JP6263990B2 - Synchronous control circuit for AC / DC converter - Google Patents

Description

  The present invention relates to an AC / DC converter connected to an AC power supply system, and more particularly to a synchronous control device for synchronizing the AC / DC converter with the same cycle as the system voltage of the AC power supply system.

  This type of AC / DC converter includes a secondary battery charging / discharging device for charging / discharging power to / from an AC power supply system, a reactive power adjustment device for an AC power supply system, and a harmonic generated by a load connected to the AC power supply system. There is an active filter that generates a current having a phase opposite to that of the wave current and cancels the harmonic current.

  FIG. 7 shows a circuit configuration of a secondary battery charge / discharge device as an example of the AC / DC converter connected to the AC power supply system. The charging / discharging device 10 provided between the AC power supply system 7 and the secondary battery 6 includes the interconnection breaker 1 provided at the connection point with the AC power supply system 7 and harmonics do not leak into the AC power supply system 7. LC filter (or LCL filter) 2 for detecting the voltage, voltage detector 3 for detecting system voltage Vs, current detection circuit 4 for detecting inverter current Iinv, and AC-DC conversion or DC-AC conversion IGBT unit 5.

  Furthermore, since the charging / discharging device 10 is connected to the AC power supply system 7 to charge / discharge the secondary battery 6, the output frequency, phase, voltage control and DC control on the AC side of the IGBT unit 5 are synchronized with the system voltage. Side output control is required.

  A configuration of a conventional synchronization control circuit is shown in FIG. The filter processing circuit 11 performs a filter process for removing noise of harmonic components due to the CR charge / discharge operation from one phase (RS phase in the figure) signal of the system voltage. The zero cross detection circuit 12 generates a system voltage pulse having the zero cross point of the sine wave as a change point (phase). The synchronization control unit 13 generates a sawtooth reference sine wave phase synchronized with the same cycle as the system voltage. The reference sine wave clock generation circuit 14 generates a reference sine wave clock having the same period as the sawtooth reference sine wave phase.

  FIG. 9 shows the relationship among the system voltage, system voltage zero cross, system voltage phase, reference sine wave, reference sine wave clock, and reference sine wave phase. As shown in FIG. 9, the slope of the reference sine wave phase is adjusted so that the phases of the reference sine wave and the system voltage match.

  The reference sine wave phase generated by the synchronization control unit 13 shown in FIG. 8 is used as a reference phase for gate control of the main circuit element (IGBT) of the IGBT unit 5 shown in FIG. The interconnection power from the secondary battery 6 to the AC power supply system 7 through the IGBT unit 5 is synchronized.

  FIG. 10 shows a method of controlling active power / reactive power using the reference sine wave phase generated by the synchronization control unit 13 of FIG.

  The reference sine wave generation circuit 31 generates a SIN wave and a COS wave having the same period as the reference sine wave phase generated by the synchronization control unit 13 of FIG. The multiplier 32a multiplies the SIN wave by the active current command value to adjust the amplitude, and the multiplier 32b multiplies the COS wave by the reactive current command value to adjust the amplitude. The adder 33 combines the sine wave outputs of the multipliers 32a and 32b to obtain a current command value. The current controller (ACR) 34 obtains a control current command value of active power / reactive power according to a deviation between the current command value and the output current IINV of the IGBT unit 5. The adder 35 adds the SIN wave of the base current in the reference sine wave to the control current command value to obtain the control current of the PWM circuit 36, and the IGBT unit 5 uses the PWM waveform gate signal generated by the PWM circuit 36. PWM control is performed on the gate.

  As described above, the AC / DC converter (charge / discharge device 10) linked to the AC power supply system 7 maintains the linked state by the synchronization control means. Here, when an abnormality such as voltage drop or waveform distortion occurs in the AC power supply system 7, the AC / DC converter (charge / discharge device 10) stops the operation / control of the AC / DC converter (charge / discharge device 10) by the system protection operation. Then, the interconnection breaker 1 is disconnected. When the AC power supply system 7 returns to normal, the interconnection breaker 1 is turned on again to resume the interconnection operation.

  In addition, as disclosed in Patent Document 2, a method for obtaining a phase by dq conversion of a system voltage is also disclosed.

JP 2012-70590 A JP 2008-177991 A

  In a PLL circuit using a zero-cross detection circuit as described in Patent Document 1, two types of zero-cross detection circuits are required to detect the phase difference between two signals, and the entire apparatus becomes expensive.

  In Patent Document 2, there are many complicated processes such as those that do not use a zero-crossing detection circuit and the phase obtained from the dq conversion result of the system voltage.

  As described above, in the synchronous control circuit of the AC / DC converter connected to the AC power supply system, it is a problem to reduce the cost of the device without using the zero cross detector and to simplify the processing.

  The present invention has been devised in view of the above-described conventional problems, and one aspect thereof is a synchronous control circuit that synchronizes an AC / DC converter connected to an AC power supply system at the same cycle as the system voltage. Based on the d-axis component and q-axis component of the voltage, the phase difference between the system voltage and the reference sine wave phase is 0 ° to 90 °, 90 ° to 180 °, 180 ° to 270 °, 270 ° to 360 °. It is determined which of these areas corresponds to the area determination circuit for outputting the q-axis component of the system voltage, and the PI calculation is performed so that the output of the area determination circuit is 0, and the PI calculation result is set to a preset value. A frequency command value calculation unit that calculates a frequency command value of a reference sine wave by resetting the PI calculation result to zero when reached, and a reference sine wave generation unit that generates a reference sine wave based on the frequency command value And.

  Further, as one aspect thereof, the region determination circuit is configured such that the phase difference between the system voltage and the reference sine wave phase is −1.0 [p. u. ] At 270 ° to 360 °, 1.0 [p. u. ] Is output.

  Further, as one aspect thereof, the frequency command value calculation unit sets an upper limit value for the frequency command value, and restricts the frequency command value from becoming higher than the upper limit value.

  Further, as one aspect thereof, an effective value of the system voltage is calculated, and weighting in proportion to the effective value is performed on the output of the region determination circuit.

  Further, as one aspect thereof, when the effective value of the system voltage is 5% or less, the weighting gain is set to 0.

  According to the present invention, in a synchronous control device for an AC / DC converter connected to an AC power supply system, it is possible to reduce the cost of the device without using a zero cross detector and to simplify the processing.

FIG. 2 is a block diagram illustrating a synchronization control circuit according to the first embodiment. The figure which shows the area | regions 1-4 of the d-axis component in a system voltage, and a q-axis component. The graph which shows the phase difference of a system voltage and a reference | standard sine wave phase, and the d-axis and q-axis component of a system voltage. Graph showing phase difference and frequency. FIG. 5 is a block diagram illustrating a synchronization control circuit according to a second embodiment. The graph which shows the relationship between the effective value of system voltage, and weighting gain. The circuit diagram which shows an example of the conventional AC / DC converter. The block diagram which shows an example of the conventional synchronous control circuit. The graph which shows the relationship between a sine wave and a phase. The block diagram which shows the control method of active power and reactive power using a reference | standard sine wave phase.

  According to the present invention, in order to generate a reference sine wave having the same phase as the system voltage, the system voltage is biaxially converted and dq converted, and the value of the q-axis component obtained by dq conversion using the rotational coordinates of the reference sine wave phase is set to zero Thus, the reference sine wave phase and the system voltage phase are made the same.

  Hereinafter, Embodiments 1 and 2 of the synchronous control device of the AC / DC converter according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 is a block diagram illustrating a synchronization control circuit of the AC / DC converter according to the first embodiment.

  As shown in FIG. 1, the three-phase system voltage Vs is αβ converted by the biaxial converter 41 to extract the biaxial voltage component, and this is dq converted by the dq converter 42 with the reference sine wave phase, The d-axis / q-axis components Vs_d and Vs_q on the rotational coordinates are extracted. The region determination circuit 43 performs input / output calculation based on the region from the d-axis / q-axis components Vs_d and Vs_q, and outputs the input / output calculation result to the frequency command value calculation unit 44. The area determination circuit 43 will be described later. The frequency command value calculation unit 44 performs PI calculation and limiter processing on the input / output calculation result of the region, and generates a reference sine wave phase from the output. The reference sine wave phase is used for dq conversion of the dq conversion unit 42. The reference sine wave generation unit 45 generates a reference sine wave based on the frequency command value.

When the system voltage is V _R = VmCOS (ωt−φ), V _S = VmCOS (ωt−2 / 3π−φ), V _T = VmCOS (ωt−4 / 3π−φ), and dq conversion is performed with the rotation coordinate of ωt. , Vd = V ₀ COSφ, Vq = −V ₀ SINφ. This φ is the phase difference between the system voltage and the reference sine wave. The calculation method is as follows.

When this phase difference φ is small, since Vq = −V ₀ SINφ≈−V ₀ φ, the same phase φ → 0 can be realized by setting Vq = 0.

  The input / output calculation by the area in the area determination circuit 43 is as follows. First, the region is divided into four as shown in FIG. Based on the d-axis component Vs_d and q-axis component Vs_q of the system voltage Vs, the phase difference φ corresponds to any region of 0 ° to 90 °, 90 ° to 180 °, 180 ° to 270 °, and 270 ° to 360 °. Judge whether to do. As shown in Table 1, the PI control input (output of the region determination circuit 43) in the frequency command value calculation unit 44 is changed depending on the region.

  FIG. 3 is a graph showing the phase difference φ between the system voltage and the reference sine wave phase and the d-axis component / q-axis components Vs_d and Vs_q of the system voltage Vs. The vertical axis is the output, and the horizontal axis is the phase difference φ.

  When the system voltage Vs is delayed (phase difference: 0 to 180 deg) with respect to the reference sine wave, the q-axis component Vs_q of the system voltage Vs takes a negative value. Therefore, when the q-axis component Vs_q is negative, the operation may be performed so that the frequency of the reference sine wave is lowered.

  On the other hand, when the system voltage Vs advances with respect to the reference sine wave (phase difference: 180 to 360 deg), the q-axis component Vs_q of the system voltage Vs takes a positive value. Therefore, when the q-axis component Vs_q is positive, the operation may be performed so that the frequency of the reference sine wave becomes high.

  In regions 1 and 4, the q-axis component Vs_q of the system voltage is used for the input of the PI calculation unit 44 a in the frequency command value calculation unit 44. In the area 2, −1 [p. u. ] In region 3, +1 [p. u. ] Is used. In addition, hysteresis is provided so that the output does not go back and forth between the regions 2 and 3.

  Since the PI calculation unit 44a of the frequency command value calculation unit 44 is an integral element, it increases monotonously, and when it reaches a predetermined value, when it is reset to 0, a sawtooth phase waveform is generated. The phase and frequency are determined by the inclination of the sawtooth, and a reference sine wave is generated. The system voltage Vs is again dq converted with the value here to obtain the q-axis component Vs_q, and the same repeated calculation is performed.

  For example, when the system voltage Vs is delayed by a phase difference φ (for example, 15 °) compared to the reference sine wave phase, a negative amount enters the PI calculation unit 44a of the frequency command value calculation unit 44, and becomes smaller than the previous value. The cycle becomes longer. By repeating this, Vq = 0 is stabilized. If an overshoot occurs and the lead phase is reached, the input to the PI calculation unit 44a is positive and the cycle is shortened. In any case, the operation is performed in the vicinity of Vs_q≈0 (φ≈0).

  The state of the phase difference φ and the frequency is shown in FIG. In FIG. 4, the upper limit value of the limiter 44b is 55 Hz. FIG. 4 shows a case where the initial phase difference φ is advanced, in the region 3 or 4, and the q-axis component Vs_q is positive. As a result, since the output of the PI calculation unit 44a is increased, the cycle is shortened and the frequency is increased. Here, it is limited to 55 Hz by the limiter 44b. The limiter 44b limits the sawtooth inclination and limits the frequency command value to the upper limit value.

  Although the phase difference φ decreases and the phase difference φ disappears at time t1, it overshoots and enters the region 1, and the q-axis component Vs_q becomes a negative value. For this reason, the output of the PI calculation unit 44a decreases, and the cycle becomes longer (frequency is lower). At time t2, the phase difference φ becomes zero again, and then a steady operation is performed in the vicinity of the phase difference φ = 0.

  Although the q-axis component Vs_q of the system voltage Vs and the phase difference φ are not in a linear relationship, the PI calculation unit 44a adjusts the frequency of the reference sine wave so that the phase difference φ becomes zero.

  Further, the q-axis component Vs_q of the system voltage Vs becomes maximum when the phase difference is φ = 90 deg (φ = 0 ° to 90 °, 270 ° to 360 °), and the value becomes smaller when it becomes larger than 90 deg. When the phase difference φ = 0 ° to 90 °, 270 ° to 360 °, the actual operation amount is desired to be large. u. ] For region 3, 1.0 [p. u. ] Is output. Thereby, when the phase difference φ is large, the convergence to the same phase is accelerated by using a large integral input.

  As described above, the synchronization control circuit of the AC / DC converter according to Embodiment 1 does not require a zero-cross detection circuit and can be realized with an inexpensive hardware configuration. Further, the method using the dq conversion result of the system voltage can be realized with a relatively simple software configuration.

[Embodiment 2]
Next, the synchronization control circuit of the AC / DC converter according to the second embodiment will be described. FIG. 5 is a block diagram illustrating a synchronization control circuit of the AC / DC converter according to the second embodiment. Description of the same parts as those in the first embodiment is omitted.

  As shown in FIG. 5, the synchronization control circuit according to the second embodiment performs A / D conversion on the system voltage by an A / D converter 46. The processes of the dq conversion unit 42 and the area determination circuit 43 are the same as those in the first embodiment. Also, an effective value RMS is calculated by the effective value calculation unit 47 based on the A / D converted system voltage, and a weighting gain is calculated by the weighting unit 48 based on the effective value RMS. Then, the multiplication unit 49 multiplies the output result of the region determination circuit 43 by the weighting gain, and outputs the multiplication result to the frequency command value calculation unit 44. Subsequent operations are the same as those in the first embodiment.

  An example of the weighting gain is shown in FIG. As shown in FIG. 6, when the effective value RMS is 5% or less, the weighting gain is set to zero. After 5%, the weighting gain is increased in proportion to the effective value RMS. Note that when the effective value RMS is 5% or less, the weighting gain is set to 0 in order to recognize that the system is out of power and not to synchronize with strange system voltage detection.

  The effective value RMS of the system voltage Vs is proportional to the dq conversion result. Therefore, like the synchronous control circuit of the AC / DC converter according to the second embodiment, the region determination circuit 43 is weighted with the effective value RMS of the system voltage Vs, so that the response of the synchronous control depends on the magnitude of the system voltage. Disappear.

  In addition, the same effects as those of the first embodiment are obtained.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

Vs ... system voltage Vs_d ... d-axis component Vs_q ... q-axis component φ ... phase difference 41 ... biaxial conversion unit 42 ... dq conversion unit 43 ... region determination circuit 44 ... frequency command value calculation unit 45 ... reference sine wave generation unit

Claims (4)

A synchronous control circuit that synchronizes the AC / DC converter connected to the AC power supply system at the same cycle as the system voltage,
Based on the d-axis component and the q-axis component of the system voltage, the phase difference between the system voltage and the reference sine wave phase is 0 ° to 90 °, 90 ° to 180 °, 180 ° to 270 °, 270 ° to 360 °. Is determined, and when the phase difference between the system voltage and the reference sine wave phase is 0 ° to 90, 270 ° to 360 °, the q-axis component of the system voltage is output, and the system voltage and the reference When the phase difference from the sine wave phase is 90 ° to 180 °, −1.0 [p. u. ] And when the phase difference between the system voltage and the reference sine wave phase is 180 ° to 270 °, 1.0 [p. u. A region determination circuit that outputs
The frequency at which the PI calculation is performed so that the output of the region determination circuit becomes 0, and the frequency command value of the reference sine wave is calculated by resetting the PI calculation result to zero when the PI calculation result reaches a preset value. A command value calculator,
A synchronization control circuit for an AC / DC converter, comprising: a reference sine wave generation unit that generates a reference sine wave based on the frequency command value. The frequency command value calculator is
2. The synchronous control circuit for an AC / DC converter according to claim 1 , wherein an upper limit value is set for the frequency command value, and the frequency command value is restricted from becoming higher than the upper limit value. 3. The synchronous control circuit for an AC / DC converter according to claim 1, wherein an effective value of the system voltage is calculated, and an output proportional to the effective value is weighted to an output of the area determination circuit. 4. The synchronous control circuit for an AC / DC converter according to claim 3 , wherein the weighting gain is set to 0 when the effective value of the system voltage is 5% or less.

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