JP2013085364A - Grid connection power conversion equipment control device and grid connection power conversion equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grid connection power conversion equipment control device which, while letting an output current continue, restricts generation of a resonance current at the time of a momentary voltage drop in the grid, and can thereby further improve the grid stability.SOLUTION: A phase retention unit 44 is included in a phase calculation unit 22 which calculates a current phase θαβ used in setting an output current value. In the phase retention unit 44, phase information at normal time before a voltage drop abnormality in the grid voltage is found is retained while being updated for m cycles (e.g., for one cycle). When setting of an output current value is made, if no voltage drop abnormality is found by operation of a phase value switching unit 43 and a voltage drop determination unit 47, etc., phase information output from a phase arithmetic unit 42 and extracted each time is output; if a voltage drop abnormality occurs, phase information held in the phase retention unit 44 is output.

Description

  The present invention relates to a control device for a grid interconnection power conversion device and a grid interconnection power conversion device.

  In recent years, a photovoltaic power generation system with a small environmental load has attracted more and more attention, and a new attempt has been made to simultaneously introduce a photovoltaic power generation system in several hundred towns. When many solar power generation systems are connected to the power system in such a relatively small area, various concerns arise.

  In a distributed power supply system such as a solar power generation system, a power conversion device, a so-called power conditioner (PCS, hereinafter simply referred to as a power conditioner) is installed between a power generation device such as a solar power generation panel and a power system. The power converter is equipped with an inverter that converts the generated power into AC power that matches the system frequency and its control device. In addition to the power conversion operation, the power converter can solve individual distributed power systems from the system when a power failure occurs in the system. It has become necessary to provide an isolated operation prevention function that causes a series connection and a continuous operation function during a low voltage (FRT function) that prevents unnecessary disconnection due to the previous function when the instantaneous voltage drops (instantaneous voltage drop). . This function is particularly effective in regions where the above-described photovoltaic power generation systems are introduced in a concentrated manner, because the effect of the entire photovoltaic power generation system in the entire region on the grid is great. This is also a necessary function.

  In addition, the power conditioner detects the fundamental voltage phase of the system voltage, and generates and injects AC power matched to the system based on the phase detection. If the AC power is output to the grid in the lost state, the grid and other power devices are adversely affected. Therefore, for example, as in the power conversion device (control device) disclosed in Patent Document 1, the fundamental wave voltage phase is detected from the system each time, and the fundamental wave voltage phase is detected at the time of the voltage drop abnormality including the instantaneous drop as described above. A technique for reducing the loss of this is considered.

Japanese Patent No. 3505626

  By the way, in the period until the voltage drop occurs in the power system and the fundamental voltage phase is lost on the power conditioner side, and the power conditioner recovers, The resonance current of the non-fundamental wave order is superimposed on the current on the system and is continuously generated in relation to the reactor, the capacitor, and the like provided in the power equipment connected to the system. In particular, when a large number of photovoltaic power generation systems are connected to the grid, the resonance current on the grid becomes large, which causes a stop due to a voltage drop in the load equipment of the customer, so-called load drop, etc. However, there is a concern that a large number of photovoltaic power generation systems will be disconnected from the grid all at once.

  Also, if a temporary operation stop function (gate block function) of several cycles is added before the disconnection, the output current during operation stop becomes zero, and the current soft start at the time of instantaneous voltage drop recovery after that Will be affected. In other words, when this function is used, there is a problem that the rise of the output current from the time when the voltage sag recovers becomes gradual, and the state before the voltage sag cannot be recovered quickly.

  The present invention has been made to solve the above-mentioned problems, and its object is to suppress the generation of a resonance current while continuing the output current at the time of a system sag and to further stabilize the system. An object of the present invention is to provide a control device for a grid interconnection power converter and a grid interconnection power converter.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a power converter that converts the generated power generated by the power generator into AC power that can be output to the power system. The control device for the grid interconnection power conversion device that performs appropriate control according to the current power status of the output power, and sets the output current amplitude of the power converter based on the power generation voltage of the power generation device Based on the setting means, the system voltage information extraction means for extracting the amplitude and phase information of the system voltage of the power system each time, the operation of the power converter based on the set output current amplitude and the extracted phase information. Output current value setting means for setting the output current value of the power converter to be controlled, abnormality determination means for determining a voltage drop abnormality based on the amplitude information of the system voltage, and until the voltage drop abnormality determination time Positive Phase information holding means for holding phase information at the time, and setting of the output current value in the output current value setting means, if the voltage drop abnormality has not occurred, apply the extracted phase information, The gist of the invention is that it comprises phase information switching means for switching to apply the held phase information in place of the extracted phase information when a voltage drop abnormality occurs.

  In the present invention, the phase information at the normal time until the voltage drop abnormality of the system voltage is determined is held. When the output current value is set by the output current value setting means, the phase information extracted every time when the voltage drop abnormality does not occur is applied, and when the voltage drop abnormality occurs, the previous information is retained. It is switched so that phase information is applied. In other words, when a voltage drop abnormality occurs, the output current value is set using the stable phase information at the normal time, so the operation of the power converter controlled by this control device is as stable as at the normal time. It will be a thing. As a result, the generation of a non-fundamental order resonance current in the output current from the power converter is reduced, which can contribute to further system stabilization.

  According to a second aspect of the present invention, in the control device for a grid interconnection power conversion device according to the first aspect, the phase information holding means has at least normal phase information until the determination of the voltage drop abnormality. The gist of the present invention is that the stored phase information is sequentially output to the output current value setting means when the voltage drop abnormality occurs after holding for one cycle.

  In the present invention, the normal phase information until the determination of the voltage drop abnormality can be held for at least one cycle, and when the voltage drop abnormality occurs, the held phase information is sequentially supplied to the output current value setting means. Is output. As a result, it is possible to easily output appropriate phase information when a voltage drop abnormality occurs without requiring computation.

  According to a third aspect of the present invention, in the control device for the grid interconnection power conversion device according to the first aspect, the phase information holding unit is configured to predetermine phase information at a normal time until the determination of the voltage drop abnormality. When the voltage drop abnormality occurs, the output current value setting means is sequentially output while calculating the phase information at that time based on the held predetermined phase information. This is the gist.

  In this invention, it is possible to hold a predetermined number of normal phase information until the determination of the voltage drop abnormality, and when the voltage drop abnormality occurs, the phase information at that time is calculated based on the held predetermined phase information. However, the calculated phase information is sequentially output to the output current value setting means. As a result, it is possible to easily output appropriate phase information when a voltage drop abnormality occurs, and to store less phase information.

  According to a fourth aspect of the present invention, in the control device for a grid interconnection power conversion device according to any one of the first to third aspects, the system voltage information extracting means includes amplitude and phase information of the system voltage. The gist of the present invention is that αβ conversion or instantaneous positive phase conversion by an αβ converter or instantaneous positive phase converter is used for extraction.

  In the present invention, αβ conversion or instantaneous positive phase conversion is used in extracting the system voltage amplitude and phase information. As a result, in any conversion, the output value after conversion changes instantaneously due to a voltage drop abnormality such as a momentary drop, so it is possible to more reliably determine a voltage drop abnormality including a momentary drop etc. It becomes.

  The invention according to claim 5 is the control device for the grid interconnection power conversion device according to any one of claims 1 to 4, wherein the phase information switching unit is configured to determine that the voltage drop abnormality is determined. When returning to a normal state, the gist is to switch the phase information output to the output current value setting means from the holding mode side to the extraction mode side by delaying the phase information by a delay unit for a predetermined time from the return time.

  In this invention, when returning to the normal state after the voltage drop abnormality is determined, the phase information output to the output current value setting means is switched from the holding mode side to the extraction mode side after a predetermined time delay from the return time. . As a result, there may be a transient change on the system at the time of recovery from the voltage drop abnormality, so that the transient change is prevented from being reflected in the phase information, and the output of the power converter is further stabilized. It can contribute to system stabilization.

  The invention according to claim 6 is a power converter that converts the generated power generated by the power generator into AC power that can be output to the power system, and the control according to any one of claims 1 to 5. It is the power converter device for grid connection provided with the apparatus.

  In the present invention, the use of the control device according to any one of claims 1 to 5 reduces the generation of a non-fundamental-order resonance current in the output current from the power converter. It can be provided as a system interconnection power conversion device that can contribute to system stabilization.

  According to the present invention, it is possible to suppress the generation of a resonance current while continuing the output current at the time of a system instantaneous drop, and to further improve the system stabilization. A system power conversion device can be provided.

The block diagram which shows the structure of the solar energy power generation system in one Embodiment. The block diagram which shows the detailed structure of the phase calculation part in the form. The wave form diagram which shows the change of the system | strain (interconnection point) voltage and electric current at the time of the instantaneous drop in the same form. The wave form diagram which shows the change of the system | strain (interconnection point) voltage and electric current at the time of the instantaneous drop in a comparative example. The block diagram which shows the phase calculation part in another example. The block diagram which shows the converter in another example. The block diagram which shows the converter in another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 shows a photovoltaic power generation system according to this embodiment. The solar power generation system 10 converts direct current power generated by the solar power generation panel PV into three-phase alternating current power of a system frequency (50 Hz or 60 Hz) by a power conditioner (power conditioner) 11 and uses the converted alternating current power for commercial use. This is output to the power system Ls. The power conditioner 11 employs a voltage type current control method.

  The power conditioner 11 includes an inverter 12 that is a DC-AC power converter and a control device 13 that controls the inverter 12. The inverter 12 is configured by a three-phase bridge circuit using a plurality of semiconductor switching elements (not shown). Direct current power from the photovoltaic power generation panel PV obtained by power generation is input to the inverter 12 via the charging capacitor 14. Based on switching control (PWM control) by the control device 13, the inverter 12 converts the input DC power into three-phase AC power corresponding to the situation of the power system Ls at that time, and the interconnection reactor 15 for each phase. Is output to the power system Ls.

  When the control device 13 controls the inverter 12, the control device 13 determines the three-phase system voltages Vsa, Vsb, Vsc and the system currents Isa, Isb, Isc at the subsequent stage of the connection reactor 15, that is, the connection points with the system Ls. Input at the sampling cycle. The system voltages Vsa, Vsb, Vsc and system currents Isa, Isb, Isc are converted into two-phase voltage values Vsα, Vsβ and two-phase in a fixed coordinate system of αβ axis by a three-phase / two-phase (3Φ / 2Φ) converter 21. They are converted into current values Isα and Isβ, respectively (αβ conversion).

  The phase calculation unit 22 receives the two-phase voltage values Vsα and Vsβ from the three-phase / two-phase conversion unit 21, calculates the voltage phase from these, and converts the calculated voltage phase into a current phase (phase adjustment). Thus, an appropriate current phase θαβ is calculated from time to time. The detailed configuration of the phase calculation unit 22 will be described later with reference to FIG. The phase calculation unit 22 outputs the calculated current phase θαβ to the output current value calculation unit 23. The output current value calculation unit 23 also receives the output current amplitude command value Ic from the command value switching unit 24 together with the current phase θαβ.

  The command value switching unit 24 has first and second input terminals a1 and a2. The output current amplitude command value from the DC voltage control unit 25 is input to the first input terminal a1. The DC voltage control unit 25 inputs the charging voltage Vdc of the charging capacitor 14 provided between the photovoltaic power generation panel PV and the inverter 12 as the power generation voltage of the power generation panel PV so that the charging voltage Vdc becomes a steady voltage. Is set to the output current amplitude command value at that time, and the set command value is output to the first input terminal a1.

  The output current amplitude command value held by the command value holding unit 26 is input to the second input terminal a2. When the command value holding unit 26 receives the output current amplitude command value from the DC voltage control unit 25 and is determined by the voltage drop determination unit 47 (described later) included in the phase calculation unit 22 to be at the time of voltage drop abnormality, The determination signal is input as a holding command signal, the output current amplitude command value acquired at that time is held, and the held command value is output to the second input terminal a2.

  In the voltage drop determination unit 47 (see FIG. 2), which will be described later, from the system voltages Vsa, Vsb, Vsc that are input as the two-phase voltage values Vsα, Vsβ, when the instantaneous voltage drops in the power system Ls (at the time of instantaneous drop) Whether or not a voltage drop abnormality of a predetermined level or more that includes

  Further, the determination signal determined as the voltage drop abnormality is input to the control terminal a0 of the command value switching unit 24 as a switching control signal. That is, at the normal time when the voltage drop abnormality is not determined (when the system is healthy), the command value switching unit 24 to which this is input as a switching control signal selects the first input terminal a1, and the DC voltage control unit 25 The current output current amplitude command value input via the first input terminal a1 is output to the output current value calculation unit 23 as the output current amplitude command value Ic of the command value switching unit 24.

  On the other hand, if it is determined that a voltage drop abnormality of a predetermined level or more including a voltage sag has occurred, the command value switching unit 24 to which this is input as a switching control signal selects the second input terminal a2. At the same time, a holding command signal based on the abnormality determination is input to the command value holding unit 26, and the output current amplitude command value from the DC voltage control unit 25 at that time is held in the command value holding unit 26. 2 is output to the input terminal a2. Therefore, in the command value switching unit 24, the output current amplitude command value held by the command value holding unit 26 input via the second input terminal a2 is used as the output current amplitude command value Ic of the command value switching unit 24. It is output to the value calculation unit 23.

  Based on the input output current amplitude command value Ic and the current phase θαβ, the output current value calculation unit 23 calculates an output current value having an appropriate amplitude and phase from time to time. The calculated output current values are input to the calculators 27a and 27b as the two-phase current values Icα and Icβ in the αβ axis fixed coordinate system, respectively.

  The calculator 27a calculates a deviation using the two-phase current value Icα from the output current value calculation unit 23 based on the command value and the two-phase current value Isα from the three-phase / two-phase conversion unit 21 based on the actual value. Then, the calculation result on the α-axis side is output to the voltage converter 28a. The calculator 27b calculates a deviation using the two-phase current value Icβ from the output current value calculation unit 23 based on the command value and the two-phase current value Isβ from the three-phase / two-phase conversion unit 21 based on the actual value. Then, the calculation result on the β-axis side is output to the voltage converter 28b.

  The voltage converter 28a converts the deviation current value between the current command value and the actual value, which is the calculation result of the calculator 27a, into a voltage value, and outputs the voltage value to the calculator 29a as the deviation voltage value on the α-axis side. The voltage converter 28b converts a deviation current value between the current command value and the actual value, which is a calculation result of the calculator 27b, into a voltage value, and outputs the voltage value to the calculator 29b as a deviation voltage value on the β-axis side.

  The computing unit 29a reflects the deviation voltage value from the voltage converter 28a in the two-phase voltage value Vsα from the three-phase / two-phase conversion unit 21, and the two-phase / three-phase ( 2Φ / 3Φ) to the converter 30. The computing unit 29b reflects the deviation voltage value from the voltage converter 28b in the two-phase voltage value Vsβ from the three-phase / two-phase conversion unit 21, and performs two-phase / three-phase conversion as the output voltage value Vcβ on the β-axis side. To the unit 30.

  The two-phase / three-phase converter 30 converts the two-phase output voltage values Vcα and Vcβ in the αβ axis fixed coordinate system into three-phase output voltage values Vca, Vcb, and Vcc. The converted three-phase output voltage values Vca, Vcb, Vcc are output to the PWM control unit 31.

  The PWM control unit 31 sets a control pulse used when the PWM control of the inverter 12 is performed, and an on-pulse width (duty) of the control pulse based on the input three-phase output voltage values Vca, Vcb, Vcc. Is determined to an appropriate value. And the PWM control part 31 is performing the suitable switching operation | movement of the inverter 12 based on the control pulse determined at that time.

Next, the detailed structure of the phase calculation unit 22 will be described with reference to FIG.
In the phase calculation unit 22, the two-phase voltage values Vsα and Vsβ from the three-phase / two-phase conversion unit 21 are input to the amplitude calculation unit 41 and the phase calculation unit 42 for each predetermined sampling period. The phase calculation unit 42 calculates the voltage phase based on the input two-phase voltage values Vsα and Vsβ, calculates the current phase θαβ at that time, such as converting the calculated voltage phase into a current phase, and switches the phase value The signal is output to the first input terminal b1 of the unit 43.

  The phase value switching unit 43 has first and second input terminals b1 and b2, and the current phase θαβ from the phase calculation unit 42 is input to the first input terminal b1. The current phase θαβ held by the phase holding unit 44 is input to the second input terminal b2.

  The phase holding unit 44 receives the current phase θαβ output from the phase value switching unit 43, and updates and holds the phase information for m cycles (in this embodiment, one cycle, that is, one cycle). For example, when the first input terminal b1 is selected in the phase value switching unit 43, the phase holding unit 44 sequentially updates and holds the phase information for the past m cycles of the current phase θαβ from the phase calculation unit 42. The Further, when the second input terminal b2 is selected in the phase value switching unit 43, phase information for the past m cycles of the current phase θαβ input from the first input terminal b1 before switching to the second input terminal b2. And is repeatedly updated with the same information from the connection mode of the phase value switching unit 43 and the phase holding unit 44.

  The amplitude calculation unit 41 calculates a voltage amplitude value | V | at that time, in this case, an absolute value based on the input two-phase voltage values Vsα and Vsβ, and calculates an amplitude change calculation unit 45 and a second determination described later. Output to each of the devices 48.

  The amplitude variation calculation unit 45 inputs the voltage amplitude value | V | calculated by the current sampling as it is to the computing unit 45a and also calculates the voltage amplitude value | V calculated by sampling one cycle before (one cycle before). | Is input, and the voltage amplitude change | ΔV | is calculated from the difference between the two values. The calculated voltage amplitude change | ΔV | is output to the first determiner 46.

  The first determination unit 46 compares the input voltage amplitude change | ΔV | with a preset reference value ΔVref. When the voltage amplitude change | ΔV | is smaller than the reference value ΔVref, an output signal is output. When the voltage amplitude change | ΔV | is greater than the reference value ΔVref, the output signal is switched to the H level. That is, the first determiner 46 uses the voltage amplitude change | ΔV | to determine whether or not a voltage drop abnormality including an instantaneous drop has occurred. An output signal from the first determination unit 46 is output to the voltage drop determination unit 47.

  The voltage drop determination unit 47 is configured by an RS flip-flop, and an output signal from the first determination unit 46 is input to the S terminal (set terminal). The output signal of the second determiner 48 is input to the R terminal (reset terminal) of the voltage drop determination unit 47 via the AND circuit (AND circuit) 49 and the on-delay timer 50.

  The second determiner 48 compares the input voltage amplitude value | V | with a preset reference value Vref. When the voltage amplitude value | V | is smaller than the reference value Vref, the second determiner 48 outputs an output signal L When the level and voltage amplitude value | V | becomes larger than the reference value Vref, the output signal is switched to the H level. In other words, the second determiner 48 uses the voltage amplitude value | V | to determine whether or not the voltage has returned to the normal voltage level after the occurrence of a voltage drop abnormality including an instantaneous drop. An output signal from the second determiner 48 is output to the AND circuit 49.

  The AND circuit 49 is a two-input type, and an output signal from the second determiner 48 is input to one input terminal, and an output signal from the voltage drop determination unit 47 is input to the other input terminal. The output signal of the AND circuit 49 is output to the R terminal of the voltage drop determination unit 47 via an on-delay timer 50 that delays signal transmission by a predetermined time Td. The voltage drop determination unit 47 changes the logic of the output signal output from the Q terminal based on the signal input to the R terminal and the previous S terminal, and the output signal is controlled by the phase value switching unit 43. It is output to the terminal b0.

  Here, the voltage drop determination unit 47 outputs an L level output signal from the Q terminal as an initial state. In response, the phase value switching unit 43 selects the first input terminal b1, and outputs the current phase θαβ output from the phase calculation unit 42 based on the two-phase voltage values Vsα and Vsβ at that time. It has become. That is, when the system voltages Vsa, Vsb, and Vsc are at normal voltage levels, the current phase θαβ is thus output from the phase value switching unit 43, that is, the phase calculation unit 22, and the output current value calculation unit 23 (see FIG. 1). ) Is used to set the output current value. In addition, the current phase θαβ output from the phase value switching unit 43 is held in the phase holding unit 44 while the past one cycle is updated.

  When a voltage drop abnormality such as an instantaneous drop occurs in the system voltages Vsa, Vsb, and Vsc and the voltage amplitude change | ΔV | becomes larger than the reference value ΔVref in the first determiner 46, the output of the first determiner 46 The signal is switched from the L level to the H level, and the S terminal of the voltage drop determination unit 47 becomes the H level. In response, the output signal output from the Q terminal of the voltage drop determination unit 47 is switched from the L level to the H level, and then the output signal output from the Q terminal is set to the H level until the R terminal becomes the H level. Maintained. Then, the phase value switching unit 43 switches from the first input terminal b1 to the second input terminal b2, and the current phase θαβ for one cycle held by the phase holding unit 44 is changed to the phase value switching unit 43 (phase calculation unit 22). Will be output sequentially.

  At this time, the current phase θαβ for one cycle held by the phase holding unit 44 is in a normal state (when the system is healthy) immediately before a voltage drop abnormality such as a voltage drop, so a voltage such as a voltage drop Even during the period in which the drop abnormality occurs, the output current value is set by the output current value calculation unit 23 (see FIG. 1) based on the stable normal current phase θαβ.

  Eventually, when the system voltage Vsa, Vsb, Vsc recovers from a voltage drop abnormality such as an instantaneous drop to a normal voltage level and the voltage amplitude value | V | becomes larger than the reference value Vref by the second determiner 48, the second determination is made. The output signal of the device 48 is switched from L level to H level. At this time, since the output signal from the Q terminal of the voltage drop determination unit 47 input to the AND circuit 49 is at the H level, the output signal of the second determination unit 48 is at the H level. 49 output signals are switched from L level to H level. Then, after the predetermined time Td has elapsed, the output signal of the on-delay timer 50 is switched from the L level to the H level, and the R terminal of the voltage drop determination unit 47 becomes the H level.

  In response to this, the output signal output from the Q terminal of the voltage drop determination unit 47 switches from H level to L level, and the phase value switching unit 43 switches from the second input terminal b2 to the first input terminal b1. The phase value switching unit 43 (phase calculation unit 22) outputs a current phase θαβ based on the two-phase voltage values Vsα and Vsβ at that time, and the output current value of the output current value calculation unit 23 (see FIG. 1) is output. Used for setting.

Next, the operation (action) of the power conditioner 11 under the control of the control device 13 configured as described above will be described with reference to FIGS. 1 and 2.
When the system voltages Vsa, Vsb, and Vsc are changing at the normal voltage level, the output current value in the output current value calculation unit 23 that determines the operation of the inverter 12 is calculated based on the charging voltage Vdc at that time. Output current amplitude command value and current phase θαβ calculated based on the system voltages Vsa, Vsb, Vsc (two-phase voltage values Vsα, Vsβ) at that time. By the inverter 12 that operates based on the output current value set in this manner, the DC power generated by the photovoltaic power generation panel PV is appropriately converted into AC power suitable for the power system Ls and output to the system Ls.

  When a voltage drop abnormality such as an instantaneous drop occurs in the system voltages Vsa, Vsb, and Vsc, the output current amplitude command value at the time when the abnormality is determined (when the Q terminal of the voltage drop determination unit 47 becomes H level) is While being held in the command value holding unit 26, the held output current amplitude command value is continuously output to the output current value calculating unit 23 in the abnormality determination period. In addition, since the normal current phase θαβ immediately before being determined to be abnormal is held for m cycles (one cycle) in the phase holding unit 44, the normal current phase θαβ continues in the abnormality determination period. Is output to the output current value calculator 23.

  Therefore, in the output current value calculation unit 23, the output current value is set using stable phase information when the system Ls is normal, so that the operation of the inverter 12 becomes stable in the same way as when the system Ls is normal. The generation of a non-fundamental order resonance current in the output current is reduced. Further, the use of the method of this embodiment is excellent in that the phase is not lost even if the system voltages Vsa, Vsb, and Vsc become zero.

  Here, FIG. 4 shows the system voltages Vsa, Vsb, Vsc and the system current Isa, at the connection point when a power conditioner having a specification for reducing the phase loss by detecting the fundamental wave voltage phase from the system is used. Although changes in Isb and Isc are shown, as shown in FIG. 4, when an instantaneous drop occurs in the system, a resonance current and a resonance voltage of a non-fundamental wave order are generated and continued. Especially when a large number of power conditioners of this specification are connected to the system, the resonance current and resonance voltage on the system become large, and the load drop of the customer is added, leading to an increase in the resonance phenomenon. There is a risk that power conditioners (solar power generation systems) will be disconnected all at once.

  On the other hand, FIG. 3 shows changes in the system voltages (connection point voltages) Vsa, Vsb, Vsc and the system currents (connection point currents) Isa, Isb, Isc based on the operation of the power conditioner 11 of the present embodiment. However, as shown in FIG. 3, even if an instantaneous drop occurs on the system Ls, the generation of the resonance current and the resonance voltage of the non-fundamental wave order is immediately suppressed. This is particularly effective when a large number of power conditioners 11 (solar power generation systems 10) are connected to the system Ls.

  Eventually, when the system voltages Vsa, Vsb, and Vsc return to the normal voltage level from the voltage drop abnormality such as a momentary drop, the current phase θαβ from the phase holding unit 44 is reached after a predetermined time Td has elapsed due to the operation of the on-delay timer 50. Is switched to the output of the current phase θαβ from the normal phase calculator 42. That is, there is a possibility that a transient change has occurred on the system Ls at the time of return, and the transient change is prevented from being reflected in the current phase θαβ. This contributes to the stabilization of the operation of the inverter 12 at the time of return. As shown in FIG. 3, the system voltages Vsa, Vsb, Vsc and the system currents Isa, Isb, This can contribute to suppression of distortion of Isc.

Next, characteristic effects of the present embodiment will be described.
(1) The phase holding unit 44 is provided in the phase calculating unit 22 that calculates the current phase θαβ used for setting the output current value, and the phase holding unit 44 has a voltage drop abnormality of the system voltages Vsa, Vsb, and Vsc. The normal phase information until the time is determined is held for m cycles (one cycle in this embodiment) while being updated. Then, when setting the output current value in the output current value calculation unit 23, in the operation of the phase value switching unit 43 and the voltage drop determination unit 47 of the phase calculation unit 22, when the voltage drop abnormality has not occurred, The extracted phase information is applied each time output from the phase calculation unit 42, and when voltage drop abnormality occurs, the phase information held in the previous phase holding unit 44 is applied. That is, when a voltage drop abnormality occurs, the output current value is set using the stable phase information at the normal time held by the phase holding unit 44, so that the operation of the inverter 12 is stabilized as in the normal time. It will be a thing. As a result, it is possible to reduce the occurrence of a non-fundamental-order resonance current in the output current from the inverter 12 (power conditioner 11), and to contribute to further stabilization of the system Ls.

  (2) A phase holding unit 44 capable of holding normal phase information for m cycles (1 cycle in this embodiment) until the determination of the voltage drop abnormality is provided, and held when a voltage drop abnormality occurs. The phase information for m cycles is sequentially output. As a result, it is possible to easily output appropriate phase information when a voltage drop abnormality has occurred without requiring computation.

  (3) A three-phase / two-phase converter 21 that performs αβ conversion is used when extracting the amplitude and phase information of the system voltages Vsa, Vsb, and Vsc. Thereby, since the output value after conversion changes instantaneously due to a voltage drop abnormality such as a voltage drop, it is possible to more reliably determine a voltage drop abnormality including a voltage drop. Moreover, if αβ conversion is used, accurate phase information can be obtained even if the system frequency changes.

  (4) When returning to the normal state after the voltage drop abnormality is determined, the phase information output to the output current value calculation unit 23 is retained after a delay of a predetermined time Td from the return by the operation of the on-delay timer 50. The mode is switched from the mode side to the extraction mode side. As a result, there may be a transient change on the system Ls at the time of recovery from the voltage drop abnormality, so that the transient change can be prevented from being reflected in the phase information, and the output of the inverter 12 can be stabilized. This can contribute to the stabilization of the system Ls.

In addition, you may change embodiment of this invention as follows.
In the above embodiment, the phase calculation unit 22 is configured as shown in FIG. For example, the configuration of the phase calculation unit 22A as shown in FIG. 5 may be used.

  The phase calculation unit 22A illustrated in FIG. 5 includes a phase storage unit 51, a phase counter 52, and a calculator 53 instead of the phase holding unit 44 that holds phase information for m cycles. The phase storage unit 51 receives the current phase θαβ output from the phase value switching unit 43, and updates and holds a predetermined number (for example, one) of phase information. Further, when the output signal from the voltage drop determination unit 47 is input to the phase storage unit 51 and the output signal indicating that the voltage drop abnormality determination has been made is input, the phase value switching unit 43 is connected to the second input terminal b2. For example, one normal current phase θαβ input from the first input terminal b1 immediately before switching is held, and updating thereof is prohibited during the period when the voltage drop abnormality determination is made. The phase counter 52 calculates a phase change amount considering the system frequency for each sampling. The computing unit 53 adds the phase change amount for each sampling to the normal current phase θαβ stored in the phase storage unit 51 so that normal phase information can be sequentially output. Even with this configuration, it is possible to easily output appropriate phase information when a voltage drop abnormality occurs. Also, less phase information is held in the phase storage unit 51.

  In the above embodiment, the three-phase / two-phase conversion unit 21 that performs αβ conversion to extract the amplitude and phase information of the system voltages Vsa, Vsb, and Vsc is used, but other converters may be used. For example, an instantaneous positive phase converter 21A as shown in FIG. 6 may be used.

The instantaneous positive phase converter 21A shown in FIG. 6 includes calculators 61a to 61d, delay units 62a to 62c, and rotation calculators 63a and 63b. The real part (Re) of the first phase system voltage Vsa is input to the calculator 61a, and the real part (Re) is calculated as an imaginary part (Im) via a delay part 62a that delays a quarter cycle. Is input to the device 61b. The second phase system voltage Vsb is input to the calculator 61c via the rotation calculator 63a whose real part (Re) performs the calculation a (= e ^{j2π / 3} ), and the real part (Re) is 1 / It is input to the computing unit 61d as an imaginary part (Im) through the delay unit 62b that performs a 4-cycle delay and the rotation computing unit 63a. The third phase system voltage Vsc has its real part (Re) is input to the arithmetic unit 61c via the rotary operation unit 63b to perform an operation ^{a 2,} the real part (Re) performs 1/4 cycle delay delay The imaginary part (Im) is input to the computing unit 61d through the unit 62c and the rotation computing unit 63b. The calculation results of the calculators 61c and 61d are input to the calculators 61a and 61b, respectively. Then, the calculator 61a outputs the first voltage value Vs1 as the calculation result on the real part side, and the calculator 61b outputs the second voltage value Vs2 as the calculation result on the imaginary part side, respectively. Extraction of amplitude and phase information is performed from the first voltage value Vs1 including information and the second voltage value Vs2 including phase information. Even if such an instantaneous positive phase converter 21A is used, since the first voltage value Vs1 including amplitude information changes instantaneously due to a voltage drop abnormality such as a sag, a voltage drop abnormality including a sag is determined. This can be done more reliably.

  In addition, the previous instantaneous positive phase converter 21A has first and second voltage values Vs1 for extracting amplitude and phase information of the three-phase voltages Vsa, Vsb, and Vsc so as to correspond to the three-phase system Ls. , Vs2, but may be applied to a single-phase system using the instantaneous positive phase converter 21B shown in FIG. The instantaneous positive phase converter 21B includes only the delay unit 62a, and the real part (Re) of the single-phase voltage Vs is set as the first voltage value Vs1, and the imaginary part (Im via the delay unit 62a that performs a 1/4 cycle delay). ) Is output to the phase calculation unit 22 as the second voltage value Vs2, and the amplitude and phase information is extracted from the first and second voltage values Vs1 and Vs2. In accordance with this, the power converter 11 can be applied to a single-phase system by changing the configuration such as changing the inverter 12 to a single-phase inverter.

-You may change suitably the holding | maintenance aspects of phase information, such as the number of holding | maintaining phase information of the said embodiment, and the timing of holding | maintenance.
The retention mode of the output current amplitude command value, such as the number of output current amplitude command values to be retained and the retention timing, may be changed as appropriate.

-In above-mentioned embodiment, although the inverter 12 was provided as a power converter, you may substitute with another power converter and may combine with another power converter.
In the above-described embodiment, the present invention is applied to the power conditioner 11 of the solar power generation system 10, but may be applied to other power conditioners such as a wind power generation system and a cogeneration system.

11 Power conditioner (Power converter, power converter for grid connection)
12 Inverter (Power converter)
13 Controller 21 Three-phase / two-phase converter (system voltage information extraction means, αβ converter)
21A, 21B Instantaneous positive phase converter 23 Output current value calculation unit (output current value setting means)
24 Command value switching unit (output current amplitude setting means)
25 DC voltage controller (output current amplitude setting means)
26 Command value holding unit (output current amplitude setting means)
41 Amplitude calculation section (system voltage information extraction means)
42 Phase calculation section (system voltage information extraction means)
43 Phase value switching unit (phase information switching means)
44 Phase holding unit (phase information holding means)
46 1st determination device (abnormality determination means)
47 Voltage drop determination unit (abnormality determination means, phase information switching means)
50 On-delay timer (delay means)
51 Phase storage unit (phase information holding means)
PV solar power generation panel (power generation equipment)
Ls Power system Vdc Charging voltage (power generation voltage)
Vsa, Vsb, Vsc System voltage Ic Output current amplitude command value (output current amplitude, amplitude information)
θαβ Current phase (phase information)
Td predetermined time

Claims (6)

For grid connection that implements appropriate control of the power status of the power system for the power converter that converts the generated power generated by the power generator into AC power that can be output to the power system. A control device for a power converter,
Output current amplitude setting means for setting the output current amplitude of the power converter based on the generated voltage of the power generation device;
System voltage information extraction means for extracting the amplitude and phase information of the system voltage of the power system each time;
Based on the set output current amplitude and the extracted phase information, output current value setting means for setting the output current value of the power converter to control the operation of the power converter;
An abnormality determination means for determining a voltage drop abnormality based on the amplitude information of the system voltage;
Phase information holding means for holding normal phase information until the determination of the voltage drop abnormality;
When the output current value is set by the output current value setting means, the extracted phase information is applied when the voltage drop abnormality does not occur, and the extracted phase when the voltage drop abnormality occurs. A control apparatus for a grid-connected power converter, comprising: phase information switching means for switching to apply the held phase information instead of information. In the control apparatus of the grid connection power converter device according to claim 1,
The phase information holding means holds at least one cycle of normal phase information until the determination of the voltage drop abnormality, and when the voltage drop abnormality occurs, the held phase information is set to the output current value setting. A control device for a grid interconnection power converter, wherein the controller is configured to sequentially output to the means. In the control apparatus of the grid connection power converter device according to claim 1,
The phase information holding means holds a predetermined number of normal phase information until the determination of the voltage drop abnormality, and when the voltage drop abnormality occurs, the phase information holding means based on the held predetermined phase information at that time A control device for a grid interconnection power converter, wherein the controller is configured to sequentially output to the output current value setting means while calculating phase information. In the control apparatus of the grid connection power converter device according to any one of claims 1 to 3,
The grid voltage information extracting means uses αβ conversion or instantaneous positive phase conversion by an αβ converter or instantaneous positive phase converter when extracting the amplitude and phase information of the system voltage. Control device for the conversion device. In the control apparatus of the grid connection power converter device according to any one of claims 1 to 4,
The phase information switching means holds the phase information output to the output current value setting means delayed by a delay means for a predetermined time from the return time when returning to the normal state after the voltage drop abnormality is determined. The control apparatus of the power converter for grid connection characterized by switching from the aspect side to the extraction aspect side.   A power converter that converts the generated power generated by the power generation device into AC power that can be output to the power system, and the control device according to any one of claims 1 to 5, Power conversion device for grid connection.