voltage of the AC voltage, the negative phase voltage is removed and only the positive phase voltage component is extracted. In the embodiment, the control device 31 is configured in consideration of the formula shown below.

When the three-phase AC system voltages are ea, eb, and ec, if these AC voltages are converted into two-phase voltages,
The two-phase conversion to the fixed coordinate system α and β axes is performed according to the following formula 1.

[0023]

[Equation 1]

When the system voltage is only the positive phase voltage component,
The two-phase converted instantaneous voltages eα and eβ are expressed by the following equation 2 and the phase angle θ1 of the positive phase voltage is obtained.

[0025]

[Equation 2]

However, E1 indicates the effective value of the positive phase voltage, and θ1 indicates the phase angle of the positive phase voltage.

On the other hand, if the system voltage becomes unbalanced and the positive-phase voltage is superposed with the negative-phase voltage, the two-phase converted voltages eα, e
β is expressed by the following equation (3).

[0028]

[Equation 3]

However, the effective value of the anti-phase voltage is E2, and the phase angle of the anti-phase voltage is θ2.

In the above equation (3), the term of θ2 occurs as a disturbance. Therefore, if the term of θ2 is removed, only the positive phase voltage can be rescued.

Therefore, the following conversion is performed in consideration of the positional relationship between the positive phase voltage and the negative phase voltage on the vector.

That is, since eα and eβ are periodic functions,
Fourier transform is possible.

[0033]

[Equation 4]

In the equation (4), eα and eβ are obtained by expressing the equation (3) by a periodic function, and the sum of eα obtained by advancing the phase angle of eβ by 90 degrees is obtained as e1.

Fourier transform of eα and eβ in the equation 4 is expressed by the following equation.

[0036]

[Equation 5]

By advancing the phase angle of eβ in the equation 5 by 90 degrees, the following equation 6 is obtained.

[0038]

[Equation 6]

When the sum e1 of eα of the equation 5 and the equation 6 is obtained, the sum e1 is expressed by the following equation 7.

[0040]

[Equation 7]

Here, Eas, Ebc, Eac, Ebs in the equation obtained by Fourier transforming eα and eβ are coefficients of sine and cosine by Fourier transform, and based on voltage waveform data of one or half cycle of eα and eβ. It can be calculated by executing the following equation.

[0042]

[Formula 8]

Since e1 in the equation (4) and e1 in the equation (7) are equal to each other, when the equations of these equations are established and both sides are compared, si
nθ1, cosθ1, and E1 are represented by the following equations.

[0044]

[Equation 9]

As described above, the three-phase voltage is converted into the two-phase voltage, the converted voltage data is sampled for one or a half period, the sampled data is Fourier-transformed, and the Fourier-transformed data and the Fourier-transformed data are obtained. By performing a comparison operation with the data before being performed, it is possible to remove this even if a reverse-phase voltage occurs in the AC voltage of the system,
By extracting only the positive phase voltage component, the accurate phase angle of the positive phase voltage can be detected.

As a method for obtaining an accurate phase angle of the positive phase voltage without using the Fourier transform, the AC system voltage is set to 2
The voltage data obtained by phase conversion is stored for 1/4 cycle,
Based on this data, 90-degree phase delayed data (voltage data of 1/4 cycle before) is generated, the negative phase voltage is canceled by using this data and the instantaneous voltage data, and only the positive phase voltage component is extracted. The method to do this is shown below.

When data eα (-90 degrees) and eβ (-90 degrees) delayed by 90 degrees from the instantaneous voltage data are obtained based on the instantaneous voltage data of the two-phase voltage as shown in the equation (3). , Is expressed by the following equation.

[0048]

[Equation 10]

By performing the following calculation based on the equations (3) and (10), the negative-phase voltage term is erased and only the positive-phase voltage component can be extracted. Therefore, the correct phase angle of the positive phase voltage can be detected.

[0050]

[Equation 11]

As shown in FIG. 3, the control device 31 specifically includes a DC voltage detection circuit 301 and adders 302 and 30.
4, a reactive power detection circuit 303, a current conversion circuit 305, a voltage conversion circuit 306, a phase angle detection circuit 307, a current control circuit 308, an interface circuit 309, and a PWM control circuit 310. The DC voltage command value and the detection voltage of the DC circuit detected by the DC voltage detection circuit 301 are input to the adder 302 from the operation command device 30. The reactive power command value and the reactive power detection value detected by the reactive power detection circuit 303 are input to the adder 304 from the operation command device 30. Each of the adders 302 and 304 generates a signal according to the deviation of each input signal, and outputs this signal to the current control circuit 308. The current conversion circuit 305 is configured to convert the three-phase alternating current into two phases and output the two-phase converted current to the current control circuit 308. The voltage conversion circuit 306 is based on the equation 2 or the equation 3 described above.
According to the formula, it is configured as a phase conversion means for converting the three-phase AC voltage into two phases, and the two-phase voltages eα and eβ are input to the phase angle detection circuit 307.

The phase angle detection circuit 307 is a voltage conversion circuit 30.
6 based on the output voltage of the positive phase voltage θ1, sin
θ1 and cos θ1 are detected, and the detection output is detected by the current control circuit 3
08 and the PWM control circuit 310. The current control circuit 308 generates a control signal indicating the control amount converted into the real axis component and the imaginary axis component based on the signals from the adders 302 and 304, the current conversion circuit 305, and the phase angle detection circuit 307, and this control signal Is output to the interface circuit 309. Interface circuit 30
Reference numeral 9 converts the two-phase voltage input from the current control circuit 308 into a three-phase voltage, and the converted three-phase voltage is PWM control circuit 31.
It is designed to output to 0. PWM control circuit 310
Generates a PWM control signal which becomes a gate pulse of the power converter 3 according to the phase angle θ1 of the positive phase voltage, and generates the generated PWM
It is configured to apply the control signal to the gates of GTO1 to GTO6.

As a concrete configuration of the phase angle detecting circuit 307, one using Fourier transform is shown in FIG. 4, and one using 90 degree delay data is shown in FIG.

In FIG. 4, the phase angle detection circuit 307 is
A Fourier transform circuit 501, adders 502 and 503, multipliers 504 and 505, an adder 506, a calculator 507, dividers 508, 509 and 510, and a calculator 511 are provided. The Fourier transform circuit 501 performs an FFT operation on the two-phase voltages eα and eβ calculated by the voltage transform circuit 306 to obtain the sine / cosine coefficients Eas, Ebc, Eac, Eb
s is calculated. When the AC voltage is Fourier-transformed, the sine and cosine coefficients are generally calculated by FFT calculation from data obtained by dividing one cycle of the AC voltage into N. However, in the present embodiment, control in the power system is considered. However, assuming that the frequency is substantially constant, the detection of the waveform of the AC voltage is not strictly performed in one to half cycles, and is approximately a constant period, for example, 20 ms for 50 Hz and 16.
A 7 ms waveform is detected and Fourier transform is performed.

The coefficients calculated by the Fourier transform circuit 501 are output to adders 502 and 503, respectively. Then, the adder 502 obtains the difference between Eas and Ebs, and the adder 503 obtains the sum of Eac and Ebs.
Further, in the multiplier 504, the output (Eas−
The square of Ebc) is obtained, and the multiplier 505 obtains the square of the output (Eac + Ebs) of the adder 503.
The outputs of the multipliers 504 and 505 are added by the adder 506. On the other hand, the computing unit 507 obtains E1 which is the square root of (Eas−Ebc) ² + (Eac + Ebs) ² as shown in Expression 9. When E1 is calculated by the arithmetic unit 507, the output of the adder 502 is E by the divider 508.
It is divided by 1 to obtain sin θ1. Also the divider 5
The output of the adder 503 is divided by E1 at 09, and sin θ
1 is required. When cos θ1 and sin θ1 are obtained, they are divided by the divider 510 to obtain tan θ.
When 1 is calculated, the phase angle θ1 of the positive phase voltage is calculated by the calculator 511 based on tan θ1. Since this phase angle θ1 is calculated only from the positive phase voltage, it indicates an accurate phase angle of the positive phase voltage.

On the other hand, the phase angle detection circuit 507 shown in FIG. 5 includes a memory 601, adders 602 and 603, a divider 604,
It is configured to include computing units 605, 606, and 607. The memory 601 stores the instantaneous voltage data of the two-phase voltages eα and eβ converted by the voltage conversion circuit 306 for ¼ cycle (instantaneous voltage data before ¼ cycle). Output is sequentially added by the adder 602,
It is designed to be output to 603. The adder 602 outputs the instantaneous voltage data eα and 1 / output from the memory 601.
A difference from the voltage data eα (−90 degrees) delayed by 90 degrees, which is the voltage data four cycles ago, is obtained. The adder 603 uses the instantaneous voltage data eβ and the memory 601.
90 which is the instantaneous voltage data before 1/4 cycle obtained from
The sum is obtained with the instantaneous voltage data eα (−90 degrees) whose phase is delayed.

In the adders 602 and 603, after the calculation as shown in the equation (11) is performed, each adder 602,
When the output of 603 is output to the divider 604, the divider 6
In 04, the ratio of the two calculated values is obtained, and tan θ1
Is required. When this calculated value is input to the calculator 605, the calculator 605 obtains the phase angle θ1 of the positive phase voltage. Since this value is also calculated only from the positive phase voltage component, it indicates an accurate phase angle. In addition, the calculator 605
Based on the calculated value of, the arithmetic unit 606 obtains sin θ1 and the arithmetic unit 607 obtains cos θ1.

As described above, in this embodiment, even if the negative phase voltage is superposed on the AC voltage of the system, the negative phase voltage component is removed, only the positive phase voltage component is extracted, and the positive phase voltage component is positively extracted. Since the accurate phase angle of the phase voltage is detected, even if the system voltage becomes unbalanced due to a system fault or the like and the reverse phase voltage occurs, the correct phase of the positive phase voltage is detected and the unbalance compensation control is performed. Therefore, stable operation of the power converter can be performed, and the power converter 3 can be prevented from being stopped by the eddy current.

Further, in the above embodiment, when the phase angle θ1 of the positive phase voltage is calculated and the power conversion control of the power converter 3 is executed based on the calculated phase angle θ1, the calculated phase angle θ1 is calculated. By adding a correction value in consideration of the delay time associated with the above to the calculated value, the shift of the phase angle due to the processing time can be corrected.

[0060]

As described above, according to the present invention,
Only the positive phase voltage component is extracted from the AC voltage of the system, the phase angle of the positive phase voltage is detected only from the extracted positive phase voltage component,
Since the power conversion control is executed based on this detected value, even if the system voltage becomes unbalanced and the reverse phase voltage is superimposed on the system voltage, this is removed and only the positive phase voltage component is extracted,
An accurate phase angle of the positive phase voltage can be obtained, and power conversion control can always be performed in a stable state.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a power conversion system showing an embodiment of the present invention.

FIG. 2 is a specific configuration diagram of a power converter.

FIG. 3 is a specific configuration diagram of a control device.

FIG. 4 is a specific configuration diagram of a phase angle detection circuit using Fourier transform.

FIG. 5 is a specific configuration diagram of a phase angle detection circuit using 90-degree delay data.

[Explanation of symbols]

1 AC system 2 conversion transformer 3 Power converter 4 capacitors 30 Operation command device 31 Control device 301 DC voltage detection circuit 303 Reactive power detection circuit 305 Current conversion circuit 306 Voltage conversion circuit 307 Phase angle detection circuit 308 Current control circuit 309 Interface circuit 310 PWM control circuit 501 Fourier transform circuit 502, 503 adder 504, 505 multiplier 506 adder 507 calculator 508, 509, 510 Divider 511 arithmetic unit 601 memory 602 and 603 adder 604 divider 605, 606, 607 calculator

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichiro Furuseki, 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Ltd., within the Hitachi Plant (56) Reference JP-A-4-248368 (JP, A) ( 58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 3/00-5/00 H02M 7/155

Claims (8)

(57) [Claims] 1. Power conversion means for converting AC power from an AC system into DC power in response to a control signal, and phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal.
Upon receiving each output signal of the phase converting means, the phase of each output signal is set to 9
Positive phase voltage calculation means for calculating only the positive phase voltage component of the two-phase AC signal from the phase shift means for shifting the phase by 0 degree, each output signal of the phase conversion means and each output signal of the phase shift means, and the positive phase voltage Phase angle calculation means for calculating the phase angle of the positive phase voltage from the calculation result of the calculation means, and control signal generation means for generating a control signal according to the calculation result of the phase angle calculation means and outputting this control signal to the power conversion means. Power converter provided. 2. Power conversion means for converting AC power from the AC system into DC power in response to a control signal, and phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal.
A delay unit that receives each output signal of the phase conversion unit and generates a signal delayed by 90 degrees in phase from each output signal, and a positive two-phase AC signal from each output signal of the phase conversion unit and each output signal of the delay unit. Positive phase voltage calculation means for calculating only the phase voltage component, phase angle calculation means for calculating the phase angle of the positive phase voltage from the calculation result of the positive phase voltage calculation means, and a control signal generated according to the calculation result of the phase angle calculation means. A power conversion device comprising: a control signal generation means for outputting the control signal to the power conversion means. 3. Power conversion means for converting AC power from the AC system into DC power in response to a control signal, and phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal.
Fourier transforming means for receiving each output signal of the phase transforming means and Fourier transforming each output signal, phase shifting means for shifting the phase of one output signal of the Fourier transforming means by 90 degrees, and phase transforming means Positive phase voltage calculation means for calculating only the positive phase voltage component of the two-phase alternating current signal from the output signal of the Fourier transform means and the output signal of the phase shift means, and the positive phase from the calculation result of the positive phase voltage calculation means. A power conversion device comprising: a phase angle calculation means for calculating a phase angle of a voltage; and a control signal generation means for generating a control signal according to a calculation result of the phase angle calculation means and outputting the control signal to the power conversion means. 4. Power conversion means for converting AC power from the AC system into DC power in response to a control signal, and phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal.
Fourier transform means for receiving each output signal of the phase transform means and performing Fourier transform of each output signal, and receiving one output signal of the output signals of the Fourier transform means to generate a signal with a phase advanced by 90 degrees from this signal. A phase advancing means, a positive phase voltage calculating means for calculating only a positive phase voltage component of the two-phase AC signal from the output signal of the phase converting means, the output signal of the Fourier transforming means and the output signal of the phase advancing means, and the positive phase voltage. Phase angle calculation means for calculating the phase angle of the positive phase voltage from the calculation result of the calculation means, and control signal generation means for generating a control signal according to the calculation result of the phase angle calculation means and outputting this control signal to the power conversion means. Power converter provided. 5. The either one of the phase angle calculating means calculates the result according to claim 1, 2, 3 or comprises a correction means for adding the correction value in consideration of the delay time due to the calculation of the phase angle 4 1
The power converter according to the item . 6. A power converter for converting AC power from an AC system into DC power in response to a control signal, comprising: a phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal; and a phase conversion. 2 from the delay means for receiving each output signal of the means and generating a signal whose phase is delayed by 90 degrees from each output signal, and each output signal of the phase conversion means and each output signal of the delay means.
Positive phase voltage calculation means for calculating only the positive phase voltage component of the phase alternating current signal, phase angle calculation means for calculating the phase angle of the positive phase voltage from the calculation result of the positive phase voltage calculation means, and calculation result of the phase angle calculation means And a control signal generating means for generating a control signal according to the above and outputting the control signal to the power converter. 7. A power converter for converting AC power from an AC system into DC power in response to a control signal, comprising: a phase conversion means for converting a three-phase AC signal of the AC system into a two-phase AC signal; and a phase conversion. Fourier transform means for receiving each output signal of the means and Fourier transforming each output signal, and phase advance for receiving one output signal of the output signals of the Fourier transform means and generating a signal with a phase advanced by 90 degrees from this signal Means, a positive phase voltage calculating means for calculating only the positive phase voltage component of the two-phase AC signal from the output signal of the phase converting means, the output signal of the Fourier transforming means and the output signal of the phase advancing means, and the positive phase voltage calculating means. Phase angle calculation means for calculating the phase angle of the positive phase voltage from the calculation result, and control signal generation means for generating a control signal according to the calculation result of the phase angle calculation means and outputting the control signal to the power converter. Power Controller of the transducer. 8. The electric power according to claim 6, further comprising a correction unit that adds a correction value considering a delay time associated with the calculation of the phase angle to the calculation result of the phase angle calculation unit. Converter control unit.