JP5640842B2 - Power conversion apparatus and control method thereof - Google Patents

Description

  The present invention relates to a power conversion device having a power conversion unit connected to an AC power supply via a transformer, and a control method thereof.

  As this type of power conversion device, for example, the current on the primary side and the secondary side of the transformer interposed between the AC power supply and the self-excited conversion device is detected by a current detector, and the detected primary side current and The transformer excitation current component is calculated from the secondary current, the magnetic flux density DC component is calculated from the excitation current component, and the voltage command correction value is calculated from the magnetic flux density DC component and the magnetic flux density DC component command value. The power converter device which made it like is proposed (for example, refer to patent documents 1).

  Further, in a power conversion device configured by a self-extinguishing element and connected to an electric power system or a load via a transformer, a means (Hall element) for detecting the magnetic flux of the iron core of the transformer is provided, and the maximum value of the magnetic flux And a control device for the power converter that detects the center value of the minimum value and corrects the output voltage command value of the power converter based on the center value (see, for example, Patent Document 2). .

JP-A-10-56739 JP-A-7-28534 JP-A-53-128776

  By the way, in the conventional example described in Patent Document 1 as described above, the current on the primary side and the secondary side of the transformer is detected, and the excitation current component of the transformer is calculated from the deviation between the two currents. A magnetic flux density DC component is calculated from the exciting current component, and a voltage command value correction value is calculated from the magnetic flux density DC component and the magnetic flux density DC component command value. However, in the power conversion device described in Patent Document 1, the magnetic flux density component is not directly detected, but the magnetic flux density component is calculated from the primary and secondary currents of the transformer. There is an unsolved problem that the magnetic flux density of the device cannot be detected accurately.

  On the other hand, in the conventional example described in Patent Document 2, the magnetic flux density of the transformer is detected using a Hall element, and the Hall element is a main iron core magnetic path through which the main magnetic flux flows. The main magnetic flux can be directly detected by embedding in the magnetic field, and the output voltage of the Hall element becomes an output proportional to the main magnetic flux. In addition, the Hall element is usually embedded in the gap of the transformer. In this case, the main magnetic flux can be measured correctly, but it is necessary to use a special-purpose transformer embedded with the Hall element. At the same time, when a Hall element is embedded in an iron core without a gap, there is an unsolved problem that the flow of the magnetic flux in that portion is disturbed and the main magnetic flux cannot be measured accurately.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-mentioned conventional example, and without using a Hall element, the main magnetic flux of the transformer is detected and the bias of the transformer is accurately determined. It is an object of the present invention to provide a power converter that can be detected and a control method thereof.

  In order to achieve the above object, a power converter according to an embodiment of the present invention includes a power converter that includes a power converter that is connected to an AC power source via a transformer and outputs AC power to the transformer. And a phase of an AC power supply voltage corresponding to a region where the leakage flux in the search coil voltage corresponding to the leakage flux detected by the search coil is directed to a positive or negative peak. An integration operation unit that individually integrates the regions and holds both final integration values as a first final integration value and a second final integration value; and a first final integration value and a second integration value of the integration calculation unit A bias amount calculating unit that calculates the sum of final integrated values to calculate the amount of bias, and a command value correcting unit that corrects the command value of the power conversion unit with the amount of bias calculated by the bias amount calculating unit. It is characterized by having prepared.

Further, in the power conversion device according to another aspect of the present invention, the integration calculation unit integrates a range of 60 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value. And a second integration calculation unit that integrates a range of 240 ° to 360 ° of the AC power source and holds a final integration value.
Further, in the power conversion device according to another aspect of the present invention, the integration calculation unit integrates a range of 90 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value. And a second integration calculation unit that integrates a range of 270 ° to 360 ° of the AC power source and holds a final integration value.

Further, in the power conversion device according to another aspect of the present invention, the integration calculation unit integrates a range of 120 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value. And a second integration calculation unit that integrates a range of 300 ° to 360 ° of the AC power source and holds a final integration value.
Further, in the power conversion device according to another aspect of the present invention, the integral calculation unit integrates a range of 150 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integral value. And a second integration calculation unit that integrates a range of 330 ° to 360 ° of the AC power source and holds a final integration value.

Further, in the power conversion device according to another aspect of the present invention, each of the first integration calculation unit and the second integration calculation unit includes an integrator and a peak hold circuit that holds a final integration value of the integrator. It is characterized by having.
Further, in the power conversion device according to another aspect of the present invention, the integration calculation unit includes a phase adjustment function for adjusting an integration phase corresponding to a detection delay of the input coil voltage of the search coil. It is a feature.

  Moreover, the control method of the power converter device which concerns on one form of this invention is a control method of the power converter device which has a power converter connected to the alternating current power supply via the transformer, Comprising: The leakage magnetic flux of the said transformer Is detected by the search coil, the coil voltage corresponding to the leakage magnetic flux detected by the search coil is supplied to the integration calculation unit, and the region corresponding to the half portion where the leakage magnetic flux goes to the positive and negative peaks is individually integrated, Both final integration values are held as the first final integration value and the second final integration value, and the sum of the first final integration value and the second final integration value of the integration calculation unit is calculated by the bias amount calculation unit. The bias value is calculated and calculated, and the command value correction unit corrects the command value of the power conversion unit based on the calculated bias value.

According to the present invention, since the magnetic flux leakage of the transformer is detected by the search coil, it is not necessary to embed it in the transformer like the Hall element in the above-described conventional example, and it can also be applied to an existing transformer. The effect of being able to be obtained.
Also, there is no search coil that directly measures the main magnetic flux, and the search coil voltage is proportional to the change (differentiation) of the leakage magnetic flux leaking outside from the main iron core. If it becomes a leakage magnetic flux. On the other hand, when the main magnetic flux increases and becomes saturated, the leakage magnetic flux increases. Therefore, by calculating the leakage magnetic flux, it is possible to accurately detect the magnetic bias of the transformer.

It is a block diagram which shows one Embodiment of the power converter device which concerns on this invention. FIG. 2 is a waveform diagram for explaining a steady-state bias detection operation in the embodiment of FIG. 1. It is a wave form diagram explaining the demagnetization detection operation | movement of the demagnetization state of embodiment of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a power converter according to the present invention.
In the figure, 1 is a power conversion device, and this power conversion device 1 includes a self-excited inverter 4 as a power conversion unit whose output side is connected to an AC power system 2 via a transformer 3. A DC power source 5 such as a capacitor or a battery is connected to the input side of the self-excited inverter 4. The self-excited inverter 4 includes semiconductor switching elements such as six insulated gate bipolar transistors (IGBT) and power field effect transistors.

Therefore, the DC power of the DC power source 5 is converted into AC power by the self-excited inverter 4, and the converted AC power is supplied to the primary side winding 3a of the transformer 3, and the secondary side winding 3b of the transformer 3 is converted. Is supplied to an AC power system 2 serving as an AC power source.
Each semiconductor switching element of the self-excited inverter 4 is driven and controlled by the control circuit 10. The control circuit 10 includes an inverter drive circuit 11 that drives each semiconductor switching element of the self-excited inverter 4, a search coil 12 that detects the leakage flux φ _L of the transformer 3, and a bias that calculates the bias of the transformer 3. A bias amount calculation circuit 13 as a magnetic amount calculation unit is provided.

  The inverter drive circuit 11 includes a subtracter 23 that subtracts the output current detection value id output from the current sensor 22 that detects the output current of the self-excited inverter 4 from the current command value ic output from the current command setter 21. . The current deviation Δi output from the subtracter 23 is supplied to the regulator 24. The regulator 24 controls proportionality, integration, differentiation, and the like based on the current deviation Δi between the current command value ic and the current detection value id. An adjustment output current iad output from the adjuster 24 is supplied to an adder 25 as a command value correction unit. The adder 25 adds the bias amount correction value ico input from the bias amount calculation circuit 13 to the adjustment output current iadj, and the added output iadd is supplied to the pulse width modulation (PWM) circuit 26. The pulse width modulation circuit 26 performs pulse width modulation processing on the added output iadd to generate a pulse width modulation signal Ppwm for each semiconductor switching element of the self-excited inverter 4, and the generated pulse width modulation signal Ppwm is used for each semiconductor of the self-excited inverter 4. Supplied to the switching element.

The search coil 12 detects a leakage magnetic flux φ _L leaking outside from the main iron core of the transformer 3, and outputs a search coil voltage Vsc having a differential waveform obtained by differentiating the leakage magnetic flux φ _L.
In the bias amount calculation circuit 13, the search coil voltage Vsc output from the search coil 12 is supplied to a low-pass filter (LPF) 31. The low-pass filter 31 removes noise and ripples from the search coil voltage Vsc, and a filter output from which the noises and ripples are removed is supplied to the integration calculation unit 32.

The integration calculation unit 32 includes a first integrator 33 and a second integrator 34 and sample hold circuits 35 and 36 to which filter outputs are input together.
The first integrator 33 integrates the range of 90 ° to 180 ° of the AC power supply voltage output from the self-excited inverter 4 and outputs the final integrated value Vi1e. The second integrator 34 integrates the range of 270 ° to 360 ° of the AC power supply voltage and outputs a final integrated value Vi2e.
Then, the final integration values Vi1e and Vi2e output from the first integrator 33 and the second integrator 34 are supplied to the sample hold circuits 35 and 36, respectively, and the final integration values Vi1e are supplied by the sample hold circuits 35 and 36, respectively. And Vi2e are sampled and held.

  The final integrated values Vi1e and Vi2e held by these sample and hold circuits 35 and 36 are supplied to an adder 37 that calculates the amount of magnetic bias by calculating the sum of both. The demagnetization amount output from the adder 37 is supplied to the adjuster 38, and the demagnetization amount correction value ico that is adjusted so that the demagnetization amount output from the adder 37 becomes zero is calculated. Then, the bias amount correction value ico output from the regulator 38 is supplied to the adder 25 of the inverter drive circuit 11.

  In the bias amount calculation circuit 13, a phase delay occurs in the search coil voltage Vsc that has passed through the low-pass filter 31 because the low-pass filter 31 that removes noise and ripples is interposed on the output side of the search coil 12. Therefore, it is necessary to measure this phase delay and adjust the integration phases of the first integrator 33 and the second integrator 34 in accordance with the phase delay.

Next, the operation of the above embodiment will be described.
Now, in a steady state magnetic deflection in the transformer 3 does not occur, the leakage magnetic flux phi _L of the transformer 3, as shown in FIG. 2 (b), the AC power supply shown in more high magnetic flux density FIGS. 2 (a) Leakage concentrates in the vicinity of the voltage phase of 180 ° and 360 ° of the voltage Vac, and the positive direction is around 180 ° and the negative direction is around 360 °. That is, the leakage flux φ _L starts to increase in the positive direction from about 120 ° of the AC power supply voltage Vac, reaches a peak value in the positive direction at 180 °, then decreases and returns to zero at about 240 °, and then returns to about 330 °. Starts to increase in the negative direction and reaches a peak value in the negative direction at 360 ° and then decreases to zero at about 60 °.

The search magnetic flux φ _L is detected by the search coil 12, and the search coil voltage Vsc has a differential waveform obtained by differentiating the leak magnetic flux φ _L as shown in FIG. For this reason, the search coil voltage Vsc increases in the positive direction from about 120 ° of the AC power supply voltage Vac, reaches a peak value in the positive direction at about 160 °, then decreases to zero at 180 °, and then increases in the negative direction. Then, the peak value in the negative direction is reached at about 200 °, and then decreases and returns to zero at about 240 °. Furthermore, it increases in the negative direction from about 330 °, reaches a negative peak value at about 340 °, then decreases and returns to zero at 360 °, and then increases in the positive direction to about 380 ° (about 20 ° ) At the peak value in the positive direction, then decreases and returns to zero at about 450 ° (about 70 °).

For this reason, in the first integrator 33, the integration is performed in the range of 90 ° to 180 ° of the AC power supply voltage Vac, so that the integration value is equal to the leakage flux Φ _{L as} shown in FIG. Thus, the final integrated value + Vi1e of the AC power supply voltage Vac at 180 ° is sampled and held by the sample and hold circuit 35.
Similarly, the second integrator 34 performs integration in the range of 270 ° to 360 ° of the AC power supply voltage Vac, so that the integration value is equal to the leakage flux Φ _{L as} shown in FIG. Thus, the final integrated value −Vi2e at 360 ° of the AC power supply voltage Vac is sampled and held by the sample and hold circuit 36.

  The final integrated values Vi1e and Vi2e output from the sample hold circuits 35 and 36 are supplied to the adder 37, and the sum of the final integrated values Vi1e and Vi2e is calculated as the amount of magnetic bias BM. At this time, when the AC power supply voltage Vac is 180 °, the sample hold circuit 35 samples and holds a new final integration value Vi1e. However, in the sample hold circuit 35, the final integration value −Vi2e at the previous 360 °. Therefore, the amount of bias BM output from the adder 37 becomes zero.

From this steady state, due to various factors such as transient DC voltage due to sudden change in the operating state of the power conversion unit composed of inverters and transient DC voltage from the AC power system side due to the inrush of the parallel transformer etc. When the biased state occurs, a large biased state as shown in FIG. 3 occurs.
At the transition from the steady state to the biased state, for example, as shown in FIG. 3B, the leakage magnetic flux φ _L at 180 ° of the AC power supply voltage Vac increases significantly in the positive direction, and conversely, 360 °. Assuming that the leakage magnetic flux φ _{L at 1} is decreased in the negative direction, the final integration value Vi1e of the first integrator 33 increases rapidly at the time of 180 °, and this is sampled and held by the sample hold circuit 35.

  At this time, since the sample hold circuit 36 samples and holds the final integrated value Vi2e of the second integrator 34 in the previous steady state as shown by the broken line, the amount of bias BM output from the adder 37 is As shown in FIG. 3E, the AC power supply voltage Vac increases rapidly at 180 °. Thereafter, when the final integrated value Vi2e of the second integrator 34 decreases in the negative direction as shown in FIG. 3D at 360 ° of the AC power supply voltage Vac, the amount of magnetic bias BM output from the adder 37 is decreased. Increases further.

  Therefore, the controller 38 calculates the bias amount correction value ico for making the bias amount BM zero, and supplies the bias amount correction value ico to the adder 25 of the inverter drive circuit 11. For this reason, the addition output of the adder 25 increases, and the pulse width of Ppwm of the pulse width modulation signal output from the pulse width modulation circuit 26 becomes longer. Therefore, the AC power output from the self-excited inverter 4 is increased, and the amount of magnetic bias of the transformer 3 is suppressed.

On the contrary, when the increase in the negative direction of the leakage flux φ _L at 360 ° is larger than the leakage flux φ _L at 180 ° of the AC power supply voltage Vac, the amount of magnetic bias output from the adder 37 is − By becoming BM, the bias amount correction value ico output from the regulator 38 increases in the negative direction. For this reason, the summed output output from the adder 25 of the inverter drive circuit 11 decreases, so that the pulse width of the pulse width modulation signal Ppwm output from the pulse width modulation circuit 26 is shortened and output from the self-excited inverter 4. The amplitude of the AC power that is generated is reduced, and the amount of bias is suppressed.

As described above, according to the embodiment, the search coil 12 detects the leakage flux φ _L of the transformer 3, and thus the search coil voltage having a waveform corresponding to the differential value of the leakage flux φ _L from the search coil 12. Vsc is obtained, and the search coil voltage Vsc is integrated in the range of 90 ° to 180 ° of the AC power supply voltage Vac by the first integrator 33, whereby an integrated value Vi1 corresponding to the leakage magnetic flux φ _L is obtained. The final integrated value Vi1e at 180 ° is sampled and held in the sample and hold circuit 35. Similarly, the integration value Vi2 corresponding to the leakage flux φ _L is obtained by integrating the AC power supply voltage Vac in the range of 270 ° to 360 ° by the second integrator 34, and the final integration value at 360 ° is obtained. Vi2e is sampled and held in the sample and hold circuit 36.

  Then, the final integrated values Vi1e and Vi2e sampled and held by the sample and hold circuits 35 and 36 are added by the adder 37, whereby the demagnetization amount BM can be calculated, and the demagnetization amount BM is suppressed. A bias amount correction value ico is output from the adjuster 38. The bias amount correction value ico is supplied to the adder 25 of the inverter drive circuit 11, and AC power for suppressing the bias amount BM is output to the primary winding 3 a of the transformer 3. Magnetic quantity can be suppressed.

At this time, the search coil 12 can detect the leakage flux φ _L of the transformer 3 outside the transformer 3, and embed a Hall element as in the conventional example described in Patent Document 2 described above, It is not necessary to use a transformer having a special configuration such as providing a gap in the iron core, and the search coil 12 is applied to the existing transformer 3, and the bias amount calculation circuit 13 and the inverter drive circuit 11 Only by adding the adder 25, the amount of bias BM of the transformer 3 can be accurately detected.

Moreover, by applying the search coil 12, the search search coil voltage Vsc output from the coil 12 leaks change in the magnetic flux phi _L becomes a voltage waveform proportional to (derivative), by integrating the search coil voltage Vsc The leakage magnetic flux φ _L can be obtained. On the other hand, when the main magnetic flux of the transformer 3 increases and becomes saturated, the leakage magnetic flux φ _L also increases. Therefore, by calculating the leakage magnetic flux φ _L , the magnetic bias of the transformer 3 can be detected. Thus, it is possible to detect the demagnetization by the demagnetization detection principle which is completely different from the Hall element described in the above.

  In addition, since the magnetism of the transformer 3 can be detected at a high speed of about half a cycle of the AC power supply voltage Vac, high-speed magnetism suppression control can be performed. Therefore, the magnetic flux margin can be reduced and the magnetic flux density can be increased, so that the transformer can be reduced in size and price. Here, when the self-excited inverter 4 composed of an inverter is applied, the magnetic flux margin causes a bias in the transformer 3 due to various factors as described above. On the other hand, if the demagnetization suppression control can respond instantaneously, there is no need for a magnetic flux margin, but there is always a delay time in the control response, and the case where it works in the demagnetization direction due to disturbance is pulled back with the demagnetization correction value . For this reason, a magnetic flux margin is required according to the control response speed so as not to demagnetize and cause an overcurrent. However, in this embodiment, since the response time for detecting the amount of magnetic bias can be shortened, the magnetic flux margin can be reduced.

  In the above embodiment, the case where the low-pass filter 31 that removes noise and ripple of the search coil voltage Vac output from the search coil 12 is inserted in the bias amount calculation circuit 13 has been described. However, the present invention is not limited to this. If the noise or ripple of the search coil voltage Vac is small, the low-pass filter 31 can be omitted. In this case, the integration phases of the first integrator 33 and the second integrator 34 are omitted. The adjustment function can be omitted.

In the above-described embodiment, the case where the first and second integrators 33 and 34 are provided has been described. However, one of the integrators is omitted, and the 90% of the AC power supply voltage Vac is obtained with one integrator. It is also possible to individually integrate the range of ° to 180 ° and the range of 270 ° to 360 °, and sample and hold the final integrated values of both ranges in separate sample and hold circuits.
Furthermore, in the above-described embodiment, the case where the inverter drive circuit 11 and the bias amount calculation circuit 13 are configured by hardware has been described. However, the present invention is not limited to this, and an arithmetic processing device such as a microcomputer is used. The pulse width modulation signal Ppwm and the bias amount correction value ico may be calculated by software.

In the above embodiment, the integration range of the first integrator 33 is 90 ° to 180 ° of the AC power supply voltage Vac, and the integration range of the second integrator 34 is 270 ° to 360 ° of the AC power supply voltage Vac. However, the present invention is not limited to this, and the leakage flux of the transformer 3 leaks in the vicinity of the voltage phases of 180 ° and 360 ° as the magnetic flux density increases. Since the voltage Vsc also increases in the vicinity thereof, the integration may be performed in a region corresponding to the half of the leakage flux φ _L toward the positive and negative peaks, for example, 120 ° to 180 ° and 300 to 360. It can be narrowed to the range of 150 °, 150 ° to 180 ° and 330 ° to 360 °, or can be expanded to the range of 60 ° to 180 ° and 240 ° to 360 °. _{According to L} What is necessary is just to set to the phase range which can detect the magnetic bias of the transformer 3. FIG.
Moreover, in the said embodiment, although the case where the self-excited inverter 4 was applied as a power converter was demonstrated, it is not limited to this, It is possible to apply other power converters, such as an AC-AC converter. it can.

  DESCRIPTION OF SYMBOLS 1 ... Power converter device, 2 ... AC power supply system, 3 ... Transformer, 4 ... Self-excited inverter, 5 ... DC power supply, 10 ... Control circuit, 11 ... Inverter drive circuit, 12 ... Search coil, 13 ... Calculation of amount of magnetization Circuit: 21 ... Current command setter, 22 ... Current sensor, 23 ... Adder, 24 ... Adjuster, 25 ... Adder, 26 ... Pulse width modulation circuit, 31 ... Low pass filter, 32 ... Integral calculation unit, 33 ... No. 1 integrator, 34 ... second integrator, 35, 36 ... sample and hold circuit, 37 ... adder, 38 ... regulator

Claims (8)

A power conversion device including a power conversion unit that is connected to an AC power source via a transformer and outputs AC power to the transformer,
A search coil for detecting leakage flux of the transformer;
The phase region of the AC power supply voltage corresponding to the region where the leakage magnetic flux is directed to the positive and negative peaks in the search coil voltage corresponding to the leakage magnetic flux detected by the search coil is individually integrated, and the final integration value of both is obtained as the first integration value. An integration operation unit that holds the final integration value and the second final integration value;
A bias amount calculator that calculates the amount of bias by calculating the sum of the first final integral value and the second final integral value of the integral calculator, and the command value of the power converter as the bias amount calculator A power conversion device comprising: a command value correction unit that corrects with the amount of magnetic bias calculated in step (1).   The integration calculation unit integrates a range of 60 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value, and 240 ° of the AC power supply. The power conversion device according to claim 1, further comprising a second integration calculation unit that integrates a range of ˜360 ° and holds a final integration value.   The integration calculation unit integrates a range of 90 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value, and 270 ° of the AC power supply. The power conversion device according to claim 1, further comprising a second integration calculation unit that integrates a range of ˜360 ° and holds a final integration value.   The integration calculation unit integrates a range of 120 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value; and 300 ° of the AC power supply. The power conversion device according to claim 1, further comprising a second integration calculation unit that integrates a range of ˜360 ° and holds a final integration value.   The integration calculation unit integrates a range of 150 ° to 180 ° of the AC power supply of the coil voltage detected by the search coil and stores a final integration value, and 330 ° of the AC power supply. The power conversion device according to claim 1, further comprising a second integration calculation unit that integrates a range of ˜360 ° and holds a final integration value.   6. Each of the first integration calculation unit and the second integration calculation unit includes an integrator and a peak hold circuit that holds a final integration value of the integrator. The power converter device according to any one of the above.   The said integration calculating part is provided with the phase adjustment function which adjusts the integral phase corresponding to the detection delay of the coil voltage of the said search coil input, The any one of Claim 1 thru | or 6 characterized by the above-mentioned. Power converter. A method for controlling a power converter having a power converter connected to an AC power source via a transformer,
Detecting the leakage flux of the transformer with a search coil,
A coil voltage corresponding to the leakage magnetic flux detected by the search coil is supplied to the integration calculation unit, and the region corresponding to the half portion where the leakage magnetic flux goes to the positive and negative peaks is individually integrated, and the final integration values of the two are obtained. Hold as the final integral value of 1 and the second final integral value,
The sum of the first final integral value and the second final integral value of the integral calculation unit is calculated by the bias amount calculation unit to calculate the amount of bias.
A command value correction unit corrects a command value of the power conversion unit based on the calculated amount of magnetic bias. A control method for a power converter.

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